A Tale of Two RX7's and Scope Creep: My 6+ Year Build

In reply to Don49 (Forum Supporter) :

Mine is still in the stock, angled configuration. I've thought about making some brackets to make it more upright, but that would resuly in a cascade of other changes I don't want to mess with for the moment. I'm trying to get one more event in this year. VIR is likely out of the question due to schedule conflicts but there is another event at Dominion in November. I'm currently waitlisted but if I get in it'll be a good test of how lower ambient temperatures affect my temperatures.

Right now I think the biggest issue is the inlet and exit of my oil cooler duct. The inlets are sized to be 20-25% of the heat exchanger area, which seems to be the recommended area. However, looking at the front of the car I can see where the oil cooler area inlet area is actually smaller with everything installed.

I'm wondering if I'm getting some boundary layer effects from the split and the bumper cover that's reducing flow to the oil cooler. It's also possible the split is deflecting at speed, reducing area even more. This Winter I plan on raising the split a little more and adding a stiffening rib across the front or a vertical strut. I may even cut out a small area of the bumper cover. Someone suggested cutting out the bar between the frame rails to increase flow to the radiator but I'm not sold on that. I can leave the ends in place so I don't lose the oil cooler mounting points but I don't know what losing that bar will do to chassis rigidity.

The other thing I'm going to address is the area behind the oil cooler. In this picture of the duct out of the car you can see the exit from the oil cooler is open to the inlet of the radiator.

As you can see the split ends at the oil cooler. I'm thinking the slightly higher pressure in front of the radiator is reducing flow through the oil cooler. My solution is to extend the split all the way to the radiator. This does mean that heated air from the oil cooler will then be passing through the radiator. The only way to avoid this would be to cut out the bottom of the duct and force the heated air from the oil cooler out through the bottom. However, I've read that ducting out the bottom of the car can increase front end life, which is definitely something I don't want.

In reply to Don49 (Forum Supporter) :

Also wanted to respond to your shifting comments. I'm nearly certain your correct. The shifter springs are all less than 2 years old so no issue there. On my last run of the day I had a REALLY hard time getting it into the correct gear. Wouldn't go into 3rd so I tried to just bypass it and go into 4th and I kept ending up back in 2nd. I'm definitely holding the lever to the left slightly. It's a short-throw shifter with a 4" extension to it doesn't take a lot of movement to move between the gates. I need to work on methodically moving the lever out of 2nd, letting it center itself, then moving it up into 3rd. It's definitely a stress/fatigue problem. I had no issues in the clip I posted, which was from an earlier run in the day, but I got progressively worse as the day went on.

Four months since my last update. Unfortunately, the reason for this is little has happened. I ran my last track day in September and with no events in the near future there wasn't much motivation to work on the car. I briefly switched my attention to my 1st gen but got quickly burned out by a stupid brake issue that ended up taking the better part of 3 weeks to figure out. So other than driving the car once every 2 weeks there wasn't much going on until this past weekend.

What happened this past weekend? As a late Christmas/birthday present to myself I scheduled some dyno tuning time with a shop who knows what they're doing. Though the car has been running for 3+ years I'd say the tune was only 80% or so. I've been running safe timing and while the low/medium load/RPM areas of the fuel map are pretty dialed in I knew the higher load/RPM areas were conservative. I was too oblivious to take any pictures/video of the car during the session so this is all I have at the moment:

I went to a pretty well-known shop in VA and there was plenty of footage taken. I'm told there will be some YouTube content in the near future. After 2 hours of WOT pulls we went from this:

to this:

This was my first time on a Mustang dyno and I admit I don't understand all the numbers. The curves show I started at 233 hp and 160 ft-lb and ended with 251 hp and 168 ft-lb. However, the "power curve test results" say I started with 241 hp and 163 ft-lb with "WCF" (weather correction factor?) and ended with 262 hp and 170 ft-lb with WCF. It looks like Mustang dynos make a lot of assumptions about the vehicle and one thing I did notice is that my car's entered weight was 3250 lb when it's really 2500 lb with driver. I don't know how that affects the results. Regardless, both sets of numbers show a max increase of ~20 hp and ~8 ft-lb with improvement everywhere. The delta is all we care about, right? So far I've only just driven the car back from the shop so I haven't had the chance to really test if the difference is noticeable. So what did I learn from all this?

-I was leaving a lot on the table with conservative fuel and timing. We leaned out the fuel map, advanced total timing and increased the split between leading and trailing ignition timing.

-I'm running out of fuel. Adding fuel above 8000 RPM wasn't reducing the air-fuel ratio so I must be maxing out the duty cycle. I'm running 2 ID1000s with 45 psi of fuel pressure. Messing with a few online calculators tells me 2x 1000 cc/min injectors is enough fuel for ~320 hp. Assuming 20% drivetrain losses means my 250 hp at the wheels is ~313 hp at the crank. Seems plausible and I have options. I can increase fuel pressure and run 50+ psi. ID's data suggests just going from 45 to 50 psi will give me another ~100 cc/min of fuel. I could swap to 2x ID1300s I've had sitting around in the garage. +600 cc/min is a massive bump in fuel so I'd drop the pressure to 40 psi. Both provide the extra fuel I need at high RPM but both will have issues with low duty cycles at idle. My idle duty cycle is already in the 3.5-4% range. The only way around this is to go to a staged setup with smaller primary and larger secondary injectors. I've been avoiding this complexity but maybe it's time to give in. A benefit is placing the primaries closer to the intake ports would improve idle stability and low RPM transient response.

-I still have restriction somewhere. It starts to pull slight vacuum at WOT at higher RPM. This tells me I either can't get air in or exhaust out fast enough. This is not new. This has persisted despite the new exhaust and intake setups. The guys at the shop think my throttle bodies are undersized at 2x 50 mm but I had this same problem with my old 2x 55 mm setup. I think it's more likely the runners in the intake manifold or in the ports on the engine are the cause. Not much I can do about this.

-I confirmed my air box isn't hurting power. We did two back-to-back runs early on with and without it and the results said I actually lost a little power without the air box. 

-The starting numbers were pretty close to my last results from Summer 2019 when the car put down 241 hp and 160 ft-lb on a dynojet. This makes me pretty confident my car is putting down ~250 hp to the wheels, which is damn good for a street ported, naturally-aspirated 13B. This puts my weight-to-power ratio around 10 lb to 1 hp with driver.

1+ month bump. Here's the official video from the last dyno session. Ignore me and focus on the car...

I took a break from the car for most of February. We had an unusually cold period here so I didn't spend much, if any, time in the garage or driving the car. Lately we've had some ~60F days so I've been driving it a few times, working on the part throttle fuel map. I'd say the tune is 95% there. Where the fuel table isn't 100% closed loop control can handle and I'm working on refining that and transient throttle. It's a little tricky finding the optimum control settings for an engine with ITBs and big ports.

I've already committed to two track nights. I'll be back at Dominion in April and May will be my first time driving at VIR. Can't wait, but that means it's time to get to work. In addition to continue sorting out the tune I need to do the usual maintenance (fluids, check bolts, bearings, alignment, etc.) and I'll be making some tweaks to my radiator/oil cooler ducting. I've also determined I'm not as hardcore as I thought I was - I'll be replacing the delrin engine and transmission mounts with some polyurethane ones. They're still 95 durometer but hopefully the car won't be rattling my fillings out over 8000 RPM anymore.

I saw this on the Angel Motorsports channel and was excited to see this car. Great numbers with the Mochi tune. ;)

Well, track season prep is underway. Ordered all new fluids and filters and it looks like I'll have everything by next weekend. That gives me about 2.5 weeks to get everything ready for the first track day of the year. Last week I tinkered with the suspension. Back in January I ordered a new set of AWR rear camber links. Around this time last year I decided to ditch my original AWR camber links and try a different product. While I like the design of the other camber links they're lack of adjustability was a big downside.

"Old" links:

Note the awesome spherical bearing design to avoid binding. Here are the "new" links:

I like that they are adjustable but wish there were some way to incorporate spherical bearings. The grease fittings are a nice touch though. I've also come to the realization I really don't want solid engine and transmission mounts. Even with the rotary NVH become an issue over 8000 RPM. I didn't want to go as soft as factory or even the Mazda competition (40% stiffer than factory) mounts so I found some aftermarket polyurethane ones. RX7 engine mounts are little more than hockey pucks so they're pretty easy to make. However, since I was already ordering the camber links from AWR I figured I'd give their engine mounts a go.

They're a two-piece design, which I figure will make getting the engine out and in a little easier in the future. The only downside is the passenger's side mount (the bigger one) isn't designed to be used with oil pan braces so I had to cut a section out. It's not pretty but I'll deal with it the next time I have the oil pan off.

Other than that I did a quick string alignment since I decided to raise the car up about a 1/4 in. I was starting to notice some bump steer and the rear was nearly at the end of its toe and camber adjustment range. I'll be getting the car professionally aligned after my first event in April at Dominion Raceway. Why after? In what is probably the second largest single purchase on this car I splurged on some Fortune Auto 510 coilovers with all the bells and whistles. Custom springs rates and damper valving, aluminum strut bodies, inverted front struts, Swift springs, etc. I figure these will be the lifetime coilovers from now on. My old Stance GR coilovers have worked well in the nearly 11 years I've had them but it's time to move one. Unfortunately, the custom nature means the FAs won't arrive until after my first event around the end of April. The goal is to get them installed and the car professionally aligned before my event at VIR in May.

Two week update. Been slowly chipping away at the checklist for my first track day, which is rapidly approaching. Finally got my new SA2020 helmet in last week after a 3 month wait (backordered). Hopefully this one will get more use than my previous helmet. Also decided to pull the trigger on a Garmin Catalyst since they were doing a $100 rebate for the month of March. Really waffled back and forth between it and a more DIY approach with a phone app (e.g. RaceChrono) but ultimately chose the Garmin on the promise they're adding overlays to the video output. Car-wise it's mainly been usual maintenance. New engine oil, transmission and differential oil. Last weekend I replaced the coolant. This year I'm going to try a 75/25 distilled water/anti-freeze ratio. We don't generally see 0F temperatures here in Central VA so I'm thinking I won't have to change it for the Winter months. While I was in there I also replaced the thermostat and gasket. Not sure why I took a picture of this. Maybe to illustrate the proper OEM thermostat and gasket because it was a pain to get the right parts even from "respected" dealers.

I always found it strange the FSM specifies the thermostat be oriented this way. Conventional wisdom is the jiggle pin should be at the highest point. It's also hard to see but the proper OEM gasket has a small cutout on the ID that is supposed to be aligned with th jiggle pin. Oddly, the gasket included with the thermostat did not include this so I had to buy the proper gasket separately. I don't know what, if any, difference this makes. I also took the opportunity to make one change I mentioned previously. Last year I was seeing oil temperatures above 220F at the hotter track days. While not catastrophic I think they should be lower considering the ducting I have on the car. One thought was that because my split ends at the oil cooler I had created a high(er) pressure area in front of the radiator but behind the oil cooler, which was hurting flow. Here's a shot from the back with the radiator removed:

The duct is split at the inlet with about a 33/67% area split going to the oil cooler/radiator. As you can see the split ends at the oil cooler. I'm concern air directed at the radiator "spills over" behind the oil cooler, increasing the exit pressure slightly, which reduces flow. In an attempt to correct this I added another piece that extends the split all the way to the radiator.

You can also see some of the extra bracing I added last year at the front in case the split was deflecting downward at speed. I'll try this setup this year. I have some other ideas for 2022 if oil temperatures aren't improved. Anyway, got everything bolted back in, filled with coolant and burped the system. It's funny how I always seem to take out more coolant than I put back in. I'm confident in my ability to bleed the system but I'll keep an eye on the level in the overflow bottle. I did notice my coolant temperatures being a little higher than they were before. It now stabilized around 183-186F where before is was 179-182F. I think this is probably just variation due to the new thermostat, though.

All that's left is to flush and bleed the brakes. I have new fuel filters but the current ones are only 2 years old. Time permitting, I'll replace them, but I don't think they're critical. I'm also debating wrapping the exhaust again. The last time I tried I did an "okay" job and in the process of removing/reinstalling the exhaust several times it kind of fell apart so I ripped it off. If I decide to go this route it won't be for a while because I have some exhaust changes planned:

That's another Burns Stainless race muffler (4.5" OD, 12" long) and repacking material for my exhaust muffler (6.25" OD, 17" long). The plan is to add the new muffler upstream and inline with the existing one. Because of my long primary system I don't have a lot of space for mufflers so this is pretty much my only option. I'm also going to have the exhaust tip turned down. I don't know if my current muffler needs repacking but I figured it wouldn't hurt to have the materials to do so. Looking at the materials I now know why these mufflers are so light but also have so-so sound suppression. If this doesn't get the noise where I want/need it to be there are some other options. I see some other companies offer SS wool mat I could use in place of the "scrubble" and there's ceramic fiber mat that offers better heat resistance than traditional fiberglass. These are heavier options but probably do better at noise suppression and holding up to the heat of rotary engine exhaust.

The only thing bothering me with the car right now is stuttering/jerking/popping under deceleration. It only does this while decelerating (0 throttle position) from 4000-3000 RPM. Above 4000 RPM and below 3000 RPM it's smooth and I can transition back onto throttle with no issues. For some reason it has issues from 4000-3000 RPM and rolling back onto the throttle is usually rewarded with some amount of hesitation. You can hear in the track video I posted last year. It sounds/feels like the car is running lean but the air-fuel ratios don't agree with this. I've tried just about everything to solve this: add/pull fuel, advance/retard timing and add/reduce timing split (a rotary thing). None of these have had any noticeable effect. I've logged ECU data while decelerating from 9000 RPM all the way down to 2000 RPM. There aren't any weird jumps in timing. Oddly, AFRs are initially rich (no doubt from slamming the throttle shut) but they creep lean (think 16:1) around 5000 RPM. However, during this time I can still roll back on the throttle without issue. By the time it hits 4000 RPM the AFRs have stabilized at my target (be it 14.7:1, 13.5:1, etc.) and the car starts jerking and any throttle input is initially rewarded with hesitation. The only weird thing I see in the logs is the engine loses vacuum in the 4000-3000 RPM range. It's usually -13 to -12 psi but at 4000 RPM it increases to around -11.5 psi. Below 3000 RPM it drops back to -12 psi. My initial thought was not enough ignition advance but that didn't seem to make any noticeable change.

When decelerating, why would you have anything except extreme lean condition?

In other words, why is there any fuel at all being injected at closed throttle?

I would think this could be contributing.

In reply to wvumtnbkr :

I forgot to mention that. Since this is a rotary and I don't have the factory oil injection pump I'm forced to premix two stroke oil with my fuel. I don't have decel fuel cut (what Haltech calls it) activated because I'm paranoid about not getting enough lubrication to the seals while decelerating. It's something I've considered messing with though. I wish my ECU, an older Platinum Sport 1000, had a few more options like a vehicle speed setting so it only cuts when speed is above a certain threshold (i.e. so it doesn't cut fuel while revving in neutral). The newer Elite models have this. I may give it a shot and see how it works. I just find it interesting the bucking only occurs between 4000 and 3000 RPM. Now that you mention it, it does feel similar to when injection resumes when decelerating to near idle speeds on any other car.

Even the omp on stock rotaries are controlled with the throttle position.  

Maybe Pete can speak up about that part.

I am sure there are people running carbs and premix.  There has to be some knowledge on that.

The point you made that you had lower afr in that range made me think that it IS related.

In reply to wvumtnbkr :

Yeah, I still haven't gotten around to messing with it. The OMP is controlled by throttle position (mechanical or electronic) but I haven't dug into the stock systems enough to understand if they ever completely shut off or not. The issue with AFR is I can have it set at 14.7:1, 13.5:1 or whatever from 5000 RPM to 2000 RPM and it'll only buck from 4000 to 3000 RPM. Everywhere else it's fine despite having the same AFR. Decel fuel cut is probably the way to go but it'll have to wait a bit longer as I'm getting into track season and this isn't something I want to mess with at the track.

Speaking of track I spent some time last night installing the Garmin Catalyst.

The unit itself, the camera and the main power cable can all easily be removed for storage but I spent a little extra time routing the camera cable so it's hidden out of view. While not on track there will just be two little USB ends discreetly sticking out from the headliner and dash. I'm considering moving the unit down since it is kind of large. Tomorrow will be my first test with it and I don't know if it necessarily needs to be right in my sight line since I'll be using the audio queues/aids. It may be better off down where the radio used to be and just angling it upward.

Spent yesterday afternoon at Dominion Raceway for my first TNia this year. Other than one boneheaded move that earned me a brief black flag there were no issues. The weather was perfect - partly cloudy with ambient temperatures in the mid-60s F. At full tilt on track I don't think my water temperature ever exceeded 195F. Oil temperatures still went above 200F but no where near the 220+ I was seeing late last year. ~30F cooler ambient temperatures are probably the reason for this. I don't think IATs got much above 80F. So yeah, great weather for a track day. Here's the video from what I consider to be the best session:

I got the play with the Catalyst a bit. With the latest firmware update it now includes overlays with the video export. Here's my best lap of the day (lap 5 from the video above):

Overall I'm pleased with the Catalyst. The video quality is okay. It seems about the same as my ancient GoPro Hero2 from the first video. I'm not quite a complete novice so most of the advice is kind of "duh" stuff to me but it's good to have someone (thing?) in your ear constantly ramming home the fact that you blew that last corner. Speaking of, I need to come up with an audio solution. Because the car is so loud the onboard speaker is useless. I ended up using some Bluetooth earbuds, which proved difficult to keep in my ears while putting my helmet on, but worked okay. I didn't have the "advanced race coach" turned on so I was only getting feedback when I did something better. I'm going to try to find some smaller form factor earbuds for VIR in a month.

Not really much planned for the future. Hopefully my FA 510s come in later this month and I'll have them swapped in for VIR in May. I'll probably be back at Dominion in June and am thinking about a Friday at the Track (FATT) at Summit Point in July. I'm told Summit Point is pretty strict about their 103 dB sound limit so I'm hoping I can have my exhaust work done by then.

Another month, another TNiA. This time I got to check off a bucket list item by running at VIR. I've been to the track multiple times before but I've never actually driven on it. Ambient temperatures were higher than at the Dominion event reaching the upper 80s F during the first runs. In my first session out I was seeing oil temperatures over 220F again so it would seem my off-season modifications haven't done anything. 220-225F seems to be the maximum since I saw those same numbers on a nearly 100F day last year. The good news is as the temperature went down in the last afternoon I never saw 220+ again. Most importantly everything still seems to be working properly with the car. I did check the catch can the next day and got 95 mL of blow by oil out of it.

Not sure if this is normal or not. Oil level was about 3/4 between "low" and "full" on the dip stick and I know it was full before the event. I've since tossed ~100 mL back in. As for the event itself my first run proved to be a little problematic. A combination of nerves and over-driving the car resulted in two spins with the second one resulting in a pretty decent off-track excursion. I made the mistake of lifting off throttle too quickly going into Turn 8 in the uphill esses. Don't do that. All I can say is I'm thankful for VIR's massive runoff and I came closer to a tire wall than I ever want to be again. After that I decided to cut the first session short to collect myself and check over the car. I'm very fortunate to have come away with no damage whatsoever. I drove the second session MUCH more conservatively. Lots of point-bys and slow overall but I needed to rebuild confidence. I made some good progress and was getting progressively faster but I never really got a full clean lap due to traffic and point-bys. I felt pretty good going into the third session and started to push the car again. I ended up with one clean lap and ticked off a 2:34.22. Here's the Catalyst video (my GoPro died about 5 min into the session because I forgot to turn it off after the first two).

There's definitely room for improvement. My lines aren't great. I need to work on braking and turning in later, hitting the apexes and using more of the track. I think I'm getting better but this is only my 4th track day since getting back into it last Summer. I'll be back at Dominion in June so that will be a good test to see if I'm progressing since I'll have previous data to compare to.

Speaking of, I'm hoping to get a few things done before then. A couple posts back I mentioned trying to quiet the car down some. Next week I'm going to call my fabricator and see if he can fit the car in before the 17th to work out the new exhaust. Also, something I ordered 10 weeks ago finally came in:

Excluding the bodywork these are the single most expensive purchase I've made for this car. While there's technically nothing wrong with my current suspension the coilovers are 11 years old and are starting to look a little worse for wear. Rather than rebuild the entry-level coilovers I went with a step up:

It's an interesting color combination that's for sure. They're Fortune Auto 510 series coilovers with Swift springs, aluminum rear shock bodies with upper and lower spherical bearings and inverted front shocks. Compared to my current setup they're lighter, have less compliance, offer more adjustability and have the ability to be upgraded to 2- and 3-way adjustable if I decided to go that route. Can't wait to get these on and dialed in.

Small updated. Not really much happened since the last. Got the FA coilovers installed. They sure looked pretty for a bit:

Installation was a little more annoying than planned. Nothing too crazy but the FAs don't have as much camber adjustment in the strut mounts as my old Stances. In order to get the amount of camber I wanted I had to install those eccentric camber bolts in the lower holes (upper is slotted). In the off-season I'm thinking I'll either have these machined for more adjustment or just get some new camber plates made through one of those online machine shops. Looks like the camber plates could be slotted a further 1/4" or so:

The rears were also a bit of a pain just because of how the lower mounting point is setup. My FAs have a spherical bearing lower mount instead of rubber so they came with an assortment of spacers. No combination proved ideal: either too much spacing and the bearing was only partially engaged with the stud on the rear control arm or too little spacing and the shock body hit the control arm. Too much:

Too little:

I made due by reducing the thickness of a couple of the provided spacers until there was about a half mm of space between the shock body and the control arm. I think the best solution would be to replace the entire stud with a bolt and spacers but I need something like a 29 mm deep well socket to get that off and I don't know the thread diameter or pitch (spherical bearing ID is ~20 mm). Again, something to play with next Winter. In the meantime I've been religiously checking the torque on the lower bolt.

Last Thursday (06/17/2021) was another TNiA at Dominion Raceway. Once again I couldn't have asked for better weather. Sunny with highs in the low/mid-80s Fahrenheit. Oil temperatures still hit ~220F, which is enough to trigger a warning, but doesn't appear to be enough to cause any damage. Oil pressures were solidly in the 75-80 psi range with peak engine speeds around 8500 RPM. At first the car felt a little unsettled. I had set the rebound damping to FAs recommendation for "street comfort." I think this just led to too much body roll, which made quick transitions a little hairy. I increased the damping by a couple clicks on all four corners and that seemed to help a lot. Here's the Garmin Catalyst export of my best lap.

A <1 sec improvement since April. I'm carrying more speed through and out of the corners, which resulted in higher speeds in the straights, and I'm braking later but I'm still slowing down too much going into the turns and apexing too early. Later in the day I started playing with braking later and later but that mainly just resulted in me being harder on the brakes. During the last session I went off in Turn 2. Locked up all four wheels and went straight into the gravel. Combination of braking too late, too hard and losing sight of the line in the sun.

I did notice after the second run the car started to feel weird again. Upon closer inspection it looked like I had lost some negative camber on the FR and gained it in the RR. The next day I confirmed this with a camber gage. I quickly figured out what happened up front. The upper bolt hole in the lower strut mount for the fronts is slotted to allow for some additional camber adjustment. That had managed to slip, which caused the hub to rotate and lose negative camber. I did whack some curbing in the esses (~80 mi/hr) so I'm wondering if that was enough to cause the bolt to slide. Hopefully it's not just a result of vehicle loading and sticky tires. Dominion is run counter-clockwise so the right side is more heavily loaded. I think I'll make some inserts to go in the slots to prevent the bolts from moving in the future. I couldn't find any explanation for the excess negative camber in the rear. Nothing appears bent, broken or loose and there aren't any slotted holes for bolts to slip in. I did notice my camber adjusters, which are small threaded links located at the front of the rear control arms, were significantly different side-to-side. Even though the alignment shop print out shows both sides as being the same I'm wondering if there was some kind of error. I've got everything back to my specs now but need to take the car on some spirited drives to see if anything changes again.

My next track day is with AutoInterests at Summit Point Main. It'll be my first time at that track and first time with an instructor in car since 2011. I'm hoping to get some exhaust work done before then so I stand a chance of being able to hear them while driving. After that the only event I'm signed up for is a full weekend HPDE at Hyperfest at VIR. I'm thinking I'm going to do at least one more TNiA at Dominion in either August or September. Biggest issue there is both are within two weeks of either the Summit Point or VIR events.

Small update. I decided to look into my dynamic camber issue in the front some more. After the last track day I noticed the hub had slipped on the FR resulting in increased positive camber. I think I may have found the root cause. When torquing the upper bolt to spec I noticed my wrench was hitting the brake caliper. This added resistance making me think the bolt was torqued but it probably wasn't completely tight. Regardless, I set about a solution that would ensure this joint wouldn't slip in the future. Another thing I noticed as soon as started disassembling the strut was I wasn't using the entirety of the slotted hole. Only about half, in fact:

Turns out there is a cast ridge on the hub that prevents it from being rotated too far. Here's what it looks like with the hub pulled away from the strut:

Easy solution - grind away the offending ridge. Much better:

With that taken care of I could now utilize the entire width of the slotted hole. Now to ensure the bolt won't slip in the future. I spent entirely too long making four of the little crescent shaped inserts:

They measure about 12.5 mm tall and are about 6.5 mm thickn and fit into the slot like so:

With one spacer on each side of the lower strut mount they make sure the hub stays put. The other good news is it with using the full length of the slot I don't have to rely on eccentric bolts in the lower hole of the strut mount. With the factory 12 mm bolts reinstalled in the lower holes I have over -3 degrees of static camber with the wheels in the air. Since my target is -2.5 with the car on the ground I should have plenty of range of adjustability using the upper strut mounts. Now I have put the car back on the ground and align it (again).

So somehow I missed that VIR was hosting another TNiA on August 20th. Yeah, not going to pass up that opportunity. So now I have Summit Point (Main) on 8/2, VIR on 8/20 and HPDE at Hyperfest at VIR 10/2-3. Thinking about trying to cram one more TNiA at Dominion on 9/16. That'll put me at something like 11 hrs on track for 2021. This car has definitely logged more track miles than road miles this year. This has me wondering if I should be changing my oil more frequently than once a year. I already flush the brake fluid before each event but I'm thinking I might want to change the oil after Summit Point. Anyone have any information on how frequently race oil (Redline 40WT) should be changed? My engine lives at 4000-8500 RPM on track and oil temperatures will get to ~220F.

In reply to infernosg :

It might be worth sending an oil sample out to Blackstone after a race day and see how much it breaks down. Where is the oil temp measured? I think the rule of thumb is that oil entering the engine should not be above 205 degrees.

In reply to dannyp84 :

I was out of town on business all last week but I managed to find some time over the weekend to put some heat into the oil and pull about 3 oz for an analysis. Hopefully I'll get that shipped out today. Didn't get around to it this weekend but I will be changing the oil before Summit Point.

My oil temperature sensor is beneath the filter. That IS where the oil enters the engine based on the FSM. I've seen a bunch of different limits (link) and it looks like I'm in the "beware" ballpark. There are some things I can do to improve flow through the oil cooler but those will have to wait until Winter. For now it appears to only hit 220F in traffic, especially during the hottest time of the day so I don't think it's a huge issue. Hopefully the oil analysis will give me some insights.

I finally got around to doing something about how loud the car is. My fabricator friend had some free time last week and we spent a few hours coming up with a plan that didn't involve rebuilding the entire back half of my exhaust system. A few posts back I mentioned I purchased another Burns Stainless race muffler as well as material to repack my existing one. First I decided to take it apart to see what I was working with. I was expecting to find a pile of dust but the packing seemed to be in pretty good shape.

If anything the scrubble was a little compacted down so I "fluffed" it and reassembled the muffler without replacing anything. Burns calls for 1.25 lb of scrubble plus a layer of fiberglass met (what I purchased earlier) but I didn't see any reason to replace what was already in there and I'm still concerned about the durability of fiberglass mat in a rotary exhaust. The new muffler went in just upstream of the current one. We were able to cut out a 12" section of straight pipe and weld it right in. Clearance is a little tight with the driver's side rear axle but there's about 1/4" with the suspension at full droop.

The other change was at the exit. The previous setup pointed slightly up and to the left. This was changed to be angled downward at about a 30 degree angle.

The reason for this was because I was trying to avoid buying any new pipe. The new tip is a trimmed section of the 12" removed to install the new muffler. We just cut the old tip off at one of the bends and welded the straight piece on then I cut it to length. Here's what the old setup looked like:

and the new:

So not only is it pointed downward it's also a straighter shot.

So how much did this change the sound? Honestly? Not much, I'm afraid. Single stage mufflers filled with stainless steel scrubble can only do so much, I suppose. The overall intensity is definitely down and the higher frequencies are supressed a little better. It's still loud but an "edge" has been taken off. Instead of a eardrum-assaulting "blat" it's more of a duller thud. I don't know it's kind of hard to explain. Hopefully this'll get me though Summit Point (103 dB limit) and I might look at some other options over Winter. I've seen some "ceramic" fiber wools advertised as being both resistant to high temperatures and better at sound insulation. I might try packing the larger rear muffler with some of that.

Quick update for now. Ran Summit Point Main with AutoInterests this past Monday. Above all else it was refreshing to have in-person instructed sessions again. My first since 2011. So much more helpful that trying to figure stuff out myself; especially on a new-to-me track. Absolutely beautiful weather for the Mid-Atlantic region in August - low 80s and sunny all day. My instructor was probably more aggressive than I would have been if our positions were reversed but he knew his stuff and there were no issues in any of the 5 runs. We had fun chasing down, and passing, a GT350 multiple times. Someone showed up with a SRT (I think) Durango, which was comical to see on track. I think I passed them three times during one of the sessions. I'm definitely starting to learn the capabilities/limits of the car. Unfortunately no GoPro/Garmin video. Since this was a "formal" HPDE I didn't think it was appropriate to have a timing device running in the car and since the 5-10 minutes both before and after the runs were spent preparing/reviewing with my instructor I never remembered to start the GoPro. I'll leave this summary with a single photo:

I'm happy to say there were no noise violations so either they didn't care or I somehow came in under the 103 dB limit. Oil temperature peaked at 227F, which seems to be around the maximum regardless whether it's 80F or 100F that given day. I still think that's a little hot but I'm not going to do anything about it for now. Oil analysis results came back last week and there's nothing special to report.

Looks like I can probably go longer between changes. About 2/3 of that 450 miles is on track, which was three TNiA sessions: 2x Dominion and VIR. I'll finish out the year on the current oil, which will have a HPDE at Summit Point, a TNiA at VIR and a full weekend HPDE and VIR (Hyperfest) then do another analysis before changing the oil and filter for the 2022 season. I'm hoping to squeeze two more events: a TNiA at Dominion in September and a TBD after Hyperfest. Unfortunately the funds in the "fun" bank account are dwindling and a HANS device and new tires are needed in the immediate future.

Theoretically a thinner oil should travel through the engine more quickly and thereby run cooler, if you're worried about that.

This car looks and sounds great in the dyno video, btw. I can't wait to get my bridgeported irons back for the 12a and put it together. Are you able to measure intake air temp? I've been wondering how much cooler I can get the intake by building a box like yours over the Weber with cold air routed toward it.

In reply to dannyp84 :

I ran Idemitsu 10W30 race oil for a while. The trade off is slightly lower oil pressure and maybe some increased blow-by. I've been watching oil pressure, which is generally good. Idle is >30 psi hot and anything over 3000 RPM is 70+ psi. It seems to peak around 75-78 psi, which is lower than I expected with the Racing Beat "street" regulator advertised at 80-85 psi. There's a number of possibilities but investigating would involving pulling the engine so I'm not worrying about it as long as oil pressure generally stays above 30 psi at idle and 70 psi at WOT. With the Idemitsu 10W30 I would see 25-30 psi at hot idle. Better cooling is why I don't run a heavy 20W50 like most seem to recommend.

I do measure IAT. With the airbox it's generally no more than 10F over ambient as long as I'm moving, even just slowly. The air box really is a game changer. Without it my IAT would creep up over 140F even while moving.

I currently run either 20w-50 or 15w-40, but after reading more about thinner oils being more effective at cooling, I think I'm going to make a change. That's a wild variance in intake temp with an air box, I'll have to see what i can come up with that doesn't effect hood clearance. I assume you won't be making it to Gridlife at Mid Ohio this weekend? Logan from Defined will be there running the 4 rotor race/test car.

In reply to dannyp84 :

I may have to bump up to a 20W50 eventually. I'm noticing a slight drop in oil pressure over time. I don't have any obvious leaks so it's possible something it going on internally. I'm thinking either the oil pump is wearing or I'm starting to lose the front cover o-ring. Both are easy fixes but they involve pulling the engine. Not something I'm going to worry about now. If it becomes noticeably lower I'll pull it this Winter.

Regarding air temperature it turns out there's a big difference between pulling in ambient air and pulling air from a hot engine bay. I cringe every time I see someone running open ITBs/carbs just knowing how hot IATs will get. Another benefit was I saw a small bump in power with the air box on the dyno. It wasn't much, maybe 1-2 hp, but I'll take it.

Unfortunately Mid-Ohio is like a 8 hour drive. I used to live in Ohio so I've driven there before and I hope some day I'll make it back. I've seen Logan's car in person and it's wild. I've thought about running with Grid-Life should they ever come further east. For now I'm content with track days and HPDEs to work on my skills as a driver. The bigger issue is the car would currently slot into Track Modified due to the polycarbonate rear window and it won't be competitive. It wouldn't be too hard to track down a stock hatch to swap in and drop down to Street Modified but I'd still need to install more safety equipment.

In reply to infernosg :

Were you able to turn the timing up a little as a result of lower intake temps?