ITS/E Production SCCA RX-7

In reply to Pete. (l33t FS) :

Did you use Racing Beat's universal muffler or hack apart one of their kits? Years ago I built an exhaust using their universal parts and the quality was good. I've read some questionable things about the quality of their exhaust kits lately. I'm not sure if that extends to their universal parts as well.

I'd never seen that chart from Racing Beat. I DO need to do something about my water pump speeds since I'm running at 8000+ RPM. I have the Atkins serpentine pulley kit, which I think retains the stock ratios. I did see someone comment about modifying a 6-rib supercharger pulley to work with the Atkins kit so I may look into that over the Winter. I'd run the RB single sheave pulley but I need the accessory mounting holes for my crank position sensor's trigger wheel. It doesn't look like there's enough meat on they pulley to drill and tap. 

wvumtnbkr said:

How is the ducting to the radiator? 

My car would run hot on track without the undertray keeping the air directed through the rad instead of allowing it to go under the car 

ducting is huge on this, learned that the hard slow way. 

infernosg said:

In reply to Pete. (l33t FS) :

Did you use Racing Beat's universal muffler or hack apart one of their kits? Years ago I built an exhaust using their universal parts and the quality was good. I've read some questionable things about the quality of their exhaust kits lately. I'm not sure if that extends to their universal parts as well.

I'd never seen that chart from Racing Beat. I DO need to do something about my water pump speeds since I'm running at 8000+ RPM. I have the Atkins serpentine pulley kit, which I think retains the stock ratios. I did see someone comment about modifying a 6-rib supercharger pulley to work with the Atkins kit so I may look into that over the Winter. I'd run the RB single sheave pulley but I need the accessory mounting holes for my crank position sensor's trigger wheel. It doesn't look like there's enough meat on they pulley to drill and tap. 

It came with the car, it is a bolt in muffler for an '83-85, and an exhaust shop made a pipe to go from a converter on the RB header to the muffler.  Judging from looks it is from the 90s or early 00s.

So yes, my '81 has a '83-85 muffler and my '84 has an '81-82 muffler 

If you heard rumblings about the quality of their non Italian made exhausts, you probably heard it in part from me.  Not relevant to thread other than "just say no to stainless exhaust components on a rotary"

Where does your trigger wheel mount?  Inside or outside?

I would say lose the Atkins belt system unless it has a smaller e-shaft pulley. We ended up with a RB lower pulley and IIRC we took an air pump pulley and made it work on the alternator by boring it out a few thous'. We also cut up a stock water pump pulley and mated it to a cut up lower AC pulley. Neither job was easy but we had mills and lathes and unused parts laying around.

You can buy everything off the shelf now.  The water pump spun about half the engine speed and the alternator didn't make 12V until about 3500rpm. Never had a problem throwing a standard V belt.

In reply to Pete. (l33t FS) :

Not trying to hijack this thread but do you know if they're universal mufflers are still any good? My trigger wheel mounts to the front of the main pulley where the accessory pulleys would normally bolt to on a stock setup. It works with the Atkins and RB dual sheave pulley because they're designed to work with the factory accessories.

In reply to jgrewe :

Nope, confirmed it's all stock diameters, so according to the RB catalog I shouldn't be going faster than 7000 RPM. The easy button is to swap back to a RB dual sheave pulley but that doesn't get me all the way (8400 vs 8500 RPM). I had a catastrophic belt failure with the dual belt setup at VIR a few years back. Apparently no two belts are exactly the same and the slightly smaller of the two decided it'd had enough. I snapped and took out my crank position sensor, trigger wheel and water pump pulley and ended my weekend early. I've never seen it done but I suppose I could run just one belt. My alternator is side-mounted so I don't worry about water pump pulley contact.

The ideal solution is to use the RB single sheave pulley with the Mazda Comp water pump pulley but I don't know if I can make that work with my trigger wheel. Normally it wouldn't be hard to drill and tap a few holes but it doesn't look like there's enough material there.

In reply to infernosg :

No worries about hijacking, this is all valuable info to anyone with a rotary Mazda. I'm going to be consistently spinning this engine to 8k, so I need to have a look at what pulleys are currently on the car. I'm upset with myself for not scrambling to get the car ready in time for the SCCA halloween event at Nelson Ledges, there was a good battle in ITS last weekend between an FC and a Z31 300zx, and I could've been in the mix if I could've passed tech.

In reply to dannyp84 :

I'd be willing to bet your 190 hp, 6-port engine requires more RPM so I'd definitely look into the Mazda comp parts if it doesn't already have them. I think the Mazda comp water pump pulley is pretty noticeable. IIRC it's the only one that's single-sheave and is considerably larger than stock.

From what I have been able to figure out the stock water pump pulley is ~3.75 in. My plan is to modify an Edelbrock 3.75 in., 6-rib supercharger pulley to work as a main pulley with my Atkins kit. If my assumptions are right it'll require some turning in a lathe and 4 drilled holes. That'll get my pulley ratio close to 1:1, which should be good for around 8500 RPM according to RB.

In reply to infernosg :

Are those parts available directly through Mazda's website? Also for your application what about RX-8 parts since they were designed to rev to 9k? I need to talk to Logan and find out when he can get the car in to take a look at the tune and improve the exhaust. I also need to install my new harness belts and peel off the old livery/come up with a new scheme, which is way outside my wheelhouse but should be kind of fun. The car has kind of sat unattended for a few weeks while I enjoy the FB now that it's up and running - I wanted a few chances to drive the car before the weather turns. I've also been road biking and riding motocross about once a week, gotta squeeze in all the outdoor activities I can before it's too cold. 

In reply to dannyp84 :

If you aren't already I highly suggest registering with Mazda Motorsports: https://www.mazdamotorsports.com/ All you need is one "racing" event a year. It used to be timed, but I just do HPDEs and they were willing to accept me. The Mazdaspeed Parts Store prices absolutely cannot be beat. The only caveat is you're only supposed to use it to purchase parts for the race car.

As for RX8 parts, there is some interchangeability but not as much as you'd think. Anything external to the engine isn't compatable. The eccentric shaft is a direct replacement, and is lighter and cheaper than the RX7 one. The front stationary gear is another part that is stronger. The rear stationary gear is as well but it requires a little modification to line up an oil feed hole. It's an easy job with a rotary tool. The rotors can be used but they're only a slight bump in compression ratio and the apex seal slots need to be machined deeper to fit RX7 style seals. Unless I fell into a pair of RX8 rotors it's not a modification I'd do. The extra oil seal is nice but the side seals are a massive pain. I'm sure there's other things but those are the big ones. I'd make sure any of these are permitted in whatever class you plan on running.

Does anyone know where to find class-specific rules for SCCA? When I got the car it was on Hoosier S75 tires which I'm told are a spec tire for E Production, but I don't

know if I can run those for ITS? I found the general competition rule book but it doesn't break down specifics of each class from what I can tell.

Did you review section 9.1.3? It starts with the IT general rules and then moves to the specific. With regards to tires IT is restricted to DOT tires and EP is not but read the rules for specifics.

In reply to Rons :

Oh I found it thanks! I was in the wrong section before where it just lists the various classes.

In reply to infernosg :

Any suggestions on navigating the parts ordering page on mazda motorsports? I registered but none of the part numbers or keywords I've searched are working. I'd like to get a complete set of wheel bearings before the season starts. 

Also a quick update on the car, Logan at Defined spent most of the weekend building a stainless exhaust with two mufflers from the header back, so now I can drive the car without irreversible damage to my hearing. I'm keen to see whether it'll also make more power, especially under the curve, as the old exhaust was 3" diameter which seems excessive. 

Just call Mazda motorsports if you can't find the parts easily on their site. 

They've always been very helpful for me

In reply to sevenracer :

They were very helpful! Wheel bearings aren't cheap but since the car is on slicks I feel it's probably best to grit my teeth and buy the quality parts.

So as the racing season draws near I have some decisions to make. The car is scheduled to be dyno tuned next Friday, where hopefully Logan can remedy the lean condition above 6k rpm, and get the timing where it needs to be. The first available road race in my region is the Hoosier Super Tour at Mid Ohio in May, which from what I can tell runs EP class cars but not IT, so I'd have to run EP. My next option is to sit tight till June and run the regional at Nelson Ledges, another track where I have some experience. I'd like to rule out Pitt Race for now, as I'd like my first race to be a familiar track. I don't have the experience to know whether the Super Tour would be a rude awakening compared to maybe racing ITS later on instead, but my gut feeling is to just go for it and just seek to benefit from the seat time. I have plenty of race craft to learn before I worry much about my outright pace anyway, just thinking out loud here. I'll be happy this year if I get to race at Nelson and Mid Ohio, the latter of the two apparently has new pavement. I also have enduro experience at Watkins Glen, which could be a fun trip for a sprint race later in the summer.

I assume you have your comp license already? I'd go ahead and run at Mid Ohio. 

The Super Tour will almost certainly have more "serious business" competitors, but often there is a pretty wide spread in lap times for the field, so you might find someone to race with even though your car is ITS spec.

There's a guy named John Hainsworth (out of NJ I think) who may be there. He's a top competitor (qualified on the pole for 2023 Runoffs) in EP with a 2nd gen RX7 vert. Nice guy, knows a ton - you should introduce yourself if you see him there.

I never raced at mid ohio, but I did a couple of motorcycle track days and my first SCCA race school at Nelson Ledges - really fun little track!

In reply to sevenracer :

Yes, I got my comp license last summer and I'll look for John on the entry list. Nelson Ledges is really underrated in my opinion. It's a fast, fun track and compared to Mid Ohio I think it's a lot easier on your brakes. 

In reply to dannyp84 :

Unless you have a ton of top end, there is only like one place to really use your brakes at Nelson.

Although getting through the Kink without lifting makes for a very short braking zone, so it's best to give a little dab there...

(When I played there with a stockish SA, WOT was my maintenance throttle through most of the corners)

In reply to Pete. (l33t FS) :

All my experience there has been in our Champcar 8th gen Civic, I think in that car I've seen 121 mph or so before the kink. Nelson is a lot of fun in that car too, since there's really only one slow corner that really highlights the downsides of fwd.

In reply to sevenracer :

Well I'm registered, the field looks pretty stacked but I'll just use the weekend as a learning experience and see how the car and I stack up.. I have the latest rulebook and I think they lowered the weight minimum for the FC in E production, if my logbook is correct I'm currently almost 400 lbs over the limit. I have a 4lb lithium battery in my street car that I could swap over to save some weight but I bet lithium won't pass tech. Going to spend the next couple of weeks going over the brakes and bolt checking everything before race weekend. I'm already edgy and excited.

In reply to dannyp84 :

That's about where I was at too... about 7k in 4th gear.  The speedometer pegged just after the 2-3 shift so I had no idea for miles per hour.  I could keep pace with people who were measuring laps in the 1:20-1:24 range and I was having all the fun I could handle.

Braking after that for the left hander was fun, as mentioned 

In reply to dannyp84 :

What is your weight? My STL spec car weighs about 2540lbs post race with me in it.   My STL min wt is 2510. Mine is the heavier 91 chassis, and I still have a full size lead acid battery. Headlights removed, and lexan hatch glass.

A buddy with a fully prepped early chassis runs a spare tire and lead bars to make min wt, and he probably weighs 50 lbs more then me. 

In reply to sevenracer :

I'm going to check via corner scales this weekend, but based on what the logbook says, minus the weight difference between me and the previous owner, and minus the 50 lbs of ballast I just took out of the passenger floor, I should be at 2533 roughly. My rulebook says my minimum weight for EP is 2170 or thereabouts. I probably don't have time to source a lexan hatch, but I could pull one of the headlights and throw in my lithium battery from my street car, it weighs 4 lbs vs whatever the big optima currently in the car weighs. 
I'm trying not to worry too much, though, I need to qualify within 115% of the lap record at Mid Ohio, which is 1:36, so I need to do a 1:50. I already did a 1:48 on club course which is longer, and that was my first time ever driving the car. So I'm cautiously optimistic.

It sounds like you'll be fine on qualifying.

Not sure if a tin top FC can make that minimum weight, but I bet the early cars can get pretty close.