'85 Merkur XR4Ti Rally Car

I love it. The new engine brings a whole bunch of advantages I'm sure, without changing the character of the car like a V8 swap might.

RallyPerry said:

Ugly 'ol race car has officially entered test and tune status.  First start was around Thanksgiving, I've driven it a couple hundred miles in the last week or so.  So far the car is reliable and fast.  I started from scratch with so many systems I'm kinda surprised everything works so well.  Things like power steering, brake booster delete, hydraulic clutch conversion, cooling system design, ecu controlled alternator, etc all work great.  The 2.5 is responsive and torquey, plenty of power even at low boost and early in the tuning process (rich mixture).  Needs paint!

Trolling South African Gumtree for old Sierra's...... Nah, to expensive...

But cool future project idea

I am very excited to see what the new and improved Merkur can do, thanks for updating the thread!

Enter the sketchy-

I've been doing some tuning in small steps and decided to kinda jump up to 9 psi or so in the last couple days.  As I started dialing in ignition and fuel settings it keeps getting faster and I keep having to dial back the boost table to keep it manageable, it ended up around 10psi for now.  Long story short the car will now quite easily spin the skinny snow tires on asphalt in 4th gear at highway speeds even at part throttle with a boost table that trims pressure per the TPS.    Anything over about 3K rpm and 60% throttle happens in a blur of noise, wheelspin, and rev limiter.  It's already faster than I ever imagained it'd be.  It's ridiculously overpowered for a rally car, so I'm dialing things back a bit and already have the wiring in place for a boost blend knob on the dash (MS3X).  I think I'll label the top half of the blend knob "DNF".  It's a riot to drive sideways though.  So for now I'm detuning a bit and trying not to blow it up yet.  It's easily driven in a milder state, quite pleasant puttering around town acutally.  I know I can get a setup that works for rally use dialed in easily enough when the time comes.

Any 2.5 turbo guys out there have advice?  it's a stock longblock that I never even pulled the head off of.  I try to avoid scope creep during the project phases where I might burnout, so I got it running first..  Now that it's running I'm evaluating what to do for reliability in essentially a 5 to 20 mile long dyno pull of a rally stage.  The power comes on hard and fast and I can't imagine it'll stay together for long in rally use like this.  In addition to a much milder tune I think I'm gonna pull it apart and regap the rings for hard use, maybe ARP head studs and a multi layer steel head gasket.  I might key the crank while it's out for future dogbox usage.  I will save further upgrades for the next engine I think.  Maybe it'll hold up as-is.

Other things to do are many, such as paint and other chassis wiring replacement.  But I think I need to put in a double master for the brakes and a bias bar.  it locks the fronts too easy even with the adj prop valve backed off.  A touch of hydro handbrake as you apply the pedal results in much better braking.  I could move the adjustable prop valve to the front, anyone done this before?  Bad idea?  it'd be an intermediate fix for an event or two (or decade) until I redo the firewall/pedal setup again.

Random other note, the open side exhaust was head splitting loud so I put a Borla on it a few days ago, It quieted down a bunch and everyone doesn't stare when I drive by anymore lol.  Now I can hear all the obnoxious race car rattles.

I need to weigh it again.  it was 2331lbs without fluids, hood, or exhaust and on rally tires (heavy).  I think it's around 2500 now. 

Random update.  I've driven it about 500 miles now with the only issue being a loose hose clamp dripping a bit of coolant.  Since it's working great, of course the next step is to take it back apart..  I am proceeding with the plans above for the engine, regap the rings for hard use, new head gasket with ARP head studs.  Pull the crank and have a keyway cut into it. 

Next event is Sandblast Rally on March 5th.

Random update.  I gapped the piston rings and did a bunch of transmission work right before we ran the test and tune in Michigan at the end of January.  Car ran great, tore out a tow point in the back.  I had a tension compression rod bracket half fall off, but there was so much ice and snow under there that I didn't know it until I got home.  I'll blame any bad driving towards the end of the day on that..

While I had it apart I fixed up a cracked header, fabricated a downpipe for the wastegate, glued the timing sprocket on with retaining compound, and a bunch of other little things.

Awesome!

I like the one post reads "this thing is way overpowered, I need to dial it back" and the next update is "so I pulled it apart and gapped the rings and added headstuds for more boost..."

Crew chief picks the colors for this stuff..

This kid is 13, my youngest daughter, and a better wrench than most dudes I know.  She's been super helpful throughout this project.

Moving on to lately..  

I'm leaving a lot of stuff out that I've done, but the big thing at the moment is paint.  

I just peeled making tape off last night, it's looking pretty good.

Red and black before, on the way to being 'rothmans like' after.. 

I don't think we'll apply the stripes and whatnot until after sandblast rally.  Or install the rear flares.  Always a work in progress.

That's Rust-Oleum.  I highly recommend the enamel catalyst and Japan dryer if you do this.  The white turned out a bit rough due to dirt getting in as it took days to dry.  With the Japan dryer and a few lessons learned the blue looks great.

In reply to Run_Away :

Excellent observation lol.

Rally is all about reliability.  It is dialed back a bit for the "event spec" and overbuilt a little for that (maybe).

For driving it to work I have it tuned right at the slip point of the supposed 400 ft-lb rated clutch.

Do you have any pics of how the rear tow hook was attached?

Need to come up with something for my XR.

Thanks!

tell me more about gluing the timing sprocket on. Is it basically just adding loctite? how'd you time it without the cams on, or did they come off after you'd done the gluing?

New livery looks good! You ended up using an MS3 for management, right? I think I remember seeing that on your FB page.

Wow that Rusto paint job looks great! I've also had good results mixing Rusto with enamel hardener. I use the Majic brand stuff from Tractor Supply. Plus now you can touch up with off-the-shelf spray cans as needed.

In reply to bluej (Forum Supporter) :

Yes MS3.  I don't have a great photo of it installed but attached is the panel I built and one of the underhood harnesses back when it was in progress.   I added an enclosure for Arduino based CAN experiments and more IO.

For the timing set I used loctite 648 and fresh diamond washers.  Technically on this engine you could just glue it wherever and adjust the cam pulleys.  I didn't want to mess with that now.  I timed it and pulled the chain and hydraulic tensioner.  I cleaned it all up to prep for glue, etc.  Loctite and reassemble without the oil pump chain or hydraulic tensioner and no front cover.  Apply Loctite such that the sprocket is glued but the front pulley is not.  I used a large quick clamp tensioning the chain guide and snugged the front pulley down, left it overnight.  Then you can remove the front pulley and put it all back together properly.  Timing was spot on after reassembly. A keyway is better but these long blocks are cheap and I did all the engine work over a weekend so I didn't want to send it out.  

Sweet. Gonna be strange seeing that car not in black and red :)

In reply to GPz11 (Forum Supporter) :

Originally it was bolted to the bumper structure which is a bad idea.  Honestly I noticed this but ran out of time before going to Michigan and only fixed the front one.  After pulling stuff loose we just welded some 1/4 inch by 2 inch steel strip into the body shell next to the fuel tank and connected it to the one on the bumper.  It's not pretty, was a quick onsite repair.  

In reply to RallyPerry :

Thanks, I was "talked to" at the track for not having proper tow hooks.

You know it's getting close to an event when you work all weekend and don't take a single picture.  I'm doing both rally car work and director work, it's keeping me busy.

Car is reassembled and all the lights work etc..  I fixed a bunch of little things all over. I made some sand shields/flaps in the wheel wells, swapped in the spare transmission, built a better side exit exhaust with slip joints and solid mounted back half, added what is essentially a driveshaft loop,  dropped the fuel tank out and resealed the pump flange, fixed a few wiring things etc.. 

 I also ran a few datalogged tuning runs after recalibration of the O2 and fixing a MAT sensor issue.  I lowered boost another pound and remapped the boost controls to be more drivable under power.  This car would be impossible to drive well on an old school pure wastegate setup. Once the boost threshold is achieved the throttle plate is useless and power is really controlled by the boost solenoid via the TPS/RPM map.

The only thing left for tonight is to reinstall mud flaps and maybe trim the front flares for mudflap fitment.  

I panicked yesterday when the car had a driveline vibe over 80.  It showed up with a trans swap in January so I put the spare back in Saturday.   Long story short it was an improperly machined driveshaft yoke.  I found it by running the car on jack stands up to about 100 mph to find the vibe and then on a hunch I measured the yoke spline section OD.  It was 1.490, the couple spares laying around were within a thou or two of 1.500.  I swapped the yoke and it's vibe free again thankfully.  

I found a picture my wife took.

I had one of our priests bless the car for us.  He's been checking it out for a while as I've been fixing it up.  He was excited to see it painted and shocked that it's Rust-Oleum lol.  

Currently involved with (re)building a road racing XR4Ti. Thanks to the OP and Perry for posting all the good XRAtty info & pics. Subscribed...

Sandblast rally report.

Despite being around rally a lot this was our first event together with actual stage notes.  For Patty it was also really the first time on stage with the car running well.  At least for a couple stages..

Paint turned out nice.  

These folks seemed particularly interested in the car... (Good to see yall)

Because of so many 'other duties' and trying to get the car painted in time, my general approach to this event was to show up with a running car and not worry about a whole lot else as far as preparation goes.  The car has been very reliable now for around 1000 miles, and I only had pretty much everything in the driveline apart lately with no testing.  What's the worse that could happen?!

We did the shakedown stage maybe 5 times without any issues.  The car has plenty of power even at a low boost setting for "rally reliability".  I was running around 8psi which feels slow compared to the normal setup but was enough to spin the rears on sand up over 100 mph.   I immediately noticed that our car was really quiet and people don't seem to get excited about quiet cars.  It was nice for us inside it though.  We had a lot of work to do on our timing with the notes and whatnot.  I also needed to get used to driving on stage with it.  So shakedown was a success and very helpful.

I'm used to volunteering and having lots to do, competing was nice and low key comparatively speaking.  On the morning of race day the 13 year old crew chief and I discussed the fact that everyone else seemed busy doing stuff in service so we checked the oil and set the tire pressures for good measure lol.  Car ran great and off we went.

Since we were brand new to notes together, I drove the first stage like a course car.  This means you drive what you can see and be a bit conservative.  We passed a lot of broken cars already and caught another competitor despite this.  We followed the car we caught for around a minute before we could get around.  Even with all this our stage time wasn't bad.  The car is plenty fast, the wide range of rpm that it makes power at is great on stage.  I didn't really need to shift up and down much and even 90 degree corners could be powered out of in third gear or so with lots of wheelspin.  I was worried about cooling but the few times I looked it was always under 190F which is tstat temp.  Intercooler temps also stayed around 90F on a day that got up to 80 or so.  Things were good.

Second stage we jumped ahead one in the start order and still caught another car on stage.  We were talking about the notes a bunch in the car and in a few places i was starting to trust the notes and go a bit faster.  Towards the end of this stage a mild miss shows up.  First thing I thought of was the Merkurial t shirt.

At service I looked things over, we put some other plugs in thanks to another crew who had a set.  it seemed to run better by the time we left. 

3rd stage was cancelled, 4th stage it ran decent for about a mile and then the miss returned.  Power was down but it was still plenty for a mile or two and we were getting the in-car relationship sorted.  This felt awesome and fast until the car slowed down more and we ended up just cruising along. 

Long story short the miss got worse and worse until we did around 4 miles of the last stage at 7mph.  We swapped an ignition coil and changed some dwell settings and all sorts of attempted fixes to no avail.  But, we were thrilled to finish!  Only about half the 2wd field managed to finish so we count that as truly an accomplishment at such a tough event with a new driveline package that I made up mostly from scratch.   And, because we had second by a large margin, even though we crawled the last stage we still managed to hang on to 3rd place in 2wd overall!  Patty was so happy to get a trophy.  

So, what was wrong with the car?  it's complicated..  Remember all the salt from the Michigan test and tune trip on an open trailer?  somehow when I washed things off I think some salty water got into the low current connector on the alternator.  This is an ECU controlled alternator with some data lines and a voltage reference line.  So there was a "water mark" inside the alternator connector and the pins rotted completely out of it into just a puddle of goo in the bottom of the connector.  weird..  So this quit working at the event at some point, or got intermittent for a while at least.  I used the default dwell/voltage compensation curves in megasquirt, which turned out to be inappropriate for the LS coils and caused issues with coils overheating and shutting off for a while.  Also, I know I put in the injector dead time compensation curves provided with the injectors but call me a liar because somehow they were not correct.  All of this is just a bunch of fancy reasons why the car didn't run well when the alternator was not charging.  

So, now it has a couple new coils, new plugs and wires.  The voltage compensation curves are fixed and it runs great even when the alternator is not charging.  today a new alternator showed up in the mail so that should be fixed up soon.  

During post event testing I also put some 17 inch focus wheels on it and promptly broke a CV joint..  But that's for another post.

The car is looking great!

Turns out I broke an axle, not a cv joint.  I'm trying to decide how much scope creep to allow here.  I'd like to go to 930 sized cvs and better axles.  Cost for better stuff varies greatly.  I think I could get by with a really good set of stock sized 100 mm cvs and a good axle.  However, stepping up a size might mean that less expensive stuff will offer better reliability and a better upgrade path in the future if needed.   I have questions.  Does anyone have experience using the empi 930 cv axle kits in something that is not a buggy?  Anyone know of a good source for 100 mm to 108mm cv adapters for the outer end?

  This might turn into a fabrication project.

On other topics I changed the voltage regulator inside the alternator last night and installed an old OEM axle spare that was in the pile.  Due to recent changes in the injector dead time vs voltage curve I found that the tune was now overall lean.  I did some late night rough tuning work and it's running great again.  It was nice to drive it to work today

https://www.vividracing.com/driveshaft-shop-rear-100mm-108mm-adapter-plate-cadillac-cts-20042008-p-152861798.html