The Merkur Club of America Forums

Hi All,
This past weekend at Brainerd International Raceway, we raced our newly completed (three year build) '87 XR with World Racing League.
Here's the good:
Car weighs 2460 lbs. caged with a nearly full tank of fuel.
The brake upgrades front (SVT rotor/PBR) and rear (TC rears) were amazing and we never had an issue.
Ran 10 lbs. of boost all weekend, completed somewhere around 100 laps, 250 miles, and no problems
Hit over 100 mph in the long RH sweeper which was a thrill
Most importantly, we had a blast shaking down the car and being on track.

Here's the bad:
Despite corner weighting the car and getting a 52/48 balance with a 51% cross weight, we were lifting the RR in every hard RH corner.
Even running 10 lbs. of boost, we were getting walked by everyone else down the front straight from a C5 Corvette to an old VW Golf
As a result of the two points above, we were dead last and the slowest car there.

I would like to personally apologize to everyone that had a hand in helping us with this build be it via purchasing parts or obtaining advice. I thought we had a good set up with Koni coil overs up front with 400 ish springs and 650 in back with a big rear sway bar. I'm open to other suggestions for anyone who has road raced an XR. Lots of work to be done in the off season and I want to show up to the next race with a tested and properly working suspension.
The whole team loves the car and it received quite a bit of admirers at the track so we want to try and develop it to its fullest potential.

Greg

Congrats on getting through it! Sometimes with those races that's the hardest part.

10psi isn't much, that's wastegate pressure (on a stock wastegate). If you have an intercooler, you're likely safe to bump that up to 15-18psi (Most use a Gillis manual boost valve).

The lifting a wheel is likely due to body flex, which the rear of the XR is not very stiff. Even something as simple as using a piece of angle iron to tie the rear shock towers together (no welding required). See the Merkur Encyclopedia link for info: http://www.merkurencyclopedia.com/Suspe ... brace.html

Spring rates sound right for road-race type activities (most seem to run 350 front, 650 rear, e alt Jeff Esteban and MC2 recommended values), you might also have rear beam flex. Esteban also makes solid (aluminum) rear beam mounts which should also help keep that rear planted. Big rear bar is why you're lifting the wheel, but with the shock tower tie in and stiffening the chassis (not the springs) should help with that.

BTW I'm no expert, I'm referencing those with experience who have been helping me, and results of my own research. Sounds like that was a good shakedown and experience, now it's time for a few improvements and I'm sure it will go great next time!

I'm about to take my XR to an SCCA Track Night in America, we'll see how she performs (likely not too well with stockish springs).

i didnt see you mention anything about bushings. If you didnt do that, do ALL of them.

Solid mount the rear subframe and go hard (Black) delrin bushings everywhere else. Use the MC2 rear diff mount. MC2 makes steering rack bushings as well.

We ran 10psi simply for longevity as the car was at WOT for 15-20 seconds at a time, 10 times per lap. Everyone that I've spoken to about endurance racing the turbo 2.3 is keep the boost at 10 or below and it should live.

The car has all Powerflex bushings in the rear subframe and we spent a lot of dough with MC2 Racing with the solid diff mount and other assorted urethane bushings. I made a bar with rod ends that tie the rear shock towers together plus the rear stays on the cage tie in with them as well. The body is pretty stiff at this point. With over 20 years of racing, I thought I had the knowledge to set up the suspension correctly but it appears I was pretty far off the mark.

Main thing we need to do next is get more negative camber up front by either camber plates, eccentrics, or some mods to the LCA. Again, any recommendations would be greatly appreciated.

Dangie wrote: ↑Tue Sep 11, 2018 5:57 pm We ran 10psi simply for longevity as the car was at WOT for 15-20 seconds at a time, 10 times per lap. Everyone that I've spoken to about endurance racing the turbo 2.3 is keep the boost at 10 or below and it should live.

The car has all Powerflex bushings in the rear subframe and we spent a lot of dough with MC2 Racing with the solid diff mount and other assorted urethane bushings. I made a bar with rod ends that tie the rear shock towers together plus the rear stays on the cage tie in with them as well. The body is pretty stiff at this point. With over 20 years of racing, I thought I had the knowledge to set up the suspension correctly but it appears I was pretty far off the mark.

Main thing we need to do next is get more negative camber up front by either camber plates, eccentrics, or some mods to the LCA. Again, any recommendations would be greatly appreciated.

Do you have an external oil cooler? With one of those, you'd likely be safe to run a bit more boost? It's an iron block and an iron head, likely plenty strong enough to turn up the wick a bit if you keep everything cool enough. What kind of temps were you seeing?

Didn't hear if you had an intercooler.

Also, pictures? We all love racecar photos!

Yep, we run an external oil cooler and remote filter. Ambient air temp was in the 70's and using Merkur Depot's FMIC/rad combo, we were running about 180 water and 230 oil. My fear was potentially blowing the head gasket and killing the weekend so we kept the boost down a bit.

Awesome to hear the car finally hit the track
AND did 100 laps / 250 RACE MILES with no issues?

10 psi is not much boost at all and I can see why the car was the slowest. 15 psi is stock boost level for the XR4Ti, I can understand not wanting to crank the boost through the roof, but at least turn it up to stock levels.

How are you regulating boost to 10 psi? Mechanically by the wastegate? (Just one hose from the turbo to the wastegate?)

Since you're running an intercooler then gillis valve is a must and works best hooked up exactly like the diagram below.

Do this and set to 15 psi and you will be amazed at the difference in HP/TQ/spool up time.

Dangie wrote: ↑Wed Sep 12, 2018 12:43 am Yep, we run an external oil cooler and remote filter. Ambient air temp was in the 70's and using Merkur Depot's FMIC/rad combo, we were running about 180 water and 230 oil. My fear was potentially blowing the head gasket and killing the weekend so we kept the boost down a bit.

Good setup! No wonder you had no issues

I'd call it a good, well-built starting place from which to improve on the speed a bit in the future.

merkurdriver wrote: ↑Wed Sep 12, 2018 1:30 am Awesome to hear the car finally hit the track
AND did 100 laps / 250 RACE MILES with no issues?

10 psi is not much boost at all and I can see why the car was the slowest. 15 psi is stock boost level for the XR4Ti, I can understand not wanting to crank the boost through the roof, but at least turn it up to stock levels.

How are you regulating boost to 10 psi? Mechanically by the wastegate? (Just one hose from the turbo to the wastegate?)

Since you're running an intercooler then gillis valve is a must and works best hooked up exactly like the diagram below.

Do this and set to 15 psi and you will be amazed at the difference in HP/TQ/spool up time.

Mike, yeah we ran a Gillis valve that we happily purchased from you and it worked perfectly. Since we knew this was our first race and there was no way we would have the car even remotely sorted, we turned down the boost to make sure everyone got some seat time. We didn't want to blow a head gasket in the first half hour and then spend the remainder of Saturday installing a new one. So do you think the engine would live for an 8 hour race at 15 psi? If so, we'll give it a try next time. Best lap we could muster around BIR was a 2:09 with me at the wheel. By comparison, a very well sorted, well driven Miata built to the full extent of the rules was in our class, GP3, and put down a 1:48. I'm sure we could get below 2 minutes had we been able to keep the RR down on the ground but 1:48 is a pipe dream.

Maybe come up form 10 psi to 13 psi for the next one and see what you think (temps, etc.) and then after that from 13 psi up to 15 psi ?
15 psi is stock, so its not like you are winding it up to the ragged edge or anything.

Are you running the small intercooler stacked on top of the radiator? If so, we have a new, larger intercooler that mounts in front now that works with your existing radiator. Simply unbolt the small intercooler off the top and install the large intercooler. They are at www.merkurdepot.com

On one of my cars here with this large intercooler at 18 psi on the stock turbo intake temps were 75 ° cooler than 15 psi stock/no intercooler.

The chassis is VERY capable once you get your suspension set up dialed in.

Motivational video:
https://youtu.be/NxFjyMUWLF8

Love that video and I would pay dearly to know what spring rates and dampening was used in Soper or Rouse's car.

We were using the FMIC/rad combo that you sell and it worked amazingly well.

You finished. This cannot be understated. It's the 1st and most important part of racing, IMHO.
Congrat's on that.
Thanks also for the vote of confidence on your chosen braking system. It sometimes takes flak. Despite the fact that it just plain works. Despite what some people think.
We used/tortured this system at Targa Newfoundland, and happily (as I set it up...) it was one system that performed without any drama.
On that, we ran with 500s up front, and 750s out back. Out handled a LOT of MUCH more expensive offerings in the incredibly challenging event.
There's a BUNCH more power available, even considering endurance. Kudos to you for proceeding carefully.
Keep us posted!!

Dangie wrote: ↑Wed Sep 12, 2018 2:22 pm We were using the FMIC/rad combo that you sell and it worked amazingly well.

The IC stacked on top of the rad is a good unit for a while depending on boost and cooling needs. With that combo in the car, an upgrade to our bigger intercooler will be very simple when the time comes for more/better cooling.

Mike McCreight wrote: ↑Wed Sep 12, 2018 8:51 pm You finished. This cannot be understated. It's the 1st and most important part of racing, IMHO.
Congrat's on that.
Thanks also for the vote of confidence on your chosen braking system. It sometimes takes flak. Despite the fact that it just plain works. Despite what some people think.
We used/tortured this system at Targa Newfoundland, and happily (as I set it up...) it was one system that performed without any drama.
On that, we ran with 500s up front, and 750s out back. Out handled a LOT of MUCH more expensive offerings in the incredibly challenging event.
There's a BUNCH more power available, even considering endurance. Kudos to you for proceeding carefully.
Keep us posted!!

Agreed that finishing is the most important part and it is always a great feeling to drive the car onto the trailer vs. winching up a busted car.

I had my concerns about the phenolic pistons but the whole setup surpassed my expectations. Huge thanks for letting me know your spring rates and I think we'll use those as a baseline for next season. Once the chassis can handle our current power output with ease, we'll ramp up the power levels to meet it. I'm already starting the rebuild process for the next engine and the cylinder head is going out for a full porting job.

Dangie,

Did you use any sort of Power Steering cooler? (selfishly asking as I prep my own car)