986 Boxster ChampCar Endurance racing build

[Endurance Racer]

HI All,

New build here. I'm taking on a project with a 986 V2 (2003) for ChampCar Endurance racing. I've been racing 944's both the 2.5 and 3.0L for several years and have had much success. Now I'm taking on the 986. It maybe brilliant or the dumbest thing I've ever done. And here is what makes this build a challenge. Per ChampCar rules the 986 V2 with manual transmission would be assessed 2 penalty laps. I can avoid the penalty laps if I run the Tiptronics transmission. That's the plan endurance race 986 v2 with Tip. So I hope you will be interested in my project.

Challenges and Goals:
Complete build and testing for Watkins Glen 7 hr race at the end of May

Get the racing weight under 2400# current weight is 3000# yikes! This include Poly Carb windshield, 20 gauge alum sheet for the top, Doors, Fronk lid, Trunk lid all reduced to just the outer skin. Door fixed, Fronk and truck lids pined. Alum bumper channels machined away material

Tiptronics: rules are pretty open on what I can with the automatic. I will be researching how to build this trans to be quick revving and quick shifting to get 0 to 60 times closer to the manual car.

ECU tune (ROW or aftermarket?) Any recommendations here would be great

Remove immobilizer?

17x10 wheels on a square set up. With 48 offset to clear front lower control arm all of the additional width (1.5") will be to the outside so fender flares will be required.

Must run 200 tread wear tires 275/40/17

Exhaust is fabricated to remove cats. OE manifolds to 2 1/2" pipe feeding 2 mufflers (one for each bank).

Most of the suspension, brakes will have to remain stock.

Engine oil cooling remote air/oil cooler and Accusump (can't afford the points for a baffled oil pan)

Tiptronics remote high capacity air/Oil cooler. I would love an alum torque converter but the cost with engineering and tooling is $12k

I'm selling off all the stock parts stripped from the car

Any Race car stuff you have related to the above please let me know
Also your experience with the above mention stuff would be helpful.

[steved0x]

275/40/17 is about about 25.66" diameter? I tried to run a 245/40/18 (25.72") in front with stock suspension and the tire was too tall and hit the OEM suspension lower spring perch in front. Unless that front wheel is pushed way out (and with a 17x10" it would be out there a ton!) that size may not fit up front. I have got a Maxxis RC-1 in that size I run on my Cayman in rear, I can try to put it up front on my Boxster and see if it clears that perch (unless you already tried it). It might be close!

[Endurance Racer]

Originally Posted by steved0x

275/40/17 is about about 25.66" diameter? I tried to run a 245/40/18 (25.72") in front with stock suspension and the tire was too tall and hit the OEM suspension lower spring perch in front. Unless that front wheel is pushed way out (and with a 17x10" it would be out there a ton!) that size may not fit up front. I have got a Maxxis RC-1 in that size I run on my Cayman in rear, I can try to put it up front on my Boxster and see if it clears that perch (unless you already tried it). It might be close!

You are correct 275/40/17 is 25.66" Dia. which is 16 mm larger Dia (or 8 mm on the radius) than the 255/40/17 I test fit without issues.
The 17x10 wheels have the same offset as my test fit wheel to clear the lower control arm strut so all the extra width will go to poke (38 mm) which will require fender flares.
If you have the time and can check with your Cayman rears that would be great. Thx

[steved0x]

I'll try it this weekend if I can get room

Looking forward to seeing your build!

[rastta]

Under 2400 is going to be tough. Not sure how you do it without CF hood, trunk, fenders and or doors. I'm at 2532 with hood and trunklid, but I have a 3.6 motor and 6 speed and air jacks and a big ass wing.

[steved0x]

Ok here is a 275/40/17 Maxis RC-1, brand new, on a 17x10 wheel, it fits but that red plastic trim tool is 3mm thick and can't clear the gap. I estimate 2mm. I don't know the offset of this wheel but it is pretty tight in there, you could space it out a few mm and gain a little clearance...

Also these are Koni FSD struts, and while they look identical in dimension to OEM, there may be slight differences. Although they do look identical.

I've seen other boxster guys run 275/40/17 back and 255/40/17 front, if you can't get that 275 in there, which would be ideal for rotating tires...

[ike84]

For the oil cooler, look into swapping the OEM one for a 996 model. Larger capacity and should fit without issue. These are oil water coolers and far more efficient than a remote oil air cooler would be.

For the tip, it already has a cooler built in. It too is a water interface so you'll have to plumb it in.

To help, adding a third (center) front radiator is a nice project.

Accusumps are a highly debated. My personal take is they are a band aid at best for a motor that has poor scavenge pump placement, but you can decide. There's lots to read about it in prior posts.

What are your rules about the intake? If you can, gut that garbage and do a short ram intake. I did this on mine, you can find the writeup in the diy section. Also, get rid of the SAI and vacuum resivoir.

A lot of guys have run these cars square in the past with mixed results. In theme of steering I'm not sure you need anything bigger than a 245 at most up front. A 275 square setup will likely slow you down a bit without much if any advantage.

In terms of a tune, we could talk for a long time. Short version of that it will depend on your intake. If you gut the cats and sai, row will avoid error codes but has drawbacks. If you keep your MAF housing the same size you can still run the stock tune no problem, but if you increase diameter here you will need either the Spyder tune or a 996 tune.

Btw. Very nice job on the exhaust. I prefer equal length long runners but the shortys will likely serve you very well. You will definitely need glass packs at the least, unless you dislike your hearing. Trust me here. I ran 2.5 straight pipe for a while but had to wear gun muffs while doing so lol.

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[Endurance Racer]

Originally Posted by steved0x

Ok here is a 275/40/17 Maxis RC-1, brand new, on a 17x10 wheel, it fits but that red plastic trim tool is 3mm thick and can't clear the gap. I estimate 2mm. I don't know the offset of this wheel but it is pretty tight in there, you could space it out a few mm and gain a little clearance...

Also these are Koni FSD struts, and while they look identical in dimension to OEM, there may be slight differences. Although they do look identical.

I've seen other boxster guys run 275/40/17 back and 255/40/17 front, if you can't get that 275 in there, which would be ideal for rotating tires...

Yikes that's close. Thanks for checking....May re think 275s

[Quadcammer]

275 is unnecessary. Running a 17x9 with 245 or 255 front and a 275 rear is probably best for the grip, while a square 255 would likely be best for tire wear. That said, after a few of these events on Hankook RS4s (14 hour and 24 hour), I found them to last for-bloody-ever.

You can likely fit a 997S oil cooler on the car, which is the biggest easily fitted oil cooler.

I'd also run 3 CSF radiators.

[ike84]

Originally Posted by Quadcammer

You can likely fit a 997S oil cooler on the car, which is the biggest easily fitted oil cooler.

I'd also run 3 CSF radiators.

I didn't realize the 997 series oil coolers for on the m96. Any fitment issues that you're aware of? And how much larger are these than the 996 cooler?

Btw, do you see a difference running the csf rads compared to OEM?

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[Quadcammer]

The 997s cooler is maybe another 1.5" taller than the boxster s unit. Its tight to the 2.7/3.2 intake but fits in my experience.

Csf rads definitely reduced my coolant temp vs oem by roughly 10 degrees. Not a huge deal for short de or sprint races but for an endurance car, id want to keep it as cool as possible. I also ditched the drivers side fan

[Endurance Racer]

All

Thanks for the great feedback and information. Let’s discuss further.

Engine cooling: I have removed the drivers side front radiator fan for weight reduction. The passenger side front rad fan remains for times where the car is stopped. Third radiator in the front adds weight that I want to avoid. I plan to use the lower temp thermostat.
Engine compartment is cooled from ducted air from Passenger side air vent.


Engine oil cooler: I will look into the 996/997s cooler. If its bolt in than that’s simple and easy enough. I know oil to water is more efficient than oil (liquid) to air coolers however the delta temperature is greater with oil to air. Assume oil to water would be 235 (oil) to 190 (water) where oil to air would be 235 to 100 (air) temp Assuming hot day and ambient air around the engine like in the trunk. Thoughts on this?

The Tip cooler appear to have a vacuum actuation valve to control the coolant flow. If I’m correct I would like to replace with an electric solenoid valve. As with engine oil cooling, do I go with 996/997s oil to water (will it also swap) or oil to air with greater delta T?

Accusump: Yes lots of debate and info out there. Goal here is to save the engine from high G force oil starvation.. I’m not 100% sold. Per the rules the Accusump is 10 points and a baffled oil pan is 20 points. If I run with the Trans cooler and Engine cooler (anything other than stock) I can only afford the 10 points for the Accusump. So I thought I would try that. Thoughts? Is anything really required?


Tire size: In this series most are running a square 255. I want square for the convenience of rotating tires and can use any spare tire on any corner of the car. Also I want to have balanced grip and be able to get the car to rotate. I’m concerned with larger rear tires (than the front) I will induce too much understeer. Since I can’t change suspension, sway bars, shocks or springs other than aftermarket replacement parts like the Bilstein pro shocks and springs (which I plan to use) I need to achieve balance with tire size and air pressures. And because this is an automatic and acceleration is not as good as the manual, the large wide 275 is to have higher corning grip to have corning speed. Thoughts?

Intake: The intake must remain stock. I can remove parts like the intake resonance air induction valve but that should actually be beneficial to me to boost low rpm response. I will check out your (@Ike84) DYI short ram intake. If it is done without adding parts its possible without points.

Tune: Tune is free. No points so its free HP that I need to take advantage of. Same with at trans tune for the Tip if you know any experts on that. So with stock intake (perhaps your DYI Ram runner), Cats are gone, SAI is gone and my fabricated exhaust with high flow mufflers I need to unlock as much HP as I can.

Exhaust: Thx. I will run with high flow muffler one per side.

Other thoughts? Keep them coming.

[nickshu]

Originally Posted by Endurance Racer

All

Accusump: Yes lots of debate and info out there. Goal here is to save the engine from high G force oil starvation.. I’m not 100% sold. Per the rules the Accusump is 10 points and a baffled oil pan is 20 points. If I run with the Trans cooler and Engine cooler (anything other than stock) I can only afford the 10 points for the Accusump. So I thought I would try that. Thoughts? Is anything really required?

If you decide to go Accusump I have a spare Accusump setup available with custom lines ready to go in the car. Electronic valve. Yours for a great price.

[nickshu]

Originally Posted by Endurance Racer

All

Thanks for the great feedback and information. Let’s discuss further.

Engine cooling: I have removed the drivers side front radiator fan for weight reduction. The passenger side front rad fan remains for times where the car is stopped. Third radiator in the front adds weight that I want to avoid. I plan to use the lower temp thermostat.
Engine compartment is cooled from ducted air from Passenger side air vent.


Engine oil cooler: I will look into the 996/997s cooler. If its bolt in than that’s simple and easy enough. I know oil to water is more efficient than oil (liquid) to air coolers however the delta temperature is greater with oil to air. Assume oil to water would be 235 (oil) to 190 (water) where oil to air would be 235 to 100 (air) temp Assuming hot day and ambient air around the engine like in the trunk. Thoughts on this?

Intake: The intake must remain stock. I can remove parts like the intake resonance air induction valve but that should actually be beneficial to me to boost low rpm response. I will check out your (@Ike84) DYI short ram intake. If it is done without adding parts its possible without points.

Tune: Tune is free. No points so its free HP that I need to take advantage of. Same with at trans tune for the Tip if you know any experts on that. So with stock intake (perhaps your DYI Ram runner), Cats are gone, SAI is gone and my fabricated exhaust with high flow mufflers I need to unlock as much HP as I can.

Exhaust: Thx. I will run with high flow muffler one per side.

Other thoughts? Keep them coming.

Engine Cooling - 100% install the bigger 996/986-S coolant pipes. They literally add almost a gallon of coolant. Get rid of the tiny Boxster lines if you are starting with a Non-S (can't recall). Also add the center radiator. Go with CSF b/c the Porsche/Behr centers are very delicate.

Oil cooler - All I can tell you is I have the 997 oil cooler and have zero oil temp issues even running at altitude.

Intake - If legal wrap it in gold foil for insulation. Pegasus racing sells it, not cheap about $35/foot x24"

Tune - I think many run the Euro tune which I believe ignores the aft O2 sensors so you can delete those.

[Endurance Racer]

Car is progressing well.
My new 17x10 w/ 29 offset wheels fit perfectly. I have a set of RS4 255 on it now for initial testing.
The 275 will come later.
Fender flares will be required. I'm going to roll the fender edge and see how close I get. then I post pics.

The car weighed in at 2321lbs. My goal was under 2400lbs.

[Quadcammer]

holy crap thats light.

Can you share how you got it down that far? Is that with the cage?

[thstone]

Originally Posted by Quadcammer

holy crap thats light.

Can you share how you got it down that far? Is that with the cage?

Remember that a Boxster Spec weighs 2650 lbs with driver and fuel. Without the driver, most are under 2400 lbs.

With that being said, under 2300 lbs is great work!

[Quadcammer]

Originally Posted by thstone

Remember that a Boxster Spec weighs 2650 lbs with driver and fuel. Without the driver, most are under 2400 lbs.

With that being said, under 2300 lbs is great work!

I was figuring the average was a 200lb driver, so 2450. Even at that weight there isn't much left.

I'd love to get my boxster down to 2250, even if it takes a bunch of fiberglass.

[ike84]

Not a 986, but might be an interesting project!

https://www.thedrive.com/news/33330/the-lightest-porsche-911-ever-is-full-of-holes

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[itsnotanova]

Originally Posted by Endurance Racer

Car is progressing well.
My new 17x10 w/ 29 offset wheels fit perfectly. I have a set of RS4 255 on it now for initial testing.
The 275 will come later.
Fender flares will be required. I'm going to roll the fender edge and see how close I get. then I post pics.

The car weighed in at 2321lbs. My goal was under 2400lbs.

That's impressive with a tip! The tip is a heavy pig. maybe double the weight of a 5 speed