986 Boxster ChampCar Endurance racing build
 

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.


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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

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

Looking forward to seeing your build!

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.

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...

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

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.

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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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

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.

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.

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.

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.http://986forum.com/forums/uploads02...1647729054.jpg

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!

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.

Not a 986, but might be an interesting project!

https://www.thedrive.com/news/33330/the-lightest-porsche-911-ever-is-full-of-holeshttps://uploads.tapatalk-cdn.com/202...54a2457ee9.jpg

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

Yes with cage, race ready all fluids and a few gallons of gas. No driver.
All panels (doors, hood, truck lid are lighten to a single outer skin.
Doors are bolted on no hinges, No trunk and hood latches - using aero pins
interior is completely striped no HVAC, dash, hand brake etc
No head lights but it does have the windshield wipers
Roof is alum sheet
Windshield is polycarb
Remove battery and battery tray replace with Braille li battery and alum mount.
There is more to remove in undercoating and wiring.
Look through the pics and see the weight reduction on just about every component

We did our shake down run at Chin HPDE at WGI
Overall it went well.
Best laps time is 2:20 We were targeting 2:12 so we have some work to do.
Compared to our 3.0L 944 the Boxster corner speed is similar but just not getting straightaway speed of the 944
We were on RS4 - 255 square.
May need wider stickier tires. But must run a 200 tread ware tire.
Water temps were good
Max engine oil temp was 230
Max trans oil temp was 215-230
The tiptronics was not horrible. We chose to let it upshift and we manually selected the downshift.
Overall I'm pleased but concerned about finding at least another 5 to 7 seconds

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I think you will run faster on straightaways with a staggered setup, 225 or 245 (at most up front)

The only other thing you can do to help is the intake, which sounds like you're pretty much stuck with. I would find any way possible within your rules to make modifications here. Even if not adding parts, "substituting" the existing layout with larger diameter components. I really think 82mm is a magic number here, from TB to MAF housing to airbox. This will need a 996 tune to with but it will help (I'm so sure that I'll bet $ on it)

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Also, do you run with the top like that? If so, you may want to try adding vortex generators in different positions and seeing if that helps. You're gonna have a really dirty breakaway on the back of that roof which can show you down considerably in straightaways.

Just for my own curiosity's sake, what did you do with the windshield? Did you completely remove the OEM A pillar?

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ike84 thanks for the input. The windshield is replaced with polycarb and the "A" pillars are cut away for the most part. I left only the body sheet metal for the poly carb windshield and half the A pillar support.
And yes the top is just an Alum sheet. The air all around the the cage and everything is going to very dirty.

Sounds like a fun project. A few thoughts:

Endurance racing is all about keeping the wheels turning. Lap times matter but avoiding breakdowns, car contact, and black flag stops matter more. We run Lemons in a 4 car Miata team with 4 drivers each. In the last race of 2021 my car was probably the slowest in terms of best lap time but... we drove pretty clean, avoided contact, and had zero breakdowns. As a result we were the top finisher on our team.

What I would do:

- Make absolutely sure the cooling is dialed in so she will not overheat.
- Add an under drive pulley to protect the power steering pump and add cooling fins to the PS lines.
- You are probably committed at this point but I would choose a baffled pan and take the points vs the accusump. Not a fan of those and have seen too many failures.
- Run 255/40/17 square on 8.5 inch tires for better acceleration and lighter unsprung weight. I think 275 on 10" wheels is too much wheel/tire for limited HP. I think 255s will turn faster laps.
- Run the new Bridgestone RE71RS for 1-2 sec faster laps than RS-4s
- Make any changes possible to increase negative camber. Stock negative camber will eat the outer shoulders on 255s. If you can get -3* up front -2.5* rear you will double tire life and use all of your available contact patch.

I see no need to change anything with the motor unless you want to run ROW and eliminate the rear O2 sensors. She will be most reliable in stock form.

Best of luck in this adventure. Low budget endurance racing is super fun!

Cool! Our Lemons car is also Red White and Blue livery.

Race results: Saturday was a 7 hour endurance race. It started in the rain and was rainy for the first 5 hours. It started to dry only for the last 2 hours.
Sahlens won with a fast lap of 2:12.6 in their Boxster.
Our team did well with the 944's finishing 2nd, 5th and the Boxster 18th. We started dead last in the field of 85 cars. (start position is determined by a random draw) The Boxster is not at a competitive pace.
I'm not sure if this is all due to the automatic or potentially sick 97,000 mile motor or gearing.

Sunday 7hours was sunny and dry. but the racing luck (bad) bit us. We started on pole (reverse order from Saturday) see pic of our cars 3 wide on the front straight at the start. At about the halfway point our sister 944 car went off in the bus stop punctured the oil pan, unknown to the driver, was loosing oil and the driver went back on the track into the carousal T5. Our Boxster was the next car thru T5 and lost it in the oil and hit the guard rail on the outside. So we have damage repair work in addition to trying to make the car faster. We will be back....

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I hate it when bad stuff happens but that is racing. Some days are clean with no contact or breakdowns, other days, not so much. I have several friends in the GT-4 America series. One team took their 1st class win while the other got punted at the start and took DNF.

https://www.gt4-america.com/results?filter_season_id=7&filter_meeting_id=73&fi lter_race_id=357

I'm only getting 115mph on the straight before the bus stop. The 944 are at 128.
And I'm at 6200 rpm so I think my gearing is too tall.
So I would like to change the final ratio (lower, high numerically). Does any one know of a source for a ring and pinion for the ZF5HP19 Tip?
Or what Audi or VW ZF5HP19 with lower final drive will swap into the 2.7L Boxster?
If I change the final ratio I think I also need to re-calibrate the TCU trans speed sensor as it will not agree with the wheel speed sensor input and that could cause issues. I think.
Any one know for sure?

Or 5 speed are swappable with the 012 5 speeds in fwd a4s from the late 90s. Not sure when the generation ended but that transmission was first used by audi starting in the 90s. I would look at any model from that period with fwd and it will likely match up. I don't remember for sure but I think that they do have a taller final drive. Don't quote me on that though.

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Did you do a custom wiring harness for the car or were you able to move the harness from the left side to the center?

Using the stock wire harness. Thinned out a little for the things not required but much more can be done. Relocated to run down the center including the fuss panel and relays all moved to the center.

I've converted the car to a manual 5 speed. At this point couldn't find a way to get a lower gear ratio. Found a stand alone tip tune but would require lots of development. So I converted it to a manual.
Next race in TMP Labor Day - 12 hours

I'm curious... Not counting gathering parts, was the tip to manual swap straightforward/bolt-in? I have stripped a couple manual cars and probably have the parts. Are all the holes and mounting points for the manual stuff already there?

Have you looked at the aero with it open on the sides and rear? Seems like it would make a lot of turbulence (drag) at 70+ mph. I think that extending the sheeting of the roof further back (even shooting brake style) or putting a gurney flap at the back of the roof might reduce the drag at speed, but I'm just guessing.

The tip to manual is fairly straight forward if you have all the bolt in parts.
The DME is common but the software is not. The Tip wire harness works, but you need to add a pin D1 to ground or add the clutch switch.


As far as drag well yes but extending panels adds points for material used that I can't afford. Its on an even playing field as all the cars run without widows and such and thus have drag (wind resistance) going thru the roll cage, B and C pillars on hard tops

I've been battling a P0336 code. RPM Circuit error.
Its kept me from 2 race events.

This is a 2003 2.7L 3 chain engine


I have verified the mechanical timing with the cam timing tool - The cams and crank are properly in sync.
The crank sensor is good. And a second sensor was tried and tested.
The wiring harness from sensor to DME is good
I can see engine RPM on the scan tool.

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per Porsche diagnostics.
The DME (ECM) is bad.

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Does anyone have a DME for a 2003 manual trans Boxster I could try to test?
Or a good source for the DME to purchase used?

I have a DME-Immobilizer set from a 2004 2.7L Tiptronic that I can loan you if that helps. I am open to selling it if it works for you.