986 Boxster ChampCar Endurance racing build

[Endurance Racer]

Originally Posted by Quadcammer

holy crap thats light.

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

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

[Endurance Racer]

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

[ike84]

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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[ike84]

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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[Endurance Racer]

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.

[Topless]

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!

[Endurance Racer]

[Topless]

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

[Endurance Racer]

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....

[Topless]

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&filter_race_id=357

[Endurance Racer]

[Endurance Racer]

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?

[ike84]

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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[subieworx]

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?

[Endurance Racer]

Originally Posted by subieworx

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.

[Endurance Racer]

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

[78F350]

Originally Posted by Endurance Racer

I've converted the car to a manual 5 speed. At this point couldn't find a way to get a lower gear ratio. ...

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.

[Endurance Racer]

Originally Posted by 78F350

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

[Endurance Racer]

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.




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



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?

[78F350]

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.