Building a Street Prepared Mk1 TT

[madmax199]

Ran the last event at 28/28 hot. HOLY CRAP was there grip. I think I still need to do some tweaking, but I didn't drive particularly well and still PAXed 12th of a field of about 140. I kept turning into cones because the car was responding so much better than I was used to.

http://www.phillyscca.com/solo2/resu...SO062710.shtml (not a bad day )

I'm glad I was able to steer you in the right direction, Ideally you'd want a little less rear pressure than the fronts unless you're trying to promote some rotation with the tire pressure. Try giving 28/26 a try next time and report.

[madmax199]

i spy a go pro camera! did u upload any of ur vidz?

I'll post one up for you sometime this weekend!

[XvwX]

Weekend's over buddy, where's the videos?

[makindue]

I wish I had some info for you so instead I'll just show you my support with a "HELL YEAH BROTHER!!".
Best of luck and PLEASE keep us updated!

Can you post some photos of building Street MK1 TT?

[madmax199]

Weekend's over buddy, where's the videos?

I know, I know, I'm a slacker!

I've been busy getting the racecar at work ready for Watkins Glen Scca's road racing double national and the TT ready for Fingelakes national tour, all this weekend!

Here's one video of the left side at DC, I'm not sure if it's mine or my codriver's:




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[madmax199]

Can you post some photos of building Street MK1 TT?

I did not document all the modifications done while building but I took pictures of a few stuff along the way:


Custom ball joint relocating plates (BJ extenders) with caster offset allowing over -5 degrees of camber





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Custom adapters spacing the wheel/tire combo and also allowing a more available 5x114.3 bolt pattern
(finding wheels wide enough and with the right offset in 5X100 is impossible)





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Custom rear adjustable control arms (I didn't build the arms with heim joints because I also drive it to and from events)


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Home made bumper lip





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Front swaybar modification(reducing the bar rate)





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Final wheel/tire ride height and offset:





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Custom 3" exhaust with single pipe, magnaflow muffler, and exit:





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[madmax199]

Racing season is over and it's time to bump this thread. Last season was a good baseline and I learned a lot about the car, what works and what needs to be improved on.

Based on my observations after a pro and a tour(both placed midpack) I have to face the fact that the TT will never change direction like the miatas (their mechanical grip is just insane) but they can be overpowered as long as you have enough traction to put power down.

I sarted my quest for power by adding a maf based Water Injection kit, it cooled down my IAT to acceptable level and I was able to raise boost to 30 PSI while advancing timing by 4 points safely with 3 M1 nozzles pre and post throttle body(post TB nozzle can be spotted in the TB spacer in the last picture) .

IAT drop from a pull


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Timing graph from a 3rd gear pull on Water only


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Narrow band AFR on open loop WOT


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With the new found power the car woke up but the stock plastic DV was not equipped to handle 30 PSI and was killing spool and made the boost taper too much by redline. I briefly tried a forge 007 DV but the valve was too slow for autocross(recovery time was horrible). I decided to build myself a valve that can hold 35+ psi without leaking and be as fast as stock. The mitsu metal valve found on the evo was a perfect candidate as it's quicker than the 710 and can hold 25 PSI un-modified.

I proceeded to crush the valve's top chamber to preload the springs and increase the holding pressure a few psi. The next modification to the valve consisted of drilling and extrnal reference port and plugging the internal port. All this does is, stop all the boost at the top chamber to push at the bottom of the diaphragm causing it to leak before max boost is achieved. The valve is now capable of holding over 40 PSI(tested) with no leak at all and is still faster in reaction than the 710.



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Next thing to let go was the factory PCV system as it started leaking a the valve even after a brand new valve(just too much pressure in the system for the plastic stock unit). I upgraded to WRX metal valve that is rated at some insane PSI.




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My next move was to convert the car to E85. Simply put you need 630 injectors and an external 255 pump to supply the engine with the needed 30-35% more fuel that E85 requires while keeping injector duty cycle under 80% at all time. A few computer tweaks later, the car was running great with the new fuel and finally feels like it should.

I know some may think it's a bit overkill to run E85 on a car with water injection but going against the miata I'll take everything I can get. E85 allowed me to run another 5 points of timing on top of the 4 points I had advanced with water injection, in addition to the timing AFR was able to be leaned out at least a full point and the result is unbelievable(pulls like a freight train). E85 also burns cooler than gas(about 200 degree F) EGT was so low after the change I was able to afford deleting one of my SMIC and reduce pressure loss afew psi. I can't wait for next season to see what the beast can really do.

I also decided to revise my wheel/tire combo, the old setup was too heavy at 21.5lbs a wheel, so I'm moving to EnkeI RPF1s(17 lbs) and also switching to Hoosiers 295X17 all around. The 295 hoosiers are as wide as the 315 kumho plus they are shorter and lighter, so it's a win/win situation for me.

[vwbora1]

Nice.. Very little hardcore autocross stuff in here. I trophied 3rd at the Wendover Pro against Kotzian and Zacharda in SMF. What crank HP gain do you think you've managed with the meth and E85? I've been contemplating meth, but am very happy with the power/reliability of my K04 setup running 100 octane.

What is the size of your new Enkeis? I am running 285 V710 on Rota Torques:



Thanks!

[madmax199]

Nice.. Very little hardcore autocross stuff in here. I trophied 3rd at the Wendover Pro against Kotzian and Zacharda in SMF. What crank HP gain do you think you've managed with the meth and E85? I've been contemplating meth, but am very happy with the power/reliability of my K04 setup running 100 octane.

What is the size of your new Enkeis? I am running 285 V710 on Rota Torques:



Thanks!

I haven't put the final setup on a dyno yet because the car is getting a new timing belt, water pump and the hydraulic lifters replaced for some peace of mind. With water injection alone I was able to avance timing 4 full points over what 100/110 race fuel could take and bump the boost to 30psi safely so I would say that water/meth is worth a good 30 hp crank.

E85, altough a little more involve, is like Rick James said a "helluvadrug" and I would say gave me at least another 50 crank hp. With it, timing was able to be pushed another 5 points and there is still more room as the fuel just won't knock, even past MBT. E85 burns a lot cooler too and has more exhaust by-products so it also spools the turbo faster and stronger, so to me it's the best fuel you can run legally period. I swear by it now!

The Enkeis are 17X10 but I only have 2 for now. I tought about going to 285X18 like you but decided to stay with 17s because of the weight/price benefits and the gearing advantage that the taller tires offer on the six speed 2nd gear.

What springs rates do you run front/rear and what bars are you using?
It's good to have someone as hardcore with a similar platform to compare notes with.

[vwbora1]

I run off-the-shelf Bilstein PSS9 coilovers, set at full stiff in the rear and about half stiff in the front. Ride height is essentially stock. Rear sway is Neuspeed 28mm (solid), and front is H&R 21mm (smaller than 337 stock 23mm bar). Custom cerealab.com camber plates up front. A/C is gone. Curb is 2700 with the super-heaving Rotas. I wish there was something like a 285/40/18 V710, as I do run out of room at the top of 2nd sometimes. Car makes about 240WHP and 265WTQ with the K04 on 100 (GIAC).

[madmax199]

Usually, the off season is procrastination time for me and I always have to cram everything I needed to do with the cars in one week before the first auto-x. This year is a little different with the TT, I got some work done early. Timing belt, new lifters and some other refreshed parts in the motor.

ForceFed Engineering in NY took care of everything. This shop is the real deal and I've been around the block a few times(from turbo Hondas to DSM and evos) and these guys rock. You'd be lucky to find another shop in the area with that kind of craftmanship and at the same time willing to go above and beyond for customers.
Some of their work can be seen here:

http://store.forcefedengineering.com/default.asp

I'm going to continue to make a push to get as much done during this off season so I can get the car ready early for next year's prosolo that my region is hosting at the Meadowlands(I can' t wait).



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[flyinglizard]

Max,
Amazing work and details.
Maybe over the winter you can start getting this to steer from the rear a little. A very small amount of rear steer will allow you to put down power sooner , by reducing the dynamic loading of the outer tire.
Have fun and keep up the great work. MM

[madmax199]

Max,
Amazing work and details.
Maybe over the winter you can start getting this to steer from the rear a little. A very small amount of rear steer will allow you to put down power sooner , by reducing the dynamic loading of the outer tire.
Have fun and keep up the great work. MM

Thanks buddy,
I am working on it and the car will have a sick rear LSD
on it before the season begins and maybe a competion haldex controller if Santa is nice to me.
Merry Christmas!

[madmax199]

After the E85 conversion, I went ahead and put the car on a DynoDynamics AWD dyno to have a baseline number and have an idea on AFR and the such. It did not go too well and I had to abort after one Dyno run because afr was way out of line and the car was missing( I later found out that it was the spark plugs blowing out at peak load with such high boost)

Beside the whacky AFR and failing plugs, the car made decent power at 360TQ/286HP on a load bearing AWD dyno that reads low; but something had to be done to get the car running like it should.




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I went ahead and changed the plugs and gave them a tighter gap of 22 vs the 25 I had before and it seems to have cured the sputtering mid run.

I also made some ecu modification to cure the AFR curve, I added (with unisetting) 10% more fuel to the primary fuel enrichment to get rid of the lean spot from 3k to 4k. On top of that I removed 85% from the fuel enrichment under accelaration to stop the ecu from adding so much fuel as the revs went up, making the car go almost 4 AFR point by redline.

Another thing that I also took care of was the secondary fuel enrichment (injector reaction time), at 100% it was optimized for stock injectors and since I now run 630cc it needed more enrichment. I set the secondary at 125% for now because that's what the chip companies put in their 630 files and the car seems to have reacted positively to the changes.

The car feels a lot better now with more power and no hesitation at all. The car feels smoother and I gained some mass air flow(I pull 200g/s now from my previous best of 187g/s). The following timing graphs also confirmed my feeling of having more power after the modifications, since the ecu now allow more timing overall with absolutely no correction.

Before

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After



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[madmax199]

Bump for a new season coming up

[Draxus]

When you say ball joint extenders, you mean horizontally outward from the car, yes?

I was picturing vertically, fixing the geometry for lowering.

Am I right on this?

[chads]

Very nice thread. What about brakes? Are you using stock rotors? What pads?

[madmax199]

When you say ball joint extenders, you mean horizontally outward from the car, yes?

I was picturing vertically, fixing the geometry for lowering.

Am I right on this?

Yes you are right, I extended the ball joint location outward and forward horizontally to gain camber and caster.

I could've raised the mounting point also to get the roll center closer to the center of gravity(creating a lower roll couple) and correct any geometry change from lowering. However, that's not legal in street prepared so I only took advantage of what the rule book allowed.

A car in Street Modified or Prepared, could easily replicate what I did and also incorporate some roll center correction.

[madmax199]

Very nice thread. What about brakes? Are you using stock rotors? What pads?

The OEM braking system in the TT, I felt was adequate enough to not warrant the investment of upgrading the calipers.

Rotors are plain Zimmermans(I never had luck with drilled and slotted rotors in racing environment).

Pads are EBC red stuff, they give me a decent cold bite and do not fade or overheat throughout typical autocross runs with two drivers(even in back to back ProSolo format).

In the future, I plan on maybe investing on lighter 2 piece rotors and steel braided lines.

[Ko4TiTy]

Thanks for the suggestions!

My car is the 225 Quattro variant and 3200 Lbs seems to be where the coupes are averaging at , in stock form, so maybe you had 180 FWD. If you have some info on how to get a 225 quattro down to low 3000 lbs while staying SP legal, please share the knowledge.

It's interesting that you are suggesting more bar, is it because of the body roll in the pics?

The car's balance is about perfect now and if anything I would run more springs before I add bars, especially in the rear. The 3 wheeling that the rear bar bring, is not affecting drivability and can be worked around but with AWD you have to wait for that wheel to come back down before you can apply full throttle and that makes the car a tad slower. Maybe you weren't picking up the rear wheels because in a stock prepped car you did not generate the grip that big tires would and the issue was not there Yet.

This picture is stolen from a fellow TT autocrosser (I hope he doesn't mind, right Audiboy) and that's the behavior I'm trying to avoid




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You are right about the brake vs throttle ratio and I have been doing what you are saying for the past two events, gas or brake and no overlap but I wish I could overlap them to keep the turbo spooled and the engine in the powerband.

I dont under stand what is physically preventing you from giving it throttle when u are 3 wheeling,just asking love that pic i have the same car paint , seats an all

[Ko4TiTy]

one more thing lol, i have experimented with 3 wheeling before doing tight controlled circles in a parking lot, it seams my nose has the wright dive angle but the rear wheels have to much travel,what will fix this so i can?, im thinking a 25mm sway bar but ur the scca guy-so u tell me

[DIAF]

one more thing lol, i have experimented with 3 wheeling before doing tight controlled circles in a parking lot, it seams my nose has the wright dive angle but the rear wheels have to much travel,what will fix this so i can?, im thinking a 25mm sway bar but ur the scca guy-so u tell me

If you're three wheeling you need more front spring, as that will keep the nose from diving. Definitely don't try to reduce wheel travel.

[madmax199]

I dont under stand what is physically preventing you from giving it throttle when u are 3 wheeling,just asking love that pic i have the same car paint , seats an all

A few things are in play, when you lift that inside rear wheel off the ground.
The main reason you can't apply any significant throttle is beacuse it will result in major understeer and the car plowing out of line.

When you're making a turn whith all 4 tires on the ground, even with weight transfer, that inside rear is still carrying some weight and the rear swaybar is still effective. As soon as that wheel lift, all the weight on that corner is instantly transfered to the already strugling outside front tire. Adding throttle or steering to that situation just make things worse and all you can do is be patient and wait for some load to be transfered back to the rear before you can get back on the gas. Another problem with tripoding is that the rear swaybar is no longer effective, and by loosing some of your rear wheel rate you also unload some of the available weight on the inside front(making it hard to avoid wheel spin without a lsd).

[madmax199]

If you're three wheeling you need more front spring, as that will keep the nose from diving. Definitely don't try to reduce wheel travel.

Agreed, but up to a point. You could also have too much front roll stiffness and that could also cause understeer by overloading the outside edge of the front tires (don't ask me how I know).

So, yes more front springs help reduce the tripod until you reach Natural Frequencies that are too high for the tires to handle.

[madmax199]

one more thing lol, i have experimented with 3 wheeling before doing tight controlled circles in a parking lot, it seams my nose has the wright dive angle but the rear wheels have to much travel,what will fix this so i can?, im thinking a 25mm sway bar but ur the scca guy-so u tell me

The biggest mistake you can make is to introduce a stiffer rear swaybar. It is in most cases, the main reason for the tripod and I'll explain. The rear bar act as a lever and uses some of the available grip on one side to help the other. However, the bar by the way it works, also have a jacking effect that contributes to the inside wheel coming off the ground when weight is transfered. If you read through the thread, you'll see that at some point I ran without a swaybar so I could eliminate that effect and rely on the springs only to control rear body roll. It was succesfull at eliminating wheel lift but due to the motion ratio in the back(around 0.65) I'd have to run super stiff springs and that creates other problems. I have the stock rear bar with 1300lbs springs now and wheel lift doesn't start until after 1.2g at steady state.

All 4 wheels on the ground at 1.2G left hander


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Before the right springs and stock swaybar, on the same 1.2g turn


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[Sead]

I could've raised the mounting point also to get the roll center closer to the center of gravity(creating a lower roll couple) and correct any geometry change from lowering. However, that's not legal in street prepared so I only took advantage of what the rule book allowed.

A car in Street Modified or Prepared, could easily replicate what I did and also incorporate some roll center correction.

This is no longer the case. One of the fastrack updates last year changed this for SP.

[madmax199]

This is no longer the case. One of the fastrack updates last year changed this for SP.

That's some good news, I'm going to look into it! I usually read the fastracks but I must have missed it. Thanks Sead .

[madmax199]

This is no longer the case. One of the fastrack updates last year changed this for SP.

I have looked into it extensively and opted to keep it the way it is, for now.

Raising the roll center with the BJ (mounting point to pivot point lenghtening) is easy but I have no way to lower the tie rod ends the same amount legally. If I don't drop the tie rods as much as the control arms, I will be introducing some unwanted bump steer that IMO not a good idea. Thoughts?

[rex_racer]

The way I and a few others read it, it allows for control arm extensions in the spirit of increasing camber, not for changing the roll center. Perhaps we should reexamine the rule a bit closer.

[madmax199]

The way I and a few others read it, it allows for control arm extensions in the spirit of increasing camber, not for changing the roll center. Perhaps we should reexamine the rule a bit closer.

That's the way I interpreted the rule myself until Sead introduced the idea that roll center corrections was feasible within the allowances.

[rex_racer]

Would you mind explaining his viewpoint? As far as I saw, it said lateral adjustments were ok, ie side to side, not vertical adjustments.

[madmax199]

Rex, he's seeing it as with the fastrack update, our bolted ball joint is un-restricted/open as long as 3 criteria are met:
1) It bolts into the OEM mounting points
2) It's not used in conjonction with upper camber compensation ( you can use either upper or lower both not both)
3) The BJ lenghtening is not an add on extender

So a custom made longer BJ, altering the pivot location in relation to the knuckle, is kosher but you still would have to deal with the bump steer introduced by not having a legal way to modify the tie rods location.

[madmax199]

Finally I have an SCCA SP legal solution for the forward bushings on the MKIV front control arms and guess what they are even better performing than anything else to date(even Defcons and pre-recalls control arms).

Well, Mike Phillips (president of MCPI) and I got together after my dissapointments that no legal solution was available for the SCCA guys. The SP rules does not allow rubber to be replaced by metal and that made the Defcons not an option except in Prepared (unlimited suspension allowances).

The solution Mike came up with is a full solid Delrin split bushing with a metal insert that's not only legal for the racers but also improve the car's behavior a lot more than the original Defcons. There is no more bushing deflection and the steering response is instant. These things does to the Defcons what the Defcons did to the OEM recalled set up. They have been on my car for a little while now and they are awesome, I have a big everyday. I find myself looking for reasons to turn because it's so enjoyable, compared to before. The steering and transition improvement these make is simply amazing, even to me (I can't wait to autocross them on fresh Hoosiers, the miata slayer has a new weapon ).

The engineering is great (internal grooves for greasing, chamfered leading edges for ease of pressing them in). I am not sure what pricing is going to be but they are well worth the investment if you're looking for a real track worthy performance improvement. Mike should have all the details posted on the website shortly.



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[rex_racer]

I was thinking the same thing, but then they added this additional statement:

Street Prepared: Per the SPAC, add as a new 6th sentence of 15.8.H.4 as follows: “A non-standard ball joint which is present in a compliant camber kit replacement control arm is permitted to offset from stock the spindle mounting location from the control arm plane.” (ref. #3355)

The control arm plane is horizontal so the ball joint adjustment would have to be lateral, there is nothing that says you can make a vertical adjustment, or did I miss it. And like all else in the book, if it doesn't say you can, you can't.

Nice job on the Delrin front control arm bushings, I have been wanting to do that for some time now, but was worried about how the bushing would wear when the rear bushing can still flex and squish into other directions and thus cause an extra side load to the Delrin front bushing and cause premature wear. Prolly not as much an issue on a dedicated autox car, but since I daily drive mine, I don't change that rear bushing as often as I should haha. Keep us posted on how the Delrin front bushing works out, looks promising!

[Sead]

Any thoughts to offsetting that bushing to gain more caster?