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Building a Street Prepared Mk1 TT

49K views 143 replies 30 participants last post by  topemu 
#1 · (Edited)
The Car:
- 01 TT quattro

Suspension:
- 17X10 5zigen fn01rc
- 315 v710 front, 275's rear
- Revalved H&R RSS (listed for R32) with custom spring rates
- Home made front ball joint extenders with caster offset (allows me to run up to 8 degrees of camber)
- Modified stock front swaybar with about half the stock rate and stock rear swaybar
- Madmax rearadjustable control arms

Engine:
- 42 Draft Design intake (with velocity stack and heat shield)
- Larger S4 maf housing with stock sensor and 3 bar of fuel pressure
- Generic ECU chip
- Wastegate actuator modified with 2 external 5lbs springs
- Converted to E85 ethanol
- Custom 3" turbo back exhaust with 42 Draft Designs downpipe
- Labonte Maf controlled Water injection kit(running straight distilled water via 4 M1 nozzles pre and post throttle body)
- 630cc injectors, 255 external fuel pump
-Timing advanced +13.5* on top of base flash
-Mitsubishi Evo modified metal recirculating valve
-SMIC delete(with low iat coming from water injection, two SMIC were redundant and an auto-x car could use some faster spool by reducing pressure loss)


Other:
- Slightly massaged front fenders for tire clearance
- 4 point harness
- Home made front lip
- 15 lbs DEKA battery

Future mods:
-Put the car on a diet with lighter seats/brackets, etc.
-LSDs and maybe a competition haldex controller if proven legal in street prepared(I'm sending a letter to clarify legality)
-Passenger side facing Extrude honed IM with 70mm TB so I can reduce the amount of piping by half.

The mission:
Build a competitive street prepared TT for next year when the car is likely going to be moved from CSP:screwy: to DSP:).

The car as of right now is in the beginning of it's R&D and has plenty of things that need to be improved.
A few guys I know, are either building for street prepared or have an SM TT that could share some setup info so I'm starting this thread so we have a place to do so. I'm sure some here would also have some ideas and input that will be welcomed.

After 2 autocrosses the car corners flat and rotates nicely and doesn't understeer unless driver induced.
My issue right now is that the car shuts power down when brake and throttle overlap(left foot braking) and it's killing my times, so if anyone dealt with that on newer VW or Audi what did you come up with?




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#4 ·
I think the TT will dominate DSP.


I'm interested in your tire selection. You have the 6 speed, so your gearing was different than mine, but where are those tires putting the top of second for you? For me, I wanted the shorter 285/30/18's as they were taller than the "almost-tall-enough 275/35/15's", but also in a more wallet friendly V710 vs. A6.

This was my car:



I'd be tempted to build a TT225 for DSP with how much fun my GTI was.

Where in NY are you running? If you're running out on Long Island, come out to some NNJR events.
 
#5 ·
I'm in long island, and now that NNJR is trying to be at the meadowlands I'll be coming to their events but the Englishtown is kind of a stretch with all the traffic!

I choosed the taller 315/17 over the 285/18 because of the gearing that becomes problematic in the faster national tour type of events. I haven't calculated what my top of second gear speed is with the 25.4" tall 315 but I'll take every extra mph I can get!
 
#6 ·
I'm wondering why you started with a convertible? Maybe you already had it?

Anyways, I think you're off to a great start. What are your spring rates?
You should also consider either a Haldex orange controller, or a custom solution. Wait...is that SP legal?

F/R LSD's make a huge difference in the overall behavior of the car, so if your wallet allows that, I would wait to mess around with the suspension till the driveline is finished.
 
#7 ·
The biggest enemy of the TT is weight, so I would start looking at how to shed some. If you can make a quick disconnect for the exhaust, right behind the driver, that should help some in the lightening department and free up a few ponies as well.
What sort of downpipe do you use? Why just a generic chip and how does it behave? There is good power to be extracted from the Ko4, but it has a habit of being very peaky. So look for a solution that gives a relatively smooth boost delivery but a high hp.

Last I remember putting on 10 inch wheels, they weren't offset that far out. Is there any more room inside the fender?
 
#9 · (Edited)
The car is actually my wife's TT, I already have an XP evo an EP saturn but one day I just decided that it would make a cool Street Prepared car!

A rear LSD and Haldex controller is in my list of mods but not on this season's budget, maybe I should edit the original post and add a to do list.

My spring rates are:
685lbs front with a wheel rate of 657.87lbs/in (modified front bar)
1150lbs rear with a wheel rate of 645.38lbs/in (no rear bar)

Edit: I opted to bring the stock rear swaybar into the equation in an attempt to get a little more rear wheel rate(I am still not getting any rear lift with the stock bar)
 
#10 · (Edited)
The car is sitting at 3200lbs right now, the exhaust is pretty light with a straight 3" pipe and a muffler. The bulk of the weight reduction is going to come from the seats and a light battery, that would save me about a 100lbs and put the car at 3100lbs.

The generic tune came with the car and I plan on advancing the timing map in the near future to match the race fuel I run.
 
#11 · (Edited)
CC GTI, what makes the haldex controller not legal in SP?

The offset is +10 on the wheels in the first picture, I since pushed the rear wheels inboard since there was plenty of room. The front however have 2mm of room between the tires and the coilovers and maybe more with less negative camber.



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#12 ·
Its not legal because there is no place in the rules that say you can add the controller. I believe the controller would bump you to SSM.
I ask about the offset on the wheels because it look like you are having the same issue that DIAF and I were have when setting up the GTi. I wonder how big the shock bodies are on your coilovers. We originally were use Teins and had to have some crazy spacers machined to get the wheels to fit. After more research we found that going to Koni Yellow with GC coilover kit gave us more room to pull the wheel in closer helping bump steer. We also used camber plates as our *one* adjustment and did not go the route of the of the LCA adjusters.
 
#13 ·
The shock body is not big at all and even if it was smaller it would have to be like a pencil in diameter to allow you to effectively bring that front wheel in-ward another inch.

I don't know if your closest point between the tire and the shock is the collar or the actual body but I had to run shorter springs to move the collars above tire height, so you could check that too. I just see it as one of the design flaws of the chassis and work around the potential bump steer!

I stayed away from the camber plates and fabricated my own BJ exenters because they didn't offer enough adjustement to justify the $400 investement. I don't know about the GTI but the TT need way more than 3" of negative camber according to pyrometer.
 
#14 ·
The Konis are identical to the stock shocks in size, and there's a part that's inset to allow for more clearance. It was worth 3/4 of an inch or so for us.

Just something to look into. If you still have the stock struts around, throw one in and see how much more clearance there is, that's how much you'd gain by going to konis/GC.

Perhaps a bigger benefit than bump steer is the narrower track and reduced steering input effort.
 
#15 · (Edited)
I did the six speed TT gear ratio to mph calculations for the 3 most likely ran R-compound sizes on the car. Since that kind of info was not available anywhere when I was looking for it, i'll post it for future references.

The TT has a final drive of 3.32:1 and second gear ratio is at 2.11:1 so on top of second gear:

25.4"▼▼ (275/17 or 315/17) ----- 24.8"▼▼(285/18)
RPM ------------(MPH) ----------- RPM----------- (MPH)
8000 rpm 86.30 mph -------- 8000 rpm 84.26 mph
7500 rpm 80.90 mph -------- 7500 rpm 78.99 mph
7000 rpm 75.51 mph -------- 7000 rpm 73.73 mph
6500 rpm 70.12 mph -------- 6500 rpm 68.46 mph
6000 rpm 64.72 mph ------ 6000 rpm 63.19 mph
5500 rpm 59.33 mph ------- 5500 rpm 57.93 mph
5000 rpm 53.93 mph ------- 5000 rpm 52.66 mph
4500 rpm 48.54 mph ------- 4500 rpm 47.39 mph
4000 rpm 43.15 mph ------- 4000 rpm 42.13 mph
3500 rpm 37.75 mph ------- 3500 rpm 36.86 mph
3000 rpm 32.36 mph ------- 3000 rpm 31.60 mph
2500 rpm 26.97 mph ------- 2500 rpm 26.33 mph
2000 rpm 21.57 mph ------- 2000 rpm 21.06 mph

Keep in mind that the TT redlines at 6600 rpm in stock form and the motor runs out of breath past
5900 rpm.
 
#16 ·
I did my 3rd event with the car last weekend and was pretty happy with the outcome, we gave a nationally prepped GT3 with good drivers and fresh A6 a run for their money while still on very old v710.
They beat us, don't get me wrong and got FTD but in their own words "that little TT really husled"

You could tell that the GT3 was pulling much harder in the few power section of the course but was not outhandling us, so I need to loose some weight and get more power.



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The GT3 that got us!
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#17 ·
Nice setup. :thumbup:

I wish I read this thread before I went through all the trouble to figure out wheel rates on my RSS's on my R32 :banghead:

I don't know about you, but I personally think that our chassis could benefit from a tad more rear rate (assuming you are leaving your front bar connected).
 
#19 ·
You are right that the chassis would've benefited from a little more rear rate but a rear swaybar even stock would be too much IMO and make the car tripod(you don't want that with awd).

The other option would be to add more rear spring but the rear natural frequency right now is almost at 3hz and raising it would make bumpy turns problematic, so I made the decision to leave it as is for now. I tried the no front bar approach but transitions suffered a little so I modified the stock front bar to cut the rate significantly and I'm happy with the balance.

I am currently at the dc prosolo and the chassis will have a real test tomorrow and I will report my findings!
 
#23 ·
Anything that can make the car faster legally is going to have my interest but I'm not sure how the system works and if it applies to the TT's suspension design. Can you give us more details, and you also mentioned something about twist beams can you clarify?
 
#22 ·
I wasnt kidding about the rear steer.
You will pick up a cleaner turn in using the DRS. It is legal in SCCA and a definite improvement over the firm rear axle placement. I have about 20 cars using it now and none will go back to the old way. Email me and Igive you some details.
The best 20$ you can spend on a VW race car.
 
#24 · (Edited)
After a long and hot weekend we put the car in the trophies in CSP at the DC prosolo and that makes me happy although it's my co-driver's accomplishment.

I sucked at life this weekend and coned or redlighted all my potentially good runs.

We had some issues with the driver's side front tire rubbing where the fender attaches to the bumper but took care of it while staging with a breaker bar. Our 710n diverter valve also failed and is honking like crazy now, it made the car sluggish all weekend but we had no choice but to continue with it since the closest dealer with one in stock was a little out of the way.

The car performed surprisingly well against the stiff competition of the miatas and was also the the fastest non miata(an Mr2 and an Rx7) of a healthy class of 12.
We were pulling high ones in the sixty foot, while the rest of the class was averaging mid twos(as a reference, SM evos with two steps launch control were doing mid ones at the sixty foot mark)

Overall I am satisfied with the result for a car with only 4 events under it's belt and limited prep. I will post some pictures and videos later because I am shot after the 6 hour drive and lots of traffic.
 
#25 · (Edited)
Here are a couple of pictures of the car at the pro in DC, I edited them to remove most of the shadows for photo analysis.
The pictures reveals a few things:
1)The car is not too stiff and still has some healthy roll, so the suspension is working
2)The high static camber is justified as you can see that when fully loaded the camber goes a hair positive
3)The car does not tripod and that makes me happy because I worked really hard to make that happen(according to my suspension simulation I would pick up a front wheel first with the setup)
4) I need to up my tire pressure all around by a few pound(I was running 23/20 front to rear and it looks like it is too low)

Maybe there are things that I'm missing so I'm open for inputs!





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#26 ·
I didn't know you could run the tires that low without problems. I have a mk4 gti with the setup that DIAF had above with the red wheels (bought it off him). I've been running 35lbs all around and wondering if that's too high. Thoughts? I'm wondering if dropping to 30ish might be a good idea.
 
#27 ·
IMO that's too high, try 28/25 front to rear and report your findings! :thumbup:

My ideal pressure in the TT is 25/23 cold targetting 30/25 hot, since your car is a bit lighter and run less tire I would start at the 28/25 and remember V710 loves heat(200 degrees operating range) and pressure builds quickly at those temps so I would start bleeding at 30/27 hot in your car. Take my advice(or anyone else's for that matter) with a grain of salt and do some experimentation with the suggestion to find what's right for the car:beer:.
 
#28 ·
Interesting car!

reading through the thread i was like WOW that's heavy. my stock car was 3070 when i was running the straight exhaust, but i see your the convertible so your've got that uphill battle to deal with.

I guess i come from a more stock class setup, but it sure LOOKS like you need some bars from the picture...in stock class i ran one year on Canadian rules which allowed rear bars and the car came alive! i ran a 25mm rear on full stiff and the car was nuts! never had an issue with the 3 wheeling effecting the drivability. The only 3 wheeling issues i had is when i was on the concrete in Peru and i was able to lift the front tire but never an issue with the rear. Then i switched to US rules and put the stock rear in and put a 25 full stiff in the front and loved it again.

As for the brake and gas thing it just takes a while to get used to it. Use lift oversteer instead of trail braking and if you trail brake in a bit just be aware that your right foot can't be touching the pedal at all. This is assuming you left foot brake which i did successfully for 3 years when i campaigned my TT, and the previous 2 with my Jetta. You just have to keep practicing.

Anyway, cool car man. Drop the exhaust though! saves like 50+lbs
 
#30 · (Edited)
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:banghead:.
 
#31 ·
Other chips might do this as well, but I believe that there's a delay on the 'immediate power cut if both pedals are pressed' with Unitronic. I don't left foot brake (yet), but I've played with it some, and it does not cut throttle immediately. Give them a call, they tend to be really responsive over the phone.
 
#32 ·
After doing a little bit of research on the subject I had found out that the issue is in fact standard on all newer Audis with drive by wire and it's called "Brake Overide System":screwy:; it's kind of a failsafe to prevent run away cars like Toyota had recently. Maybe it's not standard on the VWs and you also had to have a certain percentage of brake/throttle overlap to engage it.
 
#40 ·
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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