Hello....

Im looking into the Stage II upgrades for my 96 993TT.

One question I have are the discussions around the GT-1 Turbo's verses the GT-2 Turbo's. What should I go with? I will be doing mostly Street running and not track...with the wonderful 91 octane gas we have in Reno.

Here is the line up for now..

FabSpeed Max Flow (Already Installed)
RS Clutch, Flywheel Upgrades (Already Installed)

Next Installs:

RennSport or Carnewal ECU - Stage II
GT1 or GT2 Turbos' (?)
GT Oil Cooler
FVD IC
5 bar FPR

Any thoughts on this config? Can I get 480hp with 91 octain with this setup?

Thanks for all the help on this list!!

Rich

 

Rich;

From doing both conversions, GT1 vs GT2 K24's, the GT1 hybrids are the way for a street 993. When upgrading to the larger K24 the 2mm larger turbine wheel does impact you bottem end torque curve. Now if you have no Cats, or different camshafts, the K24 will be the next choice. Depending on how your ECU is programmed you can obtain that 500hp mark.

 

For the street, where most usage is 2,000-4,000 rpm at partial throttle I really don't think any of the current TT upgrades would really help much? Bigger exhausts, larger turbos, bigger pipes, bigger intercoolers are all going to hurt the performance under typical street conditions.

What do you think of the flywheel and clutch? - Do you hear gear rattle? Is the engine revving significantly different? How has street driving been for you?

I am currently still stock, but I do mainly street/highway driving and I don't want to negatively affect the nice smooth balance the car currently has. (And it gets expensive upgrading!)

 

Hi Andy...

There is a big change in how I drive with the new flywheel. Pulling from a stop requires some changes from before, and I often kill the car in reverse! I also noticed that at slow speeds in traffic the car get "Jerky"...But not enough to complain. No gear chatter that I have heard so far.

Hope this helps...

Rich

 

Some changes are clearly worthwhile and will enhance rather than hurt street performance. My car has headers (installed when I bought it--not sure they do anything), "racing" cats (similar to cat bypass), max-flo mufflers and a Turbo S ECU upgrade from Steve at Rennsport. I don't have nearly enough hands on experience to say how this relatively mild set-up compares to others (its just where the car stands right now while I decide if I need more power), but I can say that the difference from stock is very evident--BETTER low-end and midrange response and better power on-boost than stock. The free-flow cats seem to allow the turbos to spool earlier and quicker, and Steve's reprogram of the ECU results in the boost coming in much stronger and staying stronger. Much better sound than the stock "nuclear vacuum cleaner" effect as well, but in no way obnoxious.

By the way, has anybody found an aftermarket air-cleaner set up for the 993TT that makes a noticeable difference?

 

Andy;

I invite you to come down to see me and I will install any of the upgrades that you mentioned. Whenever you reduce the backpressure on our turbo motors you will get a noticable gain in performance. This gain is usable horsepower, you will notice in you butt meter.

 

I had an AWD Eagle Talon a few years ago that I managed to squeeze 350hp from - headers, ecu, vpc, evc, injectors, big exhaust, no cat, larger intercooler, big turbo etc... Sure on full throttle it was amazing, but the low/mid performance made it a much worse street driver, also the car was so peaky it became really tiring to drive after a while.

Some amount of backpressure is required to have better low end torque. Street driving is done at small / partial throttle - dyno charts don't show the losses you will experience with the small air flows through larger diameter components. Most of the additional equipment will increase peak HP and maybe then only at full throttle, max boost or hi revs. (There are some exceptions, like a well designed header can improve low end torque and hi-end power). I am really interested in which mods help the street driving most.

If only it were possible to measure partial throttle response better....

 

Andy,

What you say is true for the bigger GT2 Turbos. However, the GT1 street Turbos don't loose anything on the bottom end. Coupled with a FVD ECU or a re-mapped ECU by Steve at Rennsport Systems, you will gain a ton of bottom-end torque.

My experience with Race CATS is that they are not worth the money. I gave Steve at Rennsport my Racing CATs and the stock CATS to be measured on a flow-bench and the numbers were exactly the same.

However, replacing the CATS with CAT bypass pipes makes a huge difference.

Rick
<a href="http://www.993tt.com" target="_blank">www.993tt.com</a>

 

Rick, I agree with you re the aftermarket cats typically sold as "sport" or "race", 100-cell or 200-cell cats--I tried the cargraphic variety on my car and noticed no real difference, including no real sound increase/improvement. I gave them back to the shop that sold them to me and the guy went in the back and came out with the cats I now have, which he said were used one-off on a GT2 Evo race car that he ran in the Supercar race in Macau when they required cats one year. These made a huge difference in performance and sound, which leads me to believe (and my guy just smiled when I asked him) that they are little more than bypasses masquerading as cats.

 

Any thoughts or feedback on the RUF Turbo's?

Great feedback so far!! Thanks...Rich

 

Rich,

Steve's ECU combined with the GT1 Street Turbos is a killer combination, and produces greater power over the entire RPM range.

I'm sure the RUF turbos are fine, but I like to deal with someone that I can get a hold of quickly in case of problems.

Add bypass pipes and that car will scream.

Rick
<a href="http://www.993tt.com" target="_blank">www.993tt.com</a>

 

Hi Joe,

Yeah, I was really surprised when I had the racing CATS put on the car. The sound was a little better, and it only produced a minimum HP gain. These were the FVD CATS I tried.

Rick
<a href="http://www.993tt.com" target="_blank">www.993tt.com</a>

 

[quote]Any thoughts on this config? Can I get 480hp with 91 octain with this setup?

<hr></blockquote>
Rich, I am by no means an expert on this, but my car is set up similarly to what you are describing. (FVD ECU, hybrid turbos, mufflers, LWF, Andial Intercooler, S-oil cooler, short shifter, sport motor mounts, bilstein suspension, Fikse FM-10's)
I believe that you are going to have to get your octane up to 93-94 to see your 480 HP.
I had to fill up with 91 a couple of weeks in a row and my car went down on power as the computer adjusted itself. My mechanic (Mike Schatz) recommended I un-hook the battery for 15 minutes and then re-attach it so the ECU would re-learn the higher octane. I mix 4 gallons of 103 octane at every fill up religeously now. All the power seems to be back. In a hot climate, I'm told that you can lose a huge amount of power on these cars running 91 octane in a stock setup.
Again, I'm an enthusiastic amature and have no dyno readings to prove this. I'm just relaying information from a trusted mechanic.

 

Scott, where did you get the short shift kit? Does it make a worthwhile difference?

 

Joe, The car came set up this way, so I'd have to go rummage though the file of receipts to give you a definitive answer. I believe the short shifter is a factory unit. I love it compared to the stock shifter. Very smooth and light. It compares favorably to the short shifter in my Audi S-4 in that it is not notchy and high effort.