Bull993tt

Sorry for the redundancy, but I have a '96 993 tt with "Powerchip's" software upgrade. A technician from Powerchip by the name of Jessie did the software download while the car was on the dyno at "Turbo Performance Center" in Jessup, Maryland. It has stock turbos, cats, exhaust, and intercooler. The tt's stock dyno came in at 327 HP at the rear wheels before the software download and 385 HP / 420 FT/LB torque at the rear wheels after the download. It is a RUSH! The car runs great. It was an extremely noticable upgrade. However, lately I've noticed the smell of my CATS going bad. I am going to have to do something and don't won't to go stock again. I want cat bypass pipes as opposed to high flow cats for better sound, added power, less lag/faster spool, and they are simply 1/2 the price. I am not concerned w/ emissions. The word on the street is that cat bypass pipes will set off the check engine light which is a concern of mine. Does anybody have any experience w/ this? If so, is there a correction for this. Based on previous posts on similar subjects, I am leaning towards Fabspeed. I am told by "TPC" the cat bypass is good for approx. 20HP at the fly wheels (not the rear wheels). I would love some input.

Bull
Baltimore, MD
PCA Chesapeake Region
'96 993 tt
'94 968
'77 911s
'02 BMW M3

Dick in TN

Hi Bull,

I'd say that you have your suspension pretty much dialed in! Wanna share with us your suspension changes? Thanks.

Bull993tt

Hey Dick,

Yes my suspension is dialed in, however it is not as aggressive as it appears. I didn't want to go too overboard with my ride quality as I still want to drive it on the street and have a full set of teeth when I'm done. I learned this the hard way w/ my 968 which is very very aggressive. I have factory shocks/struts (reds) with Eibach spring sets. I choose Factory 993 RS EURO sway bars over MO30's and other aftermarket bars. The car is corner balanced with lots of negative camber up front to dial in some oversteer. It drives a little like a 2S as opposed to the "neutral" AWD typical feel. Also, when autocrossing (as pictured), I'm running Hoosier autocross compounds which heat up when you look at them. All in all, it is a great "best of both worlds" set up in my opinion. It definitely is a little loosey goosey for the track, but is an "FTD" autocrossser with somewhat mild characteristics for the street.

I would still love to hear some input about the check engine light with a Cat-Bypass. Anybody???

Thanks,
Bull

ScottMellor

OK. I'll chime in with my particular experience. Do a search on CAT bypass and you will find many different experiences though.
I have an FVD ECU of some kind and I have no check engine light issues with CAT bypasses after about a year. My check engine light is still completely operational. I have the FVD CAT bypasses, which are plumbed for the sensors just like the original CATs.
Again, other peoples experience with this have been different, but I'm pleased with my particular set-up.

Mark in Baltimore

Bull,

What a coincidence that you made your first post a few days ago and happened to be the first person I gave my Rennlist card to! Your car looks great; I'm sorry we didn't have a chance to talk more.

Bull993tt

Mark,

It's a small world. How cool is it to be posting messages on a worldwide scope and wouldn't you know it... a fellow Rennlister that you have never met or seen rolls up next to you in your own town and hands you a rennlist card. I got a kick out of it. It was the 1st time in 2 months I broke the tt out with the crappy weather. Anywho, I will be going to Summit Point and VIR a couple times this season w/ the 968. Let me know if you will be there. Also, try to make it out to a couple Chesapeake PCA Autocrosses, we have a pretty sick lot (very big w/ high speed courses... for autocrosses at least).

Bull
Baltimore, MD
PCA Chesapeake Region
'96 993 tt
'94 968
'77 911s
'02 BMW M3

Mark in Baltimore

Hey, Bull,

I'll look for you at SP. I'll be at Summit for the Potomac DE in March. My other DE dates are TBD at this point. I'm also planning to do the club race at Summit in August and the VIR race in October.

I used to autocross a bit in the 80's and really prefer track driving MUCH more. The amount of seat time you get on the track is more fullfilling to me.

Douglas Driver

Bull

I noticed you are running Hoosiers for autocross. What sizes on what wheels?

Doug Driver

fc-racer

I will play devil's advocate here and say that I think the suspension in that car is not actually dialed in. Usually, when you see a tire hung up like that, it usually means that the suspension has run out of travel and the anti-roll bar is picking up the inside tire.

If this person is successful at racing, he/she is probably doing it through sheer heroism or the car may still be balanced, albeit with less grip than optimal.

My racecar runs out of travel in the rear and picks up a rear tire on corner entry. It's really annoying when you want to get on the power in a 475hp AWD car with narrow tires and one of your driven wheels is hanging up in the air!!!

A stiffer setup or a higher ride height would probably make that car in the picture a lot more driveable and userfriendly.

Bull993tt

Doug,

I am running 245/35/18's up front and 285/30/18's in the back. I didn't want to change the factory diameters of the wheels and therefore lose compensation of final gear ratio. In autocrossing it is important to have those turbo's spool as quickly as possible coming out of the hole and out of slow tight 2nd gear corners. If you go wider, the sidewalls grow larger and it gives you a higher gear ratio which hurts your acceleration. Many people say that is pointless when you have a car w/ almost 500 hp at the flywheel, but autocrossing is a sport where .001 of a second is everything. Hoosier Autocross compounds are truly great tires... they just don't last long.

Bull

Bull993tt

fc-racer,

You aren't being devil's advocate, you pretty much said everything right and I agree with it. The tire is picking up because of the setting I choose on both the front and rear Factory 993 RS Euro sway bars. However, you stated the your right rear is coming up on corner entry making the car loose when you're back on power. Settings for road racing and autocrossing are night and day differences. As I mentioned earlier, my car is not ideal for road racing, but you can't have the best of both worlds. I will not go heavier on my spring rates and ruin this car for the street. I learned this the hard way with my '77 widebody 911s and 968 which I strictly use for the track. In the picture above, you notice that I am picking up the left front tire coming out of a fast corner under full acceleration which means that the majority of the cars weight transfer is occuring at the rear end of the car which is where most of the cars traction is coming from regardless of the AWD factor. I haven't noticed if my rear raises like yours...(I'm sure it does under the right circumstances) but these are apple to orange comparisons. All I know is the car feels very balanced with great turn-in characteristics. It has a good amount of oversteer built in and is usually running the Fastest-Time-of-Day. But then again, maybe I don't give myself credit, maybe my suspension and car aren't all that, it could have something to do with my smooth but "DRIVE IT LIKE YOU STOLE IT " mentality. Who knows, but I like your well thought out reply.

Bull
Baltimore, MD
PCA Chesapeake Region
'96 993 tt
'94 968
'77 911s
'02 BMW M3

fc-racer

Bull993tt,

Your car would definitely be more userfriendly if you could keep it off the stops. Your fastest time of the day is probably more as a result of your driving rather than the car

As for my racecar, it's a 1991 Eagle Talon AWD, a front engine, AWD turbo car. I was not referencing my 993T in the post. If my 993T ever picks up a rear tire and not a front, I will have done something very, very, very wrong

ZCAT3

Bull - I have Cargraphic cat bypass pipes and have never had a check engine light due to them in 2 years. I, like Scott, also have a repgrogrammed custom ECU so that may be part of it. It seems to be a crap shoot - some people report this issue repeatedly and some never have it. One thing I will note is that you are probably pushing your stock K-16 turbos to the limit. I do not think I have heard of anyone running them with the HP you are seeing. In fact, it would not surprise me if the smell you are noticing is the turbos dying?? Of course that would give you an excuse to have the rebuilt ot better support high HP