TRINITONY

not to hijack...but how does a sc 993 compare to a 993tt, especially in the twisties?

Dick Beers

I have no empirical evidence (ie: haven't gone head to head or know anyone who has) but my guess is that my car, as it is set up, would best the 993 TT. Certainly better throttle response and better suspension.

YMMV

onefstm

I posted this same question on Pelican...

Has anyone checked their air fuel ratio (AFR) using a wideband O2 after installation of the supercharger? I am curious to see what everyone else is seeing with a computer tuned by TPC (split second or uni-chip). After installation of the Fabspeed bypasses while still running the split second box, I was seeing AFR's of 12.5 -12.8 on wide open throttle (using a new Inovate LM-1) . This concerned me so I decided to wait until I installed the uni-chip to retest the car. Now with the uni-chip, 6lb pulley, and bypasses, I am still seeing high 12's on WOT. I talked to Tom at TPC this morning who told me that this sounded fine to him and that anything up to 13.0 when measured through the left exhaust pipe sounded fine to him. He said that on these cars typically the right bank of cylinders would run richer and should show a 12.5 on that side.

I plan to post more about my initial impressions of the upgrade but am limited in time right now. This weekend, I plan to replace my fuel filter, clean the AFM, and possibly replace the fuel pump.

So far, I am impressed with the power gain. With the cat bypasses and 6lb pulley, I would say that 30-40 rwhp is realistic. There is a definite difference in 3rd and 4th gear pulls.

One thing that is really bothering my right now is the sound level of these Fabspeed bypasses with FVD mufflers. For me, the car is way too loud now. Before, I could hear the supercharger under WOT. Now, all other sounds are completely washed out by the sound of my new Nascar equivalent exhaust. The mufflers were great on their own but way too loud when combined with the Fabspeeds. I have ordered a set of stock mufflers from a fellow Rennlister. These should be in by Thursday or Friday so I am hoping that this will solve my sound issue.

mr_bock

onefstm,

I would have to search around for my before and after TPC install dyno print outs... but I think what Tom said sounds right. I am interested in your results after you make your changes and retest.

Dick Beers

Jeremy,

Must be nice to be able to actually do something with your car this time of year.

I'm thinking about trying to find someone around here who can dyno an AWD car as I'm curious as to what kind of hp & torque I'm actually putting on the ground. Looking forward to hearing your results.

Mr. Bock,

How is the resonance with the B&B setup on your car. I had an '88 930 with the B&B headers and exhaust system that was almost unbearable between 2500 and 3500 rpm. Made the car quicker but gave me a headache if I drove too long.

Geoffrey

Several comments here from my experiences.

With MoTeC on several 993RSRs and my 964RSR, I do see the right bank consistently richer than the left bank, this is with ITBs, Factory RSR ITBs and resonance manifold, and with the plastic 964 style manifold. I have never been able to determine specifically why this occurs, but I believe it to be exhaust manifold related.

The older TPC system that I worked with showed extremely rich mixtures, in the range of 10.8:1 when on full throttle with the smaller pully (5psi maybe). When I put MoTeC on the engine and did not use the 7th injector, I could not get the intake air temps cool enough. I believe the 7th injector system is required to maintain proper IATs moreso than for additional fueling.

If you are running the AFRs near 13, I believe that you will have problems with the engine. I think that as long as you can keep the IATs below 130F by the use of a 7th style injector, you may be able to run as lean as 12.5:1 under full throttle.

I would approach with caution.

onefstm

The current AFR's really scare me. On 3/4 th's throttle, I do see AFR's in the low 11's or high 10's. However, upon WOT I mostly see high 12's. Does anyone have any idea what is causing it to be lean on the high end besides a clogged fuel filter or weak fuel pump? I may replace both this weekend if they are reasonably affordable.

98993c2s

6 psi without an intercooler??? hmmm.

onefstm

I plan to add an intercooler before summer; however, TPC says that it is fine without it at 6 lbs. According to Tom, they have sold around 2,500 supercharger kits world wide so it is probably safe to say that it is a proven kit.

Also, it is 25 degrees in TN today so that should help keep my charge pretty cool.

I plan to put a fuel pressure gauge on the car on Saturday to see if I am holding full fuel pressure at WOT. If I am not, then the pump or filter may be my problem.

Does the 993 have 2 fuel pumps? Are they known to be pretty reliable?

98993c2s

6 psi concerns me...as do the posts about detonation. I personally wouldn't risk forced induction (even at relatively low boost levels) without an intercooler even with reduced compression.

Did they say those 2,500 went into 993s? I suspect that's probably a figure encompassing all their models.

Geoffrey

You won't easily be able to test the fuel pressure unless you have a dyno where you can provide boost pressure the regulator. The factory regulator is a 3.8bar 1:1 rising rate regulator. Ensure you have proper vacuum to the regulator.

onefstm

Geoffery,

My friend has an external fuel pressure gauge that has a long hose and a T on the end. He uses it to tune his rising rate fuel pressure regulator on his turbo Miata. If I Tee that gauge in to the test port on the driver side rail, run the gauge under the wiper on the outside of the front windshield, and drive around won't I be able to monitor the pressure in the system while driving around?

I am thinking that I should see base pressure + boost at mid throttle and hopefully maintain it under WOT. If the pressure falls off at full throttle/high rpm's, then my thought was that I have a problem in the fuel system. If the system maintains full pressure (say 50psi - I am not sure what base pressure is on the 911), then I would assume that the pump is fine.

I could be totally off here. Let me know if I am leaving something out.

Thanks for your input.

Geoffrey

Sounds right although I don't like the idea of a fuel line on the outside taped to the car as you are wailing down the street. However, you'll see 55psi (3.8bar) with key on, engine off. When you start the engine, it will drop by about 6psi due to vacuum so you'll see about 49psi at idle. At 6psi of boost, you'll see about 61psi.

onefstm

Geoffrey,

Thanks for the pressure information. That is exactly what I needed.

The external gauge came with his Corky Bell (author of Maximum Boost) Miata turbo kit. You actually tune the FMU (rising rate regulator) to 100psi under full boost. I will take a picture of the guage on the windshield and post it here later.

Before anyone says anything, I paid for my Rennlist membership last week but still haven't been upgraded even though my card has been charged.

MPB993

onefstm,

I have adjusted split second box afr to 12:1 under wot using innovate LC-1. I was seeing a 0.75 variation left to right so decided to go slightly richer. I have now adjusted to the uprated injectors its more like 0.3. As mentioned previously. The w/a injection substitutes for the 7th injector cooling.

BR, Mark.