ptuomov

S3 and GT have the same lobes, but S3 has an LSA of 114 and GT has an LSA of 110.

pdejong has a twin turbo with GT cams, you might want to ask him how's he liking them:

https://rennlist.com/forums/928-foru...l#post10197592

jcorenman

Sharktuners are the cheapest part of this whole discussion. Check out the price of S/C kits, then the price of replacing everything that might be aged or broken. Isn't it better just to know?

Hilton

$990 for a ST2 that gives you full control, or $360 for an Adjustable FPR makes the ST2 seem like a bargain.

Bmw635

Having installed a Vortech style SC in my BMW E38, I'd rather install whipple style Sc for more early bottom end torque , lower intake air temp for more power.

I'll install a 928 Specialist twins crew style once I am out of CA so I can't wait.

bureau13

Given that (from what I've read) wheelspin in 1st is a big issue with the superchargers, is even more low-end torque helpful? This was a big criticism in the "How to supercharge an RX-8" discussion, because those had no low-end torque to begin with, but that's not the case with these cars.

SeanR

Wheel spin is a result of too much right foot. That can be modulated

demetan

can you adjust the FP with a ST2? How much can a stock FPR be tuned?

jorj7

No, you can't adjust the fuel pressure, but you can control the injector duty cycle by adjusting the fuel map. Which gives you more options, to adjust by load and RPM.

If you need to flow more fuel that the injectors can handle, then you need to up the size of the injectors.

__________________
George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
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http://928.jorj7.com

Hilton

No, with a ST2 you tune the car by adjusting the injector pulse widths and spark timing, using a wideband O2 sensor to target specific mixtures at different load/rpm/temperature values.

Much more elegant than just turning up fuel pressure and hoping the stock maps are close-enough at all rpm's to not damage your engine with detonation or cylinder washing, or that you won't have idle or hot/cold start issues.

Note if you're adding more power, you might need bigger injectors too so you don't run out of duty cycle.

demetan

Very interesting. Do you guys think a 24lbs/hr injector mods would add more power (with ST2) & be sufficient if I decide to go SC? Considering the bang for the buck aspect, the other option could be to keep my stock injectors (19lbs/hr), add a FPR & S-tune it? Good or bad? Any probable issues (heating, flushing, knocking..)

demetan

Very interesting. You guys think that a 24lbs/hr injector swapp can add power (with a ST2) & eventualy be enough if I decide to go SC? Or go with the stock injectors (19 lbs) & a FPR upgrade (bang for the buck aspect) & S-tune it? Possible issues involved (heating, flushing, knocking..)?

Carl Fausett

Thats a good question for the manufacturer of the kit you select. They should know what their experience is.

For us, for example, a new set of injectors is included in the Stage II kit for the LH-Jet equipped cars, but not the L-Jet or K-Jet equipped cars. On those cars we found that yes, we picked up a little more HP with larger injectors but at the expense of a bad idle and weak bottom end. So the stock injectors were a better all-around solution.

FredR

Although people do it, running with higher fuel pressure is just not for me. I migrated to 30lb design 2 fuel injectors with the "more modern" 4 spray head units and metal body.

I did this for various reasons including the ability to run to full rpm without changing over the duty cycle and to prove to myself that I could tune the system using sharktuner without doing any damage to the motor. Before doing anything I did quite a lot of shark tuning runs with the stock injectors and programme so that I could at least understand and see what Porsche intended to happen and set a benchmark for comparison. Once I had a grip on this I started to try and improve on the stock programming and then played around with things like the exhaust mods etc. When i had this reasonably well sorted I then went to bigger injectors and found it reasonably easy to replicate what I had previously tuned.

Thus if I wanted to add on a supercharger I feel confident i can do so safe in the knowledge that I now have a certain degree of competency to do so and that my injectors will definitely support a modest amount of boost.

if 19lb injectors can handle 345 crank bhp on a GTS then logic suggests 30 lb injectors should be able to handle around 500 crank bhp all things being equal.

Rgds

Fred

demetan

I think that you're completly right M. fausset about wich SC kit goes with wich type of FI system. Actualy, I was wondering if tuning with a ST2 (Sharktuner 2) a stock engine (with no power adders) & swapping the stock injectors with moderately higher flow injectors, would be safer regarding knocking & flushing, or the equivalent of upgrading the stock FPR with stock injectors, knowing that I can control the F&IMS (fuel & ignition managing system) with the ST2? In other words, have you or your R&D team ever experimented your kits with the ST technology & what are your thoughs about this type of F&IMS?

Lizard928

24# injectors are really only good to around 350rwhp on an 87+.
I normally install larger injectors so if boost is increased in the future, new injectors aren't needed a second time.