Jim R.

Good luck with it Seth.

disclaimer: I am not an expert, and am not trying to start an issues here

Regarding the pinging, the GT chips do have more aggressive timing than S4 or GTS. I have to say that I have yet to get my car to ping under any circumstances since installing my SC kit. Be carefull with the ping--we are pushing 16 year old head gaskets past their design limits and ping will lead to early failure. As far as "throwing more fuel at it", I use a RRFPR and my boost, fuel pressure and RPM's all build linearly instead of higher boost down low. So in my application, the ratio of rise to boost for the fuel pressure works well without going rich under light throttle. As far as I know, Gretch's GT behaves the same way. Since I spend most of the time driving with light throttle vs WOT, this is key to driveability. Get it sorted, it will be much more fun. As a quick bandaid/fix, have you tried pulling the hall sensor for a 6 degree retard of timing--the 3 degree of the knock sensors seems to not be enough?

Good luck, and be carefull. The car is now a beast and will bite!

Jim R.

Th Dude

Glad to hear that you're finally up and running, Seth

To those that helped Seth get this accomplished.
D

GoRideSno

Jim R.
Both Seth and Jim_H have to run 91 octane. Unless you have dynoed your car on 91 octane then you have very little similar experience to compare to Seth or Jim. I'll bet you are able to get 93 on the east coast. What kind of # did you get when you dynoed your car?

Garth,
That's a good idea. I am going to check into that. May be a necessity for the guys that only have 91 octane for their SUPERMODEL GTs.

Seth's car pinged on the dyno before the install too. Part of it is just the poor quality low octane fuel available in CA.


Andy K

Jim R.

Andy,

I have "very little similar experience to JimH and Seth". I get 93 octane here, and my dyno is not yet scheduled. I will have it in 3-4 weeks depending on my schedule with my wife, kids, work, and shopping for a new house. I'll let you know when it is done, it just runs great, so I am in no rush to get it done. I was not looking to step on your toes here, just thought more info is good.

Jim R.

Tony

While 2 points in Octane may help, it sure wont cure the issues of fuel flow/delivery which IMHO is what is going on here. You could run 100 octane through it but if the mixture is lean..its lean. period.
If its lean, it gets hot, if its hot it will not help detonation prevention.


I think determining whether its fuel or sprk/timing related would be a good idea.??

pulling the hall sensor seemed to be a good idea to atleast try?

Tom. M

Just an FYI..the CR spec for a S4 is 10.0 to 1 with + or -0.6...so...range from 9.4:1 up to 10.6:1 ....so far a couple we have checked here (pac nw) have ended up on the low end of the CR..ie 9.4:1 or so...The GT spec was almost exactly 10.0:1..+ or - 0.1 so a much more narrow range..ie. 9.9:1 up to 10.1:1..
My 89GT used to ping on moderate throttle going through 3 to 4 k range..on a hot day ..even with 92 ...

Later,
Tom
midlman@rennlist.net 89GT

Bill Ball

Yes, Seth's car pinged on baseline dyno. Driving around yesterday, there was no ping. Ping was only with heavy dyno load and partial throttle, something you would not encounter except perhaps on a very steep grade.

The gas quality is an issue. My car NEVER pings, but it did on cheap Safeway gas on a hot day after the SC install. Sticking with namebrand, no pinging at all since.

With Seth's car on the dyno, we could see the knock sensors working, resulting in very distinct down ticks in the power curve. So, they were working within their limits. The runs with the throttle hammered and no audible ping had smooth power curves. On my Durango, the knock sensors progressively retard the spark and will literally shut the car down. The 928 system seems to have a limited effect.

Just to keep the discussion going, as what I understand about fuel curves is negligible, since the car seemed fine on full boost, it appears to just need more fuel for no/very low boost rather than retarding the spark curve. How would you accomplish that?

Seth W

Yes, Andy is right my car pinged on the dyno (at second temp line) after Steve S and I gave it an italian tune up that morning (he wanted to drive a before and after GT with a SC).

Bill is correct too, it was 410 at just over 5psi at 6200 rpm, the belt was slipping slightly after 3500 rpm on that run. So, there is a whole lot more ready to be extracted once fully sorted out. I'm sure that there is another 40-50 hp in this car between 5psi and 7psi. That said, I'm going to conservatively develop AND DRIVE this car. Adding 100 plus HP is something to be respected and now that I've scared Bill with some street terror I'm going to re-learn how to drive my car.

Thanks Dennis--heading to Italy and this Saturday I will be rooting amongst the tifosi for Schumacher. I'll say hi to all the Grid Girls for you guys. LIkely need to re-corner balance the car when I come back to heavy!!

Bill Ball

Mike:

Yes, but Murph describes tip-in as a full throttle issue where the fuel flow cannot catch up fast enough to match the demands from the boost. Now, Seth may develop that limitation when we tighten his belt, but at this point it looks like he has a low-end, no/low boost lean condition. Once boost comes on, the 85-6 regulator responds and, as far as I could tell, there was no knock retardation. It just doesn't do very well when the car is under load but partial throttle.

Jim R.

Mike, first off, sorry about your car. Second, I'm guessing your statement is directed at me. You can check with Tim on the specifics, but at 10 psi or less there is no issue. He runs way more than that and tries to break it on his car so we don't. I run about 8 psi with no issues in daily driving or WOT. As I said to Andy, I'll let you know when I dyno. I will also try to real time for knock detection with the JDS "spanner" tool so I will know if I am getting knock that I can't hear. Sorry for stepping into the supermodel forum.

Jim R.

Bill Ball

Jim R - don't apologize. I hope we're all trying to share and figure things out. The Murph issue seems different to me than what we are seeing on Seth's car. The situation may change as we up the boost by tightening the belt. Since he joined the 400+ club, Seth may decide to put on a 5 lb pulley, tighten the belt and be happy there, and we can just address the partial throttle lean condition.

CMW

As Mike said... My stock GTS pinged at the very start of acceleration STOCK.

This car has ceased pinging at 5PSI... although I think I am running a bit rich at the moment.

Seth you r car has to be a monster off the line with the 5 speed GT. I love my car but I simply can't wait to see what the GT's really put down when 100%

Seth W

I can't even imagine what launching it would be like, I did not get on it until a rolling 3k in first gear and then it was just silly. No traction, like driving in the rain.

Hey, we are all in this community together. I know that WE ALL benefit from the fair, unbiased exchange of information here.

We consumers need to continue to exchange information so that we can all improve our cars. In a couple of years this SC thing is going to be as common as headers and RMB's. It will be like the turbo upgrades on the 944turbos.

GoRideSno

Jim R,
Just wanted to point out that it wasn't an apples to apples comparison. My toes are unscathed.

Andy K

GoRideSno

BTW Guys, it is timing.....period. The setup on Seth's car is what I had on my car recently. I made 402RWHP on 93 at 8.5psi with my S4 auto. It has never pinged at all with this setup.
Spending time thinking about/talking about fuel is mainly going to be a waste of time. Garth has made the best suggestion.
HTH,
Andy K