Tampa 928s

Well so far so good except for the fresh gas I don't drive it enough!

Z

I forgot to mention checking to make sure that the cam timing is correct. We found Shane's to be off and corrected that before starting the supercharger installation and doing any tuning.

Tampa 928s

It was set up with Pokens tool!

Z

When Shane got the car back home, he modified the car from what it was when it left Green Bay, increasing airflow through it, and increasing it's power. Unfortunately he did that and didn't make the tuning changes stated by Tim on this page of the thread talking about it.
https://rennlist.com/forums/928-foru...new-car-4.html

A little over a year later, the head gasket went out. I didn't see the failed head gasket, so can't comment as to how much of the falure may have been from it being due to the state of tune with the car in that configuration, or how much it may have been from the gasket just being old and in poor condition.

As far as a properly tuned car needing to be retuned due to a 500 foot elevation change, it didn't seem to be any problem for Shane's car going from the 600 foot above sea level elevation of Green Bay, up and over the Rocky Mountains, and back down to the elevation of where he lives in Washington.

Tampa 928s,
With you being at your current boost level, you're safer from damaging anything from a bad tune than you would be at higher boost levels. Definitely don't think that you're completely safe because of that though. A bad tune can definitely still ruin your day, especially if you start changing the ignition timing. The SharkTuner is a great tool, but if there's not somebody who knows what they're doing working it, you can end up needing more than just a head gasket before you know it. If you're going to be SharkTuning, an adjustable fuel pressure regulator and MAF with custom tuning pots on it just adds to the complexity and variables when tuning, and wouldn't be needed.

Tampa 928s

I just read about Shane's car, I thought the head gaskets were done when the S/C was installed.
I have always worried about the original head gaskets and the ability to stand up to the increased pressure over the long hall. Since he was running about 12 Lb's of boost I am around 7Lb's it seems like this would be less of an issue.
What did he do to increase the airflow, add a smaller pulley I can't think of what else would cause the increase in power. I want to avoid any of the same mistakes so I am curious what he caused to do this.
I am comfortable with the tuner but any info would be helpful. Like I said I think this 86 has a lot more on the table but needs to be tuned based on my location and placement of the Maf.
Project:
Maf set up under fender
Adding Adj FPR
Increase size of Injectors
Shark Tune.

Z

No, the head gaskets were not replaced. They were still the original factory installed ones that were in the car.

The two things that are going to make the head gaskets fail are deterioration due to age and improper coolant maintenance in the car's past, and detonation. Both of those things will cause a head gasket failure, even if the car's not boosted at all. The higher the boost, the more likely that there'll be detonation in a system that's not tuned or operating well. Some cars have blown head gaskets when completely stock, and others haven't, even when run at 17psi of boost with the original head gaskets.

As was mentioned by both Tim and I beforehand, the way it was tuned in Green Bay was safe, but the fuel system was basically maxed out at that point with the configuration that was on the car at the time. The 42lb fuel injectors were maxed out with the stock fuel pressure of the car.
https://rennlist.com/forums/5350122-post21.html
https://rennlist.com/forums/5365672-post49.html

Part of the testing that was done when the car was in Green Bay included exhaust pressure measurement. That showed it to be high enough to be reducing power. When he got home, Shane reduced the exhaust back pressure, increasing airflow through the engine, increasing power, and no additional fuel was being added. If the car would have had the less restrictive exhaust on it when it was in Green Bay, and leaning out due to it would have been observed, the car would have gotten an S4 fuel presure regulator and been SharkTuned for that configuration.

I don't know how much power you're making now, but for reference, Shane's '86 A/T car did 370rwhp when we had the Murf stage-1 kit on it, and 480rwhp a day or two later when we had the Murf stage-3 kit on it

Tampa 928s

86 S/C with FMU

I placed a fuel pressure gauge on the following pressure readings:
Idle 30 Lbs
1500 30 Lbs
2000 30 Lbs
2500 30 Lbs
3000 30 Lbs
3500 30 Lbs
4000 30 Lbs

Kicked pedal quickly 38 Lbs

This does not seem correct any feedback?

dprantl

Sounds like you got these numbers with the car in neutral? The FMU doesn't know RPM, it only knows load (i.e. vacuum/boost). You need to do these measurements under load.

Dan
'91 928GT S/C 475hp/460lb.ft

Tampa 928s

86 S/c Vortech Fmu from Tim Murphy

With vacuum removed form FPR 38 Lbs

I just hooked up a vacuum gauge in-line to the Fmu it shows 15 at idle
I injected regulated compressed air into the Fmu it shows at 5.5 Lbs 60 Lbs of fuel pressure.
This seems a little low this shows a gain of 22 Lbs gain at 5.5 Lbs of boost indicating a 4 Lbs FMU. Do I need a larger FMU?
Fmu's Available
4 to 1 Seems like this is the one I have !!
6 to 1
8 to 1
10 to 1
12 to 1

Unless I put my son on the hood while I drive "redneck Tune up or a dyno this seems to be a good test I will wait for feed back or criticism.

Z

The ratio of the FMU is changed by taking it apart and changing the disk inside to a different sized one. I can't remember for sure, but I think that the one that the stage-1 kits use is either an 8:1 or 10:1 disk.

Tampa 928s

I waiting on Tim Murphy to chime in, I believe it was suppose to be an 8 to 1. It seems like its reacting like a 4 to 1 which would explain a lot, that only means that I have the incorrect Fmu for my application.

http://www.motorsportsdigest.com/tech/

Cosmo Kramer

My FMU is 8-1 and so is Imre's it is the recommended ratio for our application. Maybe you are having the same issue as me. As soon as I get some time, I am going to manually pressurize my FMU at 1 or 2 psi with the fuel pump relay jumpered and I am going to see if it is raising the fuel pressure above the stock regulator pressure of 36 - 38 psi. I know it is working at higher boost levels because I tested it on install and I am nice and rich but I didn't test it at low pressure.

Tampa 928s

I had my car running and rigged up a tester and will check it again tomorrow when I have more time. I will graph the fuel pressure based on the positive pressure, I have all the gages still connected. Unless some one comes back with a why not I think this a good way to test it.
I gave Paul "Zeus" a call and he walked me through the testing procedure and this seems like the issue.

Tampa 928s

From what I gather an 8-1 raises the Furl Pressure 8 Lbs for every pound of boost. So at idle "30 Lbs" and at 7 Lbs of boost you should be seeing 86 Lbs are you seeing that type of pressure? My injector duty cycle is maxed out and this may help my A/F ratios seem fine on my data logger like yours except for the transition point.

Cosmo Kramer

Yes I am seeing those pressures, from what I remember with the car off, relay jumpered and FMU pressurized to 7 psi I saw 85 on my rail gauge. At full boost I am in 10 to 11-1 AFR's