Interesting Discovery...

94DreamGT · Mar 28, 2004

Either my factory tach is way off or I have no rev limiter.

Took her out today to find out where the rev limiter is just so I know what happens when I hit it. Figured this would be a good thing if I would be shifting at 6200rpm with a stock limiter set at 6250rpm. I have yet to ever touch it and just wanted to be prepared so I know what happens when I ever do at the track, on the street, etc...

Result: She's still pulling up to 6500rpm as shown on the stock tach. This was in 1st and in 2nd I ran it up to 6300rpm or so with no sign of limiter coming in.

Did this a couple of times and never had the balls to go higher than 6500rpm to find out where the limiter actually is...but I know its there. Something about seeing it climb towards 7000rpm with all stock internals makes me kindof weary. Tach must be off something fierce though. Any ideas on how much? Not really planning on getting a tach, maybe a shift light though which would tell me where I actually am on the shifts.

This made me think then...if it is off by a couple hundred rpm, then when I was shifting at 6000rpm racing that LS1....I still had a lot more left in it...hmmmmm.

Also...other updates. A couple of bolts on my oil pan turned a good full turn or more when I got under there to check them out and snug them up. After I got back and parked it, no signs of oil...or at least yet after an hour or so. Hopefully that was the cause of my oil leak and not the rear main or back of the pan.

New problem popped up as I have been driving in traffic more...thing is heating up faster and quicker than ever before. Don't know if this is a by product of the aluminum heads, but sitting at a light, within 2 minutes the stock temp gauge is on A heading towards L. I flip on my manual fan switch which cools it down, but I don't like it getting that hot. Maybe next on the list will have to be a radiator.

SuperSync · Mar 28, 2004

The stock gauges are really nothing more than idiot lights. Esp. the oil/water/volt since they are designed to show a value on a scale that is either in or out of limits, not exactly what the value is.

As far as your car heating up, how do you know it's really getting that hot? Between A and L on my stock water gauge is translated to 190-210 on my Autometer gauge sitting in the pillar, which ISN'T really that hot. According to the service manual, these cars are liking 200-220 degrees for fuel injection...whether or not we like it or not.

If you are concerned with temps I would definately recommend a gauge that shows degrees...you'll see that the in-dash gauge isn't all it's cracked up to be...it tickles me to see people saying my car's between the M and A but sometimes at the top of the L when in fact it's different on different cars in terms of degrees.

SS

94DreamGT · Mar 28, 2004

I couldn't agree with you more SS...Autometer Water Temp guage is on my short list of next things to get

95snoozer · Mar 28, 2004

screw the tach... just get a shift light keeps uyour eyes and midn on the road.

ypou can even toss it behind the ac vent

Zero Signal · Mar 28, 2004

ypou can even toss it behind the ac vent

Man, that's an awsome idea!

sirstuntalot · Mar 28, 2004

i noticed the same thing with my 93 cobra i used to have. The stock tach is off a few hundred rpm depending on how fast your rev... but i also had an autometer tach... and at times reved the motor to 7000 rpm with no sign of a rev limiter.... strange huh

Killercanary · Mar 28, 2004

The 94-95 car's have a 7000rpm rev limiter. I never believed it, but when I got my EEC Tuner my PIP showed it plain as day... 7000. I know my dad's 91GT had a 6250 rev limit from the factory as we hit it on more than one occasion, and my mom's bullitt does as well as I found out today at the track when I was doing a burnout in it. I even had Dave at Kauffman Motorsports verify I was looking at things correctly when I thought it showed a 7000rpm rev limit, and much to his amazement he confirmed it. I always wondered why I never bumped the thing. I even have dyno pulls made to 6300rpms, and I've done nothing to alter the rev limiter.

Zero Signal · Mar 28, 2004

That's crazy, I'm afraid to go past 5k, lol. Seems pretty gutsy pushing the stock shortblack over 6k even with the right heads.

DaveB · Mar 28, 2004

I dunno, I've revved my car up to 6250 and it just hits a brick wall at that rpm. This was in 1st and 2nd. I guess some have the 6250 limiter and others the 7000.

Rootus · Mar 28, 2004

My car has a 6250 limiter... but that's because I'm running the J4J1 (Cobra) calibration, and that was the default . BTW, I'm not sure I'd go "hunting" for the rev limiter, especially in the 6500+ range... that's begging for trouble.

Dave

94DreamGT · Mar 29, 2004

Killercanary said:
The 94-95 car's have a 7000rpm rev limiter. I never believed it, but when I got my EEC Tuner my PIP showed it plain as day... 7000. I know my dad's 91GT had a 6250 rev limit from the factory as we hit it on more than one occasion, and my mom's bullitt does as well as I found out today at the track when I was doing a burnout in it. I even had Dave at Kauffman Motorsports verify I was looking at things correctly when I thought it showed a 7000rpm rev limit, and much to his amazement he confirmed it. I always wondered why I never bumped the thing. I even have dyno pulls made to 6300rpms, and I've done nothing to alter the rev limiter.

I have NEVER heard this. I always assumed it was the same as the A9L processors on the earlier Fox EFI stangs.

I'm not doubting you Paul, but is there anyway this info can be verified? I might put something up on Corral and see what the response is. This now makes me feel a little uneasy about how hard I was pushing the car.

<--- Now more confused than before

VibrantRedGT · Mar 29, 2004

Get just a shift light.

If you have the stock radiator then it's time for a Fluidyne. More HP generates more heat. Same thing happened to me when I changed the heads/cam. Had nothing but cooling issues until changed radiators and got control of my cooling fan.

Killercanary · Mar 29, 2004

I got the following information from http://www.iwantperformance.net under their FAQ section. They have some good starting information there for EEC Tuner users.

PIP

Think of this as a rev limiter using the following formula:

PIP = 6006250/maxRPM

maxRPM = 6006250/PIP

for example stock A9L

PIP = 961 maxRPM = 6006250/961

= 6250 rpms

Lower numbers give a higher rev limit.

The PIP is a sample rate frequency that limits the PCM program operating loop to a minimum rate.

If the loop is sampled less then PIP times within one operating cycle (2 crankshaft revolutions), the

PCM limits rpm.

With this logic, you should be able to set the pip to 1 and the car should run normally, but not limit

RPM. I have tested this on an A9L processor.

In my STOCK T4MO calibration my PIP value is set at 833. So using the formula maxRPM = 6006250/PIP and my PIP value we get 6006250/833=7210rpms. In my EEC Tuner setting though it says PIP=6250000/MAX RPM, so using that we get 6250000/PIP=MAX RPM. 6250000/833=7500. OK... now I'm a little confused. I could have sworn it came out to exactly 7000 when I did it before. Can anyone with a twEECer or EEC Tuner with a T4MO look and see what their STOCK PIP value is? Maybe I changed it long ago for some reason and didn't change it back??? I don't ever remember messing with it. I can't look up my stock EEC settings right now as my car doesn't have a battery in it. I'm 100% positive that stock it was at 7000 and I know for sure that I have pegged the stock tach past 7000rpms before doing burnouts by accident. Like I said, I douted it too, but I had Dave at Kauffmans, who is an EEC Tuner guru, verify this because I always thought it was set at 6250 too, but could never understand why I didn't hit it.

Rootus · Mar 29, 2004

94DreamGT said:
I'm not doubting you Paul, but is there anyway this info can be verified?

You can verify it yourself -- download the TwEECer software, then download the T4M0 (94/95 GT) binary, and look it up, the rev limiter is a scalar on our processors. It's 7000 on the T4M0, I've verified this. It's 6250 on the J4J1 (94/95 Cobra).

Dave

Killercanary · Mar 29, 2004

OK, I just went to the eec tuner group on yahoo and downloaded the binary for the T4MO and did the parse function on it and sure enough, the PIP is set at 833, so the rev limiter is higher than I thought. Even the other limiters in the stock T4MO settings have a minimum value of 7000rpms.

swingline · Mar 29, 2004

Yesterday was the first day I had driven my car in a while so I shot her up to about 6k. I don't do that very often and I don't make a habit of searching for the rev limiter. If you go bouncing off of it often enough you'll be sorry.

Rootus · Mar 29, 2004

Killercanary said:
OK, I just went to the eec tuner group on yahoo and downloaded the binary for the T4MO and did the parse function on it and sure enough, the PIP is set at 833, so the rev limiter is higher than I thought. Even the other limiters in the stock T4MO settings have a minimum value of 7000rpms.

The PIP value doesn't work the same way on 94/95's, ignore it .

Dave

94DreamGT · Mar 29, 2004

Ok...I was looking on the TwEECer website and it shows:

T4MO - 94-95 5.0L GT Vert 5spd
W4HO - 94-95 5.0L GT
U4PO - 94-95 5.0L GT Auto
J4J1 - 94-95 5.0L SVT Cobra 5spd
ZAO - 95 Cobra R

By that list...I would think my 94 GT 5spd. coupe would be using the W4HO calibration. Dave, you said 94/95 GT's use the T4MO binary. Which one is it?

Killercanary · Mar 29, 2004

What do you mean Dave?

1105 · Mar 29, 2004

This past friday I had my car up close to the 7000rpm range on accident when doing a burnout... It came up pretty quick. I had always thought it was at 6250rpm too but I guess now, But this is coming from the stock tach

The timing light I use has a built in tach for one of the settings you can choose form, and its saying my car is idling around 600rpm while the tach in the car says 800rpm. If its off that much at idle, how much will it be off in the 6000rpm range?

Interesting Discovery...

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