I know, I have not done anything ridiculous yet!!

 

the new z06s are a handful but the gt3s acutally arent awefully hard to catch...you just have to use your huge torque advantage and slow in fast out to slow up the NA guys and then power away while they are still clamoring in 1st gear or low 2nd...

As for CAR mods, I would say hands down a bi-adj race suspension is in order and 200 more lbs out wouldnt hurt...haha...as for engine, im running stock motor with just exhaust and still wailing on most of the standard DE competition...well see about the gt3s at my next clubrace...

 

Keep up the good work! Your car weighs 3100 pounds?
Are we talking about the 997 GT3? I have no problem with the 996's but man the 997's are fast!!!

 

oh, nah, my car is still prolly inbetween 3200 and 3300...otherwise I move up a class and get my *** handed to be my gt2s...

And the 997s are really quick, but I dont acutally know if they are in my class or not as the 415hp puts them near the 420 i have stock but with a couple hundred llbs less weight...that said, if you have around 480 hp with a turbo and a great setup...well, anything is possible with the "right" driving around a track...haha...you know that though

 

Please read what was written a bit more carefully. I never stated that EGTs were useless. Nor did I state that aircraft engine failures were insignificant. However, compared to the dynamics of a car at a race track, most aircraft engines operate under a nearly steady state loading condition. EGT’s work fine in this application as the hysteresis associated with probe heat up time is minimized and ignition timing is relatively static. Fatigue failures of the probes themselves are also minimized in aircraft as the total heat/cool cycles are a fraction of those seen in a car used for road racing.

Many aircraft engines are still carbureted as well, that doesn’t mean a carburetor is the best choice for the topic at hand. Therefore, the argument of “it’s used in aircraft� is irrelevant to the situations we are discussing here. Making statements of that sort indicates somebody who is reaching, but maybe that’s just my interpretation.

And I agree, using both is great. But if choosing either/or, using an EGT instead of a wideband is a poor choice since it is a secondary measurement to ideal combustion and is dependent on so many other factors.

 

EGT’s are indeed useful if you are worried about turbo life. But again, that is not what we are talking about here is it? This is a thread about an engine failure, not a turbo failure. So these statements are again irrelevant to what would be most useful to help Tom prevent future engine failures.

Maybe you should try a better wideband, the Zeitronix isn’t exactly what I would choose for easy viewing. A bunch of numbers flashing on a screen aren’t useful in about any driving situation. Once again, I have absolutely no problem recognizing a lean condition thanks to the colored warning LED’s of the AEM in my car (or any of the cars I have tuned). You really should consider trying one out as it's a pretty good product:

http://www.aempower.com/ViewCategory.aspx?CategoryID=67

I take it your 944 is your track car? Where do you have your wideband display mounted? I watched the video of it, and I don’t see a wideband in plan sight anywhere unless it’s mounted out of camera view on the A-pillar. Regardless, if you genuinely think that an EGT will properly alert you in time to prevent engine failure due to a lean condition (on one or multiple cylinders), and a wideband will not, then I really don't have anything else to say.

 

Brett,

this is precisely why an EGT can be more useful than a wideband in monitoring an engine's health during stress loads. I am sure that you are aware many cars have failures running perfectly tuned AFR's. The modern OBD II Motronics monitor 4 O2 sensors (though not wideband) several times per second. The thing that kills engines, especially FI engines is heat. The EGT measures combustion chamber heat and gives clues to whether or not multiple factors are at optimal or not. The AFR measures just AFR. It will not tell you if you are knocking/pinging/pre-detonating, if you have a fuel quality problem, if you are at risk of burning a piston or a valve, or if you are about to cook a turbo. It is slower reacting by far than a wideband, but the wideband lean-out disaster is still only one possible mode of failure.

For me, I have been using the EGT in a very crude application. I run a single EGT on my crossover pipe. I have bungs on all 4 of my primaries but run a very conservative boost and fuel map for track. I am looking primarily at preventing turbo failure and burning valves/pistons and not at all at optimal power. The Zeitronix I have mounted in the console down by the radio where it is far out of the line of sight, but I am only sweeping the guages - EGT, AFR, oil temp, water temp, boost once per lap on the long straight of TWS when the engine is under max load. If it blows, I am out only about $1k. For a tt the cost of failure is much, much higher.

 

This is not correct, as a lean condition is not the only thing you are looking for. When my ECU detects detonation from any cause (be it too lean, heat soaked, too aggressive timing, poor fuel, etc), it retards timing and adds fuel. My A/F ratio at WOT in full boost is a flat 11.6:1 across the board (with no running issues). If my ECU thinks it sees detonation via the knock sensors, it adds fuel and my A/F curve instantly dips into the 10’s. The wideband registers this addition of fuel, hence giving me a visual indication of detonation for ANY reason within 200-300 milliseconds.

At this point I do not care why it detonating, all I care to know is that it DID see some detonation, and I need to back off the throttle or suffer engine damage. The wideband tells me this every single time without failure regardless of cause. It is a very simple method that takes advantage of the ECU’s built in knock feedback controls.

The EGT will not show an increase in temp (due to the now retarded timing) for several seconds of WOT, and possibly not at all if the pull is not long enough to properly heat up the probe, leaving you completely unaware that your engine is experiencing detonation for an extended period of time. This is not a good situation to be in. Most engines can only survive through some small amounts detonation before suffering severe damage. The time it takes for an EGT to show ANY indication of a non-ideal running condition compared to the ~300 millisecond response of a wideband often makes the difference between a close call and catastrophic failure.

 

Brett,

your AFR going rich is probably due to profound timing retardation rather than the ECU adding fuel. As far as I know I don't think the computer is ever going to add fuel to a cylinder that is already detonating. Detonation will cause lower EGT's and higher cylinder head temps, not higher EGTs.

I think you have made it clear that we are going to have to agree to disagree.

 

Interesting. I would have thought retardation/cutting spark might be enough. I guess if it is pre-igniting though, the flame path already exists.

 

When the ECU sees detonation, it pulls timing. When timing is retarded, EGT’s do indeed increase. This is a very well-known fact of ignition tuning.

The A/F ratio will not change even if the ECU pulls 20 degrees of timing (assuming no misfiring).

The A/F will only change when the ECU adds fuel, which it does in combination with pulling timing when it detects detonation, as Kevin verified.

This is true for the stock 996 ECU, as well as other OEM and aftermarket ECUs such as the one I am currently running. Below is a screen shot showing how the ECU I am using reacts when knock is detected. My A/F goes rich upon the ECU seeing knock because that is what I have programmed it to do. Dumping fuel is one of the most effective ways to combat detonation, as pulling timing (even a large amount) is only helpful to a point.

 

Tom, I track my car about 5-6 events a year , I installed an oil temp, fuel pressure & boost. I set them @ the peak levels I want (audio alarms). Just in case! I might be able to save the engine ...tom

 

thanks, going to do the same!!

what's better the A/F gauge or fuel pressure, I was going with the A/F

 

Tom, sorry to see your car down , at least you know it's in good hands. By the way i have your twin in Tampa in the same shop! Sucks to see your car that way, hopefully your experience helps others as it did me.

 

Danny,
saw your car, very nice!! sorry about the tranny sounds like at least it is covered!!
my engine came in today go check it out, I'll posts pics later
tom