TonyG

You do not want to install the EGT probe in a collector. It will not be representative of the exhaust gas temperature exiting the engine... which is why you install the EGT setup in the first place. Why? Because unburnt fuel is burning in the collector.

You install the exhaust probe exactly per the manufacturer's instructions, and you use the calibrated wire supplied with the gauge, uncut/modified per the instructions.

The best would be 1 probe per cylinder. But often that's not convenient in terms of gauge placement. Furthermore, on a track, it would be impossible to monitor.

Combining to get an average is not good either. This can hide a problem situation.

The best solution if you cannot have 1 probe per cylinder, is to use just 1 probe, and if you're using a stock intake manifold, that would mean the #4 cylinder since it's historically the leanest cylinder on a stock intake manifolded car. That way if you error in your tuning based on the fact that the #4 cylinder runs lean, you error on the safe side with the other 3 cylinders.

TonyG

TonyG

EGT: Exhaust Gas Temperature.

It is affected by back pressure, air fuel ratio, fuel type, and ignition timing. (There is also, to a very small degree, other things that will affect EGT, but for 99.999% of those here, they are irrelevant). All 4 of these things affect each other (basic EGT understanding):

The more you retard ignition timing, the higher the EGT's.

The leaner your air fuel ratio, the higher the EGT's.

The tighter the turbine housing, the higher the EGT's.

Certain fuels, burn leaner and/or hotter than other fuels, also affecting EGT's.


If you stop and consider how each of these things affects the EGT's, you can very quickly understanding the balancing act that goes on when tuning a turbocharged engine.

Example:

More boost causing detonation? No problem... burn a chip that pulls out (retards) the ignition timing some more. That's fine, the detonation is gone. But now the EGT's go up. Remember... advancing timing lowers EGT's. Retarding timing raises EGT's. What's the solution? Richen the air fuel ratio? Ok. That will help a little, but it won't help enough.

What next? You either lower boost, increase the octane rating of the fuel and advance the timing, or open up the turbine (run a larger turbine a/r to lower back pressure... at the expense of more turbo lag).

Yes you can inject water/alcohol, etc... but that's a band-aid approach to fix a fuel quality issue, which itself will cost you in terms of the cost of the alcohol as well as the weight and cost of the system not to mention the reliability of the system itself.

Yes, you can install a better intercooler. That will also lower the propensity to detonate. But there is a limit to how large an intercooler you can physically fit. Plus... cooler air lowers the propensity to detonate. It doesn't eliminate it. There's only so much cold air can do to stop detonation.


In the end, it is always the fuel that becomes the ultimate limiting factor in a turbo charged car.


Anyway.... back to EGT's.

With the EGT probe, you can monitor the exhaust gas temperature. This will tell you if you have a problem that is not apparent by looking at air/fuel ratios. These problems can and do very easily exist in turbo charged cars.


TonyG

TRP951

https://rennlist.com/forums/showthre...gt#post2610063
check post #3

TonyG

>>>http://forums.rennlist.com/rennforum...gt#post2610063
check post #3<<<

You'd need to check for yourself. My #4 was the hottest before I ran a modified intake.


TonyG

TonyG

And... if you really wanted to do it right, you would run 4 probes, and an EFI system that would let you tune each cylinder to compensate for the differences. It's an easy way to pickup 2-3%.

It's just a money thing...

TonyG

xsboost90

or open up the turbine (run a larger turbine a/r to lower back pressure... at the expense of more turbo lag

nice- i thought this since my car has the same laust probe and zt2 as sam grants car, but mine has a hotter reading egt than sams since he has a larger hot side on his turbo. It'll be interesting to see how much it lowers after i get my car running again w/ the larger turbo.

Techno Duck

While on the subject..when welding the EGT bungs to the factory headers one should use stainless steel bungs correct?

Also is the VDO gauge compatable with any type of K-Type sender?

333pg333

Just a stupid question but as we know what harm pre-ignition can do to an engine, I believe Kablooieeee
is the technical term. However if we lower boost or retard timing we can lower that happaning but it's quite likely that our EGT's go up. What is the negative outcome of raised EGT's? Even if we have a 4 probe and run a sophisticated standalone, what is the course of action if we do see raised EGT's on the road or track? I guess we can lower boost or go up in octane level if possible?

TonyG

>>>However if we lower boost or retard timing we can lower that happaning but it's quite likely that our EGT's go up. <<<

Lowering boost won't raise EGT's. Retarding ignition timing will.

>>>What is the negative outcome of raised EGT's?<<<

Damaged head gaskets, burned exhaust valves, destroyed exhaust valve seats. Then the piece of burned off valve bounces around and dings up everything inside the cylinder until it finally exits through through the hole in the exhaust valve, out the exhaust port, through the turbine blades, possibly damaging them as well.

>>>Even if we have a 4 probe and run a sophisticated standalone, what is the course of action if we do see raised EGT's on the road or track? <<<

It's hard to tell on the road since there's not really much time sustained at WOT. The track is a different story.

The thing here is you need to know what's changed. Did you change the chip/programming? Are you running different fuel? Has the engine config changed? Something must change, in order for the EGT's to be different from what they were the last time the car was run on the track for example. If you ran the car on the track, and everything is exactly the same, the chances of you having an EGT problem are slim.

But say you installed a different chip, or installed a different cam, or you installed a different turbo, etc.... then you would want to keep an eye on the EGT gauge. And if the EGT's became a problem, you would be able to determine what has changed, and thus what the problem is, and thus how to fix/correct the problem. But the main thing is that you see it, and back off, and avoid engine damage.


>>>I guess we can lower boost or go up in octane level if possible?<<<

Increasing the octane level by itself won't affect EGT's (although the type of fuel might). But increasing the octane of the fuel will allow you to run more ignition advance which will lower EGT's.


TonyG

lejams

With this system it would be easy to monitor http://www.aircraftspruce.com/catalo...pace_logic.php

1) Any specific cylinder. Choose the cylinder you wish to monitor and change to the next whenever you wish.
2) Sequential step through each cylinder with 5 second delay.
3) Auto select. Selects the hottest cylinder, updated every 1 second.
4) Switch between any selectable function and the auto function and return to the last monitored setting without any data loss!
• User programmable high and low limits

TonyG

>>>With this system it would be easy to monitor http://www.aircraftspruce.com/catalo...pace_logic.php<<<

While I agree that's a nice gauge setup, at least for me, it would be too much to look at while on a race track.

I can barely take the time view the lap timer and water temp gauge.

I can look at a gauge. But it's got to be real obvious one way or the other. That gauge has too much information to process in in a race/track scenario. Too much thinking involved.

Just my opinion. But it is a nice gauge for sure.


TonyG

333pg333

Well you could have a gauge or your EMS alert you and you could come into pits to decide what to do perhaps.

toddk911

Anyone done before and after EGT readings after adjusting a/f leaner or richer?

Like example above: 12:1 = 1,550. So at 11.5:1 how much would EGT drop? 11:1? etc.

lejams

What I like the most about this gauge is that you really don't have to monitor anything. The gauge does it all for you and tells you (alarm) when there's a problem.

The Auto select feature - Selects the hottest cylinder, updated every 1 second. An addition you can set hi/low temp alarms. You focus on driving. The gauge does all the work. The only thing it lacks is data logging which probably could be accomplished.

Phil R

http://www.aircraftspruce.com/catalo...pace_logic.php<<< looks like a pretty nice system at a pretty decent price. plus how cool is it to have aircraft quality gauges in your car! I think that would be pretty nice. I just need to think about how that would interface with data logging as mentioned above.

I dont think this is going to happen anytime soon since I assume you need to remove the exhaust manifold to drill and well the bungs. I think a normal mild steel would be the easiest to weld to the stock manifold. Ive heard stainless can be difficult to weld especially to old parts.