I am not sure about this but, I was always told if you want a true EGT reading the probe needs to be in the exhaust manifold...hence Exhaust Gas Temp...what you are getting now are "TGT"...Turbo Gas Temp.

From what I can understand from reading your post this has been happening for awhile? Maybe move the EGT to the exhaust mani?

Just an idea.

 

check your cam positioning sensor timing..........if that is off that will show as high EGT's.........

 

The CPS was installed by instruction from the Toyota service manual and then after the engine was operating temp the timing was set to 10 before TDC. Of course it wouldn't hurt to recheck but I thought when the CPS was put in incorrectly the car would have operating issue such as a distributor being out of tooth and running sluggish or having starting issues.

 

dbsupra

Brace yourself, I've gone off on a rant.

The highest combustion temperature occurs at the perfect stoichiometric air/fuel ratio. Too much air not only adds oxygen to lean out combustion, but also inerts (about 68%). The inerts take some of the combustion energy to heat up and, at certain cylinder temperatures, also burn (NOx for example) releasing varying amounts of energy or react consuming energy. The heat created is also quenched based upon moisture content/humidity as energy is required to vaporize the water.

Additionally, reversion into the combustion chamber from cam timing or back pressure affects overall cylinder temperature by reducing the amount of oxygen available, lowering cylinder temperature and generally reducing NOx formation. This is the reason for VVti. You'll notice VVti engines do not have an EGR system.

So, the point of all of this is to indicate that the final exhaust gas temperature is really only a potential indicator of A/F problems. It is a good indicator of fuel, ignition timing, backpressure or valve timing issues. It is an excellent tool to indicate the likelyhood of cooking a header or heat stress cracking a turbine housing.

You list some good potential items to look into. Here's a couple more.
1) Fuel carry over. This would suggest too much valve overlap blowing fuel through the combustion chamber before the exhaust valve closes. Are the EGTs extremely high? Does the turbo glow after two trips down the 1/4? Do you ever have exhaust backfire?
2) Overall timing too low. This would suggest that the intake valve is not open enough when fuel is injected. This would cause fuel to pool on the intake walls and would lead to leaner combustion. This may not be indicated in A/F ratio because the O2 sensor only indicates exhaust oxygen, not unburnt fuel. The use of the term A/F meter is almost always wrong. Is your injector duty high for a given A/F at your power output? Has the head been milled skewing the cam position sensors base timing setting?
3) More power = more fun = more energy = more combustion = more heat. Your EGT may be normal for your power level.
4) Backpressure. Is the the turbine housing undersized? Downpipe? Are the cats, if present, in good unmelted condition?
5) Intake temperatures. While a minor factor can contribute by causing knock which jacks up the ECU into retarding timing. Next thing you know you have problem 2.

I would start with backpressure problems, then try bumping base timing down 1 then up 1 degree, then try resetting the ECU on a cool day, then mess with timing gears.

Let us know how it turns out

BTW, cool looking kid. Is he a gear head too?

 

Excellent reply jkturner

I am also having the same problems with High EGTs and rich A/F. My wideband is reading about 10.5-11 at WOT (sometimes richer) and the EGTs will climb up to about 880C (sometimes 900C)...it will on get up that hot for a second then drop back down to 800-820C or so. My CPS is set to TSRM specs and the timing is @ 10 degrees BTDC. Although I am running a stock CT26 with a non ported elbow and stock IC w/hardpipes. I have heard from some knowledgable people that the stock IC could be a cause for the high EGTs. But in dbsupra's case he is running a Spearco...I believe. I dunno, maybe if I open up the exhaust with larger elbow and upgrade ICs it will help out my temps.

Josh

 

DBsupra, if those readings are with the probe at the turbo inlet (exhaust housing) imagine how high it is upstream. The recommended location of an egt probe is ~3 inches from the head port. I thought mine is high and I was kinda getting concerned, .876 lamda is just approaching 12.5:1

Kinda like what's going on with everybody else but a little lower overall, my egts will tend to rise at high rpm (above 3000) no boost, situations. This is with ideal a/f's at those conditions. Under boost though, most of the time, it starts to go down. Not always but a/f's are always consistent.
Here's a note from Chris@motec, it does makes sense but still left me with questions How high can we go and do we have to go that high?

There is a correct EGT for each engine. However, they do not correspond from one engine to another. Therefore there is no "correct" EGT value. They do not always read hotter in lean conditions and cooler in rich condition. There is too many variable from type of sensor, to sensor location, to external cooling and engine characteristics. For EGT's to be useful you have to develop your own theories based on some dyno runs, then many track sessions.

sorry there isn't any hard concrete conclusions. You're far better off with a lambda sensor than and EGT.

cheers,
chris

HTH.

 

So, basically an EGT gauge is useless in terms of A/F ratios. EGTs could be high because of a lean condition and they could start to decrease because of an extreme lean condition or they could be high from an extemely rich condtion. It seems EGTs should not be used as guide for A/F ratios at all, but only as a warning before something melts.

I have to hook the EGT gauge up to the Profec and log them together vs. RPM to see if there is any correlation.

 

check your cam positioning sensor timing..........if that is off that will show as high EGT's.........

I agree.............I installed a new TMG belt set the tmg to 12Deg and after 800 miles it was at 14 and the engine was running warmer than normal in cold weather.....................backed it down to 12Deg and noticed a 150 Deg drop in my EGTs

 

So, basically an EGT gauge is useless in terms of A/F ratios.

Not true at all.. A/F ratio has the greatest impact on EGT out of all the factors that effect EGT. So yes... it is useful. Besides, it helps to keep you from blowing up motors.

All jt2ma71 and jkturner were trying to say is that 2 identical 7M's running the same A/F ratios would not have the same EGT's. The EGT's would be "similar" though...

EGT's are not identical from cylinder to cylinder on the same motor, much less from similar motors.

 

Not true at all.. A/F ratio has the greatest impact on EGT out of all the factors that effect EGT. So yes... it is useful. Besides, it helps to keep you from blowing up motors.

All jt2ma71 and jkturner were trying to say is that 2 identical 7M's running the same A/F ratios would not have the same EGT's. The EGT's would be "similar" though...

EGT's are not identical from cylinder to cylinder on the same motor, much less from similar motors.

I did NOT say A/F ratio did not impact EGTs....I said EGTs are useless in terms of A/F ratios, as they are not directly proportional (ie As A/F ratio is leaned out EGT get hotter.....that is not always the case). I understand that EGTs are mainly affected by the A/F ratio along with other factors.

 

I am another who has high EGT's yet rich A/F.
For my car, I have two suspicions...
1. spark issue. I suspect a degree of blow-out at higher boost levels. I plan to gap down the plugs to 26-27 and see how it goes. (unburnt fuel will raise egt's... but will the head see that temp?)
2. fuel. My 550cc fuel injectors maybe nearing there maximum.

Please keep us posted on your progress regarding this issue.

Jason

 

Well, i was experiencing the same problem. It took me forever to figure it out. Actually dr jonezz figured it out after looking at it for a while. My cam position sensor was off 1 tooth. Now dont get me wrong, im no dumbass, and i have timed many-a-supras. It was just a honest simple mistake. So do yourself a favor and double check it. I know it sounds stupid, but make SURE your using the same mark on the crank pulley. good luck man!!