Turbo Exhaust Temp, is it important and Why?

[almc2242]

If you have a turbo installed on your RAV4 3SFE engine. Is it important to have an Exhaust Temp Gauge in your gauges, and why? Hot means lean

[CrawlingEye]

hot means rich.
rich = fuel burning in the exhaust manifold
lean = valves taking extra heat

remember, ideal combustion is 14.7-1, and the more fuel the cooler your engine will be, so tuning has to be done within your boundaries. don't want to melt a valve, don't want to kill the cat.

[88 LE]

^ 14.7:1 is stoich.

For force induction you want a richer mixture. 12.5:1 - 12.7:1 is good. Some people will even run it at around 11.6:1.

[bgrieger]

egt tuning is the po' boy sandwich of tuning...everyone has done it, few are all that good. Wideband and time on the dyno are the trick to getting it right, and you completely ignore the EGT. Never a concern when tuned this way, unless you got something really f'd up happening, and the proper tuning process will show that right away.

[Flashmn]

hot means rich. <- hot means lean actually...

EGT and CHT gauges are both your friends

[white90dx]

Lean = hot EGTs, rich = cooler EGTs... this is all to a point, of course. (EGTs will be VERY cool if there is not enough or too much fuel to ignite, for example...)

An EGT gauge is not great for tuning, but helps. Its more important to tell you if your motor is about ready to explode. Do not let EGTs get above 1600*F if you can help it.... and your car should run much cooler under cruising.

-Charlie

[CrawlingEye]

Originally Posted by Flashmn

hot means rich. <- hot means lean actually...

EGT and CHT gauges are both your friends

Not for exhaust.
For the head and combustion chamber, sure.

[almc2242]

The bottom line here is; yes, it is important but not critical. As long as it runs leaner, the better. I guess fuel economy will dictate how much lean.

[Flashmn]

Not for exhaust.

ofcourse for exhaust, if the combustion process is hotter than normal, exhaust gasses are hotter than normal.
Thats how pilots tune the engines when they lean it off, they turn the mixture leaner until the exhaust temps start to rise and then adjust it back to proper setting. Go learn the basics before you start talking out of your ass.

[almc2242]

Will a Greddy E-manage computer running piggy back [or like we say in the island, Riding Shoot Gun] keep this issue in check? The lean/rich, cool exhaust issue.

[88 LE]

^ I believe the E-manage has a wideband O2 option.

TonyTheTiger would know more about it. He had a E-manage.

[CrawlingEye]

Originally Posted by Flashmn

ofcourse for exhaust, if the combustion process is hotter than normal, exhaust gasses are hotter than normal.
Thats how pilots tune the engines when they lean it off, they turn the mixture leaner until the exhaust temps start to rise and then adjust it back to proper setting. Go learn the basics before you start talking out of your ass.

You're failing to realize that more fuel cools combustion.

For reference, here's a little article that you may find informational from Modified Mag on basic tuning principals (something that you seem to need to read):

"when cruising down the highway we would like to aim for an A/F ratio of 14.7:2-15:1 to keep our mileage up and our environment clean. But what happens when you hammer down and hit 15psi of boost? If you ran that same A/F ratio chances are you'd wind up on the back of a tow truck with a melted valve or piston. Heavy engine loads need a richer air/fuel mixture. Naturally aspirated engines can run 12.5:1 to 13.5:1 air fuel ratios under full power. Turbocharged, supercharged, or heavily dosed nitrous engines will run from 11.5:1 to 12.5:1 air fuel/ratios. An air fuel ratio that is richer (more fuel) than 14.7:1 slows combustion and the extra fuel helps cool the charge."

so far, this should all seem obvious to you.

"For reference let's pretend we have a 2.0L turbocharged motor running at 15psi at full load. We'll start on the rich end and work our way toward the lean end. Starting at an A/F ratio of 10:1 we would notice puffs/clouds of black smoke out of the tailpipe and a very rough powerband as we make a dyno pull. Horsepower would be down and the engine would be sluggish. This mixture causes slow combustion (less power) and incomplete burning of fuel. Contrary to what most people think, exhaust gas temperatures go up in this condition because of the slow combustion and the chance of some of the fuel burning in the exhaust manifold. As we lean out to about 11:1 we notice the exhaust starting to clean up and the car making more power on the dyno. EGT's come down and the combustion process speeds up exerting more pressure on the pistons (more torque/power). As we approach an air fuel mixture of 12:1, there is little trace of unburned fuel in the exhaust (black smoke) and horsepower picks up across the RPM range. The power graph is smooth and the added power comes from a faster combustion process. Going leaner and approaching 13:1 now starts to bring EGT's back up as the combustion is quicker and hotter, also givinng us an increase in horsepower. At this point the leaner combustion process is inducing a lot of heat stress inside of the cylinder. The majority of the heat gets transferred to the edges of the exhaust valves and the top of the pistons. Any leaner and we now run the risk of melting a valve or piston and ruining the engine. Obviously for safety sake its better to stay on the rich side than the lean side. To correctly measure A/F ratios we need what's called a wide band oxygen sensor. We'll talk more about this sensor in the next few paragraphs."

Now with this said, I certainly wouldn't let you tune my vehichle.

[zoni]

almc whats up with all these like rhetorical question threads... or its like a statement that you want to make everyone blow up about...

[Flashmn]

You're failing to realize that more fuel cools combustion.

And where did I state otherwise? Nowhere, because I didnt. As far as I recall saying from the quote you so kindly posted, I said pilots LEAN the mixture UNTIL the exhaust temp rises, then they adjust it to a proper level. WHERE THE MIXTURE IS NOT LEAN ENOUGH TO CAUSE AN ENGINE FAILURE. and that can be seen on the EGT.

The cooler the combustion is the cooler the exhaust gasses are and the cooler the engine stays, the cooler the head etc are.

almc whats up with all these like rhetorical question threads... or its like a statement that you want to make everyone blow up about...

EXACTLY , when the people who dont know jack-shit start to speak out of their ass and make the ones who actually know something look like fools. For reference I'm working on a degree in motorsports engineering, so knowing this stuff is basic.

Now with this said, I certainly wouldn't let you tune my vehichle.

I wouldnt even want to tune your vehicle

PS. I got lazy and didnt have the mental strength to read the essay you just posted... Next time please so summarize it. :ihatespam

[Tony the Tiger]

EGT's confuse everybody...

Isn't it funny that after all this oohs and ahhs, yap yap yada yada, still no one mentions anytihng about ignition timing.

I can probably say that ignition timing has the GREATEST impact on EGT's.

You can run rich or lean all you want, but once you touch that timing, it is all going to change. I can make my EGT's shoot up to 1600 deg F without touching any fuel settings. If you have heard about anti-lag, then you have heard about retarding ignition timing This type of heat actually doesn't melt anything in the engine...the heat is strictly after the exhaust valves and in the manifold/turbo.

It is tricky... if an engine is tuned with conservative ignition timing and running about 12.5:1 A/F yet my EGT's are on the high side, what is the problem? It is too much/too less fuel? Usually it is neither because the timing is probably too retarded and causing late burn and put heat on the manifolds.

I can tune an engine to run with low EGT's, rich A/F's and still be able to blow up and melt the engine. How? Just put shit loads of timing. You see, once you realized how inconsitent EGT's are, you also realize that why tuners nowadays don't even use EGT readings anymore. With current wideband technology, it is safe to assume that the engine runs correctly with a common range of A/F's and a common set of ignition tables.

So onto the argument, does rich A/F increase or decrease EGT's? Both. I can run a very rich 10:1 A/F and jack up the timing and it would decrease EGT. Back down the timing to create an incomplete combustion state and EGT's would rise. If I lean out the engine and back down the timing the EGT's will also increase. Timing plays the most important role here.