EGT's with your 1HD-T

[bsmith123]

egt

yes I figured that ---would just show how much soaked into the head and the EGT should keep you from getting to the point to worry about that I suppose

 

[crushers]

ummm, that gauge would react similar to your coolant gauge ... slowly and the warning would be WAY too late to matter...

 

[asutherland]

Post turbo I'm running 500-700 F during normal city or highway driving, and on big hills (such as the Coquihalla or the Sea to Sky Hwy, not the Malahat for you wussy islanders) I'm hitting 1,000 F or just over, MAX. As soon as I see it go above 1,000 F I dip off the throttle and climb the rest of the way slower.

I have a stock-ish setup, though the fuel has been tamperered with by the PO (I reset it to mostly stock, as far as I can tell). It has a 3 inch aftermarket exhaust (again, PO)

 

[sandcruiser]

more info:
on highway climbs I've been hitting higher egt numbers

I advanced timing, that shaved about 100 degrees from egts
I reduced fuel slightly and added boost controller at 14psi, that took another 100-200 degrees off and gave me more power and better passing behavior without any noticeable downside around town (maybe a little less smoke, maybe a little less off-the-line oomph, but hardly any).

next step is 3" exhaust....

then an intercooler

 

[Jbone]

You guys have me thinking now!
I have a stock HDJ 81 with H151 manual tranny. There is talk of bone stock vehicles not being capable of frying themselves but might that change with manual tranny? I frequently climb hills on the highway at 22-26 hundred rpm in 5th without any issue, from what you guys are seeing with your pyro's should I be dropping into 4th and reving 3 grand+ ? Looks like I am going to have to get myself one!

 

[IanB]

The only way to know what's going on with your truck, is to get your own EGT gauge. It's a great investment for these trucks, motors are expensive in comparison.

 

[yotahed]

EGT is your Exhaust Gas Temperature as it leaves the head and enters the turbo (or it SHOULD be measured this way)
It is important to monitor because:
Pistons are mostly alluminium and WILL melt down at excessive temps.
Turbine wheels and seals can only take so much heat. Sometimes they melt, explode, seperate from the shaft. I've seen many different scenarios.

Post turbo temps are quite inaccurate and can have great variance from actual pre-turbo temps. 3 inches downstram from the turbo can have a variance of 200*F or more. There is no calculation for post turbo temps, they are a guess at best, and your exhaust size, turbo size, drive pressure can all affect this.

The key is to get the probe to sit in the center of the exhaust stream and close to the turbo inlet. Not in the EGR port, not in a single runner(unless you have one in all of them), and not after the turbo. If your going to spend the money on a pyro, you obviously care about your motor, so take the time to do it correctly.

Sorry for the rant, but really, you wouldnt buy a sick intercooler and install it in the trunk, would you?

A good rule of thumb is keeping temps below 1200-1250*Fahrenheit (around 650*C), as exceeding this temp for any amount of time is rolling the dice.
I rarely push mine over 1150*F

I shake my head at the big diesel guys that constantly push 1600*F. And they wonder why their motors catastrophically fail after investing a lot of $$$ and time. It all how you drive it, make it last, or.....don't.

my .02c

 

[Dougal]

I had the head off my Isuzu a few months back and had a chance to inspect the pistons for any signs of heat damage. I run 750C sustained EGT for minutes at a time and have seen 900C in moments of inattention when towing heavy loads (rpm dropped, boost dropped, EGT's spiked).

Absolutely no heat related damage.
I'm not using this example to recommend others follow. Just to show you need to get it very wrong to melt pistons. My readings are with a 3mm probe (fast acting) in the dead centre of the turbo inlet. I am confident in them.
The worst thing people can do is take dodgy readings as gospel.

 

[NetJunky]

Just got my rig running and did some freeway driving. Temps are running in the 225-275 range and I need to check if the sensor is after the turbo which I assume it is.

 

[Rob1983]

'91 1HDT, GTX3071R, maxed standard 12mm pump (only for another couple of weeks ), XXi w2a intercooler, 3" straight exhaust, EGT probe is right behind the turbo flange on the dump pipe, 17:1 AFR prespool, 23:1 AFR at full boost, currently running 24psi (1.65 bar), EGT's never go over 400*C in 40 deg ambient temps, even 5th gear flat up hill (manual trans). More boost without increasing fuel will drop EGT's and raise AFR, when I bought the car, the old wastegate was jammed, as a result, when the fuel was turned up it made 32psi @ 30:1 AFR, but wouldn't go over 380*C, also had less power thanks to the lean fuelling. Will be interesting to see the changes in EGT once the new (12mm high flowed) pump goes on, will be running 17:1 AFR right through at 28psi (1.93 bar) or so for the power setting, and 33psi (2.27 bar) at 23:1 AFR or so for daily drive/towing

 

[Dougal]

'91 1HDT, GTX3071R, maxed standard 12mm pump (only for another couple of weeks ), XXi w2a intercooler, 3" straight exhaust, EGT probe is right behind the turbo flange on the dump pipe, 17:1 AFR prespool, 23:1 AFR at full boost, currently running 24psi (1.65 bar), EGT's never go over 400*C in 40 deg ambient temps, even 5th gear flat up hill (manual trans). More boost without increasing fuel will drop EGT's and raise AFR, when I bought the car, the old wastegate was jammed, as a result, when the fuel was turned up it made 32psi @ 30:1 AFR, but wouldn't go over 380*C, also had less power thanks to the lean fuelling. Will be interesting to see the changes in EGT once the new (12mm high flowed) pump goes on, will be running 17:1 AFR right through at 28psi (1.93 bar) or so for the power setting, and 33psi (2.27 bar) at 23:1 AFR or so for daily drive/towing

EGT sounds too cold. Where is the probe?

 

[ozwallaby]

EGT sounds too cold. Where is the probe?

Says "EGT probe is right behind the turbo flange on the dump pipe".....

 

[Rob1983]

EGT sounds too cold. Where is the probe?

Like it says in my post, right behind the turbo flange on the dump pipe. I run all digital gauges including AFR, so I'm not guessing where the needle might be sitting on an analog dial, like I said, flat in 5th up a long hill, it's lucky to go over 380*C

 

[Dougal]

Like it says in my post, right behind the turbo flange on the dump pipe. I run all digital gauges including AFR, so I'm not guessing where the needle might be sitting on an analog dial, like I said, flat in 5th up a long hill, it's lucky to go over 380*C
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You do realise post turbo readings are useless?

 

[Rob1983]

You do realise post turbo readings are useless?

Not completely useless, but that's why I have the AFR gauge, that's even better than having a pre turbo EGT

 

[Dougal]

Not completely useless, but that's why I have the AFR gauge, that's even better than having a pre turbo EGT

You can hit dangerous egt with what is normally a safe a/f too.
I've got a vehicle knocking on 750C with 21:1 sustained.

Why even fit egt in the dump pipe? It's only a little more work and you get a useful reading. Post turbo temps drop lower the harder turbo is working. While p re turbo temps keep climbing.

 

[Rob1983]

You can hit dangerous egt with what is normally a safe a/f too.
I've got a vehicle knocking on 750C with 21:1 sustained.

Why even fit egt in the dump pipe? It's only a little more work and you get a useful reading. Post turbo temps drop lower the harder turbo is working. While pre turbo temps keep climbing.

It came to me that way, if I'd done the original install it would have had a pre probe. Will probably chuck a second one in next year when I swap to a Gturbo. 750 pre is about 550 post? I'd be worried at that point too

 

[Dougal]

It came to me that way, if I'd done the original install it would have had a pre probe. Will probably chuck a second one in next year when I swap to a Gturbo. 750 pre is about 550 post? I'd be worried at that point too

There is no fixed difference from pre to post. It varies with a dozen factors. It can be 300C.

I don't worry about 750C as long as it's a true measurement. I've seen my pistons after doing this for a long time and they survived the temps fine.

 

[Tapage]

interesting setup ..

 

[Hulsty]

It came to me that way, if I'd done the original install it would have had a pre probe. Will probably chuck a second one in next year when I swap to a Gturbo. 750 pre is about 550 post? I'd be worried at that point too

Post turbo EGT's are as useless as tits on a bull. I've got some data somewhere on a 1HDFTE fitted with post and pre turbo EGT gauges, showed some interesting things. At one point it was 800c pre turbo and only 500c post turbo