Stock 12HT with 700C+ EGT? (1 Viewer)

[dousty]

Stock 12HT with 750C+ EGT?

I am after some advice. I have a 12HT in a 60 series. The engine is unmodified and the vehicle has a 2.5" exhaust that is around 8mths old.

I have fitted an Autometer EGT to the manifold. I find I can surpass 750C when climbing hills on the highway in 4th gear. If I change to 5th gear the EGT will drop to around 650C and will not climb again unless engine speed increases, even with full throttle.

So, my EGT is really high when engine speed is over 2500rpm and under load. All anti tamper tags on the fuel pump are in place. Exhaust is near new and fitted with a non restrictive muffler. Intake is standard with new air filter. Rockers were adjusted to spec around 4mths ago.

This problem hasn't just occured, I found it as soon as I fitted the EGT guage.

If I increase boost to 13psi, EGT's under the same conditions will drop by 50C.

What could be causing these high EGT's in my stock 12HT? I wanted to increase power but at the moment there isn't any room.

Dribbling injectors? Unknown age
Exhaust restriction? New exhaust but maybe 2.5" is restricting flow at high engine speeds?
Tight exhaust valve rocker lash?
Turbo passing oil into intake and increasing cylinder temps? Engine doesn't appear to consume any oil although there are light traces in take tract pre and post turbo

 

[Hulsty]

Its probably just how it was from factory. I have a 13BT, stock with a 3'' exhaust, all the anti tamper tags are in place on the pump. Holding 14-15psi at 3000rpm I hit 670C pre turbo. I drove it around for awhile on stock fuel and boost, no EGT gauge, hate to know what the EGTs would have been on some of the really long hauls I have done.

 

[Radd Cruisers]

They tend to increase fuel a little over time. Turn down the fuel screw a little and you will be good.

Also, check your valves and your timing.


~John

 

[Stone]

Wow...that's pretty high...assuming your gauge is reading correctly.

 

[Dougal]

It's not unexpected.
What altitude are you at?

*edit* Okay, NSW so that's pretty much sealevel. I think it could be just how things were. More modern engines run leaner and cooler to lower smoke. More boost and an intercooler will give you enough headroom to add more fuel.

 

[dousty]

Wow...that's pretty high...assuming your gauge is reading correctly.

Agreed. It's on Autometer Cobalt series and I am pretty confident/hope that it's accurate.

 

[dousty]

It's not unexpected.
What altitude are you at?

*edit* Okay, NSW so that's pretty much sealevel. I think it could be just how things were. More modern engines run leaner and cooler to lower smoke. More boost and an intercooler will give you enough headroom to add more fuel.

Yeah at sea level. I ordered an ebay special intercooler t'sarvo. Will take me a little while but I'll get it fitted up and see how it goes. I might even change the exhaust to 3" mandrel and incorporate a divorced wastegate dump pipe, though that might be a bit of overkill.

I'm planning to change the compressor housing and wheel to 7mgte if I can find an old turbo. Also I am thinking of changing the "throttle body" to something of a larger diameter. I have removed the heating grids and ground out the housing to increase flow but the rest seems pointless while retaining the little shutoff valve throat.

All these mods could be worthless though, unless I can get egt's down and make some room for increasing the fuel.

 

[blis]

i'd check the valve clearances...

 

[Tapage]

I would add to the list service to your injectors ..

 

[relaxedcruiser]

Hi Dousty - have you fitted the intercooler ? - wow just realised that the thread is 14 years old....I have for ages searched for unmodified 12ht EGT data.
I really would like what the manufacturer thought back then which temperature is regarded as sustainable. It's a lot of guessing around about those EGT.
some say don't go over 600°C others say 750°C is just fine...
I personally have always - well since fitting the gauge -stuck to max 600°C as I just can't afford be it money or time wise to harm my engine - in an ideal world I would love to build a second spare engine and swap it over once it's finished.
I have just fitted an intercooler ( The Official 12HT intercooler thread ) and that helps big time with the EGT.

 

[AussieHJCruza]

Sustained 750c is fine in a direct injection diesel engine. I ran my 1HDT to 900c a few times goosing around on the dyno, I wouldn't recommend making a regular habit of it but never any indication of engine distress.