5 Posts - Page: 1

Turbo diesels and heat


Basic background.
upgraded my v8 chev Diesel with a turbo. Went and saw my local turbo man who sized up a turbo for me based on my specs.
I decided to go conservative aiming for for 10-12 psi at 3000rpm
He supplied a custom to4 with t3 internals. Exact ar ratios I dont have right now.

I was lead to believe that in a Diesel application that overall a turbo should provide some cooling benefit , measurable by the egt. Na diesels can regularly hit 600degree egt whereas turboed they float from nothing to a max of 500. (Given an equal situation )

Since finishing the upgrade I've had significant overheating problems that I didn't have before.

My question is... would having a conservative (read potentially undersize ) cause overheating issues thru additional back pressure??

Before anyone tells me to goto another forum I have asked here to try and get some general turbo knowledge that I can apply. Im also asking this question elsewhere

Could it be leaning out thus making more heat ?
What have you done to give the engine more fuel under boost ?
Ok deisels work the opposite to petrol motors. The more deisel you wind into them the better they go. Not so much boost. It helps, but really what boost is allowing you to do is wind more deisel in.
What causes heat is also deisel. ie if she is getting up there in egt's, you;ve got too much fuel wound in.
You say overheating problems; do you mean egt's or water temp??
If it's water temp issues you could be having issues with engine bay latent heat being too high, maybe need to look at allowing the heat to escape.
If you mean egt's, you need to look at the tune of the pump. Intercoolers will help also.
Generally you don't want to exceed 550. This will be debated ENDLESSLY though, as will the positioning of the egt sensor. You'll never get a consistant answer on these.
To an extent your right about turbo's cooling your egt's. Its more a case of 'it's not the boost causing high egt's'. ie your better off hauling heavy loads or up steep hills with the engine reving and on boost, then trying to climb low in the revs on low boost.
Tuning of the pump is critical on these things, and should not be played with. Things go boom too easily. Let a pro tune your pump.
Hope this helps
Cheers, Rob
Thanks for that feedback rob.

Pretty much the only tuning method available to diesels is the fuel pump.
I have been reluctant to wind in more fuel as I know that more fuel will increase egt's and I already have high water temps.
You are also right that tuning diesels needs finesse as too much fuel can quickly melt pistons and generally break stuff.
My egt's sit well below 300deg during normal use and spike to about 450deg during hill climbs and regular work loads and can hit 500deg. after prolonged heavy right foot work. They then drop off quickly once the load is off. This is all expected.

I havent used the most common turbo option and most of the chevy diesel nuts didn't have much to say about the expected result.

The issue is high water temps.
I have heard that too much back pressure before the turbo can significantly increase /affect temps both egt's and eventually water temps as the heat has to soak somewhere.

If I have a turbo that is too small would that increase back pressure resulting in more heat from the exhaust being soaked by the water rather than escaping out the pipes

A good and knowledge friend suggested that since I have added a bonnet scoop to feed the top mount intercooler that that will have upset the airflow and be causing heat to stick around in the engine bay rather than be flushed down and under the car.

My next option is to upgrade the radiator to a bigger unit. What bugs me is before the turbo upgrade overheating was not a problem so im reluctant to throw another $500 at the Pootrol when the dat deserves it.
I heard bigger radiators are important for turbo diesels as the exhaust side of the head gets more heat soak from the manifold and turbo rather than just looking at egts. Are you happy how she goes now do you notice any flat spots or pinging of any kind, definitely would invest in a good tune unless the expert already suggested a bigger rad.
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5 Posts - Page: 1