In reply to Fueled by Caffeine :
1200-1500 is pretty normal, but 1650 is very easy to get to on many low power to wt packages. Like a 1.6l turbo suv.
For the rest of you, these seem hot, but they are done to not hurt anything, and will run for hundreds of hours on a dyno with no issues.
The higher compression ratio (or rather the expansion ratio) in a diesel engine means that it extracts a lot more of the energy out of the combustion than a gas engine does, thus the EGTs are significantly lower. I know this used to cause problems for people running engines hard with turbos designed for diesels, but I've never tried it myself. Might only be some of them, might not. Might be OK in a street car, might not. Basically just a heads up that the two technologies are significantly different in this regard, and it's worth paying attention to before trying to transfer parts designed for one to the other.
Note also that turbos are "sized" in two dimensions, both of which contribute to power ratings. They care about volume of intake air on the compressor side (which directly translates into horsepower) and also about pressure ratio across the compressor (boost). A 2L engine running 2 bar of boost has 6 atmosphere-liters of air coming in. A 3L engine running 1 bar of boost *also* has 6 atmosphere-liters of air coming in -- same volume at the compressor intake and in theory those two engines will make similar power numbers, but 50% higher pressure ratio on the smaller engine meaning that those two engines will ideally want different turbos.
In reply to alfadriver :
I think the other thing is.. I'm 10 years out of this game.. Drawing on some dark corners of my memories now.... :-) I could be entirely wrong.
In reply to codrus :
It's tough to believe that there are actual issues with the turbo due to temps. I'd imagine that you have lack of oil flow for the bearings, or compressor surge before you get into any metallurgical issues with the actual parts.. Lack of sufficient oil flow kills more turbos than any other root cause...
In reply to codrus :
The other thing to add- diesels lower exhaust temp isn't only because of compression. Heck, it's not even the leading reason- it's that they run lean all the time- which lowers exhaust temp more effectively than going rich.
Fueled by Caffeine said:In reply to codrus :
It's tough to believe that there are actual issues with the turbo due to temps. I'd imagine that you have lack of oil flow for the bearings, or compressor surge before you get into any metallurgical issues with the actual parts.. Lack of sufficient oil flow kills more turbos than any other root cause...
I know the variable geometry turbos do NOT like gasoline EGTs, dunno how common that is in diesel turbos.
Dunno about the metallurgy, but things like seals, gaskets, fasteners, etc are all designed with certain expected temperature ranges, thermal expansion ratios, etc, and going outside those expectations can produce unexpected results. Again, may not be much of an issue on a street car that only sees occasional excursions into high EGTs.
alfadriver said:In reply to codrus :
The other thing to add- diesels lower exhaust temp isn't only because of compression. Heck, it's not even the leading reason- it's that they run lean all the time- which lowers exhaust temp more effectively than going rich.
At partial power, sure, but I thought they ran rich at full power?
The expansion ratio of around 18:1 will suck a huge amount more heat out of a combustion mix than the ~9:1 in a typical gasoline turbo motor.
I'll have to check but I don't think they are that rich- the mixing with the air is so poor that there's not much of a point to be rich.
Yes, 18:1 will take more heat out, but not double, and not really a huge amount. There's also the issue of kind of combustion- diesel is (for the most part) constant pressure combustion, whereas gas (for the most part) is constant volume combustion. And constant volume is considerably faster burning- which is another huge reason gas burns hotter than diesel.
A lot of the reason for that high of compression for diesel is just to get the fuel to burn.
Is it a bad thing that the last few set ups I’ve thrown together have gone something like “that looks like it will work “
td04 off a 2.5 Volvo works great on a 2.0.
T3 off a Saab works great on a 1.5 tercel.
T3-gm3 off a 6.5 gm also works on a 2.0 if it can flow enough.
Don't overthink it, the truest thing in maximum boost was something to the effect of “the wrong boost is better than no boost.”
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