1HZ and TD04-15G
VT:
Some comments from a mechanical engineer:
Turbo's and IC engines are both air pumps - the issue is at hand is whether the turbo is matched to the engine in the range
where you are looking for torque improvements.
The consequence of having too small of a turbo, is that the turbo will spool quickly at low rpm, and not pump enough air and starve the engine at high RPM. Ultimate power potential will be reduced. Possibilities of over-fuelling the engine at high rpm exist.
The consequence of having too large of a turbo, is that the turbo will not start boosting until higher rpm. To gain power, you will need to rev the engine. Potential peak power is higher.
The problem with selecting turbo's by the current application engine displacement, is that it assumes the turbo was "perfectly" matched in the original application.. If that was the case, tuners would not be changing out turbo's 'cuz they already would have the best! The reality is, that any turbo selection will be a compromise! And compromizes are all a matter of opinion! Current engine displacement (and max rpm) will get you in the ball-park only, and will not ensure a home run, or even getting to first base.
Selection of a turbo used on a gasser is further complicated by the fact that gassers are air-throttled, and diesels are not. Also, the turbo on the gasser may be sized for high boost and high rpm operation, or low pressure and a wider power band. An example, Volvos of any particular model typically have either high pressure or low pressure turbo options. Even the selection of the transmission type can and will affect turbo selection.
The
only way to
select a turbo is to find the turbo maps, and do the math, and evaluate your needs. An alternative is to copy a previous selection, and assume that you desire the same results..
When I went digging for information, I learned the following:
- I was told Mitsubishi turbo's are easier and cheaper to rebuild than Garretts - this would appear to be true.
- Mitsi plain bearing turbos have similiar efficiencies to ball bearing Garretts, and cost about 50%. This verified by published turbo maps, and online price searching.
- The Mistsi's tend to be smaller diameter and longer than Garretts with similar flow charateristics
- Garretts have a "hole" in their sizes, just where one would like to pick one for a 1HZ. The big TD04's and small TD05's fit right into this hole.
- A TD04H-15G is just about the perfect size for a 1HZ, IMHO, if you are looking for lower end torque improvements like I am - IIRC, peak efficiency of that turbo should be at about 2400 engine rpm, and the turbo may choke the 1HZ above 4000 rpm (my automatic never shifts above about 4100 rpm now anyway). If you are looking for higher end boost, a TD05 is in order. Or a Garrett GT28.
- Like Tapage says, the info I have found on the KKK26's would indicate that they are in the range of sizes that are useful for the 1HZ.
- The Volvo TD04H-15G that I have, was very easy to "clock" for the 1HZ. It required the drilling of one, maybe two - 1/16" hole(s) for the locating pin(s).
The reality is, any turbo selection is going to be a compromize - you can buy a kit and see if the vendor's compromize matches what you want, or try a few different turbos and see which best matches what you want. Almost any turbo is going to help somewhere in the power curve, unless it is grossly oversized.
Also, remember Paredo's law - 80% of the results will come from 20% of the effort/spending - if you are looking to get 100% of the possible output from your engine, you will have to put in 100% of the effort or money. There ain't no free lunch!
Personally, I would rather have a turbo that is too small and makes more torque down low, than one that requires me to rev my engine.. But I was born in the mid 50's, and your needs may differ! (
If I was looking for ultimate power, I'd buy a 572 chevy and junk the 4.2L diesel!:whoops: - I'm not!)
My flame suit is on!
Jim
I love this .. ! 
