why is it that when you do the math for your engine and find a good compressor map, its always the one that is one size larger that people report is the 'best' one offering pull all the way to redline, etc?

for a B18C1, 8000rpm redline, the T04E with .54 trim looks ideal at 6, 8 and 10psi.

people recommend the .57trim though...why would it be better when it seems that you're effeciency is falling off quickly as you approach redline?

could there be somthing in the math that we are not accounting for? i always see anyone calculate the best turbo config, then go install it and then end up with something bigger. (not always, but often i see this happen to people who did their homework).

Joe

 

People always wanna go larger.. "bigger is better, dont ya know?!"

I agree with you.. people should stick to compressor maps.. because it usually shows you the best turbo with good spool-up and good power.

I actually think the 50 trim would be better on the C1. The line goes right through the efficient part of map on both maps.. but the 50 trim will spool quicker. Still, I'm not sure why people go higher.

 

falconGSR, that is a very good question. I have read and plotted out compressor maps while researching the proper turbo for my D16Y8. I came to the T3 with a 60 trim compressor wheel. Do your method for finding the right compressor for the D16Y8 at moderate (7-12PSI) boost levels and report your results. Ideally you want something that will hit redline at full boost while still at max efficiency. It makes sense to me, because when you are out of max effiency you make more heat. Why make more heat at max boost than you need to?

 

Yup. That is what I have found.

 

I asked an RX-7 buddy of mine. His answer: loss. intercooler, piping, intake manifold, throttle body losses. It all adds up and separates the theoretical numbers from the real world numbers.

Joe

 

well of course that's true.. but this is a good place to start on. Changing the T-body, piping sizes, intake manifold, all change the engine's characteristics because you're changing the way air is getting into the engine. If you worry about all that, you'll never get an idea what size turbo is good for your application.

 

ugh.... engineers...

 

So MarkC, which Turbo are you running now? I remember you saying that the 48 was your favorite for the street but the 54 gave much better top end, and you thought that the super 50 might be the best compromise. Would you provide some more info, when they started to boost, reached max boost, what kind of 1/4 you ran, how the top ends where, etc.

Thanks. I am finally about ready to order my Turbo. If I had known all of the distractions that would take my money along the way of building a custom kit I would have just ordered the Drag in the first place.

 

your buddy is right,
when most people size a compressor your only calculating the airflow rate with out an intercooler. If you wanted to be thorough and accurate you would also have to:

-calculate the Intercooler PSI loss, and efficiency and airflow rate through the IC
-IC endtank efficiency
-calculate the air filter PSI loss (some filters can be restrictive)
-take into account the number of bends and turns in the IC piping, too many abrupt changes in the flow path results in PSI lost
-many other variables

you get my point though there is some "give and take" when your calculating the above variables, a more efficient IC gives you more power, air filter PSI loss... you lose power.

you can calculate the compressor requirement very easily, but everything else is confusing as hell. for me any ways

[Modified by BlueShadow, 6:09 AM 12/12/2001]


[Modified by BlueShadow, 6:10 AM 12/12/2001]

 

I think alot of people find that out.

art