Turbo explanation? What do the sizes mean?
 

I'm trying to learn about turbos and decide what turbo is best for me and what I want out of my car. I have a 93 fd rx7 stock. I will be getting supporting mods obviously but I want to pick the turbo first. From what I read GTX35r seems like what I'm looking for. Fast spooling, great power (I want 400hp), and it's not having to boost so much to make that power. But now it's getting to trim this and compressor that and that housing is this? I don't know what any of that is?
Like smaller/larger housing does this?
This means more low/top end?
Smaller or larger trim is this?
Small/large Compressor wheel helps with this?
Not sure which way these things go? Lol
If you guys can kindly explain this that would be great, pictures help too! Lol
Thanks

Interested in learning this too

Wheel Trim | Turbobygarrett

read all they have to read. this was where i got the fundamental understandings from.

Cool thank you!

The garrett link is the best, check it out if you want a good understanding, it has good illustrations too.

Trim is just a ratio on the turbine or compressor(ie each has their own respective trim). The higher the ratios(the higher the number) the more air it will move. Most manufaturers don't give many choices on turbine trim, mostly they alter compressor trim to allow for either a quick spool(lower compressor trim) or top end (higher compressor trim) - assuming turbine trim is held constant. Remember trim is more about compressor, and equally important is the size of the compressor wheel. For example, on a GT4088, the compressor wheel is 88 mm in diameter(exducer, or total diameter). in a GT3572, the compressor is 72mm. The size of the wheel is an equally important factor.

A/R is (Area/Radius) is almost always referring to the trubine, because adjusting compresssor a/r has little overall effect. Smaller turbine A/R will give you quick spool but poor upper end performance. As far as the GT35r (a great choice for an rx-7 on pump fuel) and the RX-7 is concerned, you want to stick between a .82 a/r and a 1.06 a/r . If you have a bridgeported engine, go with the 1.06 a/r, if it is stock or a mild street port, you may want to consider going with the .82 a/r for quicker spool.

Since A/R is mostly for turbine, and trim and (compressor) wheel size is obviously for compressor, this is where you choose the relationship between your turbine and compressor. Everything is a compromise. Low a/r and a really small compressor wheel would be really quick spool and fun for everyday driving, but would be terrible over 5500 rpm.

The GTX35 is a great turbo and the ball bearings are so good lag is not that much of an issue anyway, So don't be afraid to go with a big A/R, but if you post(or pm) what kinda ports and IM(intake manifolds) you plan to use as well as were you want your power I can recomend a turbo thats suitable.

-Kevin

^ great explanation.

Thanks!:icon_tup:

great link thanks