Hey... I got bored yesterday so I made a webpage that I think is helpful in showing people how to evaluate turbo compressors. It uses a combination of real maps, experimental dyno results, and some rough calculations to explain a little bit about how you pick a compressor.

It's not meant to be 100% accurate.... so nobody needs to get out their slide rule and try to nitpick

http://www.zeroglabs.com/rx7/compressorsizing.htm

Brian

 

Thats some realy good info! Thanks for helping the stupid. (me)

I don't suppose you have a compressor map for a SR stage II, or a holset HX35? CJ

 

Wrong compressor trim wheel for the GT40r. Wrong on ATP's site too. Told them about it over a year ago.

 

thats pretty cool.

 

Hmmm Interesting. When you look on Garrett's site, and click on GT4088R (I assume this is the GT 40R people talk about), you actually get some compressor map labelled "GT2876R"... so go figure.

Just out of curiosity, how do you know the thing I have as "GT40R" is the wrong one?

Thanks,
Brian

 

Brian,

I have the turbo...had the first kit. It had the wrong wheel on it. They are supposed to have the 54trim wheel on it, which I have now. The 56 trim was only on the early prototype units I was told by my master Garrett dealer...who sourced the correct wheel for me.

Tony

 

Asleep,

Ah... So you're saying that the GT40R 56 trim map I have is (or was at one time) a real map, but in reality, a "GT40R" should actually come with the 54 trim wheel. This would be the GT4088 wheel in Garrett-speak, right?

Thanks for helping to clear this up.

 

Yes.

The wheel that is on the GT40R that one could purchase from Garrett, or a dealer, is a 54trim. Big difference in spool up.

I have the map here somewhere...I'll post it when I find it.

The 56trim spooled slow but had a big bang up top.

See video against a 11.79 second Evo here:
http://flathat.woodstream.net/Columb...II_40to130.wmv

Tony

 

Actually, the reduced size image on the web page is the one reading GT2876R. If you click on it, you will get a large image that seems to have only the upper left corner of a map. Download it as an image to your desktop and doble click it to see it in your image viewer. You will now see the "actual" 52 trim wheel's map of the current GT4088R. This must be one of those "ups" the webmaster made, and there are plenty of them on the Garrett website. The 54 trim wheel has, from the begining, been the GT4088 journal turbo's. As a service to you all, here you can find it attached:

 

So it looks like we've got a bunch of GT40 maps...

GT4082 (the smaller one)
GT4088R 52 trim (the ball bearing one)
GT4088 54 trim (the journal bearing one)
GT40R 56 trim (the "mystery" one that Garrett's page doesn't seem to mention... yet there are compressor maps floating around all over th internet)

Right? ugh... it's enough to drive you crazy... why can't they just be clear and complete on their page?

 

OH my goodness... as if that's not confusing enough... I found this picture...



which seems to say it is a GT40 56 Trim if you read the title on the image....

But... that doesn't seem right... looks just like the published map for a GT35R here:



So... what's up with that? AAAAAHHHHHHHH...

 

Its enough to make you wonder if all their compressor maps are really just BS anyway. I've "heard" that they dont publish real compressor maps....never believed that though...but seeing them have the same map for 2 turbos really makes me wonder.

Stephen

 

does anybody know what happens if you hit the surge line on the compressor map?


What does it sound like?

Will it pop the engine?