obZidian

iTrader: (2)

As we all know, matching a turbo to your application is by far on of the most important, if not, the most important factors in a turbo setup. I have been jousting around the idea or dream, of a FI powered ls1 camaro and maybe i might finally get her done.

Im not new to anything FI I have owned a few turbo powered dsm's but back then, it was basically pick a 16g killa and call it a day. I did get to as a 20g on my 92 eclipse but i didn't really know much about the workings of a turbocharger.

So here i am, trying to match the hairdryers for my 408ci and i have a few questions. For starts, i want to know more about the differences in turbine wheel styles. I believe that they have individual power making characteristics and would like to know more. Right now, all i see is P-Trim or GTS. I could just pick the coolest sounding one and be done with it!!! But that is not gonna cut it...

Secondly, the affects of compressor trim versus turbine trim. So, for example, here are two turbos from precision:

800 PT-68 68mm 2.680" 3.580" 76 4"/3" 360 Race Tan .68 .81 or .96 GTQ 3.110" 2.675" 70
850 PT-70 70mm 2.756" 3.502" 62 4"/3" 360 Race On Center .69 or .85 GT-Q 3.110" 2.675" 70

They both have identical or similar turbine trims but there compressor trims are different. Basically, i would like to know the theory that would help me look at these specs and say "Well, this turbo will be more responsive while this one will lag a bit more but deliever more overall peak power.

Another thing is the turbine a/r setup. I read things like tan or on center, I understand the a/r completely, but not the style or a/r relationship or whatever you may call that.

And finally, let say i wanted to choose a set of twins for my 408ci and i see this:

780 PT-67 67mm 2.620" 3.310" 63 3"/2" 360 Race Tan .68 .81 or .96 P-trim 2.920" 2.542" 76
780 PT-67 67mm 2.620" 3.310" 63 4"/2.5" 360 Race On Center .69 or .85 P-trim 3.110" 2.695" 70
780 PT-67 67mm 2.620" 3.310" 63 4"/2.5" 360 Race On Center .69 or .85 GTQ 3.110" 2.675" 70
780 PT-67 67mm 2.620" 3.310" 63 4"/2.5" 360 Race On Center .69 or .85 GTS 3.200" 2.960" 85

If i wanted a combo that yeilded a hp goal of 1000rwhp, 6800max revs @ anywhere from 15psi-20psi for a street/strip, full weight race car with a 4l80e, what are the considerations i should, uh, consider , in picking the right turbo for my app.

Im not asking "please pick the right turbo for me", this isn't one of those threads, But how may i look at this particular table and narrow down to maybe two turbos and go from there.

thanks, i would like to generate a nice thread with this kind of info so it can rely as a reference point for those with the "which turbo for my application" threads.

Im gonna continue reading and finding as much as i can, however, since there is so much collective info here on this board, maybe we can put all of our brains together and produce a nice informative thread...

thanks

obZidian

iTrader: (2)

WEll, got a bit of info here, its not muchd really but a good start:

nitrorocket:
"On center is a housing where the exhaust inlet is centered wit the centerline og the turbo shaft. Tangenial is offset and give the exhaust a straight shot directly to the turbine. A Tang housing is supposed to be good for 5-10% more power. The downside is that you cannot mount the turbos with a symetrical look. One turbo will sit way up and one way down, unless the headers are built to accomodate. But then you still don't have a symitrical look if thats what you want."

Interesting, but my question is, When would you want to run a tangenial turbine housing as opposed to a on center design and vice versa?

Boostaholic

iTrader: (4)

Maximum Boost by corkey bell is a good book for this kind of stuff if your into books

engineermike

Tangential is generally accepted as being better. Some people use on-center due to installation or spacing constraints. On-center is when the turbine inlet flange points directly at the shaft centerline.

Some general guidelines . . .

For 1000 rwhp, you'll need about 1150 fwhp. That's 675 hp per turbo. So, you could get by with a couple of T63E'sl, rated at 690 hp each. However, that would put them close to their limit where they start losing efficiency. Most turbo's reach peak efficiency at around 50% of max flow at 15 psi boost. So, for max efficiency, you would choose 2 turbo's capable of 1150 fwhp EACH. That would mean you would need 2 T-76's for peak performance. My bet is that the combo would be a bit laggy with twins that big. So, you basically have to pick something in the middle that won't be so laggy, but still have respectable efficiency. The PT-67's are probably not a bad choice.

The more complicated side is the turbine. I don't have enough experience to be considered an expert in that area. I do know that every turbine/compressor combination has an optimum engine cubic inch range that will obtain a 1:1 boost/backpressure ratio. On a T-76GTS, that optimum is somewhere in the 325 cid area. The later the trim letter is in the alphabet, the bigger the turbine wheel and the more it will flow. For instance, the S is a large T4 wheel, while the P and R are smaller. Also, a larger A/R will lower backpressure and band-aid too small of a turbine trim, make it more laggy, etc.

Here's a good website:

http://www.forcedinductions.com/help.htm