Camaro Chris

iTrader: (1)

Well with a sts kit you will never get the right turbo, DO to the inefficiency of the RM design. you need a smaller A/R because you lose heat and pressure the further away from the source. you will either run out of hp and power band at 4500 because your A/r is to small or not get boost Intel 4000rpm because the A/R is too big. what do you want track/canyon car or drag car?

Karpellarpy

iTrader: (3)

I'm not mad, and I'm trying to listen. I've already stated what I'm after, a fast spooling street car, not a laggy drag car. I liked the way my previous gt67 spooled, and was pretty satisfied with the power. However, I was maxing it out and overspinning the turbo (and I could send it into surge if I stomped on it sub 3k rpm in a high gear). This caused damage to the turbo eventually. So now I'm looking to size the turbo better to avoid damaging it. "Not great top end" with a turbo'd 402 to me is around the 700rwhp mark. Plenty of big cube D1SC users making 750+. Anyway, I've gotten both positive and negative recommendations for the popular tc78. I've gotten reports from rear mount tc78 guys that they are seeing power fall off ~250hp from 5k to 6.5k rpm ... while my tiny gt67 fell off only 40 hp or so. Something may be wrong with their setup, I don't know, but a turbo is too expensive to purchase just because of a blanket "tc78 will work" statement. So again, I'm not mad and I appologize if I came across that way, I'm just looking for the reasoning or math behind a suggested turbo size. So Camaro_Chris, do you think you can run a bigger turbine to make up for the flow loss from a smaller a/r? I would guess that the flow of a .81 s-trim turbine housing would be comparable to a .96 p-trim turbine housing.

sujomatt

iTrader: (7)

How was it not proven btw.. dude runs low 10's lol

Zombie

iTrader: (2)

For a 6 speed rear mount you are in a motor size range where it's tough to match the turbo to. Unless you go to the same physical sized turbo you will have to have things fabbed to fit the new turbo. Just part of the game.

I suggest doing everything you can to keep all the heat in the exhaust and going with an 80-88mm turbo with a small turbine housing, or go auto and not have to worry as much about spool times.

hawk584

iTrader: (1)

on 100oct.fuel, a buddy of mine's 6speed '02/SS camaro is making just over 630 rear wheel with an intercooled t67 / .81a/r, forged ls1 w/custom turbo cam, fuel system upgrade, stock exhaust manifolds a dyno tune and a few other small things... last i heard before he bought a z06 was i think he was looking at getting a meth kit.

https://ls1tech.com/forums/forced-in...ear-mount.html

Karpellarpy

iTrader: (3)

sujomatt, I was in no way saying that Zombie's combination was unproven. It is obviously quite the opposite, and he has been a great resourse to this site (especially for rear mounts). But as he has stated, a stalled auto vs. an M6 is a huge difference and has to be factored into a turbo choice. I was just trying to say that since your combination isn't running yet, we can't know how well it is working and thus how good your turbo choice was. And I hope that it is a good decision, and that you will have great success with your combination.
Zombie, you're right, fabbing stuff is a part of the game so I can be flexible there. I'm not at a point that I can switch to an auto right now, so I need to size the turbo for the setup as-is (even though my combination is a bit mismatched and thus hard to size for). For me and sujomatt's benefit, do you have an opinion on how your SX80 would spool on an M6? And I haven't had a chance to look, what's the difference between the SX80 and the ST80? Thanks

Zombie

iTrader: (2)

Dunno, here is a video of it before the quick spool valve on 91 oct.

1.25 a/r, 87mm turbine.

http://videos.streetfire.net/video/B...-up_637926.htm

Camaro Chris

iTrader: (1)

First check out Turbo FAQ click TURBO HOW TO and read down the page a little They show how to do the equation for determining Turbo size, injectors ect. If you go bigger you might need more fuel. Second RMs weakness is that you need a smaller a/r. that kills top end, but sence your not looking for a nasty top end try jumping the a/r up a bit. Say your at .62 A/r go to a .7x a/r <(example) if your only dropping 40hp off the top your close to what you want. A .96 A/R is too big, that's front mount size you will have tons of lag on a RM

Camaro Chris

iTrader: (1)

Yeah but look how long it takes to spool that thing. 1st gear at 5000 rpms before he even gets to 10lbs. Not a wise set up for a rear mount. That same turbo on a FM I'll be done with the 1320 before he gets out of second gear. I'm not bashing your car Zombie I think its bad ***. But why such a huge turbo when its not needed to get you to 10's. I think the fact that your turbo is so big its acutely slowing you down over a smaller turbo.

Zombie

iTrader: (2)

1. i've heard guys complain they can't get full boost in first (even front mount guys).

2. this was just testing without the quick spool valve.

3. did you see that built boost decently on the foot brake?

4. When I played with the turbo in neutral I was making 4-5psi at 3000 rpms backfiring like crazy with retarded timing and on the 2 step (just collecting some data for 6spd guys).

5. It spools a lot faster than this old vid now

6. I like to experiment and post the results. It's fun and helps others. Stay tuned for The Zombie rear mount turbo saga Part II