if it has the 74.5 mm front wheel the it has a hp rating of 800hp and more than likely its a GT42R. the GT42RS has a 94 mm front wheel and is rated at 1000 hp. the 102mm outer cover is the exducer and will be on both turbos....... this channels air into the turbo.

Ernie

hang on a sec I think you have some facts mixed up here, sounds like you know whats what but its mixed up. Just to make it clear incase you get angry(me being new and all), the jump in area from a 74.5mm inducer, up to a 94mm inducer that only yields a 200hp gain is wrong, its out of proportion.

In the GT42 family;

68mm inducer 94 mm exducer, that's the 800hp version(garrett)

74.5mm inducer 102mm exducer, that's the 1000hp version(garrett)<<the one I have.

76mm inducer, not sure of exducer that's the 1200hp version(custom)

I am not familiar with the GT45 series, it wasn't around back when I bought this unit.

The plan is to mill the existing dump pipe flange off, 5" is just a little to big to fit, lol.

I agree also, this will work but wont really perform at low rpm or low boost, sweet spot of the map is above what I will be able to run with the stock n/a engine.

Edited February 11, 200818 yr by ltd351t

its rated at 1000hp man

the gt4508r is rated at 1200hp part number 774090-5001

the gt4202r is rated at 1000hp part number 774088-5001

Edited February 11, 200818 yr by etm

Does'nt sound like your um budget ... is going to give a good outcome! :wacko:

Money isn't everything, and spending money on a smaller rear housing isn't something I'm keen on, I'd rather keep the backpressure lower and run a higher stall.

That 600$ is better spent on rods or pistons.

thanks Earn, I think what I was thinking about was more a trans-brake style spool up - if I'm not mistaken as to how this works. I completely understand the concept of efficient boost levels on all turbos, apologies if I missed it, but will this car be a full drag set-up, or still be street driven?

meh, either way its getting this turbo, its a street car, but making boost on the street is something I don't need, if I can drive it normally and make no boost it doesn't bother me.

its rated at 1000hp man

the gt4508r is rated at 1200hp part number 774090-5001

the gt4202r is rated at 1000hp part number 774088-5001

yeah the Gt4202r, that's the one.

Edited February 11, 200818 yr by Dagabond

yeh I would try 3500rpm, with the torque the 4lt makes at 3500, with 5-6psi, should start stretching the stall a bit further, then will make more boost, which will stretch it further again.

if you go bigger then 3500 stall in this weight car, and with the torque it will make, under full boost it will stretch up to about 5200rpm, so any bigger, and you will not have any rpm left to play with.imo

David

the car its going into is lighter than a BA but not a whole lot.

What RPM do these engines like to rev to? I guess that depends on how much boost its running, stock valvesprings no doubt don't take that much.

Dont forget if its hitting full boost, and for these turbos you want to get into its effiency range, which is, as Ern said, 20+odd psi at high 3000s -4000 then your limited in the motors top end. Unless you spend up BIG, your max rmp will be 5800 at best, so your power bands limited.

You can always play with tuning/breathing & boost control to reduce some of the lag.

Should be a big banger to drive though... nothing, nothing, nothing... then woaaaaaaah we have huge boost. Fun times there!

What stops the rpms that early? Is it just valvesprings/cams?

its the design of the engine, its supposed to be a mid-range torque maker. Even if you want the engine to spin to 7000rpm safely it is quite an expensive thing to do, let alone 8 or 9000rpm. I beleive the crank doesn't like going any higher than 6000rpm.

You will definately need better valve springs though, the stock ones are useless.

Oil pump gears fail at high rpm also,

And it is just an old falcon motor with a twin cam head on it... it was never designed to rev like the Jap motors do.

There are plenty of i6 motors that spin up to high rpm, they just need alot of work dont to them.

Your better off, $$ wise, getting the smaller exhaust housing/wheel and working within the motors ability... or re-do your sums and figure out what it will cost to make a high rpm motor

speaking with a few people now, given a flash speed of 3500 and lock up speed of 5000rpm, and allowing 1200rpm of lockup range, that puts me only 400rpm above factory rev limit.