T76GTS vs GT47

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Mar 26, 2007 | 08:20 PM

koolaid_kid

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From: Indianapolis

T76GTS vs GT47

Where can I find a comparison of these two turbos? They will be going on a street car with a built LT1 383 installed. I checked Garrett's site, but only found info on the GT47.
Thanks.

Mar 26, 2007 | 08:33 PM

engineermike

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That's not even a fair comparison. They are way different sizes and hp potentials. A better comparison would be the 76GTS versus the GT42.

Anyway, the 76GTS will support 1100 or so hp and will usually fit in the engine compartment without major surgery. The GT47 will go up to 1500 hp and is physically way too big to fit in the engine bay without moving around alot of metal.

Mike

Mar 26, 2007 | 08:46 PM

koolaid_kid

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Thanks. Interestingly enough, there is a company offering the 76 as standard, with an available flange for the GT47. But they make no mention that it won't physically fit in the same space. Appreciated.
The car is slated for 700+ hp, so it sounds like the 76 will do nicely. Do you know (roughly) what boost level a 383 would need to obtain this objective? With an intercooler, of course.

Mar 26, 2007 | 08:53 PM

engineermike

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Quote:

Originally Posted by koolaid_kid

Do you know (roughly) what boost level a 383 would need to obtain this objective? With an intercooler, of course.

It depends on the NA hp of the 383. Based on some formulas, if you build a 400 hp 8.5/1 383, then you can expect it to take 11 psi of boost to get there if the system is reasonably efficient.

Interestingly enough, back when I was running 11 psi on my old 383, I estimated the fwhp to be around 680. It made 550 rwhp through an A3/loose converter and pulled about 133 in the quarter. That was with AFR 210 heads, a 224/236 cam, a Vortech water/air aftercooler, with the T76GTS.

Mike

Mar 27, 2007 | 12:43 PM

TURBO383WS6

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go w/ the 76GTS, you'll love it! as far as hp, i have no idea since my car will probably never see a dyno. on 20psi, and a very conservative tune (no more than 19* of timing), i should already be in the mid to low 10 sec 1/4 and have run a 6.94 in the 1/8th w/ plenty of room to spare. gotta line out this suspension.

Mar 27, 2007 | 03:18 PM

MIGHTYMOUSE

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i think the 76 and 383 would be a good match considering a rear mount set up.

Mar 27, 2007 | 03:57 PM

koolaid_kid

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Thanks, MM. Nice dyno run, btw. How about for a front mount (this is for a friend, I am sticking with my rear mount).

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Mar 27, 2007 | 04:38 PM

engineermike

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Quote:

Originally Posted by MIGHTYMOUSE

my gut is that the 76 might be small on the exhaust side for a 383.... i guess it depends on the rpm range of the engine

I've pulled 146 in the quarter at full weight with a T76GTS .96 on 388 cid. The WG is wide open, too, so there's more in it. It will do fine, depending on goals. Rpm will be limited to ~6300 with those cid and that turbo.

Mike

Mar 27, 2007 | 06:10 PM

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MIGHTYMOUSE

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From: Virginia

..like i said

and if your gate is wide open running the turbo hard, imagine the boost stability problems he may run into cutting it down to 700fwhp..maybe even need a second gate

Mar 27, 2007 | 06:40 PM

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engineermike

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Quote:

Originally Posted by MIGHTYMOUSE

and if your gate is wide open running the turbo hard, imagine the boost stability problems he may run into cutting it down to 700fwhp..maybe even need a second gate

Not quite sure what you're saying here. . . but my gate is all the way open, as in the boost is as low as I can get it going 146 in the quarter. I had it set up differently in the past and had no problems running 11 psi and making about 680 fwhp.

Mike

Mar 27, 2007 | 07:10 PM

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THE_SUPRA

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i think the gt47 would be a dog with that power level, go for the 76 fa sho!

Mar 28, 2007 | 07:39 AM

#13

MIGHTYMOUSE

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From: Virginia

obviously the 76 is the better choice of the two given.

Mar 28, 2007 | 11:57 AM

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NA$TY-TA

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Quote:

Originally Posted by THE_SUPRA

i think the gt47 would be a dog with that power level, go for the 76 fa sho!

A Dog????????

I have 13ci less and mine is by no means a dog with my 88mm turbo.....

Mar 28, 2007 | 12:02 PM

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JZ 97 SS 1500

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T6 units FTW

Apr 1, 2007 | 01:50 PM

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eLTwerker

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Quote:

Originally Posted by engineermike

What would be the next step up from a 76? I'm going w/ 400rwhp NA 383 + turbo and would like power to 6500. I'm only looking for max 600-650rwhp.

Apr 1, 2007 | 03:47 PM

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engineermike

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Quote:

Originally Posted by eLTwerker

What would be the next step up from a 76? I'm going w/ 400rwhp NA 383 + turbo and would like power to 6500. I'm only looking for max 600-650rwhp.

Well. . . the next step up would be either the S76 or a PT-88, depending on which direction you want to go. However, the T76GTS will do 650 rwhp easily.

Mike

Apr 1, 2007 | 03:52 PM

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Pro Stock John

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I have a GT47-88 up front:

http://psj.ls1tech.com/gallery/main....d=10&g2_page=5

I'm not a turbo expert, but I'd be considered about how it spooled out back though I don't really know anything about rear mounts.

Apr 1, 2007 | 06:00 PM

#19

ddnspider

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Quote:

Originally Posted by eLTwerker

What would be the next step up from a 76? I'm going w/ 400rwhp NA 383 + turbo and would like power to 6500. I'm only looking for max 600-650rwhp.

since i have a 383 with a T76GTS ill give my experience.im going to redyno in about 2 weeks so will have updated number but on 7 psi with major boost controller issues(ie boost went up then dropped way down the came back up) the car made 530rwhp on a very rich tune for when i fixed the boost controller issue.boost comes in at ~2800rpms.this is a front mount turbo.im expecting 600+rwhp on more boost on pump gas but can keep u posted.