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Discussion Starter #1 (Edited)
Hey Guys,

I'm looking to downgrade in sizing from my Greddy T78 to a SP61GT....

My car is on the stock fuel system, and I have decided not to upgrade, as I'm getting married in June and I've got a wedding to pay for...

The T78 is simply too big and laggy for my taste with the stock fuel system..

I'm currently running about 16PSI boost, and the car is making 425rwhp....

I want to find a fun street turbo for cruising around town, a few street races with the locals, etc...

Any opinions?
 
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Well from what I've learned, the SP61GT is going to work a lot better for you as a fun street application turbo. I will be aiming for a similar size turbo when I go single, to use as a daily driver with street performance in mind.

Most everyone will probably tell you that you're not going to be able to enjoy most of the T78's capabilities on stock fuel.
 

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Discussion Starter #3
Since I dont plan on ever taking this car on high speed runs, over 150MPH, should I look into swapping in the auto rear end...?

Is it a 3.73 FGR?
 

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DO NOT SWAP REARS! I have the auto rear end in now and I hate it. The gears are too short and by 105 mph your in fifth gear! It sucks. I had an sp61gt with the auto rear and I must say it was wicked through second and third but it started to die from there. Stay with your rear end and go with something small like a 60-1 (thats what i have and love it to death). If your staying on stock fuel get something small no doubt.

-Mike
 

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IMO, I would keep the car the same. And plan on adding a fuel system next year. Then you can discover the monster lurking underneath your hood. ;)
Tony
 

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hey man...the cheapest way out of this situation is call greddy n order ureself a smaller back housing for that same turbo...i have a t78 w/.84 back housing...not much lag problem!!!
 

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84 housing

How much did that run you? You're the first I've heard of to swap housings on the T78. What's the difference in spool and power?
 

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im also curious to know the spool difference between the diffrent exhaust housing?
 

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Re: 84 housing

Hau said:
How much did that run you? You're the first I've heard of to swap housings on the T78. What's the difference in spool and power?
hey guys.....there are abt 4 ~5 members that i know that have smaller housings in thier t78s. my friend with a auto has a t78 w/.81 a/r...i have a .84 a/r.....well as far the spool up goes...its not laggy at all in a 6spd....but we r yet to install the same kit on my friend's auto..so i will post some results soon.

full boost around 3900 ~4000, n its not like a on n off switch....the power band is more linear....

it didnt cost me anything extra cause i ordered the kit that way...waited abt
12weeks for it!!

hey hua...if u ever come out to the island jus pm me man....if the weather is good i will definetly give u a ride....
 

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lilmatty96 said:
get a 63 and u only need like 13 psi to make 470hp thing spools up so quick its great
Did you read his post before you posted?

"I'm currently running about 16PSI boost, and the car is making 425rwhp...."

So you are suggesting he can go to a smaller turbo, ar and run less boost and gain nearly 50 hp:rolleyes:


Brad
 
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banton said:
So you are suggesting he can go to a smaller turbo, ar and run less boost and gain nearly 50 hp:rolleyes:


Brad
That seems to be exactly what he's saying, and if the 63s efficiency at a lower PSI is significantly greater that's exactly what will happen.
 

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Discussion Starter #13 (Edited)
SP63 - date from www.moreboost.org

488 rwhp by Al S. (RAnGer498) .68 A/R @ 18psi (SP, AEM, 3row, SP fuel)

490 rwhp by Steve J. .68 A/R @ 18.5psi (SP, stock maf, stock fuel, 93 oct)

498 rwhp by Henri F. .68 A/R @ 18.5psi (cast, dual maf, stock ic)

not gonna happen on 13 PSI....but 17 PSI, yes...
 

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dag said:
That seems to be exactly what he's saying, and if the 63s efficiency at a lower PSI is significantly greater that's exactly what will happen.
You obviously need to get your head out of your ass too, newbie:rolleyes:
 

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Sounds like you already know what you want.

Me personally, I could never go down to a turbo that small. After driving a customer's sp57 6speed, I wasn't impressed at all. Super quick spool but ran out steam really quick. Felt like it didn't have much for top end. Just not that impressive =/
 

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Discussion Starter #16 (Edited)
I'm still leaning towards the 61.....from what I hear, the spool characteristics are where it shines...

As I'm on stock fuel, I can't max out the 63 anyways...so, I mise well go with something that will spool down low and have more fun on pump gas..

WHERE ARE ALL THE 61MM TURBO OWNERS...? This is who I want to hear from....
 
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banton said:
You obviously need to get your head out of your ass too, newbie:rolleyes:
Pardon me, but go read up on turbo theory. Don't go insulting me because I disagree with an uninformed post.

*Edited to add* I wasn't agreeing with the fact that the 63 would produce more power at a lower PSI, just that you can't compare turbos at a given psi by looking at the sizes, you've got to look at efficiency.
 

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Riggs said:
I'm still leaning towards the 61.....from what I hear, the spool characteristics are where it shines...

As I'm on stock fuel, I can't max out the 63 anyways...so, I mise well go with something that will spool down low and have more fun on pump gas..

WHERE ARE ALL THE 61MM TURBO OWNERS...? This is who I want to hear from....
61mm here. :D I make 460 RWHP/415 RWTQ at 17.5-18 psi pump gas tuned safely with the VPC/SAFC, and some have made 500+ HP with the AEM and more aggressive tuning. Come to think of it, I have never done a pump gas run after the car cooled or after icing down the pipes, that 460 came after about 20 back to back tuning runs, so it would make more under ideal conditions.

You won't even come close to maxing the 61mm on stock fuel either. I made 532 RWHP at 22.5 psi on stock fuel then did full fuel for 625 RWHP at 28.5-29 psi, again without the AEM. The powerband of the T61 is a thing of beauty! Here is a 25 psi 5th gear dyno I did, that's about 7000 rpm in 5th for 170 mph. I have done this on the road too, man it feels nice!! 25 psi is definitely my favorite street boost. :cool:




To be honest, the newer 63 or maybe a 67 is probably the ultimate street turbo now, the 67mm in particular has come a long way since 5 years ago. But if you are using stock fuel I wouldn't use anything more than a 63, and I would never use anything less than a 61mm on a MKIV, period.
 

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dag said:
Pardon me, but go read up on turbo theory. Don't go insulting me because I disagree with an uninformed post.
Well we aren't talking "theory" here, the thread starter is NOT going to be driving a theoretical car and turbo either.

Second, turbo efficency at low boost levels is all but a non-issue (especially 45 rwhp with 3 less psi) for the turbos he is evaluating. You can line-up a 61, 63 and 67 and at low boost, the power is going to be very, very similar, but again, real world numbers says 470rwhp at 13psi isn't a realistic expectation on a 63.

But hey, maybe your theory combined with your theoretical supra can pull such numbers:rolleyes: For me, my MKIV w/ 67mm turbo at 13 psi runs a real world 410 rwhp.

Brad
 

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Riggs said:
I'm still leaning towards the 61.....from what I hear, the spool characteristics are where it shines...

As I'm on stock fuel, I can't max out the 63 anyways...so, I mise well go with something that will spool down low and have more fun on pump gas..

WHERE ARE ALL THE 61MM TURBO OWNERS...? This is who I want to hear from....

Riggs, the 61 would probably be a great fit. Based on your set-up, it will spool great and give you nearly the same hp for the boost level you will be running.

Brad
 
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