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Discussion Starter #1
I just installed the Sound Performance SP74 turbo in place of the Turbonetics T-64 on my car. Power-related mods on my car are SP fuel system with 72 pound per hour injectors (750-ish cc), SP Cold Air Intake, GReddy "3-row" FMIC, RPS header, 3" DP, GT Spec cat-back, and HKS 264 cams. The SP74 has a 74-mm compressor wheel (at the inducer) and a .81 exhaust housing with Q-trim wheel.

I only drove the car for a few miles after completing the install last night, but I have to say that the turbo is awesome and spool is incredible for a turbo capable of suporting 825-850 RWHP. To give you an idea of the spool characteristics, I reset the peak hold on the GReddy boost gauge, then did tests in 2nd, 3rd, and 4th gears wherein I would nail the throttle at 3K RPM and then let off the instant the tachometer indicated the target ending RPM. From 3K to 4K RPM in 3rd it made approximately 9 PSI and I could tell that it was JUST beginning to cook. Not too bad for a 74-mm compressor wheel, and considering that the stock twins in sequential will only make 15 PSI under these conditions.

BUT, by 4500 RPM it made 23 PSI! In 4th it made 28.5+ PSI by 4500. I had the EVC EZ set at 2.0 kg/cm2, so I don't know how much more it would have made in 4th at 4500. I tried to test it in 2nd gear, but couldn't get much of a test because it kept blowing the tires away before 4500. It kinda hooked up a little in 2nd once and made about 18 PSI by 4500.

One other thing to keep in mind is that my tachometer indicates about 7150 when it hits the factory 6800 RPM rev limiter. I don't know what the actual RPM is when the tachometer is indicating 4500, but it is probably less than 4500 -- maybe around 4300 or so.

I definitely look forward to playing with it some more. I haven't done any pulls -- just a few short stabs of the throttle through a couple of gears -- but so far I think it's very impressive. I was hoping that it would spool decently early in the RPM range, and it definitely does. Considering the power-making potential of such a huge turbo, I'd say it spools incredibly well. It's pretty nice just going moderately through the gears -- not really nailing it. Where with the T-64 you can be pretty liberal with the throttle and still not have the power come on too explosively, you have to modulate more carefully with the SP74. If you don't, it just gets wild with boost (that's a good thing :) ). As you would expect from a turbo this size, power comes on like a 600 pound boot to the ass! I like it. :)

Steve
 
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Sounds like a nice size turbo with some good spool. I am curious to see how this stacks up against other big singles. Of course it is not as big as the "big thumper". That was the nickname of a 9.5 inch diameter, 5 inch outlet, 48 lb turbo used in a vette I read about. Don't know the flow on it but it was a hefty piece of equipment. It was used on the cover of turbo magazine years ago.
 
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Strap that bitch to a dyno and let see some high hp numbers!:D
I want see how this turbo compares to a T78 power wise.
 

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HpPak said:
Strap that bitch to a dyno and let see some high hp numbers!:D
I want see how this turbo compares to a T78 power wise.
It should be a better comparison to a T88. The SP74's compressor is 7mm's bigger than a T78s. Good luck with the turbo Boost Junkie!

-amir
 

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Congrats Steve! Sounds awesome! Please keep us updated.

Adam
 
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awsome steve,


I'll be making the same switch in a few weeks(Sp63 to SP74). Please expand more on the differances you feel/record. Is it really that much more power than the 660hp you got from your 64. I'm getting excited thinking about it.


later, mike
 
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Mike,

I drove it some more late this afternoon. No more than I've driven it, I'm already used to it, spool wise. Realistically, it is probably about 500 RPM later spooling than the T-64, but just like it probably took you about 10 miles to get used to the SP63 versus the stock twins and never have another thought about the slightly earlier initial onset of boost from the twins, I'm pretty much that way with the 74 already.

It's weird, but it's hard for me to tell by seat-of-the-pants exactly how the power compares. Maybe I'm just trying too hard, or maybe it's because I've just been doing some short pulls through a couple of gears at a time because I've been cautious not to go more than about 2X the local speed limit... And I seem to be unable to remember just exactly how the T-64 felt under full boost. So far on the 74 I've kept the A/F ratio pretty rich -- running at about 10.9-11.2:1 once it comes up on boost and on up into the higher RPM range. At that setting, I THINK it's pulling about as hard at 21 PSI as the T-64 did at 25-26 PSI and with the AFR peaking at 11.8-11.9:1 on the 64 in the higher RPM range. (Man, I don't know how I lived without this built-in wideband for so long. :) ) I think the tendency for wheel spin in 3rd gear is about the same in the above scenarios -- breaks loose sometimes but most of the time it doesn't. IMO, it's a hell of a turbo.

The best way I know to compare to the now-versus-then is to race my friend's ZX-12R (pipes, dynotuned jet kit, and sprockets) again. While I had the T-64 I ran him at about 26 PSI and me with a passenger. He put about 2 lengths on me from 70 to 160ish. We're planning to get together sometime in the next couple weeks or so. I'm probably going to take the same passenger along so it's as near a duplication of the earlier race scenario as possible. (BTW, this 12R walks the local Hayabusas without much problem.)

SP74! -- the best little street turbo on the market. Get14U. ;)



BLK-SP64 said:
awsome steve,


I'll be making the same switch in a few weeks(Sp63 to SP74). Please expand more on the differances you feel/record. Is it really that much more power than the 660hp you got from your 64. I'm getting excited thinking about it.


later, mike
 
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Sp74

Congrats the new turbpo hey i was wondering with such high horse power when you crank the boost to the max do you plan to use 93 pump gas or do you have some race gas ready?
 

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pick me!

Hey steve its me billy from the floridaz32 board. i would love to ride with you when you run Brian. if you want i can bring along the camera so you can see the results for yourself later. anyways drop me an email at [email protected]
 

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Discussion Starter #10
Re: Sp74

I rarely run straight pump gas. I usually run a 50/50 mix of Sunoco GT Plus 104 unleaded and Shell 93. On the T-64 I considered 17 PSI the base boost for 93 octane, and would add about one PSI per octane point, so that would make the above mix good for about 22-23 PSI. If I want to turn it up more, I raise the octane by running a higher percentage of GT Plus. I'm probably wasting money on octane, but I don't put that many miles on my car (so the race gas doesn't cost me all that much per year) and I'd rather be safe than sorry on that front.

Steve

VJRacing said:
Congrats the new turbpo hey i was wondering with such high horse power when you crank the boost to the max do you plan to use 93 pump gas or do you have some race gas ready?
 

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Steve,

Where in Jax do you buy 104 octane? I just started buying, every Saturday, three to six gallons of 116 octane. I actually have to buy it from a very small business who stocks race gas and at $7.50 a gallon the shit gets expensive.
 

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You should be able to buy it 55 gallon drums for a little better price. I run Sunoco 104 unleaded as my daily gas in my lexus, and I buy it by the drum for @$200.

-Ethan
 

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17psi power?

Would be interested in knowing what sorts of power it makes at this level and how quickly it reaches that level - it sounds like it spools pretty darned quickly and hitting "only" 17psi wouldn't be hard. Will yo ube dynotesting it anytime soon?

Congrats - you're making the SP kits sound better and better :) [ignorant question] Was it as easy as popping one turbo off for another? No piping changes or anything? Water cooled centersection?

TIA! Please keep us posted, love hearing about it.
 

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Hows it going Steve? I am glad you lie the SP74, you are making me think of get that opposed to the SP66. I was unaware that you had the RPS manifold. I was under the understanding that you could not get the SP cold air on with the RPS intake. Interesting!! I am going up to O-town in the next couple of weeks to finally get my fuel system and retune it. Maybe we could meet up again and tune them I would love to see the difference between mine and yours as far as spool up.

Peace
Justin
 

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Discussion Starter #17
Re: 17psi power?

VetKilr,
Browning Chassis (765-0507) handles several brands of race fuel including Sunoco. They're out of GT Plus right now.


BLKMGK,

Once it hits about 1.0 kg/cm2, it's almost instant full boost from there. So, it probably won't make 17 PSI much earlier than it made 23.

My T-64 was water cooled, so I removed one -6AN water line completely and connected the two coolant ports on the engine together using the other line. The only differences in fitment were that with the turbos bolted up to the header, the V-band flange on the SP74 turbine housing is positioned about .150" further rearward than the flange on the Turbonetics turbo. This caused the waste gate body to sit .150" away from its flange on the header. Most shops would probably have just tightened the wastegate-to-header-flange bolts down and pulled the WG body up against the flange or just added a 2nd Fire Ring gasket, but I made a stainless steel spacer out of some ~2-mm sheet stock and added another Fire-Ring gasket like the original. The result was gasket, ss spacer, gasket, and a perfect fit. (I just traced the spacer from the original Turbonetics Fire Ring gasket, drilled the bolt holes with a 3/8" bit, drilled a starter hole for the center opening, and cut the entire thing out with a hand-held jig saw. No problem.)

Steve

BLKMGK said:
Would be interested in knowing what sorts of power it makes at this level and how quickly it reaches that level - it sounds like it spools pretty darned quickly and hitting "only" 17psi wouldn't be hard. Will yo ube dynotesting it anytime soon?

Congrats - you're making the SP kits sound better and better :) [ignorant question] Was it as easy as popping one turbo off for another? No piping changes or anything? Water cooled centersection?

TIA! Please keep us posted, love hearing about it.
 

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Discussion Starter #18
Justin,

I think the SP CAI was originally designed for the RPS header. At least the one I have was. Let me know when you're heading to Orlando. Maybe we can do like we did last time, only this time over at Rollo's shop.

Steve

FiZZioN said:
Hows it going Steve? I am glad you lie the SP74, you are making me think of get that opposed to the SP66. I was unaware that you had the RPS manifold. I was under the understanding that you could not get the SP cold air on with the RPS intake. Interesting!! I am going up to O-town in the next couple of weeks to finally get my fuel system and retune it. Maybe we could meet up again and tune them I would love to see the difference between mine and yours as far as spool up.

Peace
Justin
 
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Steve and VetKilr,
Wells Performance on Universaty Bvld in arlington sells Sunoco 104 unleaded $4.50/g ,
leaded gas is 110 $4.25/g, 112 $5.25/g, 118 $7.75/g.
There # is 743-5878.
 

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Boost Junkie said:
Justin,

I think the SP CAI was originally designed for the RPS header. At least the one I have was. Let me know when you're heading to Orlando. Maybe we can do like we did last time, only this time over at Rollo's shop.

Steve

I will send you an email before I head up there. And thanks for the info.

Justin
 
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