9 Second (STS) REAR mount setup
TECH Regular
Joined: Feb 2003
Posts: 451
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From: Spring Hill, TN
Originally Posted by ddnspider
Sometimes it takes awhile to learn some of this stuff,but youll get there.
Something you said actually made me think of something,in the other thread about rearmounts vs front mounts it was said and pretty much proved that a rearmount is less efficient as getting the air and heat to the turbo correct?If thats true then wouldnt you be able to use a larger motor with a smaller turbo to get in the efficiency range of a front mount setup with a motor suited to the turbo?I dont know if i explained that right or it made sense but it makes sense in my mind.Wouldnt that work?
Something you said actually made me think of something,in the other thread about rearmounts vs front mounts it was said and pretty much proved that a rearmount is less efficient as getting the air and heat to the turbo correct?If thats true then wouldnt you be able to use a larger motor with a smaller turbo to get in the efficiency range of a front mount setup with a motor suited to the turbo?I dont know if i explained that right or it made sense but it makes sense in my mind.Wouldnt that work?
In effect, the turbo sees a smaller motor because the exhaust gas has cooled and shrunk and lost velocity.
From punching some numbers into a weight/hp calculator:
600rwhp and 3000 lbs is a 9.96 @ 136.8
650rwhp and 3200 lbs is a 9.91 @ 137.6
So if you can drop some weight, I think a high 9 is very do-able.
My target is 3200 and 650.
That's with an STS 67, upgraded by Jose to a 70, on a fresh SDPC forged ls1 shortblock. 60 lb injectors, '97 'vette return type stock fuel rail, walbro pump, KB BAP. 4" obx fmic. No meth. Automatic, 3.42 gears, ET streets, skinnies.
60' times will make or break the high 9, especially being so close to the edge.
Just waiting on the engine and turbo to get done, and get here... Plus finishing up the roll bar, various weight reduction, etc.
600rwhp and 3000 lbs is a 9.96 @ 136.8
650rwhp and 3200 lbs is a 9.91 @ 137.6
So if you can drop some weight, I think a high 9 is very do-able.
My target is 3200 and 650.
That's with an STS 67, upgraded by Jose to a 70, on a fresh SDPC forged ls1 shortblock. 60 lb injectors, '97 'vette return type stock fuel rail, walbro pump, KB BAP. 4" obx fmic. No meth. Automatic, 3.42 gears, ET streets, skinnies.
60' times will make or break the high 9, especially being so close to the edge.
Just waiting on the engine and turbo to get done, and get here... Plus finishing up the roll bar, various weight reduction, etc.
Originally Posted by jyeager
I think I know what you mean. Could it be stated this way?: For a given engine, a rear mount turbo should be smaller than you would choose for a front mount.
In effect, the turbo sees a smaller motor because the exhaust gas has cooled and shrunk and lost velocity.
In effect, the turbo sees a smaller motor because the exhaust gas has cooled and shrunk and lost velocity.
Suspended Sponsor
Joined: Oct 2004
Posts: 371
Likes: 0
From: Just outside of Palm Springs Ca.
Originally Posted by Wet 1
Is the criteria a quick spooling street car or a 9 second car? I'm not suggesting you can't have both, but I hear a lot of talk about area under the curve in this thread... last time I checked very few 9 second cars spend little (if any) time under 5000 rpm.
Smaller turbos 'feel' very peppy on the street, but big turbos generally rule the track.
Smaller turbos 'feel' very peppy on the street, but big turbos generally rule the track.
I would have to disagree, unless you are running a BIG stall in an auto, it is area under the curve that makes ANY car fast at the track. I would consider AVERAGE power to be the biggest concern, for a stick car especially, as it will likely leave better without having to "dump it" at 6K!
-Bryan
Originally Posted by Frost
BUT... [complex] reactive-inductive circuits = trig = teh suck = 
That's right; gay turds beotches
blablabla
Originally Posted by Race-Prep
I would have to disagree, unless you are running a BIG stall in an auto, it is area under the curve that makes ANY car fast at the track. I would consider AVERAGE power to be the biggest concern, for a stick car especially, as it will likely leave better without having to "dump it" at 6K!
-Bryan
-Bryan
If we were to talk about street or road racing cars, I certainly agree that power under the curve becomes much more important.
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Having a flat power curve is good for the 1/4 because when you shift you drop down to similarly strong part of your power band. If you make 800rwhp peak, and on shifts you drop 2000 rpms but to spot where you make 750rwhp, you will run better than if you made 600rwhp at that spot... that makes sense right?
I would also say that the car with the flat power curve is not probably going to be the dyno king since the builder probably optimized the package's power curve at the expense of the peak.
When I changed cams I picked up 75rwhp under the curve but only like 20rwhp at the peak.
I would also say that the car with the flat power curve is not probably going to be the dyno king since the builder probably optimized the package's power curve at the expense of the peak.
When I changed cams I picked up 75rwhp under the curve but only like 20rwhp at the peak.
so what do u guys think about that theory i had,it makes sense in my head but who knows.With that logic couldnt he use a 408 with a T76 and it would spool really fast AND be efficient because of the loss of heat and such while traveling back to the turbo so it wouldnt get choked?
Spider.... Check out this thread, we talk about this pretty heavily.
https://ls1tech.com/forums/forced-induction/440034-rear-mount-turbo-smaller-r-question-why-would-hurt-performance-long.html
John.... That is why I think the 370 and GT-42 76 would be ideal. I think it would see a strong HP curve instead of a very peaky one. Like you said.. I would love to have a very flat 700+rwhp rather then a steap peak 800rwhp.
https://ls1tech.com/forums/forced-induction/440034-rear-mount-turbo-smaller-r-question-why-would-hurt-performance-long.html
John.... That is why I think the 370 and GT-42 76 would be ideal. I think it would see a strong HP curve instead of a very peaky one. Like you said.. I would love to have a very flat 700+rwhp rather then a steap peak 800rwhp.
