Twins or large single your thoughts
- Thread starter TURBOZ
- Start date
- Joined
- May 27, 2001
If you are going racing it is much easier to find a class to run in with a single than twins. 53s will make about 610hp each for a total of 1220hp. The 88 is rated at 1150hp, but has seen close to 1300hp already. You can step up to a 91.5mm, 100mm, 106mm or even a 108mm. The last of these is not legal for any class that I know off. People are getting 1800hp plus from the 91.5mm and up to 2200 on the 100 and 106 units. Duttweiler just made over 2600hp with twin 100mm on a big block. We may never know how high the dnyo numbers were really!!!
On a 800 hp supra dyno chart comparison, the twins made the power alittle earlier, yet the single made the power band bigger towards the high end. The conscensus was that the single was a better strip turbo and the twin was a better street set up on close to the same cfm. The charts were pretty similar though as is probably the rpm limit of the supra and your chevy. Supra was at 7900 rpm.
SBC, vs a 6 and turbo strategies are two different items.
Reading thru Supercharging and Tubocharging by John Humphries will explain things. Especially the part about Pulse Turbos.
While turbine inertia is of some concern, there are other design elements that can be capitialized on.
Reading thru Supercharging and Tubocharging by John Humphries will explain things. Especially the part about Pulse Turbos.
While turbine inertia is of some concern, there are other design elements that can be capitialized on.
IMO the major differences on a V motor (V-6 or V8) have to do with headers and downpipes. Twins allow short headers and no long crossover, and two separate downpipes, so they tend to spool better for the same rough CFM range. Heat lost through piping is spool energy lost, and turbine backpressure is a limiter with a single 3" downpipe and the bigger single turbos. A couple of guys with the big PTE-88 turbos (Fiscus and Harmon) picked up considerably when they went from a 3" downpipe to a 4" or 5".
I see you've got a 94 Camaro; things may be tight to fit in there with accessories. If you can't fit twins and good sized downpipes for them, a big single and one big (4" or 5") downpipe might be a better alternative.
I see you've got a 94 Camaro; things may be tight to fit in there with accessories. If you can't fit twins and good sized downpipes for them, a big single and one big (4" or 5") downpipe might be a better alternative.
- Joined
- May 27, 2001
If this car is a true street racing purpose built car, you
may want the power to come in a little later.
Most street races are lost at the line with traction problems.
We have a local T Type running a PT-88 that also has
been know to run on the street with out problem.
He is knocking on the high 8s at over 3500 lbs!
He is running the atr headers that are far than less from
perfect . I will probably build a custom foward facing
set of single headers for my car. I have not decided on
putting the turbo in the center of the motor (stock intercooler location) or a more stock type like on Alan Witter's car.
He ran a 90mm + and also an 88mm. I would be interested in
Bill Anderson's input regarding the street car he built.
If you think that you are going to have a problem with getting
the car on boost you can raise the compression to help in spooling. PTE did this on Tweaked 7.75 @ 178 and Alan Witter
8.4 @ 168. My good friend Chris Chow just put a TT SBC in his
car and he basically can not race anywhere and compete unless
he goes to a full tube chassis. BTW twin 76s are not that easy to
spool with an automatic even on a Duttweiler SBC.
may want the power to come in a little later.
Most street races are lost at the line with traction problems.
We have a local T Type running a PT-88 that also has
been know to run on the street with out problem.
He is knocking on the high 8s at over 3500 lbs!
He is running the atr headers that are far than less from
perfect . I will probably build a custom foward facing
set of single headers for my car. I have not decided on
putting the turbo in the center of the motor (stock intercooler location) or a more stock type like on Alan Witter's car.
He ran a 90mm + and also an 88mm. I would be interested in
Bill Anderson's input regarding the street car he built.
If you think that you are going to have a problem with getting
the car on boost you can raise the compression to help in spooling. PTE did this on Tweaked 7.75 @ 178 and Alan Witter
8.4 @ 168. My good friend Chris Chow just put a TT SBC in his
car and he basically can not race anywhere and compete unless
he goes to a full tube chassis. BTW twin 76s are not that easy to
spool with an automatic even on a Duttweiler SBC.
Since the car is currently a six speed I was thinking the big single would be better because it would not come on so fast, maybe not till the top of second gear, then hit hard in 3rd. This would hopfully keep the tires on the car. Where twins would come on right away and blow the tires off the car.
I would like to make 700-800rwhp on 10psi pump gas, which should not be a problem with a big single, but how big 91mm or 100mm? I will never use the max potenial of the turbo being that I still have the stock LT1 block. My short block is good to around 1100hp, the most I have seen is 1200hp(flwhp) on an LT1. Im sure a smaller T88 might make the power of my block but I would like to make more power on pump gas(lower boost levels), and it would be nice to know I will never use the potential of the turbo.
As for room I plan on cutting the radiator support and moving it down and closer to my front mount. Then put a manual rack in to eliminate the A/C and P/S. This will clear up enough room for 2 T76 turbos or one large frame turbo. I already have one T76 on the car I could just add another to the other side
I would like to make 700-800rwhp on 10psi pump gas, which should not be a problem with a big single, but how big 91mm or 100mm? I will never use the max potenial of the turbo being that I still have the stock LT1 block. My short block is good to around 1100hp, the most I have seen is 1200hp(flwhp) on an LT1. Im sure a smaller T88 might make the power of my block but I would like to make more power on pump gas(lower boost levels), and it would be nice to know I will never use the potential of the turbo.
As for room I plan on cutting the radiator support and moving it down and closer to my front mount. Then put a manual rack in to eliminate the A/C and P/S. This will clear up enough room for 2 T76 turbos or one large frame turbo. I already have one T76 on the car I could just add another to the other side
- Joined
- May 27, 2001
Turboz,
If you are going to street drive this you do not want more than the 88. It can make 1200 plus HP in 4 bolt configuration. How is your tranny and clutch holding up to the 76? I would think you would run into problems with the 88. Harry @ PTE states that the 88 is worth 200 Rear Wheel HP over a 76. I am not sure about your 800hp on pump gas. I would reccomend calling PTE and asking for Harry.
If you are going to street drive this you do not want more than the 88. It can make 1200 plus HP in 4 bolt configuration. How is your tranny and clutch holding up to the 76? I would think you would run into problems with the 88. Harry @ PTE states that the 88 is worth 200 Rear Wheel HP over a 76. I am not sure about your 800hp on pump gas. I would reccomend calling PTE and asking for Harry.
It sounds like you don't have to meet any race class restrictions and this is just going to be a fast street car.
If you are on a budget why not run 2 used GN turbos? They can support approx 400hp each? They sell for under $200 here on the forum all day long in good working order. 800hp will push the car into the 9's. If you need to go faster then upgrade once you have the bugs worked out to TE-44's or the 50 series turbos and you will meet your goal of of 800rwhp on 100 octane (pump gas). Fuel quality dictates what timing and boost you can run.... don't cheap out on the fuel or you will pay for it in the long run.
Or you can run 91/92 octane and use alcohol injection..... which is just like running 100 octane all the time.
Here is a link to nice kit that has evolved over the years into a killer fault free system that many on this forum use: http://www.geocities.com/rad87gn/tech/SteveCkit.html
To run any turbo at low boost (10psi) is really not using it to its full potential. 20-25psi is where the peak efficiency is in most turbos except the tiny factory ones found on 4cyl turbo cars. I assume you are running between 8:1 and 9:1 compression? If not you can stack headgaskets to lower compression to where you need it.
Save your money for clutches as high hp forced induction cars eat them up like candy. I'd consider a TH400 instead and save yourself major headaches in the long run. The T56 is limited to about mid 10's before it pukes its guts out after every few runs.
Here is a killer website on a fast local LT1 Camaro and the history of his car buildup and what is needed to get into the 9's:
http://para.noid.org/~lj/
Good luck with your project. Can you elaborate on what internals are in your shortblock? I'm heading down that path in the near future with a TTLT1 powered sub 3000lb widebody RX-7.
GNX7
If you are on a budget why not run 2 used GN turbos? They can support approx 400hp each? They sell for under $200 here on the forum all day long in good working order. 800hp will push the car into the 9's. If you need to go faster then upgrade once you have the bugs worked out to TE-44's or the 50 series turbos and you will meet your goal of of 800rwhp on 100 octane (pump gas). Fuel quality dictates what timing and boost you can run.... don't cheap out on the fuel or you will pay for it in the long run.
Or you can run 91/92 octane and use alcohol injection
..... which is just like running 100 octane all the time. Here is a link to nice kit that has evolved over the years into a killer fault free system that many on this forum use: http://www.geocities.com/rad87gn/tech/SteveCkit.html
To run any turbo at low boost (10psi) is really not using it to its full potential. 20-25psi is where the peak efficiency is in most turbos except the tiny factory ones found on 4cyl turbo cars. I assume you are running between 8:1 and 9:1 compression? If not you can stack headgaskets to lower compression to where you need it.
Save your money for clutches as high hp forced induction cars eat them up like candy. I'd consider a TH400 instead and save yourself major headaches in the long run. The T56 is limited to about mid 10's before it pukes its guts out after every few runs.
Here is a killer website on a fast local LT1 Camaro and the history of his car buildup and what is needed to get into the 9's:
http://para.noid.org/~lj/
Good luck with your project. Can you elaborate on what internals are in your shortblock? I'm heading down that path in the near future with a TTLT1 powered sub 3000lb widebody RX-7.
GNX7
OneQuikSix
Member
- Joined
- Jun 7, 2001
Twin Turbo SBC
Not trying to steal anyone's thread here...but just had a few questions.
I am considering swapping a 383 SBC in my 87 and was pondering many of the same questions as TURBOZ.
Does anyone make a set of headers/downpipes (twin or single) that would facilitate such a swap on a regal? I am not all that concerned with A/C since the car is not a daily driver.
Because this car is not going to be entered into any specific class to race, I am not concerned with what rules I might be breaking.
Also, if anyone has any advice on what types of components to choose or steer away from, I would appreciate it greatly.
Feel free to email me directly, as it was not my intention to cause a fork in the thread
Not trying to steal anyone's thread here...but just had a few questions.
I am considering swapping a 383 SBC in my 87 and was pondering many of the same questions as TURBOZ.
Does anyone make a set of headers/downpipes (twin or single) that would facilitate such a swap on a regal? I am not all that concerned with A/C since the car is not a daily driver.
Because this car is not going to be entered into any specific class to race, I am not concerned with what rules I might be breaking.
Also, if anyone has any advice on what types of components to choose or steer away from, I would appreciate it greatly.
Feel free to email me directly, as it was not my intention to cause a fork in the thread
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