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Discussion Starter #1
I know plenty of people have made good power with a 90mm but at what hp level is it not optimum?
 

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i have seen over 1700 hp but i would think 2500 would be a good round number...

Well then my 105mm is way over kill. LOL! I'm just looking for 1000hp at the motor, I guess if I ever start looking for more power than that I won't need to upgrade the TB.
 

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I just made 1250 with a stock GT500 TB its a twin 62mm bore, Plenty of tuning left.
 

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We make 2500 hp with our combination and a 90mm TB.

Have you tried a 105mm or larger to see if it gained anything?

I had a pump gas engine that was 445ci with a YSi trim and it made 1030 or so with a 90mm throttle body. We were going to test a larger one to see if would pick up anything, but ran out of time and then never did it. The engine is gone, unfortunately.
 

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Have you tried a 105mm or larger to see if it gained anything?

I had a pump gas engine that was 445ci with a YSi trim and it made 1030 or so with a 90mm throttle body. We were going to test a larger one to see if would pick up anything, but ran out of time and then never did it. The engine is gone, unfortunately.
We haven't Mike, at least not yet. I'm not sure it's going to make any difference. The intercooler tubing on our car going to the TB is 4-inch OD, which is the OD of the 90mm TB. The OD of the 105mm TB is 4 5/8-inch, so we would have to use a 4 1/2-inch to 4-inch reducer to hook it all up. Not a big deal I guess but we just haven't done it yet (although we do manufacture this transisitional tubing). Throttle body size is much more critical when it comes to naturally aspirated or nitrous engines than with forced induction engines. On the other hand, if you have a "draw through" supercharger system, like the Ford GT or the '03-'04 Cobra style, in which the supercharger draws air through the TB instead of blowing through it, the size is very critical and "bigger is always better" is the word.
 

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I bought the throttle body off of Brian Browns car after they wrecked it. They had just switched it for a 105 and couldn't tell the difference. That's a 632 with twin 88's.
 

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I wish I would have asked this question before I got that 105mm, I would have done a 90mm and been done with it.

Thank you guys for the info!
 

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And I was just about to buy a 105mm TB...
 

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Discussion Starter #13
Thanks for the good info guys.

I have both a 90mm and 95mm sitting here and I was trying to decide which to use with my 1100hp+ blower combo.

The 90mm will be easier to make work with my intake set-up. I could make the 95mm work but it would be a pain vs the 90.
 

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we use a 90mm. but we have only be 176.7 in the 1/8th ;) at 3050 lbs. on 10.5W. buy you know some say that dont count. lol
 

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Well then my 105mm is way over kill. LOL! I'm just looking for 1000hp at the motor, I guess if I ever start looking for more power than that I won't need to upgrade the TB.
I make 900hp+ at the motor with a 75mm TB and 2 1/2" cold piping at 16 psi. My friend with the same setup 75TB and 2 1/2 cold side made over 1000HP. I think he was around 1100hp and that was because the turbo was maxed out.
 

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Times in sig were with a 70mm @ 3440#'s
 

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I think on a boosted car it depends entirely on what is before the T/B if you have a 80 mm pipe feeding a 90 mm throttle body you probably would not see any improvement with a 105mm , conversely if you had a 110 mm pipe feeding the 90mm throttle body you would probably see an increase by changing to a 105.
 

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I think on a boosted car it depends entirely on what is before the T/B if you have a 80 mm pipe feeding a 90 mm throttle body you probably would not see any improvement with a 105mm , conversely if you had a 110 mm pipe feeding the 90mm throttle body you would probably see an increase by changing to a 105.
I agree but I would go further back than the pipe to the turbo outlet size.
 

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is their an advantage with smaller 4 in. pipe on spool? could a larger tb and pipe cause a slower spool based on air speed into the motor? maybe -maybe not.
 
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