I'm running 13 psi through a T-trim and Aftercooler. I currently have a 52 mm throttle body and was thinking about upgrading to a 58.

A friend tells me that the larger throttle body isn't needed with boost. Since the air is compressed, you don't need as big of an opening.

My argument is "why not use a 10 mm throttle body, then", if the size is so insignificant?

Any opinions or test data?

Thanks,
Mike

 

Here are some good discussions on throtle body size and how they affect the motor. They basically saying that its better that you go too big than anything else. Hope this helps.

http://web.camaross.com/forums/show...&threadid=31034

http://web.camaross.com/forums/show...threadid=130974

 

I think what your friend means is that the change from a 52 to a 58 won't make a differance because the motor is not sucking air it's getting stuffed with it. the motor doesn't have to pull air into itself. this help?
Matt

 

I disagree.. there have been hp gains documented going from a 58mm to a monoblade.. now why wouldn't it gain from 52-58mm with a boosted engine????

Anyways... you will have to work on the Trans tables as your car is an auto. the TB changes a lot these parameters.

 

I couldn't get those links to work.

Highlander, I have a TH350, so I don't think transmission calibration would be an issue in my case.

Thanks for the responses - I'll try to do a pressure drop calculation today to see if the math points one direction or the other.

Mike

 

Try these...they should help.


http://web.camaross.com/forums/showt...threadid=31034

http://web.camaross.com/forums/showt...hreadid=130974

 

A larger TB would be low on my list of mods for a SC motor. It will help, but not a lot on most setups. I was using a stock TB for 4 years and had good results with it. But if you want to do it, it can only help. Definitely wouldn't loose any sleep over it either way. It's much more important to remove restrictions from the intake side of the SC. Efforts there will have a high benefit/cost ratio.

Rich Krause

 

OK, here's the results of pressure drop calc's, assuming 13 psig boost at 150 deg. F. A decent supercharged engine will max out the MAF, so I did the calc's at 500 and 600 gms/sec.

Flow___500 gm/sec____600 gm/sec
52_____1.3 psi________2.0 psi
58_____0.9 psi________1.3 psi

According to this, even a 58 mm TB is a restriction. I apparently stand to gain ~.5 psi boost by going to a 58, but as much as 1.5 psi by going to a single-blade, assuming I'm somewhere between 500 and 600 gm/sec.

Mike

 

If you're saying that a 52mm TB is causing a 2 psi pressure drop, then you need to launch the 52. Corky Bell in "Maximum Boost" says that total pressure drop from turbo to intake should be 2 psi or less, or better yet, less than 10% of boost pressure. I'm sure that would apply to a supercharger as well. Since the tubing alone will cause some drop, 2 psi from just the TB is unacceptable. I would also give some thought as to how much pressure drop happens at the 1100 to 1200 cfm that your blower is probably trying to move at max boost.... Hello monoblade!

 

not a bad idea the monoblade

 

But why take my word for it. . .

http://www.efunda.com/formulae/fluid...meter.cfm#calc

This is pretty handy.

I put in a 3" upstream pipe, 5.2 cm orifice (52 mm throttle body), 1.5 psi delta P, and 0.000071 lb/in^3 density (p=P/RT) and get a flow of .3 kg/sec, or 300 gm/sec through single orifice. Of course, 300 X 2 = 600 gm/sec for a twin blade throttle body.

Changing the orifice to 5.8 cm (58 mm), and putting in a 0.95 psi delta P, you get the same 300 gm/sec.

This agrees fairly well with the calc's from earlier in that I could gain 1/2 psi boost by going to a 58 mm, and even more by going to a monoblade.

Someone care to check my calc's???

Mike

 

Are you planning on switching out to a monoblade? I am assuming you currently have a 52mm TB.

 

I strongly considering it based on the dP calc's. For every 1 psi, my car picked up 15 hp, so a 1.5 psi gain should net me ~22 rwhp.

I'd like to figure out what happens to the IAC passage before I do it, though. Do they still use the factory IAC ports?

Mike

 

nevermind

 

I'd be really curious to see some data. I doubt anywhere near that much gian.

Rich Krause