what kind of gains can i expect from a 62mm throttle body

[blk92z34getrag]

I think a bigger TB would help the 3.1 because it has a lot more low-end torque than the DOHC's. If you've taken any advanced high school auto class you learn about venturi's and such, air moves faster through smaller openings than larger ones. It's really a trade off, with a smaller TB you won't be able to flow as much air at high RPM, but with a larger one you won't be able to flow air as fast at low RPM. If you did a ram-type intake then you would really benifit from a larger TB.

[XLR8ING]

No offence BetterThanYou, but who's said they've lost HP with a 62mm TB on a naturally aspirated platform?
I've been selling them for 3 years now, and nobody has ever told me they didn't like the increase, as well as every track time I've heard from a customer has been better. I wish I had dyno sheets for the TBs, but there's none near me unfortunately.

Now with a turbo set up, I've heard that going bigger is better, but you can go too big as well, such as in Raven's case. On the other side of that, I just sold a 62mm to a customer with a supercharged 2.4L, and he's very happy with the gains across the board, from what he tells me.

And just as a thought, with a TB being 52mm or 56mm, and the plenum being bigger than the opening of the TB, and then the air having to turn into the runners, and at no point in the intake manifold is air being mixed with fuel, does the velocity difference between a 52mm or 62mm TB really matter?
Obviously velocity always plays a role in engine's performance, and if anyone wants to offer their thoughts on the subject, I'd love to hear them.

[Cliff8928]

just curious on the 2.4 supercharged, was the throttlebody attached BEFORE the supercharger? or was it in the normal factory location?

Cliff Scott
89 BerettaGT
89 Volvo740

[m6amba]

ok so i have a TGP with a high lift cam and a t 28(more air) also i have a FRESH performance engine rebuild..as in under 1000 miles.........i want to upgrade to the 62mm unit im running 12 lbs of boost will it help me and if so how much?....i can only see that it would help by opening it up and allowing more air to go in even if it means a slightly lower velocity it is the same principle of exhaust back pressure right? no back pressure means lots of high end but not as much low end...more back pressure means more low end but less high end and when yer racin how long do you actually spend in the low end of your rpm range? hell i hit fuel cut at 5500 and when im racin my car never gets under 3500......except when i first launch but it gets above that so fast when i brake torque it that it is almost negligible how much time i spend under 3500 so i really dont care about that range for racing....however for pure street use i would want more lowend to smoke the tires more ............







but anyway.......has anybody with a TGP tried one ? or at least a turbo 3.1? to see how much gain ya get when ya introduce boost into the equation..........................

[XLR8ING]

The TB was for used on the supercharger GM sells for the 2.4, which replaces the whole intake manifold and the TB mounts on the inlet side of it.

[2_8_mpfi_chevette]

I thought that the velocity was only a issue with carb setups. The carb wouldent produce a accurat mixture at slower velocitys and the fuel wouldent get/stay atomised. But this shouldent matter with a mpfi setup? the only way the velocity would lower would be by enlarging the runners.? Am i thinking right?

[m6amba]

hey i did some figuring on the desktop dyno...and to go from the 52mmTB to the 62mm TB i theoretically gain over 30 hp with 12 lbs of boost but in order to get a TB to match the 500 cfm of my turbo i haev to go even bigger than 62mm........any know where i can get a 65mm ?

[Bryan1970]

By putting on a bigger TB you do reduce the velocity at all parts of the RPM range accept for WOT. ANd unless your going to race the car it wouldn't be a good street car. The velocity factor goes for all carbs and TB's. The velocity isn't the reason that the air fuel doesnt stay atomized it is partially because it is a carb and not an injector. Basicly carbs are not as efficient as injectors. Another reason the air fuel doesn't always stay atomized is because it is flowing on and around the throttle plates when not in the idle circut.And it will condece on the throttle plates. But back to the reason for why bigger is not better all the time. On a stock engine it has a good amount of velocity going in the intake and that same velocity acts as almost a form of boost(similsr but definatly not the same) when the intake valve is opening. Most people think that the piston does the whole job of putting the air/fuel mixture into the cylinder. And it does a lot of it but it also uses the velocity of the air going to all the runners to flow into the cylinders. And when less velocity goes into the intake at low and midrangeRPM, HP is also hurt. So the only place that real gains of HP will be at the top end of things.

[Sorin]

By putting on a bigger TB you do reduce the velocity at all parts of the RPM range accept for WOT. ANd unless your going to race the car it wouldn't be a good street car. The velocity factor goes for all carbs and TB's. The velocity isn't the reason that the air fuel doesnt stay atomized it is partially because it is a carb and not an injector. Basicly carbs are not as efficient as injectors. Another reason the air fuel doesn't always stay atomized is because it is flowing on and around the throttle plates when not in the idle circut.And it will condece on the throttle plates. But back to the reason for why bigger is not better all the time. On a stock engine it has a good amount of velocity going in the intake and that same velocity acts as almost a form of boost(similsr but definatly not the same) when the intake valve is opening. Most people think that the piston does the whole job of putting the air/fuel mixture into the cylinder. And it does a lot of it but it also uses the velocity of the air going to all the runners to flow into the cylinders. And when less velocity goes into the intake at low and midrangeRPM, HP is also hurt. So the only place that real gains of HP will be at the top end of things.

Well what if you also put on a larger intake manifold (2000+ 3x00 on a 97 3100), a better air intake, and do some headwork?

[Bryan1970]

Then to take advantage of the bigger runners and intake you would need to get a bigger cam. don't get me wrong porting and bigger manifolds will possibly give you gains across the RPM band but mainly at high RPM. Because with the stock cam and bigger spaces everywhere the low velocity effect will only get worse because the cam is still opening as far and as long as when it left the factory. All though if you want to do some porting and want low end to midrange power don't go straight for the intake runners to make them bigger. Smooth out the intake and exhaust bowls first.(the bowl is the area where the valve goes into the runner right before the opening in the comustion chamber for the valve) And you can also polish the cumbustion chamber. Don't go carzy here too much polishing could cause a loss of compression. Don't polish the intake runner or fuel will stick to the walls and puddle up. However you can polish the exhaust runners.

[RacerX11]

hey i did some figuring on the desktop dyno...and to go from the 52mmTB to the 62mm TB i theoretically gain over 30 hp with 12 lbs of boost but in order to get a TB to match the 500 cfm of my turbo i haev to go even bigger than 62mm........any know where i can get a 65mm ?

This only applies if the TB is upstream of the turbo. If your turbo is blowing through the TB, the stock 52mm will flow WAY more than 500cfm under boost. How are you geting these numbers from Desktop Dyno?

Marty

[m6amba]

what do u mean how am i gettin these numbers?.........i entered my specs and thats hwat it came up with

[RacerX11]

What I mean is, what kind of setup are you simulating, turbo, or NA? Does desktop Dyno take into account the fact that the TB is downstream of the turbo, or not? If the TB is upstream of the turbo, then changng the size will have a dramatic impact on the power output. In the stock location between the turbo and intake, the 52mm TB should be good enough to flow 300+ HP easy. The flow across a given size TB is dependant on how much pressure you have across it. If you run 14 psi past a stock TB, you will get roughly twice as much airflow as with NA. It has been mentioned in other threads that turbo 3.8 Buicks are pushing 550+ HP to the wheels with the stock 58mm TB.

You aren't going to pick up 30HP with just a TB swap.


Marty

[m6amba]

ahhhhhhhh.........got it now ......im runnin turbo setup and that has the TB down strem of the turbo.....so is there a method i can use to figure out cfm at boost?