New dyno numbers, 415 WHP

[SappySE107]

Im so freaking confused. Why are you running a 52mm TB on a 3.4 DOHC? Why would you recommend a 57 ported TB? 64 was stock for the DOHC.

[CNCguy]

An undersize TB can be just as bad on a turbo charged engine. Every bend, transition and change in flow pattern creates restrictions and a pressure drop. Per Maximum Boost by Corky Bell, the recommended maximum pressure drop from turbo to manifold is 10%. The purpose of an intercooler is to reduce the temps created when compressing the air. Lets say that at 15# boost at the manifold there is 20#s coming out of the turbo thus having a 5# or 25% drop in pressure. If there were less restrictions, say 2# instead of 5#, then the turbo could be operated at 17# thereby creating less heat, less detonation and more power.

The only way to measure your actual pressure drop is to use multiple pressure gages at various points along your boost path. Right after the turbo, before the intercooler, after intercooler, before TB, after TB and in the manifold.

Put a bigger tb on it like even a ported darrel morse to 57 mm and I guarantee that you will see a gain in power. SHould be an easy swap as you don't have to change anything.

Yes you are pushing air through a tb with a turbo, but you can push more air through a 57 mm hole then a 52mm hole at the same boost level. What does this mean for you? More air = more power.

Also the larger tb will help with transient response between vacuum and boost as the motor can suck in more air through a 57 mm tb then a 52 mm unit. Which eqautes to quicker spool which means a quicker car and more power.

I spooled faster and made more tq by going from a 52 mm fiero TB to a darrel morse ported 57mm tb on my turbo pushrod setup.

I love how people like to argue that with a boosted application, runner size and or tb size doesn't matter because you have a turbo to push the air. Its totally laughable.

If thats the case then take off the 52mm tb and put on a 30 mm tb from a lawnmower and get back to me on if you make the same power at the same boost level with the same spool.

Come on guys.

[IsaacHayes]

On a turbo you are forcing air in, so a small throttle body isn't much of a restriction since the motor isn't trying to suck in through that small opening. If the TB is smaller than the output/charge pipe of the turbo then I can see it being a restriction but if it's the same size or bigger as the output piping then I don't see it making a difference going bigger.

[SappySE107]

Yep. Hopefully this proves to people that this isn't the restriction on most engines. NA engine "seem" to get a benefit because the same throttle pedal tip in gives you more air. And the sense of more power.

I don't care to argue either but you made this comment, which has nothing to do with your turbo experience.

[timg]

Looks great! The 3071R is a great turbo. I'll bet the spool is almost instantaneous. Have fun with it!

Tim

[Matt Hawkins]

Do you have any dyno data for a stock TB versus bigger for a NA 3.4l DOHC? I am not looking to debate NA performance. I am talking about my turbo experience.

[SappySE107]

Have you tried a larger TB on an NA 3.4 DOHC?

[Matt Hawkins]

Sure there is a flow difference due to the larger diameter versus butterfly cross section. All I am saying is it is a small difference. Rarely worth the cost of the new throttle body. Usually, money is better spent elsewhere.

[SappySE107]

You are boosted, which makes a difference. I am not sure how you conclude that a larger TB doesn't add hp to an NA motor. I have documented the flow difference at the intake valve between throttle bodies, and we also know that with a larger plenum, you can use a smaller throttle body. Powerband is important to tune your TB size/plenum area with though.

Id like to see you run a 3.1 TB on an NA 3.4 DOHC and see what happens. That is what you are doing now with boost.

[Matt Hawkins]

Yep. Hopefully this proves to people that this isn't the restriction on most engines. NA engine "seem" to get a benefit because the same throttle pedal tip in gives you more air. And the sense of more power.

you are running a 52mm tb?

[Matt Hawkins]

I am not sure of the compression ratio. I would guess that I lowered it to around 8.5:1. Not a drastic change over the stock 9.25:1. I did the porting of the combustion chambers more to clean up sharp edges and unshroud the valves.

[HayesPerformance]

What Compression are you roughly running?

[HayesPerformance]

perfect thanks!!!!!!!!