Talk to me about DRIVE PRESSURE

[MikeThomas]

So im getting close to mounting up my twins. I opted for a Tial 38mm external wastegate b/c it is my understanding the gating will be essential in obtaining optimal drive pressure. I understand in simple terms what drive pressure is and how it relates to manifold pressure, but what happens when they are not 1:1. How else will I obtain 1:1 drive pressure, and where to I put my port for the drive pressure gauge?

Oh yeah, The top is an H1c with the 60mm and 14cm housing, the bottom is a bht3b with the 26cm housing. I have a 12cm available housing for the top as well, and access to a 23 for the bottom.

[MikeThomas]

hmmm, guess this was the wrong site to ask.

[dazedandconfused]

Allot are not on here everyday and takes a while to get responses sometimes

[PToombs]

I'm on everyday, but I don't know diddly about twins.
One of the guys on the TDR added a 38mm BOV on his twins setup. It runs off the drive pressure. From what I read, the drive pressure is plumbed into the top of the BOV, then when you let off, the drop in DP lets the BOV open and dump boost. He had it on the dyno, said it works great. WOOOSHHH!
Oh, he also said he blew out the gasket that came with it, so he cut a groove for an o-ring into the manifold to seal it.

[bgilbert]

On this site, we don't care about no stinking drive pressure!! For the port I think you can tap the exhaust manifold like you would for a pyro. Run copper tubing to the gauge, old big truck 150psi air pressure gauge works good:).

[MikeThomas]

Hehe, just had to instigate a bit. Figure there is a lot of guys with twins on here. Its just my understanding that drive pressure will dictate how efficiently and how well tuned things are. Seems like a lot of people are just bolting twins up without giving thought to tuning....

[KTA]

FWIW my truck makes more power with my manifold charger gated so I run less boost. On my setup i run nearly 1:1 drive pressure versus boost up to about 60psi. Anything above that I start to make more drive pressure than boost. Perhaps that is why I make more power with 70psi than I do with 90. RPM's seem to have the greatest effect on drive pressure the mor RPM's I turn the more unbalanced my pressures become.

[MikeThomas]

Hmm, interesting. Are you refering to the top turbo when you say "manifold charger"?