hooked up an old oil pressure gauge to the manifold last night. it was kind of hard to read cuz it was bouncing all over the place under load. at wot, seeing about 33-34psi boost, i was seeing 75 psi on the other gauge. and my exhaust housing is very heavily ported.

i'm not sure what to think.

 

I have become a big believer in backpressure robbing power from our motors. Not only does it rob HP it also is hard on all the internal parts, headgaskets, turbos, etc. If you install a larger exhaust housing and wastegate it around 30 psi you should see a performance gain plus egt reduction.

Doug

 

man that is a lot of drive pressure, even suprised me.

 

Yikes! Mine's probably up there, too. Maybe not quite so bad since I don't have the 3,200 RPM spring. I wish the 14 cm wastegated housings weren't so dang pricey.

 

what would the drive pressures be with twins?

 

I see about 1:1 with the current twin setup at WOT. The needle bounces hard, but it does seem to be around 65psi back pressure to ~65psi post-CAC.

brandon.

 

I have no greater than 1:1 up to 45 psi boost with my HTB2.

Your pressure guage needs to be snubbed.

 

you say the needle bounces hard, how much fluctuation? i was seeing prolly about 30psi of bounce. just curious.

dave

 

Your pressure guage needs to be snubbed.


what do you mean by that?

 

What do you get above 45 psi boost. I'm interested in the comparisons between B-1's and the HTB2.
I also get 1:1 TIP (drive pressure) at 45 psi. At 51 psi boost (my max boost) I jump to 65 psi TIP.
What other bombs??

RJ

 

You need either a gauge snubber or a valve almost closed ahead of the gauge to restrict the flow. When the gauge is bouncing all around the readings are worthless.
If you are exceeding the rating of your valve springs, usually 60 lbs, back pressure any higher will cause damage. Highest back pressures I've seen are on stock trucks with an exhaust brake on with zero boost, about 45 psi. All the modified ones I've checked are lower due to no or free flowing mufflers and larger exhaust pipes.