Boost vs backpressure

Bponci

Bponci

rookie
Joined
Sep 15, 2006
Messages
2,160
What's the best boost to backpressure reading people have seen or had? We just made a few test hits this last weekend and I very surprised of what my results were on the data logger. Just looking for some people with results. Thanks.
 
I'm curious about this also.

I used to see 90psi of boost and 75-80 psi of drive pressure in a loose twin set, is lower than 1:1 really ideal? Or does it mean that you should push the setup harder and or run tighter exhaust housings?
 
If I remember right we seen ~60 or so drive vs ~80 boost out of that promod. My triples are a little better than 1:1 at max power, drive does just barley cross over towards max rpm.
 
We played with the gate setting and got a little aggressive on one run. Boost 135psi+ drive 88.8 psi. So far my theory is working out! Only time will tell.
 
Are you talking about the supercharger/turbo combo or is this a massive set of compounds?
 
Joesixpack said:
Well then. That's just cheating! LOL
Click to expand...

For real! two stages of compression and only one turbine to fight! It will be interesting to see if the awesome response and insane boost/drive ratio's will make up for the crank loss of turning the supercharger. very excited to see future results of this build!
 
Todd W said:
For real! two stages of compression and only one turbine to fight! It will be interesting to see if the awesome response and insane boost/drive ratio's will make up for the crank loss of turning the supercharger. very excited to see future results of this build!
Click to expand...
I bet it will pay off at the tree.
 
I don't ever see a SC/turbo out powering just turbo compounds but off the hit should be phenomenal.
 
We will see. Dont see anybody else going outside of the box and trying it. I know theres some loss but gains in other areas.
 
Seems that the ones that can make it to the second round or able to go rounds are the ones that can do good. Not always about the fastest one out there.
 
Bponci said:
We will see. Dont see anybody else going outside of the box and trying it. I know theres some loss but gains in other areas.
Click to expand...

This is exactly what makes this build so interesting to me. there are always compromises in all builds. always have to give up something to get something, if you want a huge power compound turbo set you compromise spooling and if you have to pedal it your re-spool time could cost the race. on this tuck will the loss in overall power be more than offset by how it acts? I don't know but that is the point of it all, figuring out the best combo and trying new stuff.
 
Believe it or not I've had the best luck with a standard s475. 96/88 t6 1.32, drive at 30-40 was half of boost 70-80 across the board. Never staged and launched at the track but it was a rocket ship out of the hole leaving at 25lbs.

With the s588 boost is at 80 lbs peak with drive around 60-80 , still tuning and trying different things but its an animal. I believe due to the difference of a .85 a/r on the s5 compared to the 1.32 s4 is why drive rises faster and ends up higher, so far egts are in check with this s500.
 
DieselheaD said:
Believe it or not I've had the best luck with a standard s475. 96/88 t6 1.32, drive at 30-40 was half of boost 70-80 across the board. Never staged and launched at the track but it was a rocket ship out of the hole leaving at 25lbs.

With the s588 boost is at 80 lbs peak with drive around 60-80 , still tuning and trying different things but its an animal. I believe due to the difference of a .85 a/r on the s5 compared to the 1.32 s4 is why drive rises faster and ends up higher, so far egts are in check with this s500.
Click to expand...

Ok, I'm confused...
You were able to get 80psi out of a 75mm compressor, with 30-40psi drive pressure on a 88mm turbine....as a single?

How is it that I can throw 50psi drive to a 80-84mm compressor, with the same turbine wheel and housing as you, and only get 30-35psi boost out of it in a compound setup?

Wouldn't/shouldn't the pressure out of the primary be higher than 30-35psi?
Doesn't the secondary act as a restriction in the airflow, which would cause the pressure to rise? (Boost pressure is restriction pressure, right?)
 
Extended Power said:
Ok, I'm confused...
You were able to get 80psi out of a 75mm compressor, with 30-40psi drive pressure on a 88mm turbine....as a single?

How is it that I can throw 50psi drive to a 80-84mm compressor, with the same turbine wheel and housing as you, and only get 30-35psi boost out of it in a compound setup?

Wouldn't/shouldn't the pressure out of the primary be higher than 30-35psi?
Doesn't the secondary act as a restriction in the airflow, which would cause the pressure to rise? (Boost pressure is restriction pressure, right?)
Click to expand...


The funny part is most think that's the case but it's not.
Think of it this way, what would you expect the boost to be for the same mass flow on a 5.9L engine vs a 12L.
 
DieselheaD said:
Believe it or not I've had the best luck with a standard s475. 96/88 t6 1.32, drive at 30-40 was half of boost 70-80 across the board. Never staged and launched at the track but it was a rocket ship out of the hole leaving at 25lbs.

With the s588 boost is at 80 lbs peak with drive around 60-80 , still tuning and trying different things but its an animal. I believe due to the difference of a .85 a/r on the s5 compared to the 1.32 s4 is why drive rises faster and ends up higher, so far egts are in check with this s500.
Click to expand...

What kind of changes were made to the engine ? If rpm is the same then 475 should make more power.
 
You must log in or register to reply here.
Back
Top