boost creep vs turbine housing AR
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Ok I have little bit of a fun argument with a fellow forum member, to whom each has there own perspective yet agree on the basic 101 facts
Question:
If on a turbo system you have boost creep and even with the WG totally removed you still build 4psi......... You could only address this problem by changing the turbine housing AR and nothing else
which will help the problem??
B. Decrease the AR - argument, By decreaseing the AR you have increased the backpressure of the system and in sense made the WG more efficient because the WG will be the path of least resistance because of the bottle neck at the turbine.
A. Increase the AR - argument, By increasing the AR you have lowered the backpressure of the system and made it easier to control the turbine speed (boost). Also increasing the over all flow capacity of the turbine
opinions please.....
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increase in AR.
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Where's the neither option? Both have decreasing benefits in their perspective applications.
Smaller AR creating backpressure it going to kill poweroutput/powerband and lower the effiency, thus creating heat, and large AR is is also going to midrange poweroutput/spool.
I vote C. Make the wastegate work correctly in its current application.
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psi2hi;286299 wrote:
where's the neither option? Both have decreasing benefits in their perspective applications.Smaller ar creating backpressure it going to kill poweroutput/powerband and lower the effiency, thus creating heat, and large ar is is also going to midrange poweroutput/spool.
I vote c. Make the wastegate work correctly in its current application.
for a lack of better words i agree with this. Get a properly matched waste gate and solve boost creep with that. If you're having issues with boost creep instead of swapping housings get a bigger waste gate/dump tube that can flow enough.
I think argument a is very incorrect tho. Increasing back pressure before the turbo isn't making the waste gate more efficient its just making it work harder and have to flow more.
here a psht, there psht, everywhere a psht psht
PVC SQUAD MEMBER #2- 95 CIVIC EX- DD 320whp on a mustang dyno
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PSI2HI;286299 wrote:
Where's the neither option? Both have decreasing benefits in their perspective applications.Smaller AR creating backpressure it going to kill poweroutput/powerband and lower the effiency, thus creating heat, and large AR is is also going to midrange poweroutput/spool.
I vote C. Make the wastegate work correctly in its current application.
SPANISH-RICE;286302 wrote:
for a lack of better words i agree with this. Get a properly matched waste gate and solve boost creep with that. If you're having issues with boost creep instead of swapping housings get a bigger waste gate/dump tube that can flow enough.I think argument a is very incorrect tho. Increasing back pressure before the turbo isn't making the waste gate more efficient its just making it work harder and have to flow more.
Obviously i know that other changes would be more beneficial.... This was strictly a philosophical question of if you could only change the turbine housing AR; NOTHING else.
which change by either going bigger or smaller would help with the problem
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+1 on a properly suited waste gate,and if need be run two or more.
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zbrown;286315 wrote:
obviously i know that other changes would be more beneficial.... This was strictly a philosophical question of if you could only change the turbine housing ar; nothing else.Which change by either going bigger or smaller would help with the problem
bigger
here a psht, there psht, everywhere a psht psht
PVC SQUAD MEMBER #2- 95 CIVIC EX- DD 320whp on a mustang dyno
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haha, i will say i was wrong based on your response's. but i still think for the car me and zac talked about. it would have fixed the problem. but might be bad if generalized for every situation.
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it was a civic with a ls motor. running a afi turbo kit, 57 trim 60/63, v-band 38mm gate.
guy was trying to run 7 lbs and was creeping to 10-11 lbs. Also he is running stock redline 7200 and map sensor.
So i had mentioned switching to the small a/r as it will spool sooner and help wastegate flow. all the larger housing will do in this case is slow down the turbine and increase lag.
So there might be 2 ways to go about solving the problem. but in this case i think the smaller a/r is the way to go.
still think it is crazy it makes 4 psi without the wastegate on at all.
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