Boost Leak Questions

[seano700]

Hi guy's

I went out for one last ride last week. Sled ran good but no matter what I did I could achieve 12lbs boost, (was running @ 10lbs). I opened my bleed valve (boost controller right up) and then shortened up the linkage to my wastgate. Still only 11lbs boost. Once I got home I found my idle air control line had popped off leaving a half inch hole in my intercooler. Problem solved. I was talking to a buddy about it afterwards and left the conversation with a few questions.

Lets say at 10psi boost an engine makes 10 hp (no boost leaks, everything is perfect). Now lets say the same engine is still making 10psi boost but has a boost leak (like I did) how much power does it make? According to my buddy it will make less power due to inefficiency of the turbo. To me boost is boost, but I am certainly no expert on the subject. Any insight you can provide would be appreciated. I would just like to wrap my head around the whole situation. Thanks Sean

 

[zebiraross]

Your buddy is right. With a boost leak your turbo has to overwork to produce the 10 psi that it would nornally achieve with out a boost leak. Doing this takes it out of it's effeciency.

 

[seano700]

Boost leak

Your buddy is right. With a boost leak your turbo has to overwork to produce the 10 psi that it would nornally achieve with out a boost leak. Doing this takes it out of it's effeciency.

Ok, so being efficient will make more power at any given boost level then? How much power can efficiency account for? Thanks for your reply zebiraross. Sean

 

[powderlites]

Power with boost leak

It's all about effcency right from cam timing, porting, intake, exhaust and turbo.
You can see Apex's on the dyno go from 310 HP to 360 HP with same boost and different setups.
See Hurricane make over 400 HP with 20 psi boost!
Most guys runing Apex's at 20 psi boost are not even close to that.
I feel that with our FX Nytro turbo kit we are getting pretty effcent setup and it shows on the dyno.
Stage 1 with Dobeck box and then change to Rapid bike 3, stage 2 and holycow things start to happen with same boost.
http://www.powderlites.com

 

[zebiraross]

Ok, so being efficient will make more power at any given boost level then? How much power can efficiency account for? Thanks for your reply zebiraross. Sean

Dave is right. But specifically with effeciency of the turbo. Basically with a boost leak your turbo is out of it's effeciency range that means you have a WAY higher intake temp. It works like this HP Output = +1% HP per 10 degree temperature decrease-1% HP per 10 degree temperature increase. Example: 330 hp engine at 160° intake temp vs. 349.8 hp at 100° intake temp. Intake temps are HUGE.

 

[Duke]

Dave is right. But specifically with effeciency of the turbo. Basically with a boost leak your turbo is out of it's effeciency range that means you have a WAY higher intake temp. It works like this HP Output = +1% HP per 10 degree temperature decrease-1% HP per 10 degree temperature increase. Example: 330 hp engine at 160° intake temp vs. 349.8 hp at 100° intake temp. Intake temps are HUGE.

So what if your intake temp was near 32 degrees F and your airbox after intercooler builds frost on it on a cooler day, does that mean with 1% HP/10 degrees, you would have roughly 374.29 HP with the same boost ??

 

[zebiraross]

So what if your intake temp was near 32 degrees F and your airbox after intercooler builds frost on it on a cooler day, does that mean with 1% HP/10 degrees, you would have roughly 374.29 HP with the same boost ??

Probably for a pull, then your intercooler will get heated up signifacantly. Even through a pull your intake temps are going to rise with the heating of the intercooler. Some nice BIG intercoolers that we dont have the luxury of running with our sleds will actually take intake temps close to ambient for a very long time, but with enough time will eventually get heat soaked. The intercoolers we use with our sleds get heat soaked pretty quick.

 

[Duke]

Mine always stays cool, that probably explains why I had to make adjustments after dynoing, I had to make adjustments on RB3 box after running on hill. Also explains why other conventional kits cant run the timing and fuel mapping I can ??

 

[seano700]

Boost Leaks

Wow, thanks for the great responses guy's!!! Makes way more sense now keep up the good work!!! Sean