Quick parts updates....
Originally Posted by statix
And I was positive someone would now what this means....
Read this link...
I get serious compressor surge on my stock turbo at WOT in 4th under 3K.
under 3.5k rpm's in 5th gear it happens too.
In my humble estimation... who wants to crank it up at that low an rpm anyway...
Dave if whatever you do to "fix" the surge results in a loss or HP or torque; I'll opt for the surge.
Just my personal opinion.
under 3.5k rpm's in 5th gear it happens too.
In my humble estimation... who wants to crank it up at that low an rpm anyway...
Dave if whatever you do to "fix" the surge results in a loss or HP or torque; I'll opt for the surge.
Just my personal opinion.
DAVID, how do you think this 21g would respond with the JDM spec EGR/Anti-Lag setup?
MY Evo 6 has it, but I don't know exactly how it works, and wondering if you know how this EGR/Anti-Lag system works? I believe it's suppose to keep turbo spooled when you're off throttle to give better turbo response when you go back on the throttle & accelerate??
So, I was wondering if it would reduce the compressor surge in the 21g? as it keeps turbo spinning off throttle.
I had disabled my system when I put on the DNP manifold for the EVO 8 on my car....this manifold doesn't come with the ports for the EGR system.
I think I feel compressor surge in low rpms when I stomp the throttle in low rpms since changing manifold.
What do you think about the EGR system & the 21g???
Thanks
MY Evo 6 has it, but I don't know exactly how it works, and wondering if you know how this EGR/Anti-Lag system works? I believe it's suppose to keep turbo spooled when you're off throttle to give better turbo response when you go back on the throttle & accelerate??
So, I was wondering if it would reduce the compressor surge in the 21g? as it keeps turbo spinning off throttle.
I had disabled my system when I put on the DNP manifold for the EVO 8 on my car....this manifold doesn't come with the ports for the EGR system.
I think I feel compressor surge in low rpms when I stomp the throttle in low rpms since changing manifold.
What do you think about the EGR system & the 21g???
Thanks
antilag would make the surge worse. becuase at the same low rpm you'll be making more boost and pushing even more air into an engine (according to 4g63>0000) that can't take the air.
i've never heard of hte egr antilag but if it indeed recirculates the exhaust gases (which is an interesting way to do things) it would have the same effects as a "bang bang" type system. tho bang bang would get you more spool... seems hte egr recirc would be more passive.
thing is... you usually use an antilag system on a turbo that is bigger (hence the need for antilag) or much heavily modiefied to flow more so you won't get these awkward spots. but curing the surge in one respect should prevent it from happening as a result of antilag also... so we're all just banking on an antisurge ring or one of the more elaborate boost control methods.
btw... if you used one of the more elaborate boost control methods you'd never see this surge. once again illustrating if you elim the surge you're antilag will be that much better.
i've never heard of hte egr antilag but if it indeed recirculates the exhaust gases (which is an interesting way to do things) it would have the same effects as a "bang bang" type system. tho bang bang would get you more spool... seems hte egr recirc would be more passive.
thing is... you usually use an antilag system on a turbo that is bigger (hence the need for antilag) or much heavily modiefied to flow more so you won't get these awkward spots. but curing the surge in one respect should prevent it from happening as a result of antilag also... so we're all just banking on an antisurge ring or one of the more elaborate boost control methods.
btw... if you used one of the more elaborate boost control methods you'd never see this surge. once again illustrating if you elim the surge you're antilag will be that much better.
For you guys who get "compressor surge' with the stock turbo, WTF are you doing to make it happen?
I lug my car around ALL the time in 4th and 5th gear around 2k rpms and I've NEVER heard my turbo surge @ WOT (it occasionally does when my stock DV doesn't vent enough, but that happens when you release the throttle), much less would mitsu ever put a turbo in the car that would be mismatched enough to surge at low rpms and full throttle.
I think we have different definitions of "surge" floating around. Compressor surge as I know it, is USUALLY when you have a coldside that is mismatched to the hotside (usually significantly larger). What happens is that the small turbine/hotside spins up the large compressor early which creates a good bit more flow and/or pressure ratio. The compressor wheel requires a certain amount of RPM to retain "traction" on the incoming air at different pressure ratios. If you end up to the left of the surge line on the compressor map, the compressor will compress the air up to a certain point before the pressure becomes too great for the rpm that the compressor wheel is turning, the compressor looses 'traction" on the incoming air and the pressurized air behind the comp. wheel escapes until the PR drops low enough that once again the compressor fins can regain "grip."
Now, thats my definition of compressor surge and I've heard it before on mismatched turbos....it makes a high pitched "chittering" sound when you go WOT, usually at lower rpms. I've NEVER heard my car, or any other evo for that matter, make any kind of sound similar to what I consider compressor surge. HOWEVER, the Evos do seem to transition roughly in and out of boost at lower rpms and higher loads than any other turbocharged vehicle I"ve driven....but thats not because of surge.
Finally, Diverter valves (or BOVS, or whatever you want to call them) can cause compressor surge, but not from a mismatch, nor can they curge mismatch compressor surge (unless you set them up to leak under boost, but thats pointless). Diverter valves that aren't setup to release enough air/pressure when venting will retain the pressure wave that occurs when the throttle body closes abruptly at full boost. If an inadequte amount of air is not released from the system, the pressure wave will bounce back and forth between the still rapidly turning compressor wheel and the TB, giving a sound similar to the mismatch compressor surge.
They sound roughly similar, and ultimately result from the same overload of pressure at XXX rpms, but their origins are very different.
This is correct, no?
I lug my car around ALL the time in 4th and 5th gear around 2k rpms and I've NEVER heard my turbo surge @ WOT (it occasionally does when my stock DV doesn't vent enough, but that happens when you release the throttle), much less would mitsu ever put a turbo in the car that would be mismatched enough to surge at low rpms and full throttle.
I think we have different definitions of "surge" floating around. Compressor surge as I know it, is USUALLY when you have a coldside that is mismatched to the hotside (usually significantly larger). What happens is that the small turbine/hotside spins up the large compressor early which creates a good bit more flow and/or pressure ratio. The compressor wheel requires a certain amount of RPM to retain "traction" on the incoming air at different pressure ratios. If you end up to the left of the surge line on the compressor map, the compressor will compress the air up to a certain point before the pressure becomes too great for the rpm that the compressor wheel is turning, the compressor looses 'traction" on the incoming air and the pressurized air behind the comp. wheel escapes until the PR drops low enough that once again the compressor fins can regain "grip."
Now, thats my definition of compressor surge and I've heard it before on mismatched turbos....it makes a high pitched "chittering" sound when you go WOT, usually at lower rpms. I've NEVER heard my car, or any other evo for that matter, make any kind of sound similar to what I consider compressor surge. HOWEVER, the Evos do seem to transition roughly in and out of boost at lower rpms and higher loads than any other turbocharged vehicle I"ve driven....but thats not because of surge.
Finally, Diverter valves (or BOVS, or whatever you want to call them) can cause compressor surge, but not from a mismatch, nor can they curge mismatch compressor surge (unless you set them up to leak under boost, but thats pointless). Diverter valves that aren't setup to release enough air/pressure when venting will retain the pressure wave that occurs when the throttle body closes abruptly at full boost. If an inadequte amount of air is not released from the system, the pressure wave will bounce back and forth between the still rapidly turning compressor wheel and the TB, giving a sound similar to the mismatch compressor surge.
They sound roughly similar, and ultimately result from the same overload of pressure at XXX rpms, but their origins are very different.
This is correct, no?
mmm i think everyone agrees with you... but there's the more violent type of surge that occurs when your bov doens't open enough or if you don't have one at all... the bucking kind... that was the only deviation from the "opperational" surge that i talked about.
you're right... mitsu wouldn't put a surgy turbo on a car. no manufacturer would... and i don't think anyone said they get surge on the stock turbo... that might be the whole reason why teh wheel doesn't flow more... to avoid surge... as it appears enlarging it slight does cause mild surge in some places.
and i just read up slight on egr anti-lag... it appears instead of the typical jdm bov purge antilag system, the egr system uses a line coming off the cold side of the intake system somewhere nad directs the "fresh air" into the exhaust gas recirc valve to feed the unspent fuels used to keep the turbine spinning... i guess they are saying it's safer and easier on parts because you can just run the car more rich and the unspend fuels will ignite with all the air it needs. whereas the with the bov purge diverted into the exhaust manifold you get more of a violent explosion because you have to inject much more fuel in the environment lacking fresh air. i don't know tho... there's so little information on this.
you're right... mitsu wouldn't put a surgy turbo on a car. no manufacturer would... and i don't think anyone said they get surge on the stock turbo... that might be the whole reason why teh wheel doesn't flow more... to avoid surge... as it appears enlarging it slight does cause mild surge in some places.
and i just read up slight on egr anti-lag... it appears instead of the typical jdm bov purge antilag system, the egr system uses a line coming off the cold side of the intake system somewhere nad directs the "fresh air" into the exhaust gas recirc valve to feed the unspent fuels used to keep the turbine spinning... i guess they are saying it's safer and easier on parts because you can just run the car more rich and the unspend fuels will ignite with all the air it needs. whereas the with the bov purge diverted into the exhaust manifold you get more of a violent explosion because you have to inject much more fuel in the environment lacking fresh air. i don't know tho... there's so little information on this.
Last edited by trinydex; May 2, 2005 at 07:42 PM.
Originally Posted by sethrichmond
I get serious compressor surge on my stock turbo at WOT in 4th under 3K.
under 3.5k rpm's in 5th gear it happens too.
under 3.5k rpm's in 5th gear it happens too.
