I have recently noticed the turbo surging after I've shifted. It only surges maybe 3-500 rpms, but I know its not proper. Its not on every shift, only shifts between say 4500-5800 or so. If I take it to 7k, its fine...if I granny shift its fine too. Its that 4-6 range that it surges...and its not all the time either. Its kinda sparatic...

Any idea's as to what I had setup incorrectly that would cause this problem?

I'm running HKS 280 with a Turbosmart VTA bov. I'm thinking its due to the firmness of the BOV being to stiff thats causing it, but I'm not posative.

Ideas?

WARRTALON: I know you diss-approve of my setup(VTA BOV), but its worked flawlessly for me, so I'm happy

 

BOV related problems aint "surge " persay but the abrupt relase of pressurized air un the backside of a sucking compressor.

Turbo compressor surge happens when there is too much demand on benificial properties of air causing it to shear or cavitate instead of building psi. To much blade force on air

 

Hmmm...so what does all that mean I should do? Am I running too much boost? I'm only running 21, spiking to 22 per my Defi gauge.

 

If the bov spring tension is too tight, it won't depressurize the system properly when you lift the accelerator and the throttle plate closes (usually when shifting). This will give the turbo compressor wheel a shock as incoming air suddenly bounces off the closed throttle plate and heads back into the compressor wheel which is spinning at crazy rpms. It's what gives that "chewy chewy chewy" noise.

Another kind of surge (which happens w/o shifting) is caused by the compressor flowing more air than the engine can consume at a given rpm. In this case, you get the same effect as above, only the bov is not what is causing it. This is the kind of surge that was prevalant on the evo8-20g turbos.

Many people have different opinions on what "surge" is and what causes it, but this is what I have come to understand after years of working on dsms, reading threads and talking to people, and testing a variety of bovs.

 

What causes that 2nd type you mentioned 95GSX?

I just sounds like the turbo continues to spool up, for a split second, right after I shift.

Is it unsafe to drive?

 

if it is only happening when you shift or lift the throttle quickly while boosting, then it's probably the bov that needs to be adjusted. It has to open fast enough and high enough to dispel enough air in the system to prevent the surge. When I adjust a bov, I tighten it to the point where it is surging and then drive around and lessen the spring tension until I don't hear the surge anymore.

 

Are You Sure Your Talking About Comp. Surge Or Bov Fluttering. Big Difference

 

Sorry for the side note. What color is your evo S2KSteven? I was wondering if I have seen you around. I live on rolling road.

 

btw the reason it doesn't happen at 7k like you said is probably because the engine is flowing a lot more air than at 4-5800rpm, which aids the bov in depressurizing from the system.

 

It's the turbosmart bov that's causing you these problems. I remember when I had a turbosmart bov on my sti it would surge and stall a lot, you just have to play with the "soft" and "hard" settings until you find the sweet spot. Once you get the right adjustment it should run perfectly. The key is to adjust it just right.

 

It doesn't really make a difference if you ask me. If the spring tension is too tight, that MAY cause the bov to not open properly and "flutter" up and down. ALthough I have never had that happen to me before and have only heard about it from other people. Either way he needs to release some of the tension in the bov to fix whatever noise he's hearing.

 

Alright, I'll mess with the tension then. I figured it was just too firm, but wasn't sure.

Thanks guys!

Deran: My Evo is black....only black one I've ever seen around this area.

 

I have seen you around then. Just wondering

 

Probably...people claim to see me all the time. I'm like the black Evo shadow

 

My stock BOV would do that and it was always at partial throttle on a hill where there was greater engine load. Thats why I installed the APS unit. Never have had a problem since.