Quick rundown, Evo 8 with forge rs adjustable valve. I get flutter under partial throttle let off, never on full boost throttle let off. According to their site that is normal. Any help? Is that actually normal or am i hearing comressor surge.

 

Valves don't flutter, It's compressor surge. The spring is too tight and won't allow the valve to open unless a lot of air slams it open.

 

That what I thought but the forge site says completely otherwise.

 

I happen also use the forge rs. When it's too loose it doesn't close soon enough; when it's too tight, it surges. Just for kicks, what does the site say?

 

Each user will need to adjust their valve so that it will hold boost all the way to the specified redline of their application under wide open throttle without experiencing any valve fluttering at full-boost throttle lift.
If valve fluttering is felt at full-boost throttle lift, this is typically an indication that the valve is adjusted too stiffly.
If the valve is leaking under wide open throttle before the specified redline of the application is reached, this is typically an indication that the valve is adjusted too softly.
Please note that valve flutter under partial throttle conditions or partial boost throttle lift is a normal occurrence as IS NOT an indication of compressor surging. Partial throttle or partial boost val ve flutter is solely an indication that the valve is responding to an inconsistent pressure differential on either side of the throttle body as it is being modulated. Compressor surging would only be experienced if full-boost throttle lift valve flutter is experienced and is not corrected immediately.

 

That's ridiculous. If you remove the bov altogether and plug both holes it will make the same sound and performance situation. Whoever wrote that for forge clearly isn't an engineer.

I like that it goes into "inconsistent pressure on either side of the throttle body". When airflow becomes inconsistent and puts resistance on turbine flow it makes the fluttering sound. It has nothing to do with the valve.

 

Made no sense to me either. So no matter how they word it, its indeed compressor surge.

 

Technically it's only compressor surge when you are under boost. The flutter still isn't good just need to adjust the BOV more

 

Well I had it dialed in perfect. No flutter under partial boost throttle let off nor full boost throttle let off. Then I read the site and got confused

 

The compressor surge you have to watch for has a metallic sound to it and occurs when your on the throttle in boost. You can search on YouTube for some of the good videos that show the difference.

 

Neer heard of ON throttle surge. Whats the difference between on throttle surg and off throttle surge?

 

Lookup a video that synapse did on YouTube called true compressor surge. As the rpms climb you start to hear the fluttering before they lift off the throttle

 

Surge can exist at high or low power levels. The physics is the same, and the sound is the same. At higher boost/airflow levels it holds more potential for damage because the forces are greater.

It's like claiming that if you hit someone with a car that its only called "hitting someone with a car" if you're driving fast.

 

Alot of good advice, thanks everyone. I got my vale properly dialed in, its perfect now. Another question, say you take a regular evo, put a bunch of new mods onto it without getting a tune(full TBE/cams/intercooler/etc) would this cause the car to easily hit fuel cut even if the boost level was kept the same? As in 4-5k wot sputter/fuel cut. Whats the dangers of running that setup without a tune...this is all for imformational purpose coming from a new evo guy. Thank you

 

You will defintely hit fuel cut with those mods, I upgraded my exhaust, intake, then put on a test pipe, and I was hitting fuel cut. The stock fuel map is uber rich so it'll keep your engine relatively safe, but you'll definitely want to get tuned as soon as possible, hitting fuel cut isn't fun, feels like it puts alot of stress on the car.