I drive an VIII sorry for the typo. I have the stock turbo. Nothing down to the turbo.

 

Hey man I had the same problem. It would cut me out when I slowly built boost on the highway in 4th and 5th. It is your tuning. I took mine to TTP and it worked perfect right after. What tuning do you have? If you are tuned then get it re-adjusted.

 

The reason why its doing that is simple. Its not your BOV, or your plugs. Its your boost settings in your ECU. Creating to much boost in to high of a gear, at too low of RPMs will hit the ECU boost limit for that RPM. You can tune your ECU to not do that, but its bad. It strains the engine allot. Mine will not allow boost past 20spi at anything below 3000rpms, in my top 5th & 6th gear. If I give it WOT at 2500-past 3000rpms it will cause what sounds like a boost flutter out of the BOV, kinda like its relieving the pressure, after it reachs its parameter (3000rpm) its will not flutter anymore. Its just a setting in your ECU that allows the engine not to blow itself up.

 

change plugs . tighten the gap. go back to stock BOV . Turn down boost a few pounds see if it still happens.

 

I have a hallman boost controller so how does the ECU know how much boost I am running. IT will happen at low RPM's then stop around 4000 RPM's.

Getting it re-tuned in about two weeks or so. Won't know till then if this fixes it.

Already done all that still no luck. Maybe this is normal.

I can gun it from a stop go through all 5 gears and have it not flutter but once I am at a cruise speed and need to pass someone and am at 3000 RPM's or below in 4th or 5th and it builds boost slowly it will flutter till about 4000 RPM's. Up till this point I have done most of the simple logical troubleshooting with no luck. Check Plugs and gapping, Boost leaks, Changed BOV, Changed MBC, Even swaped out Boost Guage, Reflashed with old mail-in flash, checked base timing, even moved my source boost to BOV hose from intake.

Hey you never know maybe it could be my driving style like warrtalon would say.

 

It sounds like compressor surge. If it has gotten colder in your area, the higher density of the air may have put you over the surge limit of that turbo with your given mods.

 

I was kinda thinking this but is the only way to stop this without buying a turbo is to lower boost?

 

Or, slow down the spool.

What turbine housing do you have? You could upgrade the turbine, which would probably bring you back under the surge limit, and also reward you with more top end power.

You can also consider the use of a slightly more restrictive intake which may or may not hinder power production.

 

Its the stock turbo nothing done to it. I just don't understand how the stock turbo is doing this, is it possible with my mods? It just does not sound right to me.

 

So, what year is your Evo? If it is a 2003, then your turbo originally came equipped with the 9.8 hotside. In which case, going to the 10.5 hotside(turbine housing) would probably cure your problem.

If you have adjustable cam gears, then going to more retarded settings might also help the situation. Have you tried running a JDM diverter valve instead of the aftermarket BOV's?

A more expensive fix would be to have the turbocharger's turbine blades clipped as well as porting the turbine housing. Upgrading to a significantly larger FMIC, like a Nissei Competition or a Buschur Racing Race unit, might also help.

Finally, you might try running a bit less WG preload if it's set at over 17#, and instead lower it down to about 13-15# by loosening the WGA rod and then dialing back up to your desired boost level with the MBC. Of course, none of this stuff may work....so take it with a grain of salt.

 

he's got an 2005 evo 8.
i believe it's his boost controller. his car was doing this before the cams w/ his boost controller, he swapped it out for a new one, problem went away, he had the cams put in the car, problem was not there initially. the problem than came back. we swapped out my boost controller and didn't change the boost settings so his car would only hit 15-16 psi and it didn't happen.

i'm going away this weekend and when i get back i'm going to put my boost controller on his car and let him drive it around for a couple days, meanwhile, we'll see if his boost controller on my car creates the same problem.

check back monday for updates!

BUMP!

 

[QUOTE]

Quote:

Originally Posted by Evo VIII Black

For the past week at WOT in 4th and 5th @ 19 PSI and up I get a mysterious flutter.

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What is your maximum boost set at on your MBC?

 

I reread this thread and I am tending to think that you may need to upgrade your stock WGA to a heavy duty adjustable unit, such as the Forge, and reset your WG preload to a higher level such as 19# instead of where you have it at 14-15#. At least, try increasing the preload with your stock actuator if it has an adjustable rod.

I had this same fluttering and bucking problem on my TiAl 9.8 HS turbo 'till I upgraded to a fully ported 10.5 HS, and the stiffer Forge WGA. Now, I don't have the problem neither at WOT or light throttle applications. You'll probably have to take your HS off and open up(grind out) the WG bypass port and the transition radius from the main scroll into the bypass port.

Are you experiencing any boost creep at WOT in top gear? This would indicate a WG control problem. Otherwise, if it's not WG related, then probably it is the BOV/DV and insufficient volume or an issue with tuning the internal spring tension. Or maybe like you mention it is an issue wih the boost controller...so, you should try that first.

 

I noticed a similar thing where if I was cruising at say 75% throttle slowly building boost my gauge needle would dance and the car would feel like it was stumbling. Warrtalon explained it to me as part throttle surging that has everything to do with driving style as warrtalon has evidently explained to you.

 

Its set at 20psi and there is no bucking or stumbbling of my car at any time except when I have the Forge BOV on the car at part throttle (It's not on the car now) but wait........

Solution below..........