I have been trying to get rid of my partial boost ( > .5bar) to full boost knock, and noticed that nothing i did to the timing table would get rid of it. I have already made room around all my heat shields, and made a nice open area for the DP to sit, and am still getting some kind of knock when i go from partial to full boost.

Today (and last night) i was noticing that the Diverter Valve will flutter at any level of boost from 0-.5 bar. Then i tried making it flutter over and over, and the knock light would turn and i would get 1-3 counts of knock on occasion. I havent been able to consistantly re-produce the knock, and im thinking this might be why.

has anyone else had this happen? too much flutter will cause 1-3 counts of knock?

 

I have the exact same problem with the IX bov

 

^what did you do to fix it? people are telling me to 'T' off the turbo nipple, and send that to the DV instead... but i wonder what that does to the BCS.

 

the DV or BOV needs to see vacuum, also make sure that there are no other lines T'ed into the vacuum line going to the DV from the intake manifold

which DV is it?

 

^the stock one. I was thinking the same thing when people told me to "t" the boost line... it never sees vac.

p.s. nothing is teed into the DV line. all stock.

 

Its compressor surge......it happens. The stronger the dv is the more it can surge at low boost - part throttle you just learn to drive around it. Also its more prone to happen in cold weather as well.....

Did you try taking some timing out in the load areas from part throttle to wot? I had to take a degree or 2 out because I was continually getting knock going into boost before peak load. I think i did load cells 100-160 / 2000 to 4000.

 

if its surging on the stock DV, check for boost leaks it can cause the turbo to work harder.

but I agree with travman with taking timing out

 

i had same problem you can try to keep the same timing and learn to stay in the high rpm. I notice if i drive in 3rd in the 4000rpm range it wont knock, if i drop it to 4th in the 3-3.5k rpm range it will induce knock.
another thing that helped was changed the closed loop tables.
also i have found a little decrease in MIVEC helped also, i had to much aggressive MIVEC i guess.

 

yea, i tried taking out 2 degrees, then 4 degrees, then 10 degrees, then setting it to 0 and nothing changed it.

I guess it could also prolly be too advanced Mivec as well. And i have changed my Openloop load table to 70 in that area, mainly because i was having a problem with the car stuttering and not going out of closed loop when i was getting full boost at 2500. The O2 sensors would actually shut off completely during that time...lol. changing the open loop fixed it.

and, im 75% sure that there arent any major leaks. I should break out the tester again and see if any new leaks may have developed, i used to have a problem with the piping leaking right at the TB. maybe its doing it again...

and this is the first time i really noticed the audible surging...so maybe it could be a leak from taking out the airbox to do the GM3-port install.

and FWIW, my car looks completely stock. Everything in the engine bay is stock except the BCS and filter.

 

Is a couple counts of knock at that load something to even be concerned about?

 

^yea, exactly what i thought...but it does affect overall timing. i.e. if your coming out of a slow turn and getting on boost at a track, if you knock 3° then it pulls 1° of timing out across the whole RPM range.

...thats my only concern, ~10 less whp cause of a DV fluttering ...lol. that could easily be the difference between 1st and 10th...

 

I've consistently seen the IX pull 1º for every 1 count and then another 1º at 3 counts. The IX doesn't play when it comes to safety. Octane still drops after 6 counts.

If you stay on the throttle after the knock is gone the timing comes back almost instantly though ... so you'd only lose that power for a second or so. Even if the octane value drops, heavy throttle makes it recover quickly.

It could be the MIVEC settings as well ... I tuned a car this past weekend with BC 280s and it would peg the knock sensor at 35 with my stock cam MIVEC map even at part throttle. It as false knock though as there was nothing audible. I pulled it down in the cruise areas and brought peak down to 26º and it was golden.

 

^thanks touringbubble.

...id hate to get rid of the mivec i have... that means no more 20psi@2500 in 4th 5th or 3rd uphill...

Im gonna throw the car up on a lift over the weekend and doubletripple check all the shields. I used to ahve a problem with the Tanabe dp hitting my beatrush tray at low RPM as well. a body hammer and elbow grease should give the dp a lil more room. Might as well heat wrap it as well to prevent any rattles from it.
Also, I think my garageghettofabbed testcat might be giving me some rattles during hard cornering anways.

And, yes i also noticed that 1° of knock = -1° timing on this car. Its wierd, but safe i guess...
(which reminds me that i need to learn more about the dynamic timing stuff)
anyone have suggestions on a different DV? id hate to get rid of such a great DV that gives 0 problems, for a fancy deer whistle thats gonna give me tuning headaches.

 

I've heard of running your bov/dv line to the lower intercooler piping, and that will solve the flutter problem. I have not done that yet, but want to, as I too have the DV flutter, when in part throttle.

 

Definitely make sure you don't have any vacuum leaks anywhere at all. Especially on the hose going to the DV.

The DV needs to be hooked up on the backside of the throttle body. Hooking it up anywhere before the throttle body will cause serious compressor surge. The vacuum helps the valve fully open (like a suction) when you let off the gas. At the same time, when you are boosting and the intake manifold has boost pressure, you are adding force on top of the DV to keep it closed.

Personally, I would never accept compressor surge of ANY kind in my car, partial boost or full boost. The correct BOV setup is far cheaper than a new turbo.