Greddy bov issues after FMIC

[Toni]

So after installing the FMIC i can't adjust the greddy bov to a spot where it won't go into a nice little "blowing off loop". So basically if I'm in part throttle I can get the bov to open and then if I keep the throttle where it is it continually blow off over and over and it slowely fads in pressure everytime it does. It will stop if I let off throttle or go back on gas. The worst case scenario for this is highway driving in 5th with cruise on because it rarely just lets off the throttle, it eases on/off.

Any ideas?

[i3igpete]

pressure surging. ray fixed it with a balance tube, I fixed it by going with larger turbos and thicker core.

[Chris@Rvengeperformance]

yep,classic case for a balance tube. Adding a little timing at <6 PSI and 2000-3000 RPM can help

[Toni]

Hmm, I have heard of that balance tube however I thought that was when going very large difference in compressor/turbine that had caused the situation. I'll do some reading up on it.

[Chris@Rvengeperformance]

what turbos do you have?

[i3igpete]

yup it's because all of our turbo upgrades are mismatched to help spool up. thats why going td05 fixes the issue, it doesn't build boost at low loads.

from what I've found, going to a 4" core helps by increasing the volume and the resonance doesn't happen anymore.

[DocWalt]

You might be able to get away with a little bit more timing at low pressures like Gump said, or use the balance tube. The turbos are essentially too efficient at that throttle position and surge, and that can be affected by timing, which is why that can work. The balance tube balances out the flow a little before it crams into the intercooler, and will solve it.

On MIVEC engines, you can make nearly any turbo surge by tweaking the timing incorrectly and making it spool too early.

edit: Pete just posted and said it much simpler than I did. :suspect:

[Drweldin]

Balance tubes don't always work. I found best cure(for me) was a dual core. You could also try removing the small spring from the Greddy and/or using the second "push" port that most cap or leave open....

[Toni]

Well I have td04H 15g turbos, I guess that is enough of a mismatch to cause this issue. I still have some extra sensors for when I was going to test pressure drop at various points on the dsm smic but never got around to actually doing it. Maybe I'll do some logs and see what it's really doing.

[Woz]

whats your spring pressure off your bov?

[jbuhrman]

You need a proper BOV that's plumbed back. It's probably screwing up the fuel trims too.

Steve

And exactly what would be a "proper" BOV??? Considering he said he has a Greddy I would tend to think thats proper, open or closed atmosphere shouldn't matter in this...

[Woz]

it doesn't matter, the problem is that it's not opening up at low boost and rpms right? if i read it correctly and he is getting compressor surge a little due to it. sounds to me the spring pressure of the bov is too strong to open up at low boost/rpm. even though i know you said it is adjustable.

[jbuhrman]

it doesn't matter, the problem is that it's not opening up at low boost and rpms right? if i read it correctly and he is getting compressor surge a little due to it. sounds to me the spring pressure of the bov is too strong to open up at low boost/rpm. even though i know you said it is adjustable.


I am going to go with this, s it been adjusted at all so far? I know I had to use a few washers last time I adjusted one.

[Woz]

my friend has the same problem in his 240 and he had to order a new spring for his tial bov.

[Toni]

Sooo I got some data for you folks. Used some pressure sensors with my innovate logger. I placed two between the turbos and core. The other is between the bov and throttle. Here you can see what is happening. Nice to see to real data on this... I should have parts to try the balance tube this weekend and log again to see if there is any difference.

Orange is bov/throttle sensor
purple/brown are turbo/core sensors.

NOTE: bov/throttle sensor was hooked into my lm1 and the other two were on the ssi-4(more accurate). I need to move all three to the same device for complete accuracy.

NOTE: Look couple posts down for new graph...
(http://www.penguinhosting.net/~bigmac/store/logs/pulsingLog02.PNG)

http://www.penguinhosting.net/~bigmac/store/logs/pulsingLog.PNG

[DocWalt]

chug-a-chug-a :p It's awesome to see real data on this, I hope the balance tube fixes it. :)

[Toni]

Yeah it is. I have to move the one sensor to the same device for accuracy. I also think since the two lines are basically the same I'll move one to measure the waste-gate pressure to see what it's doing.

[mh3kgt]

I get the same problem on my 15g vr4 with cx racing fmic from time to time as well. Always seems to happen at part throttle slowly accelerating tho, never when I mash it and go.

[i3igpete]

chug-a-chug-a :p It's awesome to see real data on this, I hope the balance tube fixes it. :)

if it was a pressure wave bouncing between the two turbos, the purple/brown pressures should be out of phase. A balance tube in this case won't fix because they are sync'd together.

[Toni]

Here is the latest log with all three sensors on the same device. Something must have been funny with the ground on the other. Anyway the graph tells a slightly different story. Now the sensors are hooked into:

1)between bov and tb
2)front turbo pre core
3)front turbo wastegate

http://www.penguinhosting.net/~bigmac/store/logs/pulsingLog02.PNG

[DocWalt]

That's the same graph, Toni :p


if it was a pressure wave bouncing between the two turbos, the purple/brown pressures should be out of phase. A balance tube in this case won't fix because they are sync'd together.

Good call.

[Toni]

Oh, I had updated the old one...so that's why they are the same. I reverted it back and made a note.

[DocWalt]

Ok. I'm assuming you've checked your boost controller functionality?

[Toni]

Not yet, going to pull it and run wastegate pressure to see if that makes a difference.

[CoopKill]

Not to hijack, but I have a question that is similar in nature. (if inappropriate let me know, I will start another)

After installing DN hard pipes I get surging when letting off slightly at cruising throttle, mostly 4th - 6th gear. I have HKS adjustable older style, and adjusted some (I screwed in about 1/4 turn). It helped some, but can not mess with anymore until the driveline shows up from 3sx.

Am headed in the right direction with this? Any help is appreciated!

Bill (as I said if this is a prob. I will delete and post new)

[CoopKill]

Did this ever get resolved?

I have now switched to a front mount, and the same surging. I have switched from the hks bov to a greddy and no change. Using a hks evc 4 or 5 controller.

Have you solved you situation Toni?

[Toni]

Not yet, I have been busy with other things lately. I'll probably get back to it when I get back from the NG.