Car feels weird at High RPMs

[xrobbx03]

My car seems to be driving fine in the lower gears and lower RPMs but when i step on it in the higher rpms then let my foot off the gas the engine sort of bubbles and the whole car sort of bounces a little bit.

What could be happening?

 

[Mikelb]

Well, from looking at your mod list, you haven't said anything about a MAF. It shows that you have a BOV, I'm assuming that you are venting it and not recirculating. This is your problem. The stock intake sensor meters air before the turbo, the ECU compensates giving the engine the right amount of fuel, when you let off the gas, the BOV opens, and the car runs rich for a moment. That causes the car to stumble.

http://www.dsmtuners.com/forums/showthread.php?t=89260&highlight=vent+bov

That thread describes the differences of venting and recirculating...
With the stock MAS, don't vent. It's just not a good idea, you might want to look into a GM MAF, then you can run it after the BOV and vent all day long (with less restriction).

 

[xrobbx03]

Yes I do have the stock MAF and I am recirculating it. Since its the stock one I didnt think that I needed to put it in the mod list.

I know not to vent it unless I have the GM MAF setup.

 

[Mikelb]

ok, well that was my first thought... explain "the engine bubbles..."

 

[xrobbx03]

Its hard to explain in words, But the engine bounces with a lil bubble sound. The higher the rpms are when i let of the gas the more noise and bouncing there is. Maybe back back pressure, but i have a 3" exhaust along with the Apexi N1 downpipe with a high flow cat so i dont see why i would be getting that much to make my car bounce. Although I do have the stock O2 housing there.

 

[Mikelb]

ah, I think I know what you're talking about. Do you have a boost gauge? I didn't see one listed in your mod list.

I think it's your wastegate opening. Mine does that when I hit about 17psi (boost set at 16.5).

Get you a boost gauge, and you should be able to see the boost gauge jumping around a little.

 

[xrobbx03]

ah, I think I know what you're talking about. Do you have a boost gauge? I didn't see one listed in your mod list.

I think it's your wastegate opening. Mine does that when I hit about 17psi (boost set at 16.5).

Get you a boost gauge, and you should be able to see the boost gauge jumping around a little.

yeah I do have a boost gauge. And your right my gauge does bounce around a little up in the higher rpms. So this is normal?

 

[Mikelb]

If the needle on the boost gauge bounces when you feel this, then I'd believe it's just the wastegate. That is normal.

Easiest way to tell is, whatever you set your boost to, the needle on the boost gauge should go a little higher, then this starts and it fluctuates right around your preset boost.

Should be nothing to worry about.

GL and happy boosting

(I'm still going to keep searching for a little while, making sure there are no anomolies out there that we should be aware of, but I'm almost certain that's what it is).

 

[xrobbx03]

ok thanks alot.