Slight bog between shifts, dont think it's turbo lag

[Guest bastaad525]

Okay, I mentioned this in another thread, but now that I think about it, this problem doesn't relate to my question in that thread.

 

 

Basically I'm noticing some serious bog after shifting when trying to accelerate quickly. I dont think it's turbo lag as the boost seems to come back on almost instantly, but it definately feels like turbo lag. It's pretty brief, maybe like a half a second before the car feels like it's back 'on' again. I have my BOV recirculated, so I dont think it's anything like running super rich every time I let of the throttle or anything like that. Whatever it is it's making it feel like it's shifting 'mushy', it doesn't HIT into the next gear the way my N/A used to, which would shift hard enough to chirp second, third, and many times even fourth gear, whereas with the turbo it will rarely even chirp into second, even though the turbo is putting 30 more hp and 70ft lbs of torque more to the wheels! While I'm sure the rest of the drivetrain is happy to not be dealing with that kind of shock, I'm sure it's not helping my performance any. Oh, my timing is set to 18* BTDC, 2 degs retarded from stock. When I tested on the dyno, the car was running rich up to about 4000rpm, at 10 or 11:1, but after that would lean considerably, to about 13:1 by 5000rpm. Considering I shift at either 5000 or 5500, I dont think it's richness that's causing the bog, but of course it may peg super rich as soon as I let off the throttle for whatever reason or peg super rich when getting back on the throttle.

 

Anyone with any ideas for what I should start checking to fix this?

[SleeperZ]

Don't let off the throttle

 

 

 

j/k, thought I 'd throw that at ya.

 

I'd try to confirm with an a/f meter or something if it is hitting rich - has your AFM had the tension changed? Not sure what else to check.

[Guest bastaad525]

You know... I dont know why but with this drivetrain I have been scared to power shift it. I used to do it a lot in my N/A, but I just can't bring myself to do it with the turbo. I have adjusted my AFM very slightly, a couple teeth... I can't say if it had been adjusted before I got to it, but if it had been, it hadn't been by much... anything more than three teeth of adjustment in one direction or the other and the idle gets pretty rough... not a whole lot of range to play with. I tightened it up just a little to smooth out the idle and also to help alleviate some of the super richness (10:1) I was getting once boost came on when I dynoed. A couple teeth tighter and the idle has smoothed out noticeably, I haven't been back to the dyno so I dont know what effect it's had on AFR.

 

I guess I will wait until the next time I dyno, and see if I can get them to floor it in second, take it up to where I usually shift and hit 3rd, and I'll watch the A/F on the monitor and see what it does. Unfortunately it will be a while before I go back

 

On a side note, is there a standard way that you guys use to check for boost leaks? There's a lot of whooshing going on under hood when the boost comes on... doesnt feel like it's leaking, and the dyno results tell me I'm fine... but I mean it definately is LOUD in there. The only other turbo car I've ever been in, the Supra TT... I dont remember it making that much noise when it came on... not that I was listening too closely. Without a real point of reference I'm not sure what sounds are normal or not.

[SleeperZ]

Yes, boost leaks can do that, now that you mention it. You can always try to spray flammable stuff around your pipes and listen for the idle speed to change. That may or may not find boost leaks. I had some leaks at first, and ended up checking all the connections, and repairing some. I had a big leak on the outlet of my DSM BOV - I didn't consider that a problem until I heard the valves are supposed to leak a little bit at idle. I also found that my air regulator had blown out it's bimetal strip (the long bit with the electrical connector). Since I repaired those two leaks, my car was much quieter under boost.

[Guest Peyman88zxt]

From my experience when tuning my car, both going lean or rich can cause that condition. Usually when you first get on the throttle the change in airflow characteristics causes some fuel to momentarily stick to the port walls and cause a lean condition. Most ecu's monitor throttle position and if they see a sudden change in throttle position, they momentarily richen up the mixture. I'm not familiar with the older Z ecu's and if they correct for that and if so, if they use a tps or change in the airflow to sense the condition. If the condition is drastic enough for you to be able to feel it, even with a narrowband oxygen sensor you should be able to tell if you running too rich or too lean.