[feckman]

All,
So, I'm having some slightly weird stuff going on with my car. I initially thought it might be an indicator of the MAF starting to go south, but now I'm thinking that it's actually either (a) the diverter valve or; (b) not a problem at all.
Basically, there's what feels like quite a bit of turbo lag that I never noticed before, sometimes followed by a really strong surge, and I'm not sure where it's coming from. I've been running the car chipped with a hyperboost DV for about 1,000 miles or so, and with a new TT turboback for about 300. My best guess is that it started after the turboback install, or at least that's when I started noticing it.
I tried roadsleeper's (Adrian's) MAF cleaning thing, and it didn't seem to help much, although it didn't seem to hurt anything either.
This weekend I installed an AEM CAI, and I noticed something really paculiar that I'm just not sure is right, and that I'm hoping is the source of my problem (lag, absence of proper boost).
Here's the deal -- I'm comparing this to another guy's car (BrandonC) which has an open element intake. Although not exactly the same as the CAI, it seems to me that it should be a pretty good comparison. I rode in his car before I got the CAI.
Anyway, when I accelerate, I get this very, VERY definite wooshing sound from the CAI, followed by the big (and I think normal) PPPPSSSSSHHHHHTTTT when I let off the gas to shift. When I accelerate hard, the noise seems to be a bit less, and when the noise is less, the car seems to pull much harder. It's possible that at hard acceleration I'm just not hearing it as much because of the engine noise.
It's like this:
sssssssssssssssssssssssshhhhhhhhhhhhhhhhhhhhhPPPPSSSSSHHHHHTTTT
I don't remember hearing this in Brandon's car, just the PPPPSSSSSHHHHHTTTT part at shift points. However, I guess I wasn't really listening for it, though.
Is it possible that I'm venting boost when I shouldn't be? I mean, it seems to me that the wooshing sound could be one of two things -- either the car breathing heavily (e.g. sucking air *in*), or venting off boost. If this is the case, I imaging the DV would be the place to look, right? Basically, I guess the question is, should I actually hear the CAI while accelerating?
Anyway, thanks for any info. I hope this is it!
--Jim.


[Modified by feckman, 3:37 PM 8-5-2002]

 

[MRP2001GTi]

Re: Bad DV or just not used to the CAI? HELP!!! (feckman)

The noise will be loudest if you plan your deceleration or lifting of the throttle during the boost spike, say 2500 to 3000 RPM, during WFO acceleration and shifting at higher RPMs there is much less boost to vent so the noise is no where near as loud. If you roll your windows down and drive next to a wall or curb you can actually hear the DV go through all its movements. Taking off from a idle and with very light throttle application yo can actually hear the boost start to come on and rush by the OPEN DV and hear it fade as the DV closes (as more boost is reached) then if you let off at 3500 rpm or so after slowly mashing it to the floor (building boost) you can hear the loud woosh.

 

[feckman]

Re: Bad DV or just not used to the CAI? HELP!!! (MRP2001GTi)

quote:[HR][/HR]If you roll your windows down and drive next to a wall or curb you can actually hear the DV go through all its movements. Taking off from a idle and with very light throttle application yo can actually hear the boost start to come on and rush by the OPEN DV and hear it fade as the DV closes (as more boost is reached) then if you let off at 3500 rpm or so after slowly mashing it to the floor (building boost) you can hear the loud woosh.[HR][/HR]​

Okay, so then I should basically hear a woosh when starting out until the DV closes and then I should hear nothing until I shift (or let off the gas) and get the PPPPPSSSSHHHHTTTT, is that right?
I'm going to go out to a big warehouse club now and drive next to a wall to see what happens. Thanks for the info, and I'd love to hear any other input!
--Jim.

 

[BrandonC]

Re: Bad DV or just not used to the CAI? HELP!!! (feckman)

Jim -- I'm going to guess that you're hearing the whoosing at part throttle, right? I think what's happening is that you're hearing the Dv venting some of the boost back to the intake because it's not closed all the way. Since you're only at part throttle, there's still a little vacuum in the manifold and it's pulling the DV open a little ways.
I hear the same thing with my intake, so I don't think it's a problem. Part throttle in 1st and 2nd gear is especially noticeable. If you drive it lightly until you hear the sound, then floor it, it should go away and be replaced by the nice intake (and no DV) sound, until you let off the gas.

 

[feckman]

Re: Bad DV or just not used to the CAI? HELP!!! (BrandonC)

quote:[HR][/HR]Jim -- I'm going to guess that you're hearing the whoosing at part throttle, right? I think what's happening is that you're hearing the Dv venting some of the boost back to the intake because it's not closed all the way. Since you're only at part throttle, there's still a little vacuum in the manifold and it's pulling the DV open a little ways.
I hear the same thing with my intake, so I don't think it's a problem. Part throttle in 1st and 2nd gear is especially noticeable. If you drive it lightly until you hear the sound, then floor it, it should go away and be replaced by the nice intake (and no DV) sound, until you let off the gas.[HR][/HR]​

Hey Brandon!
Weird to be talking to you so far from our hometown forum!

Actually, I just took a few passes by Home Depot in Albany, and it seems to me that the DV may be sticking. To answer your question, yes, it is definitely more noticable at 1/2 throttle or so. At 1/2 throttle, it pretty much always does it -- I hear the noise all the way up to 5500 RPMs or so. However, sometimes I can hear the venting under hard acceleration, too, as if the DV is open and just venting away. Other times, it seems to work "right" and I get tons of power right away. Then, yet other times, it seems to be venting and it will all of a sudden snap closed and I get a big boost of power. It's definitely hard to pin down a particular pattern, so that makes me think it's the DV doing something weird. What do you think?
I'm going to open it up tonight and see if there's enough grease in there. I may also test my stock DV to see if that does the same thing. I talked to the guys at Stratmosphere, and they said they'd take care of it either way -- send me more grease or send me a new valve. http://****************.com/smile/emthup.gif http://****************.com/smile/emthup.gif
--Jim.

 

[MRP2001GTi]

Re: Bad DV or just not used to the CAI? HELP!!! (feckman)

Try mounting it backwards too. Pressure side on the bottom of oposite side from the small nipple.

 

[feckman]

Re: Bad DV or just not used to the CAI? HELP!!! (MRP2001GTi)

quote:[HR][/HR]Try mounting it backwards too. Pressure side on the bottom of oposite side from the small nipple.[HR][/HR]​

Really? That won't cause a problem? Maybe I'll give it a shot...
--Jim.