Sideways7

iTrader: (7)

Ever since I got my car running with the new engine it has had high RPM hesitation pretty reliably. It is an s4 car with s5 block and intake. I haven't yet rigged up a way to operate the VDI.
Anyway, I got myself a small air pump (lumbar air pump from a Caprice Classic) and made it to where it would keep the VDI open so I could take it for a test drive. To my extreme surprise, I no longer had any hesitation!
My question is this: why the hell would this happen? It doesn't make any sense to me.

jgrts20

Are you talking about the actuators, cause most of the time at high rpms 3800 or above would be your ports not opening right.

Sideways7

iTrader: (7)

No, this is VDI. It is on the s5 UIM and switches on at 5500 RPM. Basically it changes the runner length.
I have had the aux ports wired open, stuck closed, and working properly and it never caused hesitation. That is partly why I am so confused about this. I guess maybe the runner length has something to do with it? I dunno. Its still on the s4 ECU so it shouldn't care about the VDI.

Sideways7

iTrader: (7)

I guess I forgot to specify, but the hesitation started at about 5.5k-6k RPM depending on the gear.
Anyway, now that the VDI is on this thing is a rocket! I had forgotten just how fast it is. I also figured out that my aux ports aren't opening until like 6500 rpm.....

jgrts20

wow, isnt that alittle bit high to be opening? especially when we tach out at 9000. AS for the VDI, i guess I dont understand what it is I have a S4. Sorry I saw hesitation and though it might of been the ports. I will shut up now.

Sideways7

iTrader: (7)

Well, since I still use the s4 ECU, my rev limiter is actually set at 7800, so I barely have time after it really kicks in. And yes, that is very high. It should be opening at 3800 or so. No wonder my car has been feeling so sluggish.