megasquirt tuners? low speed bucking?
Discussion
fitted a megasquirt to my old polo as a project
had it running all year , but still fighting a low speed violent bucking
where would you be looking to try and resolve it ?
ive tried a vast range of timing and afr in a block surrounding the problem area , tried ego off , a.e off , decell cut off turned off
had it running all year , but still fighting a low speed violent bucking
where would you be looking to try and resolve it ?
ive tried a vast range of timing and afr in a block surrounding the problem area , tried ego off , a.e off , decell cut off turned off
Maybe driven cycle-to-cycle variation under slow and high vacuum conditions. I've driven production cars that can shunt violently at very low rpm and I don't suppose there's a universal fix for it, but if that was me I'd try richening it up and dropping the timing advance to try to reduce the sensitivity to the state of the intake charge. It'll run hotter and use more fuel, but I doubt you'll care about that. If it works, be aware that might not help you get through an MOT and I'm sure you'll think of a way to deal with that.
steveo3002 said:
all i can see is the rpm suddenly flickers 2-2400 ish , afr becomes unstable
I assume the RPM change is just reflecting the shunting so all bets are off by that point. Can you see any unusual sensor inputs or spark/fuel outputs leading up to that? If you're getting cycle-to-cycle variation I'd expect that to be caused by charge robbing and EGR, and if your data logging is fast enough you'd see that on a wideband. The point of running rich and retarded is trying to reduce the engine's sensitivity to that. But if you aren't seeing any fluctuating load signal or EGO that is provoking this and don't get any improvement from those map changes, I'm out of ideas.aka_kerrly said:
What age Polo + engine are you using? Have you built some kind of pre 1994 1.3 8v with bike carbs or using a later 1994 onwards 1.4 or 1.6 16v engine in a pre 1994 era polo ?
on the 1.4/1.6 engines its the throttle position sensor and or throttle actuator that is often the culprit.
3f +abd bottom end ...3f inj gear , new tps which has a stable signalon the 1.4/1.6 engines its the throttle position sensor and or throttle actuator that is often the culprit.
Edited by steveo3002 on Tuesday 31st August 08:08
steveo3002 said:
3f +abd bottom end ...3f inj gear , new tps which has a stable signal
Cool little setup that. Me and one of my brothers have had a couple of GTs. The most tuned one ended up with a ported head, schrick cam (AMAZING upgrade with a 7500rpm rev limit) , 4 branch manifold, de-cat, 2.25" exhaust, retained the digi management with a "PoloAce" chip , swapped to a Golf GTI 8V digi Air flow Meter with larger intake piping to a ported throttle body. It made over 100hp, pretty much G40 power on a couple of dynos.Edited by steveo3002 on Tuesday 31st August 08:08
Speaking of throttle bodies have you De-wedged your throttle body as this can influence the small throttle input response.
From my experience the engines are so sensitive to issues with the Air Flow Meter and the blue temperature sender which feeds the ECU. The blue temp sensor is one of those items which has to be genuine or high quality, the cheap ones are poop.
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