Bodging Butterfly to increase Idle RPM ?????

poormansporsche

before the "noooooooooooooo dont do it" start i will just explain my reasoning

basically some of you may have seen my other thread about lumpy cams without going in to too much detail my current idle tickover is around 550 RPM and i sit in alot of traffic and i really need to get the idle upped to say at least 1000 RPM which would normally only be acheived by changing the fueling etc by a remap. As ive got a 2.4 TB on order there is no point getting a remap at this stage til the solution is sorted for that. Ive got a ported 2.2 TB on the car at the mo plus ive got my original TB sitting in the garage doing bugger all. So i was thinking that a quick fix to up the Idle RPM would be to maybe shave of a tiny outside edge of the butterfly to allow more air into the engine on tickover and hope that the ecu adjusts the fueling to match. I know this will fook up the TB but it doesnt matter to me or am i getting completely the wrong end of the stick.

Any thoughts would be appreciated especially any ideas how much to shave off or whether to take out say maybe the "ridge" by the butterfly will be better

thanks

Brett

Daz

Ummm....might find the ecu will correct the idle....i cud be wrong tho....

Lightning_Coupe

I was watching my throttle today whist the car was on tickover and I found the TB to be permamnently twitching and contributing to the lumpyness (its quite impressive just how fast it moves!). I think that perhaps the lumpy idle is partly due to the ECU looking at the MAP pressure thats not stable due to the cams and trying to correct it all the time with the TB which just attenuates the lumpyness further.

Shaving the TB will just feck it up in my honest opinion. People have gone a little too far porting the TBs before now which brought the ecu light on and I'll bet if you touch the butterfly it will do the same. Introducing a leak in other ways will just cause the TB to close that little bit more too, and will effect the long term trim.

What does concern me a little is the very low idel speed you have as standard. Mines always been around 650/700rpm from factory, 500rpm seems very low indeed. I know Ian at MPG has the dbilas cams fitted and Im sure he said something about raising the idle speed. Ill ask him tomorrow for you and see what he did?

vocky

personally I would remove the inlet manifold, clean the mating surface on the head and refit the manifold.

rabidh

IMO the ECU should always adjust the tickover to 800rpm - if it can't then there's probably something else wrong, and taking a bit out of the TB might not help matters (although it could work I guess).

If it is the air pressure fluctuating then you could take your sensor out, and put it on the end of a piece of pipe with a restriction in it - that should even out the variance in air pressure.

alanoo

Just one thing

Tickover is not only adjusted using the throttle position but with ignition advance changes too 😉
(meaning that modding the TB may not change anything at all)

poormansporsche

well done it today - shaved about half a mm off and didnt make any difference at all due to the lip of the "ridge" - so shaved a tiny bit more off and got the EML of doom and the car sounded like steam engine !!