Stumbling Under Boost?

quattrodave · Post by **quattrodave** » Sun Jul 09, 2006 1:43 pm

Hiya Guys,

I'm in the process of tuning my first Megasquirt project

so far all's gone reasonably well. I'm now a bit stuck tho, the car runs fine and puls well up untill boost starts to come in, all of a sudden it starts stumbeling / misfiring. I've tried more fuel, i've tried less fuel, nothing makes any difference and the wideband sensor reads rich.

I've gone thriugh my settings and cant see any mistakes... Any ideas would be gratefully accepted.

Many thanks.

MS2 V3 Audi Quattro Turbo.

Uncle Bob · Post by **Uncle Bob** » Sun Jul 09, 2006 7:23 pm

I'll say what others will probably say here anyway....post your build.

But....if you haven't done it already, check your plug gap, and make sure its at most .030"....usually it takes more boost than that to blow out the spark, but it can be an issue...

quattrodave · Post by **quattrodave** » Mon Jul 10, 2006 2:26 am

Thanks UncleBob,

Excuse my inexperience, what info would you be after ?
It may well be on here.....
http://www.toffnet.net/MS/audi.html

Many thanks

Dave

rs2000 · Post by **rs2000** » Mon Jul 10, 2006 2:38 am

Uncle Bob wrote:But....if you haven't done it already, check your plug gap, and make sure its at most .030"....usually it takes more boost than that to blow out the spark, but it can be an issue...

Thats what i was going to suggest

keithmac · Post by **keithmac** » Mon Jul 10, 2006 5:09 am

I had a similar fault and it was down to plugs, both sets were Denso Iridiums, both gapped the same but the 2 grade colder plug worked at higher boost where`s the hotter plug didn`t, wierd!

quattrodave · Post by **quattrodave** » Mon Jul 10, 2006 7:16 am

Thanks Guys,

I dont think i explained my self properly, before i installed megasquirt it boosted A-OK, although i have checked the plug gap. But more to the point as soon as it tried to boost i get really bad misfire, this is at 0.1 bar ( checked on 2 different guages ).

Also if you open the throttle quickly it misfires.

I'll get a log this evening....

Many thanks

Dave

keithmac · Post by **keithmac** » Mon Jul 10, 2006 11:07 am

Strange, have you tried altering the VE in steps of 10 where the fault occurs in the VE table? If it`s missfiring the Wideband reading will be useless you may have to do it by feel until it`s somewhere close.

Have you had a look though all your settings in review mode to make sure boost control/ spark retard etc aren`t turned on?

Could maybe be a dwell problem, weak spark?

quattrodave · Post by **quattrodave** » Mon Jul 10, 2006 11:42 am

Hiya,

I'm only using MS to control fuel at the moment. The original ECU is controling the ignition....

Many thanks

Dave

quattrodave · Post by **quattrodave** » Thu Jul 13, 2006 9:56 am

Hiya guys,

Just to tie this thread up; I started my MSQ file again from scratch reworked out all constants, retyped everything and hey presto it's solved all my problems.....Strange eh ?! Car feels soooo much better.

Many thanks to all involved.

Dave