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Home > Help Needed / General Tech Chat > Fueling at start

JackZwiebel

19 Posts
Member #: 11786
Member

Hey guys,

I am still tying to get my fueling right, and at the moment i dont really know where to start.
I have a HIF44 with a BCA needle (as far as i can remember). Part throttle lean off is connected.

The engine starts perfectly fine and idles smooth - just a bit rich (AFR 11)
Now the problem: when i put in the first gear and dirve away the engine rattles and leans off - to AFR 15-16.
As soon is the clutch is all in and i am driving it is normal again with AFR 11-12.

It leans off a bit if i quickly accelerate and when boost sets in (AFR approx. 14.) and then runs at AFR 12-13 at load/boost. I am running 10psi boost - is the AFR ok under boost?

What can be the cause of the rattling at the start - is it fueling or maybe the clutch? Never had a problem with the clutch befor.
I thought it may be the dashpot oil, but i am already using a thick gearbox oil. Any suggestions?

best regards


JT

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2688 Posts
Member #: 637
Post Whore

Hertfordshire

Try the standard bdd needle and block the part throttle lean off.

Edited by JT on 13th Mar, 2019.

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985


JackZwiebel

19 Posts
Member #: 11786
Member

The BDD is a bit leaner at the top - so i would get richer at bottom. Do you think i run lean when starting and thats the rattling? But why does it idle so rich then?


JackZwiebel

19 Posts
Member #: 11786
Member

The part throttle lean off didnt change anything at start.

Is it possible that im getting so rich when starting that i dont have combustion at one cylinder - and therefore have that rattle and the lean reading on the AFR...since not combusted air comes through?


JT

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2688 Posts
Member #: 637
Post Whore

Hertfordshire

Have you tried adjusting the idle mixture screw on the carb?
Anti clockwise for rich, clockwise for lean.

Edited by JT on 16th Mar, 2019.

My build thread..

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=542985


JackZwiebel

19 Posts
Member #: 11786
Member

I have now adjusted the mixture a bit to lean. also changed the damper oil to 20w50. It idles now at 11.5 and idles way smoother. The rattling is (almost) gone. The afr while driving looks good too.
Running quite rich at cruise (11-12). when the boost sets in it gets a bit leaner....running at 12.5-13 at boost but not full throttle (didnt try that yet).
Guess thats ok so far? Dont want to make it more lean on the screw since i would get too lean on boost.

One thing i have noticed and dont really understand:
Since i blocked off the part throttle lean off the pressure of the flow out of the exhaust is waaaay lower. Also it idles smoother.
Befor you could still feel the wind from the exhaust over 2meter away. Now you can only feel it in a distance of maybe 40cm.
Anyone has a explantion for this?

Edited by JackZwiebel on 19th Mar, 2019.


metroturbo

752 Posts
Member #: 989
Post Whore

North Yorkshire

The rattling isn't pre-ignition, is it? Are you using a distributor or mapped ignition?


JackZwiebel

19 Posts
Member #: 11786
Member

I'm using the standard metro turbo distributor and i set it to the factory settings (approx. 7degree at 1500rpm with disconnected vac.).

How do i know if its pre ignition? Wouldnt pre ignition get worse when i get i leaner mixture?

Edit: Also its worse at cold engine - not sure if this helps recognizing the problem

Edited by JackZwiebel on 19th Mar, 2019.


JackZwiebel

19 Posts
Member #: 11786
Member

I'v been thinking and pre-ignition doesnt particular mean that the ignition is too advanced right? Or should i try retarding the ignition a bit?


Joe C

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12151 Posts
Member #: 565
Carlos Fandango

Burnham-on-Crouch, Essex

Drop gear rattle?

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

https://joe1977.imgbb.com/



JackZwiebel

19 Posts
Member #: 11786
Member

no, dont think its the drop gear. its a too low frequency for drop gear - also a too high for the clutch. Also too strong for the drop gear, it was reall hard rattle that shakes the whole car.

Kinda worried now to damage something with pre ignition.
Its almost gone now since i blocked off the part throttle lean off and put it a bit leaner. It now occours sometimes with cold engine...only a little bit, almost not noticeable.

Not sure if it is good to lean it off even more.

Edited by JackZwiebel on 19th Mar, 2019.


metroturbo

752 Posts
Member #: 989
Post Whore

North Yorkshire

With a correctly timed in distributor and tick over CO set correctly there should be no risk of pre-ignition at tick over. If you had had mapped ignition it might have been a rogue number causing a problem. Have you got a wideband air/fuel ratio meter fitted?

A video might help to identify the noise?


JackZwiebel

19 Posts
Member #: 11786
Member

I will check the ignition again today and see if it still occours. If so i will take a video.
Yes i have a wideband afr meter

Does pre-ignition result from loo lean or too rich mixture?

i cant really tell if making it more lean made it better since i blocked the part throttle lean off and made it leaner in one step. so maybe it was just the part throttle lean of that made it better.


metroturbo

752 Posts
Member #: 989
Post Whore

North Yorkshire

My understanding is that it is caused by running too lean and/or too advanced ignition timing.

I'd try the BDD needle to rule out the needle being the source of it leaning out when driving away. I assume you are confident you have no air leaks on the manifold?


JackZwiebel

19 Posts
Member #: 11786
Member

I had some, it was running better there *happy*
I now have sealed them and pressure tested the whole system, also checked with brake cleaner - no leaks.

I checked the ignition just now and it was about 2 degree off. I put it at 6-7į at 1500rpm and no vac connected.
Adjusted the mixture a bit (a bit richer again) and it sets off perfectly fine now. Also fueling is more constant over the whole band.
Guess it really was the ignition. I would never have thought of pre ignition thanks mate!


Edit:
It runs fine so far, with 12.5-13 AFR in boost and 12 AFR off boost. Only on transition when the turo sets in it leans off shortly, if i accelerate quick. The higher the gear the more it leans off at this point.
What do you think? thicker damper oil? am using 20w50 now.

Edited by JackZwiebel on 20th Mar, 2019.


Turbo Phil

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4336 Posts
Member #: 20
My sister is so fit I won't show anyone her picture

Lake District

If youíre already using 20/50 oil, try a stronger spring. Itís a bit of a balancing act to get right but worth some effort.

Phil.

WWW.TURBO-MINI.COM


JackZwiebel

19 Posts
Member #: 11786
Member

what afr am i looking for at transition to boost? Should it stay at 12.5 or is a bit of lean off ok?

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