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Running rich
matty78 - 5/2/12 at 09:31 PM

I think I know the answer to this already but I thought I'd check it out to be sure anyway.

I have a Sylva striker mk2 with a 2.1 16v silvertop zetec running on webber 45's.

The engine starts fine, runs fine through the rev range, no splutter up or down the revs but does smell extremely rich on idle.

The only thing I have changed recently is the exhaust system, before I had a 4 to 1 branch manifold and normal exhaust can.

I recently bought a manifold and 6in can from RAW themselves and since fitting this has it run extremely rich, so much so I'd be scared on lighting a match next to the car.

Could it be that the flow in the system has effected the fueling or would it be something else ?

mark chandler - 5/2/12 at 09:39 PM

Have you tightened up the inlet manifold nuts? these should float on the rubbers if you have nipped them up this could be the issue.

You need to use thackery washers and tighten until the washer is compressed within itself, not the carb tight to the manifold.

A new exhaust would affect things but I doubt it would alter idle settings, at low engine speeds it has little effect but through the rev range it would make a change.

matty78 - 5/2/12 at 09:48 PM

quote:
Originally posted by mark chandler
Have you tightened up the inlet manifold nuts? these should float on the rubbers if you have nipped them up this could be the issue.

You need to use thackery washers and tighten until the washer is compressed within itself, not the carb tight to the manifold.

A new exhaust would affect things but I doubt it would alter idle settings, at low engine speeds it has little effect but through the rev range it would make a change.


Thanks for the reply.

The inlet manifold itself to the engine is tight but the carb's to the inlet manifold are loose'ish if you know what I mean, basically I can grab the carb's and wiggle them slightly.

mark chandler - 5/2/12 at 10:49 PM

Not that then, how about checking the float heights, it may be one carb causing the issue?

If you take the filters off and leave it idling in bad cases you see petrol dribbling back out the trumpets.

Regards Mark

will121 - 6/2/12 at 07:23 AM

It could be something to do with new exhaust manifold has had an effect on pulses in the inlet especially if running large overlap cams, when you can get a fuel mist outside the carbs, I can't explain it but heard of it before, hopefully someone can explain more

Oddified - 6/2/12 at 08:42 AM

The wilder the cams fitted in the engine (mainly due to the amount of overlap) the more sensitive the engine becomes to changes on the intake or exhaust.

The best way to know is a wide band lambda if you have one or can borrow one.

Ian.

Xtreme Kermit - 6/2/12 at 07:26 PM

quote:
Originally posted by will121
It could be something to do with new exhaust manifold has had an effect on pulses in the inlet especially if running large overlap cams, when you can get a fuel mist outside the carbs, I can't explain it but heard of it before, hopefully someone can explain more


Not got an explanation for you but I know a couple of key words. The mist outside the carbs is called Stand-off, and it's something to do with standing waves at certain revs.

matty78 - 18/2/12 at 12:34 PM

Well after some thinking, i've decided on a mapping session.

Going to aim for the end of march.

Looking at getting it done at mek motorsport if i can get hold of Dave.

Anyone know anybody else within a 50mile radius of the severn bridge who is any good just incase?