ditchlewis
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| posted on 16/1/08 at 02:14 PM |
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ignition & Engine Knocking
Following on from an earlier post about a mysterious starting problem which most people think is the timing, I have had a similar problem and also
have chronic misfire.
The starting problem has been over come by a monster starter motor, but the misfire is a problem that won’t go away.
I’m running a pinto 2.1 with maxiflow 2 head, a FR32 cam, twin dellorto 45 with a modified dizzy and lumination electronic ignition. The engine was
built by Vulcan engineering and was a complete installation, which only needed fettling once run it.
Once when the car was running my brother in-law (a Ferrari mechanic) played with the carbs and the timing to “improve” the running. He did not have an
ignition timing light with him so he did it by ear.
The problem I have been having is that the car misfires’ and back fires a lot, and has even blown one of the Carb Socks to pieces. This only happens
under load and I have to back off or keep the revs above 4K to prevent back fire. The sound is difficult to describe as the helmet and wind noise
obscure the noise a bit.
The definition of pinking I have found is
Knocking (also called pinking or pinging)— occurs when combustion of the air/fuel mixture in the cylinder starts off correctly in response to ignition
by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The resulting shock-wave
reverberates in the combustion chamber, creating the characteristic metallic "pinging" sound, and pressure increases catastrophically. It
can range from hardly noticeable to complete engine destruction.
Detonation can be prevented by
• Increasing the amount of fuel injected/inducted and thus reducing the fuel air mixture
• Retardation of spark plug ignition.
When I increase the fuel mixture the noise/ stutter is reduced. When I have the plugs out they are black which lead me to think the mixture was too
rich but reducing the mixture will cause the stuttering to come back.
Do you think that I have a problem with ignition that is to far advanced?
Ditch
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David Jenkins
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| posted on 16/1/08 at 02:48 PM |
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I have a timing light...
...why don't I come over sometime and check your static timing? (This is the timing at idle, with the vacuum connection to the dizzy removed and
blocked.)
David
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garage19
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| posted on 16/1/08 at 03:11 PM |
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Assuming your ign is correct a missfire can be caused by both a lean or a rich situation.
With out a wideband to tell you which you are probably on a road to no where.
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ditchlewis
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| posted on 16/1/08 at 03:33 PM |
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B###er
I though it might be easy, i suppose that there is no putting off a tune up then i will have to get the wife to work some more hours next
month  "WHAT SO YOU CAN SPEND MONEY ON THAT THING. YOU PROMISED ME NO MORE!!!!!!"
i will turn up the carbs again just a little bet more 1/2 turn should do it, if it improves as it did last time it might prove something.
just a matter of elimination
ditch
[Edited on 16/1/08 by ditchlewis]
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cng1
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| posted on 16/1/08 at 03:48 PM |
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Carbs will spit back for all sorts of reasons and a hairy cam only exacerbates their natural desire to spit. Timing might be it but it could just as
well be a rich or a lean condition. Since you're diddling around with the fuelling I wouldn't rely on the colour of the spark plugs too
much as they're not a great indicator.
First off get your timing set up right, if necessary just nudge it back a couple of degrees to be safe and see if that improves matters. Next get the
carbs balanced, I find it as easy to do with a length of hose as with the proper tool but I'll generally use whichever is closest 
With your timing set up on the conservative side and your carbs balanced you now have a great baseline to tune from. Get yourself a wideband
(personal plug here for the techedge units which you can get from www.trigger-wheels.com) or hire from Bill Shurvinton. With the wideband connected
up take the car out and drive it up in say 3rd or 4th gear from the lowest revs that it will pull at up to the redline and review the results. The
wideband will tell you exactly how rich or lean it is at any given point in the rev range, armed with which you can make an educated decision about
what you need to do to the carbs.
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BenB
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| posted on 16/1/08 at 03:53 PM |
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You could do a rough and ready tune-up with a colortune and a timing light. I know some people aren't too keen on colortunes but David Vizzard
use to recommend them and if it's good enough for him...
At least that will get close on the mixture. Then you can swing the dizzy to get the timing right.
£15 for a colortune, about the same for a timing light.
Job's a good 'un.
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Macbeast
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| posted on 16/1/08 at 03:54 PM |
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I don't think you han hope to set the ignition timing correctly "by ear". The correct setting does not even correspond to tweaking
timing for maximum revs.
Also, you cannot compensate for incorrect timing by adjusting the mixture - that will give you two faults in place of one.
From what I've seen on other posts setting the ignition timimg on a Pinto can be quite tricky. You really need as a minimum a timing light, the
book, and someone who known what he's doing (I don't think Ferraris use the Pinto )
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cng1
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| posted on 16/1/08 at 04:02 PM |
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Yep, colourtunes. Bought one some years ago, used it a couple of times and yes it will just about get you in the ballpark but I can do that by
looking for the clouds of black smoke out of the exhaust
Vizzard rated them when they were the state of the art for the home user, back in the days before digital watches! Times have moved on substantially
but unfortuantely most of his books haven't been updated to reflect that. I'm positive that if writing his books today he'd not be
recommending colourtunes for anything other than historical curiosities and a wideband would be his diagnostic tool of choice.
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ditchlewis
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| posted on 16/1/08 at 04:16 PM |
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I've got a colour tune and have used it a couple of times. (though not since i b###ered it up last time)
the last time i set it up with a colour tune was just before my sva retest. i went out out a 5.30am and the car would not start, so i wound the carbs
back to the default setting of 2.5 turns from closed and still nothing panicing now as i had to be on the road at 6am i remembered that
i had not plugged in the card into the imobiliser
well it started 1st time but ran like S~~t.
i found it hard to use as i'm colour blind and cant tell the difference between bunsen blue and the other blue discribe in the
instructions.
the wife reminded me last night that one of her friend's husbands runs a garage and he is very into those sierre based hotrods and used to race
at vauhall stadium in ipswich. he once tried to sell me a race pinto that he has lying around.
i will give him a call and ask if he has the right equipment
ditch
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BenB
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| posted on 16/1/08 at 04:59 PM |
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I did say "used to" recommend them
(actually I didn't, I put "use to".... )
Anyway, short of ponying up for a wideband, or finding someone with a emissions tester......
Got me through SVA #2 after failing on emissions at #1... Didn't even need to tweek the mixture during test #2.....
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ditchlewis
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| posted on 16/1/08 at 08:36 PM |
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just been out in the beast again. gave it a half turn on the carbs and it is running a bit better with the occasional pop.
i've given it another half turn and i will take it out another day.
did note that the lights were very dim and i could barely able to see.
ditch
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David Jenkins
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| posted on 17/1/08 at 03:31 PM |
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This WAV file gives an idea of the noise that knocking makes, recorded off a sensor bolted to the block. The knock is the 'rasberry' at
the very end of the recording.
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Macbeast
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| posted on 17/1/08 at 05:31 PM |
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I thought Jane Birkin and Serge Ginsbourg did it better
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David Jenkins
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| posted on 17/1/08 at 07:10 PM |
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rusty nuts
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| posted on 17/1/08 at 07:50 PM |
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quote:
Originally posted by Macbeast
I thought Jane Birkin and Serge Ginsbourg did it better
Showing your age a bit!
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Macbeast
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| posted on 17/1/08 at 08:19 PM |
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They say age is just a number.
It's true - practically everything has gone numb.
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