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Author: Subject: fuel mist coming out of filters???
pickmaster

posted on 5/2/14 at 11:22 AM Reply With Quote
fuel mist coming out of filters???

Ive fitted an ST170 engine on ZZ6R bike carbs with a pipercross 90mm depth dome filter
When under load and full bore fuel mist comes out of the filters
With it being a front engine car and the filters sticking out in the air this fuel mist sprays back on onto my visor
Anyone got any ideas
deeper filters 150mm?
longer intake tubes?
longer trumpets?

Any ideas anyone????

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prawnabie

posted on 5/2/14 at 11:27 AM Reply With Quote
Is it misfiring under load or spitting back throught the carbs?
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pickmaster

posted on 5/2/14 at 11:29 AM Reply With Quote
No misfire
Its pulling like a train

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pickmaster

posted on 5/2/14 at 11:37 AM Reply With Quote
on the road you don't notice as its not often I give it that much as it wheel spins with it only being light (500kgs)
But I have fitted an LSD so now can give it more throttle and be under load, not spinning the wheels

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Peteff

posted on 5/2/14 at 11:45 AM Reply With Quote
Fuel standoff, all to do with pulses and inlet lengths. Can you fit an airbox ? Watch this about 1 minute 20.






yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

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pickmaster

posted on 5/2/14 at 11:54 AM Reply With Quote
That's it
Here is mine with no filters on rolling road about 12 seconds in mist
http://youtu.be/Ppjy8rGHvZk
Any ideas on how long or short to make the intakes
plus 1\4"
plus 1\2"
plus 1"
Where would I start??????

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britishtrident

posted on 5/2/14 at 12:13 PM Reply With Quote
The only real cure is an airbox.





[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]

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Scuzzle

posted on 5/2/14 at 12:20 PM Reply With Quote
Fuel mist is normal on bike carbs at full throttle, never heard of it coming through the filters though, what filters are you using?
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scudderfish

posted on 5/2/14 at 12:30 PM Reply With Quote
quote:
Originally posted by britishtrident
The only real cure is an airbox.


Is that curing it or hiding it? Are you going to end up with a puddle of petrol waiting for the next backfire for fun and chuckles?

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v8kid

posted on 5/2/14 at 12:46 PM Reply With Quote
quote:
Originally posted by scudderfish
quote:
Originally posted by britishtrident
The only real cure is an airbox.


Is that curing it or hiding it? Are you going to end up with a puddle of petrol waiting for the next backfire for fun and chuckles?


I think the idea of the airbox is to reflect the pulses at the resonant frequencies so i guess thats a cure if you get the frequency right and hiding it if you get it wrong

Cheers!

PS can the OP lengthen the inlet tracts? Although it may seem counter intuitive by lowering the resonant frequency the pulse strength is also lowered and the added inertia of the gas may overcome the pulse - Whell something like that !

[Edited on 5-2-14 by v8kid]





You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a chainsaw

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Peteff

posted on 5/2/14 at 12:49 PM Reply With Quote
You get to suck the fuel back in when you let off the throttle instead of losing it to atmosphere





yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

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MikeRJ

posted on 5/2/14 at 12:58 PM Reply With Quote
quote:
Originally posted by scudderfish
quote:
Originally posted by britishtrident
The only real cure is an airbox.


Is that curing it or hiding it? Are you going to end up with a puddle of petrol waiting for the next backfire for fun and chuckles?


What do you think happens in the original plenum?

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pickmaster

posted on 5/2/14 at 01:12 PM Reply With Quote
I don't think an air box is an option
I won't be able to see where I'm going with that in the way

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pickmaster

posted on 5/2/14 at 01:16 PM Reply With Quote
It's a pipercross 90mm deep dome filter
I can't go any shorter on intakes because of the angles between carbs and cylinder head

[Edited on 5/2/14 by pickmaster]

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MikeRJ

posted on 5/2/14 at 04:21 PM Reply With Quote
quote:
Originally posted by pickmaster
I don't think an air box is an option
I won't be able to see where I'm going with that in the way


Then the only way to work around this would be longer trumpets to try and contain the stand-off, but that may require the carbs to be rejetted, and you may sacrifice some top end for more mid range (which is often a good thing).

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jacko

posted on 5/2/14 at 07:22 PM Reply With Quote
engine
engine

Why not i did with the filters out side
Jacko

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pickmaster

posted on 5/2/14 at 08:14 PM Reply With Quote
That's a neat solution
But I'd like to spend a bit more time trying to cure the problem rather than contain it
I'm going to experiment with intake lengths and see how I get on
If not maybe a mesh baffle inside a larger filter
I'll try 3" longer then shorten 1/2" at a time see what happens

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madteg

posted on 5/2/14 at 08:28 PM Reply With Quote
Have you checked the cam timing, just a guess but bet you have adjustable vernier wheels fitted.
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pickmaster

posted on 5/2/14 at 08:38 PM Reply With Quote
Now that's a thought it's on that VVT thingy
I have full advance set at 1500 rpm
So at 4000rpm when it's spraying its on full advance
Maybe too soon?

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madteg

posted on 5/2/14 at 08:54 PM Reply With Quote
Let me know what you find, thanks Kev.
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Canada EH!

posted on 6/2/14 at 12:01 AM Reply With Quote
It was a common problem in the 70's when I raced, friends Volvo 122 was really bad, a longer set of air horns fixed the problem.
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MikeRJ

posted on 6/2/14 at 09:04 AM Reply With Quote
quote:
Originally posted by pickmaster
That's a neat solution
But I'd like to spend a bit more time trying to cure the problem rather than contain it


You can't "cure" it, it's an inevitable part of engine operation. . Containing the stand-off is the only solution, whether it be in longer trumpets or within a plenum or air box.

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pickmaster

posted on 6/2/14 at 09:45 AM Reply With Quote
I've been on the phone to pipercross today and they have said there is a carbon element in the filter to stop this
But I've been using K&N filter oil and they think its worth trying there's first as the two oils are for different materials
Watch this space!!!!

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pickmaster

posted on 9/2/14 at 06:04 PM Reply With Quote
I've cleaned and recoiled filters with pipercross filter oil and been out this afternoon when it was dry
Still the same oil and fuel coming out at 4000 rpm and full throttle
Next time I get half an hour I'm going to extend the inlets an inch
See what happens

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britishtrident

posted on 9/2/14 at 08:14 PM Reply With Quote
quote:
Originally posted by pickmaster
I've cleaned and recoiled filters with pipercross filter oil and been out this afternoon when it was dry
Still the same oil and fuel coming out at 4000 rpm and full throttle
Next time I get half an hour I'm going to extend the inlets an inch
See what happens


As others have aready said you can't stop it from happening only contain it so it gets sucked back in and not blown away in the slipstream
Although the. net flow into a cylinder is inward airflow into a single inlet tract pulses in both directions.
You can't rewrite the laws of physics the length of the inlet tract. has a major affect on power delivery and mixture.

[Edited on 9/2/14 by britishtrident]





[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]

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