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Discussion Starter #1
hi

I have head that cylinder 6 runs leaner than the other cylinders?, is this true?

i heard that when mapping some tuners input more fuel into cyl 6 than the others...

is this due to heat?, due to cylinder 6 getting more air from the inlet manifold? (unequal distrubtion) or is it due to cylinder 6 actually being larger than the others?

regards, brian
 

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Yes, No 6 runs lean, it gets more air due to ram charging cos of the manifold shape.

I always run a touch more fuel in 5 & 6 just to be on the safe site.

Also, I reckon the waters probably quite warm by the time it gets that far down the block, so cooling a tiny issue too.

Cyl 6 is the same size as all the others.
 

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Discussion Starter #5
yes i have

i have not finished but this virgin unskimmed head has a 11ml difference from cylinder one to cylinder 6 (cyl 2,3,4,5 are as yet unchecked)

i thought the reason for the extra fuel goin g to cyl 6 was for the same reasons you think but now im not sure......

does the stock map have extra fuel going to cyl 6?

maybe its just this head that has this issue but its not bent and it hasnt got det on it.....


has anyone else measured the head volume so i can discount my findings and my thoughts that it has actually nothing to do with the inlet manifiold at all?
 

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Very interesting find.

I can't imagen for one moment its supposed to be like that.

It could be that the valve seats are sunk further into chamber?
 

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Discussion Starter #8
R32 Combat said:
Very interesting find.

I can't imagen for one moment its supposed to be like that.

It could be that the valve seats are sunk further into chamber?

i dont think so..., i think (IMHO) its actually made like that but i hope im wrong on this one (dont worry i normally am lol)

i just wondered if someone has been here before and checked them with equal results so i can discount my findings

ill be doing a full test this week sometime and ill load up the exact values of each cylinder
 

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the RB isn't blueprinted or even finished to that high a level so it is entirely conceivable that you have mismatched volumes. if you are handy with a grinder that can easily be fixed.
there was thread on here a while ago about how much difference porting made to the RB, maybe cylinder matching will also yield good results.

/Steve
 

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Discussion Starter #11
i understand what you are saying but 11ml? out of each cylinder?

its just too much!

i removed a load of matrerial from the exhaust ports but even this wouldnt meet half of what i need


the way to go would be to skim the head so that no6 would become equal with no1 but this would be some serious skim and i guess would be on the limit of the head which would then require a thicker gasket..

i dont think there is a right way to...right this issue without causing problems elsewhere
 

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if this is a production problem it is little surprise that RB's eat their 6th cylinder then, imagine how much extra air it gets with the ram air effects of the plenum added to 20% more volume anyway, that would mean to keep things equal you would need to get a 530 cc injector in there just to keep the air fuel ratios the same:eek: *(assuming 440's being used in the other 5)

/Steve
 

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Discussion Starter #14
it was a nice theory but it was actually caused by a persistant leaky thread on no:6 plug

lol, oh well it would have made a great april fools if i posted this next week lol
 

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Thanks!

I'll be interested to hear if you change those values when you get your 6 channel EGT installed.

I understand there are a bunch of variables that go into exhaust temp, but it's nice to have a bit of a benchmark!

Cheers,
Dan
 
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