Cylinder pressures

[350matt]

Having just tested my 4.2 AJP V8 for compression pressure I'm getting 16 Bar on all cylinders with about 0.1Bar variation. Is this any good, too high /too low?

Also what spark plugs do people run
I've got NGK BKR5EKU's in mine which naturally don't appear at halfords.... is there an alternative?

Matt

[GreenV8S]

Sounds bl**dy high to me, but consistency is a very good sign.

[Mr.Cerbera]

Bloody Hell ! I thought it was supposed to be 11 Bar

[headcase]

Youve not got one of them faster blue ones have you?

[350matt]

Well theres the thing while it is blue I reckon its not quite the full shilling as anotehr Cerby owner has driven it (admittedly he has a very sorted 4.5) and seemed to think it wasn't pulling quite like it should.

Also I've got one of those little 'g' meter things which works out rear wheel horsepower ( uncorrected of course) and while its no good for absolute figures it used to tally pretty well with the wedge dyno runs and thats showing 260Bhp at the wheels ( mind you I did have the aircon on) and I reckon it should be showing about 280/ 290.

Possibly the cam timing is a bit out? and so boosting the compression a bit

also a 4.5 won't read as high due to the bigger bore

Matt

PS anybody know about the plugs then?

[trackcar]

for plugs i use the champion rc9bmc, hate the NGKs in the cerbies, don't seem to run hot enough to self clean causing all sorts of misfire problems. if you x-ref the NGK part number i think it's for some kind of 1980s vauxhall astra or something.
No idea about the cylinder pressures, my compression tester isn't accurate, i just use it for comparison tests. a cylinder leakage test is what you need and i use a local tuning firm who have one, they tell me if it's ok or not

[350matt]

Cheers Jools

You happen to have a figure for cam timing would you, apart from the follower drop method

Ta Matt

[ridds]

Sounds ok. Very accurate if you can measure to 1.45 PSI.

Was the engine warm when you did it? Even-ness of pressure is more important than absolute pressure as this can vary with cam timing, combustion chamber temp etc.

[trackcar]

350matt said:

Cheers Jools

You happen to have a figure for cam timing would you, apart from the follower drop method

Ta Matt

I set equal lift on overlap at TDC, i've seen less top end power using the 1.5mm method

[Julian64]

trackcar said:

350matt said:

Cheers Jools

You happen to have a figure for cam timing would you, apart from the follower drop method

Ta Matt

I set equal lift on overlap at TDC, i've seen less top end power using the 1.5mm method

Bloody hell, I just set mine and put the cover back on . Still I guess its good practice

[simonsparrow]

Julian64 said:

trackcar said:

350matt said:

Cheers Jools

You happen to have a figure for cam timing would you, apart from the follower drop method

Ta Matt

I set equal lift on overlap at TDC, i've seen less top end power using the 1.5mm method

Bloody hell, I just set mine and put the cover back on . Still I guess its good practice

Good to know for the future I guess, equal lift must be easier to set than 1.5mm difference.