290 psi!!!!

[prince_zorro]

In brief, I'm running my car with a set of 11.5 compression pistons, group n cams, 182 manifold...the car is given 170 hp only on the dyne even after map!!!,,,

Checked the Compression for the four cylinders...they give me 290 psi!!!?..

Wat cud be the problem??

Cheers.....

 

[SamP]

Is it detting? Put it in another car and see what numbers it comes out with? Compare with another gauge..?

 

[prince_zorro]

Is it detting? Put it in another car and see what numbers it comes out with? Compare with another gauge..?

Already tried it in two other cars...and the values were fine,,,,

 

[SamP]

Already tried it in two other cars...and the values were fine,,,,

Who was the engine built by?

 

[Cro]

Burning oil at all? Could be a build up of carbon on the the piston... assuming its fitted correctly

 

[prince_zorro]

The car wasn't t idling after the build,lots of knocking and the exhaust gases were a bit rich with fuel...

 

[sideways danny]

thats pretty extreme, I expect you have errors on the gauge. It's not impossibly high compression though as you have basically standard cams

 

[prince_zorro]

The cams are not standards....they are 272/?, that's what I have been told!!!

 

[sprintcup]

I think you may find Group N cams are a standard profile just machined to the limits to guarantee a standard duration to run in the Group N class.

Regards Russ...........

 

[sideways danny]

The cams are not standards....they are 272/?, that's what I have been told!!!

possibly 428s them, still very very mild

I think you may find Group N cams are a standard profile just machined to the limits to guarantee a standard duration to run in the Group N class.

Regards Russ...........

exactly this.

 

[slindborg]

tbh 290 isnt 'that' high...

We had a 1.6 8v gm engine test at 250-260 depending on the gauge throughout its life. It was on a fairly mildish cam too.

 

[sideways danny]

for reference, I would expect a stock engine to make 170-190psi and a high compression fully built engine with something like cat 422s to be around 230psi

 

[Laine_16v]

Slap some diesel in the tank and she'll be purring away at that compression!

 

[sprintcup]

I assume the throttle is open as well, just wondering how you comp check FBW throttles, still this won't cause the above.

Regards Russ........

 

[sideways danny]

I assume the throttle is open as well, just wondering how you comp check FBW throttles, still this won't cause the above.

Regards Russ........

have to remove the plenum on these. I actually started typing the same thing hehe

 

[jezcharger]

for reference, I would expect a stock engine to make 170-190psi and a high compression fully built engine with something like cat 422s to be around 230psi

I had mine tested on sunday and got 150psi across all cylinders, is this cause for concern? The engine is stock and covered about 90k

 

[shiyan]

I'll be removing the inlet to install spark plugs this weekend, is there any point to doing a compression test if there's nothing particularly wrong with the engine?

Just had some misfires recently.

 

[T.Trophy]

I had mine tested on sunday and got 150psi across all cylinders, is this cause for concern? The engine is stock and covered about 90k

Sounds low mate, my low compression engine is 145psi per cylinder

 

[jezcharger]

Sounds low mate, my low compression engine is 145psi per cylinder

Mmm another issue for the list

 

[SamP]

Mmm another issue for the list

Theres massive variation between the testing equipment. As long as all cylinders are roughly the same then theres nothing to worry about. Unless by being all the same theyre all 10psi

 

[drhowser]

I'll be removing the inlet to install spark plugs this weekend, is there any point to doing a compression test if there's nothing particularly wrong with the engine?

Just had some misfires recently.

Are you on the original HT leads?

 

[slindborg]

Sounds low mate, my low compression engine is 145psi per cylinder

I think he meant its 150psi on each cylinder.... Which imho is perfectly fine.

 

[shiyan]

Are you on the original HT leads?

Changing the spark plugs, leads, coilpack, matched inlets, uprated engine mounts.... over the coming 2 weekends.

Just wondering if it's something worth checking while the inlet is off.

 

[sideways danny]

I think he meant its 150psi on each cylinder.... Which imho is perfectly fine.

I would say anything as low as 150psi has deteriorated enough to be down on power

 

[jezcharger]

I would say anything as low as 150psi has deteriorated enough to be down on power

My mate works for Arnold Clark and just had his compression meter calibrated, so should be pretty accurate. It still goes well enough and each cylinder is exactly the same at least so it will have to do

 

[slindborg]

I would say anything as low as 150psi has deteriorated enough to be down on power

A leak down test would be preferable to really get a good idea as compression tests are hugely swayable with temperature of the engine, air temp, oil temp, oil type, starter condition, battery condition etc etc... But you know all this anyway

 

[sideways danny]

indeed a compression test is only really useful if you know what you should be seeing to start with, but done in hot, cold, wet and dry (oiled) conditions can tell you a hell of a lot about where a fault lies