what is considered good results for a 92 twin turbo? I was hoping to tweek my boost slightly up to around 10psi, car has a decat stainless sytem, mines ecu and induction kit, i should hopefully have my results later today... Cheers dan

Not going to have my car back until tomorrow now, any ideas though guys?

do a search pretty sure this has been covered previously what you looking for mostly is a uniform pressure, between each cylnder.

The closer to 180 psi the better, needs to be done with all plugs out and a well charged battery.

 

Jeff TT

thanks guys, how come they all have to be out? Ive tried doing a search but couldnt find any actual numbers

with all the plugs out and the throtal open the engine will spin over with no effort, its quicker and wont kill your battery.

the highest is 140psi and the lowest is 125 psi, is this about right? I spoke to the tuner he said for a reliable boost increase i should have it rebuilt with forged pistons as they are cheaper to buy than stock ones... What do you think??

the highest is 140psi and the lowest is 125 psi, is this about right? I spoke to the tuner he said for a reliable boost increase i should have it rebuilt with forged pistons as they are cheaper to buy than stock ones... What do you think??

 

Given the age and mileage of most original zed engines thats not too bad, trouble with compression testing it has so many variables that can effect the result such a battery charge level, operators gauge accuracy, throttle opening when done etc. it should be viewed as part of the engine information not all of it. Seen many zeds in good running order that boost well and return acceptable mpg with not especially good readings.

 

Rebuilding with forged pistons is nice rather than a requirement, when its all apart the difference in price is just the parts cost as the labour is the same.

 

Jeff TT

The closer to 180 psi the better, needs to be done with all plugs out and a well charged battery.

 

Jeff TT

 

That's nice to hear.

 

My NA was tested soon after I bought it and I got between 200 and 210 in all of the cylinders...the tester said he had never seen such a clean engine and that it was ripe for tuning.

 

As for the process, you're absolutely correct. He had to remove so many bits i was worried he might forget to put something back!

Providing the test is performed correctly - (Engine warm, all plugs removed, throttle open, healthy battery, dry test), then in my opinion and experience :

 

140-160 psi is a realistic figure for a healthy, but used TT engine. 174 psi max.

150-170 psi is a realistic figure for a healthy, but used NA engine. 186 psi max.

 

Anything less than 130 for the TT or 140 for the NA would interest me to investigate further. Also, Nissan reccomend a maximum difference of no more than 14psi (1bar) between cylinders.

Edited April 7, 201114 yr by Yowser

That's nice to hear.

 

My NA was tested soon after I bought it and I got between 200 and 210 in all of the cylinders...the tester said he had never seen such a clean engine and that it was ripe for tuning.

 

As for the process, you're absolutely correct. He had to remove so many bits i was worried he might forget to put something back!

 

The NA has a higher compression ratio than the TT. But even so, Its max limit should be 186. Being over this is not an indication of a healthy engine unfortunatly.

 

If high in only 'some' cylinders it typically indicates high carbon build up. But since all your results were high, its most likely that either the tester was at fault or that your timing is out by a tooth or more.

 

I would suggest having your timing checked.

Edited April 7, 201114 yr by Yowser

what are the negative effects to a bad/old battery in general?

what are the negative effects to a bad/old battery in general?

 

It wont start when its cold? LOL

The NA has a higher compression ratio than the TT. But even so, Its max limit should be 186. Being over this is not an indication of a healthy engine unfortunatly.

 

If high in only 'some' cylinders it typically indicates high carbon build up. But since all your results were high, its most likely that either the tester was at fault or that your timing is out by a tooth or more.

 

I would suggest having your timing checked.

 

I can see timing being out lowering compression, but how would it increase it without the engine running :confused1:

valves might be partially open....

oops, you said increasing it, scrap that then...

I can see timing being out lowering compression, but how would it increase it without the engine running :confused1:

 

Was thinking the same matey..... :blink:

 

Alz.

could it be that the cam durations would be wrong for example the exhuast side would stay closed too long., allowing too much air into the cyldnder then the pressure would build up beyond the norm

jeff, do you think increasing my boost would do the same as last time? Or do you think my last engine may have been just as strong as this one? Admittadly i did try for 15psi last time and wouldnt go that high this time, or is it impossible to say really?

could it be that the cam durations would be wrong for example the exhuast side would stay closed too long., allowing too much air into the cyldnder then the pressure would build up beyond the norm

 

If the engine was running, yes - it's forced induction - but when not running you're simply measuring the peak pressure difference between atmospheric and TDC... unless I'm missing something?

I can see timing being out lowering compression, but how would it increase it without the engine running :confused1:

 

Intake and exhast valves out of correct sync, as you crank it over to perform a compression test more air is entering than exiting.....more pressure.

Intake and exhast valves out of correct sync, as you crank it over to perform a compression test more air is entering than exiting.....more pressure.

 

But the only air entering is what is drawn in by the vacuum effect of the piston dropping, so any difference would surely be negligible? I'm not trying to be argumentative btw... just can;t get my head round the idea!

 

Rich