Compression and Leak down numbers - need input
#16
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The question is:
Why are the leak #'s on 1-4 basically the same as the two cylinders with higher compression?
You would assume the lower compression cylinders would have a higher leak # ?
Why are the leak #'s on 1-4 basically the same as the two cylinders with higher compression?
You would assume the lower compression cylinders would have a higher leak # ?
#17
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1) Lets say you test a motor and it has 200psi in all cylinders but one that reads 175 psi . By the 10% rule that motor "needs" a repair because of the 175 psi cylinder .
2)The next motor that is checked reads 175 psi on all cylinders and is said to be fine and needing no repair .
3)The 3rd motor reads 157 psi on all but one that reads 175 psi , this motor is said to be needing repair because the one cylinder is more than 10% away from the others .
1) 175 psi = to low compared to the others = repair
2) 175 psi = fine = no repair
3) 175 psi = to high compared to the others = repair
"You test a motor one week , one cylinder at 100 psi and all the others are at 125 and you say the motor needs a rebuild , next week you test and all the cylinders are at 100 psi and the motor is fine and needs no rebuild ? " Again, I might question measuring technique or the compression guage if readings aren't consistant.
If one day a cylinder is fine to run at one psi reading , and then the next day at the very same psi reading it isn't fine to run ...
They make from the factory cylinders that switch on and off . There are motors that are meant to have dead cylinders .
#18
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Oh, jeeze. Perform an Italian Tune Up and then retest.
Seriously- get it hot and then thrash it for an hour- curviest roads you can find, up and down thru the gears, WOT/redline as much as possible.
1. It'll be good for your soul
2. It'll blow out any accumulated gunk*
(*technical term)
Seriously- get it hot and then thrash it for an hour- curviest roads you can find, up and down thru the gears, WOT/redline as much as possible.
1. It'll be good for your soul
2. It'll blow out any accumulated gunk*
(*technical term)
#19
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Oh, jeeze. Perform an Italian Tune Up and then retest.
Seriously- get it hot and then thrash it for an hour- curviest roads you can find, up and down thru the gears, WOT/redline as much as possible.
1. It'll be good for your soul
2. It'll blow out any accumulated gunk*
(*technical term)
Seriously- get it hot and then thrash it for an hour- curviest roads you can find, up and down thru the gears, WOT/redline as much as possible.
1. It'll be good for your soul
2. It'll blow out any accumulated gunk*
(*technical term)
#20
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Well, that may or may not have made a difference. How long is an autocross lap, time-wise. 2 minutes? Vmax?
If you said you'd been to DE....
100 miles highway? Soft duty.
Whatever- your numbers are not anything I'd be concerned about given the age/mileage of the car. I imagine it runs entertaininly strong, and your oil consumption seems very reasonable.
Again, I'd run it unless you were looking for an excuse to get the work done, in which case your numbers are terrible and you need to have it serviced immediately
If you said you'd been to DE....
100 miles highway? Soft duty.
Whatever- your numbers are not anything I'd be concerned about given the age/mileage of the car. I imagine it runs entertaininly strong, and your oil consumption seems very reasonable.
Again, I'd run it unless you were looking for an excuse to get the work done, in which case your numbers are terrible and you need to have it serviced immediately
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#21
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Well, that may or may not have made a difference. How long is an autocross lap, time-wise. 2 minutes? Vmax?
If you said you'd been to DE....
100 miles highway? Soft duty.
Whatever- your numbers are not anything I'd be concerned about given the age/mileage of the car. I imagine it runs entertaininly strong, and your oil consumption seems very reasonable.
Again, I'd run it unless you were looking for an excuse to get the work done, in which case your numbers are terrible and you need to have it serviced immediately![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
If you said you'd been to DE....
100 miles highway? Soft duty.
Whatever- your numbers are not anything I'd be concerned about given the age/mileage of the car. I imagine it runs entertaininly strong, and your oil consumption seems very reasonable.
Again, I'd run it unless you were looking for an excuse to get the work done, in which case your numbers are terrible and you need to have it serviced immediately
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
Thanks again to everyone for their input.
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To me, what is important is the difference from the original compression ratio-
Were all rated at 180 psi or was there a different ratio for the 4 at 160 originally.
If all were at 180 psi as stock - and 4 have lost 20 psi, but the leak down test doesn't show any significant leakage difference from those at 175-180 psi, then were is the issue. Could the 4 @ 160 have been less originally - maybe 170
I would say that if you have the original compression numbers ( which none of us have) that this is what you want to pull your evaluation from - as it will tell you what you have lost - without it it is a shot in the dark to come to any major decision as leak down is not that bad. ( if all were done correctly)
Were all rated at 180 psi or was there a different ratio for the 4 at 160 originally.
If all were at 180 psi as stock - and 4 have lost 20 psi, but the leak down test doesn't show any significant leakage difference from those at 175-180 psi, then were is the issue. Could the 4 @ 160 have been less originally - maybe 170
I would say that if you have the original compression numbers ( which none of us have) that this is what you want to pull your evaluation from - as it will tell you what you have lost - without it it is a shot in the dark to come to any major decision as leak down is not that bad. ( if all were done correctly)
#25
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If you use the criteria of a previous poster where 100 PSI was the so-called number, then 90 PSI was 10% low and 110 PSI was 10% high. Now looking at the OP's #'s we can apply the same factors where 175 PSI is the mid-range, therefore, 160 is only 9%, and 180 isn't even 3%!
Therefore, you are dead-nuts on for variations. DON'T WORRY ABOUT IT!
Even if you took the extremes 180/160 = a whopping 12.5% (judging by the increments of 5 PSI the error in reading the gauge would account for 2.5%)
Therefore, you are dead-nuts on for variations. DON'T WORRY ABOUT IT!
Even if you took the extremes 180/160 = a whopping 12.5% (judging by the increments of 5 PSI the error in reading the gauge would account for 2.5%)
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Unfortunately I could not find it so I went with Techron which also seems to get good reviews.