triscadek

On my kids Accord the compression is about 120 psi, just "how" low is that? How low do you get before starting to see some problems?

Bhj0887

If it's 120 psi in all the cylinders or with minimal difference between them. Than there shouldn't be any problems. If each cylinder has a different compression or even one with a difference of more than 10 psi, then you'll start to see problems (missing, loss in power). I'm not familiar with the accord so i don't know what the compression should be at.

If it's low then it may be time for some new rings and a honing.

brad-cam

My 951 has 135 psi in all cylinders. I was thinking that was kinda low too, but since it the same in every cylinder, I'm feeling ok about it.

Zero10

Your 951 is a turbo, so the CR is much lower than on the accord.

You should be seeing 150-220psi, depending on the compression ratio. In that range is good for a normally aspriated engine. Are you testing it with all the plugs removed? I found that makes about a 20-30psi difference (at least on my car it did).

120 sounds pretty low, what's the mileage, what year is it? If it's from the 80's, I believe the compression ratio was about 9.8:1, if it's from the 90's, I think they pushed it over 10, but I could be wrong.
As long as they are consistant, I wouldn't worry, unless of course, it is a new car, in which case I would be very worried. But if it's getting into it's old age, then that isn't too unreasonable. Could try a thicker oil, helped bring my numbers up.

Mike C.

The Honda engines will continue to run with even lower compression. I helped a friend who's Accord had 200K on it, did a compression check and got around 100 psi in 3 cylinders and zero in the 4th! It was still driveable (it did consume some oil though)...

Zero10

Yeah, engines will still run with low compression, but expect a power and mileage loss.
Just for sh*t's and giggles, here's the numbers from my 85 subaru GL, with 340,000km's on it.
150, 90, 120, 25

Those are all close enough, eh? =)
Never burned any oil, still pulls pretty good, but you should hear that sucker knock! the warm oil pressure is 0, even with thick oil, but if you rev it to 2000 or so, it will hit 2 kg/cm^2 (stupid metric system), and eventually work it's way to 3 near it's new redline (vibrationally limited to around 5000 RPM).
Even free revving (not in gear) it won't top 4800-5000RPM, lol.
But, it was still driveable for well over a year.

If it's your kid's car, it's fine, it will just help him not get speeding tickets.

triscadek

Well the deal on this was, about 2 1/2 yrsago the car blew a radiator tank and verheated so fast that the gauge didn't go up. After I put in a new radiator, the top rad. hose expanded to about % its normal size. After some diagnosis I decided blown head gasket is pushing compression or exhaust into the cooling system, too much trouble for an old car and bought my S.

Fast forward to March 04, I gave my son the car and his mother said she would have engineput in for him.

Well knowing kids he drove it around his small town and kept getting out further and further and now he has driven in to see me twice (65 miles one way) and the hose isn't over psi or expanding now, I've been told that the comp is 120, but the power is way down and fuel mpg is about 14 and stopped over heating.

So the car has run over 1000miles with only these problems but has a lot of blow by.

I know cars can't heal themselves but this is weird, ideas anyone?

Zero10

Sounds like a warped head or toasted headgasket.
A leakdown test would tell you for sure.

Chris_924s

It needs a NOS sticker. It'll fix everything Triscadek.