[aslet]

I looked around but am not sure if my dyno numbers look good. The motor was compression tested and all cylinders were 135psi. My dyno run had a max power of 185HP (6200rpm) and max torque of 171ft/lbs (4800rpm). Do these numbers sound good for a stock motor (I only have the air box mod)? I know the dyno type and weather and other factors can change results a lot. I also know you lose about 15% from the crank. This would suggest you should get 200HP at the rear wheels. So do my numbers sound low?



Thanks



PS- I can't get the image uploaded right now, I'll try to figure out how to upload it later.

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[Cloud9...68]

I would do another compression test with a different gauge - 135 psi is off-the-charts low - it should be at least in the mid-180s. Did you do the test hot or cold? If cold, you may want to first re-do it hot. When I did it cold, I got really goofy readings, but hot, the numbers are quite normal (185 - 190 psi). How many miles are on the engine? Does it run OK? How much oil does it consume? Dyno's seem to be a real can of worms, with tons of variation among machine types, and the numbers seem to be highly dependent on a lot of variables. Flash wrote a nice summary of dyno's and their pitfalls; you should do a search and read through it.

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[flash]

135 compression i s WAAAAY low



do not assume any percentage number for drive trian loss - that is an erronerous amateur mistake - you have about 35 ho loss, regardless of what power you make



that being said, 185hp/171ftlbs at the wheels is normal on a dynojet for an engine with about 80k on it

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[aslet]

A real good local shop did all the testing. I'm not sure what they did for the compression test, but they said it was good numbers. Maybe there setup will give different readings compared to other peoples units?



The car runs fine, so I done think the compressiOn is danger low. It also uses no oil to speak of, but has 126k miles, so it's getting up there.



So I'm guessing it's good and is just normal wear and power loss.



Thanks guys!

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[Cloud9...68]

Yeah, if it doesn't smoke or consume much oil and runs well overall, and given what appear to be pretty normal dyno numbers, I wouldn't worry too much about the compression numbers. They can't be right, because you'd be belching smoke like a semi with a million miles on it, and/or going through a quart of oil a week if they were real; chalk it up to a quirk of either the gauge or the method that was used.



As a point of reference, I'm doing a rebuild now (not because it actually "needs" it, but because I want to track the car a lot more, so I want to upgrade the connecting rods, which means the crank has to come out - very slippery slope...) with 115K miles. I took the head to a very experienced machine shop that specializes primarily in European cars, and the owner told me the head is in excellent condition overall - no warpage, the seats are good, etc. So it appears these engines can go quite a ways before needing a rebuild, although of course the performance will slowly deteriorate as the miles build.

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