Poopy power, poor piston performance?

[douglas vincent]

Ok, for those who didn't know it, I damaged the top of #4 piston and destroyed the ring lands of said piston. I did damage/scratch the cylinder wall, but nothing close to disasterous. I did this by running too much boost and too much nitrous combined with no aftermarket fuel enhancement and no timing management. This was done on a NA 1990 2.2 that had just had new rings and rebuilt heads on it. I was then branded with the word "idiot" on my forehead. I was greedy and impatient.


I replaced the pistons with a brand called "Rock" and the rings with a quality japanese brand (cant remember the name). Absolutely no problems when I finally restarted the motor. Runs and idles like a dream, maybe a weird dream, but a dream none the less.

But....... I have about 225 miles on this engine so far. I am not hammering on the engine at all and have yet to hit 5000+ rpm. But when I do floor it, there is a nice smooth power but it feels like shit compared to my old engine. There is NO punch now. Car can easily go fast, but not accelerate fast. When running up to 80 in 5th, the car doesnt complain in the least, no stuttering just no oomph.

My question is, could I have gotten pistons that are lower compression that OEM stock pistons? So lets say my compression ratio drops from NA compression (which is what 9.5-1 9-1?) to lower, somewhat nearer to turbo 2.2 compression ratio. Would this rob power but still run well?

Thanks.

[vrg3]

It seems possible to me, although it's kind of weird that they'd make pistons that fit but have a low CR... unless they're meant for people doing aftermarket turbos and stuff.

But, yes, lower compression would make less power but still run well. That's what evolutionmovement's got.

It's also plausible that the new rings aren't sealing as well as the ones you had before, right?

Did the pistons look physically different in shape or size?

[douglas vincent]

The new rings I am using now are the same brand as the last time I rebuilt the motor.

The pistons looked different, but mainly because they were made by a different maker, so the head/face was milled slightly differently and said "rock" in them. The side and wrist pin stuff looked very similar. I really should have mic'd em, but alas I did not.

I just took the car out since I wrote the first post, and damn it is a dead power rig now. Bleah. Just nothing there, no bogging or stuttering, just no power.

I wonder if my timing is off. It could be that my cam crank on the 1/3 cylinders is off about 3 notches. I will have to yank off all the timing belt stuff again and reinspect.

Also, is there a way to test and compare compression? ie, would a new NA motor have higher compression test results versus a turbo motor?

[vrg3]

If one of your cam sprockets was off by even one notch, I'd expect it to make the engine run very badly. I could be wrong about that though.

Yes, I do believe NA motors have higher compression test numbers than turbo motors. The problem is that unless you have access to a really nice expensive compression tester, the absolute number indicated on the gauge is't that meaningful.

[evolutionmovement]

What about the knock sensor?

Steve

[professor]

have you seen this site

http://www.theoldone.com/

dude builds stuff like 475hp hondas with 27 psi blowers and 11:1 compression without getting knock. Much information on piston design / compression ratio and stuff. I like the anti-hype, low-buck approach, no bs

[scottzg]

I love the alliteration in the title of this thread.