Had my car on the dyno for the 1st time last week when Jan came to Seattle. My initial pull was pretty low given the numbers I’d seen others pull with similar mods:
2003 MCS
Dinan CAI
Miltek Catback
15% pulley
380 injectors

Initial pull HP 163.7 @ 6900
Initial pull TQ 156.2 @ 3936

Jan worked his magic, and the car ran much better, and a nice increase:

Final pull HP 178.2 @ 6635
Final pull TQ 162.7 @ 3853

But still lower than I’d expected. At first I thought I just had a Friday afternoon build, but someone suggested a compression check, so I thought what the heck.
well, I’m starting to get an inkling of why my numbers were so depressing:
#1 - 150psi (180 wet)
#2 - 132psi (150 wet)
#3 - 135psi (190 wet)
#4 - 150psi (didn't bother... )

So, where to go from here? Is it worth getting a leak down test done? The diff in the wet #'s seem to suggest that it's a piston/rings problem.

Anyone know of a shop in the Seattle area?

 

I suggested that. No wonder your number was low.

 

150 psi is actually fairly consistent with what these engines run stock. I wouldn't be overly concerned with the 2 & 3. They're pretty close to 1 and 4. Not sure why 3 ran so much higher than 2 wet... doesn't make any sense.

How many miles do you have on your car?

 

63k on the car. Doesn't seem to burn oil, and certainly no smoke (even when on the dyno).

150psi doesn't worry me, fairly typical from what i've read, but 2 & 3 do. I though the "uh oh" point was if there was more than a 10% variance between cylinders?


Yep, the wet #'s for 3 suprised me. Maybe i'll test agian to double check.

 

Yea, i'd recheck it...

 

maybe clutching at straws here, but....

does that fact that the compression is low adjacent cylinders mean anything? Wondering if it's at all possible that there's head gasket/head leak going on.

 

Its a chance... but i doubt it. I think he just needs a nice set of pistons in there.

 

Custard how often do you retorque the head?

John

 

Never since i've owned the car. I wasn't aware that this was something that needed doing on a regular basis.

 

I will see if I can find a cycle rate for how often.

John

 

I was in a similar position to you a few months ago (33,000 miles on car)

150psi
135psi
150psi
150psi

As you are only suposed to have a difference between cylinders of 7 psi I took it to BMW as my car is still under warranty...... result was they fitted a new engine even though it probabily was just rings needed

My compression now on all cylinders is over 180 psi

 

If it was a head gasket you'd have coolant in the oil.

 

but has he checked for this....hmm i think he should

 

no coolant in the oil as far as i can tell. If memory serves from blowing the headgasket in my 66 Mini 20 years ago, the emulsion is pretty obvious!

I'm pretty sure it's not the gasket - just in denial Well, that and the fact that adjecent cylinders were low seemed suspicous.

 

So, double checked again today - no coolant in the oil. But, oddly, there is oil in the coolant! Quite a reasonable "film" floating on the top.

 

Redid my compression check today at rustyboy155’s suggestion. I’m seeing around 160psi all round . The only thing I can think of is that I didn’t have the compression tester tight enough, or there was some goop or something on the O ring preventing a good seal. Rechecked twice to make sure, and yep, 160 all round.
Aside from me b*llocksing it up in the 1st place, would anything else cause this? It’s mighty hot here in seattle, but I can’t see that affecting things at all.

 

Are you sure you cranked it enough the first time around on cyl 2 and 3? Glad to hear they're all even now! Now you can stop being a worry wart.

Jeremy

 

Sorry if I have missed it in the posts above but you did do the test both times when the engine was hot? Not one done cold and one done hot?

 

Yep, hot both times.

 

I've actually scared myself in the same way - it was the tester. If you don't have a good seal, it will look exactly like yours did the first time.

As an interesting side note, I saw a busted exhaust valve (a chunk was actually missing) on a 2002 JCW the other day. It was pretty close to stock JCW, but he had run regular fuel in it. Low mileage too. The valve blew right through the head into the exhaust though, and it didn't hurt the piston or cylinder a bit. With a new head, the car runs like a champ again. The compression for #3 was zero!

Randy

 

Nice parts replacers ya got there....do they do the same thing when your footing the bill?