died on the dyno. your veiws please

[329jay]

took my 2.9 m20 e30 to the dyno for mapping. strong engine. rebuilt about 2000miles. good compression tested on the day of the dyno. new oil and filters. he did the fuel mapping ok then went on to play with the timing
on the last run as the revs climbed it stuttered, like a big pause and carried on reving.

it now has a death rattle from the bottom end and the compression is lower. one has gone down 40psi.

injectors were checked and they are fine. plug leads were crap and he suggested they may have caused the cut out.

did the dyno opperator kill the engine?

[LJ851]

It depends on what failed. Way too much timing causing mega detonation is about all he could do to hurt the engine.Or overheat it. I have dyno tuned hundreds of motorcycles and only a couple have failed on the dyno, all non related to tuning. Disassembly will show the failure and you can go from there.


edit: A competent dyno operator will not hurt your ride, is this tuner known as competent?

[nando]

broken rocker? floated valve?

it would have had to be a lot of timing for a big pre-detonation event. M20s are generally knock insensitive, unless they're boosted to hell and back.

[329jay]

it was a hot day and he was doing a lot of runs. i did wonder if he had over heated it. i never saw the temp gauge but i do have one of those temp stickers on the back of the head. ill have to get a mirror in behind the head to see what temp it went to. the rockers are good. what should it be looking for on strip down?

[nando]

try a leakdown?

[329jay]

the operator was recomended and had done e30 m20's before. i havent done a leakdown. i just chucked it in the garage and tried to forget about it

[LJ851]

Forgot say i'm sorry for your loss, that sucks. Start with easy stuff like nando said, leakdown and pull the valve cover to look for damage. Drain the oil and look for chunks and or brass flecks. (when you feel like going back out to the garage of course)

[329jay]

thanks dude. ill prob go and have a look this weekend. what will the brass fleck indicate?

[LJ851]

what will the brass fleck indicate?

A rod bearing that is gone. Your oil will look like black metallic paint with the metallic being brass/gold color.

[AndrewBird]

Sounds like a bent valve to me. Not sure what would have caused it, assuming all your clearances were good to begin with. Rod/main bearings failing wouldn't cause low compression. Could also be a blown head gasket.

[LJ851]

Sounds like a bent valve to me. Not sure what would have caused it, assuming all your clearances were good to begin with. Rod/main bearings failing wouldn't cause low compression

You obviously haven't been around too many engines. Rod bearings fail, pistons start stroking 1 or 2 mm more than normal, piston hits head, compresses ring land, and massive blowby/leakdown occurs.

[329jay]

i got this from someone....
it sounds to me like your tuner could have advanced your timing forwards in an effort to find MBT (mean best torque). Problem is, being a high CR (even 10:1 is high CR by modern unleaded standards) your engine probably started to detonate long before MBT, resulting in extremely high peak combustion temperatures and pressures, to the point where you quite possibly now have a broken ring and/or ring-land on one or more of your pistons. He may have even thought it was safe to advance the timing because he saw the power falling, but in reality it was dropping because he was pushing your timing into dangerous territory, not because he was still well in advance of MBT. Usually if you hear full blow detonation its too late. Detonation starts long before we can actually hear it,

[329jay]

i just re read my first post. i didnt mention that while he was doing the timing the power was going down. he kept stopping, getting out the car and looking at the power graphs on the screen. he did look a bit puzzled.

[dkbmxer002]

there is a 99.9 percent chance it wasn't your tuners fault. hanging out at shops enough i have seen way too many people try to blame a tuner for an issue their car already had when their car was put on a dyno.



not sayng you are of course. but i'd bet money it was an issue that isn't the tuners fault.

[psyber_0ptix]

there is a 99.9 percent chance it wasn't your tuners fault. hanging out at shops enough i have seen way too many people try to blame a tuner for an issue their car already had when their car was put on a dyno.



not sayng you are of course. but i'd bet money it was an issue that isn't the tuners fault.

tuners work with what they have, and when starting from scratch on a non-standard motor, it can be a bit tricky to get right. As stated above, if there was a problem to begin with, tuning it might further exploit weaknesses in a motor until failure.

...but how many runs was he pulling? and did you ask him any questions during the tuning process? (as to why he looked puzzled) That in of itself would raise alarms for me. I'd be the curious bystander, while trusting the tuner to do what he does, I'd want to be kept in the loop at all times especially regarding a labor project of love/hate.