dima88

iTrader: (5)

I was at 10psi when the vacuum/boost line that goes to the (begi)fmu came off and the engine went lean. the car runs but not on all cylinders and oil is being pumped out the pcv hole in the valve cover.

The rings are gone in one cylinder?

hustler

iTrader: (6)

yes. If its puking oil then its probably over for the motor.

dima88

iTrader: (5)

yeh thats what i thought...
Should i get another stock bottom end or reuse my old pauter rods from my other engine and get some new JE pistons because my old ones have a ton of detonation marks on top? going to make less then 250whp

Braineack

iTrader: (62)

and sell the FMU and get real managment so it doesnt happen again. how does a vacuum line fall off?

m2cupcar

iTrader: (5)

stock bottom end + engine management ftw

dima88

iTrader: (5)

Its a vacuum/boost line to the FMU that came off and my fuel pressure went from 70psi to 43psi and i didn't notice. I got a parallel MS but never got around to installing it, i will probably go with a stock block again.
Thanks

Turbobarber

iTrader: (2)

Ton of detonation marks? How much detonation could you have sustained and still have a running motor?

My understanding was a mere few seconds of detonation was the very end of the motor itself...

Any pics of those rambo pistons? I feel like I've been getting a little det myself, just can't hear it :(

I'm also getting alot of blowby from my pcv... No oil coming out, but lots of air flow coming out of there at idle. Probably wouldn't hurt to do a compression check, but I maintain about 20 inches of vac at idle(900-1k rpms)

dima88

iTrader: (5)

I still didn't take apart the engine that is pimping oil out the PCV hole, the pistons with the detonation(there are a bunch of small craters on top on one side of all the pistons) came out of my old built engine that also failed because the oil ring on #3 cylinder came off.

I was at 24/25 in at idle before this happened.

Turbobarber

iTrader: (2)

well then... I probably could use a rebuild eh?

I believe before I went turbo I was around 22 inches.

That was about 3 years ago, so for all of my mishaps I guess I'm doing okay on a 73k motor..

I'd love to rebuild now, but just not possible.

Craig N

Quite a bit, I believe, depending on the severity of the detonation. If it leads to pre-ignition, or is severe and happens early in the combustion sequence, then that's when you vent your pistons, or remove your ring lands.

Braineack

iTrader: (62)

boring...

Craig N

Like 'boring' a hole in the piston? (sorry, bad joke...)

Well, he asked; I answered.

Braineack

iTrader: (62)

no, just boring lack of knowledge.

pre-ignition is just when the spark plugs get too hot and cause an explosion event before the desired time.

detonation doesn't lead to it, it however, can lead to detonation.

Craig N

This seems to be a well mis-understood area, so I'll post what I understand to be true.

This statement is true, although it doesn't have to be the spark plug that lights off the mixture too early.

Overheated exhaust valves or sharp edges in the combustion chamber (unradiused valve reliefs, etc) can cause pre-ignition once they become hot spots.

You're right, pre-ignition can lead to a detonation like event. However, there is an important difference.

In a standard detonation event, the two (or more) colliding pressure wave fronts are created by the spark plug firing, and the pressure rise due to the expanding wave front autoigniting the remainder of the mixture, respectively. However, this mode of detonation will always occur after the spark plug fires.

In a pre-ignition event, the flame front can be lit off by a hot spot before the spark plug has fired. This can lead to the cylinder achieving max pressure before the piston has reached TDC. Another piston will be on its power stroke, and (along with the engine's rotational inertia) will force the piston from the pre-ignition cylinder up against the high pressure, usually resulting in catastrophic damage. There will probably be a colliding wave front (detonation) in this situation due to the massive pressure rise, but if the pre-ignition occurs too soon before the spark is planned, it's all over anyway.

Detonation can lead to pre-ignition, in that repeated occurrences will break down the boundary layer of gas around the spark plug, and other edges, and can then allow these spots to heat up to a pre-ignition temperature.


This is the way I understand it. Feel free to disagree, but please post your reasoning if you'd like to discuss this more. I'm always eager to learn.

Braineack

iTrader: (62)

boring.

Joe Perez

iTrader: (8)

I like this Craig guy. Argumentative, sadistically ---- about the very esoteric, uses complicated words and phrases to describe simple phenomenon... Reminds me of me.

Craig N

Ha! I actually did laugh out loud when I read that. I can't argue with such a succinct rebuttal!

I slept in this morning... makes me a bit wordy My apologies.

chicksdigmiatas

iTrader: (11)

I used methane injection by farting into my intake. It caused detonation, then pre ignition so bad that my engine spun backwards and opened a worm hole. I am from august 21, 2010.

Craig N

Hardly worth the effort for 19 days worth of travel. Maybe you should make some bovine friends to up the ante?

dima88

iTrader: (5)

Found the problem