Engine knock. What is it?

[danursin]

I recently bought a 95 Tsi talon. somebody told me i might have a blown connecting rod. its definitely a bad knock. no smoke or oil shooting out. heres the video

YouTube - 95 Eagle Talon Tsi

 

[joe sobo]

uh, engine knock is a knock in the engine , no , but seriously, that is most likely a rod bearing failure. but by keep running it , it is just tearing up the crank too, and taking the crank out of its tolerances. so instead of poss. being able to get it cut, you'll have to replace it

 

[boostedjay32]

im pretty sure he meant what is going on inside the engine that makes it knock

 

[Rob10_99]

Rod knock vs Engine knock-

Rod knock= something physically wrong with your engine rotating assembly, IE spun rod bearing(Bad) or too much clearance in your rod bearing to crank journals. Usually a spun bearing.
Engine knock= ECU tells your spark plug to fire too early, too much carbon(ie burnt oil) buildup, cheap gas, too much boost for your timing map(ie spark timing issue again). Overheated engine/head.
Boosting in the middle of Canada is very different than boosting in Mexico, tune accordingly.

Yes, stop running your engine before its a paperweight, take it apart now.
"Rod knock" is audible just like that. "engine knock" is only audible under load/high load.
Formula1 engineering has come up with internal engine pressure sensors, these sensors are so precise that they can get into 1k bar plus. They know the ragged edge of tuning(something I've always wanted to get my hands on!) via special adapters on the spark plugs. The knock they see is knock before its audible or even thought of. Something of a precurser to knock. Maby I'll dig around and see what I can find.

 

[boostedjay32]

Rod knock vs Engine knock-

Rod knock= something physically wrong with your engine rotating assembly, IE spun rod bearing(Bad) or too much clearance in your rod bearing to crank journals. Usually a spun bearing.


Engine knock= ECU tells your spark plug to fire too early, too much carbon(ie burnt oil) buildup, cheap gas, too much boost for your timing map(ie spark timing issue again). Overheated engine/head.

Boosting in the middle of Canada is very different than boosting in Mexico, tune accordingly.

I love learning something new!!
Thanks

 

[joe sobo]

rob, thank you for the wonderful explanation on the subject

 

[Rob10_99]

thanks, Most people REALLY don't realize the difference between a Canada and Mexico tune(copywrite)(no not really, just getting my point across)

 

[danursin]

okay so its a rod knock? Should i even bother fixing it? or should i just swap the motor out? I can get a forged 6 bolt installed for about 2200 where i am.

 

[slinarez25]

Just buy a stroker kit for $1400, and you'll be good to go. Plus now your car would be a 2.3l with better low end torque and your turbo will spool faster. Just an idea!

 

[danursin]

if i were to buy a stroker kit is is something id have to have done by a speed shop? or is it a do it yourself kit for backyard mechanic type of deal?

 

[slinarez25]

Well the kit consists of a new crank, new rods and pistons, and all new bearings. So you definitely could do it in your backyard as long as you know what you're doing of course. I dont know how mechanically inclined you are but if you think you can do it go for it.

If you didnt go the stroker route you would still need (depending how bad the spun bearing is) a new crank, rods, and bearings. Which would be around $1000-1200 anyways, so i figure you might as well get a whole package of everything you need and get a pretty decent upgrade in the process for just a little bit more money. Plus most kits come with all forged internals, which is always a plus.

 

[danursin]

well i have great mechanic friends that will charge little to nothing.. plus its a good learning experience. if i go stroker would i have to bore as well?

 

[slinarez25]

Nope! Unless your cylinder walls are all scuffed up i would recommend it.

 

[danursin]

awesome! where can i find the best priced one? i found a few for around 1700.. is there cheaper?

 

[Rob10_99]

Remember all the additional costs in a rebuild, it's a lot more than just a rotating assembly, you have headgasket, headbolts, water pump, front case gaskets, timing belt job, more urathane from you ripping the back mount out because you forgot it was there,
I think you get the idea.

 

[danursin]

nevermind. i found a kit through slowboy racing... for under 1300...

 

[slinarez25]

Yea that must have been where i saw it, i was going to suggest slowboy but wasnt sure. But good luck!

 

[danursin]

Thanks! hopefully my cylinder walls aren't marked up...

 

[danursin]

so everyone is telling me that no matter what i do ill still get "crank walk" with a 7 bolt. everyone insists that i do the 6 bolt swap then stroke if i want to. if im replacing all of the bearings and getting forged internals why would i still get "crank walk"