knock detection and fuel pres. control

**MADcunz** · 10-08-2007, 01:57 AM

Just had a chat to a workshop owner regarding tuning of my car and he had a few interesting things to say:

1) when tuning a timing map, instead of complicated knock sensing that i should instead run my oil breather hose up to my rear view mirror and keep advancing the timing until i see it start venting oil. Then to back the timing off. His reasoning was this corresponds to the lifting of the cylinder head due to knock.

2) I heard a bit of cavitation in my fuel rail, his explanation was that the factory fuel pressure reg couldnt handle the bosch 044 behind it. He reccommended that i buy an aeromotive rising rate and the problem would be solved.

Bit of background: The person in question was going to tune my car but couldnt, blaming the FPR. The car was then tuned (perfectly) a few days later with exactly the same setup by a different workshop. This individual then went on to tell me that he has been running a stock bottom end 1jz at 36psi and that it can handle 38psi (with 2jz being able to cope with 42)

Just wondering if the above information i have been given has any logic and sense behind it. Cheers

**The Real Roadrunner** · 10-08-2007, 03:55 AM

sounds like an idiot to me.
1 you dont want to make it ping then back it off as you can easily hurt an engine in doing so. lifting the head usually ends in BHG so that confirms my thoughts on the guy.

2 factory regs arent bad for most applications but depends on the model.

3 yes you can run that much boost on a factory bottom end but for how long? and unless youre running a gt3582 or bigger why would you.
might be good for a drag car but not a street car.
cheers
linden

**MADcunz** · 10-08-2007, 09:37 AM

thats what my opionion was, if there is enough knock or preignition to "lift the head" the cylinder pressures must be at an extreme level!

im just running a stock 20v reg if that helps anyone form an opionion

**YLD-16L** · 10-08-2007, 09:58 AM

Originally Posted by MADcunz

when tuning a timing map, instead of complicated knock sensing that i should instead run my oil breather hose up to my rear view mirror and keep advancing the timing until i see it start venting oil. Then to back the timing off. His reasoning was this corresponds to the lifting of the cylinder head due to knock.

When tuning timing you are looking for the least amount of timing possible that creates maximum torque (MBT minimum best timing) which on many engines may not be close to the point of knock. Some engines however will be limited by knock.

His method of tuning is hit and miss, even if he doesn't kill your engine he most likely won't have achieved an optimal timing map.

His method is probably the dodgiest I have heard of in a long time.

**brett_celicacoupe** · 10-08-2007, 11:25 AM

Originally Posted by MADcunz

instead of complicated knock sensing

complicated?!

definately sounds like he doesnt know much. probably avoids using it because he doesnt understand it

**briney** · 10-08-2007, 11:53 AM

a while ago, zoom ran an article on using bits of a v6 commodore memcal, and some other bits to make a knock sensing light. i made one of these, and it is amazing ! i had some shit fuel in the car, and the light would light up, then if i opened the throttle, i could hear it ping. i borrowed the magazine from a mate. someone on here may have the article.

**abently** · 10-08-2007, 11:58 AM

Originally Posted by briney

a while ago, zoom ran an article on using bits of a v6 commodore memcal, and some other bits to make a knock sensing light. i made one of these, and it is amazing ! i had some shit fuel in the car, and the light would light up, then if i opened the throttle, i could hear it ping. i borrowed the magazine from a mate. someone on here may have the article.

Can you get/post up a copy of the article ?

**MADcunz** · 10-08-2007, 12:04 PM

i fully agree with the tuning for MBT, i didnt mention that to him as we were only considering road tuning as i find it too hard to measure torque by feel

Regardless of whether it is safe or not, would this method of knock sensing actually work? or is it just a load of wank......

**Norbie** · 10-08-2007, 12:38 PM

Originally Posted by MADcunz

Regardless of whether it is safe or not, would this method of knock sensing actually work? or is it just a load of wank......

Not really. Even if we accept that detonation = blow-by, there are other things which can cause blow-by.

Also his suggestion to "fix" the FPR by replacing it with a rising-rate FPR is pretty dodgy. RRFPR's are for cheap-and-nasty turbo installs, if he knows his stuff he'd be recommending linear-rate only.