curiousities

[ejust]

first off, what makes the diesel clatter exactly? I figured its from the fuel igniting under high compression and temps, but it seems on my car anyways, it "clatters" more when cold, and at the higher RPMS. Its fairly quiet till about 3k. Just wondered if this was normal. I just checked my timing and it was right at .040" (1.01mm). Compression is aprrox:            445, 485, 445, 435 - cyl 1 thru 4 respectively +/- 5psi on the readings
starts good, milage is like 40mpg (17km/L)

#2, i was thinking of removing the resonator/first muffler - good or bad?
also, if the turbo has a certain size exhaust opening, then what good would a bigger down pipe do? i imagine that would have to be custom made (downpipe)? Ive heard bigger exhaust = faster turbo spool

[jtanguay]

yea the clatter comes from the diesel injectors and kinda makes the pinging clatter.  I notice on my car that when the cold start is pulled out, I can hear the clatter as it is very loud, but when i push it in the noise goes away.   Possibly the engine is timed a little off?  

BTW That is some awesome compression you have on your motor!

[fspGTD]

The diesel "clatter" noise is louder when the engine is cold because when the engine is cold the ignition delay time is longer (Ignition delay are the milliseconds of time elapsed between when fuel is injected and when it starts to burn.)

The longer ignition delay results in more fuel being present in the combustion chamber when burning starts, and when combustion starts all the fuel present in the combustion chamber tends to burn quite quickly.  The sudden combustion of this large amount of fuel in the combustion chamber results in a sudden pressure rise.  The sudden pressure rise resulting from combustion is what makes the diesel "clatter" noise.

[srivett]

If you get the timing out far enough you can get the sound of having 2 seperate diesels under the hood.  My brother's does that.

Steve

[ejust]

when i checked my timing, it was like at .036" (.914mm) and the clatter wasnt too bad (usual when cold). I up'd the timing to .0402" (1.020mm) and it definitely clatters more. The Bentley calls for 1.000 - 1.020mm (.0393 - .0402").  I checked it several times to ensure accuracy. Ive read (i think it was in here too) that some have ran timing up to 1.10mm (.0435").  Is the clatter bad and should i back the timing off?

How does the timing affect performance and milage??  

Can the fact of winterized fuel cause more clatter too?

If im thinking right, blended winter fuel has #1 (up to 50%) therefore a lower cetane number so it causes a bigger delay.  If im correct, then when we get back to straight #2, everything should sound and run normal then right?  

Thanks for your help everyone!!!

[chrissev]

i've been told advance timing for performance, retard it for fuel economy.  Mine is at .038 right now (if the neutrality of the cold start cable in "off" position can be trusted, which is doubtful).