[Vwdiesel] pump effects...

[Mark Shepherd]

Further to my comments of yesterday... 

When I set about timing my Quantum 1.6TD to the 1.0mm that Loren,Nate Gary etc all told me was the 'secret' figure I was trying to get from stealerships here in the UK a few years back THANKS GUYS :oD... This is what I found... 
My Quantum was giving me between 35- 45mpg (4.54litres) 
Initial settings were pump set at 0.88mm 
Cam when locked was wrong giving a crank advance of about 1/2" on the flywheel or 1 &1/2 teeth or about 4 deg. 
Whilst farting about with my dial gauge I found (like Hagar says) piston thrust to be 90 thou....or 2.286 mm 
New fuel economy became 41.5 to 56mpg (4.54litres) or a 20+% improvement.. :o)

Interestingly (To me anyway) I found that the piston thrusts at an initial 2 thou per flywheel tooth peaking to 5 thou per tooth [percieved rotation of flywheel]... which gives an idea of spread of injection (static timing).
 
According to Rogers archives... 
Full load piston squirt is 0.0345 cm ^3 or 34.5 mm^3 
Bore of fuel line is2.25mm dia by 340mm long... or carries 430 CUBIC mm !! 
Hence each new squirt passes7.9% down the bore..or 12.6 squirts to reach the injector ...amazing or what!!! 
So at a guess I'd say DONT BORE DA BORE  eh? ;o) 
How about putting copper wire strands down to reduce bore to counteract compressability of the fuel? 

Mark(The Miser)UK "There's nothing like driving past a bonfire and then realising it's your car thats smokin' " 

======================================== 
Message date : Apr 01 2004, 01:25 AM 
>From : "Will Taygan" 
To : mark at shepher.fsnet.co.uk 
Copy to : 
Subject : RE: [Vwdiesel] pump effects... 
Thanks Mark. 

-Will Taygan 

> -------- Original Message -------- 
> Subject: [Vwdiesel] pump effects... 
> From: "Mark Shepherd" 
> Date: Wed, March 31, 2004 4:17 pm 
> To: "vwdiesel" 
> 
> This is my limited view and may or may not reflect that of the experts 
> The piston in the pump always pumps the maximum fuel...BUT... there is 
> a sleeve that fits outside/around the 'compression chamber' in front of 
> the piston. This piston has a hole down its middle that allows the 
> compressed fuel to squirt back and it is directed to each fuel line in 
> turn via oneway valves at the start of each line. The sleeve covers a 
> further hole in the piston that allows spillage of fuel back into the 
> body of the pump. The point at which this spillage occurs depends on 
> the position of the sleeve. 
> The position of the sleeve is determined by several springs or links to 
> springs pulling on it... 
> 1) The accelerator arm... 
> 2) The max fuel screw... 
> 3) The centrifugal weights that are rpm relatedand also advance timing 
> like the gas engine distributer... 
> 4) (for the TD) the boost pressure from the turbo [which is 
> predominantly engine loading and available exhaust heat] +exhaust 
> flowrate to some extent also...A kind of positive feedback the rate of 
> effect being controlled by the taper of the cone in the aneroid spring 
> tension,and initial position. 
> 5) The Cold start lever I believe only advances the fuel timing and its 
> effect minimises as speed picks up... 
> Well thats my view... 
> Mark (The Miser) UK 
> "There's nothing like driving past someones bonfire and realising that 
> its your car thats smokin' " 
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