Author Topic: mechanicaly increasing fuel - AHU pump (Read 4001 times)

entuzijast · « **on:** January 03, 2007, 04:25:10 pm »

Is there any way to increase fuel on AHU pump mechanicaly?

RabbitGTDguy · « **Reply #1 on:** January 03, 2007, 06:50:21 pm »

You can increase the internal pump pressure which ends up knocking pressure inside the pump up and therefore output to an extent if you want too...but you have to be careful with it...

It involves using a punch and a light hammer and "tapping" the pressure relief valve (look where the pump fuel inlet is...now "in back" of that, more towards the engine, looks like an "squared oval with a circle in the center, countersunk in" usually marked from the factory with yellow paint.

Insert the punch...a tap that center portion just a little...ever so slightly (you should see it move and leave a slight mark from where it "used" to be and where it will be) and internal pressure is increased... some have seen a little bit of gain off this...others, a bit less noise...but TRIED AT YOUR OWN RISK. If you tap it TOO far... the collar that retains the valve will plop down into your pump and the only way to get it out is to remove the valve, fish out the collar, diassemble the valve, tap it back up through and start over

There is some info on it over at TDI club if your interested...maybe on here as well, but not that I've seen in any threads.

And...this is not to be confused with the "Hammer Mod" used on eTDI pumps

Joe

hillfolk'r · « **Reply #2 on:** January 06, 2007, 02:26:25 am »

yea be careful with that mod.....
when my guy set my pump up on the stand
he said to not push that pin in too much
something about letting internal housing pressure go much above 120 psi can cause pump failures very fast

entuzijast · « **Reply #3 on:** January 06, 2007, 07:44:16 pm »

What power gains can be expected?
Engine is currently chiped to 120 ks...

QuickTD · « **Reply #4 on:** January 06, 2007, 08:26:47 pm »

I would expect very little power gain from increasing housing pressure. Diesel fuel cannot be compressed at any reasonable pressure, so increasing housing pressure in an effort to "squeeze" more into the plunger chamber won't work. Injected quantity depends on plunger displacement not initial pressure. You will alter (advance) the timing throughout the range, leading to more noise and higher peak cylinder pressure.

A larger plunger will increase the fueling level. Other electronic means can be used on top of the chip, tuning boxes or the "Evry mod" are effective and cheap. Look here for evry mod info http://forums.tdiclub.com/showthread.php?p=120184

RabbitGTDguy · « **Reply #5 on:** January 06, 2007, 11:06:46 pm »

Increasing pump pressure can increase/decrease the amount of noise from the motor..I've seen this in the mod. Howevr, it does come in handy slightly when you are messing with larger nozzles, etc. where you need to adjust up your breaking pressures (especially on earlier TDI's... 1z and AHU/AFN) to make things run more nicely...and quietly to an extent...
It does work...but isn't a flat out of the box modification to the pump nor did I recommend it to be this way.
Hence the diclaimer as well. Only something to do if you have the right motor setup to do it with...larger nozzles, higher breaking pressures, etc. There, it will make a bit of a difference...

Otherwise, things just get noisy

Joe

entuzijast · « **Reply #6 on:** January 07, 2007, 05:28:48 am »

Yes, larger nozzles should be in the game...It's a friend's car, and he sais that software that gave him 120ks, was made like the engine had 2.5TDI nozles, although it didn't...So they will most probably be installed...