Author Topic: Just played with my boost pressure (Read 3016 times)

molgrips · « **on:** November 08, 2008, 10:43:43 am »

Got a gague, tried it out - couldnt' get any more than 14psi on my 1.9 aaz. Is that normal? I kept unscrewing the wastegate but didn't go any higher.

I've got a Rover 220D conical boost pin in there, but the stock spring. I was worrying about wasting fuel due to the LDA going all the way down too quickly, but I notice that boost climbs up to max levels REALLY quickly, like less than a second when I put my foot down. So surely I can only be wasting a tiny drop of fuel by having the stock spring?

I was considering stretching the spring out - making it longer would effectively increase the preload on the spring, and hence be like having a stiffer spring. Anyone know what the dimensions of the spring are when it's in the pump? Like, how long it is at no boost and full?

dillenger1 · « **Reply #1 on:** November 08, 2008, 03:45:53 pm »

did you raise the spring seat any?That will increase tension.

Smokey Eddy · « **Reply #2 on:** November 09, 2008, 01:14:54 am »

Shims? I don't know what it looks like but shims always increase tension on springs

molgrips · « **Reply #3 on:** November 09, 2008, 02:18:13 am »

Well yeah, I could try the shims. I didn't look to see if there was an adjustable spring seat...

The thing is, I don't know how much to adjust it. I could pull the pump, sit it on a bench and examine how much boost gives how much fuelling but that's a right pain

jimfoo · « **Reply #4 on:** November 09, 2008, 08:07:01 am »

The stock AAZ spring is worthless to meter fuel as a function of boost. Somewhere on the forum, I posted the results of some tests. The AAZ spring was bottomed out by 4 psi or so, the MUCH stronger Cummins spring I put in wasn't bottomed until 11-12 psi. You can't shim the AAZ spring enough to be effective as even fully compressed, it is only 1/3 as strong as the proper spring.

jimfoo · « **Reply #5 on:** November 09, 2008, 08:11:55 am »

I think what I did for my test was have the pin in place, but the cover off, and with the pump on a scale, I measured the force needed to bottom it out, then figured the area of the diaphragm to find what PSI I would need.

James8485 · « **Reply #6 on:** November 09, 2008, 07:02:12 pm »

you have prob posted it but what if you used the 1.6 TD pin and spring?
like i used that combo in my aaz and if does seem that fuel comes on too quick for it to build boost to burn it, you say a cummings spring when is that close to the 1.6?

can you shim the 1.6 sping in the aaz pump?

molgrips · « **Reply #7 on:** November 10, 2008, 01:32:25 am »

Quote

it is only 1/3 as strong as the proper spring.

So I roughly want a spring of the same dimensions but 3 times the rate? Ok, gotcha

The question is, how will I know if the LDA is working as it should? It'll just mean a bit less fuel used, won't it? Maybe a little less smoke when I hit the pedal, although I don't really see that anyway...