Author Topic: truck up and running, but power down a little (Read 4430 times)

jimfoo · « **on:** June 30, 2008, 10:44:24 am »

I got my truck running, but the power seems to be down a bit from what it was before, particularly the top end. Things I changed were: reduced internal pump pressure after I checked it and found it to be 55-60 PSI. This had the effect of allowing the dynamic advance to not be almost fully advanced all the time, but probably delayed the advance curve. I also put some shims back into the timing cover, but my timing plunger has 2 springs, a heavier outer one which acts on the entire plunger, and a smaller inner one which acts on a smaller inner plunger(function unknown) but it can only move so far. This smaller one is what I put the shims back on. I did this because it seemed to me to be advancing the timing to fast before. I also put in a different cam plate with more lift, but a steeper and shorter profile. I also lengthened the arm on the throttle shaft, but this should give more power if anything.
My thoughts is the change in pump pressure is what made the majority of the difference, but I would like others thoughts.

jimfoo · « **Reply #1 on:** June 30, 2008, 10:47:48 am »

Also boost is down a little, which to me seems to be due to less fuel, though the vanes seem a tiny bit sticky, so it may just be that.

jimfoo · « **Reply #2 on:** July 02, 2008, 11:02:55 am »

I got the boost back up. A combination of adjustments/1 spring coming off. F-ing new rear main is pissing out oil now though! :evil: :evil: GRRRRR!!! Power is still down from what it was. I did retard the timing just a little, and it sounds much better though. I'll have to check the boost pin and make sure it's rotated the right way. Aside from that, I'm wondering if the extra lift from the new cam plate hurt me in the sense that the bleed hole in the plunger may be opening more than with the old cam plate. That or I'm also wondering if somehow the higher internal pressure lead to more fuel delivery. Oh, and smoke is way down. I am getting a little sometimes as the turbo still leaks a little oil, but between it leaking way less, and me tapping the IC drain bolt and putting in a line to blow excess oil back into the crank breather pipe, not much makes it to the engine.

jimfoo · « **Reply #3 on:** July 02, 2008, 01:51:53 pm »

Well yes, but seeing how it's only 3/16"ID and about 4' long, not much air gets through it. But it will push oil when it has a little boost behind it. My VNT will still easily make the 18 PSI I run it at

veedubcanuck · « **Reply #4 on:** July 02, 2008, 09:27:43 pm »

The boost pressure leaking through your drain tube could be pressurizing your motor blowing oil out your main seal.. Just a thought

jimfoo · « **Reply #5 on:** July 03, 2008, 12:13:39 am »

Even at full boost, there is nowhere near enough air going through it. It really is a small line, about the size of the one on the LDA and 4' long. Plus I have a 3/4" breather which would carry more than enough air to prevent pressurization. think the leak probably has to do with the brake cleaner I sprayed the seal with (like my IP leak) or the metal bits I was trying to clean off with the brake cleaner.

Powered by Spearco · « **Reply #6 on:** July 03, 2008, 02:04:20 am »

Speeking of spraying brake clean, I was trying to clean off some dirt and fuel to find a fuel leak while the engine was running and WOW, that was a close one. Motor started to runaway. Very weird though if fuel leaks out due to pump presure, how, and why did the brake clean cause it to rev up?
Sorry Jimfoo, just saw that and thought I'd ask.

jtanguay · « **Reply #7 on:** July 03, 2008, 02:19:07 am »

Quote from: "Powered by Spearco"

Speeking of spraying brake clean, I was trying to clean off some dirt and fuel to find a fuel leak while the engine was running and WOW, that was a close one. Motor started to runaway. Very weird though if fuel leaks out due to pump presure, how, and why did the brake clean cause it to rev up?
Sorry Jimfoo, just saw that and thought I'd ask.

try spraying brake cleaner into the intake :twisted:

Powered by Spearco · « **Reply #8 on:** July 03, 2008, 02:22:50 am »

I know, well not really.

Powered by Spearco · « **Reply #9 on:** July 03, 2008, 02:23:44 am »

I know, well not really.

veedubcanuck · « **Reply #10 on:** July 03, 2008, 06:25:30 pm »

LoL I did that once too, not thinking that it would suck up the fumes through the intake.. Scared the crap out of me.

Tintin · « **Reply #11 on:** July 08, 2008, 10:41:02 pm »

I heard about injecting brake cleaner in tractor puller... loll, but I never tested in my car... probably a rumor, I dont know.

Jimfoo, you have now good experience with M-pump and the answer is in some post here, but.....

Adding lift on came plate that change nothing, euuhh... yes and no, It's complicated to explain, but it's not your entire problem.

More aggressive slope on the cam without other modification that affect the fueling amount, more movement is needed from the control collar to obtain the same fueling as with the previous soft came plate, but you get the fueling in shorter time with aggressive came.

More aggressive came create more counter force on the carrier roller,( exponential as the rpm goes up), more pump case pressure is required to move the timing piston, extra came lift have a little effect in this way too, like adding more shim on timing piston, or bigger head plunger, or playing with the fuel screw also affect the counter force, etc....

I think the biggest problem is that you play with the wrong regulator, not the entire regulator, but the spring in it.

Always set the pump timing at 1mm with dial gauge and weld it in place.. loll..!! It's a joke, but 1mm.... and fine tune only with different combination of regulator (spring in it) no need to monitor the pump pressure, It's a waste of time and that say nothing on the timing position.

A good timing value for M-TDI is 3-4-5deg at idle to 15-18 deg at around 4500rpm, your regulator give the correct pressure for a correct timing at idle, and not enough pressure to get 15-18deg at 4500, you have probably 8-10 deg at 4500rpm, and if you tap too much on the regulator, you get too much timing at idle and lower rpm range for what you want in the high rpm range, you have to put a harder spring in the regulator, to keep the same pressure (timing) at low rpm and more pressure (timing) at high rpm.

I think I already explain how the two spring timing piston work, It's easy, the small spring in the centre is attached to a small regulator in the timing piston, and the pump pressure act directly on this regulator to bleed more or less pressure behind the timing piston, this type of timing piston are less affected by the carrier roller counter force, also less piston oscillation when the pump rotate.

A good control collar lever would not be a luxury............

jimfoo · « **Reply #12 on:** July 09, 2008, 12:04:31 pm »

I ended up increasing the internal pressure a little, maybe why my cold start clip popped off again, but I replaced it with a bolt, so no more leaks there. I never used the cold start anyway. :twisted: I can't time with a dial indicator as I can't get it in the pump unless the engine is out, so that's why I have a timing light. Yes, I probably have too much initial advance, and should probably do as you say and find a different regulator spring. I may try modifying a lever at some point, but it will have to wait until I have a spare as I don't want to screw it up.
So for the small timing piston spring, you are saying a softer spring will bleed more pressure from the timing piston, meaning more pressure will be needed for a given advance?
Thanks for the reply.