Injection timing?
 

I have heard of folks running 1.00mm for injection timing. I am curious what you guys think in terms of a timing setting on a D24 NA... I am wondering if it really will make any difference. I measured my piston height on my engine rebuild today, and determined that it is a 2-notch gasket as per the green book, but that I can safely go to a 1-notch gasket, which is what I will be doing. I want to have an idea as to what to run my timing at for the best performance and economy (economy is more important). Its a BW55 slug, though should be much better with the fresh motor with .040" OS pistons...

I have heard of some VW IDI guys running up to 1.10mm. That's too far in my opinion. When I was messing around with the old motor in my 244 I had a total timing advance of 1.05 (my altitude compensator did not have power to causing it to have full advance throughout the RPM range) And it drove fantastic with that amount of advance. A whole lot better then .85mm.

Has anybody here put a pressure gauge on the IP to see what RPM the IP starts to advance? I was thinking of losing the dynamic advance all together and running a static timing of 1.10 (that would be from idle to redline) That way I could get better lower end power and not have the advance to high in the upper RPM range to slowly damage the motor. This is how inline IP's are. Any thoughts???

I have tried many timing settings up to and including 1.1mm on my volvo and my 1.6 jetta TD I had. Any more than 1.0mm gave no increase in mpg, only noise. Extra timing really only starts to make a difference when you pushing alot of fuel and trying to make power at higher rpms. The bigger players in economy are engine condition, especially compression which you have addressed with a rebuilt engine, and injector condition and calibration.


As for the IP advancement, it should start to advance right off idle, and will actually advance in relation to throttle position even at idle speed. That is adjustable as well, but not something you should mess with unless you have lots of experience or a pump bench. "locking out" the timing would only lead to poor performance at lower rpms if your locking it at full advance. As for too much advance up top, the pump is limited by design, the pin that rides on the advance plunger can only travel so far before hitting the body of the pump as the internal assembly rotates.

Jason

Interesting stuff Jason... I had wondered about when the advance starts working and how it reacts to throttle position. I assume that is one of the things that is altered with a performance pump build, like Giles etc.

I agree, I would not think about disabling the dynamic advance. I think it is one reason the rotary-pump VW engine designs work so much better out of the box than the Mercedes with inline pumps. A non-turbo D24 is 2.4 liters and makes 82 HP... a non-turbo MB OM616 (240D motor) is the same size but makes 67 HP with an inline pump. The VE design is pretty neat once you get to know it, though of course the Mercedes inline IP is happy pumping river mud, while the VE pump is a little more picky about fuel quality and filtration...

Mike, I usually set mine to around .92. I would not go any higher than about .97 unless, as Jason said, you are using a lot of air and trying to move a lot of fuel. On a stock non-turbo motor, I doubt you will see any advantage beyond about .95.

I got my hands on a timing light that clamps to the injection line today. I have suspected that my dynamic advance did not work. When I put the light on I was able to see it advance ~3 degrees with the cold start on and about the same with the altitude compensator. The issue is when I rev it, the timing goes the about 5 degrees the other direction (retarded). This may explain my excessive egts and lack of top end power. I am not sure where to start on making the pump advance correctly as I can hardly find any information on it.

Did this problem just start happening? Or was it a slow deterioration? What is the condition of the fuel filter?

Was this IP ever opened up? Possibly to reseal one of the little side case covers? It's possible that the spring and washers (part of the advance piston assy.) flew out and didn't get put back in the correct orientation.

Remember that the internal advance mechanism works off of the pressure differential between pre- and post-internal vane pump. If you are feeding the IP (and therefore internal fuel pump) pressurized fuel (as in a pre-IP electric "helper" fuel pump), you may even be reducing that pressure differential and hence reducing further an already weak dynamic advance curve.

Apparently, worn IPs (specifically the IP's internal fuel transfer pump, the rotary vane pump) struggle to provide sufficient internal fuel pressure to activate the dynamic advance correctly. Here is some good reading for you on the methods of measuring the internal IP fuel pressure, and how to adjust the internal pump's pressure output to produce the proper advance: Internal injection pump pressure
Please note that that discussion is pertinent to the Bosch VE IP model(s) installed on the VW 4-cyl engines; possibly the D24 version has different specs?

Open question to all: Does anybody know the IP internal fuel pressure specs for the D24/D24T IP?

There/s nothing to make it different from a 1.6 really.
I wouldn't worry about a clicker pump, VE Cummins run a 7-12 PSI lift pump, and worry about the front seal blowing out of the housing if they raise that much past 20.

Well I only now just checked the actual timing. I suspect in the time I have owned it, it has never worked properly. The pump didn't respond to adjustments like other VE pumps I have messed with and has always has always been pretty flat on the topend power wise. Even with the compound turbos and shimmed governor its a dog in the higher rpms.

I am going to change the fuel filter tonight just to see (I have doubts, it was new and drove just like this). My only thought is that maybe he diesel cleaned something off the fuel tank and clogged the filter in short order. If that does not get me advance then I will make a adapter for a gauge and set the internal pressure. I suppose if that does not work I am in the market for another pump :-/

I dont think its a problem with the advance mechanism itself since the altitude compensator works perfectly.

We will be interested in the results; please post them! (My own hunch is that there are many of these IPs out there running with subpar internal pressure/dynamic timing.)

Take it that you understood you need to tap the pressure reading upstream from the out bolt restrictor orifice? Wasn't that in interesting link?

I am interested to see as well. While I suspect there are a lot of pumps running around in this condition (likely not as horrible feeling in a 3000lb sedan as it is in a 5000lb truck). It may be the reason this engine came off the road. I am not sure that it means a "dead pump". It might just be a matter of re sealing the pressure regulator and making sure it operates smoothly.

I replaced the fuel filter at lunch today and it has a smidge more power on the bottomed but still nothing up top. Egts might even climb faster than they were.