govenor removal

[Dropout]

I'd like to comment on the idea that the spring needs to be kept at the same installed length. Noting that the the TD has a slower advance curve than the 1.5, isn't it true that increasing the installed length by 3mm will reduce the spring tension and quicken the advance curve?

That's a good thing right?

Dropout

[VWRacer]

Advanced timing increases cylinder pressure. A bit too much and bye bye headgasket.

It is important to distinguish between static timing and dynamic timing. If static timing (set at the pump, such as with 1.2mm) is too far advanced, then yes, the engine can suffer from excessive pressures. This can show up as low power, growly noise and blown head gaskets. Dynamic timing is the advance curve built into the pump, and typcially varies with RPM. Our diesels cap the timing at something like 20 degrees, which is in accordance with their design philosophy for these engines as lo-po econoboxes. I don't know where the max power point is, but it's got to be close to 30 degrees. Even this will result in lower peak cylinder pressures than a low RPM, high torque demand setting.

In short, I would not worry much about allowing the advance curve to extend well beyond the stock point at high RPM, so long as the static timing is set not more than about 1.1mm, based on fspGTD's posts on the subject.

[fspGTD]

I'd like to comment on the idea that the spring needs to be kept at the same installed length. Noting that the the TD has a slower advance curve than the 1.5, isn't it true that increasing the installed length by 3mm will reduce the spring tension and quicken the advance curve?

That's a good thing right?

Dropout

The timing advance can be plotted of timing advance vs engine RPMs.  Changing the spring pre-load will just shift the curve, just like changing static timing (mm plunger displacement at TDC measurement).

If you want to change the SLOPE of the curve, you'd need to change the spring rate.  (Which is how much the spring collapses given a fixed amount of additional force.)  This is a property of the spring itself; varying the pre-load will not change it.  So you'd need to find a new spring if you wanted to change that.  But this isn't what I want to do either.  Dyno testing has shown at least for my injection pump / injector setup, the factory timing curve is ideal for all RPMs up to somewhere above 5000 rpm.

About that point however, although my testing is not perfectly conclusive, it suggests more timing advance would give more power.  Based on my hp vs RPM plots from the G-tech, I see a sharp kink in the curve at 5200 rpm and based on hat, I am theorizing that this is where the stock timing advance mechanism stops moving, because it gets blocked by the cover.  (So if you looked at the timing advance curve that showed RPMs going this high, the curve would switch from a straight, constantly increasing line abruptly to a dead horizontal line.)  My goal of getting more travel out of the mechanism is keep the line straight up to a higher RPM, so hopefully it never gets to the dead horizontal area.

[DieselsRcool]

Wouldn't changing the internal pump pressure via an adjustable outlet oriface change the curve also? :shock: So many variables!

[fspGTD]

Wouldn't changing the internal pump pressure via an adjustable outlet oriface change the curve also? :shock: So many variables!

 Yes it would change the slope of the timing advance curve.  As would messing with the pressure-regulator mechanism that is built into the pump, screwed into the top near the pump's inlet.  But neither would allow more overall advance capability like machining the timing advance piston or cover provides.

[fspGTD]

Alright guys... I finally have got the timing cover machined now.  (Long story short... Someone was going to do it for me, but they were stalling and taking forever, so I had an opportunity at my school to use their machine shop, I just took the part back and did it myself! )  Anyway, the dimensions of material removed from the inside of the cover are a cylinder shape with the diameter of 25mm and a depth of 3mm.  Sorry for the crappy pics but hopefully you get the idea what it looks like:





I'm looking forward to trying it out, and am going to take some before/after measurements with my g-tech pro competition accelerometer (after I get it's tachometer calibrated) so I should be able to post some before/after hp&tq vs rpm curves!  Hopefully sometime this week (but maybe next week!)  

[Turbo DS]

Looks proper Jake.  Let us know how it improves the output!

[fspGTD]

I just did a really quick and dirty calculation to estimate how much higher I might be able to revv my motor with the timing advance still working without running out of room, for the extra 3mm clearance provided by the reliefed cover.  Doing a quick guesstimate for the distance from the center bore of the injection pump to the pivot point of the timing advance mechanism, I figure it might be 1.8".  3mm displacement at a 1.8" radius (arctan(3mm/1.8") gives 3.75 degrees (pump degrees.)  That would equate to about 7.5 crank degrees extra advance allowed by the 3mm cover relief.

Using data taken from here:

Also, here is a plot of the 1.6lTD's timing advance specifications, from the 1.6lTD SAE Paper:
http://home.comcast.net/~vwgtd/tdsae/f40-f42.jpg (huge pic - scroll to the right to see figure 41, timing of the 1.6lTD.)
This graphs looks to be in pump or cam angles and pump rpms.  It shows timing advancing from 0 pump degrees starting at about 480 pump rpm and ending at 6 degrees advance at 2250 pump rpm.  No rpms higher than 2250 are listed.

Converting those to crank degrees and crank rpms (multiplying them by 2), we could have 0 degrees at 960 rpm and 12 degrees at 4500 rpm.  That's a rate of change for the 1.6lTD advance mechanism of 3.39 degrees per 1000rpm.  Doing a rate of change calculation for the 1.5lD gives is 5 degrees per 1000rpm.  This illustrates that the 1.5l timing advances at a quicker rate than the 1.6lTD timing advance mechanism.

...(in particular, the part about the 1.6lTD timing advance working at a linear rate of 3.39 degrees advance per 1000 crank rpm) means that the 3mm-relieved timing advance cover should allow things to advance for approx 2000 crank rpm higher than stock before the timing advance piston hits the cover.

Assuming my hunch is correct that the piston hits the stock timing advance cover at approx 5250RPM, I would estimate that with the 3mm relieved cover, I should be good to go, with timing advancing at the usual linear rate, up to 7250RPM.  

(It is too bad I didn't get a chance to test this prior to my motor's valves getting crunched by the pistons...)

[fspGTD]

Well there is a lot of territory in the upper-RPM area left to be tested, IMO... 5750RPM (ish) while still delivering full fuel is the highest I've had my revv limiter set to.  Through dyno-testing, I found what I would describe as a limit here, or a drop-off of power, due to inadequate timing advance.

And I should correct you that we still don't know at what RPM valve float occurs on these motors.  It could be 7000RPM, or it could be significantly higher.  I may have revved the motor to 8000+RPM when I mis-shifted into first.

If the bottom end of my current motor is in decent enough shape, I might be inclined to use an econo-rebuild cheap-o head (maybe even just slap on a good used one...) and do further testing into the upper-RPM region.  Worst case, I'd just be out a cheap-o head rebuild.  I could try disabling the revv limiter completely, as well as trying out the timing advance mod.

My current motor is still behind the top FSP JH gas engines both in terms of both peak power output (although it's close) and width of powerband (means I need to do more shifting.)  But I think there still may be uncharted territory in the upper RPM region worth investigating...

[dieselpower]

are there any high preformance/rpm valve springs available for our diesels? will the ones from gassers work? because if we could eliminate valve float at say 7000 rpm and move it up to around 8000 with different springs then the only thing stopping us from revving this high would be the fact that the diesel cant burn fast enough.

[QuickTD]

Oddly enough, the gassers  often use diesel springs in heavy duty high rpm applications. Not sure how gasser aftermarket springs would compare to diesel springs.

[lord_verminaard]

Another question is if the JH solid-lifter spring/lifters are the same as the solid-lifter TD head's.  (I dont have ETKA anymore, so cant check...) If so, Autotech has dual sport springs that are good for 7k or so that fit the JH engines.

Worth a shot- they might be close enough to work with "minor adjustment".  

Brendan
84 Scirocco 8v
00 Camaro L36 M49

[fspGTD]

For '84 Rabbit, ETKA makes no distinction across different available engines, diesel or gas (EN, JF, JH, CR, JK, CY) for valve springs.  This may mean that all solid-lifter VW motors got the same dual valve springs.

It lists "spring - valve, outer", part number 078 109 623A, and "spring - valve, inner" part number 078 109 633 A

Can anyone verify that a solid lifter gas engine uses dual valve spring (inner and outer?)

If so, I'd say there is a good chance that the valve springs on a solid lifter 1.6lTD would not cause float until above 7000RPM... as they do on a JH (solid lifter '83-'84 GTI 1.8l gas motor)

[lord_verminaard]

Well, crap- if my car was here, I'd pop the valve cover off real quick and check.  I want to say yes, because VW changed to a single-valve spring starting with the A3 8-valves.  (and autotech sport springs work on all 8v engines up to 1995)  After that, they sell a "conversion" kit to use their sport springs on the 95 and up engines.  

So my educated guess, is yes, early 8-valves use dual springs.  

Anyone else have evidence to support or deny that observation?

Brendan
84 Scirocco 8v
00 Camaro L36 M49

[caddy]

For '84 Rabbit, ETKA makes no distinction across different available engines, diesel or gas (EN, JF, JH, CR, JK, CY) for valve springs.  This may mean that all solid-lifter VW motors got the same dual valve springs.

It lists "spring - valve, outer", part number 078 109 623A, and "spring - valve, inner" part number 078 109 633 A

Can anyone verify that a solid lifter gas engine uses dual valve spring (inner and outer?)

If so, I'd say there is a good chance that the valve springs on a solid lifter 1.6lTD would not cause float until above 7000RPM... as they do on a JH (solid lifter '83-'84 GTI 1.8l gas motor)

i think they could be over 7000 because the cameshaft of the idi is very softer than the gti.