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D-Jet tuning questions?
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mgphoto
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PostPosted: Sun Jan 27, 2013 2:25 am    Post subject: D-Jet tuning questions? Reply with quote

Hello Ray,
I have been reading some of your posts concerning the PCV valve issue and I have a question.
When the PCV is removed and the controlled orifice in place, the breather hoses for the cylinder heads have to be closed off ?
Thanks,
Mike
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raygreenwood
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PostPosted: Sun Jan 27, 2013 10:51 am    Post subject: Re: D-Jet tuning questions? Reply with quote

mgphoto wrote:
Hello Ray,
I have been reading some of your posts concerning the PCV valve issue and I have a question.
When the PCV is removed and the controlled orifice in place, the breather hoses for the cylinder heads have to be closed off ?
Thanks,
Mike



NO! The breather hoses for the cylinder heads are the BEST PCV system built...hands down....outside of an exhaust powered venturi vacuum system. 99% of teh owners have no idea how the factory system works.

If you have a 1.7 with D-jet (the 2.0's "should" be theame but I will have to llok).......the PCV valve itself is in the oil breather chimmney (that square thing with the cork gasket).

Its accessibale from below. Remove the breather and there is a "D" shaped plastic plug. Remove the nylon ring nut from the outside. Now....with a small pick....crack and remove the thin plastic disc inside (if its even still there).
Clean it out and replace it in the oil breaher. No its just a connector nipple.

In the 12mm red line that connects to the PCV nipple....you take a piece of steel or plastic 13mm rod...maybe 1/2" to 3/4" long.....drill a 3mm hole to start...through the center of the rod. Push that plastic rod into the 12mm hose far enough that you can now put the hose back onto the pCV nipple....get it?

The plastic or steel rod is now the restricted orifice in the PCV line...not the PCV valve itself.

The rocker box hoses are essential. The way this system works is that filtered air comes from the air cleaner through the special connector port built into it. It flows to the splitter/flame trap and splits to each cylinder head.

So.....clean air is pulled INTO the rocker boxes....not out of it. The air then gets pulled through the pushrod tubes...whcih is also why D-jet injected vehicles with the factory PCV system have little to no issue with oil collecting in the valve covers. It gets moved through the PR tubes rapidly by the incoming PCV air.

The air then gets pulled through the case collecting fumes, exits the cast in "Z" baffel in the case at the top under the oil breather box...which is an oil baffel. It then exits the oil chimmney and gets pulled into teh intake manifold.

Going to a fixed PCV orifice also keeps the case and heads much cleaner. Ray
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PostPosted: Tue Jan 29, 2013 3:55 pm    Post subject: D-Jet tuning questions? Reply with quote

Got the LM-2 working, we took several 20 min. rides and recorded the data.
I did have a problem with tach signal noise, it did not record rpm data above 3300 rpm.
The AFR data seems useful.

I can see idle 13.88, cruising 15.80 and WOT 11.08 ratio numbers.

Also, because I removed the deacceleration valve, I can see a rich situation on engine braking.

I think if may be a hair too rich?
Thanks for all of your help,
Mike
ps: Ray, any word on the TVS document?
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PostPosted: Tue Jan 29, 2013 5:00 pm    Post subject: Re: D-Jet tuning questions? Reply with quote

mgphoto wrote:
Got the LM-2 working, we took several 20 min. rides and recorded the data.
I did have a problem with tach signal noise, it did not record rpm data above 3300 rpm.
The AFR data seems useful.

I can see idle 13.88, cruising 15.80 and WOT 11.08 ratio numbers.

Also, because I removed the deacceleration valve, I can see a rich situation on engine braking.

I think if may be a hair too rich?
Thanks for all of your help,
Mike
ps: Ray, any word on the TVS document?



lets think about those #'s just a bit. They are not bad....but your WOT is slightly lean.

Idle should be your leanest. Cruise can typically become too lean because of small throttle openings and high rpms re-establishing vacuum.
The WOT should not be quite that lean because you will also be at maximum advance.

So thinking about this you should think about what part of the MPS controls what....and what adjustment controls which part.

There are three adjustments in the MPS.

1. Outer full load stop (the outer plug): This is an impulse type adjustment. It changes as vacuum makes changes. Very quick and very short lived. If the adjustments. If the throttle opens at all (or any vacuum leak or the decel valve etc.)....the copper diaphragm moves outward against the full load stop and causes lessening of pressure on the armature rod causing it to move out of the coil assembly...causing a short enrichment impulse. So....at stationary throttle position (cruise or WOT) this should have no effect.

2. Main load enrichment screw (the center screw): This is a preload adjustment. It puts tension on against the armature rod and the barometric chambers (all in one stack). It really does little to compress the barometric chamber stack all by itself. What it does is shove the whole stack toward and into the MPS coil. This Makes it leaner at idle...and because it preloads the spring in the horn casting of the MPS....it makes the barometric chamber not react so far or as fast when you open the throttle. This is your main fuel mixture screw...as it operates across the entire fuel mixture spectrum from idle to WOT.

3. The inner load stop: This is the inner side of the copper plate. It has a slightly raised ring just like the outer side that bears against the outer full load stop when you stomp on the gas. However the inner stop bears against the plate inside the MPS with the keyhole shaped cut-out in it. Its job......remembering that when the armature rod is pushed INTO the coil it makes it leaner.....its job is to bear against the inner keyhole plate and stop copper plate from being vacuumed in farther and applying any more pressure to the barometric chamber/armature stack....and keeps it from shoving it int the coil further and leaning it out too far. its adjustment is done by using a hollow allen key and turning that raised ring that surounds the center adjusting screw.

That being said....there are other adjustments to how far the armature can be pushed into the coil....but they are factory adjustments and you would have to fully disassemble the MPS to get to them...and at that point you cannot adjust them...so you would make an guess on the adjustment and/or add a shim to the pintle that bears on the main load spring.....not recomended.

So what can you do?

Here is the quandry: At idle.....you could turn the main mixture screw in the center outward until idle mixture is at about 11.5-12. Then by testing, insure that when taking off the line...between teh adjustment of the outer full laod stop and the stroke of the TVS...you get off-the-line enrichment until the vacuum drops....about .5 seconds...and main enrichment takes over.

But that would make your top end even leaner.

Or you can try the adjustment at the control knob on the ECU....that is idle only....to bring down idle mixture....and then bump the center mixture screw upward. But then that makes your cruising mixture even richer.

Or....you can use the same combination above to reduce idle richness (with the knob) reduce slightly the center main adjustment on the MPS to bring your cruise enrichment down just a hair......and then adjust the inner load stop inward a bit more so that the copper plate cannot exert as much extra pressure on the barometric chamber and armature stack and cause leanness.

This is one of the issues of the d-jet system. What is happening is that you are...because of rpm.....re-establishing vacuum just enough to lean the mixture out. Or....it just is not supplying enough fuel across the board.

the way to find out is to check the vacuum at WOT. If its similar or higher than at idle...that is the problem. If its not...you are just out of fuel and need to probably bump fuel pressure up and then adjust all the other adjustments down for idle and midrange...or go to larger injectors. Ray
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mgphoto
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PostPosted: Tue Feb 05, 2013 2:23 pm    Post subject: D-Jet tuning questions? Reply with quote

OK, I pulled the 270 ohm resistor off the TS II and screwed the outer plug on the MPS out a quarter turn, I had to move the ECU idle adjustment 4 clicks clockwise, a slight adjustment to the air bleed screw and back to a nice idle.

This is where I ran into trouble, a jumper wire that I ran from the tach to the input of the LM-2 pulled out of it's shielded connector shorting to ground. I was looking in the engine compartment and notice the smell of an electrical short, that's when I notice smoke from my distributor, pulled the wires to the Ignitor but too late, damage done.

I put the distributor back in the car with a new Ignitor and set the timing 27*

I haven't been able to hook up the LM-2 again to check lambda but on a test ride I did notice a slight ping on an uphill WOT situation. At this point this is no bucking and good off the line acceleration, gas mileage is the next issue to address.
I hope to have more data soon, thanks for all of the help!
Mike
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PostPosted: Thu Feb 07, 2013 11:07 am    Post subject: Reply with quote

Unscrewing the Outer stop only adjusts the WOT mix. You have to unscrew that to get to the inner screw. That inner screw adjusts the mix at partload while the outer screw mounted in the diaphragm is held in place. Turning the inner screw a touch at a time is important its adjustment is in minor turns. You must have a O2 setup to adjust this.
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PostPosted: Thu Feb 07, 2013 1:41 pm    Post subject: D-Jet tuning questions? Reply with quote

Hello Bleyseng,
My intention was to increase the AFR to .80 for WOT. My lambda at WOT was .86 to .84 that's the reason for the 1/4 turn on the outer stop.
My idle mixture is around .988 .

The engine is running GREAT, bucking is gone, rapid acceleration, doesn't bog down at all.

There is a ping on hard acceleration, it starts at about 4000 RPM but it doesn't happen all the time, I am going to recheck the timing.

I am taking the car on a 200 mile tuning session today through the Angeles National Forest. I am going to install the LM-2 and record certain sections of the ride.

At this point I am thinking about gas mileage, I am getting an average of 22 mph, a mix of city, country and freeways at 85 MPH +.
I think I can get 3 more mpg out of a better adjustment.
Any help is greatly appreciated.
Mike
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PostPosted: Thu Feb 07, 2013 4:36 pm    Post subject: Reply with quote

Bleyseng wrote:
Unscrewing the Outer stop only adjusts the WOT mix. You have to unscrew that to get to the inner screw. That inner screw adjusts the mix at partload while the outer screw mounted in the diaphragm is held in place. Turning the inner screw a touch at a time is important its adjustment is in minor turns. You must have a O2 setup to adjust this.



Very good.....but to add to that...the small inner screw adjusts part throttle (partload etc.)....yes true....but is also responsible for ALL mixture across the board. It is your baseline mixture.

you need to bear that in mind as you are tweaking it. Adjusting the center screw too much with a part throttle performance in mind can leave you too lean or rich at idle or WOT.

The center screw adjusts not only the pre-load on the barometric chambers but affects the baseline fuel mixture setting, because as the load on the barometric chambers increases...it moves the armature rod attached to them deeper into the coil.
Getting it too loose or too tight will cause loss of control of part throttle loading as Bleyseng noted.

Also....the outer stop....the large screw that screws into the outer body of the MPS.....is not exactly a WOT affecting adjustment. It will only do that when the throttle is wide open and ALL vacuum is vented to atmospheric.

Typically as rpm increases, that affect only exists for a very short amount of time. The outer load stop as this screw is called....is most responsible for off the line or gear shift/rpm transition enrichment. It is ...along with the TVS...functionally the equivalent of the accelerator pump circuit in a carburetor.

When you crack the throttle the copper plate flexes outward but only for a split second or so. This happens for the same reason why this function does not do that much for that long at WOT. The copper plate has very large surface area.This cross section acts as a multiplier. It takes very little vacuum loss upon cracking the throttle for the plate to flex.
Along with that...it takes very little vacuum at WOT to flex it back in. Ray
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PostPosted: Thu Feb 07, 2013 4:38 pm    Post subject: Re: D-Jet tuning questions? Reply with quote

mgphoto wrote:
Hello Bleyseng,
My intention was to increase the AFR to .80 for WOT. My lambda at WOT was .86 to .84 that's the reason for the 1/4 turn on the outer stop.
My idle mixture is around .988 .

The engine is running GREAT, bucking is gone, rapid acceleration, doesn't bog down at all.

There is a ping on hard acceleration, it starts at about 4000 RPM but it doesn't happen all the time, I am going to recheck the timing.

I am taking the car on a 200 mile tuning session today through the Angeles National Forest. I am going to install the LM-2 and record certain sections of the ride.

At this point I am thinking about gas mileage, I am getting an average of 22 mph, a mix of city, country and freeways at 85 MPH +.
I think I can get 3 more mpg out of a better adjustment.
Any help is greatly appreciated.
Mike



yes...but bear in mind that the outer stop screw has little or no effect at 4000 rpm. You need to put a vacuum gauge on the MPS when you are 4000 rpm to see this. You have more vacuum than you think at that rpm.
Ray
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PostPosted: Fri Feb 08, 2013 11:45 am    Post subject: D-Jet tuning questions? Reply with quote

180 miles 23 mpg mix of city, country and high speed freeways.

No bucking, good acceleration and no bogging down on take off.

2 clicks counter-clockwise on the ECU "pot" half a turn out on the air bleed screw idles at 960 rpm with the headlights on and 1040 rpm with the headlights off.

As for Lambda I measured WOT .83 with a gradual rise to .90 during acceleration. (I do see an even more rich mixture under engine braking .78 )

Idle is at 1.03 .

Oil temp barely cracked 185*.

Adjusted the timing again it was off a slight bit, I do see that my timing mark is jumping to the left and right slightly, I do remember this being a problem but I am not sure what the cause is?

Thanks again for the input.
Mike
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PostPosted: Fri Feb 08, 2013 5:56 pm    Post subject: Reply with quote

Ok...you are spot on enough for now....no more adjusting...yet. You need to do some work on the inside of the distribuitor on the advance springs and [possibly on the vacuum advance stops. I can tell you how to ad an adjustment screw to both vacuum advance and retard if yours does not already have the advance adjusting screw that many 411/412 and 914's with D-jet had. If you have it its a flat head screw in the center of the vacuum advance body.

With age and with wear the mechanical advance plates and springs get some chatter in them. You should with some work get a rock steady timing mark at idle.

Also..do not let ANYONE tell you that baseline idle timing should just be left to its own devices and that WOT advance is all that is important. Both are critical to D-jet and the type 4 engine. Ideally these engines run best at a bare minimum of 8* at idle. Bettter yet is about 10* at idle...rock steady with advance not operating yet (throttle totally closed).

The vacuum advance is to help get it off the line BEFORE mechanical kicks in which should be like 1100-1200 rpm (ill have to check exact...memory failing).

When you get the advance and idle timing dead on the engine will WANT a tweak to fuel mixture.

Also...its advisable after the last tweak to timing and fuel...to do the PCV mod. That can upset the timing mark as well if PCV is kicking in at idle. It also screws with AFR.
Ray
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PostPosted: Sat Feb 09, 2013 11:09 am    Post subject: D-Jet tuning questions? Reply with quote

Hello Ray,
I took a good look at the distributor when I replaced the Ignitor. I had to clean the inside which was covered with burnt oil. I pulled the breaker plate and broke the ground wire between the two parts. I replaced the plate with a breaker plate from a 1.7 which looked identical. With the plate out I checked the tension on the advance springs and the fly weights. Springs were very taut and weights did not move on their own.
It does have the adjustment screw on the vacuum can and there is still paint holding the screw and nut.

This is a '74 2.0L 914 induction system, it does not have the vacuum advance just the retard.

The timing does not seem erratic at idle (but I will check it again), it is at 3500 rpm that it jumps less than 1* in either direction.

Here I am contused, the vacuum line is disconnected so at this point no vacuum advance or retard so the jumping timing mark, I think can not be related to the vacuum can?

Another distributor issue I may have is when I assembled the engine I used a 1.7 distributor I had laying around. When I installed the 2.0 distributor in the engine my high tension leads were 90* off of the distributor # 1 cylinder mark, I just moved the wires to the correct position and the engine fired up without problem. I don't think this would cause an erratic timing issue but it could create a problem with the fuel injection timing?
Thanks again for all of your help.
Mike
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PostPosted: Sat Feb 09, 2013 12:47 pm    Post subject: Reply with quote

Ah....jumping at high rpm with vacuum disconnected. That is usually slack worn in the pivot point holes of the advance weights or rocking/rattling of the upper points plate. You can tighten that up by bending the little "finger" or hook 180* opposite the ball and spring that tensions the points mounting plate....downward so about .004" is the total gap.

So you have no vacuum advance? Is that what I'm reading?

As for timing, the 2.0 and 1.7L distributors should be identical in wire position. In all of these engines...1,2,3, and 4 are all in the same spot. Just be sure you used a 1.7L distributor and not a VW type 3 model....all of which look identical save for the installed position which is different on a type 3.

As long as your drive pinion in the case is installed correctly, the injection timing of either the 2.0 or 1.7 is identical and will be correct when the distributor is timed correctly.

However....just to be sure, you need to be running vacuum advance with this system. Vacuum retard is optional really...especially if you have a deceleration valve and/or fuel cut-off model of TVS. Ray
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PostPosted: Sat Feb 09, 2013 1:39 pm    Post subject: D-Jet tuning questions? Reply with quote

Hello Ray,
Yes '74 2.0L 914 has no vacuum advance only vacuum retard.

I removed the deceleration valve because of popping on over run. I can probably reinstall it as I get a very rich condition on engine braking. There is no fuel shut off circuit in the '74 ECU as far as I know

The breaker point plate is from my original 1.7L setup, I think it is the distributor I used to install the drive pinion.

I will take some time to check the pivot point holes and the gap in the breaker points plate retainer.

I am not sure about the install of the drive pinion as I used the Tom Wilson book, I could have made a mistake but the engine runs great!
What would be the symptoms of the fuel injection timing being off 90* ?
Thanks again,
Mike
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PostPosted: Sun Feb 10, 2013 10:39 am    Post subject: Re: D-Jet tuning questions? Reply with quote

mgphoto wrote:
Hello Ray,
Yes '74 2.0L 914 has no vacuum advance only vacuum retard.

I removed the deceleration valve because of popping on over run. I can probably reinstall it as I get a very rich condition on engine braking. There is no fuel shut off circuit in the '74 ECU as far as I know

The breaker point plate is from my original 1.7L setup, I think it is the distributor I used to install the drive pinion.

I will take some time to check the pivot point holes and the gap in the breaker points plate retainer.

I am not sure about the install of the drive pinion as I used the Tom Wilson book, I could have made a mistake but the engine runs great!
What would be the symptoms of the fuel injection timing being off 90* ?
Thanks again,
Mike



You need to have vacuum advance. the reasoning for NOt having it was not sound on VW's part. Having retard is sound logic....but no advance will cause the need to run your fuel mixture slightly off at idle.

There are also several redundancies in the system here.
1. Fuel shut-off
2. Decel valve
3. Vacuum retard

There are two possible engine conditions to observe:

first condition:
The issue is that on normal decel (getting off the interstate on an off-ramp...throttle closed, car in gear)....your throttle is closed. Because of the high rpm on deceleration (overrun)...vacuum is high so the MPS is giving you minimal fuel. This creates a lean condition. You will already have maximum mechanical advance due to high rpm. Lean fuel with high advance is not a good combination. vacuum advance should not be engaged at this point because throttle is closed giving no vacuum signal but giving retard signal.

This is where the vacuum retard makes sense...and....retard ONLY works when the throttle is fully closed if its hooked up to the right port.

In my experience the TVS shut off is redundent in this situation. You are already very lean and fighting to control advance.

Depending on how your baseline fuel mixture is set up....the purpose of the decel valve is to bleed air ...a small amount of air.....downstream of the TB....to a point in the manifold right near the vacuum tube for the MPS. its purpose is NOT to lean out the mixture on deceleration.....the mixture is already lean. Its purpose is to decrease the vacuum on the MPS....tricking it into thinking the throttle is very slightly open....so it will enrich the mixture slightly.
If the deceleration valve is plumbed incorrectly, adjusted incorrectly or the MPS is adjusted incorrectly....all the decel valve does accomplish is excessive leaning of teh mixture. Not its function. Anyone who tells you different does not fully understand the system dynamics.

Condition two:

Car not in FULL deceleration. This is more like high speed cruise or powered cruise.....like rpm high...coming into a curve.....throttle cracked maybe 1/16th" ...waiting for shift point. At this point most of the same conditions as abive exist.....maximum advance, moderate to high manifold vacuum making for lean fuel mixture......the difference is that the engine is under partial load and transitional throttle, vacuum retard and vacuum advance may intermittantly engage at this throttle opening (some bucking can happen)....dangerous detonation risk.

In this case the vacuum is usually just right enough that the decel valve cannot kick in. The TVS shut-off... if you have it....will fight you tooth and nail if your TVS is not adjusted perfectly. So will a factory PCV at this throttle setting because it kicks in and out at random due to high rpm blow-by increase.

All of these things together at medium to high rpm throttle transition points will cause moderate bucking and difficult driving in situations of twisty turns, heel and toe shifts, autocrossing etc.

its good the ECU has no fuel shut-off. Worthless. I disconnect it on all of mine. Just use the decel valve and vacuum retard.

The problem with vauum retard on all of these engines is that it is "on" anytime your throttle is closed. Also...in reality...it screws up both your ignitiontiming and injection timing.

Why? how? .....Retard is a safety device for deceleration as well as an emmissions device for NOX. But.....in almost all cases i have found for type 4 engines (411/412/914 and bus)....how far the vacuum retard unit retards you at idle is ...criminal.
Bear this in mind....In general if you set your ignition timing to about 8-10* BTDC...which is where ALL type 4 engines should be for best running with D-jet...or else the vacuum signature sucks.......when you connect the line to the retard unit......it will pull your idle timing down to around 5* ATDC..... Shocked .

This means that you can barely idle. This means that you will have to increase idle mixture...air.....which means that yoru resulting MPS adjustment will be crap.....and most people have to dial in more static timing just to keep idling....which throws off your injection timing and WOT timing as well.......sound familiar? This is why you are getting popping at higher rpm acceraltion. You are over advanced and quite possibly lean.

The mechanical advance in the D-jet type 4 dizzy is slightly slow. It does not give you what you need for getting off the line until about 1100-1200 rpm. So you end up with a leaner misture at the MPS to keep from bogging down off the line. This is why you MUST have advance. It affects your entire range of tuning.

What affect would be 90* out have on injection timing? Simple.....it heavily affects mixture atomization....which heavily affects combustion efficiency...which due to the valve overlap on these engines....heavily affects vacuum signature. This heavily affects the movement and reaction of the MPS....which greatly changes the injection rate especially at low rpm.

You can see when the injection timing is far off by plumbing an accurate fuel gauge into the ring main at idle. The poor timing influence on vacuum causes an excessive pulsation to the MPS. The long injector pulse width created causes wild/violent high speed swings of +/- 5 psi...a 10 psi spread...on the gauge. Its a big reason why improperly timed cars cannot get proper control of the idle mixture with either the MPS or fuel pressure combined.
You can backstop this observation with a good vacuum gauge plumbed at the MPS vacuum line. the wild vacuum swings will nearly match the wild fuel pressure swings. Ray
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