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Latest a/f readings


Guest Anonymous

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Guest Anonymous

1k / 14

2k/16

3k/12.8

4k/12.8

5k/14.5

6k/15

7k/12.2

Difference is that mid range is not as lean as before. This stuff is getting too easy. I will be ready for a rebuild soon the way this thing is revving!

For those who are curious, this is how it works with the A4: Once you set all the throtles to close evenly, there is just two adjustment: the enrichment screw in the pump and the linkage from the pump to the crank, that is it! The later supposedly was to be a set dimension (believe it was 290mm), but I believe that is incorrect, small adjustment of that linkage causes the a/f to change, reason: it shifts the crank starting point, allowing to move the throtles differently since it is a sinusodial curve (rotation translated into linear), so where it starts is important because it may initially be moving the other linkage too fast. The other thing that is very important is to make sure that the movement is repeatable and consistent, so no play axially, radially, etc. The enrichment screw is used just to change the mixture across the board. I can go to bed now!

Well, to be correct, there is a third adjustment: reprograming the profile cone in the injection pump (that seems to me the hard way), but you still have to deal with the linkage.

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Guest Anonymous

Dubois, I forget, do you have a wideband monitor?

There is one more adjustment, since you did mention the internal cone. That is the spring that controls the rate of cone rotation with rpm increase. It in effect controls where the fuel curve exists in the rpm band. So looking at your measurements, you may be seeing that the fuel seems to be there, but it just needs to be shifted a bit up the rpm band.

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Guest Anonymous

but I thought the spring and the magnets in the back of the pump did not control fuel at steady state only during acceleration, ie the rate at which you stump on it, in order words gave the car that throtle response... The readings are at steady rpm using LM-1 AFR meter from Innovate Motorsports, wide band o2 sensor.

Test drove it today, very smooth... wonder now what it would be like with 13 accross, future project: cam that linkage, for now I am happy I got my mojo.

Please note, I am not claiming to be a "sabelotodo", I am just sharing my empirical knowledge, so please comment, add or substract.

Michael

72 tii (Bacchus)

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Guest Anonymous

Know it all! :) J/K

Anyway, from what I understand from looking at a partially disassembled pump, and from discussion with the Redszus, the spring does allow some control over shifting the fuel curve up or down.

My Here is how I would describe what is going on:

The engine is turning the pump pulley, the pulley shaft has a magnetic connnection that 'bumps' the cone trying to rotate it, the spring attached to the cone resists this force. As the time between bumps decreases (rpms go up), the force trying to rotate the cone increases, and the cone rotates more, changing the cam profile. So if you increased the resistance from the spring, the cone would rotate less for a given RPM. Or lessen the resistance and it would rotate more for a give RPM. I don't know if the rate of RPM change has an effect on how the cam rotates. I feel confident that if you are at a stable rpm, the cone should be stable at the point it is rotated to.

Make sense? I don't claim that to be a perfect explanation. But it should be pretty close for an understanding of what basically is happening.

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Guest Anonymous

Looking at your a/f ratio from a wideband that should be close, a couple of RPMs would worry me at heavy load.

5k/14.5

6k/15

If you are maintaining the rpm, and not at full throttle, these measurements are not really something I would base a guess at. There are too many variables.

BUT at high load, full throttle, high engine efficiency (in the engines power band) I was trained to look for A/F ratios under 13 if possible for a NA motor. This is a rough guideline. You are not near the rough guideline IMO. It would worry me unless I could confirm the motor is happy via other means.

A good source of more info is spark plug reading.

Doing a dyno pull would be good, and a good place to read plugs. If the plugs read OK for fuel, and did not display signs of detonation, I would feel a lot better about those RPMs.

On the bright side. You say the motor is smooth. That is a good sign that there it is not too far off.

One thing I took away from my recent efi training was - Getting A/F ratio perfect is a good goal, but not one that has to drive you crazy. Get to where the motor is happy and be happy :).

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Guest Anonymous

the injection pump is just beautiful piece of technology. I would look at plugs, etc. Much thanks for the input.

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Guest Anonymous

if you have datalogging capabilities with your wideband. The fuel

supply will vary considerably wiht slight throttle position. I want one

for tuning the tii.

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Guest Anonymous

mixture as the mixture is changing so much ( the kugel cuts off fuel

supply during decel for example) most importantly search the internet

for images of plugs and familiarize yourself with signs of detonation.

That is the big concern and is closely related to timing. If you are

getting leanish reading but have not detonation issues you need not

sorry- however as stated above high load open throttle positions when

lean (and in combination with too much advance) can cause problems.

When I first started tuning the tii I retarded the ignition just a little to

be on the safe side. I too have the LM-1 and it is a very useful tool. I

log rpm and A/F and want to add the throttle position sensor.

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