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tii injection questions


Guest Anonymous

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Guest Anonymous

I'm still not quite getting this system, although it runs better than it used to.

1. I have 4-wire O2 sensor plugged into a CB Performance CO gauge. Can I rely on this to tell me when the mixture is less than or greater than 14.7:1? It's supposedly not accurate at any other AF ratio, but it's better than nothing if it gets 14.7:1 right.

2. What is meant by "setting the pump ahead of the throttle body"? IOW, what should my mixture be doing when I increase throttle? Right now, it goes leaner. What do you change to get it to go richer with increased throttle?

These questions may seem dumb, but they'll help me understand how this system is supposed to work much better.

Are there any good books on fuel systems?

--Jerry

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Guest Anonymous

For best torque and power, you will need to run slightly richer than stochiometric. It will yeld smoother running and much better torque, especially at low RPM.

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Guest Anonymous

14.7 is a theoretical figure, you would not be able to maintain this in practice through all rpm ranges, lean under load and you will damage the engine (overheating around cylinder head), What you need is the correct mixture under load at full throttle, this you can adjust on the KF pump by the adjusting screw at the rear of the pump next to the fuel outlet return pipe in to richen out to lean, only a 1/4 of a turn at a time, with an A/F ratio gauge you are going to have to blast up the road a few times to get it right but they do work.

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Guest Anonymous

The factory book says set the pin in the throttle body and in the pump and your good to go- thats it in terms of the mixture acoss the range. When I did that I could adjust idle just fine but if I gave it any gas the mix leaned out. This was using a CO meter at the tail pipe which is really only accurate for setting the idle ( I think) Howver I was concerned about running around lean so I figured I would try to get it rich.

The throttle cam is shaped in such a way that at the beginning of the cam there is little change relative to the curve up to/at WOT. So I "set the pump ahead" of the curve by closing the cam more with the initail setting. That is to say that with the pin in the pump the cam over lapped the hole for the pin in the throttle body. Effectivly this should advance the pump position relative to the throttle curve.

In terms of the screw on the back of the pump- I believe this just affects the mix across the entire range. I am not sure but it seems that adjusting it would affect the high end and low end equally.

As I have also recently purchased an A/F meter I'll be looking at this al again soon- so let us know what you find out!

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Guest Anonymous

What sort of readout do you have? At idle you want 2%-4% CO; if everything else is set up OK, the mixture will be correct elsewhere. If your readout gives you some resolution in the 2%-4% range, it will be useful.

"setting the pump ahead of the throttle body" is done by loosening the clamp under the throttle body and turning the TB shaft relative to the bell crank below. This can be useful if the stock adjustments do not give the correct mixture above idle. Jim Rowe describes how to do this in an old tech note, whose location on the web, if any, I do not know. Email me for a copy.

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Guest Anonymous

Most of the experts recommend not messing with this screw. This is especially good advice if you don't have a proper gas analyzer to check your results.

The screw is set when the pump is calibrated; if it needs to be changed, the pump needs work.

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Guest Anonymous

but I've done it, just a 1/4 turn at a time and keeping

written notes, so to have a road map to get me

back. The problem that I had was too lean of a

mixture across, and knocking, 1/2 turn later and the

problem has gone away for good. The screw used

to be sealed at the factory, but my understanding is

that it only shifts the fuel curve up or down, the one

in the tuna can tilts it, and everything else connects

fuel to air. This is kind of my visual picture, I wish

someone could illustrate this better...

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Guest Anonymous

14-6965726.JPG

The readout is temporarily mounted in the seatbelt warning cutout until I don't need it anymore (see photo). I got it from CB Performance. The display units are AFR, with 14.7 having it's own special mark. Range is 12 - 17. It swings pretty radically, usually pegged at one end or the other.

Just a bit of rambling thoughts...

Can a well-adjusted k-fisch maintain fairly constant AFR over the normal operating range, i.e. under the typical variations of engine speed and throttle position? According to my gauge, this one's not even close to being able to do that. It's especially bad at the factory "pin" setup positions, it runs pegged on lean all the time except at idle. I've moved the half-moon almost completely over the 4-mm pin hole to get it to run halfways decently.

Linkages were new this year. The bellcrank ball was badly worn, so I got a real nice used bellcrank. There is still a little slop in the bellcrank-pump linkage ends. Anyone ever add a pad to the linkage-end socket to take up the slack?

What's everyone's favorite fuel pressure gauge?

--Jerry

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Guest Anonymous

I've hesitated to mess with "the screw" so far. I'm not totally sure everything else is right yet.

I still need to verify fuel pump pressure. Any recommendations on a gauge for this?

--Jerry

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Guest Anonymous

that connects the pump, throttle and firewall (attached to the block) then the bottom ball that rests in a socket on the pump housing has a small plastic bushing. You probably know that but just checking.

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Guest Anonymous

is that the pressure relieve valve opens at 28 psi. So if you have return at the tank it whould be ok- I guess that assumes that the relieve valve is in good shape but its hard to imagine that it wouldn't be. At any rate I have had the exact same problem so.... In the end if it cannot be resolved my plan is to recurve the throttle cam- but hopefully it won't come to that.

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