engine and drivetrain kitty, kitty, kitty, at what point is a/f mix too lean?

[Guest Anonymous]

I am running 16:1 between 3K and 5Krpm, the rest is around

13. The car seems to be running fine with a big "turbo" push

after 5k, but my concern here is combustion temperature and

engine damage between 3k and 5k rpm, which is probably

used for cruising speed, the question: is 16:1 too lean?

[Guest Anonymous]

URL: http://www.bmw2002faq.com/store/index.html

on load over 3-4k you want to be at about 12-13 for engine safety and max power.

is this on the new A4?

-Rob

[Guest Anonymous]

you really only know much more than you're lean of stoch).

It also makes a difference what conditions you hit this reading. Was it steady-state, or during an acceleration run (lean on deceleration would be entirely normal).

If you believe the reading is valid, you're too lean for maximum power if this is an acceleration run.

If this is steady state, you're also a little lean for maximum economy (ideal is usually considered 15.4:1).

Cheers!

John N

[Guest Anonymous]

Put the alpina pump on and see if there is a difference in reading anddriveability.

[Guest Anonymous]

I think that if you keep the ignition in a safe zone you don't need to

worry. I have heard (from dave redzsus) that if the ignition isn't too

advanced that a lean setting isn't a problem in terms of cylinder temps.

I have a a spot that is 17/1 at 2500 rpm partial throttle and I will soon

try to eliminate it. But for now I am not so worried about it.

[Guest Anonymous]

To start, you should be running about 700mv - 900mv for max power and engine health. Your reading is about 200mv and that is a little scary to a motor.

Three things to try, short of swithing out your pump.

1. After warm-up, try inserting a match book cover between the enrichment lever and its resting stop. This is the area below the "do not touch" screw. This will enrichen the fuel mixture across the entire fuel curve, not a permanent fix but it will give you some information to make decisions on, You may need to insert two or three shims of matchbook cover to get the AF mixture you are looking for. If you get it right this way, a pump builder can take these measurements to make your pump give you the fuel you need.

2. Or, you can shorten the intermediate rod one revolution. The intermediate rod is the 94mm adjustable rod that runs from the pump bell crank to the other bell crank. When you do this you will notice that you can not pin the pump at P1 when you are at an idle position.The bell crank has know rotated towards P2. That is ok, 94mm is a suggested length when everything was new 30 years ago. However, you may notice an increase in idle speed because you have now advanced the pump. You may also notice that the motor may be lean at idle. That is because the fuel curve of the K pump dumps more ccs of fuel at P1 below 1,000rpms. The ccs of fuel at P1 above 1,000 rpms is significantly lower. This shuts of the fuel to the motor on throttle lift off or decel. Quite a smart pump!

3. The other thing you may try that may fix your AF but may hinder WOT is to shorten the shaft, with the thumb screw, that runs from the other bell crank to the butterflies. This will shut down the air a bit, enrichening your mixture a bit. One revolution at a time though.

Hope this helps, the best thing you have going for you, other than you have an A4, is the wide band 02 sensor. Gives you the information to work with and save your motor. Oh, I take it you are running premium gas.

[Guest Anonymous]

URL: http://www.innovatemotorsports.com/

I can calibrate my thoughts now!

BTW this is the wide band gizmo I am using, it is pretty good.

We tested it with another tii that in our opinion was running

perfect, what a surprise: the readings were just around 13

across 2-6k, completely even! Amazing to achieve that with

a mechanical system! That Kfish is a jewel!

I am leaning (no pun intended) towards going with the pump

that came with the set up, hopefully I get lucky and has the

right curve. One variable at a time!

[Guest Anonymous]

URL: http://www.bmw2002faq.com/store/index.html

installed together! Have fun,,, just wait until you get that A4 system *fully* installed... and then get a nice 300deg cam... "turbo" push, indeed!

-Rob

[Guest Anonymous]

Adjusting the shafts is definitely an area to look into, but adjusting the "do not touch" (or actually known as overall enrichment screw) screw is also necessary.

Why are you lean? Because you have left the gas constant and increased air flow. How do you remedy that? Increase the overall enrichment.

I have the "stock" KF in my A4 and it runs perfect. Why? Because we adjusted the length of the shafts and the overall enrichment. Why rebuild a pump to increase enrichment? The pump is fine; it's just not correctly adjusted for your intake system. If you want to go nuts, you can change the 3d cam to perfectly match the air curve of the A4, but it is by no means necessary.

BTW, Pheadrus and Hardy and Beck used to build tii motors with 292 schricks, leaving the overall enrichment screw (Spenser @ Pheadrus called it the "verbotin" screw) at the stock position. The car was then even slower than before the rebuild. My friend, mechanic and owner of the fastest tii (w/ stock injection) ever seen by mankind used to make quite a few dollars fixing that simple mistake. That was in the mid 1980s. Pheadrus has finally wised up.

[Guest Anonymous]

I used to believe as you did until I saw it with my own eyes. Ran my a4 on dyno with 2 stock pumps and an Alpina pump, delivery while "acceptable" (ie will idle smooth and not blow up) with stock pump is not anywhere ideal for power.

There are lots of theories with these old k-fischer systems. Luckily technology has caught up so we can dispell the rumors.

Throw your car on a dyno and you will see too.

[Guest Anonymous]

I was perfectly happy with the way the car ran, it "appeared'

to run fine, but after I pluggled in the a/f in the tail pipe (this is

a poor man's dyno in a way), the numbers told me that things

were not optimized. Yeah, they can ran great, relatively

speaking, but the curve is wrong. You can adjust linkage

and the no-no screw on the pump, but that only shifts doesn't

change the shape. The best you can hope for is a

compromise.

Another idea is to build a cam into the linkage set up to get

rid of the flat spot, but I have to dig out the drafting tools and

the slide rule for that! I keep my fingers crossed that the

pump 2 has a better delivery curve.

[Guest Anonymous]

I have personally never heard of anyone getting one of those systems to run right with a stock cam and a stock pump. Having said that, Josh is no dummy!

Coop

[Guest Anonymous]

so the fuel curve matches the air intake. But you can get it close enough with a "stock" pump and tweeking the overall enrichment screw and the rod lengths.

As with any system, enough dyno time and it can be made even more optium. But, my point is that if you are using a stock pump, you gotta adjust the amount of fuel delivery via the overall enrichment screw. Sorry if that was not clear originally.

[Guest Anonymous]

I agree with your disagreeing with me. I didn't mean to say that was the ideal setup. It is, however, more than acceptable. If you go with the stock pump, you have to adjust overall enrichment. Best world: Pump custom flowed with new 3D cam to match intake. I think that is a lot of money for little gain (same reason my 282bhp 540 doesn't have a Dinan chip to bump it up 15 more bhp. The $750 does not seem worth it to me for a few ponies when it is already fast enough for me).

And, BTW, I'm a democract and will be voting for Kerry, so don't flame me for the joke.

[Guest Anonymous]

A larger cam coupled with the A4 intake system with no change in fuel delivery will only exaserbate the problem. We must think about the choke point for air,is it the intake or at the valves? The A4 intake system remedies the choke point of air at the intake side of the shop, and a larger cam remedies any air flow choke point at the valves. Any total air flow increase, either by the intake system or the cam must be matched by additional fuel flow. The A4 intake system will not nesessarily give you additional air flow by itself if the valves are not letting that air pass through the motor. The larger cam with the A4 intake definitely will. Then when that matches up, you start wondering about the exhaust side of the shop. That is when you get the magic of the Alpina system is that the air flow to each cylinder is equal and can be tuned to be equal. The Alpina exhaust had the tubes balanced, not to equal length but to equal velocity.And getting that balance of fuel, air and timing is what this is all about. Oh well it fun to discuss and play with.

I too agree that a simple adjustment of the "verbotin" screw will fix some of the insuffecient fuel delivery problem, but will not not make it perfect, that is why I was suggesting adding pices of match book covers under the enrichment or verbotin screw. The readings, by doing this, gives you data about the AF ratio. It may correct at some combination of throttle position and rpm, but not all. Then you can add or subtract shims to see what that does at other combinations. Then with that data a pump builder can add shims inside the pump or suggest another cam profile.

Good luck and the turbo push you feel is the motor responding the proper amount of fuel. Get the AF right across all setting and watch that smile get bigger and bigger.