To get a Lambda computer or not? '87 engine
 

I'm putting a stock '87 930 engine in and am contemplating whether or not it will need a Lambda computer to run properly.

I've read threads about improving performance without it, and I'm not concerned about emissions.

All the Lambda do is lean it out a bit,, you could spend your money on a DWUR and get better performance and better MPG too!

DWUR sounds better to me.

I've read about one, and only one so far.
Can you recommend one?

Unwired tools is the only one I know about,, I love mine

Just unplug the O2 sensor and tune your car without it. Be aware that there is still the frequency valve that will continue to do its thing in an open loop mode (you'll still hear it buzzing back behind the fuel distributor), but when unplugged the lambda will no longer have any affect on leaning out the mixture to meet emissions standards. Just set your idle mixture where you want it and go.

Sounds easy enough

Thanks!

My understanding is a stock 87 930 motor needs the Lambda computer to run.

If you have the Lambda computer you can unplug the O2 to disable the Lambda function so you can run richer but you still need the computer.

Alternately you can have the Fuel Dist modified so it no longer utilizes the lambda frequency valve (closes up an internal passage ) or use a non Lambda fuel distributor.

Yes, you still need the computer but with the O2 unplugged all it's doing is maintaing a fixed duty cycle at the freq valve. Otherwise you're correct in that the fuel dist. would need to be modified.
I popped this topic some time ago, wanting to do away with the freq valve altogether and even tried running the car without it plugged in. No-workie. Unfortunately it's just one more thing left that can fail.
Jim Fairman can describe what would need to be done to the fuel distributor to accomodate running without the valve. It's beyond my scope.

Can someone post a picture of the Lamda computer?
The engine I bought came "complete"

If you don't have a lambda computer or k-jetronic ECU, than only get one if you need it to pass emissions.

The k-jetronic lambda ECU does nothing other than run the lambda emission system that uses a narrow band oxygen sensor in the exhaust to monitor oxygen level and a frequency valve / inline injector pulse valve on the fuel head that makes small changes in the fuel mixture to keep AFR's around 14.7:1 to pass emissions so they could sell the 930 in the USA again in 1986.

At full throttle the throttle position switch on the throttle body puts it into open loop mode and the AFR goes richer.

K-jetronic lambda control was calibrated with the better quality gasoline that was around in the mid eightees and not the low quality ~E10 stuff that has oxygen in the ethanol molecule we get from pump gas today. Today's E10 gas leans out the mixture a little because of that so it should run a little richer than the gas from the eightees to run as smooth.

Some people have removed everything electrical under the driver seat. The lambda computer or k-jetronic ECU, the enrichment relay that bypasses the lambda box at full throttle to richen the fuel mixture, and the speed relay rev limiter, and the wire harness that goes from it to the shock tower cross member in the engine compartment and the car runs great. It will be more reliable without the 25 year old relays and prehistoric lambda emission control devices that are on CIS.

When changing to EFI all that stuff is removed, and CIS doesn't need it either.

CIS is all mechanical and needs nothing more than around 97psi fuel pressure.

Jim, thanks for chiming in. It's been a couple years since I played with the idea of deleting all the lambda crap. I currenly run open-loop by simply unplugging the O2 sensor and letting the freq valve lock into whatever fixed duty cycle it is (I can't remember, but it doesn't matter).

I do know that when I unplugged the freq valve in addition to the O2 sensor, she ran really really lean if I recall and I wasn't able to compensate enough with adjusting the mixture control screw - so just went back to letting the freq valve buzz happily away. Back then you did a great job of explaining how the freq valve interacts between the upper and lower chambers of the fuel head (or something like that, again it's been awhile).

Hi Mark, the mixture screw is not going to do it.

lowering the bottom differential chamber pressure with the pulse valve returning fuel to the tank lowers the diaphram in the fuel head which lets more fuel flow into the orifice in the top chamber and that richens the mixture.
you turn in the 6 seperate spring tension screws in the top of the fuel head to do the same thing mechanically and then leave it.
you have to do the injector flow test with 6 little bottles like has been posted here to do that accurately between all injectors.

to show the lambda box is not needed on an '86-'89 reach under the seat and unplug the big multi pin prehistoric harness plug from it and you will see that the motor runs just the same without it...

only unplugging the oxygen sensor may work well enough on your car and is simpler if you think the AFR's are acceptable at high rpms and boost so just leave it that way if that works good.

Cool. I've been meaning to flow check (and adjust if needed) the injectors anyway, so this would give me a good excuse to rip out the lambda box entirely.
Or just leave it to your point; my car runs well and AFR's are where they need to be with just the O2 unplugged. I just don't like the idea of waiting for the freq valve to eventually die and would rather have it out of there entirely.

And oh....this would also entise me to remove the front seat and go after that damn speed rev limiter relay which I believe is starting to give me sporadic fuel pump running issues.

I used to think the speed relay had to be there because the fuel pumps stop if you disconnect the multi pin plug from it or just disconnect the brown ground wire or the white wire in the multipin plug on it while leaving the rest in place... but, a friend of mine with an '87 930 removed everything under the driver seat including the whole wire harness that goes from all that stuff and then down along side the driver side longitudinal, then under the rear carpeting through to the engine compartment and ends at the multipin plug on the rear shock tower cross member and his fuel pumps run fine without any of it.

I guess having that harness in place creates a ground loop or whatever you call it that makes it so the speed relay has to be hooked up for the punps to run. I was real surprised to hear his fuel pumps run with the ignition on and white overboost wire grounded without any of the crap under the seat or that harness in place.

All the lambda stuff under the seat is an afterthought. 930''s before 1986 had none of it so it appears removing the harness and all the stuff under the seat sort of backdates part of the engine wiring safely.

The 2 CIS warm up devices get their heater element 12 volts from the rear fuel pump relay so it appears they are independent of the relays and ECU under the driver seat but I don't know which harness their 12volt supply wire travels through - the one on the shock tower cross member behind the air flow meter or the other one that goes to the rear relay panel. He switched to EFI so the WUR and AAV are no longer.

I don't know... you can't see electricity unless it sparks or arcs so whats going on with it is usually a partial mystery.

Further, one other possibility is to use a different driver in-place of the Lambda computer.

This can be accomplished using a Split Second Timing -- Additional Injector Controller.

With this you can lock the Frequency Valve at a 50% duty cycle which is basically what unplugging the O2 dose with the Lambda computer.

With this you can also use the AIC to provide additional tuning ability such that you can better tailor your Air Fuel Ratios along the RPM curve by load (manifold vacuum). You would also be able to make for acceleration enrichment. Not to be confused with increasing gross fuel delivery on boost.

There is a thread here somewhere where the owner even felt he was able to increase gross fuel delivery by manipulating the Lambda / Frequency Valve with the AIC.

Such an AIC has two channels and the other can be used for some fun things like turning on a shift light or ruining an additional frequency valve to manipulate Control Pressure for further tuning potential but that is another story.

What the AIC will not do it act in place of the Lambda computer as an emission's device at idle and cruse.

Again, it would probably be easyer to send you Fuel Distribuitor out to FlowTech to be refreshed, possably adjusted for increased gross fuel delivery potental if you are going for big HP, and modification to remove the Lambda circut so it operats like a non Lambda / early euro fuel dist.

Gone.

Does the frequency valve require a computer?
A computer was not included with the engine I bought.

Can I still just set the idle mixture where and go?

I'm trying to research "Split Second Timing -- Additional Injector Controller" because my 930 engine did not include a Lamda computer when I bought it.

Any helpful advice will be appreciated. I have the local Porsche club guys coming over March 19th to install the engine with me and I hope to have all the necessary parts by then.

Have you verified that the engine you bought has the original un-modified fuel head?
If so you can simply swap it for a Euro head. I'm just south of you and glad to help with some of the questions you might have (see the 930 powered SC in my signature line). Give me a call tomorrow if you like.

I've always assumed that the answer to that was yes, but reading some of the comments from Jim make me wonder. I can't see how a valve can oscilate at any frequency without some sort of controller involved. But hey, maybe all a person has to do is apply 12 volts to it and it will happily buzz in its default or open loop mode. If that's the case, then yes you can simply tune the mixture and idle speed around it and not worry about obtaining a computer.

I'm told it's a completely stock '87 930 engine without any modifications, and it looks like that may be true. If anything it's dirtier than I expected, but I'll deal with that later.

Hmmm, I will start searching for a Euro head.
Are there specified year models of the Euro head that should be used?

I'm looking at the 930 engine before install and wondering about the "Frequency valve" question.

Should I just buy what belongs on the other side of this plug?

Can someone show me a picture of it?
I'll show you my pic in a minute.

Here's my sign...
 

That whole deal plugs into a harness that runs to under the drivers seat. I think if you review this thread you have several options besides trying to find all that stuff for your car.