Staffan

After installing new headers the boost has increased slightly and the AFR is high above 0.9 bar, about 12.2 - 12.8, I would like to be closer to 12.0 (I have a graph somewhere).

I tried to increase the co level at idle and disconnect the o2 sensor, but I get the same result.

Is there anything else I could try?
I know about the fuel head mod and adjustable wur, but I am leaving for Nürburgring in a week, don't have the time (and the money) to anything major.

Remember reading about improving the movement of the "air flap", is this something that would help?

dholling13

The allen head screw on the fuel head is what I've heard you can adjust to get more fuel.

Staffan

Thanks, that is the co adjustment that I tried.

Can I port the fuel head myself, how hard is it, anyone knows?

NineMeister

We tend to leave the stock fuel system alone and add a 7th injector under electronic control, however given your time constraint you could consider reducing the control pressure of the warm up regulator, but the downside is that it will make the car run richer under all conditions.

To do this involves knocking the brass post down into the WUR, a little at a time until you get it right. If you go too far, drill and tap a hole in it, fit a stud and use a nut/washer to pull it back out again. Do a search on Rennlist for WUR mods and I'm sure you will find a lot more info. Please understand that this is not really a DIY mod, you are messing with a £900 part and you need to be aware of the consequences if you cannot get it right!

PorschePhD

Steffan,
Did you leave the 02 unplugged after the CO reset? If not try that. The system will try to pull back if you plug it in.

The fuel head mod is the correct fix. I do not recommend running a wet injector in a dry intakes that flows like a lump of coal to begin with. Miller had a sytem like this years ago and the end result is 2 and 5 were staturated and made the AFR look ok while 6 was lean and tupically 3. The result was never good.

The WUR adjustment is also a bandaide but works. As Colin recommend unless you know what you are doing a little sometimes can be too much and you are buying a new WUR.

jeff91C2T

The frequency valve goes to 50% duty cycle when unplugged or on full throttle. In this case I'm not sure I understand how having it unplugged would effect the readings under full load. As far as getting more fuel with the mixture screw. I was never able to see a measurable effect on the dyno (that would solve the problem).

I did the WUR mod and tapped the brass insert down to get more on boost enrichment (this makes the movement of the air flap easier). This is the same detail Porsche did with the the 3.6 Turbo. You can tap it down yourself or find a 3.6 WUR. As Colin mentions, the tapping down part is very touchy and an iterative approach. You don't want to go to far as these WUR's are not as easy to tap back the other direction. All in all it's an easy change, just be careful. You'll need a CIS fuel pressure gauge. You could do this in an evening. If you want more details...shoot me a PM.

Another source for getting the fuel head mod is at;

http://specialtauto.com/porsche-parts/index.html

They can also rebuild your WUR as well....in case you it gets damaged while modding

Staffan

Thanks Colin, I will investigare and do some thinking about the WUR mod, but I guess that would give me problems during smog inspection. My car need to show a 0.98 - 1.02 lambda (perhaps I coudl talk myself out of 0.96) at idle and 2500 rpm to pass the smog inspection, that's a show stopper for a WUR mod right?

Staffan

Stephen, I unplugged the o2 sensor and adjusted the co allen bolt so that the idle AFR was about 13.6, I left the o2 sensor out. Should I try a richer idle?
I know you recommend a 3% co at idle and leave the o2 sensor out, do you know what AFR that corresponds to?

Staffan

Thanks Jeff, I'll send you a PM for sure.
I guess my concerns are:
1. Smog inspection
2. Time, or possibility to return this brass plug if something goes wrong, leaving for Germany next sunday.

dholling13

Hmmmm.

Staffan, I would recommend dyno tuning your car. I have a high flow s turbo, b&b headers, and pretty close to the same set up which you are running and my afr's are 11.6 - 1 at 6k rpm's but far higher at lower rpm's. Check out my dyna pack sheet. The purple line is the one to look at.

PorschePhD

Normally about 13-13.5. The other thing you have to do is unhook the air injection at the same time. Otherwise the CO will not be accurate at idle. You really should not need this standard if you have a good AFR gauge. What is it? There is a possiablity it is not calibrated. You should base line it to something else that is a "known" good unit.

If you are too close to time at the track to do any tuning/checking simply fillup with some 100 octane. 12.6 on 100 is fine!

PorschePhD

FWIW I can tell you is this is not someone we sell the mod too. I am not sure what they are doing but myself and my tech who builds these came up with the idea by changing halves until we got what we wanted. We then loaded that and CNC the ports. Anyone else claming to do what we do I highly find that unlikely.

Jean

Stephen

I am far from understanding what is being done to the fuel head but my previous SY 964 3.6Turbo that was modified in the UK in 2002, had the fuel head modified for increased 40% flow (according to the invoice).. Are we talking about different methods being used nowadays?

Jean

nathanUK '81 930 G50

Who modded the head Jean ?

PorschePhD

Not knowing how they modified your fuel head I really couldn't answer your question. There are only a few poeple that work on the heads to begin with. What we did I know had not been done up to that point.