UPDATED! Cyl 2 and 5 lean, This is how I fixed
 

Hello Turbo friends, When I removed one of my heat exchangers and noticed cyl 2 was very white , see pics posted above, then I removed the other heat exchanger cyl 5 the same . This isn't the first time I've experienced this and fixed this problem with success.

I tested the fuel system, removed the fuel line from the injectors at WOT, and got perfect results. OK, I thought, Maybe bad injectors, so I tested the injectors at idle and at 10% and 25 % throttle then WOT and again got perfect results. as they should, they are new.

I talked to Chris at TurboKraft he suggested that I adjust the fuel head-on cly 2 and 5 !. I removed the little caps next to the fuel line and turned it clockwise 22 deg and started the motor, It started fine and idled perfectly. I will drive the car for the next few days ( 70 deg day coming up in the DC YES !) area. I will check my EGT's the best I can using my inferred temp gun, and check my AFR's with my Innovate handheld unit.

In a couple of weeks, I will remove the heat exchangers and check the color of cly 2 and 5 again, From my test drive. it seems to be spot on.

Even a freshly balanced CIS system is not going to ensure even fuel ratio tuning per cylinder as there other factors inherent in the 3.3 / 3.6 CIS design.

Different primary tube lengths make for variations in reversion per cylinder and thus cylinder filling, the pancake intake manifold seems to flow better to the two center cylinders, and the flat 6 design makes for two center cylinders that are just going to run hotter. On top of that air/oil/, fuel cooled motors have less effective cooling systems and naturally run hotter combustion tempshttp://forums.pelicanparts.com/uploa...1615125458.jpg
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Thank you for this contribution. I am excited to see what will come out

I did a write up on this a few years ago. The pancake manifold has shorter center runners which is cyl 2&5. Result is more air to those cylinders causing them to run a touch lean when compared to the others. Pull the exchangers on any 930 any you will typically see this. Enriching the fuel flow to 2&5 will balance the AFRs.

Hi Brian,

Yes sir I did, At the time it was my yellow car with a highly modded 3.3. I wasn't expecting to see the same thing on this mostly stock except for the cat bypass and RUF 0.9 bar spring on this 3.3 965.

What I read from someone was if adding fuel to some ports, it will lean out a little on the other ports. and I'm okay with that. Have you heard of that? Thoughts?

Helio

If assuming that the fuel distributor delivers 100% then taking away from that total to add to cyl 2&5 will decrease the amount left for 1,3,4 & 6. This amount is so small that you can easily compensate for it. Off the top of my head I believe the change to fuel amount was around 5%, but this varies engine to engine. If I recall you did this with the yellow 993tt/Gt2 clone, this should be similar even with Lambda. Once the adjustment is done the Lambda system will lean out all 6 cylinders similarly. Really nice detail, props on doing that!

I hate threads like this.
Now I want to drop my exhaust and check for a lean condition.
How much should you turn the screw clockwise on a 79 fuel head for a 5 % increase if I find an issue?


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It's not really an issue, more an exercise in optimization. The 930 fuel system is well known for being overly rich, this is likely one of the reasons why.

Thank you, That's what I thought, Well said, I'm going to share your words on Rennlist, It will be helpful for the 964 Turbo guys, Some of them will appreciate the knowledge

Lets us know what you find and we will help you on how much fuel you need to add.

I try and tune my cylinders to 2% (matching) or better if I can get there. While the 2/5 thing makes sense I have never seen the signs of them running leaner - and they get a hard time - mostly WOT.
But as Brian says - usually on WUR dump - which is generally on the rich side for most but the upper rev range. And on upper revs only briefly - have to change gear some time.
I am about to retune after a total fuel system rebuild. I try and match 2/5 to the rest.
I guess it will show up more on low/cruise revs.
Alan

Every set of OE exchangers that I have ever removed had this same 2/5 light gray color pattern. Those cylinders were likely not lean but rather the 1/3/4/6 cylinders are rich. I'd say that tuning for an equal AFR on all 6 cylinders would produce more power and allow some tweaking of the timing and boost level as well.

Hello,
It would be nice to have this tuning technique here with pictures.

I will be doing mine this week - just waiting for some parts - fuel pump and filter.
Can take some pics.
But there are some threads on this also. Will be same in 911 forum if not on 930. Tuning the FD is the same for my SC as for 930.
Alan

Disclaimer - we are only random guys on the internet, fuel system tuning should be done by a professional.
There you go, don't want someone getting butt hurt 'cause they screwed this up and burned a piston.

What I am doing - in a day or so, is just balancing the injectors out. This is the process you would go thru if you want to put more fuel in 2&5. Balance them out - then add a bit more flow to 2&5. I run mine all the same - but can post the process if that is what is being asked.
Just installed new filter, now waiting on a pump. My rear pump is lazy - too much pressure differential between the two (5 bar) and too low a fuel flow in total. 1500cc /30 sec.
So I am fitting a 2nd 044 Bosch pump - ie one each front and rear. Then I will tune/balance the FD.
Happy to post that stuff if that is what is wanted. The 'tuning' - AFRs - I do on the track - via the WUR pressures. I have mine so I can adjust it in situ, and have a permanent pressure gauge on the WUR.
Alan

I’m having a little trouble understanding your explanations in English, so if I could get some pictures, it would help me understand. thanks you Alan L ! :)

Hopefully the pics will explain.
When you see the calibration data, the first run is as the fuel head delivered after reassembly.
To recap - my car had been sitting about 6 mths. Been running fine. Would not start - fuel problems. Front 044 pump (near new) had seized. replaced. Week later the new 044 seized. Had small amt of very fine grit on the pump intake screen. Spent some time cleaning swirl pot in tank as best I could without cutting the tank. Very little in there basically and tank interior fine. Install another new 044 pump. Now the injectors are squirting constantly. Metering piston seized in FD. Could not free it - had to split the FD. Maybe a magnet would have pulled it free - it wasn't badly stuck. But now I have to recal the FD.
Check fuel system prior - low flow at FD (1000cc/30 sec.). I had more previously. Check pump pressure differential - 5.5 bar. Too high - spec is between 2-4 bar. Either filter blocked or rear pump substandard. Replace filter. Differential now 5 bar. Pump must be suspect. Replace with another new 044 - now got 044 front and rear. Differential now 2.5 bar. Looking better. Check flow - 1700cc/30 sec. Enough. Now set system pressure. 6.5Bar +/-. Now ready to do injector calibration.
I concentrated on #6 which was low, first, then went to #1. You could do both at same time. Then I convinced myself to crack open #2 for a small adjustment at the end.
You need a weird allen key size (9/64) to open the adjuster port - remove the black sealing cap. You use your idle adjust allen key (3mm) to tweek the adjuster port.
I am for even number from 1-6 - but you could easily bump 2&5 up by say 5% by this process. Unwind the adjuster port to reduce flow at that injector and vice versa.
I had explanaotory captions on the pics - which didn't come out.
#1 you need plenty of space
#2 checking the pump differential press - I just took the pic since I was in there.
#3 measuring flow rate
#4 collecting the injector flow
#5 I measure mine in a measuring cylinder
#6 - getting ready to adjust - remove the cap over the adjuster port
#7 doing an adjustment
I use an outside power source to power the pumps when doing this - jumper leads off a running motor. The pumps suck a lot of power.
Alanhttp://forums.pelicanparts.com/uploa...1615861767.jpg
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Forgot to post calibration figures.
Alanhttp://forums.pelicanparts.com/uploa...1615862624.jpg

Alan, excellent post. Two questions - did you by any chance check your flow with the air plate pushed down to simulate something other than idle? Always been curious to see if it’s any different.

Other thing is do you know what names/sizes of the adapters you used at the rear pump to fit the gauge temporarily and check your pump differentials? I want to do that but don’t know what to ask for at the parts counter.

Thanks!

To check the flow, you need the injectors shut. To compare apples with apples - factory values/specs. Any flow thru the injectors will detract from the flow values (unles you collect them as well). This is the port for the return line to the tank. Anything not going to the tank (injectors) will screw the number.
I have measured the flow at the injectors at WOT and get just over 1000cc/30 sec.
So at factory value of 1500/30 sec - minimum, you have 500 cc/30 sec returning to tank.
My differential pressure thing is a home made cobbled thing - and I have the same issue as per fittings.
But the critical fitting is the one that hooks on to the fuel fitting at the end of the front pump line. - Mine came off the discarded fuel filter. It has a couple of fittings screwed in it - as it comes out of the box. One of them happens to be what you want.
Then I just cobbled what brass fittings I had that would fit.
If you grab the filter fitting (ball socket type fitting with a thread on the other end) (can post a pic), and take your pressure gauge - then the shop should be able to assemble enough bits for you to Tee the gauge in.
Regards
Alan