Stephencs601

This Saturday, I will be checking things out by Lex. We are doing are own tech type day.Thanks for all the heads up.

mark kibort

that is the worst possible mixture range. you are more prone to detonation there than ANYWHERE in the fuel mixuture level. 14.7 is worst. any side of that, even leaner is better( but at the cost of power, even more power than the rich side of stoich). however, the 928s are set in this range by the factory, and my 84 showed similar hp, and the mixture after i put on a regulator put the mixture a little richer (13.8), so it must have been leaner before, i would imagine. then, with a turn of the regulator, it got down to the rich range.

if the WOT switch didnt work, the mixture would be much leaner.


mk

hacker-pschorr

So you don't know for sure what the mixture was before the adj regulator?

I have an adj regulator on my 81 right now. My fuel pressure is 100% stock as it was with the factory units (until the boost kicks in). I "had" a lean issue with my car so I added the adj regulator. It ended up not being my fuel pressure so I turned it back down once I fixed the problem.

So for the fourth time in this thread - without a fuel pressure gauge before / during and after, this is all 100% guess work.

Stephencs601

We are going to check everything on Saturday. I will not have the regulator for a week or more, so I will be checking everything prior. Hopefully it is something minor, such as the regulator. I will test the WOT and Temp II along with other items.

mark kibort

I dont know for sure, but 2 RRFR's set up for 15% more than stock pressure, equated to 13.8. i would imagine, mid 14s would not be unusual for an 84. Plus, ive seen a few S4s with a similar values for a stock set up.

bottomline, the engine stock is so underrated that it probably is not dangerous, unless you have a pinging issue.

mk

Stephencs601

No pinging at all. I must say though, at 50mph, when I go to WOT this car is a rocket. It actually leaps when it up shifts. Love that feeling.

hacker-pschorr

We just finished the Sharks In Titletown Dyno Day.

Rod Kubis(69gaugeman) put his stock 83 on the dyno, found it odd the air / fuel was 14.7 through the entire run. We discovered the WOT switch was not working.

We will post the dyno results later in a different thread.

Z

Below is the air/fuel mixture from Rod's car on Saturday. The blue line is where the WOT wasn't working, and the red line is a few minutes later, after the WOT switch was adjusted so that it would work. No other changes were made to anything other than getting the WOT switch working.

Stephencs601

Basically, I need to look at my WOT to see if it is functioning. That seems to make sense. Now finding the time to do it is another story.

mark kibort

great graph.

this makes me doubt the AIM1 gauge, other than just for major issues. without the WOT on my 84 5 liter euro, the mixture went WAY lean, in the 17s according to the meter. however it was the 5 liter and it could have been leaner due to the larger displacement.

however this kind of points to the WOT switch as you said in the beginning.

hope thats it! should be an EASY check

Mk

docmirror

<edit> :Oops, L-jet, disregard CIS adjustment..... Sorry
Okay, some CIS stuff. The CIS will be set from the factory for a nice lean, 14.3-14.5 to pass emissions. This is normal. The WOT switch is used as enrichment becuase you don't check emissions at WOT. The extra fuel controls detonation as Mark mentions.

If you are running normal (non-dyno) the AF ratio should be around that 14.5 area. This will keep the cats from getting too hot. It also gets the best fuel economy because the internal cylider pressures are the highest.

Now, if you want to play with it a bit, and have a long 3mm allen, there is an adjustment. I would NOT recommend this without having a set of CIS gauges and a sniffer. Some year CIS distributors have an anti-tamper cover over the adjustment, I don't know if the 928 or which year if any have the anti-tamper cover. Between the air damper plate, and the distributor in the valley casting, there is a little screw-plug with a screwdriver slot in it. If you remove the scew-plug, you can use a 3mm allen to change the mixture of the CIS head.

Again, without CIS pressure gauges, and a sniffer, you're guessing on the setting and it is VERY sensitive. with the car in question I would not be making any adjustments. Check the control and working fuel pressures first, but it seems to be right on the money AF ratio wise at standard driving conditions. The WOT switch is probably not working, and that has to be resolved first, then investigate if there is a lean running condition once everything is setup right.

mark kibort

Doc, I think both of the cars in question here are Ljet. (ie '81 and the 83 that enzo tested)
mk