What main Jets?

[240260280z]

presently

40DCOE151

125 main

170 corrector

F11 emulsion

30mm Choke

4,000 RPM 11.5 Air/Fuel

6,000 RPM 10.5 Air/Fuel

240z L24 270 cam

I am thinking that a switch to 115 may lean it towards 12.5 at 4k and at the same time tip the the high end back at 6k. Any suggestions?

Edited September 16, 2012 by Blue

[Lazeum]

Rich at high rpm could very be your chokes being undersized also but 11.5:1 at 4000 is too rich, I would go down to 115 since you have a lot a fuel to restrict to get back to proper AFR at WOT.

here is a graph with my previous setup with F54/N42, Schneider stg 2 cam & 40DCOE-18. You can see the difference in AFR between mains.

Edited September 16, 2012 by Lazeum

[Zedyone_kenobi]

I tend to agree with Lazum. I think you should try 115 or 120. I have some 120's if you would like to try.

[240260280z]

Thanks Lazeum. That is the data I wanted to see. 140 to 130 raised your AFR by 1 point. I should do the same and try a 115.

Stephen, I'll accept your offer and PM my contact info.

I bought 55F9's and 60F9's based on your data. Mine ran rich and richer. But I ran into 3 problems (Murphy's Law) while on the road testing so I'll go again next weekend and post the data. I just put the 175 fuel needles in and the Solex FPR.

THANKS!

[Zedyone_kenobi]

Yeah, I figured out that tuning for steady state cruise in 4th gear is not really the best way to get the idle circuit to work. Shooting for 12.5:1 at 55 mph in 4th gear meant I was pig rich the second I wanted to accelerate in 4th gear while still in the idle circuit.

The thing is I was reading around on some tuning forums in the Subaru community I am part of. During steady state cruise the engine is under next to no load. Running at 14.5 to 15:1 is fine in the mid range rpm bands if the engine is under next to no load. I would not want to be there at top end. But running right at stoich. while not accelerating is probably a GOOD thing.

I put 50F9 jets back in mine. But now that I have gone to 32mm chokes, I will probably need to go to 55F9's if the choke has any effect on the progression circuit.

[Lazeum]

For what is worth, with the curves shown above, I was running around 14:1 to 14.5:1 at crusing speeds. I was running 45f9 if I'm not mistaken (or 50f9 if not 45f9)

[LeonV]

On a non-catalyzed vehicle, run it as lean as possible without misfire at cruise for optimal fuel mileage and least emissions. There is no good reason to aim for a rich AFR at cruise, or at idle for that matter. WOT is another story, 12.5-13:1 is a good place to be.

I'd go with the Subaru guys' recommendation if a catalytic converter were involved, which of course is not the case for a 240Z.

[Lazeum]

Usually on our cars with no programmable ignition (as far as I'm concerned, it won't be true anymore in some months ) or without depression in the dizzy, timing is way to low to provide good burn at low loads. To compensate for the deficiency, AFR needs to be richer than 14.7.

Catalysis reaction only occurs at 14.7:1 AFR, that's why car with catalytic converter have always an O2 sensor; it is to allow the ECU to run in close loop mode to regular AFR to be as close as possible to 14.7 ratio.

Running leaner than 14.7 on our car is creating more NOx & CO2 but less HC & CO but to a small step which makes it not so interesting. See the graph below.

Edited September 17, 2012 by Lazeum

[LeonV]

Usually on our cars with no programmable ignition (as far as I'm concerned, it won't be true anymore in some months ) or without depression in the dizzy, timing is way to low to provide good burn at low loads. To compensate for the deficiency, AFR needs to be richer than 14.7.

I don't have that problem!

Catalysis reaction only occurs at 14.7:1 AFR, that's why car with catalytic converter have always an O2 sensor; it is to allow the ECU to run in close loop mode to regular AFR to be as close as possible to 14.7 ratio.

Running leaner than 14.7 on our car is creating more NOx & CO2 but less HC & CO but to a small step which makes it not so interesting. See the graph below.

[ATTACH=CONFIG]56363[/ATTACH]

Let's compare 12.5 and 17 AFR on the chart you posted:

• CO is way lower
  
• HC is slightly lower
  
• NOx is about even
  
• CO2 is about even
  

Comparing running 14.5 AFR with 17AFR:

• CO is slightly lower
  
• HC is slightly lower
  
• NOx is slightly higher
  
• CO2 is slightly lower
  

Plus, you get an additional benefit of higher mpg.

You're right about requiring more spark timing with leaner mixtures and lighter loads, but that is why I recommended to run as lean as possible without misfire (or losing power). Certain combinations will be able to attain leaner mixtures than others, depending on mixture distribution, spark timing, combustion chamber design, etc.

[Lazeum]

I'm wondering if I haven't heard stuff about extr lean AFR to run modern engine. I think direct injection fuel engine are working also with those kind of AFR. I'll have to look for some info but it would make sense.

For your Edis system, I know that too well You've shared this picture with me already and I'm going to follow your steps towards EDIS & Megajolt also

[LeonV]

I'm wondering if I haven't heard stuff about extr lean AFR to run modern engine. I think direct injection fuel engine are working also with those kind of AFR. I'll have to look for some info but it would make sense.

DI engines can run very lean but the idea has been around for a long time, e.g. Honda's CVCC!

For your Edis system, I know that too well You've shared this picture with me already and I'm going to follow your steps towards EDIS & Megajolt also

Good choice! MJ is great, just finished a 1000 mile road trip to JCCS and back. My speedo doesn't work for now, hence I don't have a working odometer to track mpg. However, it is definitely improved and I'm somewhere in the 20-30 mpg range . Once I deal with the speedo, I'll have a better idea.

From memory, I'm running 42deg advance at cruise but my AFR is way too rich (about 11.5:1). I'm attending a DCOE tuning day here in Northern CA (that conedodger has organized) in October. I'll be aiming for far leaner cruise while keeping transition tractable and WOT around 13:1.

Let me know if you have any questions about EDIS and MJLJ, I'm happy to answer. I've got more details posted in my thread at hybridz.org.

Edited September 17, 2012 by LeonV

[Lazeum]

I won't go off topic then on this post. I'll go on HBZ if I've got questions

Looking forward for the tach to work since this is the little unknow for now (I took the tach adaptor with my kit)