Hi all,

I have been refining the map on my RX and would be very keen to get input on my target AFR table and I also have a quick question basically I am really struggling to get my P3 row near my target after (it is currently in the low 12s).

So I wondered is this just the nature of overrun afr's or should I keep pulling fuel out of my map?

Thanks
Daniel

 

Yes you can keep pulling fuel out of those cells that you want to see leaner afr. Start datalogging as you are driving in those cells and stop the datalog before you let off the gas. you have the stock primary injectors?

 

Post a log. It's possible for you to hit the minimum injector pulsewidth in that load point. If the parameter "Advance InjFrPr" flatlines, anywhere between about 2.2 and 3 milliseconds, you've hit minimum. That's just a limitation of the PFC.

Overall, your targets look fine. You're trying to steadily richen it with boost while attempting to keep it steady with rpm, getting down into the 10s at heavy loads. That works; it's a safe way to go. Regarding P9-P15, under about 3500 (maybe 4000rpm), well that area is somewhat open to debate. You can run it leaner than that for better fuel economy. How lean and in what areas is a little complicated. Basically, if you had exhaust temperature probes you could get better handle on it. New cars have very sophisticated logic and feedback to determine when to go in and out of enrichment during transients.

What you'll find is that you will be on the highway in 5th gear, giving partial throttle if you get on a grade/hill, and now you're 12:1 AFR with the pedal 1/8 down. There's nothing seriously wrong with that in this case but it does waste fuel and theoretically could increase carbon deposits. Don't worry about that so much right now though. Focus on a safe tune with good fuel economy in steady-state conditions.

 

Sorry my reply is late, I completely forgot about posting this quesiton!

Thankyou for your input so far, I will upload some logs in the near future as I am away at university (college) at the moment.

I would be suprised if I was at the lower limit of my injectors as they are the origional factory 550's, but it is true their opening ms are getting down towards the 2ms range at this point in my map...

Maybe my engine is simply not pulling the amount of vaccumm it used to, I think I shall try to get a compression test arranged to see if it is low.

Thanks
Daniel

 

I say that most of your cruise area is too rich for best mileage.
If you want to tune cruise for best mileage, your AFRs will be up around 16-17 AFR.
But you would not do it by AFR alone, but what gives you the lowest duty cycle for a smooth constant speed. The same way as tuning idle.

This is when you do not care about emmissions.

That is what the Japanese did with the A6M Zero that fooled the US military in WWII.

 

I had a chance to fiddle with my car over last weekend, I think by chance I may have come accross the problem. I use a malpassi 1:1 rising rate fuel regulator with a base pressure of 36psi. I double checked this and then to be totally thorough I used a small pump to apply some pressure and vaccum to the reguator whilst I monitored fuel pressure.

When pressure is applied to the regulator the fuel pressure raises up 1:1 exactly as it should, however interestingly when vaccum is applied the regulator bottoms out at around 30psi fuel pressure and will not go lower.

Even with the adjuster screw wound all of the way out the regulator will not let the fuel pressure go lower than 30psi, I suspect either my regulator is broken or I have some sort of restriction in my fuel return line. But at least it explains why at high vaccum I am bottoming out my injectors opening time and still being very rich!

 

Imo I would look at other fuel comp. settings. I dont think that is the prob. Normal idle fuel pressure is 28-32 psi. Pressure with the F/P (fuel pump) and GND (ground) diagnosis terminals jumpered should be 36-38 psi.

 

Thanks for trying to help, but I'm not quite sure you followed my previous post.

My base pressure is 38psi, when the engine is running at idle (my p6/p7 rows) the vacume drops this 32ish psi as you would expect. I believe that in high vacuum areas such as the p3/p4 rows the fuel pressure will continue to drop to maintain the 1 to 1 ratio with the manifold pressure.

My regulator seems to be broken, with the adjuster screw turned right out it will not drop below two bar. I cannot remember exactly, but I am confident that when I first installed the regulator turning the adjuster fully out could reducce the pressure to next to nothing - my current thinking is either my regulator has broken or there is a restriction in my return line.

I picked up an adjustable SARD regulator today, I will fit it tomorrow and report back!