The 14.7:1 target is driven by my present need to generate an emissions-compliant fuel map.

Please stop trying to convince me to run leaner than this in cruise for any reason.

 

don't you want to make sure to burn "all of it" fuel?

y8s, i forgot you have an EGT gauge. add 10° to your timing map, brave the cold tomorrow, and see the effects.

 

No. I want to be sure that the catalyst is operating right in that narrow window of oscillating happiness wherein it is most effective at reducing HC, CO and NOx into N2, CO2 and water vapor, thus enabling me to pass an emissions test. A California "Enhanced Area" emissions test, not that weaksauce stuff y'all have out there on the hurricane coast where they're just checking to see that you don't have pure, unrefined crude oil gushing out of the tailpipe.

All other considerations are secondary.

 

My bad Joe, everyone has been talking about efficiency and mpg thats what was on my mind.

 

Best efficiency / power for an AFR of 14.7:1 in the idle and cruise region. WOT and high RPM are open for debate.

In fact, this thread has inspired me to go in and do some tweaking to my AFR table. I've lowered the thresholds at which I start swinging rich to 85 kPa and 4,500 RPM.

So thanks to those who suggested that. I've been fixating only on the cruise region.

 

I want to see less of this ------ry and more people advancing +10* on pump 87 and not hurting engines.

Because throughout this sausage fest we have yet to bring up the fact that Joe is the only one running 50* (or close to it ) in cruise on CA 87 ****.

Maybe its blessed with unicorn semen like Leatherfces' stock shortblock that took 23psi on a large turbo.

I will try this when I get my MS. But not on 87. F that

 

I wasn't suggesting you lean out your mixture, I was suggesting that you'll be in a very large butter zone for just about any timing advance value you want to run.

 

This thread inspired me to do 2 things. 1) double check that the pulley matches the mechanical TDC and 2) add ~10* to almost my entire ignition map. I was too lazy to do any datalogs at the moment, but the butt dyno certainly approves. My map is now very similar to the map Ben posted over in the other thread linked here somewhere with some more added in the cruise regions inspired by Joe. No pinging noticed on our craptastic Albuquerque 86 octane, at least I didn't hear anything, and the plugs still look clean. So, take that for what it's worth.

 

Future generations will recall this day as the moment that enlightenment rained down upon the Miata Kingdom.

Or maybe not.

But I did quite a bit of this on the way home tonight, and nothing has blowed up yet:



I find the injector duty cycle to be of particular interest. Note that I am peaking at 86%, and this is on a bone-stock engine with injectors that were cleaned and flowmatched less than a year ago. That is why piggyback-only fueling with forced induction blows up engines.

 

While you're at it, don't forget to verify the hardware latency setting.

 

ok, 1 other person has done it too

now we need 10 more and for their motors to run like champs for a while doing it

 

I set latency a long time ago. I double checked it while I had the timing light out, but it still looks pretty close.

 

I ran 5-6 psi on my stock injectors. Until about 6k rpm they would hold 11.5afr, over that afr creeped up to about 12.2afr by 7k rpm. Yes at that point i'm guessing they were opened 100% of the time since adding any more to the table did nothing.

 

Joe, you are very concerned about creating an emissions-compliant map, but you don't seem to be considering the effect ignition timing has on NOX emissions. NOX increases as timing is advanced beyond a certain point. The timing that yields best fuel economy will yield pretty high NOX emissions, generally speaking.

 

I'm aware of the contradiction.

Generating a nice, perfect VE table takes time. So right now, that's what I'm doing. When I've got the VE table perfect, I'll save a copy of it and then maybe start experimenting with lean-burn cruise.

By comparison, experimenting with optimum timing for peak torque is an interesting thing to do, and something to which it is obvious that little attention has been paid in the past.

When I need to go in for a smog check, it's an exceedingly simple matter to just yank a bunch of timing out of the spark advance table, and this should not have a significant effect on AFR. I need to have a separate ignition map for emissions testing anyway, as I need it to idle at exactly 10* (they check this) even though this is, by far, sub-optimal for idle stability.

 

Just making sure.

 

All of the cool kids are doing it.

Don't you want to be cool?

 

This guy claims 38mpg+ at cruise using a NBO2 (14.7AFR) primarily by tuning timing: Hydra, 38mpg+, power and smoothness like no other

Unfortunately he doesn't really discuss his methodology or even provide the resulting timing map.

 

Joe could u post up your current Spark map and AFR table?. I live in a hilly area much like you and im weak sauce on timing and stupid rich at anything over 80kpa where i spend up to 2min at a time in an attempt to not blow **** up. Im intrested in seeing where you transition from stoic to richer and how / if timing reflects that. Im a visual person so the pics really help my understanding.

Cheers and thanks for trying this out.

 

Didn't he already post both?




what the hell

is the point

of making a thread about tuning

then not sharing said tuning

ugh