Proper timing and EGT at cruise
 

Keep getting into 1200 degrees at cruising speeds. Not sure whats going on. I have closed loop working good so AFRs are at about 14.7, I might need to go a little leaner considering I am running E85. My timing in the area is about 45-48 advance, seems a little too much?

it is. your map should be maxed at ~40° and that's in the 20kPa area where you never hit. unless you're running like 16.0:1 in cruise.

What's good timing and afr for crushing? I end up being pretty high up in rpm at 65 because of my rear end.

You can run a ton of timing in cruise, its really something you have to tune by feel.

If you lean it out a lot youll have to give it a lot of timing to keep it smooth. Youre not going to hurt it, its under very little load.

Ive seen people lean way out to 17.x:1 in cruise in the name of mileage. Some say that you actually get better mileage by not running quite that lean, but Im not sure. Id image it depends a lot on the engine and atomization.

I see. I went to about 48 degrees and the car started to back fire a ton. Thinking 15.5-16 afr is about the tops I should be running. I see that 45 degrees is where tuner studio shows timing maxed out on the dash board gauge.

backfiring = too much fuel.

in cruise, the more you lean it out, the more timing you have to add.


i know hustler played with mpg and cruise a lot and found he made better mpg with a fatter afr and certain timing. something like that.

Theres not much point in running more than you need. Start down at 30 degrees and advance it until it stops bucking.

What should I start with first afr or timing?

Are you running 100% E85? If so you need an A/F ratio somewhere in the high 9's. If you're running a mix, there's tables/calculators out there that will tell you what A/F you should run between 9.x and 14.7

Yeah I run straight e85 but lc1 is just reading lambda, so when I see 14.7 it's actually at 9.76. So I tune like I am tuning gas but all the numbers are changed automatically. I hope this makes sense

Hey Taras (this is Kent) IMO get your fueling right, then deal with timing afterwards. As you pass stoichiometric combustion you should see your EGTs drop.

This is for my stock 1994.
https://www.miataturbo.net/attachmen...1&d=1342138297
I found that more spark angle and leaner fuel required an increase in TPS to maintain speed and ultimately and increase in PW. I played with this from Dallas to Houston 3 times, this is the end result. 27-29mpg at 79mph with a 5-speed/4.10 and a motor that's seen a ton of detonation.

This is also an 89-octane tune, lol.

thanks for posting that.

Geez you run 89 craptane at 10 psi?

Naturally aspirated daily driver. I'll do a 91-tune when the VVT swap goes down later this year. Maybe 93 tune and pull 3* for Oklahoma racing for the day my daily lives the life it always wanted as a PTE racecar.

Green Glory hole runs 93 but I tuned on ~92 octane, lol. I mixed a bit between the two grades because I had severe paranoia issues back then, lol.

Here is my cruise dash for you newbs so you can hopefully put two and two together. I should not that I also used my phone as a level when road-tuning cruise to make sure I was on level ground whilst using cruise control (taped to the passenger door, lol) .
https://www.miataturbo.net/attachmen...1&d=1342139223
I managed to narrow down my tune to this level and about 1-point leaner with more spark angle as two really close sets of values that worked. I then looked at the cruise logs when I got home and made the decision to go richer with less spark angle due to a miniscule decrease in PW. I was very surprised to see maximum efficiency at such a rich mixture, contrary to what the Hondata hyper-mile guys do at 19:1 or so. I drove down the first time at 16.8:1 and scored a miserable 23mpg, lol. I've tried to do this on a Mustang and Dyno Dynamics but we can't consistently dial in ~10-20whp load levels, there is not enough precision that low and the barrel is too heavy.

Brain, please allow ".DASH" extensions upload-able so I can share this file.

Also, with a better, cleaner, EV14 injector, I suspect a significant increase in fuel economy due to the atomization and better flame propogation, rather than these 200k squirters on a bad engine that I'm giving away when removed. I really wanted to work on fuel economy tuning with this engine; I'm currently very unhappy with my results. I expected to be around 32mpg with this set-up but I'm going to lower my goal and hopefully get that with the 10:1 VVT engine.

Here's an awesome article that's light-years ahead of what we're doing, but it describes ideal combustion.
http://www.theoldone.com/articles/Ho...oft_Head_3.jpg

There are a few things that are specific to my setup. Like compression ratio. As i understand the lower the compression the more timing i need to use. And i am running E85 so my timing and fuel would be a bit different.

Very nice tuning hustler.

Propsies