D15B with Neptune RTP
 

Hey guys I got my Neptune setup about 2 weeks ago and am on my second tank. The first LEAN burn attempt was 38mpg. Not as good as Ive seen people getting. my 2nd tank looks to getting a lot better. Im at 240 miles and the gas gauge is at almost half tank. Is there someone here that can read my tune and give me some pointers? and also what should i change? like Disable Closed Loop, fan control in gauge at 180 above 50mph ext.... any thoughts are greatly appreciated. Thanks

It's been a while know and still not very happy with the lean burn tune. Best attempt is 43 mpg and I know there's people getting way better results. Any tips would help out slot. Thanks

What AFR are you running? How fast do you travel? Do you have an instantanious MPG display, if so what are your typical readings? What other mods do you have to your car? I assume you are running a wideband, which one?
Give some more details and I will help where I can.

I'm running around a 17:1 AFR, driving 50-55mph with aeromods and very LRR tires. My instant readings are in the mid seventies with this set up.

I have a innovate lc-1 running at 19.5 afr ( no b.s. ) while cursing 45-55. I have a jdm d15 single stage vtec with a Skunk2 intake manifold tubular header and 2.5 exhaust. Lowered on blox coil over sleeves and agx shocks. No ac no ps other than that it's stock. And of corse the Neptune rtp. I don't have a mpg gauge although that's on the list when money allows.

Thanks for the help.

Don't worry, I don't believe you are trying to trick me on the AFR.
One thing you gotta consider with running lean is that you need to reduce your load. Big wings, wide sticky tires and the like will have a large negative impact. The more power you need to make to propell your car down the road, then the more fuel you need. That's why I can do so good at only a 17:1 AFR.
Even though I see mid seventies while cruising, I can average just above 50mpg on my regular commute, so you also need to consider the way your drive, the route you drive, etc...

The key ingrediant will be the Instant MPG Gauge. Without it, you will never get your tune right for best mpg while lean. Right now you are just guessing at all of your parameters and they can not even be educated guesses because there is not much of a knowlege base for running this lean. I'd suggest you get an MPGuino imediatly, back down on your AFR and focus on learning how to get a more convervative AFR. You are more likely to suceed this way and learn how to make a tune that works will with lean AFR's.
If your able to tweek your injector pulse widths and timing on the fly, you can just monitor an instant mpg reading and you will know exactly what parameters are needed.

Hope this helps!

Oh yea, I have to add that at 45mph, I'm at 16.5:1 and getting high seventies or low eighties and at 35mph, I'm at 16:1 AFR and getting low nineties. Leaner isn't always better, you really need to expirement and think outside of the box.

Great point I'll report back after I get the mpgunio.

exhaust pipe diameter is too large
 

I wouldn't split hairs on exahust pipe size. While I'm sure it could be optimized for FE, I don't expect that to be the need in this case. I have an oversized exhaust pipe as well. I like to use my car for more than just good FE. Even when I go drag racing, I am still getting great FE :) I want my cake, with frosting and I want to eat it too! Lean Burn is the frosting :D

Yeah thanks for the info guys will see what my instant mpg is when get my MPGuino. I'll be able to tune it better from there. Where are y'all mounting it at? I seen a pretty slick setup under and behind the tack. Dose any one know who did that?

How lean can we go before we start to burn valves?

Well there's a guy on d-series.org with a del sol that's getting over 70 mpg and his tune is over 22 afr with no ill effect. I figured I was safe at 19 with timing advanced to 45 degrees. So fare I've gotten over 2000 miles on this setup and all is good. (knock on wood)

lean condition results in cooler combustion temps
 

velocity should be no more than 300 fps at
 

What I have read is 13.2:1 produces the most torque and "highest" EGT's.
But I don't know if that is highest EGTs of all A/F ratios or the highest you get using normal ratios such as 12:1 through 15:1.

I googles searced for quite a while last night and could not find a magic number for the exhaust valve burning air:fuel.
I have burned exhaust valves before I had a car where the IAT sensor was reading 300'F on a normal 70'F day, caused it a nasty lean condition and burned the valves on every cylinder.
Never thought to look for peak NOx to find the highest EGT mixture. I bet that will work.
If I find anything I will post it here. Burning out your exhaust valves to save gas isn't going to save us any money.

An expensive alternative could be to get Sodium core inconel 625 exhaust valves. They are burn proof. I know you can get them for pretty much any chevy V8 gas engine ever made, not sure about getting them for 4 cylinders.

Computerized Engine Controls - Google Books
What air fuel ratio burns valves?
What air fuel ratio causes the most NOx to form?
Looks like just short of 16:1 is your peak for NOx production and likely the peak for combustion flame temperature.
But once you pass 16:1 NOx levels start to drop quickly. 16.5:1 looks about as NOx-ious as 14.7:1.

Oil Pan, we are only use these lean conditions under light loads. In your case, you were accelerating under heavy loads while lean, that's why you burned valves.
At some point, I would like to put a EGT gauge in my car to confirm a drop in combustion tempature.

Yes my car was running lean all the time.
You can score a new EGT off ebay for cheap like I did. Or get a used one real cheap if you want to get creative.

retarded ign timing
 

..."I have burned exhaust valves before I had a car where the IAT sensor was reading 300'F on a normal 70'F day, caused it a nasty lean condition and burned the valves on every cylinder."...

FALSEly hi IAT values will cause
retarded Ignition timing
which will change the timing of Peak Combustion Pressure to
After 14 degrees atdc ...
so part of the charge burns in the exhaust
not in the combustion chamber

contributing to
burnt exhaust valves

The car had a mechanical ignition system timing with mechanical and vacuum advances.

Thanks for all the info guys. But ahh could we happen to keep this on topic?

Ok I'm back and have the mpguino calibrated and reading dead on. Tygen1 is there any way I could get your map to take a look at it?

Don't have a map. I adjust it on the fly. Every combo will be diferent. To give you some idea, I run about a 17/1 afr at anything less than 50 LOD. You can be more aggressive than that, but it should be a good place to start.

Ok what was your timing set at? Or did you just adjust the fuel trim?