Thread: Tuning for Gas Mileage

Ah that makes sense, I did notice a much smoother ride today with a leaner mixture. I'm hoping to get some power back from being 10 A/F at WOT to 12 A/F at WOT.




Sorry I got of track a bit, but yes at cruising speeds it's all HP and not torque. I forgot to mention, from my logs my Throttle was at .8v (with .36 min, and 4v max). RPM's logged were around 3200 at 70-75 mph.

I guess this would be a good place to share my experiences in this department.

I made a trip from socal to az when I first bought my se-r.

I checked timing before the trip and didnt realize until months later that i had confused the timing notches on the crank pulley. My timing was wayyyyyyy off.

I thought the 12-15 mark ( where the timing should be set at) was the ZERO mark. So I set the timing according to that. It actaully ran fine, I did not notice any performance issues.

Also had the tires filled to 45 psi just for the mpgs.

I made it to the AZ border from Thousand oaks Ca on a little over half a tank
=
43 mpg!

**** your damn hybrid!!!

You also don't want to lean out your idle too much. You want that around stoic (14.7:1, maybe a tiny bit leaner) and about stock timing. Otherwise you'll be putting a lot of extra heat into your exhaust and coolant if you idle for long periods.

If you're going to be doing your own tuning, consider an EGT gauge. It is very helpful for tuning your timing maps.

Also, low RPMs doesn't always equal high MPG. If you look at OEM highly efficient cars (such as the CRX HF) you'll notice that cruise is geared so the RPMs are near torque peak. It basically comes down to what BenFenner was saying, the more power you are making with the least amount of throttle input the better your MPG will be.

Not having enough timing is not good either, I agree. My timing on my old motor was very low because of the back knock sensor. But even after I increased the timing and replaced the knock sensor, it still got the same MPG.

My Alignment was off by 1", that has been my bad MPG culprit since day off. Besides the sludgy motor haha.

I'm going to reduce the A/F at idle, It's idling at 1k and I don't really like that . Plus ontop of that A/F are around 15.3 at idle, not really all that much higher.

What I found interesting is, there is a dip in the A/F as I'm driving. when throttle is at about 75% it goes way below 12, but at full throttle it goes at 12.5 down to 11.8ish.

ben turned me onto the whole aem o2 feedback fuel table which i feel is really amazing, not only does it work, im not sure if calum has a simular setup on his ecu, but basicly it has a axcess of engine load to engine rpm and basicly its used for specific tuning of off boost driving, but alls you do is highlight a certain rpm to certain engine load and set it at say 15.7 and the ecu will compinsate the fuel to the specific needs of that air fuel ratio, either take out the fuel or add in the fuel to achieve that specific air fuel ratio, which is super easy to target more leaner fuel condition to achieve better gas mileage off boost.

ive been playing around with the aem system alot lately and found that even though a leaner idle is beter for gas mileage, it can mess with your idle, i have found a richer idle seems to be cooler and more stable than a leaner idle, which i like a lean idle, but if a rich idle is going to be more stable that is what i will be going for

also if you have away to target that dip on a log you cna go into that specific engine load at that rpm and adjust it

with a calum ecu your going to have a hard time getting around the closed loop afr. the stock ecu can and will add lots of fuel or pull a lot to achieve 14.7 oscillation.that is part of the reason i went full standalone.

Whats this AEM system? I'll have to check my idle with a little richer mixture, because it automatically resulted to 1k rpm idle, which then moved off my 800 rpm fuel line. I guess that's an easy way to see if the ecu/engine doesn't like being that lean.

As for the dip, I believe that is the weak spot of the boosted SR20's. Because there is a descent timing map dip, I tried to avoid doing anything in that area to avoid unnecessary detonation.



That's true, this is why sometimes you have to have pretty extreme values before you even notice a difference. I noticed this being especially with leaning out, with riching it only takes a little and it makes a bigger difference.

Oh wow, I just realized that is strictly because of Open Loop/Closed loop. You make it richer for engine safety at WOT, well at WOT you are Open loop.

Found out why the idle was so high, the 4 Bar tune that I just started using had a higher Base Idle RPM

nice thread guys, good info. keep updated

im running the aem ems stand alone, i recenlt hadnt had a wideband for a while, then had a aem wideband for a few years but never had the wideband giving the ems data, so i recently bought a plx wideband and hooked the wideband up to the ems, and then benfenner told me i should activate the o2 feedback, its a really nice little feature that allows you to easily tune air fuel ratios for off boost driving, basicly its easier than having to tune each and every little cell , and instead of like a raw fuel number and adding in or taking out the tune you can actually just put like 14.7 from 0rpm up to 107kpa across to 7500rpm, and the ems will actually add in or take out depending on your existing fuel map to compinsate the fuel in order to target the certain air fuel ratio. i found that to be extremely easy in targetting certain air fuels vs trying to target each little fuel cell in the current fuel map.

now dont get me wrong my current fuel map without the o2 feedback isnt bad my any means, as far as driveability, however the o2 feedback acts as a overriding piggyback for fuel correction.

also i dont think its so much as the ecu not like being lean, but i run 720cc injectors along with step 2 hks cams, and i personally found the hks cams love the richer idle for stability, now they dont become completely unstable at a more lean condition, but they lobe alot smoother with more fuel, as i imagine alot of cams will...i really think its all a matter of how extreme your setup is as to how your setup will react to a leaner or richer idle condition.