Hypothetically, would it be possible to tune a car to get better milage than what it came with from the factory? Lower the boost, take out some fuel?

This will be a good thread for NC Galant to respond to. This may end up in the Tech section because of it though.

When NC and I were tuning in the stroker we were running on crazy lean mixture at cruising speeds. This would make for some incredible mileage and seemed to have no adverse affects like knock while driving.

On the flip side I am wondering if this extreme lean condition attributed to the warpage found on some of my vavles recently? This is only a theory but here is where I'm comming from...

This head has been freshened about 3 times in the past two years durring various stages of my stroker trial & error project. The last time it was in the shop, I had 3 valves replaced from a bad rocker coming loose and causing collateral damage. This was in the spring/summer of 2006. At that time all the other valves which probably had less than 1000 miles on them, looked fine to Kalina Machine. A couple months later, a pile of tunning trips and a broken rod later (about 800mi.) the valves in cylinder three where the rod broke are obviously bent. Strangely 8 other valves are bent or warped. Kalina says that they have been seeing this type of thing more and more with leaner burning engines and crappier gas (This is just on daily driven comuter cars BTW).

NC and I did make a number of WOT pulls in the Talon and there was considerable knock a lot of the time, but it was in a semi-controlled environment. The Talon was never in a race against anything after the last head repair. The only all out runs were while on the logger with another set of eyes keeping watch. There were also never any full-on 1st through 4th or 5th gear pulls like a drag race.

Most of the time we did have the ultra lean cruise mixture though. It's not definetive, and any one of those WOT runs could have caused the problem, but it raises the question about ultra lean cruise tune.

A final point I would like to bring up for discussion is that I purchase Ferrera valves everytime I need valves. They are about four times the price of stock valves and I buy them for a reason. Or at least I thought I did. The old 'get what you pay for' and 'buy a piece of mind' addages prevailed in my decisions when replacing the valves each time. Well, with less than 2000 miles and no real races under their belt, I'm wondering if it's worth the quadrupled price tag to buy them. I will need to bring that up in a new thread.

It is hard to change the A/F under 4000 RPMs/40% throttle without an EPROM. During that time the ecu is in closed loop which is where it uses the O2 sensor to calibrate the fuel mixture. For tweaks, turn up your base timing to around 7 degrees and keep your boost low. The regular stuff like running good oil, a fresh air filter, good gas, and fresh plugs would also apply.

Running lean, around 18:1, is another way to get better mileage. I would not recommend this for most though. It is much easier to just let the computer control the fuel and add just a bit of timing.

I'm afraid I don't have any real tech knowledge to contribute here. However, I can relate that as a customer of a Works Rally Brainflash for my '03 Evo that, besides all the mid-range power and better peak, she would get approximately 2 more mpg.

They didn't market it that way but it is widely known by their customers. Going from 22 to 24 was a pretty big leap, actually! Alot of highway miles there.

I also recall a thread from David Buschur on Evolutionm.net about their tuning of a pair of their shop cars and how pleased he was at the excellent gas mileage they got out of them for the round trip.

So, possible? Damn right.

One other tip to add to ncgalant's short list: tire pressure. Properly inflated tires can net you a solid 1 MPG!

I get horrible gas mileage...I have a pretty heavy right foot, but for the most part on normal trips I notice my mpg is way low...

I attempt to tune my low throttle settings leaner, for better gas mileage/cruising purposes, but I have had no luck....With the mitsu ecu doing its job, no matter how lean I set my safc settings, my wideband always finds its way back to 14.7 during cruise....At idle, thats a different story...

Maybe my o2 sensor is bad? Well, the logger says otherwise....Sometimes the o2 cycles perfectly normal like it should when I cruise and idle, then a little later it will stay perfectly still at .001v which clearly is a sign of a dead/dying sensor....Who knows why, but the fact that it does cycle has stopped me from spending more cash on a new unit...

I guess its time for me to change my oil regardless, and I could use some more tire pressure

AEM recomends 15.9 or richer. I have set my 02 Feed back to 15.9 and get high teens with 280 dgree cams, and a 2.3. Egt's stay a a reasonable level too.

Have you hooked up you UEGO to your ECU?

I had Devo Tuning install my wideband, since I didnt feel like welding a bung and whatnot so they just finished up the wiring themselves and all....I doubt they spliced into the ecu....

Whats the difference?
-Josh

The AEM UEGO has a 0-1V analog wire to mimic a narrow band. So it's alot more accurate for the ECU to read off of.

I was just looking through my AEM notes and this option only came on the AEM-2300 UEGO. This is the unit I have, it is the box (controller) without a guage. So if you have the gauge type your out of luck, but if you have the same one I do you conect the white wire to pin number 4 on your ECU.

Oh interesting...No mine is the gauge type UEGO....My fuel adjustments are set to go lean, but my wideband always finds its way back to 14-15a/f...Whatever

What would the logger show as far as fuel trims with a super lean a/f for cruising...Would that make the Mid/hi trims go to? 110-139?

I couldn't tell you, the grater part of my tuning expericance comes form stand alones. Sorry.

To make a super lean burn you would have to get both the O2 trim and high trim to max out. High maxes at 139 and I think O2 goes to either 159 or 169. After a while though it will think your O2 sensor is bad and make your milage worse. The whole thing really gets pretty complicated with a noneprom ecu.

All in all, it sounds like there's not much you can do to mess with fuel economy by simply tuning.

Since we are on the topic of gas mileage, I may as well ask a question. I have a mildly modded 1g DSM.

-K&N
-Intake/UICP
-Spearco SMIC
-MBC
-Walbro-255
-Exhaust-not installed
-DIY ported 14b/mani/o2 housing


I will swap out the 255 with a 190 sometime in the near future because I dont have the $$$ for an AFPR and I dont plan on getting any major mods other than a mild set of cams. When that is done, I want to throw on a 2g fpr to get the most out of the 450cc injectors.

Now here is my question. I know that by increasing the base fuel pressure a rich condition will exist at WOT because the 1g ECU still thinks the base FP is at 38.5psi when it will be 43.5. But while cruising, will the ECU be able to compensate for the higher pressure via the 02 sensor? I really would like to raise the pressure, but I dont want to do it at the expense of gas mileage. What do you guys think?

Also, while im at it, since the fp will be higher, I will hack the MAS to lean out the mixture some more and have better combustion

Nomie

Why do you want to increase the base FP if you don't need it at WOT? If you're running lean at WOT, that will help. The ecm will correct the A/F in closed loop to some extent.

The reason why I want to raise the pressure is because my stock injectors at 10lbs of boost are seeing close to 90% duty cycle. Im sure when I raise the boost, install the exhaust and cams I will need extra fuel..

So, raising the fuel pressure will have no adverse effects on gas mileage?

No it won't. Closed loop can make up for that. I would recommend hacking the MAF one small bit at a time to make sure you don't take out to much. Log her between changes to see what happends. It may be enough just to take out the lower comb and then play with the adjustment screw in the bottom.

Thanks for the advice! Im so excited it wont hurt gas mileage!

I've found that all the modifications and tuning I've done to my car has actually increased the mpg. When I first got the car it got 19, now even with bigger injectors, bigger pump, bigger everything the milage has gone up to 25-26. Faster and more mpg, got to love that!

Shamou got a little less than 20 on her first tankful.... hoping that goes up. Might be worth throwing the SAFC on just for kicks.

I know stock these cars run on the rich side, so hacking the MAS should lean out the a/f ratio. Though my question to you is this, what exactly should I be looking for on the logger? Knock will be the #1 priority as always, but there is no accurate way of seeing if the car is running better or not without a wideband.

What do you think?

After hacking the MAF properly your fuel trims should be close to their normal levels. If I had the guess they would end up at 125lo 110mid 100hi. This is commonly what happends when you hack a maf because at low air volume, such as idle, most of the air goes through the hacked section, but from cruise to WOT the flow evens back out. This is why you hack to get the high trim between 100 and 110.

BTW, unexplained crappy fuel mileage can often be attributed to bad O2 sensors, also. Have 'em checked out if your mileage is down!

I have seen the same results and even damn near identical numbers to what you said above... although... I wonder if the mods simply replaced some much needed maintenence items that had I just replaced with OEM would have improved mileage as well or more.

The other thing is the theory that a HP engine works more efficiently because it doesn't have to work so hard to get out of it's own way. thus it might get better mileage on it's own as long as it isn't under a large load like racing.