Thread: Tuning for optimal mpg with DHP

Hey I'm getting the hang on things now but I don't know exactly the best way to tune for best fuel usage. I am only asking because I don't want to mess something up! So basically what tables should I be tuning? MAF? What am I watching when logging STFT or LTFT? And how should I go about making adjustments once I've logged things and reviewed them? Also when logging what should I focus on ie MAF, STFT, LTFT, RPM, MPH, KR, Spark anything else? Right now I'm using a stock DHP bin on a 97 GTP and I like the settings BUT compared to stock I'm obviously burning more fuel and also when I hit like 40mph it kinda bogs down and when I hit the gas to actually move it throws it into boost and then I let off and I'm good which I'm sure isn't right.. Thanks for the help guys I appreciate it VERY much!

I have only ever messed with timing, you are never going to gain MPG in the city unless you light foot it everwhere. I am lucky to get 16-18 city if that.

Basically I took a 04 GTP timing table and did some voodoo magic and combined it with my 00 GTP table for getting better freeway MPG. I have no cat or egr, so raising the timing a few degrees in all the spots (cells) the car would see during freeway driving helped. Stock is kinda around 32-35ish degrees of timing and I'm around 37-38, as anythng higher really doesnt much from what I've seen. Getting 30-32 mpgs is the norm for me if I go on long trips.

You don't want to mess with the MAF data for this. You can watch other parameters and stuff. LTFT could let you know of a vacuum leak, STFT just switch too damn fast to bother with unless the numbers are huge but then the LTFT would follow and show a reason.

Yea I'm getting 16-19 mpg 75% highway and basically stock.. I am fine with getting extra power but my main goal from buying DHP is gas and saving money.. I'm tired of filling my tank every 3-4 days it's crazy! I'm kinda ready for now to use stock settings for everything except trans I like how DHP has it setup with that and the power and stuff is nice to but gas is less the likeable LOL

And btw the mpg I just said was with a stock bin I just put on this DHP last night have to try it out but I know it's eating more fuel for sure.. I go to my GFs and on stock it takes .5 gallons on DHPs bin it took .8 today but I had it in boost a bit also

If you can only get 16-19 with a mainly freeway route, then part of me says its either a mehanical problem or sensor related.

Even the avg from the factory was mid 20's.

Everything is good mechanically though also sensor wise I know it's PCM related because before I edited the PCM from the canned ZZP I had I was getting 12-13 mpg and I changed the plugs which were to cold and it went to about 15 mpg then edited the PCM and I'm at 17-19 more towards 19 most of the time

And that's not the best fuel settings you can get.. I also need to change the fuel pump I think it's been acting weird for a little while along with the filter and adding the rewire kit

I just need to know what needs to be edited and what to look for etc

I'm not calling you stupid but make sure you have 4th gear. 75% of people who I have taked to that complain about bad mileage and they do a decent amount of highway driving are missing 4th. 3K rpms @ 65 mph or so is a good indication your missing it.

I have it

Originally Posted by darkhorizon

you cant change "fuel settings" because you will constantly be in closed loop, which corrects for any fuel changes you make.

Best things you can do is disable cat warm up timing cut, and disable alot of the warmup enrichment settings. After that add a ton of timing.

Then you can try going open loop and running lean cruise.

Agreed, open loop has definitely been working well for me. I set the baseline AFR for all cells at operating temperature to 14.7, and then I use the AFR adder in the cruise cells to run lean. Had to tweak the timing in those cruise cells to work best for the leaner AFR.

Also agree with fivefinger though, you should be getting around 30ish highway to start with. I'd make sure your front O2 is working correctly. I have found they can give totally bogus readings and not necessarily set a code.

im running nearly no PE with a flat pe/rpm/time.
lack of power sucks... but for mpg's....

Originally Posted by Turbocharged400sbc

im running nearly no PE with a flat pe/rpm/time.
lack of power sucks... but for mpg's....

I must not be understanding what you are doing. Why would you modify PE? Generally, if you are driving for MPG, you aren't into the throttle enough for PE to kick in.

If you are running super lean, and need a throttle position that pushes into the PE range... you can just raise the minimum throttle level for PE.

You guys also gotta understand I live in NY it's not like other places it's stop and go every few blocks my GF lives in NJ and it's totally different driving and way better mileage I've heard from many people they have the same mileage as me.. and regardless it's fine I was getting 12 mpg at one point but I just want the best gas mileage I can get as far as PCM settings

my local mpg are in the 12 to 14 too. highway can see up to 30 mpg if flat ground.


and the tune i have is set up for better cruise mpg. to bad it dint help out for the local any. its the same as stock was lol


i know SI, its all stop and go, pretty much like i got here. red light, stop sign over and over. if you hit 40 mph, its not for long lol

Exactly Scotty it's horrible I'm so jealous of the people who get to drive like 2 miles till a red light LOL

you'll have to as i do. suck it up.......or move off that 5 x 8 mile wide island lol

when your using the most fuel is when accelerating...i lean it out, less fuel, less power but im at 22mpg mixed driving and i dont baby it

hes got no mixed driving, trust me. its all local. its a rather small island, all stop and go. hell even the express way is bumper to bumper most of the time.