How to get better MPG? (cal and elf attached)

98vtec · Post by **98vtec** » Sat Sep 27, 2008 4:10 pm

As some of you know, i have an h23vtec with high compression running RDX injectors. Well i have this thing tuned pretty damn well and its still just not giving me the gas mileage i have been expecting. Like right now on this tune, i am barely getting 120 miles to a half tank. My fuel pressue is still stock at ~45 psi and i havent tried anything else. Its a B&M regulator so i cant drop it lower than stock, but i can do the trick i saw on endyns website and drill a hole in the base to relieve some pressure but i dont know if that would help anything. Please check out my log and give me any pointers you could possibly give me. Thanks, Blake

HRTuning · Post by **HRTuning** » Sat Sep 27, 2008 5:02 pm

Why drop the fuel pressure? Just tune it for better fuel economy.

xenocron · Post by **xenocron** » Sat Sep 27, 2008 6:14 pm

HRTuning wrote:Why drop the fuel pressure? Just tune it for better fuel economy.

Well..different injectors will spray more efficiently at various rail pressures I would assume. If you can optimize the droplet size for fuel mileage (using Fuel Pressure)...any little thing will help. Also, increasing the temperature of the fuel before it hits the rail will help with atomization and fuel economy.

98vtec · Post by **98vtec** » Sat Sep 27, 2008 9:12 pm

i've been trying for the past hour to find the recommended fuel pressure but i cant find anything on it. I guess the only other thing i can do it keep leaning it out until i hear detonation or i get a misfire.

Post by **Bugermass** » Sat Sep 27, 2008 9:42 pm

low fuel pressure will reduce the quality of the spray pattern, you need to run it around 45-55PSI.. Also depending on the motor, somtimes running lean will net worse economy. try tunning all your part throttle to around 13.7AFRs and see if you get better fuel economy.. Best way to know, it get up to like 70MPH and and cruise and get your AFRs to say 13.7 then datalog and note injector duration, then retune cruising at 70MPH for like 15.5.. It'll probably end up being in a sligtly higher load area, the cruise again datalog and note injector duration.. Then compare, see which AFRs give you the least injector duration at a fixed MPH.. From motor to motor it varies..

98vtec · Post by **98vtec** » Sat Sep 27, 2008 9:44 pm

wow never even thought about that. Thanks chris.

Post by **Bugermass** » Sat Sep 27, 2008 9:45 pm

98vtec · Post by **98vtec** » Sun Sep 28, 2008 12:26 am

13.84 AFR / gear5 / 492mBar / 15 TPS / 68MPH / 3232 RPM / 5.81 INJ duration 14.95 AFR / gear5 / 492mBar / 15 TPS / 68MPH / 3227 RPM / 4.96INJ duration 15.85 AFR / gear5 / 470mBar / 15 TPS / 69MPH / 3260 RPM / 4.7 INJ duration

98vtec · Post by **98vtec** » Sun Sep 28, 2008 12:56 am

ok well im trying to upload the datalog but its not letting me. When i click \"add attachment\" it does nothing and tells me \"no post code specified\".

98vtec · Post by **98vtec** » Mon Sep 29, 2008 1:50 pm

i dunno maybe i just suck at part throttle tuning for injectors bigger than stock. It just doesn't make any sense to me. If the compensations were gear/load based i think it would be a bit easier....

Post by **Bugermass** » Mon Sep 29, 2008 2:49 pm

what exactly are you having trouble with???

98vtec · Post by **98vtec** » Mon Sep 29, 2008 3:22 pm

thats the thing i dont get. The engine runs amazing and can easily get an excess of 42mpg on the interstate, however, in the city i'm getting roughly 20-24mpg. It just doesnt make any sense to me. I dont beat on the motor and when im not trying to figure out why its getting bad city mpg I rarely go over 500-550mbar. Every now and then i feed my ego but its not often. I've gone into vtec 3 times (bad that i can count how many times, lol) in the last 2 months. I'm going to up the fuel pressure a little bit and play with the timing a little more. I think one of my problems is the compression. I have to run so little timing for the acceleration areas that is possible the fuel is not combusting properly even though it does not show up in the logs. I'm just confused i guess, lol. I know I'm not dumb and I know I have the ability to tune but this has got me scratching my head. When i had the engine running on crome, i was getting much better city mpg but the same highway mpg as i am now with ectune. I would think if there was anything wrong with my tune, it would show up in the logs and it just doesnt. I did the INJ duration test and it likes to be ran lean at cruising at part throttles. I also noticed (should have been common sense) that the Injector Duration is positively correlated with MAP. It follows the curve of the MAP in the graphs at all times other than fuel cut so naturally that would tell me to use as little throttle as possible while maintaining momentum so you dont end up using more throttle. ugh, just so many factors and variables.

98vtec · Post by **98vtec** » Mon Sep 29, 2008 4:55 pm

well i bumped the pressure and it seems to have fixed the \"shape\" of the acceleration portions. Theres no longer any big/long fuel humps or dips. Bumping the pressure to 55psi, i took out a good amount of fuel from the mid load part of the map and added (-10) to overall fueling which was previously 0. after i fill up and do some more tuning when its not so damn hot outside, i will update again.

98vtec · Post by **98vtec** » Mon Sep 29, 2008 5:18 pm

for anyone who is lazy and doesnt want to download the map, here are some screen shots of the new map vs the old one. NEW:

OLD:

the fuel comps and ignition are the same other than changing the IAT temperature resolution and adding the -10 to overall fuel.

HiProfile · Post by **HiProfile** » Mon Sep 29, 2008 5:40 pm

You might want to alter your driving style in the city. Some motors, usually larger motors, will benifit from lower RPM/higher load. The less load (higher mbar) results in less restriction, so less power spent pulling a vacuum in the wide bores. I actually drive my 1.5L beater in a 'spirited' fasion, but shift early, and get around 40 mpg. The key is to drive it where its most efficient, and the torque curve can tell you much. A dohc vtec head shouldn't have issues down low, but I'm not saying to use vtec's high-cam to save gas either.