krochus

iTrader: (1)

I love the sound and power my 219/233 @109 cam provides. The issue is I'm driving this car WAY more than I originally anticipated. And even though the latest round of carb tuning has netted some impressive mpg gains between it or a 7.3 f250 I'm getting eaten out of house n home in fuel costs for my 60 mile round trip commute.

I know my overall setup with a th400 and 3.23 gears isn't exactly mpg friendly. But in your opinion is there a significant mpg gain to be had from "detuning" to a smaller cam?

newschool72

iTrader: (12)

I guess you could pick up a little bit better mileage if you widened the LSA out a little and killed the little bit of overlap you have. Right now you are at 8* . Something like a 219-225 on a 111 LSA would get you 0 overlap and make the engine idle and low RPM cruise a little cleaner. It should be worth a couple MPG, but it will also take a bunch of spunk out of that little 5.3.

Blowerman

Get a map sensor for your ignition box so you can mimic an old school vacuum advance at part throttle.

krochus

iTrader: (1)

You mean like the one I already have running 10 degrees at my steady cruise vacuum?

89gmcs15

iTrader: (7)

Hes just tryin to help... I get about 25 mpg with my truck with 600 hp and th400 with 3.73's but I only weigh 2800# so im sure that helps too. Is there more left in the tune? Maybe look at going to mvb 4l80 to gain the od? They hold tons of power stock and are everywhere in the junkyards for dirt cheap

krochus

iTrader: (1)

There's not much left to wring out in tuning. At 45> mph it's pulling 15.5/1 AF ratios. It could stand to loose a tiny amount of fuel at low speeds but nothing dramatic.

The car is VERY light on its feet weighing only 2860lbs BEFORE I yanked a pig of a cast iron motor out replaced it with an aluminum one and removed probably 100lbs of wiring, emissions and hvac garbage

3.27 gears 225/60-15 tires

Mpg is mid teens currently.

Pop N Wood

iTrader: (1)

Gearing is huge when it comes to MPG.

Are you still running with squared jets and the power valve blocked off? I don't have a lot of experience running that way but the whole purpose of the power valve is MPG.

krochus

iTrader: (1)

I'm on 72-82 jets no PV on a quick fuel carb now. I pull really good numbers on those but I am a tiny bit rich at low speed part throttle.

See my last post in my other thread and see what you think

89gmcs15

iTrader: (7)

Your gears and tire sizes arent so bad. The calculator puts your tires at 25.63 tall and with your 3.27 gears your cruising almost 70 mph at 3k rpm judging by the calculator at www.wallaceracing.com .. http://mobile.dudamobile.com/site/wallaceracing/default?url=http%3A%2F%2Fwww.wallaceracing.com%2Fg ear-speed.php#3003 thats the direct link for the figures I used. Its the mobile link tho so im not sure it will work

this is all going off my setup and I know every combo is different, but...

I had the same height tires and 3.73 gears. Over a 60 mile cruise with a couple stops and 3 jaunts from 40 to 110ish at wot I still pulled 23 mpg cruising at about 3400 rpms and 65-68 mph. I know the truck had 26 ish mpg in it driving nicer. Carb flowed 980-1040 cfm from pro systems and was a mech secondary 1050 dp with no choke. Timing was 29* with 10* added with the map sensor and a slightly rich 13~:1 cruise afr and rich 11.2:1 ish wot afr.

Maybe a different issue like converter or trans slipping or lots of stop and go or idle time or (we dont blame ya) a heavy foot?

like I said this was with my setup but I make more power, weigh the same ish, and had taller gears... somethings up...

krochus

iTrader: (1)

85. I know we've butted heads in the past and in the spirit of fellowship I mean this respectful as possible but your claim of mid twenties just doesn't add up by your own post.

3.73 gears
Rich AF
******* it
>20mpg

Now I'm no stranger to economy tracking and mods. I've owned and wrenched on a 3cyl metro recently, this car has a build thread over on ecomodders.com that spans pre and post engine swap. In my opinion your basing your claim on an anomaly reading. Something be it an early pump shutoff an odometer discrepancy has skewed your single data point. I'll bet that if you'll track mileage over several fills you'll find the resultant average quite a bit lower than what you expect.

As to my car. Honestly it's not THAT far out of line from what cars USED to get when three speed transmissions v8's and 3.xx gears were commonplace on new cars. This said its pretty abysmal by today's standards with my latest fill to fill data point coming in at 16.4 mpg. What's really funny though is the car struggled to get to 23+ mpg as a 4cyl auto in a good state of tune. Laughably losing only 6 mpg in the process of almost quadrupling the power output.

Another interesting observation is that over the course of several powertrain, gear and tire combinations all the "gear ratio calculators" put the rpm at any given speed appx 2-3 hundred rpm high. I chock this up to an unlocked torque converter and the difference in a loaded tire vs published specification.

89gmcs15

iTrader: (7)

I understand the questioning of the mpg my truck averages. My speedo is a speedhut gps unit that matches perfectly with timing mile markers and my hand held gps unit so I dont think thats off. Also my fuel cell has no filler neck and I always fill it to the exact same spot (just as it starts to come up the short neck it has.)

Another mpg log I did was my first decent trip with the truck for a burnout competition about 38 miles from my home. I drove roughly 60 mph there and then did 2 burnouts to blow a brand new set of tires. (Roughly 1:35 of spinning the tires at a high rate of speed 120-145 mph) and then drove to a near by gas station. All that and I still got 19 mpg. Drove home and checked it again after racing my friends e46 m3 and it was 21 mpg. But that was also before I did extensive tuning to the carb to lean the cruise afr out. It was low 12's then.

Ive since taken the carb off and put on a fast ez efi 2.0 tbi setup. If I dont see close to 28-30 mpg on the highway id be surprised.

On a different note tho when I first put my carb on and drove the truck I was getting roughly 8 mpg maybe even less. But that was alot of idle time and also had a leaking needle and seat and a **** poor carb tune.

I put a 34 gallon cell in my truck expecting the 10 mpg area but now I rarely need to fill it if im cruising.

the only reason id go with a od trans would be to get the rpms down at highway speeds but im not worried about the mpg side of it...

EDIT: My mpg estimates might be high this year as im adding weight from the roll cage and bigger rear end in the truck with 4.10's vs 3.73's, im also stepping up from a 255 wide 26" tire to a 325 wide 28" radial. But im going to a lexan rear window and kirkey pro street seats and also cut 120# ish from the wheels and tires, but It might not change from the mid to mid high 20's due to this

Blowerman

So I guess you wouldn't believe me if I told you I get 21 mpg with my square ported 496 in my 3800 lbs chevelle.