6.3 miles to the gallon! Woohoo!

Emerald 74 4X4

Well-known member
So I decided to do the first calculation of fuel milage on my turbo 300 truck the other day. Yeah, this included almost all of in-town driving (except for a 5 mile stretch of highway to work) and driving under boost for tuning purposes. I burned about 15 gallons in 95 miles. I wonder what it'll get on on the highway with minimal time above 100 kpa MAP.
 
interesting.. I had a 10 second street Camaro in the 1980's that would average around 5 mpg
 
It shouldn't be too bad off boost. I haven't had too much experience with owning turbo cars but my turbo Nissan gets better mileage than the n/a version if I don't drive like a hooligan.
 
6.3! I would be interested to see the data logs from that!

My turbo and EFI MGB manages to get low 30s on the interstate and low 20's around town. If I beat the heck out of it, 15 around town. Thats about what it would do with the factory carbs as well!

Once the machine shop finishes up with my 300 we can have a competition!
 
Haha! I'm gonna drive it nice this tank and see what happens. One thing I notice is that it likes to run rich. Idle to about 1200 it wants rich, then cruise between 1800 and 2400 it likes around 13.8 to 14.8 AFR. The under boost I have it doing 10 and 11 AFR, which I think might be too much fuel. I might be able to back it off a bit.
 
I can't find the forum topic on the garret turbochargers forum but they said that even whith a turbocharged you wanna tune it like a n/a car at first keeping afr's between 13-1 and 14.7-1 for optimum burn. anything more than that is way to rich for any engine to operate near peak effeciency. Unfortunately I'm more intune with how import engines operate than my ford six, but I'm learning and they seem to be much easier to work through except for the heads of course when it comes to optimum flow. to bad the engine isn't as popular as the smaller six so we could have an affordable crossflow head to go along with our other mods.
 
High 10 to low 11 is very safe in boost. I target high 11 to very low 12.

In cruise I will add a lot of ignition advance and target a mid 15 to low 16.

Target about 13 around 100kpa.

I never have any complaints about an engine being rich in boost- that keeps everything safe!

I see you have pretty low CR on your engine. Low CR engines seem to like a lot of fuel.
 
Given I'm still in the tuning stages, I'm happy with what I have so far. I'd rather be running a bit rich than lean in any regard. I'm going to try and slowly lean it out over the tuning process and see what makes progress and what doesn't. As for now, it definitely likes to be rich. If I try and lean out the idle and cruise areas to 14.7 or above, it runs worse.

I think I need to retard some timing a bit more, or try running some higher octane fuel when the boost reaches around 7-8 PSI. I can hear a slight short ping at that point, then I let off. It may also need some timing retard in a lower RPM bin at 7-8 PSI which might also be my problem. The pressure is jumping up but it's still in a lower RPM bin where the fuel mixture is a bit leaner. Then it switches to the next RPM bin, enriches, then doesn't ping anymore.
 
I've got a pretty good tune on the Megasquirted Locost. I did a short 45 mile run in the Locost today. Burned just under two gallons in mixed hwy/city driving. Probably could have used less, but the throttle is too much fun to use. :eek: Light weight has it's advantages, but it still felt like every SUV-driving soccer mom in Orlando was trying to kill me....

I think I can get the mileage even higher once I get a wideband controller. So far all the tuning has been on the butt dyno, leaning out the VE table until the engine hates it, then bumping it up again until it runs better. My current spark table does go as high as 40 degrees, but that's at no load, high vacuum, coasting, so the fuel cut is engaged anyway.
 
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