Megasquirt mpg test

[webb1624]

Just curious what everyone is getting for mileage with a Megasquirt on a small block V8. I have a Megasquirt and really like it. I have been tuning on the car for about 6 months. I did a little road test the other day to check my mpg. I started at a gas station right off the interstate. Filled up, and drove 73.35 miles round trip (all interstate driving) at 70 mph, and refueled at the same station using the same pump each time. My ignition timing was 34 degrees at cruise and AFR was around 15.9-16.2 at cruise speed. I got 19.25 mpg. Next trip I changed the timing to 40 degrees and left everything else the same. I got 20.10 mpg. Next trip I left the timing at 40 degrees and set the AFR to 17 - 17.3. I got 19.43 mpg. My laptop battery was going dead so I couldn't do any more tests that day. I'm studying my datalogs from the trips to see what to adjust next. I'm trying to squeeze 25 mpg out of it. Here's a list of what I've done to the car.

Car is a 1988 Ford Mustang
1998 Ford Explorer block 347 ci
AFR 185 heads
Holley Systemax II intake
Buddy Rawls cam
Mac 1 3/4 shorty headers
2 1/2 inch exhaust
75 mm TB
42 lb/hr Bosch injectors
Walbro 255 lph pump
Ford Explorer ign coils
MS3 w/ MS3X expansion V3.57
LC 2 wideband (2)
4R70W with Baumann Opti-Shift controller
Precision Industries lock-up convertor 2800-3000 stall
1996 8.8 rearend with 3.73 gears, disc brakes
Cobra 13 inch disc brakes
Eibach springs, Koni shocks and struts

[slow_hemi6]

Try some slightly taller rear tyres. Works wonders and easier than a rear ratio change.

[ashford]

almost exact setup just e cam, t5 and 3.27 got me 25 in a capri at 70mph

[ol boy]

That's really good for a 347. 25 from a 302 seems to be a stretch but I'm sure with the right combo of stuff it could be had. I have a roller 306 with Elde rpm heads and 4R70W with 3.27 gear and barely squeeze out 20mpg.

[Laminar]

Here's the Fuelly for my 5.0 V8-swapped M3:

http://www.fuelly.com/car/bmw/m3/1997/laminar/375814

Best all-time tank was 23.8mpg, that was coming home from a RallyCross doing a steady 75mph on the interstate with the tires still pumped up to 42psi. More typical highway mileage is 20mpg.

Cruise AFR is around 16.0, ignition timing is around 34 degrees.

[DaveEFI]

Just done 250 miles - London to Morpeth. Heavy traffic. 29.1mpg. And it's a 3 speed auto. Was running VEAL, as I've been playing with injector dead time, so was varying the speed etc as much as possible.

[Laminar]

Just done 250 miles - London to Morpeth. Heavy traffic. 29.1mpg. And it's a 3 speed auto. Was running VEAL, as I've been playing with injector dead time, so was varying the speed etc as much as possible.

Whose gallon?

[ol boy]

Lol.. whose mile?

[webb1624]

I was able to do some more testing today. 60 mile round trip, same gas station, same pump, 93 octane fuel, same as first test I did. First test I set the timing to 45 degrees and AFR's were 15-9 to 16.2 at cruise speed. I got 20.639 mpg. Best mpg so far. Next test I left the timing at 45 degrees and took some fuel away and had the AFR's around 17-17.3. I got 19.676 mpg. It seems by all the tests that my engine responds to more timing but doesn't like it when I take fuel away at cruise speed. I don't feel safe with anymore than 45 degrees of timing. I'm going to do some more tests tomorrow and add a little fuel and get the AFR's down to around 15 and see what happens. I will also move the timing around to see if the engine likes that as well.

[TheSilverBuick]

With a Buick 462 (455, 7.6L) V8, 3,900lb running weight, 3.89 gears, short 26" tire, deep .64 overdrive running between 2,300-2,500rpm on the highway see around 19mpg. I run mine in the ~16.5 AFR and 42º-46º timing range on level ground going 70-75mph. Anything below 2,000rpm I have the timing pulled down to 32º or less and AFR's in the 14.5 or less to make sure it's won't ping on me (when running 85 octane with 10.6:1 compression).

Camshaft, vehicle weight and frontal area all are factors outside the EFI. I think there is 22-25mpg in my combination if I'd stick to the dang speed limit.....

[whittlebeast]

If you do create new gauge and define it as VVS/DutyCycle it makes a fairly accurate fuel economy gauge. With that and a friend playing with the timing table and AFR Target table, you can optimize fuel economy fairly fast. All you need is a long, flat slab of highway.

[subwoofer]

Duty cycle is extremely sensitive to inclines and acceleration, from experience it is very difficult to get good data on the road like that.
Linking power output and fuel consumption on a dyno to find the specific fuel consumption is the only reliable way.

[whittlebeast]

A really flat road and a steady throttle is very helpful.

Have fun

[TheSilverBuick]

I just drive the same road a lot, both ways. It averages out. I have the "Instant MPG" displayed along with the DC%, PW, AFR, speed, vacuum and ignition advance. A big block getting 19mpg at 2,500rpm isn't bad though, any real gains from here are going to be aero and chassis efficiencies (like change the gearing).

[Quagmire]

Just done 250 miles - London to Morpeth. Heavy traffic. 29.1mpg. And it's a 3 speed auto. Was running VEAL, as I've been playing with injector dead time, so was varying the speed etc as much as possible.

That's great! I am only getting 25-26 (UK mpg) in my Rover P6, and that's a manual! I don't have a TPS fitted so no fuel cut at the moment and I have been fiddling around with mapDOT AE again recently to try and remove the last little stumbles. Most driving for me is 35 miles into work, which breaks down as:

-30 miles motorway driving (including a 15 mile section of the M3 where it is a 50 mph average speed limit)
- 5 miles of heavy stop start traffic into Kingston Upon Thames, where I work.

[whittlebeast]

Activating trailing throttle fuel cut can be very helpful for fuel mileage.

Andy

[TheSilverBuick]

Just done 250 miles - London to Morpeth. Heavy traffic. 29.1mpg. And it's a 3 speed auto. Was running VEAL, as I've been playing with injector dead time, so was varying the speed etc as much as possible.

That's great! I am only getting 25-26 (UK mpg) in my Rover P6, and that's a manual! I don't have a TPS fitted so no fuel cut at the moment and I have been fiddling around with mapDOT AE again recently to try and remove the last little stumbles. Most driving for me is 35 miles into work, which breaks down as:

-30 miles motorway driving (including a 15 mile section of the M3 where it is a 50 mph average speed limit)
- 5 miles of heavy stop start traffic into Kingston Upon Thames, where I work.

I've used just the MAP threshold for the fuel cut (when my TPS shorted out and I waited a month or so to replace it). Once I dialed it in it worked practically as well as the TPS. I do have a manual transmission though, which can really pull vacuum down below idle levels.

[webb1624]

Did a couple more tests today. First test timing @ 45 degrees, AFR's 14.5 - 15.2. 20.897 mpg. Second test timing @ 40 degrees, AFR's 14.5 - 15.2, 19.6528 mpg. It looks like 20.897 is my best so far. I don't think I can get much more out of it in it's current state. Overall I'm pretty happy with the results. I didn't build this engine with mpg in mind. It was built for performance.

[piledriver]

Don't be afraid of high advance timing at low MAP.(below ~70 KPA) it won't knock.
The A/F mixture is burning slower at low pressure and needs lots of advance to finish the burn.
Leaning it further requires even MORE advance, as leaner burns slower as well.

An EGT setup can help here.

[slow_hemi6]

My car will start to surge if I push it too far.