[540Hotrod]

Well, it looks like Vince and I were both out doing fuel mileage testing today with the Holley EFI systems!

Just a quick update on my combo....

555", 11.4 compression, Brodix 3Xtra CNC heads, 266*/272* cam with .774"/.731" lift, G-Force GF5R trans (non-O/D) with 3.07 rear gears.

I'm using the Holley Dominator EFI with the 2000CFM throttle body and 1 to 1 throttle linkage as well as the Holley DIS Ignition System.

A couple of months ago we did a 2500 mile road trip with the EFI pretty much locked into the dyno tune we had used a few days before. Didn't take any time to play with it really in the car...just jumped in it and drove it. We got some high 13MPG readings on that trip.

Since then I've had a chance to play with it some to see what it can do. First thing is it pretty much lets you do anything you want to...good or bad! I *turned on* the self tuning feature again and then started playing with the 13.2 A/F ratio and the 37* timing we had limited it to on the dyno (and the road trip).

I had my wife drive one night while I monitored things to see what I could get away with for timing in the *light cruise area* as well as the A/F tune. I was able to put in 48* total (just like adding 10* vacuum advance) right where I wanted it. I think it could stand more...but I wanted to start out safe. I also played with the A/F ratio and found it could easily handle 15.5 A/F under light cruise. As soon as you *tip* into it, you're in another part of the fuel/timing map, so you never hear a ping.

Today I hit the road. I got out a little late...so it was in the 100*-103* range this afternoon during the test. I threw on some sunscreen and left the top down for a nice Sunday drive. I drove to a station that is right near the I-20 on-ramp and filled it up with 93 octane. This is pretty easy to see on old Vette's because the fill neck is big enough to put your arm in and you can see the fuel come right up to the neck.

I hit the road heading West....and made a 166.2 mile circle. I used the GPS on my computer to track speed and miles as well as I was watching the EFI do its thing. This stretch of road has no stops...but it is a solid series of long rolling hills, so not the best place to get big fuel mileage numbers...but pretty realistic in my opinion. The good news is that with 555" it climbs hills well without having to give any more throttle. I drove in the 65-72 mph range mainly which is around 2450-2650 RPM rpm in my car.

Everything went well....engine temps stayed in the 195* range mainly and the Intake Air Temp that the EFI was reading was in the 150-152* range. On the final 20 mile leg I tried leaning it to 17.0 A/F ratio and it actually did OK...but to keep it there will take some tuning in the areas around it to keep it from *rolling* any during light throttle cruising in the lower gears. Probably best to leave it where it was...or just do something inbetween. Also, that 17.0 A/F ratio is based on what the system is reading. A lot of cam overlap like I have can skew that number a little. Doesn't matter really...you just tune it to what it wants and use the numbers for reference in this case.

Anyway....when it was all done...I used 10.26 gallons to go 166.2 miles. That equals 16.19 MPG!! I was pretty surpised!

My old 1050 Dominator carb usually got somewhere in the 10-12 MPG range. Now I never spent much time really tuning it for MPG...just driveability and power mainly. But I gotta admit the EFI is doing everything and more powerwise and definitely doing much better on MPG.


JIM

[aukai]

I'll switch over when you can come and spend a week tuning it for the street and the track. Nice numbers for the mileage.

[540Hotrod]

All I have to is send you the file...bingo..it's tuned!

But I'd rather hand deliver it so I can play on the Islands!

JIM

[aukai]

OK as soon as I pay off a bill we'll work on it. And I'll take that as a Texas promise

[Tom Mobley]

Say, if Jim can't make it let me know. You buy the the ticket and put me up over there and I'll install and tune the EFI. You can either watch or help or both. By the it's done and I'm outta there you'll be the Islands leading expert on EFI.

[aukai]

Starting to sound interesting
Jim I've forgotten what intake you have.
I was wondering about the super victor over the C&C victor that I have. Which would be the better street manifold? If I did my research right the SV is .300 taller than the C&C Victor, is this right?
Don't mean to hijack this thread let alone an efi one

[Tom Mobley]

hmmmmm...... Hawaii

maybe you could start taking bids for guys to help you out.....

[aukai]

Originally Posted by Tom Mobley

hmmmmm...... Hawaii

maybe you could start taking bids for guys to help you out.....

OOOHH DOUGH
Shucks, just have you all come on over....

[GRN69CHV]

Gonna go out on a limb here - I suspect the 3.07 final ratio may actually be a contributing factor to the positve mileage and good manners of the EFI at cruise. When you look at Jim and Vince's combos, Jim's 555 is bigger everywhere, despite this, the combo pulled good fuel mileage. Vince has been struggling to get his car to run without bucking and surgin in top gear. Runs a 3.90/.62 OD for a final gear ratio of 2.41. Think we get to the point where you get so used to real low rpms from modern cars that you forget just how tight a 3.07 ratio really is. Very probably, even with MPFI, a hipo motor is just not efficient enough at lower rpms, especially with an OD trans where you have a negative curve in relation to vehicle speed and an increased load.

[69-CHVL]

Jim, good to see that I'm at least in the ballpark. Just suprised that my 850DP was within .5mpg of the MPFI. But the question is, when you get to 15-16-17:1, although the motor is running, how do we know that its most efficient there? You dont really know anything until you get back to the gas station and fill back up, be nice to get some sort of data while the car is running.

Can we somehow hook-up one of those MPG gauges to this system, so how, some way?

Joe, no problems pulling OD in top gear at all...its pulling top gear on slow back roads at 1500-1800 that are presenting the challenge. Will give the system a little more time to see what it can do.

[TD509EFI]

You could do a data log and check the TPS numbers against the MPH. Using cruise control ( if you have one) on a level surface and get back to back comparisons after you change the AFR. If you can run it with lower TPS numbers at the same MPH without driveability issues, you know your getting better MPG.

John

[69-CHVL]

That's what I was thinking John. The RPM and TPS are displayed together. I'll just have to hold the RPM as steady as possible on level ground, and see what happens. Hey, its all from the drivers seat, so I dont mind

[Doug F.]

Originally Posted by 69-CHVL

That's what I was thinking John. The RPM and TPS are displayed together. I'll just have to hold the RPM as steady as possible on level ground, and see what happens. Hey, its all from the drivers seat, so I dont mind

Way easier way - If you have the laptop software - Look at fuel flow in lbs/hr and tune timing and A/F at that point to minimize fuel flow.

If you don't have the fuel flow and have the Avenger - Look at fuel pulsewidth. I think it shows that.

[69-CHVL]

Originally Posted by Doug F.

Way easier way - If you have the laptop software - Look at fuel flow in lbs/hr and tune timing and A/F at that point to minimize fuel flow.

If you don't have the fuel flow and have the Avenger - Look at fuel pulsewidth. I think it shows that.

yep - it show pulsewidth! Smaller is better here right?

[vrooom3440]

Totally what Doug said. Coming up with a relative idea of fuel economy with EFI is really very simple/easy.

Remember that we input fuel in proportion to air, and air is input proportional to engine RPM (ignoring volumetric efficiency). A drop of RPM from 2400 to 2000 is close to 20% fewer gulps of air per minute which could bump a 14 MPG up to 16.8 MPG using very simple math (meaning overly simplified and not totally accurate). So at these lower RPMs a little change can make a big difference.

I am also under the impression that peak efficiency is obtained with full manifold pressure... so even if there is some reduction of power from leaning it should still be overall more efficient. Don't current BMW motors use control of valve timing/opening and fuel for engine power control rather than a throttle? Maybe it is some mix of those along with electronic throttle controlled by the drive by wire ECU system.