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

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.:yes:

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

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

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.

Starting to sound interesting:yes:
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:)

hmmmmm...... Hawaii

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

hmmmmm...... Hawaii

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

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

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.

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.

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

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 :D

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 :D

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.

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?

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.

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

Yes, BUT if you use pulsewidth, you must be comparing IDENTICAL RPM's. For fuel flow it doesn't matter.

Also keep this in mind. If you are going x mph going down the road, it takes a fixed HP to motor it down the road, not necessarily fuel flow. So if a low RPM if very inefficient, a higher RPM might actually take less fuel, but generally speaking lower RPM is better. A big cam like you have Vince might show this issue.

More cylinder filling, but less power from too lean might be partially offset by additional pumping losses. Seems variable valve timing would improve this.

Great results on that big 555"


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.

I'd like to see what this system can do in that range on the hwy. I like cruising on the hwy at 75mph pulling that kind of rpm with a 6speed.

It's going to depend a lot on the cam. As good as EFI is...I don't think it can overcome the physics of a huge cam etc. It can surely make it a LOT better by allowing you to super tune to fill in the holes in the driveability. If the cam is somewhat *normal* an EFI system like this could really do some neat stuff in the under 2000 rpm cruise range.

I think folks need to be realistic on *IF* the engine combo is going to be happy at a 1500 RPM cruise or not. Even the new LS motor folks can *mess up* a perfectly great running/low rpm lugging cruiser motor when they stick a big cam in it. Runs killer at WOT but loses some of the low speed smoothness.

JIM

What kind of shmuck would try and get a decent sized cam to run at very low rpm???

IMO the LS world has gone big cam crazed and the hardcore tech topics that used to go on for pages on LS1tech discussing cam specs and dynamic compression ratio have dried up.

With that said plenty of LS motors are happy running in 6th at under 2k RPM with cams in the mid to upper 230s at .050 112+4 or +2s and lift in the .600s on 347 cubes. I'm not expecting a cam like Jim's to cruise that low but I continue to be impresed with how driveable his setup is and the road trips he takes it on.

I also think a high velocity intake runner (which has likely been key to the big #s LS motors have made for their size) helps keep a bigger cam stay driveable at low RPM. On a 454 this Holley EFI combined with some of the new smaller runner higher velocity heads (RaceRites, AFR 265/295) and a hydraulic roller in the 230s at .050 would make an interesting setup.

What kind of shmuck would try and get a decent sized cam to run at very low rpm???

The same shmucks that are trying to get 20+ MPH out of their big cammed BBC's! :D

What the heck...it gives you seat time behind that BBC! That beats most of the data collecting that I've ever done!

good point there.

Just think.....20MPG RAT motors! How cool is that???

The heads on the LS motors are great....but have you noticed the size of the ports in the new stuff? Heck, they look like BBC rectangular ports! Goes to show that a great set of heads can make good power with milder cams. Throw more cam in it and it gets wild!

But somehow they just don't have the eyecandy appeal when you open the hood!

http://i318.photobucket.com/albums/mm436/540Hotrod/DSC02327_edited.jpg


JIM

What happened to seeing who can lay a longer set of black marks rather than who gets the best mpg! Lol...

What happened to seeing who can lay a longer set of black marks rather than who gets the best mpg! Lol...


Too easy anymore :D

Question is, who can run 10's and get 17-20 mpg in a BB...not me - just yet!

What happened to seeing who can lay a longer set of black marks rather than who gets the best mpg! Lol...

lol

When it became more expensive to drive to the Cruise Night at the local drive in than...

..to buy the Burger, Fries, and Shake at the drive in.


Besides why not have relatively big power and not stop every other county to get gas.

Hey, if this whole fuel mileage thing works out...we *could* build 15.0 compression motors and afford race gas!!

You KNOW I'm not willing to give up power for fuel mileage!


He heh heh........


JIM

What happened to seeing who can lay a longer set of black marks rather than who gets the best mpg! Lol...
I think Vince nailed it: laying black marks is just too easy :yes:

Real men need real challenges.
We live in a world of "AND" and are no longer satisfied with nor accept mere "OR" solutions.

And in the grand tradition, we layed black marks because we could and we tweak for best MPG because we can as well.

:beers:

Hey, if this whole fuel mileage thing works out...we *could* build 15.0 compression motors and afford race gas!!

You KNOW I'm not willing to give up power for fuel mileage!


He heh heh........


JIM

You know they say you can up the compression by running E85 :)

I don't see it around my area much yet. If it really takes off and becomes available it's definitely a great option. I'd be stepping up the program a lot!!

JIM

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

Yes, but if you compare pulsewidth it has to be at the exact same RPM. Fuel flow can be at any RPM. So go by fuel flow if you have the laptop.

4 milliseconds of fuel at 2000 RPM is the same fuel flow as 2 msec of fuel flow at 4000 RPM since the engine is running twice as fast.