Gas mileage in my Ford Zetec modified:

My son and I round tripped from Nor Cal to Pomona and back on Friday and Saturday for the Roadster Show. My car is a 28 RPU based lakes style with a Ford Zetec four banger, Hilborn electronic fuel injection, Borg Warner T5, Hildebrand quickie, 5.20:1 ratio, 33 inch tall rear tires. This was the first real trip for the car, which ran pretty good except for one problem that we fixed in the hotel parking lot. Some people expressed an interest in what kind of mileage it would get so I keep pretty close track on the miles and the amount of gas and over all mileage was 20 mpg with the best being 22. This is driving a pretty steady 70 on I-5 and includes lots of LA stop and go traffic. I am pretty sure that I can improve as it is still pretty rich. I'll check it again when I go to Bonneville in August.

Drove thru the Central Valley in the afternoon on Friday it was 104 degrees and we really burnt ourselve and I do not have any insulation on the aluminum interior and floor panels so they got pretty hot, my son's flip-flops melted to the floor! Then froze our asses off coming back thru the Bay Area around 10 PM on Saturday night! Just love roadsters!!

Rex

 

That's a bitchin little roadster. I think you're on the right track (no pun intended) with the late model 4 cylinder. I'll be watching to see what you do to get more mileage out of it. Maybe try some taller gears.

 

i really like the stance. let's see some more pics.

 

I was looking for your car at the So-Cal speed shop Open house. I guess you did'nt make it?

Glad to hear you made your maiden voyage with no hassles.


CBB

 

Crazy,
We did make it to So Cal but it was 6:00 in the evening and lots of people were already gone.

Probably going to try a bit less gear maybe something in the 4.8:1 range and of course lean it out more but I really don't think I will ever get more than 25 mpg.

Don, thanks for putting my picture on your hot rod page!

Rex

 

Wow thanks for the update (keep'em coming) I'ts suprising to hear it's that low....I would think a warm 283 with a OD trans would get at least that....I would have expected quite a bit more with the Ztec.

 

Reality is a brutal thing sometimes. I am curious what it would do with, say a 3.50 ratio.

 

I would have to think it could get close to 30 mpg?

 

I too would have hoped for higher milage than that. What was the RPM when you were out on the highway at 70+?

I've got a couple of Olds quad-4s that I plan to start a roadster around. Was your engine already longitudinal, or transverse? Where did the bell housing come from?

Great lookin' ride.

 

I agree, bitchin car! I also agree, the mileage is lower than I would have expected. I also agree that a different rear end ratio will make all the difference if you are going for mileage.

 

Wow, real cool story. You and your son have a cool thing going on when you can drive all the way down to LA in a modified! Thats too cool.

I would have thought you would get better mileage with that 4 banger. Im hoping my wifes modified will get close to 20-22. Well have to test it!

 

That was my thought, I'm just curious but why the gear ratio that would be a bit stiff on some quarter mile dirt tracks instead of running something more highway friendly?

I realize that the car has a T 5 overdrive but the engine still has to be turning close to 2600 rpm at 65mph.
That same 2600 rpms with 3.55's would be 86 mph.

3.90's would get you down to about 1950 which is close to what my wifes box with wheels with a 2.2 cruises at.

 

In that light of a car, do you get tossed around the road on the highway or is it pretty manageable?

 

Rex that is a great looking roadster, my question is;

Is the distance in your calculation true and not thrown off by tire size gearing etc? Is it running too rich, my harley has that problem?

I would think that little beauty should be rolling the high 20's at least.

 

Oh yeah do you have some more photos on another thread so I can "study" it some more?

 

If I can get 34mpg on the freeway in my '07 HHR, you should also.

 

My 235 powered 53 got in the 20 to 22 mpg range to the Revival and back. It hasa weber 2 barrel, t5, an old 55 chevy rear and 205/65r14s.
And we were at 70 for hours at a time.

 

I would guess your HHR is a lot more aerodynamic than a modified.
As said before I think gear ratio is the main problem, but even completely tuned with a 3-something gear I would'nt expect more than high 20s at hwy speed.
Just my .02.

 

Can't you flop the gears in one of those? Sexual Chocolate gets 20 with the A/C on, and she weighs 3600lbs!

 

5.20:1 ! That's way low. Why such a low gear?

 

just don't go too low that you are at too low of an RPM in 5th while cruising. You could call Richmond or any gear company and they'll figure out what is a good gear.

I agree... if you don't get at least 30mpg in that something is wrong!


(but it does look really coool!)

 

I really think that it shows that I am not very close on the tune-up yet. More screwing around with the lap top to get it leaner maybe a bit more hps. For checking the mileage I used a GPS that is pretty accurate. I ran the car with a 4.4 gear when I first got it running and it was really to high gear but I am going to go to a 4.7 and drop the fuel by another 5% and see what happens. With the overdrive that is in the T5 when you drop it into 5th it really doesn't want to do much. I really think in need to do lots more screwing with the injectors and timing.

As for ride quality (poor choice of words!) it rides like a buck board! Really doesn't like the right hand lane on the I-5, lots of bumps!! We got into an area where they were doing some repaving and there were lots of place where the new pavement started or stopped and it was an experience!! We hit on section at a bridge and I know that both back wheels were off the ground!! Also the thing is really sensitive to cross winds, hit some pretty good ones on I-5 and really had to hold on. So I have a list of things I need to do before I take it to Bonneville in August. I think that no 50 sunscreen is at the top of the list!!

Rex

 

Doing the math with 33" tall tires he should only be turning about 2200 RPM at 60mph with the 5.20 gears he has (I am also assuming that a T5 has the same overdrive ratio as 700R4 so I could be off on that). A 3.50 ration would drop that to about 1500 RPM at 60mph which is probably a little low.

I would suspect that he was correct in his assessment that more tuning is needed on the fuel mapping.

Cory

 

Hell ya man! Keep us posted, I want to see what happens with this car.

 

Rex,
I have a rodding buddy here in Tampa that has a Zipper car. He got it built / cheap because of the way it rode as I recall. Took him a lot of time working spring rates / shocks to get the ride decent. Gary

 

Hey Rex, My T weighs 1700 empty. and on one trip, where it was 40-50 MPH of back roads for about 5 hours I got 30 MPG. But on most road trips which have 70-80 mph highway and local roads and such, and a few good blasts the average is 20 mpg. I'm running a 283 w/Edelbrock 4 bbl, and a T-5 S-10 style, and 4.11 rear and 27.5 tall rears(Bias). Hey, 20 mpg, that's the price of traveling in style.

On the ride, Mine has buggy springs with nylon(hard plastic) bushings in the shackles. I just drilled and put grease fittings in to lube them bushings. The difference is night and day. WAY smoother ride when the suspension can suspend.

Frank

 

FWIW I have an FI Zetec in a Lotus 7 clone and get about 24mpg in mixed driving. The aerodynamics are terrible (CD is about 0.7) so this is typical for a Seven despite being very small and light, don't know if other roadsters are as bad.... I bought it in L.A. a few months ago and drove it home to Norcal and the bumps on I5 scared the crap out of me, also got airborne a few times...turned out the seller had about 30 psi in the tires and that is waaay too much for such a light car, dropped it to 19 and it is OK now. Also, I've heard that you need to be very careful not to go too lean when tuning a Zetec as the rods are highly susceptible to detonation.

 

Interesting. I have a 153 Chevy II 4cyl with 2 45 weber side drafts. I haven't gotten mileage figures yet but just thought I offer what I have in the drive line for now. 3.73 rear, 30" tire, 20% overdrive (BW T-50 5 speed). It runs 60 mph at 2000 in 5th. Seems very smooth and settled down at that speed, but it doesn't pull away with a lot of vigor. 4.11's might be a better choice, or a little shorter tire.

I have to do some tranny tunnel changes to fit the speedo pulse generator to the trans, so mileage figures are a ways away.

Charlie

 

I can't quite figure why the car has such poor mileage but those humongous tires on the back may be a big part of what's killing the ride. That's a bunch of unsprung weight for such a light car.