Technical Fuel injection, dork question

What about gas mileage between a (supposedly) well tuned Holley and any of the modern FI kits? Is there any significant difference? (Ducking)

 

I've never checked gas mileage on any of my hotrods

 

There will be some. But if you keep your foot of of it they are a livable. The efficiency of the air pump (an engine) as designed makes more sense along with parasitic internal loads....an ohc will do better than a solid flat tappet.

 

First question to you -
What do you mean by "supposedly" ?
1. Do you mean, tuned by spark plug reading ?
2. Do you mean, tuned by mileage ?
3. Do you mean, tuned by 1/4 mile times ?
4. Do you mean, tuned by oxygen sensor gauge "in" the exhaust system ?

In general, a current Electronic Fuel Injection will be more efficient during cold starts and the first few minutes after that, than the best a carburetor can do.
BUT...if the carburetor has been "fully" (fully adjustable Holley "style") calibrated by the use of an oxygen sensor in both sides of the exhaust system and a person that knows the working of a fully adjustable carburetor, along with the help (but not solely used) of a dynamometer, the EFI and the carburetor will be fairly close, after the first few minutes after a cold start.

If you are comparing an old WCFB (or similar year carburetor) vs. a modern electronic fuel injection, then no, the best that carburetor can do will not be close to the EFI assembly.

Mike

 

hmmmm....it depends.

I took a 350 out of a 87 Suburban with EFI, which got 13 mpg. I put a different intake and a Qjet carb on the engine, and put it in a different, older, on topic, lighter, Suburban, and it got 17 mpg.

So yeah, they're different.

but maybe not the way you think. And you have to be careful about what is an apple, and what is an orange.

Either way, though the EFI stuff is off topic, unless it's a late 50s Bendix system.

 

That's what I thought. I don't know what 'tuned' in this manner means, it's a possible purchase from someone who does know his stuff. And it runs fantastically. But if it is to become a daily driver ( like I hope, at 30K a year) 16 MPG ain't gonna get it. I don't want to give too many details, but it's a properly, and well built GM 350, not total performance, but certainly not stock. Currently a TH400. What would an GM OD transmission be better? Or am I in another pipe-dream?

 

I would suggest doing a bunch more reading and less asking. You did say you were ducking

 

Like Jim said, you may be chasing rainbows. This is a traditional hotrod site. And no I don't have any police I.D.

 

And your not a dork. Lippy

 

Thanks all. I've had hot rods before, but never as a DD. Just trying to decide if my passion is a flame-out.

 

why not? That would have been respectable mileage for any car with decent power to weight ratio back in the old days. The cost of fuel is still similar to what it was then, when you look at the cost of living and how much money we have today.

Overdrive is a good thing for mileage, IF you build the vehicle to work well with it. As an example, years ago I had a 39 chevy sedan, also with a mostly stock 350 with a quadrajet...TH350, 3.23 rear gears. I added an overdrive, highway mileage went from 15 to 20.

These days my "fun" vehicles have big engines, and even with overdrive they get really crappy mileage. But I have enough money that I can afford the gas. And we have some later models that have modern engine designs, efi, overdrive, etc and get pretty good mileage. They're just boring as hell to drive.

 

I was at a driving event before the stay at home order. One rodder had a nice early 60's El Camino with a small block and a new square bore efi.
I asked him how much his milage improved from the carb. He didn't think it affected milage much, but cold starting was easier.

 

I put a fitech in my wife's off topic 50 year old car...cold starting was different, maybe better, but not like the OEMs.

getting one to work right can be tricky.

 

My rod has a 350 crate with 700R4 and 3:50 rear. I've worked some on distributor advance curve and metering rod size in the quadrajet. No Dyno tune or oxygen sensor. It gets over 20 mpg on the highway. Not a lot left to be gained.

 

[QUOTE="squirrel, post: 13989770, member: 3595"?]...we have some later models that have modern engine designs, efi, overdrive, etc and get pretty good mileage. They're just boring as hell to drive.[/QUOTE]

Yep, I agree.

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