Let's talk fuel efficiency!

[StavrosZhekhov]

I tried to find a thread specific to this, but couldn't.

I drive a 83 GSL and average only 15 miles per gallon, (13 city, 17 highway) For the sake of every 12a engine owner, are there any mods, maintenance, anything that can improve this? I checked my Haynes manual and found nothing of use.

Please help, this is so expensive for me to drive!

[chibikougan]

Nope better Get a Honda for daily.

[Whizbang]

seek out Peejay, might have to use the rx7club to do so. He got over 20 with his. He has tricks and tips. A lot is in how your drive the car. A carb sucks fuel under vacuum, unlike EFI, so engine breaking can use a far amount of fuel.

[t_g_farrell]

Your carb or emissions or exhaust is foobarred in some way. I'm assuming you have the
stock nikki carb and intake, full emissions and rats nest setup.

Normally you should be seeing well above 20 mpg highway, usually in the 25 mpg range if
everything is up to snuff.

I have a Dellorto 48 DHLA and no emissions or stock exhaust and I get 24-25 mpg normally. This is cruising on the highway. It drops to around 17-18 city and 10-12 in the
mountains

[StavrosZhekhov]

Originally Posted by Whizbang

seek out Peejay, might have to use the rx7club to do so. He got over 20 with his. He has tricks and tips. A lot is in how your drive the car. A carb sucks fuel under vacuum, unlike EFI, so engine breaking can use a far amount of fuel.

Thanks for the tip, if I find anything about it, I'll post what I find here to make things easier. I have to sift through all of his threads though, 125 of them.

[StavrosZhekhov]

Originally Posted by t_g_farrell

Your carb or emissions or exhaust is foobarred in some way. I'm assuming you have the
stock nikki carb and intake, full emissions and rats nest setup.

Normally you should be seeing well above 20 mpg highway, usually in the 25 mpg range if
everything is up to snuff.

I have a Dellorto 48 DHLA and no emissions or stock exhaust and I get 24-25 mpg normally. This is cruising on the highway. It drops to around 17-18 city and 10-12 in the
mountains

Everything is stock. I've heard about removing the ratsnest but only heard the only benefit is reducing clutter in the engine bay. Now, by foobarred, are you saying that you can't repair those items, only replace them?

[GySgtFrank]

As t_g_farrell said make sure everything is up to snuff tune wise first. It sounds like you're probably running overly rich. The numbers you're quoting are a little low for a stock port 12A. If it's ported those numbers are quite possible though. Getting more fuel mileage out of them is mostly a matter of keeping the rpms down at cruise and minimizing parasitic losses (when everything else is running right). Dragging brakes, wide tires, overly thick engine, trans, and diff oils, etc. will all cost you in terms of mileage.

[StavrosZhekhov]

This is the only thread of his that discussed the topic:

http://www.rx7club.com/1st-generatio...-529696/page2/

A whole lot of jargon I don't understand without doing extensive research on it. I kinda feel like I should've gone to school to be an auto mechanic instead of an electrician, certainly more useful.

[t_g_farrell]

Basically, do a tune up on it. New plugs, wires, cap, rotor, filters, oil change. Inspect all
vacuum lines and replace any that are cracked or broken. Then see where you sit.

Next step would be to start inspecting the carby for bad adjustments. You'll need the FSM
for that so you can know the process for each function and how to evaluate it.

[Whizbang]

Originally Posted by t_g_farrell

Your carb or emissions or exhaust is foobarred in some way. I'm assuming you have the
stock nikki carb and intake, full emissions and rats nest setup.

Normally you should be seeing well above 20 mpg highway, usually in the 25 mpg range if
everything is up to snuff.

I have a Dellorto 48 DHLA and no emissions or stock exhaust and I get 24-25 mpg normally. This is cruising on the highway. It drops to around 17-18 city and 10-12 in the
mountains

tell me more! im running a 48 IDA. Curious how to get some reasonable cruising MPGs

[Ubaru]

I get 27 mpg highway and 12 city. lean carb 15-30 oil, light gear oil, modded gear ratio for lower rpm at higher speed [just a tad harder on take off] but of course i started pumping up the power dunno what i will get after my last set of mods. removed all emissions, stainless steel apex exhaust, had the carb ported for larger needles an jets, high airflow intake 4 inch smooth pipes on a k&n filter, an now just got to get it to start. ignition bugs, i hate electricity at times.

[t_g_farrell]

Originally Posted by Whizbang

tell me more! im running a 48 IDA. Curious how to get some reasonable cruising MPGs

Your cruising mixture is dominated by your idle mixture. So make sure your idle
air adjustment is as lean as you want it. I think this is as true on the Webers as
the Dell. Not sure of the details for an IDA but thats where I'd start with it.

Oh and you have to keep your foot out of it. I normally cruise at around 3500 to
4000 rpm (75-80mph) and get this kind of mileage. YMMV LOL!

[Whizbang]

good to know about the idle mixture.

[diabolical1]

with respect to the Dell'Orto, i can pretty much second everything that TG Farrell said. i had similar experiences with mine when i finally got around to tuning it - oh, and mine was on a 13B that had seen better days. i got consistent 23-24 mpg on the highway and if i recall, i'd get around 18 in city/local driving. i really miss that Dell.

a 12A on a stock Nikki should at least match that, but should probably do a little better.

[sen2two]

Almost all of the milage is lost in the take off. Cruising at 2000 or 2500 rpm does not have that much of an effect as one thinks. Maybe 1mpg. But having to be the first one in the pack from a red light drastically reduces mpg. Do NOT engine break. Put it in neutral and roll to a stop. Let the old ladies pass you from the red lights.

I have a car that was getting 15mpg by the previous owner. It is now faster and gets 22mpg! The car has only gotten upgrades that would have made mpg worse. It's all in the driver. Learn to take off smoother.

Also, you can actually get better milage with a 4.30 (maybe even the 4.88's too) over the 4.10. The higher (numerically) gear allows you to use less throttle with the lower ratio to get going to your cruising speed.


I also had an F150 that got 20mpg that was originally getting 13mpg. And a full weight 12 second T2 that got 20+ mpg.

Ps. Weight is a killer! make it lighter!