RPM's and Fuel Efficiency

[dsnyder]

As I'm getting used to driving my new (to me) 1978 Spider, I am discovering where the sweet spots are during accelleration. As I've never driven a car with this engine/weight combination, I was wondering where the efficiency range is as far as RPM's? In other words, at what RPM are the most efficient shift points (efficiency, not best accelleration)?

Just based on the feel of the car, it seems to be more comfortable in the higher range of engine revs. Even in 5th gear, at 65mph, it does not seem to be loping along, revs seem high- definitely not like having an over-drive. If that is how it should be, I'm fine with it but I was wondering.

-Dave

[mbouse]

ummm... do you know which rear end you have? i believe '78 came with two different rear ends, and the majority weren't geared well for highway.

my '78 runs 500rpm's more at 60 mph than my '80 does.

but when you drive like i do, fuel efficency is not a huge factor. i like to drive my car as if it were stolen..

[engineerted]

What? does't everone? Blaaaaaaaaaaaaaaaaaaaaaaaattttttttttttttt, Vrooom Vroooooom. Dam I am bored! Work is so slow before xmass.

Ted

[mbouse]

work? oh... yeah guess i should look busy

[engineerted]

Its hard to stay busy when you are the only guy here, layed off another guy last Friday, now we are down to 5. Not much to cheer about this year other than that my wife and i still have a job. Come on lets see some snow!!!!

Ted

[So Cal Mark]

engines really like to run where peak torque is, and on your Spider that is close to 4k. The 78 should have a 430 rear end, so cruising at 70mph will be around 4k depending on your tire size.

[mbouse]

if it is gonna be cold, it might as well snow. then i gotta excuse to go buy some new tires for the Ranger. that'll get me outta the house for an hour!

be glad you are one of the five WITH a job. according to what i've read recently, Michigan is at 14% unemployed. typically, that includes only those that are seeking work and are drawing assistance... not those that no longer qualify for unemployment compensation. that number (uncounted) typically is around an additional 5%... making michigan near 20% unemployed.. that is one in five, bubba... who's next at your place?

yup. be thankful you gotta job. they are getting scarce around here too. we're adding up the days before we shut the doors for a week or two, and only some will return when the doors reopen. this shop is down 50% in total from what we were a mere three years ago, both in sales and in employment. not a pretty picture.

[dsnyder]

If you get the storm that hit us last night here in Arizona... you'll get all the snow you want. Plus we had 78mph winds last night with the rain. It was moving East so get ready.

I don't know what rear end my car has. Is it stamped on the pumpkin?

Dave

[mbouse]

good question. i dunno for sure, but i am sure someone else does. what rpm do you run in fifth gear at 60 mph? 3,000 or 3,500

[dsnyder]

3600 RPM at 60... Is that 5th gear considered an overdrive?

[mbouse]

yeah... you got the same rear end as i
fifth is overdrive

[BurbankJalopy]

Your facts are all wrong, the Messiah has created hundreds of thousands of high paying jobs. You guys aren't getting the news - earlier this year my unborn children rushed to spend billions and likely trillilons to keep the unemployment rate below 10%, and CNN tells me it worked really well. (I can't resist getting political when the opportunity arises.) Back to your question, my fuel injected '81 gets about 20 to 26 mpg based on the one or two times I calculated it. It seems to get more mpg on back country roads around 45mph or so...but I don't really care too much about mpg with old cars like the Spiders.

[JimM]

Dave--
My 78 will cruise very smoothly from 50 mph at 3000 rpm up to 75 mph at 4600 rpm in 5th gear. Since I have never run a full tank of gas at one particular speed to check for mileage, I do however get between 23 to 25+ mpg as an overall average. Best acceleration seems to be between 4000 rpm and 5500 rpm with a very modest decline in mpg at this rate (not used for extended periods). All this said and done, if I was strickly looking for mileage I would drive my wifes Ford Focus at 30+mpg and no fun. Besides, how many people do you know that can point at their car and say "I do all the work on it". It's all part of the fun of owning a "classic".

Good luck and enjoy your ride. Jim