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We've seen this topic in various threads, there is even a Youtuber with a 302 running a lawnmower carb with 'amazing' results... So, here is the forum to discuss vairous MPG/Hypermileing and economy mods!
 
Back in the 70s when gas hit 75 cents a gallon I thought the world was going to end! I bought a new Holley "Economaster" one barrel carb to replace the 1100 on my 200. I didn't notice much of a change, maybe a couple mpg in an already relatively economical car. The Holley didn't take well to repeated periods of storage though, and I switched back to the 1100 a few years later. That's all I've got on the subject!
 
We've seen this topic in various threads, there is even a Youtuber with a 302 running a lawnmower carb with 'amazing' results... So, here is the forum to discuss vairous MPG/Hypermileing and economy mods!
He took the car with that set up to a car show with a dyno and got 40ish hp to the rear wheels. He also had a trick “carb cheater” set up to control AFR with his iphone and an app he created. Later he showed how you can set up the carb to run like crap and turn the ignition off as a theft device for older cars.
Recently he used that same device to make his own home made sky ram intake work and drove it to the hot rod power car show going on this week.
 
I know people like their linux and hacking sourcecode and tinkering and all that, but seems to me that the snipers and purpose built dizzy are the easy way to go over megasquirts and other similar solutions.
 
Just restricting the airflow of the engine is not going to help fuel economy much, you can do that by simply "keeping you foot out of it", in fact its entirely possible to make it less efficient that way. Otto cycle engines have very poor thermal efficiency as load drops away they become quite bad, if you look to modern eco engines like the GM equinox 1.5 (i have one) they are very good on fuel. The idea is to have a small displacement engine direct injected and turbo. The turbo is almost part of the head so little heat is lost to the turbine, this gives almost instant response when torque is needed. Otto cycle engines with homogenious charge can only run over a limited range of mixture strengths, once your outside these limits combustion stops. Fuel economy on the road is largely dependant on many factors mass, drag, load etc. It would be far better to address those factors than trying to improve thermal efficiency from what is in reality an old clunker. TE is built into he engine, there isnt much you can do to improve it. Once its tuned and running well, your at the limit. So any "truck" by virtue of its task and design, is never going to be economic, UNLESS, its a well designed DIESEL! And even then it has to be driven in a manner to reduced fuel usage. Basicaly its , work=fuel used, less work, less fuel.
 
Just restricting the airflow of the engine is not going to help fuel economy much, you can do that by simply "keeping you foot out of it", in fact its entirely possible to make it less efficient that way.
Are you saying that the guy with the 302 V8 with the small carb is not really getting 40+ mpg or are you saying there are other reasons why he is getting 40+ mpg?
 
Are you saying that the guy with the 302 V8 with the small carb is not really getting 40+ mpg or are you saying there are other reasons why he is getting 40+ mpg?
He may have improved the drag of the engine in a small way, but I would say it was mostly down to "other" factors, and carefull driving. If you look at the mileage marathons that are often run, guys car get 100mpg out of stock vehicles by very frugal driving. One easy way to cut fuel usage is to travel slowly. One thing to keep in mind is that the best TE of most OTTO engines is at around 75% full load, do you ever drive it there? Most of the time our taxi engines are operating in their least efficient areas. Our 2016 Falcons with the Barra engine car get down to around 9/100km on the highway, this is very good for a big car with an auto and 4litre engine. This gives some indication of the improvement that have happened over the years. The heavy trucks that are dragging around 60tonnes have not change their fuel usage for a long time, but they have doubled in power output. There are Scanias and Volvos down here with 450kw (700bhp) they can go up to over 100tonnes (200,000lbs) as a road train but they regularly run to 75tonnes with b doubles.
 
He may have improved the drag of the engine in a small way, but I would say it was mostly down to "other" factors, and carefull driving. If you look at the mileage marathons that are often run, guys car get 100mpg out of stock vehicles by very frugal driving. One easy way to cut fuel usage is to travel slowly. One thing to keep in mind is that the best TE of most OTTO engines is at around 75% full load, do you ever drive it there? Most of the time our taxi engines are operating in their least efficient areas. Our 2016 Falcons with the Barra engine car get down to around 9/100km on the highway, this is very good for a big car with an auto and 4litre engine. This gives some indication of the improvement that have happened over the years. The heavy trucks that are dragging around 60tonnes have not change their fuel usage for a long time, but they have doubled in power output. There are Scanias and Volvos down here with 450kw (700bhp) they can go up to over 100tonnes (200,000lbs) as a road train but they regularly run to 75tonnes with b doubles.
I shared his videos in the other thread if you care to watch them. And i agree with you about work= fuel, and with that i believe the more power you can make down low the better for your fuel economy. I once saw where a 351 was given heads intake and carb, but stock cam and made 340ish hp and 400 + torque, they then went on to change the cam and got near 500hp i believe. But i got curious as to what economy they might have gotten with the stock cam. My idea is turning a kid with asthma into a marathon runner. I do got a 351 laying around and since my 300 isnt getting the fuel economy i was hoping for i might as well be using the 351 and be able to make more power and torque for cheaper. But at the same time, how is that fun when its so easy. I like challenges 🤷🏽‍♂️.
 
and with that i believe the more power you can make down low the better for your fuel economy.
No.
What Aussie7mains said was "One thing to keep in mind is that the best TE of most OTTO engines is at around 75% full load, do you ever drive it there? Most of the time our taxi engines are operating in their least efficient areas."
By that same statement, the more engine torque that is available at cruising rpm, the more inefficient the engine has be operated to have the minimum torque required to maintain vehicle cruising speed.

The general theme here and also in the video is that a light duty vehicle doesn't need much power to move it down the highway at cruising speed.
This allowed the video car to be operated with a very small carburetor with a max power around 60 hp at the rear wheels.

A low rpm, high torque 300 six has the least TE because the low rpm torque cam requires a very low static compression ratio for a given pump gas octane. If you want the engine to run on 87 octane pump gas to save on the cost of fuel, then the SCR will be very low and have the least TE.

The highest gasoline efficient engines produce peak torque at relatively high rpms and operate far below the peak torque at highway cruising speeds.
The camshaft profiles under these conditions allow for a much higher static compression ratio for a higher TE.
The later closing intake valve also decreases the Volumetric Efficiency at low rpm causing the engine to pump less volume, making the engine run as though it has less displacement.
The engine will produce the least amount of low rpm torque but sufficient enough to move the vehicle at highway cruising speeds with a higher efficiency.

I see a 240 six with an EFI head and high compression with the proper cam profile and low friction piston rings as previously discussed as being a good combination for a very fuel-efficient Ford inline six.

An engine designed to operate the majority of the time pulling heavy loads is a totally different story.
 
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WOT dyno chart torque numbers, don't seem like they'd be all that relevant, in a part throttle, mileage-seeking scenario?

Doesn't a small carb, operating at full throttle, more efficiently atomize the fuel, than a big venturi unit barely cracked open?
Booster signal strength, right?
Otherwise, we'd just have different sized single throat carbs, rather than multiple throats, spreadbores, CV/VV, air door operated metering, etc.
 
WOT dyno chart torque numbers, don't seem like they'd be all that relevant, in a part throttle, mileage-seeking scenario?

Doesn't a small carb, operating at full throttle, more efficiently atomize the fuel, than a big venturi unit barely cracked open?
Booster signal strength, right?
Otherwise, we'd just have different sized single throat carbs, rather than multiple throats, spreadbores, CV/VV, air door operated metering, etc.
In carbureted form, yes, EFI different.
 
Just saw Thunderhead 289 is selling carb cheater kits now. I posted about it on the Big 6 forum. Link in the thread as well. Now to just to get that lawn mower carb. Part of me has wondered if the brigs n stratton carb from their 18 hp v twin pony engine would work better.
 
Most of the efficiency gap between gasoline (Otto cycle) and
diesels is due to the higher compression ratio of the Diesel cycle.

But a further efficiency hit against spark ignition engines is the throttle.
It takes engine output (fuel burned) to produce manifold vacuum.
The further closed the throttle is the worse this loss will be.
 
Most of the efficiency gap between gasoline (Otto cycle) and
diesels is due to the higher compression ratio of the Diesel cycle.

But a further efficiency hit against spark ignition engines is the throttle.
It takes engine output (fuel burned) to produce manifold vacuum.
The further closed the throttle is the worse this loss will be.
And the diesel cycle runs on the constant pressure cycle, and it operates as a stratified charge, this means that the fuel added can be beyond the stoichiometric point as an average, but the mixture is rich enough to burn at the injector. Your correct with high compression, and throttling (although some diesels are throttled) loss, and the expansion cycle is greater. the other main advantage is that there is no knock, this means you can virtually raise the manifold pressure and therefore the BMEP, until the piston melts of the crank drops out the bottom. Some of the tractor pullers have 250psi manifold pressure. Many regular heavy duty engines like M.A.N diesels run 30-40psi. I worked with a GAZ (Russian) engine that had at least 30psi, it could produce 300BHP from 6.6litres all day long, it is a really heavy duty thing.
 
Part of what spurs the arguments or suspicion, is the testing and results. Supporting facts. Yes, I imagine he may have achieved 40+ mpg under unknown conditions, but the next question is determining the primary reason - why? A direct validation for power limiting would be to simply add a throttle limiter to the stock carb, so it only produces the same top speed as the mower carb. Equivalent HP. Now go drive it and see how the economy changes (or not). ;)

Objective tests such as this would qualify the primary reason(s) for the gains, rather than endless speculation. Of course, more tests using scientific method would follow, so additional improvements could be made by tuning or mods to support greater gains. :cool:
 
Part of what spurs the arguments or suspicion, is the testing and results. Supporting facts. Yes, I imagine he may have achieved 40+ mpg under unknown conditions, but the next question is determining the primary reason - why? A direct validation for power limiting would be to simply add a throttle limiter to the stock carb, so it only produces the same top speed as the mower carb. Equivalent HP. Now go drive it and see how the economy changes (or not). ;)

Objective tests such as this would qualify the primary reason(s) for the gains, rather than endless speculation. Of course, more tests using scientific method would follow, so additional improvements could be made by tuning or mods to support greater gains. :cool:

Start you own thread & or list your product in the for sale section if you own the right to sell it.
 
I'm not selling anything. I am directly responding to this thread. I am discussing and hoping to help others understand some of the principles of "tiny carb" operation, previous similar efforts I am aware-of, and potential alternatives to prove true value and possibly achieve similar results much easier or simpler. Perhaps I am not understanding your point?
 
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