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.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!
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?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.
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.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?
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 .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.
No.and with that i believe the more power you can make down low the better for your fuel economy.
In carbureted form, yes, EFI different.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.
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.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.
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.