Yellow Bullet Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
167 Posts
Discussion Starter #1
Assuming I'm not trying to push big power nor double the hp output of a 250hp 350 sbc, and just run low boost for improved output - and that I don't keep my foot in it all the time - could it actually improve fuel economy?

I've always heard this, and want to know if there's any truth to it?
 

·
Registered
Joined
·
4,131 Posts
Not likely, turbocharging is something like 1.2x more fuel. Someone here will have a more accurate answer but, it takes more fuel on a turbocharged engine to make it work, even at low load.
 

·
Registered
Joined
·
6,706 Posts
Well when the blades are nearly closed, there is no boost. The blades throttle it. For the same hp output the fuel usage will be similar. If it lets you avoid downshifting it could arguably gain some economy. But that is a stretch
 

·
Registered
Joined
·
223 Posts
You achieve some very slight efficiency improvement at cruising vacuum, as the turbo helps overcome induction losses, but as soon as you go over atmospheric pressure, you're using more fuel than you would NA
 

·
Registered
Joined
·
6,706 Posts
You achieve some very slight efficiency improvement at cruising vacuum, as the turbo helps overcome induction losses, but as soon as you go over atmospheric pressure, you're using more fuel than you would NA
True but is this somewhat offset by the reduced throttle needed?
 

·
Registered
Joined
·
160 Posts
Turbos are NOT more fuel efficient. They run much higher BSFC on boost. Plus they are a restriction on the exhaust at all operating points so it reduces fuel economy.
 

·
Registered
Joined
·
1,758 Posts
My 305 tpi engine seemed to stay the same after placing a turbo on it where the stock muffler used to go. I figure the turbo flows as good if not better than the oem muffler. Took the cat off so it flows better too but it hurt spool up abit.

Gas mileage day to day out of boost i’d say it was roughly the same, but it wasnt something I specifically cared about. But it did pick up over 100 hp over stock lol
 

·
Registered
Joined
·
115 Posts
If you keep you foot out of it you can expect roughly the same mileage.

I have two snowmobiles....both exactly the same....except one is turbocharged....over the same terrain/ride/speeds...ridden at the same time (girlfriend riding the other sled)...filled up at the same pumps....they will be within 1/10th of a gallon of one another if I keep the turbo sled out of boost.
 

·
Registered
Joined
·
943 Posts
A buddy of mine's Mustang went from 400+ horsepower 351w to a basically stock 289, not sure of the horsepower, and his MPG went to shit. With the Windsor it was just light pressure on the throttle to get to speed. With the 289 you had to give it half throttle to do the same. Granted these are NA but I would assume the same principles apply, find the right amount of horsepower to get the car rolling efficiently and it wouldn't matter how are you got the horse power whether it be turbo, cubes etc
 

·
The Liquor Makes Me Think
Joined
·
2,952 Posts
Seems like a lot of oem turbo 4cyl on the road with great fuel effeicency.
Its on the whole combo. Torque = cylinder efficiency. Bring the torque up and it will not have to work as hard.
 

·
Registered
Joined
·
1,120 Posts
The main fuel economy advantage you can get with a turbo is that you can squeeze an equal amount of horsepower out of a smaller engine. The motor will take more gas to make a given amount of horsepower at full throttle, but the friction losses off-boost will be smaller for the smaller engine. Or you could use the turbo to add power to an engine while having about the same mileage when you aren't under boost.

Note - turbodiesels are a completely different ball game.
 

·
Registered
Joined
·
525 Posts
Bear in mind that you'll likely have a lower compression ratio-so engine efficiency is lowered, plus you'll probably have lower timing advance settings to keep detonation at bay on pump fuel, again lowering engine efficiency. And once you have a turbo fitted you'll never be able to keep your foot out of the throttle!
 
1 - 12 of 12 Posts
Top