I am a novice so i have another question. while looking into fuel injectors I noticed a calculation that seemed to indicate the need for larger injectors on supercharged applications, even larger injectors for turbos.....AT THE SAME HP .Is this true???? at the same HP and rpm....is the supercharged and turbo engine burning more fuel? Why?I assume this has something to do with parasitic loss of a supercharger.......and heat therefore timing to control detonation????How much does a huge intercooler help the fuel consumption if at all?

2.

3. Originally Posted by dnewps
I am a novice so i have another question. while looking into fuel injectors I noticed a calculation that seemed to indicate the need for larger injectors on supercharged applications, even larger injectors for turbos.....AT THE SAME HP .Is this true???? at the same HP and rpm....is the supercharged and turbo engine burning more fuel? Why?I assume this has something to do with parasitic loss of a supercharger.......and heat therefore timing to control detonation????How much does a huge intercooler help the fuel consumption if at all?
You can run a N/A engine closer to stoich than a boosted engine so this is a large part of the reason the boosted engine burns more fuel. As to how much more , there are many many variables such as what kind of fuel your burning and the efficiency of the engine that your burning it in. Every engine will be different.
Some of the automobile manufacturers have been able to run smaller engines with turbos and still make the power of a larger engine yet burn less fuel.
Here's a good read on the subject. Check out the list of stoichiometric ratings of different race fuels at the bottom of the page.
http://www.highperformancestangs.com...Considerations

4. intercoolers help fuel consumption by cooling the charge so that fuel doesnt have too, basically you can run a leaner afr with a intercooler and be safe, whereas without a ic you've gotta lay the fuel to it to keep detonation at bay and somewhat cool the charge.

5.

6. Remember, belt driven SC's require hp to spin. Roots take the largest. So, these will use more fuel per crankshaft hp.

7. Originally Posted by cfm
Remember, belt driven SC's require hp to spin. Roots take the largest. So, these will use more fuel per crankshaft hp.
isnt it true, if you underdrive the blower, you will use less fuel?...just askin'

FastRat

8. Originally Posted by FastRat
isnt it true, if you underdrive the blower, you will use less fuel?...just askin'

FastRat
Rule of thumb for aircraft

1/2 # of fuel / hour / horsepower N/A

.8 # of fuel / hour / horsepower supercharged

Intercooling can give great gain in power a highly boosted diesel Ie 55 psi boost at 900 deg
thru a intercooler equals 34 psi at 300 deg and for every 11 deg cooled you pick up 1% power increase

9. Originally Posted by cfm
Remember, belt driven SC's require hp to spin. Roots take the largest. So, these will use more fuel per crankshaft hp.
Yeah, but it isn't much I tell everybody that 3" wide kevlar reinforced toothed belt is just for the bling factor. I could drive with one 1/2 V belt belt but it just doesn't have that "LOOK"

Originally Posted by FastRat
isnt it true, if you underdrive the blower, you will use less fuel?...just askin'

FastRat
Less than what? A over driven one? Well yeah, duh! less than a N/A. No! Not at the same HP. You have to pay to drive the blower. And with a roots, its huge. With a centrif, a little less. Not as much less as some think, or you would never see toothed belts on vortecs, and they would just drive them all with the serpentine belt driving you alternator.
Turbos are the furl economy kings. Least power draw from the engine directly, but as Hass and Impatient stated, you need some extra fuel partially for cooling, partially as a safety zone from detonation. You can run a blower right at the "best power" or even stoich, but your walking a tite rope with anything but a damn good F/A/S EFI setup.
You can only cool a blown gas deal with AF ratio and no intercooler so much and that it. Too rich and the power goes south and you still risk a piston. AF is not the answer. Blower guys cool it with fuel, but not with the AF. Turbos guys talk AF cooling, blower guys don't. Thats why ALL turbos except alky/E85/blow thrus should be intercooled.

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10. who is that mask man

with the silver bullet

11. Thats just the homeless guy they let wipe down the boat to make a little food money

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12. Originally Posted by gn7
Yeah, but it isn't much I tell everybody that 3" wide kevlar reinforced toothed belt is just for the bling factor. I could drive with one 1/2 V belt belt but it just doesn't have that "LOOK"

Less than what? A over driven one? Well yeah, duh! less than a N/A. No! Not at the same HP. You have to pay to drive the blower. And with a roots, its huge. With a centrif, a little less. Not as much less as some think, or you would never see toothed belts on vortecs, and they would just drive them all with the serpentine belt driving you alternator.
Turbos are the furl economy kings. Least power draw from the engine directly, but as Hass and Impatient stated, you need some extra fuel partially for cooling, partially as a safety zone from detonation. You can run a blower right at the "best power" or even stoich, but your walking a tite rope with anything but a damn good F/A/S EFI setup.
You can only cool a blown gas deal with AF ratio and no intercooler so much and that it. Too rich and the power goes south and you still risk a piston. AF is not the answer. Blower guys cool it with fuel, but not with the AF. Turbos guys talk AF cooling, blower guys don't. Thats why ALL turbos except alky/E85/blow thrus should be intercooled.
I was surprised to see my procharged engine cruise so efficiently with the blow off valve open. up to approx 3800 RPM the valve was open and the engine ran in a vacuum. I'm guessing it didn't take much to spin it with the valve open. Once I mashed the go pedal the valve slammed shut and the boost jumped up I could hear the procharger whining then. If your racing then this would be a moot point
but in a lake boat I can see a great benefit.

13. Running a roots blower doesn't always take that much more fuel than N/A. It will take some horsepower to turn the blower, but when using a large blower and before it actually starts making boost, the blower will almost free-wheel and doesn't require much power. When it is being pushed and creating boost, then it starts to work. In some cases it may have to work hard and require several hundred horsepower while making boost and more horsepower.

That's why you will see electric fuel pumps being advertised they support 1300 hp N/A or 1000 hp supercharged.

I don't know about turbo's, but at one time I understood better fuel economy could be obtained with a turbo than N/A because it mixed the air and fuel better. If the Turbo is pushed, it will make a lot of power and use a lot of fuel.

14. Originally Posted by jimsplace
Running a roots blower doesn't always take that much more fuel than N/A. It will take some horsepower to turn the blower, but when using a large blower and before it actually starts making boost, the blower will almost free-wheel and doesn't require much power. When it is being pushed and creating boost, then it starts to work. In some cases it may have to work hard and require several hundred horsepower while making boost and more horsepower.

That's why you will see electric fuel pumps being advertised they support 1300 hp N/A or 1000 hp supercharged.

I don't know about turbo's, but at one time I understood better fuel economy could be obtained with a turbo than N/A because it mixed the air and fuel better. If the Turbo is pushed, it will make a lot of power and use a lot of fuel.
With EFI and reasonably low HP a turbo can be more fuel efficient than a N/A of the same HP over all. But when your making HP, it still takes fuel. The new Ford EcoBoost is a perfect example. Roughly the same HP and torque as the V8s it replaces, but when its at max torque, or max HP, it not really that much better on fuel. If it is a little better on fuel at max, its because of the DFI which allows it to run a little leaner than a standard EFI could. Its a little easier to light off a lean mixture when the fuel is shot straight across the plug. But at equal technology, any blown motor is going to use more fuel at max HP than a N/A at the same HP. That blowers is at max when the motor is at max. Its sucking power big time. If your talking cruise, thats another story. If the turbo is a draw thru, it can act as a homogenizer, but really, draw thru are pretty much a non player in most cases. There exceptions, but most turbos blow thru something and the fuel never sees the turbo.
Originally Posted by Outlaw
I was surprised to see my procharged engine cruise so efficiently with the blow off valve open. up to approx 3800 RPM the valve was open and the engine ran in a vacuum. I'm guessing it didn't take much to spin it with the valve open. Once I mashed the go pedal the valve slammed shut and the boost jumped up I could hear the procharger whining then. If your racing then this would be a moot point
but in a lake boat I can see a great benefit.
No you know why Ford had the "bypass" in the Thunderbird SC, and Whipple has the same setup for EFIs. Drastically lowers the parasitic drag in non boost conditions. If you have EFI, and do a lot of crusing, it THEE setup.

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15. Originally Posted by Outlaw
I was surprised to see my procharged engine cruise so efficiently with the blow off valve open. up to approx 3800 RPM the valve was open and the engine ran in a vacuum. I'm guessing it didn't take much to spin it with the valve open. Once I mashed the go pedal the valve slammed shut and the boost jumped up I could hear the procharger whining then. If your racing then this would be a moot point
but in a lake boat I can see a great benefit.

I'm glad you went with the race valve. Your biggest benefit will be from the longevity in the charger and engine (added fuel mileage is just an added perk). the engine and charger end up working against each other without the valve, as you overcharge the charger and in turn add stress to the engines while you prematurely wear out your charger...loose loose situation right there. have you mentioned what the max RPM you got out of it was? or did you still have some more tuning and bugs to work out?

Andrew

16. I see it mentioned but not discussed, BSFC. Or, brake specific fuel consumption. How about the core engine design and it's affect on BSFC as it relates to making power. A Honda 4 valve pentroof headed engine will have a lower BSFC than a Ford flathead, for example.
Ok gn7, you can take over from here.

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