Turbo gas mileage...
01-09-2009, 07:27 PM
#41
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All I was saying about the big rigs is that they could use SC's, but instead they use turbos, because it makes use of energy that would otherwise be wasted. But you're right, a semi without a turbo is a turd. 
The engine would have to be ginormous.
At different conditions, a smaller FI engine will be more efficient than a larger NA engine, given the same max power output. They may make the same power, but the curves will be very different looking.
At WOT or in boost, for example, the smaller FI engine will be less efficient as seen by the higher BSFC (lb/hp-hr) required to make the same power as the bigger engine. To illustrate, the smaller FI engine will need a lower AFR to make the same power as the bigger NA engine. The air consumed should be the same, but the fuel used to keep parts happy will be different.
I think what Turbo 6.0 is saying, is that at part throttle and cruising is where the FI engine can have an advantage, because it's being somewhat feed the air.
I can't say for sure if this is true, but I'd have to guess that in order for this to be true...the SC or turbo would have to push more air that it would need to consume if it were NA. I'm not saying it needs to be in boost, but NA at 70mph lets say the load on the engine makes it pull 10in-Hg. With FI at 70mph it only pulls 8in-Hg, since it doesn't have to work as hard to get air. I'm just spit balling here.
Here's some more fuel for the fire. Something I've noticed when swaping turbos, cams etc. is that a vacuum/boost referenced FPR increases fuel with less vacuum. So...if an engine is being fed air at cruise and the gauge reads less vacuum, the FP has gone up. Therefore, fuel consumption should go up as well.
The engine would have to be ginormous.At different conditions, a smaller FI engine will be more efficient than a larger NA engine, given the same max power output. They may make the same power, but the curves will be very different looking.
At WOT or in boost, for example, the smaller FI engine will be less efficient as seen by the higher BSFC (lb/hp-hr) required to make the same power as the bigger engine. To illustrate, the smaller FI engine will need a lower AFR to make the same power as the bigger NA engine. The air consumed should be the same, but the fuel used to keep parts happy will be different.
I think what Turbo 6.0 is saying, is that at part throttle and cruising is where the FI engine can have an advantage, because it's being somewhat feed the air.
I can't say for sure if this is true, but I'd have to guess that in order for this to be true...the SC or turbo would have to push more air that it would need to consume if it were NA. I'm not saying it needs to be in boost, but NA at 70mph lets say the load on the engine makes it pull 10in-Hg. With FI at 70mph it only pulls 8in-Hg, since it doesn't have to work as hard to get air. I'm just spit balling here.
Here's some more fuel for the fire. Something I've noticed when swaping turbos, cams etc. is that a vacuum/boost referenced FPR increases fuel with less vacuum. So...if an engine is being fed air at cruise and the gauge reads less vacuum, the FP has gone up. Therefore, fuel consumption should go up as well.
01-09-2009, 07:47 PM
#42
01-09-2009, 07:49 PM
#43
when I am on the freeway cruising my motor makes less vaccum now with the turbo than it did NA. That tells me that there is more air available when the throttle opens. IE the motor doesn't have to work as hard to get the air thus it is more efficent. I'm not saying I think this is the sole reason for the increased gas mileage but I do think that it is a big factor.
01-09-2009, 07:51 PM
#44
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You can e-mail me the logs and info if you choose too..
At
calliedusty@sbcglobal.net
Thanks
01-09-2009, 07:53 PM
#45
It is not pushing air into the motor it is only making the air more readily avaliable. It is kind of like a restrictive air intake verses a free flowing one. I do understand that you would have to retune the vehicle to make the most of the free flowing intake but it is not the only thing making the difference. You could tune your *** off on a restrictive intake and not get the same gains that you could with a free flowing intake. It's the same principal with a turbo or blower or even ram air.
01-09-2009, 07:56 PM
#46
I wasn't going to bring it up, but since someone already did, let's talk efficiency of a turbo engine vs. an NA engine.
About 1/3 of the engine's energy goes to turning the crank. Another 1/3 is lost to heat (goes into the cooling system), and another 1/3 goes out the tailpipe. A turbo engine utilizes some of that otherwise lost energy, thus making it more efficient. As such, it has the ability to get better mpg's. Look at a big rig. They wouldn't be running turbos on them if they weren't efficient. 5-8mpg's of diesel for thousands of miles a week is a lot of coin.
About 1/3 of the engine's energy goes to turning the crank. Another 1/3 is lost to heat (goes into the cooling system), and another 1/3 goes out the tailpipe. A turbo engine utilizes some of that otherwise lost energy, thus making it more efficient. As such, it has the ability to get better mpg's. Look at a big rig. They wouldn't be running turbos on them if they weren't efficient. 5-8mpg's of diesel for thousands of miles a week is a lot of coin.
01-09-2009, 07:56 PM
#47
What pressure ratios are you seeing at full boost? can you send me a few logs for comparison sake? Not sure if you figured out I'm the guy who contacted Joe the other day about a bigger turbo for my truck....
You can e-mail me the logs and info if you choose too..
At
calliedusty@sbcglobal.net
Thanks
You can e-mail me the logs and info if you choose too..
At
calliedusty@sbcglobal.net
Thanks
01-09-2009, 08:28 PM
#49
It is not pushing air into the motor it is only making the air more readily avaliable. It is kind of like a restrictive air intake verses a free flowing one. I do understand that you would have to retune the vehicle to make the most of the free flowing intake but it is not the only thing making the difference. You could tune your *** off on a restrictive intake and not get the same gains that you could with a free flowing intake. It's the same principal with a turbo or blower or even ram air.