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Discussion Starter #1
My last thread regarding 6.9 mileage kinda fell apart...guess I wasn't clear in my thoughts. Let me try to present this again with a bit more detail.

Mods, please feel free to delete other thread.

Nearly everyone who adds a turbo to an IDI uses a pre-fab package from Banks, ATS, etc. These packages are designed to bolt on, then turn up the fueling rate (by way of IP pressure) to utilize the newly available charged air, meanwhile making more hp with nearly stock fuel economy.

The slightly less common class are those who add a larger turbo than you might find in a kit, drop comp ratios, add fire rings, change cams, larger valves, heavier valve springs, beefed up rods, larger IPs, etc, etc. In these applications you are shooting for maximum power with no thought of fuel economy.

There is plenty of info on the above...but my question is a different one.
I am wondering if anyone has (in the interest of fuel economy) added a turbo, possibly even a smaller turbo than what comes in a Banks or ATS package, without turning up the fuel...just enough extra air to maximize the stock fueling rate. Beyond that, I was also wondering if anyone has played with timing and/or comp ratios at the stock fueling rate for maximum efficiency.
If someone out there has done that on a 6.9, I was wondering how it might have responded.

When you turn up a mechanical IP, you are changing more than the "fueling potential" that you regulate with your foot. You are increasing the fuel pressure to the mechanical injector which is opened by way of fuel pressure itself. Additional pressure will advance the timing some. That might be fine, or if a guy didn't like that, he could retard then retard the pump timing to account for the change which occurred through the pressure increase....BUT, increasing IP pressure also increases the duration of the "squirt", which causes injection to occur both before and after the ideal moment of injection from an economy standpoint. To fight that, you could possibly look into running injectors with bigger nozzles and higher opening pressures to get the extra fuel injected within the original duration, possibly at a loss of atomization depending on nozzle design....but in this case....I was never was looking to turn the fuel up to start with. :eek:

I already built my power-hauler (my '95), and did it in such a way that it has made reliable power for nearly 350,000mi now...with no end in sight. Unfortunately, diesel is no longer $1.35 a gallon like is was back when I built that truck.

The thing I'm interested in now is keeping my '95 for hauling and fun, meanwhile, taking my '84 with the 6.9, and seeing how much mileage I can squeeze out of it (not expecting much, if any power increases)

Thoughts? Experiences? "Go to hells"? :smirk:

Thanks, Phillip
 

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i really don't think you are going to see much more than 20 mpg out of a V8 diesel with todays poor quality fuel whether it is turbocharged or not.

back in the the very early 90's i was regularly getting 21-22 mpg out of my 88 4X4 on the highway. then as the fuel quality went down mileage took a hit. i am lucky to get 14 mpg on the highway now.
 

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STILL LEARNING
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I know the timing and overall condition play a big part w fuel economy.
Where the timing is set, for it is beyond me though
 

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Trailer Trash...
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The beauty of a diesel is its simplicity, and what I said inthe other thread still pertains to what you elaborated to in this thread. Obviously timing plays a huge role in both power and efficiency. That doesn't change the fact that the turbo only delivers air to burn the fuel that is induced into the engine by the pump. The best thing you can do is watch your egts and dial back the fuel, you don't have to have a turbo to do that...
 

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Discussion Starter #5
That doesn't change the fact that the turbo only delivers air to burn the fuel that is induced into the engine by the pump. The best thing you can do is watch your egts and dial back the fuel, you don't have to have a turbo to do that...
I think you may still be looking at this from a "power making" standpoint...or maybe just oversimplifying?
The beauty of turbochargers is that they utilize energy in the form of heat and pressure which would have been wasted out the tailpipe. This energy originally came from the fuel, and any of it that is lost...is wasted fuel.
I wouldn't recommend "dialing back" fuel as you are reducing pressure, thereby retarding injection timing and loosing fuel atomization.

To get maximum engine efficiency, you need to do a few things:

-Achieve as complete a fuel burn as possible. This comes down to injection timing, fuel atomization, prechamber design, compression ratio, etc.

-Maximize the mechanically limited volumetric efficiency of the engine. Maximum VE would occur when you could read no vaccum inside the cylinder on the intake stroke (assuming still naturally aspirated), and no pressure inside the cylinder on the exhaust stroke...while spinning the engine over at max rpm(not under it's own power...wouldn't want heat to be a factor yet.). To achieve this you need manifolds, ports, valves, cams, etc that allow a massive amount of flow.

-Scavenge the massive amount of wasted energy from the exhaust. This is where the turbo comes in. When running, an engine acts like a big air pump...taking in air at the intake, and blowing it out the exhaust (with the heat which was a byproduct of combustion). The turbo converts the air flow and heat on the exhaust side into pressure on the intake side which...further increases the VE of the engine.

-Cool the air charge. The cooler (more dense) the air you get into the cylinder, the higher your engine's VE will be.


Watching EGTs and staying off the right pedal...Great for hippies who have no knowledge of the actual workings of an internal combustion engine or someone who just doesn't care to modify their vehicle...but there is so much more that can be done.

I was hoping to find out how these engines responded to turbos with no fuel changes because that would give me a better idea of the stock VE/flow capabilities and combustion efficiency.
There is a lot more to efficiency than most people think.

-Phillip
 

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well, i can tell you after i put the turbo on my 88, i lost 2-3 mpg because i worked it harder.

and reducing fuel delivery does not retard timing, to retard the timing you need to move the injector pump.
 

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Trailer Trash...
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I am not oversimplifying things, you are overcomplicating them. Id give you a more in depth answer, but unfortunately all I have for the next few days is my phone to work off of, and that's a bitch. Regardless of everything you considered, it still comes down to air and fuel, and the energy that is in the amount of fuel your burning. You can tune the hell out of the pump (without "turning up" the "fuel") and add any amount of boost you wish, once you burn the fuel, the rest is wasted as parasitic loss (higher pre-combustion pressures, etc) VE is not really an issue, because its only relavent to the fuel your burning.
 

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Turning up the pump does not increase pressure, it increases flow by allowing the pumping piston to fill more. The pump makes enough pressure to open any given injector setting.
 

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Just adding a turbo should get you better fuel economy.. I would throw a turbo. cold air intake, 4' exhaust, and maybe even a IC. then see what happens. you can only do so much. If you truly are looking for fuel economy the quickest route would be to do a gear change.. get them RPMs down in the 1500 to 1600 range at 70.. that is weere you will see the biggest differance.. I mean most diesel can pull you at 70 in the 1200 to 1500 range.

Let's see, with you ZF5 and 3.55 gears and 235-85R16 tire you will be around [email protected] RPMs now trow a gear vender on there. and you will see [email protected] RPMs. NOW you are talking fuel ecomomy gains i mean you should get 20 easy and 25 should be quit double.. PLUS you can still tow EVEN better then stock gearing!!!!!!.

just some food for thought
 

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Need more power!!
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Just adding a turbo should get you better fuel economy.. I would throw a turbo. cold air intake, 4' exhaust, and maybe even a IC. then see what happens. you can only do so much. If you truly are looking for fuel economy the quickest route would be to do a gear change.. get them RPMs down in the 1500 to 1600 range at 70.. that is weere you will see the biggest differance.. I mean most diesel can pull you at 70 in the 1200 to 1500 range.

Let's see, with you ZF5 and 3.55 gears and 235-85R16 tire you will be around [email protected] RPMs now trow a gear vender on there. and you will see [email protected] RPMs. NOW you are talking fuel ecomomy gains i mean you should get 20 easy and 25 should be quit double.. PLUS you can still tow EVEN better then stock gearing!!!!!!.

just some food for thought
:poke:

He is not talking about the 97 Stroke.... He is talking about the 84.
 

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:poke:

He is not talking about the 97 Stroke.... He is talking about the 84.
I know.. BUT the same thing applys for the 6.9L and 7.3L IDI's


Besides, How can you make a turbocharged engine that already has a Turbo into a turbocherged engine??? :poke:
 

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this are not the same as the powerstrokes you cant even compare them. yes you can but it will not improve mileage that much if really at all, but that is what i have seen with the 6 or 7 of the idis that i have owned and modified
 

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this are not the same as the powerstrokes you cant even compare them. yes you can but it will not improve mileage that much if really at all, but that is what i have seen with the 6 or 7 of the idis that i have owned and modified
Try it you might be suprised... i know people that have done it and it works!!! Quite well to!!
 
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