Fuel efficiency

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Wesman07
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Fuel efficiency

Post #1 by Wesman07 » Wed Apr 26, 2017 10:53 pm

Will tubrocharging the 300 motors acutually add fuel efficiency?

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MechRick
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Re: Fuel efficiency

Post #2 by MechRick » Thu Apr 27, 2017 3:10 pm

It can, if the turbo is sized correctly.
The exhaust gasses are still expanding as they leave the exhaust ports. If the turbo is small enough that there is a small amount of boost during cruise, some of that wasted energy can be recycled. I saw 2-2.5 mpg on a 4 cyl Fox body. I imagine 1-1.5 mpg is possible in a truck.
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block, stock pistons, ARP rod bolts
Stock cam installed straight up (aluminum cam gear)
Hedman header, full mandrel bent duals, crossover, super turbos
viewtopic.php?f=2&t=73244
Bronco II with a 2.3L swap viewtopic.php?f=13&t=72863

Wesman07
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Re: Fuel efficiency

Post #3 by Wesman07 » Sat Apr 29, 2017 12:56 am

Ok so fuel efficiency can be gained. I would assume the working rpm would stay the same.

Can a simple set up be reliable? Say a ms controller, wideband O2, turbo and injectors?

Would it be cost effective as far as hp/dollar? Let's say the build would break the 200hp, 300lbs bench mark.

J.R.
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Re: Fuel efficiency

Post #4 by J.R. » Sat Apr 29, 2017 3:15 am

Remembering a long ago answer from the late Ak Miller, re. a MPG increase in turbocharged & carbureted Ford 300 engines: NO for a blow-thru system, but potentially, YES, for a properly executed draw-thru system, due primarily to increased induction stream turbulance, i.e. better fuel atomization. Ak also threw down the caveat, that most turbo owners probably won't see any increase in fuel mileage, because the newfound power available with turbocharging would be just too tempting!

As to EFI-turbo... probably more like the draw-thru turbo-carb jobs. Sad to say, the last chat I had with Ak, when we discussed his 'enjoyment' of the power in his then fairly new (1996?) twin-turbo EFI 4.9L Ford F150, the subject of fuel efficiency did not come up. As were quite a few of Ak's creations, that setup was a "dual fuel" (gasoline/propane) induction system, undoubtedly with efficiency as one consideration, but primarily done as an even lesser-polluting "workaround" that could meet California's strict emissions laws, and still utilize twin turbos on a street legal vehicle.(?) OTOH Ak may have registered it as an experimental or manufacturer's developmental vehicle.(?)

J.R.
SoCal

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MechRick
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Re: Fuel efficiency

Post #5 by MechRick » Sat Apr 29, 2017 1:26 pm

Wesman07 wrote:Can a simple set up be reliable?


Absolutely. I built mine as a daily driver. It was not a max power effort. The turbo was a junkyard unit that I rebuilt. I even removed the stock Ford oil cooler as I felt it was not necessary for stop light sprints in a light car. MS1 with a wideband. The most expensive component was the fancy Wiseco pistons needed for a Ranger crank with the shorter Ford 2.3 rods.

J.R. wrote:NO for a blow-thru system


This was my experience. Carbs cannot control the fuel precisely enough to prevent melting pistons *and* deliver MPG. Best I ever got out of my blow-through Pinto was 23 mpg.

With my Mustangs, 25 MPG was typical of a 2.3 N/A. My turbo setup got 27 consistently, with a couple tanks at 28 MPG. This was back and forth to work with the cruise set at 70 MPH.

I once removed the turbo to intake tube with the engine running. This was after extensive tuning, so I know it was close. At 1000-1500 RPM the engine was suddenly *very* lean. I worked out that the MAP sensor was reading less positive pressure without the turbo connected, and the engine was using more air.

What this means (I think) is the engine is ingesting less air for a given RPM with the turbo functioning. Less air means it needs less fuel for the same output as N/A. Not very scientific, but I did back it up with hard numbers.
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block, stock pistons, ARP rod bolts
Stock cam installed straight up (aluminum cam gear)
Hedman header, full mandrel bent duals, crossover, super turbos
viewtopic.php?f=2&t=73244
Bronco II with a 2.3L swap viewtopic.php?f=13&t=72863

pmuller9
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Re: Fuel efficiency

Post #6 by pmuller9 » Sat Apr 29, 2017 10:08 pm

MechRick wrote:I once removed the turbo to intake tube with the engine running. This was after extensive tuning, so I know it was close. At 1000-1500 RPM the engine was suddenly *very* lean. I worked out that the MAP sensor was reading less positive pressure without the turbo connected, and the engine was using more air.

What this means (I think) is the engine is ingesting less air for a given RPM with the turbo functioning. Less air means it needs less fuel for the same output as N/A. Not very scientific, but I did back it up with hard numbers.

What you saw when you disconnected the turbo outlet tube is correct. Less manifold pressure more throttle for same engine output.
The reason is slightly different

Air and air fuel ratio is measured by weight not CFM.
Example: 400 cfm at standard atmospheric pressure (no boost) is equivalent by weight to 200 cfm at 2 atmospheres or 14.7 lbs of boost providing both air temperatures are the same. (think intercooler)
When you pulled the tube and the manifold pressure dropped it needed more air volume to provide the same amount of air by weight.
A/F ratio should have stayed the same.

Where you gain fuel mileage when turbocharging is by reducing the pumping losses during the intake stroke.

Looking at it from a gauge pressure perspective.
Normally the engine must draw the intake charge into the cylinder by working against intake manifold vacuum. That takes energy.
Under light loads the turbo reduces intake manifold vacuum which reduces pumping losses.
As the engine load increases and the intake manifold sees positive pressure or boost, the piston is driven during the intake stroke which increases engine power.

As you previously pointed out this energy is extracted from the blow down portion of the exhaust cycle which would have been wasted otherwise.
I would like to add that blow down is complete just after BDC and any residual pressure left becomes a pumping loss as the piston moves towards TDC at the end of the exhaust stroke.
Exhaust system design and Turbo turbine housing A/R selection is important to minimize exhaust cycle pumping losses.

Wesman07 wrote:Ok so fuel efficiency can be gained. I would assume the working rpm would stay the same.

The working rpm can be lowered since the turbo can increase the torque in the lower rpm range

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MechRick
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Re: Fuel efficiency

Post #7 by MechRick » Sun Apr 30, 2017 11:37 am

pmuller9 wrote:A/F ratio should have stayed the same.


That's the part that convinces me the efficiency of the engine is improving with the turbo in place. Speed density is fueling by two parameters, RPM and MAP. When I removed the turbo outlet tube and the engine went lean, the only possible explanation is the engine is using more air for a given MAP and RPM. You are correct in stating the throttle would have to be opened more to achieve the same power output. It would also have to be using more air (and fuel). The reduction in pumping loss is allowing the engine to do this.

As an aside, I've noticed over the last few years an increase in vacuum pumps on new cars. With VVT electronic throttles and direct injection, manifold vacuum is dropping to the point that there is not enough vacuum left to operate the brake booster.
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block, stock pistons, ARP rod bolts
Stock cam installed straight up (aluminum cam gear)
Hedman header, full mandrel bent duals, crossover, super turbos
viewtopic.php?f=2&t=73244
Bronco II with a 2.3L swap viewtopic.php?f=13&t=72863

pmuller9
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Location: Columbus, Indiana

Re: Fuel efficiency

Post #8 by pmuller9 » Sun Apr 30, 2017 1:48 pm

MechRick wrote:
pmuller9 wrote:A/F ratio should have stayed the same.


That's the part that convinces me the efficiency of the engine is improving with the turbo in place. Speed density is fueling by two parameters, RPM and MAP. When I removed the turbo outlet tube and the engine went lean, the only possible explanation is the engine is using more air for a given MAP and RPM.


This is my thoughts so help me out.
Once the turbo outlet tube was removed, the MS1 would be operating in the lower section (less kPa) of the speed density map since the intake manifold was seeing less pressure.
In most cases those VE numbers represent a leaner air fuel ratio than the higher kPa numbers.
Correct me if I'm wrong but I think that is why the A/R ratio went leaner with less intake manifold density.

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MechRick
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Re: Fuel efficiency

Post #9 by MechRick » Sun Apr 30, 2017 8:41 pm

I think you are right. We can further postulate that if the turbo pipe was removed while the engine was at say, 1500 RPM, the RPM would drop a bit. It would be a good test.

I believe the engine would need more throttle to maintain the same output.
1994 F150, 4.9L/ZF 5 speed, C-Vic police driveshaft
EFI head w/mild port work, 3 angle valve job
1996 long block, stock pistons, ARP rod bolts
Stock cam installed straight up (aluminum cam gear)
Hedman header, full mandrel bent duals, crossover, super turbos
viewtopic.php?f=2&t=73244
Bronco II with a 2.3L swap viewtopic.php?f=13&t=72863

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