" Aerodynamics doesn't begin to have an effect until 60 MPH "

[racprops]

Originally Posted by freebeard

For those that may confuse as easily as I; the old thread in question is the one raceprops started in 2018.

I have not seen that one brought up here at all.

Thanks for reminding me.

Rich

[Isaac Zachary]

I made a terrible graph but it kind of explains the point.

If you're only improving aero your engine RPM's will be exactly the same, but your load will be lower. Unless you're already driving at full throttle to maintain your speed, chances are you will move away from higher brake specific fuel consumption efficiency. In other words, you will use less fuel, but your engine will become slightly less efficient because internal combustion engines in general are more efficient at higher loads, at least up until they start enriching the AFR.

Ideally, you want to lower aerodynamic drag and rolling resistance as much as possible and then measure how much power you really need to maintain your desired speed on your desired road. Then size the engine so the amout of power needed can be placed as close to max BSFC efficiency (which would be a very small engine) all the while making your engine big enough so it's not going to dog out when you do need the power. The more varied your driving conditions (e.g. hills, etc.) the bigger the engine you'll want. Then also gear the transmission to put those RPMs as close to best BSFC efficiency.

[racprops]

OK So it seems the only way to figure my engines BSFC efficiency will be by testing:

To calculate BSFC, use the formula

B S F C = r P {\displaystyle BSFC={\frac {r}{P}}} BSFC={\frac {r}{P}}

where:

r {\displaystyle r} r is the fuel consumption rate in grams per second (g/s)
P {\displaystyle P} P is the power produced in watts where P = τ ω {\displaystyle P=\tau \omega } P = \tau \omega (W)

ω {\displaystyle \omega } \omega is the engine speed in radians per second (rad/s)
τ {\displaystyle \tau } \tau is the engine torque in newton metres (N⋅m)

The above values of r, ω {\displaystyle \omega } \omega , and τ {\displaystyle \tau } \tau may be readily measured by instrumentation with an engine mounted in a test stand and a load applied to the running engine. The resulting units of BSFC are grams per joule (g/J)

Commonly BSFC is expressed in units of grams per kilowatt-hour (g/(kW⋅h)). The conversion factor is as follows:

BSFC [g/(kW⋅h)] = BSFC [g/J] × (3.6 × 106)

The conversion between metric and imperial units is:

BSFC [g/(kW⋅h)] = BSFC [lb/(hp⋅h)] × 608.277
BSFC [lb/(hp⋅h)] = BSFC [g/(kW⋅h)] × 0.001644


With my 03 Ford Explorer's 4.6 there may be a readout of its engine's BSFC efficiency but it has to be of the Explorer as they are reported to have special intake manifolds and other systems to promote high torque at 1500RPMs. So I believe they are not the same as say a 03 P71's 4.6.

As as for my 383 with all its special features I build in and how I built it for a torque peek at 2000 and at 3000 the only way will be on the road.

I have found all engine and all car dynos DO NOT read torque and torque below 2500RPMs and only at Full throttle.

My engines will be running at 1500 to 2000RPMs at as little throttle as possible.

So the only way to figure anything out will to fully gauge my SUV and Van and fully test its MPG at the speeds I will want to drive is to record its MPG and at Various MPH.

I believe I can do this, with the 2000 Mercury I used a section of the I17 Freeway, which showed on GPS a slight incline north, and my tests show a loss of 1 MPG northbound and a gain of 2 MPG southbound.

I would make full up and down this strip at a cruse controlled speed of 65MPH and on each run changed it's A/F ratio by 1% from 4.7 to 7.0 and noted that the cars MPG peeked at 16.4 and dropped with any higher ratios.

I also mentored the engines exhaust gas temperatures during these tests and saw no real changes.

Rich

PS and with all manufactured engines every engine is NOT the same, so as the old joke goes: YOUR MPG may be different.

[Piotrsko]

how do you intend to accurately measure fuel burn? The sensors I have seen seem to be +/- 20% and most demonstrators use a precisely calibrated fuel container and weigh the fuel at a controlled temperature

I suppose if you have a calibrated fuel flow map for injectors, accurate pressure measurement and record of the controller output, you could use that, maybe.

[racprops]

Originally Posted by Piotrsko

how do you intend to accurately measure fuel burn? The sensors I have seen seem to be +/- 20% and most demonstrators use a precisely calibrated fuel container and weigh the fuel at a controlled temperature

I suppose if you have a calibrated fuel flow map for injectors, accurate pressure measurement and record of the controller output, you could use that, maybe.

I use the following: A MPGunio, a ScanguageII and runs from Phoenix, AZ to Blythe, CA is 150 miles (241 km). a 02 hours 20 minutes drive by car.

So a fullup to three kick offs by the gas pump handle, and then doing the math.

A full test would be a round trip both ways and a return to the very same pump.

As I am only interested in broad strokes not each 1/10th of a MPG, more in rather I am seeing 5 to 15 MPG changes these are accurate enough for my needs.

Once I am sure my Two MPG gauges are reading close and just about the same as the road trip, I can do short runs up and down I17 near my home working to get a good improvement and if one really shows up, I can do the run from Phoenix, AZ to Blythe, CA to really prove it.

Rich

[Piotrsko]

For broad changes, I grok your method, but eventually you will end up in a decreasing pattern of differences. So at that point you are finished making modifications?

[freebeard]

When I looked into this, it appeared the best solution was a vortex street flowmeter. Here's DDG:

https://www.sike-flowmeter.com › vortex-flowmeter_p0013.html
LUGB type vortex flowmeter is according to the principle of Carmen (Karman vortex street measuring gas, steam or the volume of liquid flow, the volume of the standard condition or volume flow to mass flow meter. And can be used as flow transducer is applied to automatic control system.V ortex flowmeter can be divided according to function name ...
Products‧Calibration‧FAQ‧Contact Us‧Parshall Trough‧About Us

Vortex Flow Meters | Badger Meter
https://www.badgermeter.com › products › meters › vortex-flow-meters › ?bu=industrial
Vortex flow meters are suitable for measuring steam, as well as a variety of liquids and gases. High Levels of Sensitivity. Superior Performance at Low Flow Rates. Vortex flow meters offer many benefits in flow measurement applications, including simple installation and a wide turndown range. Advanced Sensitivity.

With a Beetle having a gas gauge if you're lucky and a speedometer driven by an undersized left front tire, I use two clicks on the pump and Google Maps.

[aerohead]

Originally Posted by racprops

I use the following: A MPGunio, a ScanguageII and runs from Phoenix, AZ to Blythe, CA is 150 miles (241 km). a 02 hours 20 minutes drive by car.

So a fullup to three kick offs by the gas pump handle, and then doing the math.

A full test would be a round trip both ways and a return to the very same pump.

As I am only interested in broad strokes not each 1/10th of a MPG, more in rather I am seeing 5 to 15 MPG changes these are accurate enough for my needs.

Once I am sure my Two MPG gauges are reading close and just about the same as the road trip, I can do short runs up and down I17 near my home working to get a good improvement and if one really shows up, I can do the run from Phoenix, AZ to Blythe, CA to really prove it.

Rich

1) Same pump, parked in same direction, same day, same 3-clicks, may be as accurate as a consumer is likely to experience.
2) Fuel has a thermal expansion coefficient published by the API.
3) Some stations actually have temperature sensors for each storage tank. Just ask.
4) A 6-inch, long-stem, stainless steel thermometer can be placed right into the filler spout, holding the detent open, if you'll actually top-off the tank to a chosen visual reference mark.
5) This will give you some idea if the fuel temp has varied in volume from fill to fill. Especially with above-ground storage tanks.
6) Fuel delivered from a refinery will have residual process heat which could skew the 'volume.'( famous at Allsup's Convenience Store, Cloudcroft, New Mexico, delivery from Artesia, New Mexico's refinery )
7) A good reason why university teams use an auxiliary tank, of a known mass of fuel for all testing ( virtually impossible for us, since EFI has fuel continually returning to the tank from the common rail )
8) We do what we can.

[Piotrsko]

State of Nevada has mandated temperature compensated fuel pumps, perhaps many others, so that the fuel delivered is accurate at any temperature. If you fuel in Phoenix in the morning it should be somewhat colder by a couple of degrees than the post trip consumption/level. The only practical way to determine useage in the existing system is to have a visual mark or use an instant read thermometer to detect the temperature and fuel level then calculate quantity in the tank. Then there's burping and thermal expansion during the drive.

Could be off as much as a gallon like on my F250