The BSFC chart thread (post 'em if you got 'em)

[MetroMPG]

Had a suggestion to post BSFC charts for various vehicles in one place. If you've got one, post it in this thread. I'll add an index in this first post if it gets long.

--

Geo/Suzuki 1.0L SI engine

Thanks to tasdrouille who posted a link to a fuzzy - and the only - bsfc chart I've yet seen for the Suzuki/Geo 1.0L, non-XFi engine (judging by power rating):

The original, fuzzy image:

Cleaned up image. Note: I "best guessed" a few digits:

Note that peak torque for this engine is listed as:

Torque(lb/ft) @ RPM: 58 @ 3,300 (Non-XFi Models, XFi not listed - source)

And 58 lb/ft = 78.6 Nm (calculator)

[Straight-3]

Ok.
What I'm getting: Driving at WOT from about 2600 to 3600 rpm will yeild the minimum fuel used for power produced.

What I'm wondern: Why is there so much data on the graph? Like islands instead of just a line, theres seems to be 8-10 points plotted for every rpm from 1100 to 5000.

[Straight-3]

Wait a sec... the aliens were just communicating with my brain... Each line is just fuel consumption for a given torque and rpm, throttle position is not represented on this graph. I think.

[cfg83]

Hello -

Here's one for my Saturn 1.9 liter DOHC engine :



saturn_dohc_bsfc.jpg

I got it from here :

Fuzzy Pareto Frontiers in Multidisciplinary System Architecture Analysis
http://web.mit.edu/deweck/www/PDF_ar...-2004-4553.pdf

CarloSW2

[tasdrouille]

Here's one illustrating NA vs Turbocharged for a given engine. It clearly shows how a turbocharger can lead to better FE as you can downsize the engine and get the same power output, but you extend the bsfc sweet spot to lower loads vs the bigger engine.

[MetroMPG]

Originally Posted by cfg83

Here's one for my Saturn 1.9 liter DOHC engine

cfg, do you know what the line is at the top of your chart with the points marked on it? The original Geo engine chart appears to have a similar line.

[jwxr7]

Here is a chart for a 2001 GM vortech 4.3l v-6. It shows both, the truck and marine applications.

Brake Specific Fuel Consumption
The engine brake specific fuel consumption (bsfc) shall be as follows:
1. The engines nominal brake specific fuel consumption point on a W.O.T. curve is shown in
table 6.3 -I.
2. The engine nominal specific fuel consumption shown in table 7.3 -I are for an operating range
between peak torque and maximum power at full load.
3. The engines best part throttle bsfc (on a fuel map) is shown in table 7.3 -I.

Table 6.3 L35 V6 4.3L Engine BSFC

rpm truck marine units
800 0.529 0.495 lb./BHP-Hr
1200 0.521 0.478 lb./BHP-Hr
1600 0.484 0.481 lb./BHP-Hr
2000 0.470 0.471 lb./BHP-Hr
2400 0.471 0.466 lb./BHP-Hr
2800 0.469 0.472 lb./BHP-Hr
3200 0.478 0.458 lb./BHP-Hr
3600 0.483 0.452 lb./BHP-Hr
4000 0.500 0.460 lb./BHP-Hr
4400 0.525 0.479 lb./BHP-Hr
4800 0.532 0.506 lb./BHP-Hr
5200 0.556 0.550 lb./BHP-Hr

[cfg83]

MetroMPG -

Originally Posted by MetroMPG

cfg, do you know what the line is at the top of your chart with the points marked on it? The original Geo engine chart appears to have a similar line.

Nope, I don't speak BSFC. It's just a topo-map to me. I'm sure someone else will pipe up and say what it is.

CarloSW2

[tasdrouille]

I always thought it was simply the torque curve at WOT through the whole range. I could be mistaken though.

[boxchain]

I agree that those look like torque curves...

So this is a load vs speed graph that maps fuel/power gradients ...the way I'm reading them is that the sweet spot for acceleration is about 1/2 to 2/3 throttle (y-axis...load really) at 1500-3500 rpm, depending on what your torque curve looks like.

[MetroMPG]

If that line does show torque at WOT, that may make it incredibly useful: could you not essentially use it to extrapolate what throttle/pedal position to use to get the engine closest to the sweet spot at a given RPM?

EG. in the Saturn chart, 7/9 throttle @ 2000 RPM looks like it would put you squarely in the 250 g/kWh island.

Of course it doesn't work quite that simply, because the engine doesn't "idle" at 2000 RPM ("0/9ths"), so you'd likely have to factor in the amount of pedal required to get there with no load on the engine.

[tputus]

Retarded timing? Or does EGR matter that much efficiency wise?

@ MetroMPG
Most gas cars have a very nonlinear accelerator travel vs. torque output response. How a bout measuring acceleration vs pedal position at lower speeds with the ScanGauge? Maybe up a hill?

[MetroMPG]

Re: efficiency reduction @ higher RPM - I'd guess that increasing internal friction also plays a role. Power required to overcome friction is an exponential relationship. Just a thought.

Good point on tps vs. torque.

[Daox]

Timing changes and pushing the engine into open loop causing fuel enrichment I would think is what causes the drop off at the extremely high loads.

[Duffman]

Originally Posted by tasdrouille

I always thought it was simply the torque curve at WOT through the whole range. I could be mistaken though.

Yes, min BSFC should be at the same RPM as peak torque as is in this case.
I agree.

[AXMonster]

What you need to do with the plots now is calculate the engine torque at various engine speeds in all gears, then plot the results over the BSFC plot to give the road curves Vs BSFC.
Then you have all you need to drive at theose BSFC points you choose

If you don't have any efficiencies then calculating the engine torques for road speeds may be a little difficult, but allowing 23% for drivetrain losses is a typical figure.
A more reliable method of getting the drive train losses is to stick the car on a roalling road and do a motored run in neutral to actually measure the power it takes to achieve the road speeds.

[elhigh]

I'd love to see one of these for the Toyota 22r - then I'd know for sure whether regearing my rearend is a good idea. Right now, it's just a feeling that the engine could be turning a lot slower and get the job done.

[fabrio.]

I am sercing that one of the tigra, engine X14XE, but I, do not succeed to find it.
you, can help me?

[s2man]

Originally Posted by MetroMPG

If that line does show torque at WOT, that may make it incredibly useful: could you not essentially use it to extrapolate what throttle/pedal position to use to get the engine closest to the sweet spot at a given RPM?

EG. in the Saturn chart, 7/9 throttle @ 2000 RPM looks like it would put you squarely in the 250 g/kWh island.

That's what I was trying to say in the shift timing thread. 7/9 = 77% of max torque (or load). Examining a bunch BSFC maps, and measuring the extents and center of the peak efficiency island, I found the average center point to be 72% of max load. Hence the question; Can we believe the LOD output on the scangauge as a good indication of engine load?

[fabrio.]

sorry, it is very difficult for me to understand that your has write and in the same manner, it is very difficult for me write to you that one I think...in Italian no problem, but an English I can only try

For an correctly reading of BSFC, the map it must be without the torque value, but with the % of PME max(pressure, average real).

The map is created put the engine in the braked dyno.
the BSFC it is a consguence of vary factors: engine respiation, friction and AFR.
The engine respiration it is defined by cams phases, valves diameters, intake and exhaust tubes lengs and diameters, resonace and pulsation phenomena.
When the respiration is at the optimum, the respiration friction losses it is at the minimum, obviously at open full throttle.
The engine friction loss increase with the engine revolution, and the AFR it is an other trouble factor.
When we interpolate all factor then obtain the BSFC map.

For to go the engine in the optimal fuel economy (in this case by 250 gHP/H), it is necessry the needed load.
In normal operation, in flat road, in the last gear and without acceleration, it is impossible go to optimal area of BSFC.
Only way, it is to decrease the engine torque available the same rpm and car load throoughout AFR modification.
This, does not have effect on the friction loss and on the volumetric efficient, but only on the PME
So, we can free-moving the engine load (point in the BSFC map) with the same engine torque output
I am understandable?