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

[MetroMPG]

Did you try a Google Image search? A quick search revealed this gasoline turbo BSFC map:



via: Turbo and BSFC - CleanMPG Forums

Not particularly helpful without seeing the comparable non-turbo though.

In that vein, I also saw the map for the naturally aspirated version of your 1.4L engine on the gm-volt forum:



http://gm-volt.com/forum/showthread....let-Volt/page7

[jakobnev]

270g/Hph doesn't look like a reasonable sweet-spot value for a modern engine. How was this chart generated?

(If it was 270g/kWh it would be more believable.)

[richierocket]

Hi MetroMPG, yes I did the internet image search without much success. I was surprised how difficult it was to find a small turbo engine BSFC chart. I did see the Acura 2.3L turbo BSFC, but it did not apply. I really wanted a smaller displacement, economy car turbo BSFC chart. The Acura is a "luxury-performance" engine, less emphasis on economy and more on performance.

The Acura engine seems strange to me: The torque curve is very peaky(big turbo requiring more exhaust flow to get full boost?), mine is much flatter(small turbo for minimum lag and good low-end). The peak torque occurs at 4500 RPM out of a 6500 RPM redline, that's really high for a turbo engine! The efficiency island also seems too high up the load axis. The turbo should negate the pumping losses at lower loads, allowing the island to drop 20-30%(my guess). So unfortunately I didn't think this one applied.

I'm only talking about very light turbo boost -2 to +2psi, just enough to overcome the pumping loss. This also allows me to short-shift, I rarely go above 2000 RPM. One person on CleanMPG stated that you need to stay out of the boost for efficinecy, that's where I disagree, 'mild' boost recovers some of the lost energy in the exhaust.

I did also see the Volt NA engine, however in this case it doesn't apply because it is tuned to run over a very narrow operating envelope. As you know, it is not coupled to the drive wheels, so the engine control forces it to operate only along the red line on the chart.

Thanks for the effort, but it looks like there is no small turbo engine BSFC charts that are easily available.

Rich

P.S. I am in awe of you real modder guys! Awesome projects! I'm just a hack, got the grille blocker, thinking about smoothing out the nose & extending the rear spoiler over the hatch to make a longer Kammback! It takes a lot of work to make real gains...

[MetroMPG]

Roll your own: a few years ago we had a member who was working on a method of converting data logged from the OBD-II interface into a BSFC map. I had a look ... but couldn't find the thread I'm remembering.

[ever_green]

Originally Posted by MetroMPG

Did you try a Google Image search? A quick search revealed this gasoline turbo BSFC map:

http://img52.imageshack.us/img52/1001/rdxbsfc.png

via: Turbo and BSFC - CleanMPG Forums

Not particularly helpful without seeing the comparable non-turbo though.

hey metro just wanted to add that chart i made above that you linked is not actually based on real world testing. it was based on honda i-vtec BSFC charts and A/F ratio tables for my car. after some recent real world testing i have found that chart to be inaccurate. It seems that turbocharged engines, specially mine, tend to run very rich above 70% engine load and/or 3000rpm. for example at 2500rpm and 80% load my RDX hits 13:1 AFR. At 90% load it's 12:1 rich and beyond 3000rpm full rich. anyway here is a much more accurate BSFC i found (i did not make this). it basically confirmed my suspicion that moderate loads (60%) and little to no boost are best for turbo BSFC:

Mazda 2.3L turbo:


and the AFR chart:


in comparison NA hondas do not enrich mixture too much below 3500rpm, some like my subaru stay stoich no matter what unless you're operating at high engine speeds. Turbocharged engines are more eager to enrich mixture to prevent knock. little to no boost along with low RPMs are best for turbo engines because as you can see from above charts AFR is actually related to BSFC.

[richierocket]

Originally Posted by MetroMPG

Roll your own: a few years ago we had a member who was working on a method of converting data logged from the OBD-II interface into a BSFC map. I had a look ... but couldn't find the thread I'm remembering.

MetroMPG, I just had an idea on how I could gather the data for a BSFC chart. I have a Ultra-Gage that I could set up to show:
Fuel gallons/hour
RPM
Commanded AFR
Torque**
Boost Pressure

**Torque is not the real number, but I can scale it to known values

Here's where my lack of electronics knowledge and skill comes in:
I was thinking I could mount my GoPro Hero camera looking at the UG display (which updates every 1/2 second). I could record runs at different throttle settings and go back thru the videos to pull out data every few seconds. Runs in taller gears would let things change more slowly, but runs to high RPMs in higher gears could get me introuble with the law. Maybe do the runs in lower gears on steep hills.

So once I figure out how to scale the Torque number to something reasonable, I could calculate hp from Torque and RPM. I'm thinking I could have lines of constant boost pressure on the BSFC as well... I could also create an AFR plot.

I could run both 87 and 93. My intercooler is currently blocked off, so I'd have to open that up.

Lots of potential problems, any comments?

[Varn]

I have been getting the parts ready to put an industrial 1.9 cam in my 1.6 vw TD.

Any thoughts on how this might run. I don't have any data just a hunch.

[ERTW]

From an sae paper l'm currently reading:

Tuning: characterised by increased volumetric efficiency...but decreased bsfc.

Anti-tuning: characterised by decreased VE...but reduced bsfc.

Also, fuel consumption is proportionately correlated with pumping work.

I was considering disconnecting half of my engine valves, and in consideration of this info, i would double my pumping loss and potentially increase VE - hurting fuel consumption.

Late intake valve closing does wonders for efficiency - the toyota 2.5L is 37% thermally efficient - and gives the turbo lag feel. It seems that a large engine with the performance of a small one may be better than a small engine with the performance of a larger engine. Fwiw downsizing more than 30% hurts transient response, and turbo engines aren't as fuel efficient as they're marketed.

[ever_green]

Originally Posted by ERTW

Late intake valve closing does wonders for efficiency - the toyota 2.5L is 37% thermally efficient - and gives the turbo lag feel. It seems that a large engine with the performance of a small one may be better than a small engine with the performance of a larger engine. Fwiw downsizing more than 30% hurts transient response, and turbo engines aren't as fuel efficient as they're marketed.

My mom has a 2003 Acura TL with a 3.2L V6 VTEC engine and it uses less gas than my RDX with a 2.3L Atkinson cycle turbocharged engine with all the latest honda gizmos like variable valve lift and timing (intake & exhaust). Of course the turbo car is a 500lbs heavier suv with 4WD and tighter gear ratios, so it's not a fair comparison. But look at the jetta hybrid with 1.4L turbo gas that gets you 42mpg city and 48mpg highway. pretty impressive for +180ft-lbs of torque. It does better than the TDI (turbo diesel) models which is epa rated at 42 highway and 30 city.

[Varn]

I can appreciate having a higher bsfc. I want the tallest part of the curve to be at 2ooo rpm, why would having a cam set up for higher performance be a benefit. I probably never ever make my car put out more than 40 horse power or what 80 ftlbs of torque at 2700 rpm, 60 mph. I can get 55 mpg with the current set up. Could care less if the car will go 80 although it will run 95 now.

Well that is my plan I can read about it or I can try it.