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

[Vekke]

Played aroud with 1.2TDI ANY map in my Audi A8 project with various Cd and gear ratios:


From that you can see why you need to play with taller gear ratios when you lower your cars drag!

[ausias]

Originally Posted by Vekke

Played aroud with 1.2TDI ANY map in my Audi A8 project with various Cd and gear ratios:


From that you can see why you need to play with taller gear ratios when you lower your cars drag!

thanks for posting this map, it seemps interesting to do the maths also with 1.6L 4 cil engines that they seem to share engeenering. I thing also that it is importatn to think that the sweet spot of low bsfc will move depending on wich turbo you fit.

where did this map came from?

your chart remember me thaat of 2.0 L VW diesel engine with 140 hp, too big turbo for fuel economy at low speeds.



You are facing a big challenge even with such a big car.

[Vekke]

Lupo 3L bsfc Original map is from Dieselmotorentechnik 2000, expert Verlag book. not available on the internet. Stock lupo peak efficiency is point 205g/kwh @ 2250 rpm

The map with power curves is from from this study but it has been modified to simulate 0.8 liter 3 cylinder diesel. http://e-collection.library.ethz.ch/...h-23866-02.pdf

I have multiplied those figures so 40 kW x1,125->45 kW lines.

BSFC map should not change much at low power figures and rpm as I am not needing that much power Without a turbo the 1.2 should give about 42 hp and 84Nm when comparing to 1.9 SDI specs. The 1.9 SDI can produce 15 kW at 1500 rpm -> 1.2 (T)DI no turbo action is 9,4 Kw that is much more than I am needing at 12,25 Hp at 1670 RPM without any boost at all. 1.9 SDI can produce about 20 kW at 1700RPM so 1.2 (T)DI can produce 12,6 kW.

1.9 SDI is more efficient in steady speed driving (highway cycle) than the 1.9 TDI. Making that boost wastes diesel if you are not needing it in the first place!

[ausias]

Originally Posted by Vekke

...
1.9 SDI is more efficient in steady speed driving (highway cycle) than the 1.9 TDI. Making that boost wastes diesel if you are not needing it in the first place!

i'll read the very interesting study that you attached.

but i'm not sure that you are right.
I did some homemade volumetric efficiency assessment with obdii data logging. first thing i noticed, SDI engine hasn't a MAF. no straight comparision could be done at ease.

Then I found that the smoke map on the SDI was limiting fuel injection below "torque curve", so FSI style inejction control on the SDI has some not accessible obdii data figures of air mg/stroke but I'm guessing that air intake temperature and somekind of pressure on the big air intake is used to evaluate mass of air.

Because i Found the same smoke map on SDI and 110 hp engine I think that stock SDI doesn't has the expected better performance, because it was too much difference on fuel injection. maybe a dyno and some sensor will help.

But I guess that if vnt turbo engine vol.efi is in the range of 80 to 95% in my 1.9 VNT15 geared and no load on the throttle and even higher in a 1.9 TDI PD with KP39 turbo, i'm not sure why with the same smoke limiter map the SDI will be capable of doing +30% more torque and power if the same efficiency and if the same injection quantity per stroke was burnt.

SDI engine had 2 gear ratios both of them shorter than that TDI ones in the same platform, so they have almost the same on road European cycle fuel consumption or a little lower. So you are right that it was less engine losses involved but not the expected ones I think.
But Stock SDI air intake is too different to that of any TDI engines from 90 to 160 hp I've seen or also the exhaust is different. Intake and Exhaust engeenering are too realeted to performance on an atmospheric.

I did the test with maybe too old engines.
It seems to me that 1.9 SDI it was capable of doing a lot of more torque and power. 125 Nm and 64 hp seem to me someking of low performance compared with the 1.9 VE TDI (90 ALH or 110 like... AFN/AHF/ASV). but if smoke limiter is already cutting the injection this means there is not air enough to tune the engine.


According to data I found SDI road 4.1L/100km with 39.6 km/h/1000rpm 5th gear
and TDI road 4.1 L/100km with 47.8 km/h/1000rpm 5th gear.

So maybe it is an amazing 20% better efficiency. (47.8/39.6 =120% o 17% less fuel consumption tith TDI gear fitted to SDI engine.)
Skoda Fabia 1.9 SDI Comfort ficha técnica, prestaciones, consumos, dimensiones de este coche - km77
Skoda Fabia 1.9 TDI Elegance ficha técnica, prestaciones, consumos, dimensiones de este coche - km77

Do you think a 20% difference due to engine bsfc is realistic?

[Vekke]

On my lupo 2l ecu file there was no boost at all up to 140 km/h speeds as it was not needed. You need only boost when you have to accelerate and stress the engine more to get better efficiency.

It all comes down to air to fuel ratio. In a diesel if your AFR is over 18 you are pretty much burning all fuel you inject. You can inject more diesel to get little bit more power but then you are wasting diesel as not all of it is not burnt.

Why there are turbos then is related to particle emissions as you can control the EGR flow direction if you have higher back pressure than boost pressure is. And yes egr system wastes fuel also but it does reduce some particle emissions.

1.4 SD engine can produce 48 hp and 82Nm, but that engine was used in the 1980s to early 1990s. My 1.2 TDI is a pump duse engine and I can control the injection more accurately and jave higher injection pressures.

if you compare the 1.9 TDI and SDI you need to use its bsfc map:


Take for example reference point from 10 hp line. thats about 2000 rpm in TDI
SDI 10hp@2400rpm-> 400g/kwh->21% efficiency
SDI 10hp@ 2000rpm with TDI gear ratios-> 320g/kwh -> 26,2% efficiency

You would save about 5,2% by installing taller gear ratios from 1.9 TDI to 1.9 SDI.

[P-hack]

nissan leaf "bsfc" chart:


The right side of the graph is probably ~93 mph. I could use a higher gear ratio.

edit, found another one:

[sword_guy8]

Does anybody know where I can find a chart for a 3.1 GM engine? I've looked all over and can't find anything. Any help would be appreciated, even if you could just point me in the right direction.

Thanks!

[superchow]

Originally Posted by sword_guy8

Does anybody know where I can find a chart for a 3.1 GM engine? I've looked all over and can't find anything. Any help would be appreciated, even if you could just point me in the right direction.

Thanks!

I would search for similar engines from that GM family of engines. We used to have a 3.3 in a 93 Oldsmobile Cutlass Ciera. The low redline and relatively high max torque makes me think the torque graph is quite flat with a local peak.

Hope that helps...

[sword_guy8]

I tried that already. I tried being specific in my searches, and then being broad. I can't find anything. It's such a bummer. Do you know where one would go to get that information normally? Like, before the internet?

[superchow]

I know that European brochures usually showed more technical information, but the 3.1 from GM would have hardly been a European spec engine.

An approximation method may be to look at the V-8 engine with similar bore and stroke from the same vintage and proportionately scale the HP and torque curves. I'm pretty sure that the truck engines have a greater following that the 3.1s.

Maybe looking at the service manual too? There may be a diagram in the back. (Long shot.) Or searching through the road tests of old car magazines?

Good luck!