2016 Tacoma Dyno Torque HP Crve

why are the numbers so large at the bottom of the graph? There are 600 and 700s at the bottom of the BSFC graph. Shouldn't those be smaller numbers down there?

 

Not necessarily. The graph is about specific fuel consumption, not absolute consumption. At lower loads the absolute fuel consumption would be lower since it's producing less power, but it uses more fuel on a per horse power (or kWh) produced.

For example. At 2000 RPM and like 30 Nm BSFC is somewhere around 600 g/kwh. You can do the math on converting RPM and Nm to kWh but you can calculate a fuel consumption. If the fuel consumption was linear then doubling your load would double the fuel consumption. But fuel consumption (for this engine and many others) doesn't work that way. You can look at the chart and see that if you double the load, by moving vertically up the 2000 RPM line to 60 Nm, that's right about at the 300 g/kWh BSFC contour (that solid black line is 270 g/kWh). If you do the math again you'd find that the engine is producing twice as much power for the same quantity of fuel as at 30 Nm.

If that doesn't make sense you can call me out on it. I might have made a mistake. This particular BSFC chart is really hard to read because it's two charts in one.

edit: i also just noticed that the vertical axis has 40 unit major tricks with 3 unit subdivisions, so each hash represents 13.3333 units instead of 10 like a normal person would have used. fuckers. Same on the horizontal.

 

I don't know why the upper bounds are where they are; but, I do know they are not max torque. They must map the area of lowest consumption and not bother going much further; but, in the case of the FKS they probably went further to illustrate the improvement over the FE.

There should be only one BSFC map for any engine tune. The "Atkinson" is achieved by variable valve timing. If it cannot produce the necessary torque with the intake valves fully delayed (105° ABDC) then it will delay them less. I don't think it is possible for the FKS to produce that torque with 105° ABDC. At lower rpm the max torque would be cut by ~50%; but, the chart goes to ~78% max torque. The upper bound for the 2GR-FE is further evidence as its' torque curve looks nothing like that and red-lines much higher.

 

Ditto on the axis scaling. WTF?

Maybe this will help you make sense of it. Black dot is best 2GR-FE of 245.5, I think. The rest is FKS: Orange is 240; dark orange is 235; pink dot is 231 (I don't know where they got 224).

 

Good point. I was thinking that the different thermodynamic cycles were much more discrete than they are actually implemented. It switches between cycles on demand but it can all fit on one chart just fine.

The colors are great.

My conjecture for the max line is partly due to equipment limit. The max power they measure is right about a million Nm x RPM. At the high end of the RPMs their machine probably couldn't dissipate any more energy. When they measured the 2GR-FE back in 2006 or whenever they probably had a smaller machine so that one cuts off at an even lower power. I know plenty of dynos can measure much more power than that but their machine may have high precision. Or it could just be old as hell.

I don't know why they stopped at 280 Nm as the maximum tested value for the torque at lower RPMs when it wouldn't exceed max power. It could be a limit of the torque measuring device. I'm not familiar with how that equipment works. But it might just be regular assed laziness. 280 Nm was enough to show that the new engine's island encloses the old one so they called it a day and went to get some sake figuring no one would bother reading this crap anyway.

 

This explains why under light throttle accel, the trans and DBW throttle tries to keep it between 1500 - 2000 rpm all of the time. They are trying to keep in in that efficiency island.

 

I paid too much money for my degree to have to figure this out as it relates to trucks power/torque/output etc...Pretty sure most of you did as well.

 

In order to help myself (and others) better understand the significance of the BSFC map I did some calculations and overlaid some curves to illustrate a couple of practical scenarios. Please correct me if I am going wrong somewhere. Of course, some assumptions are necessarily made; but, I think nearly all of them wash out proportionally.

Say you want to run at min BSFC. Min BSFC occurs at ~1850 rpm and ~210 Nm (which converts to ~54.5 HP, I believe). Say Sweers is genius and this the exact HP required to push a TRDOR 4WD Auto in 6th gear. At 1850 rpm you would be going 71.8 mph. The bottom curve represents 54.5 HP. The next green dot down the line is 5th@2191rpm. You can see if you increase rpm but keep the power (speed) the same by downshifting you are burning more fuel per HP. 4th@3190. All very intuitive, so far.

Lets say Sweers isn't concerned with going 71.8mph most efficiently and it takes 66hp, or you're going uphill, or into the wind, or loaded, or towing. This is the upper curve. In 6th, you are at 240g/kWh. So, you are better off in 5th burning ~235g/kWh. That's only ~2% different; but, at higher output it will be more significant.

I'll try to guess at some numbers. Let's say you can get 22mpg at 54.5HP at 71.8mph.
6th = 22.0 mpg
5th = 20.5 mpg
4th = 19.2 mpg

At 66HP it may be:
6th = 17.5 mpg (22/66*54.5/240*231)
5th = 17.9 mpg (better!)
4th = 16.7 mpg

 

One more...

The curves below represent constant HP. The lower is 10; 20; etc.; the upper is 140 HP. Yeah, this map only appears to go to ~148 HP. The line crossing all the HP lines shows the most efficient rpm for each HP. This is the rpm you want be at for a given power demand.

At first I thought it was weird how the orange area was stretched from lower left to upper right; but, with these HP curves overlaid you can see that this is exactly how you would want it to be stretched.

 

Check out the big ol' brain on Brad!!

Jk, great work THarris242!

 

LOL. Best movie ever?

 

it's too late for all this PEMDAS

 

"Some people don't want a full size truck."
BINGO.
Thanks AGAIN for stating the obvious.

 

I don't want a full size truck

 

Now THIS is the kind of stuff I come to forums for.

Is there any way to translate your single most efficient line across the HP lines into % throttle at certain gears or something? Meaning, how do I know I am close to that most efficient zone while under load, since this implies I can be using extra gas by being too gentle...

 

So is this still the same dyno-torque thread with no actual dyno-torque chart? How are we on page 8 already?

 

You must have missed the Dino Graph

 

Officer, I know the max speed limit is 55 mph; however, I'm doing 71.8 mph to maximize fuel efficiency - I'm doing it to conserve fuel, reduce my carbon footprint, and save the planet... it's all for the children!

 

THINK OF THE CHILDREN!!

 

Gas engines aren't very efficient (talking thermodynamic efficiency) at part-load, because nearly-closed throttle=high throttle losses.

Diesels don't have a throttle, which is why they are so efficient when cruising on the highway (way moreso than just due to the higher energy content of diesel fuel). Low-displacement turbocharged gas engines cruise with a much more open throttle at zero boost compared to a larger-displacement naturally-aspirated engine.

The best truck engine configurations (where you care about efficiency and low end) are: turbodiesel>turbo gas>n/a gas. Toyota's 2L gas turbo (sold in a bunch of Lexi now) would actually have been a much better engine for the Taco than this 3.5L, not to mention their diesel. But Toyota is hamstrung by their customers' expectations, so they never innovate on the powertrain front until they absolutely have to. That probably won't happen until the Ranger shows up with a 2.3L turbo that gets 30 MPG.