Technical Why Twinair never really worked

[AGH1965]

Are you hard of understanding? The NEDC IS the “promise” and the twinair seems farther from the “promise” than the vast majority of cars out there.

Hard of understanding? No, I'm not. In every brochure of every car manufacturer were disclaimers telling you that NEDC results do not resemble reality. Why is it so difficult for you to understand what that means? Well, let met try to explain it one more time. It means that you shall not compare these figures with real-world fuel economy! So stop doing that, since it doesn't make sense!

 

[306maxi]

Hard of understanding? No, I'm not. In every brochure of every car manufacturer were disclaimers telling you that NEDC results do not resemble reality. Why is it so difficult for you to understand what that means? Well, let met try to explain it one more time. It means that you shall not compare these figures with real-world fuel economy! So stop doing that, since it doesn't make sense!

No brochure says that.

Here’s an example...

“These figures facilitate direct comparison between different models from different manufacturers, but MAY not represent the actual fuel consumption achieved in ‘real world’ driving conditions”

The point is that having a bigger delta to “real world” figures means that Fiat have designed an engine to be driven in NEDC tests and not in the real world, pity we all live in the real world and don’t all do NEDC every day.

Which is a world away from “does not resemble reality”. You have an atypical and selfish view of fuel economy figures. Simple as that.

 

[UFI]

Have I?

Don't be another Andy, please. Are you really suggesting that my Fiat burning 10% over is going to kill the planet in a world where the 2+ tons of SUV is fast becoming the minimum? The top 2 best sellers in Oz are now 2+ ton trucks. They put out double the CO2 I do (assuming they match official) and the industry average is actually 40% over claimed...

So while Andy got his calorific values wrong, what’s the average thermal efficiency of a diesel vs a petrol engine car?

I think people have taken this very personal against their chosen engine, it’s not like that at all.

Everyone always goes on about the 1.2 being slow, I don’t take offence at that :laugh:

No numbers exist for the average thermal efficiency of a diesel - no OEM that I've ever seen has put out those numbers - seriously, try to find something concrete. We do know from a few sources (notably Toyota) that 40% (yes that is 'peak') is possible from current tech petrol. We know that from simple calorific calculation that a 60mpg petrol is theoretically equivalent the same car getting 69mpg on diesel - which is about what 500 MJ's get. So the real world difference is pretty tiny- which would tend to agree with my own petrols vs diesels being hardly any different.

I think FIAT's error was loaning out press cars that weren't run in. ~38MPG they all cried - that was all the ammo the experts needed - any claims of good mpg are now simply ignored. I got ~38MPG driving (new car/ new engine) gently on my first tank too.

I own 2, 4, 6, and 8 cylinder engines, petrol, diesel and hybrid. So I don't think I have a 'chosen' engine, frankly they all have their charms

UFI's even going up for sale soon (I no longer need a small car), I want an Exige, which will be my first V6 (I hate V6's).

 

[306maxi]

Don't be another Andy, please. Are you really suggesting that my Fiat burning 10% over is going to kill the planet in a world where the 2+ tons of SUV is fast becoming the minimum? The top 2 best sellers in Oz are now 2+ ton trucks. They put out double the CO2 I do (assuming they match official) and the industry average is actually 40% over claimed...



No numbers exist for the average thermal efficiency of a diesel - no OEM that I've ever seen has put out those numbers - seriously, try to find something concrete. We do know from a few sources (notably Toyota) that 40% (yes that is 'peak') is possible from current tech petrol. We know that from simple calorific calculation that a 60mpg petrol is theoretically equivalent the same car getting 69mpg on diesel - which is about what 500 MJ's get. So the real world difference is pretty tiny- which would tend to agree with my own petrols vs diesels being hardly any different.

I think FIAT's error was loaning out press cars that weren't run in. ~38MPG they all cried - that was all the ammo the experts needed - any claims of good mpg are now simply ignored. I got ~38MPG driving (new car/ new engine) gently on my first tank too.

I own 2, 4, 6, and 8 cylinder engines, petrol, diesel and hybrid. So I don't think I have a 'chosen' engine, frankly they all have their charms

UFI's even going up for sale soon (I no longer need a small car), I want an Exige, which will be my first V6 (I hate V6's).

Don’t be an Andy? Huh?

I think even you’ll agree that you’re not a typical example. You run or at least ran lithium batteries as a 12v power source in your 500 right?

I can get the NEDC figures out of my completely standard car, the fact that Fiat have a bigger delta to the NEDC figures than most manufacturers says that customers are getting a bum deal.

This was never even a diesel vs petrol thing anyway. It was just a well reasoned (find the fault in what he’s saying) video which explained why small turbo engines like the twinair never really delivered the fuel economy that they promised. The fact that you posted the hilarious example of Bentley getting better fuel economy than NEDC in real life says that bigger and less stressed engines are more likely to do better than small stresses turbo engines like the twinair.

Of course twinair 500s are not going to be the death of the planet, but you don’t seriously think that a 10% reduction in CO2 isn’t a big thing? In the words of Tesco, “evry little elps”. 10% across the board would be a massive decrease.

I’ve liked the twinairs that I’ve driven, but they didn’t really meet my expectations in terms of fuel economy and even though they have their charm, it’s not charming enough to make up for the disappointing fuel economy.

 

[306maxi]

https://www.theicct.org/blogs/staff/ever-improving-efficiency-diesel-engine

There are figures for diesel efficiency, the fuel consumption figures bear these figures out.

I don’t like diesel myself, but for fuel efficiency and power they are good. If I’d been doing mike munching in my 500 I might have gone for one.

 

[AGH1965]

Here’s an example...

“These figures facilitate direct comparison between different models from different manufacturers, but MAY not represent the actual fuel consumption achieved in ‘real world’ driving conditions”

Which is a world away from “does not resemble reality”.

So now a foreigner has to teach you English? Well, I will give it a try.

The use of "may" in disclaimers only expresses that there is a chance, but not how much. A chance close to 100 % is still a chance. So even in that case it is perfectly legal to use "may".

Now you will say: "The chance isn't close to 100 %; it is 100 %!" But that is not true. Everyone who drives NEDC style under optimal conditions will likely reach the official figures. Don't you drive NEDC style yet? Ah, that's a pity...

Conclusion: Everybody should know that when a disclaimer says "may not" it likely means "does not".

 

[306maxi]

So now a foreigner has to teach you English? Well, I will give it a try.

The use of "may" in disclaimers only expresses that there is a chance, but not how much. A chance close to 100 % is still a chance. So even in that case it is perfectly legal to use "may".

Now you will say: "The chance isn't close to 100 %; it is 100 %!" But that is not true. Everyone who drives NEDC style under optimal conditions will likely reach the official figures. Don't you drive NEDC style yet? Ah, that's a pity...

Conclusion: Everybody should know that when a disclaimer says "may not" it likely means "does not".

This is getting silly. Does not is not the same may not.

Yet you still think that it’s good that the twinair does worse than other manufacturers who sell cars in the class. Lol

 

[AGH1965]

Is that if you put your foot down in either car, despite the increase in speed, neither seem to see any increase in the amount of fuel consumed.... actually it looks like the fuel use goes down despite burying the throttle

Apparently you think that it is impossible that the fuel consumption in l/100km decreases when the car's speed increases while accelerating with full throttle in highest gear. Since Maxi liked your post, he seems to think the same. Therefore I will try to explain how that this is possible.

Modern engines often have a wide, flat maximum torque section in their torque curve. When accelerating with full throttle in highest gear through this section of the torque curve, the engine's power increases proportionally with its revs. If the engine's efficiency is constant in this section, then the fuel flow increases proportionally with the power and therefore also proportionally with the revs. Since the car's speed also increases proportionally with the revs, this results in a fuel economy (either in l/100km or mpg) that stays constant when accelerating with full throttle in highest gear through this section of the torque curve.

However, what happens if the engine's efficiency improves when the revs increase in this section of the torque curve? In that case the fuel flow will increase less than proportionally with the power and therefore less than proportionally with the revs. Since the car's speed still increases proportionally with the revs, this means that the fuel economy improves (l/100km down, mpg up) when the speed increases while accelerating with full throttle in highest gear through this section of the torque curve.

With turbocharged engines this might not work in lower gears, since the turbo must deliver boost quickly enough to reach the maximum torque.

 

[AndyRKett]

You can bicker and bitch back and forth as much as you like, In the grand scheme of things this is all irrelevant anyway because it bares no influence on the discussion at hand.
The whole point of the thread.

Small engine petrol turbos don’t meet anywhere near their claimed economy figures, it’s its not meeting the economy figures then it’s definately not hitting the claimed CO2 figures either. This is not exclusive to the twinair but the twinair definately is one of the worst offenders.

It would be pointless of Maxi to post the video and draw a comparison to a VW or ford engine, it’s not a VW or ford forum.

If you bought a bag of oranges that were claimed to be 6.7cm in diameter and you got a bag of 4.4cm oranges you and anyone else would be pretty annoyed. This is exactly what fiat did.
They may put disclaimers saying that the oranges in the picture “may” not be exactly representative of the oranges you get, but you still expect a reasonably fair deal.

If want a car that has a much lower disparity between the claimed figures and actual figures, buy a diesel, buy a fiat diesel, buy an NA petrol or buy a Bentley, I don’t really care, but don’t get on your high horse trying to prove something to be wrong when there is plenty of evidence, articles, threads, published data all over the internet and in the press, which shows the opposite of the argument you’re trying to make.

 

[AndyRKett]

Apparently you think that it is impossible that the fuel consumption in l/100km decreases when the car's speed increases while accelerating with full throttle in highest gear. Since Maxi liked your post, he seems to think the same. Therefore I will try to explain how that this is possible.

Snip

However, what happens if the engine's efficiency improves when the revs increase in this section of the torque curve?

Indeed, what happens, what happens if you post your theories on the internet without any evidence base or knowledge and expect people to buy it?

I honestly can’t be bothered to argue with someone unwilling to accept reality, if I was there is a whole subsection of the internet dedicated to flat earth and religion.

 

[lsgraham_uk]

Indeed, what happens, what happens if you post your theories on the internet without any evidence base or knowledge and expect people to buy it?

I honestly can’t be bothered to argue with someone unwilling to accept reality, if I was there is a whole subsection of the internet dedicated to flat earth and religion.

Let's face it this whole thread should read, don't buy a twin air - get an abarth

 

[UFI]

https://www.theicct.org/blogs/staff/ever-improving-efficiency-diesel-engine

There are figures for diesel efficiency, the fuel consumption figures bear these figures out.

So yeah, a 4% advantage which you add to the 15% calorific advantage, to get around 20% - thats seems to agree with what I've seen and what we see reported. The TE of the diesel is greatly exaggerated.

Indeed, what happens, what happens if you post your theories on the internet without any evidence base or knowledge and expect people to buy it?

I honestly can’t be bothered to argue with someone unwilling to accept reality, if I was there is a whole subsection of the internet dedicated to flat earth and religion.

The most basic of concepts seem to allude you. An engine at full throttle cannot burn any more fuel. Just because the speed increases, the throttle body and injectors don't allow more fuel to pump into your engine, they're already maxxed out the moment you go WOT. Energy stops being converted into acceleration and is required to overcome drag -the overall energy being produced/ consumed remains the same.

An engine doesn't burn fuel in MPG, it burns fuel in litres/hour. At full throttle, a Twinair uses around 30l/hr. If you nail the throttle in 1st a 5km/h or 160 in 5th, your engine still only uses 30l/hr. So 30l/hr at 90km/h is 33l/100km and 30l/hr at 160 is only 18l/100km. WOT fuel consumption falls with speed.

Gradients, headwinds, tail winds, or if you've paid this week's ritual goat sacrifice, none of that matters because at full throttle the engine will ALWAYS consume 30l/hr. You can take ten seconds of data, you can take ten million years of data, it will always use 30l/hr. The engines are rated only 5hp apart so the conditions look the same - we can definitely conclude that for the same rate of acceleration, the fuel economy is much improved.

It doesn't magically grow a bigger throttle body, injectors and fuel pump as your flat earth theory would require, despite your argumentative tone.

AGH's graphs and EE video are important and relevant because they show without question that the issues outlined in Maxi's EE video have indeed been fixed for Euro 6. The video would have been relevant 5 years ago, it's really not any more. If you don't like it, post DATA, not waffle on making wild claims about people who take the time to run experiments and post data.

 

[jrkitching]

@jrkitching can you just lock this damn thread?

Not a chance - this way I've got all the trolls in one place where I can see them, and it's keeping the rest of the section delightfully free of such controversy .

 

[306maxi]

Not a chance - this way I've got all the trolls in one place where I can see them, and it's keeping the rest of the section delightfully free of such controversy .

Fair point.

Do you have any opinion on the matter?

 

[AndyRKett]

The most basic of concepts seem to allude you. An engine at full throttle cannot burn any more fuel. Just because the speed increases, the throttle body and injectors don't allow more fuel to pump into your engine, they're already maxxed out the moment you go WOT.

An engine doesn't burn fuel in MPG, it burns fuel in litres/hour. At full throttle, a Twinair uses around 30l/hr. If you nail the throttle in 1st a 5km/h or 160 in 5th, your engine still only uses 30l/hr. So 30l/hr at 90km/h is 33l/100km and 30l/hr at 160 is only 18l/100km. WOT fuel consumption falls with speed.


It doesn't magically grow a bigger throttle body, injectors and fuel pump as your flat earth theory would require, despite your argumentative tone.

AGH's graphs and EE video are important and relevant because they show without question that the issues outlined in Maxi's EE video have indeed been fixed for Euro 6.

Two graphs side by side, one shows the amount of fuel measured in L/h increasing as the car gathers speed as you would expect, to maintain the correct stoumetric ratio needed to maintain efficient running conditions.

The other graph measured in litres per 100km shows no significant change up or down in the fuel consumed over 100km.

The car is able to and is adding more fuel. You can’t go faster over the same distance and not use more fuel.

Assuming the first graph is correct that’s what it is showing, acceleration without any increase in fuel use despite and increase in energy needed to accelerate.

Even comparing a car traveling at 110km and one traveling a 130km with everything else being equal (same gearing and conditions) you would expect the faster car to use more fuel, so this would clearly visible on the graphs.... if the graphs were accurate.


This website which Agh1965 used to prove fuel economy figures for the twinair shows no increase in fuel efficiency if you expand the search to include all cars up to 2018..
https://www.spritmonitor.de/en/over...18&power_s=62&power_e=64&minkm=2000&gearing=1

So no these graphs are BS

 

[AGH1965]

Even comparing a car traveling at 110km and one traveling a 130km with everything else being equal (same gearing and conditions) you would expect the faster car to use more fuel

YOU would expect that, but you forget that these cars aren't driving at a constant speed, but they are accelerating. Also power and therefore fuel is needed for the acceleration. However, when the speed increases, the acceleration gets less. So more power is needed for the speed and less for the acceleration. This combination is what matters. if such elementary knowledge is lacking, then any discussion is pointless.

This website which Agh1965 used to prove fuel economy figures for the twinair shows no increase in fuel efficiency if you expand the search to include all cars up to 2018..
https://www.spritmonitor.de/en/over...18&power_s=62&power_e=64&minkm=2000&gearing=1

Well, I'm impressed. You repeated what I already wrote:

Compared to the Euro 5 TA, the Euro 6 TA has a fuel economy improvement at full throttle of about 30 percent, but real-world fuel economy isn't improved much at all. In other words, the cause of the "disappointing" real-world fuel economy of the TA is differs from what you suggested.

The last part - sorry for the typo - is a response on Maxi's suggestion that the extremely low air/fuel ratios at high engine loads are the reason for the "disappointing" fuel economy of the TA. But the Euro 6 TA doesn't have these, and still real-world fuel economy isn't much better. Apparently the fuel economy at high engine loads and full throttle isn't that important for normal use, unless you think you need to be faster than Lewis Hamilton... So if the fuel economy of the TA is really "disappointing", then there must be another reason. That is the point I wanted to make.

So no these graphs are BS

Apparently you didn't pay much attention to the teacher during math lessons. The explanation is very easy to understand for anyone who can multiply and divide, and who knows what proportionally means. So here it is again:

Modern engines often have a wide, flat maximum torque section in their torque curve. When accelerating with full throttle in highest gear through this section of the torque curve, the engine's power increases proportionally with its revs. If the engine's efficiency is constant in this section, then the fuel flow increases proportionally with the power and therefore also proportionally with the revs. Since the car's speed also increases proportionally with the revs, this results in a fuel economy (either in l/100km or mpg) that stays constant when accelerating with full throttle in highest gear through this section of the torque curve.

However, what happens if the engine's efficiency improves when the revs increase in this section of the torque curve? In that case the fuel flow will increase less than proportionally with the power and therefore less than proportionally with the revs. Since the car's speed still increases proportionally with the revs, this means that the fuel economy improves (l/100km down, mpg up) when the speed increases while accelerating with full throttle in highest gear through this section of the torque curve.

 

[AndyRKett]

YOU would expect that, but you forget that these cars aren't driving at a constant speed, but they are accelerating. Also power and therefore fuel is needed for the acceleration. However, when the speed increases, the acceleration gets less. So more power is needed for the speed and less for the acceleration. This combination is what matters. if such elementary knowledge is lacking, then any discussion is pointless.

What are you even talking about

If you accelerate any object you need to put energy into that acceleration, in a car that energy comes from fuel

You posted two graphs

The one of the left shows an obvious increase in fuel consumption with acceleration as you would expect to see.

The graph on the right shows no increase in fuel consumption despite and obvious and marked change in speed.

This is not an averaged calculation of fuel used over 100km it is an instantaneous value of L/KM based on the fuel being used and the road speed

It is also one snapshot of a single 15 second period which just shows exactly what you want it to show.
You could be on a hill in one car and not the other. Have a head wind or there be a significant difference in air temperature, without any other information you expect this one tiny instance that you managed to find and overlap, to prove that the euro 6 car has solved all the problems of a euro 5 car.

If this was a research project you’d literally have nothing to write about you can keep banging on about these graphs all you want they prove nothing at other than once you managed to get the acceleration curves of two cars to match roughly.

I don’t care how you spin it, your data shows nothing, I could make a graph just like that in about 5 minutes in excel.

 

[StevenRB45]

I think the point here is...one side is stating maximum fuel use is a constant. So flat out at 5000 rpm in 3rd uses the same amount of fuel as flat out at 5000 rpm in 5th. The engine is seen to be in the same state regardless, but the action of the gearing effective gives more distance per "bang" so a better MPG figure despite a similar fuel flow?

Yes?

If that's not it F**k knows.

 

[AGH1965]

This is not an averaged calculation of fuel used over 100km

Indeed. Like mpg is the standard unit in the UK, most of the world uses l/100km, but that doesn't mean you have to drive 100 km. Just like mpg doesn't mean you have to burn 1 gallon.

You could be on a hill in one car and not the other. Have a head wind

Like UFI already explained, hills or wind do not influence the fuel flow when accelerating full throttle. They do influence the acceleration, but you see these are close to identical. That's not strange, since both the TA85 Euro 5 and the TA80 Euro 6 have 145 Nm over a wide rev range. So if the conditions are comparable, both cars accelerate equally fast.

If this was a research project you’d literally have nothing to write about

I would have a lot to write about, but you wouldn't understand. Therefore I keep it simple.

 

[AndyRKett]

Indeed. Like mpg is the standard unit in the UK, most of the world uses l/100km, but that doesn't mean you have to drive 100 km. Just like mpg doesn't mean you have to burn 1 gallon.


I would have a lot to write about, but you wouldn't understand. Therefore I keep it simple.

You explain back to me what I have literally just said we’ll done have a sticky star.

Then you try to be condersending by saying something that you don’t seem to get and have failed to explain your way around is beyond me....

One graph from one 10 second time period that I can make in 5 minutes on excel doesn’t prove anything and certainly doesn’t have to have come from any real world data, we only have your word on that, and guess what you have a vested interest in proving yourself right.

The website you relied so heavily on further back in this thread however shows no improvement in fuel economy factoring in all twinair models of the same type from 2011-2018

So do we believe the graphs you made up on your computer or do we believe the website with lots of people’s real world data?

I didn’t buy your graphs when you first posted, and I’m not going to no matter how much you keep trying to justify their importance.
There is literally nothing left to discuss.

Twinair, doesn’t get its claimed figures by a country mile and that’s pretty much the end to it.