Yota v K

[bencollins]

Apologies if this thread has been done....but

How come the Toyota engine is so much thirstier (@20%) and heavier than the K?
Shirley the same capacity should be roughly the same results, or?
Is it Euro IV? or over engineering? or the VVT system?

As an engine tech nerd so im curious.

[kambites]

I believe that the K-series VVC has the best power to weight ratio of any 4-pot mass-production engine; the Toyota is fairly average in that respect.

I've never understood why the Toyota Elises are so inefficient either.

[bogie]

one of them is 120bhp and the other 190bhp?

[kambites]

bogie said:

one of them is 120bhp and the other 190bhp?

But the 156bhp K-series returns better economy than the 120bhp one... and better economy than the 134bhp Toyota lump.

Edited by kambites on Friday 20th June 11:49

[Saied]

Interesting question, and its always puzzled me, too.

The 189bhp VVTLi engine, when fitted to the Toyota Corolla T-Sport, returns 34mpg on the official combined cycle.

The Elise R, which is 350 kg lighter and has the same engine, returns less mpg on the same combined cycle (around 32mpg IIRC).

Bizarre. The Lotus should be in the region of 38-39mpg with its significant weight advantage, surely?

[bogie]

kambites said:

bogie said:

one of them is 120bhp and the other 190bhp?

But the 156bhp K-series returns better economy than the 120bhp one... and better economy than the 134bhp Toyota lump.

Edited by kambites on Friday 20th June 11:49

ah yes - the magic of VVC I guess the VVC was/is also the lowest CO2 isnt it?

lets face it, the Rover K was a good engine in its time, the Yota one isnt *that* good...the Honda is far better, but they wouldnt sell it to Lotus, so they had to make do with what they could get their hands on that would fit in the car .......

[Phil-CH]

Saied said:

Interesting question, and its always puzzled me, too.

The 189bhp VVTLi engine, when fitted to the Toyota Corolla T-Sport, returns 34mpg on the official combined cycle.

The Elise R, which is 350 kg lighter and has the same engine, returns less mpg on the same combined cycle (around 32mpg IIRC).

Bizarre. The Lotus should be in the region of 38-39mpg with its significant weight advantage, surely?

Both cars are very differently mapped. I hear from good sources that the ZZ2 engine in the Corola-TS doesn't achieve 189bhp most of the time and is quite a bit lower (average probably around 175-180bhp). Most Elise/Exiges on the other hand, with a more aggressive mapping should hit 189bhp.

[Saied]

Phil-CH said:

Saied said:

Interesting question, and its always puzzled me, too.

The 189bhp VVTLi engine, when fitted to the Toyota Corolla T-Sport, returns 34mpg on the official combined cycle.

The Elise R, which is 350 kg lighter and has the same engine, returns less mpg on the same combined cycle (around 32mpg IIRC).

Bizarre. The Lotus should be in the region of 38-39mpg with its significant weight advantage, surely?

Both cars are very differently mapped. I hear from good sources that the ZZ2 engine in the Corola-TS doesn't achieve 189bhp most of the time and is quite a bit lower (average probably around 175-180bhp). Most Elise/Exiges on the other hand, with a more aggressive mapping should hit 189bhp.

Maybe that explains it.

What about this one: 134bhp Toyota MR2 achieved 38mpg on the combined cycle. The Elise S (weighing at least 100kg less than the MR2) only does 34mpg. Differences in mapping also?


Justin

[Phil-CH]

Saied said:

Phil-CH said:

Both cars are very differently mapped. I hear from good sources that the ZZ2 engine in the Corola-TS doesn't achieve 189bhp most of the time and is quite a bit lower (average probably around 175-180bhp). Most Elise/Exiges on the other hand, with a more aggressive mapping should hit 189bhp.

Maybe that explains it.

What about this one: 134bhp Toyota MR2 achieved 38mpg on the combined cycle. The Elise S (weighing at least 100kg less than the MR2) only does 34mpg. Differences in mapping also?


Justin

Could be. Unfortunately, my knowledge is limited on the ZZ1 engine. It does strike me a bit as a surprise, as from my own experience, I thought the fuel economy was quite good in the Exige and put that down to weight.

How do we know how accurate the numbers are though? I would think reviewers drive a differently with a sportscar such as the Elise/Exige compared to say, a Toyota MR2? I'll see if I can dig up some more data on fuel economy...

[NathanE]

Surely aero drag affects the Elise more than anything?

If you let off the gas slightly in an Elise it slows down pretty quick (drag and lower kinetic energy from the lower mass keeping it rolling).

If you let off the gas in a Celica or whatever it doesn't slow down as quickly (less drag and heavier car so more kinetic energy keeping it going forward).

I can get 35mpg from my 111r quite easily so IMO the figures aren't terribly accurate.

Edited by NathanE on Friday 20th June 13:11

[kambites]

The Elise has a st CD but quite a good CDa because it's so low - it has far lower total drag than something like a Corrola.

[robbieduncan]

You have to take gearing into account. Standard shopping-trolley stuff will have massively long gears for economy. An Elise doesn't. This is also largely the reason the VVC K-Series Elsie S2 gets such good figures: much longer 5th than the standard one.

[kambites]

robbieduncan said:

You have to take gearing into account. Standard shopping-trolley stuff will have massively long gears for economy. An Elise doesn't. This is also largely the reason the VVC K-Series Elsie S2 gets such good figures: much longer 5th than the standard one.

Well I average 37mpg without ever going near a motorway of dual carriageway. I think you'd struggle to do that in a 'yota engined Elise S.

[Scuffers]

kambites said:

I believe that the K-series VVC has the best power to weight ratio of any 4-pot mass-production engine; the Toyota is fairly average in that respect.

I've never understood why the Toyota Elises are so inefficient either.

you are mistaken... just about every bike engine out there does significatly better, then you have stuff like the smart car's engine, closley followed by the B18 Honda etc etc etc...

also, using goverment CO2 or MPG figures are somewhat meaningless in the real world as they are from a very ridgid simulated drive test on rollers, thus if a manufactuer can be arsed, they can map an engine specifically for the test (something they are increasingly doing) rather than for real world economy.

[kambites]

Scuffers said:

kambites said:

I believe that the K-series VVC has the best power to weight ratio of any 4-pot mass-production engine; the Toyota is fairly average in that respect.

I've never understood why the Toyota Elises are so inefficient either.

you are mistaken... just about every bike engine out there does significatly better, then you have stuff like the smart car's engine, closley followed by the B18 Honda etc etc etc...

also, using goverment CO2 or MPG figures are somewhat meaningless in the real world as they are from a very ridgid simulated drive test on rollers, thus if a manufactuer can be arsed, they can map an engine specifically for the test (something they are increasingly doing) rather than for real world economy.

Sorry. I meant car engine, I probably meant normally aspirated car engine to be honest too. Bike engines obviously destroy it quite comprehensively as do some turbo'd engines.

I didn't think the B18 Honda engine was better though? It's a fair bit heavier.


Whatever the the manufacturers figures say, the K-series based Elise annihilates the 'yota engined one in fuel consumption terms.

Edited by kambites on Friday 20th June 17:13

[bencollins]

Phil-CH said:

Saied said:

Phil-CH said:

Both cars are very differently mapped. I hear from good sources that the ZZ2 engine in the Corola-TS doesn't achieve 189bhp most of the time and is quite a bit lower (average probably around 175-180bhp). Most Elise/Exiges on the other hand, with a more aggressive mapping should hit 189bhp.

Maybe that explains it.

What about this one: 134bhp Toyota MR2 achieved 38mpg on the combined cycle. The Elise S (weighing at least 100kg less than the MR2) only does 34mpg. Differences in mapping also?


Justin

Could be. Unfortunately, my knowledge is limited on the ZZ1 engine. It does strike me a bit as a surprise, as from my own experience, I thought the fuel economy was quite good in the Exige and put that down to weight.

How do we know how accurate the numbers are though? I would think reviewers drive a differently with a sportscar such as the Elise/Exige compared to say, a Toyota MR2? I'll see if I can dig up some more data on fuel economy...

Yes the S is a good example cos although it has some kind of VVT it cant be that manic going to only 134bhp.
While, the grippy tyres wont help i agree with the aerodynamic point that even if it is a high coefficient, the frontal area must be significantly lower and at least even that out. Im surprised to learn they mess about with final drive ratios, i thought the Eng+GB unit was fitted as is.
Anyway that doesnt explain the difference between the K & Yota cos the 2003 v 2007 have the same tyres and aero. The issue of the extra weight i can reconcile due to overengineering and beefir GB, but 20% less fuel economy? That's alot. It should have got better not worse. Or?

[Jez O]

[quote=bencollins]


Shirley the same capacity should be roughly the same results, or?
quote]

I don't know. And don't call me Shirley! (in true Airplane style!)

[LivinLaVidaLotus]

Aero, gearing, weight, mapping, as has already been said. Out of interest, what's the official MPG on the VHPD 190?

[Esprit]

LivinLaVidaLotus said:

Aero, gearing, weight, mapping, as has already been said. Out of interest, what's the official MPG on the VHPD 190?

I remember on a 450km journey that my near-standard S1 Elise used to take about 28 litres to do, my 190 VHPD Exige takes about 36 litres, so it's a fair bit thirstier... mind you, the Exige always tempts you to rag it more than the more relaxed Elise used to so it's partially up to driving

[Gooby]

The problems with the K are long and varied.
From Lotus point of view the biggest problem is that they could never get the engine certified for use in the USA and large international markets were off limits while they used the K. This was because in the USof A, any car must be able to go for 100,000 miles with no maintenance. The belt driven cams of the K series would not do this. The engine would also not pass emissions in places such as California.
Lotus needed an international product and thousands of potential customers were crying out for an Elise in various parts of the world

The 'yota with its relatively inefficient chain drive would pass the various regulations to get it into any country in the world, and even better, toyota had got the engine into any country in the world so lotus would not have to worry about certifying the engine at all.

Also don't forget that toyota hold a 25% stake in lotus, lotus and toyota have worked together since the early 1980's (why do you think the first gen MR2 is so good and looks exactly like a Lotus prototype that was going around at the time). Form the Lotus point of view, Toyota are an established business partner with a good relationship, the engine is a reasonable price and capable. It can go into any market in the world and the bottom line is that it is light and powerful AND reliable. (Comparative to its peers)