Elise SC, CO2 output

[The Pits]

The 111r is quoted at 208 g/km

whereas the SC is 202.

Impressive if true but anyone have any idea how it's possible?

[RobM77]

The Pits said:

The 111r is quoted at 208 g/km

whereas the SC is 202.

Impressive if true but anyone have any idea how it's possible?

As a complete guess, I should imagine that to set the engine up for supercharging they have to change certain characteristics of the engine. I doubt they alter the compression ratio (what normally happens for turbo engines), but certainly something in the ECU would change. I'm not sure what conditions the emissions are tested under, so I can't guess any further than that I'm afraid!

[NathanE]

I reckon its all done with the ecu mapping. Apparently the SC will change onto the 2nd cam at 4000rpm with a wide throttle opening (i.e. you are giving it some).

So I reckon the rest of the time (whilst on the 1st cam) it is on a super duper "Ken Livingstone" mode.

Unfortunately it's the only way a manufacturers can survive... by having quite wild and interesting power curves from the ecu mapping and multiple cams for different types of driving moods.

Edited by NathanE on Thursday 3rd April 18:58

[Blown]

RobM77 said:

The Pits said:

The 111r is quoted at 208 g/km

whereas the SC is 202.

Impressive if true but anyone have any idea how it's possible?

As a complete guess, I should imagine that to set the engine up for supercharging they have to change certain characteristics of the engine. I doubt they alter the compression ratio (what normally happens for turbo engines), but certainly something in the ECU would change. I'm not sure what conditions the emissions are tested under, so I can't guess any further than that I'm afraid!

I have a sneaking suspicion that the emissions are simply calculated using a formula of 2.4KG Co2/ litre of petrol. Thus the g/km thing is just extrapolated from the combined mpg of the vehicle. The SC does slightly more MPG than the N/A car. In much the same way for example that often a 1.4 litre shopping hatch does more mpg than a 1.1 shopping hatch.

[RobM77]

Blown said:

RobM77 said:

The Pits said:

The 111r is quoted at 208 g/km

whereas the SC is 202.

Impressive if true but anyone have any idea how it's possible?

As a complete guess, I should imagine that to set the engine up for supercharging they have to change certain characteristics of the engine. I doubt they alter the compression ratio (what normally happens for turbo engines), but certainly something in the ECU would change. I'm not sure what conditions the emissions are tested under, so I can't guess any further than that I'm afraid!

I have a sneaking suspicion that the emissions are simply calculated using a formula of 2.4KG Co2/ litre of petrol. Thus the g/km thing is just extrapolated from the combined mpg of the vehicle. The SC does slightly more MPG than the N/A car. In much the same way for example that often a 1.4 litre shopping hatch does more mpg than a 1.1 shopping hatch.

I presume that there must be a very close correlation between mpg and CO2, because obviously CO2 comes from burning petrol. I seem to remember that they measure mpg in a rather strange way actually, although I can't quite remember how, I don't think it's the fuel used that they measure!

[The Pits]

I can't see how bolting a supercharger on the same engine can improve fuel economy though?

[kambites]

There are several things it could be. Are the gear ratios the same? Is the compression the same? Are the cams the same?

A forced induction engine can get away with a much less agressive setup when it's running off-boost than a N/A engine. Why is the 111S more efficient than the 120bhp K-series?

[hahithestevieboy]

Maybe its just pumping out carbon monoxide rather than carbon dioxide?

[Blown]

The Pits said:

I can't see how bolting a supercharger on the same engine can improve fuel economy though?

It certainly does in the SC in real world driving. Obviously if it were just full throttle everywhere it would use more juice. I've had several tankfuls in my SC that have got me over 260 miles- I very rarely saw over 220miles in N/A cars.

[Blown]

kambites said:

Are the gear ratios the same?

I was told they were unchanged from the N/A, but I have a feeling they might be a tad longer - Will attach the Snooper this afternoon and go for a thrap.

[RobM77]

The Pits said:

I can't see how bolting a supercharger on the same engine can improve fuel economy though?

They may not have just bolted it on. There may have been some EVU changes.

[polus]

The Pits said:

I can't see how bolting a supercharger on the same engine can improve fuel economy though?

Because its the ECU that controls fueling.

[Scuffers]

Blown said:

RobM77 said:

The Pits said:

The 111r is quoted at 208 g/km

whereas the SC is 202.

Impressive if true but anyone have any idea how it's possible?

As a complete guess, I should imagine that to set the engine up for supercharging they have to change certain characteristics of the engine. I doubt they alter the compression ratio (what normally happens for turbo engines), but certainly something in the ECU would change. I'm not sure what conditions the emissions are tested under, so I can't guess any further than that I'm afraid!

I have a sneaking suspicion that the emissions are simply calculated using a formula of 2.4KG Co2/ litre of petrol. Thus the g/km thing is just extrapolated from the combined mpg of the vehicle. The SC does slightly more MPG than the N/A car. In much the same way for example that often a 1.4 litre shopping hatch does more mpg than a 1.1 shopping hatch.

Nope..

CO figures are calculated from a std drive test on a calibrated set of rollers and a emmisions capturing system.

the total test is ~7Km distance, and is 4 cycles of urban + 1 extra urban, they then take the total CO output and divide by the total distance to get the number.

I believ Lotus certify themselves for this stuff (they have the facilities to do the job).

adding a SC would make sod all odds to this test, it does not demand the sort of throttle usage that will *use* any boost etc, so appart fromt he additional drag of the charger, makes zero odds.

[Blown]

Scuffers said:

Blown said:

RobM77 said:

The Pits said:

The 111r is quoted at 208 g/km

whereas the SC is 202.

Impressive if true but anyone have any idea how it's possible?

As a complete guess, I should imagine that to set the engine up for supercharging they have to change certain characteristics of the engine. I doubt they alter the compression ratio (what normally happens for turbo engines), but certainly something in the ECU would change. I'm not sure what conditions the emissions are tested under, so I can't guess any further than that I'm afraid!

I have a sneaking suspicion that the emissions are simply calculated using a formula of 2.4KG Co2/ litre of petrol. Thus the g/km thing is just extrapolated from the combined mpg of the vehicle. The SC does slightly more MPG than the N/A car. In much the same way for example that often a 1.4 litre shopping hatch does more mpg than a 1.1 shopping hatch.

Nope..

CO figures are calculated from a std drive test on a calibrated set of rollers and a emmisions capturing system.

the total test is ~7Km distance, and is 4 cycles of urban + 1 extra urban, they then take the total CO output and divide by the total distance to get the number.

I believ Lotus certify themselves for this stuff (they have the facilities to do the job).

adding a SC would make sod all odds to this test, it does not demand the sort of throttle usage that will *use* any boost etc, so appart fromt he additional drag of the charger, makes zero odds.

Interesting. Thankyou Simon.

[Blown]

Blown said:

kambites said:

Are the gear ratios the same?

I was told they were unchanged from the N/A, but I have a feeling they might be a tad longer - Will attach the Snooper this afternoon and go for a thrap.

and the result is - SC on newish tyres will do 114 on the limiter in 4th. Anyone got a N/A or an Exige S want to do a similar test ? IIRC my last N/A elise R was circa 110ish at change-up.

[Scuffers]

I should also add that said test is nothing like real world driving as it's performed from stone cold (as in car has to stand for 6+ hours before the start) and the test cycle is way too short for a typical journey...( unless you live in the city or the like).

also, as the test is fixed and known, manufactures will calibrate ECU's to optimise the results from this test - as CO2 figures are now big £££.

Also, then they can charge big money for a 'better' calibration after-market.

Stupid bit is that if they want to charge by CO2 output, it's directly proportional to how much fuel you put in......simple eh?

[Blown]

Scuffers said:

I should also add that said test is nothing like real world driving as it's performed from stone cold (as in car has to stand for 6+ hours before the start) and the test cycle is way too short for a typical journey...( unless you live in the city or the like).

also, as the test is fixed and known, manufactures will calibrate ECU's to optimise the results from this test - as CO2 figures are now big £££.

Also, then they can charge big money for a 'better' calibration after-market.

Stupid bit is that if they want to charge by CO2 output, it's directly proportional to how much fuel you put in......simple eh?

Too simple for the EU obviously... the Australians do it simply by the average MPG - petrol 2.4 KG/litre Diesel (IIRC-) 1.9kg/litre
no tests, no extra civil servants, no license to certify vehicles etc etc etc...