You could ask a Lotus dealer if they could re-program your ECU with a late 2005 240 Cup calibration but you would need to fit the 240 Cup injectors as they are special parts (larger).
I’m wondering if the std Exige S injectors are big enough. If you look here you’ll see the AFR run a bit lean at the top end…
“Ideal” is a strong word but I would say that 12:1 is a good general guideline. Obviously 13.5:1 isn’t lean in outright terms buts it leaner than I’d like to see.
“Ideal” is a strong word but I would say that 12:1 is a good general guideline. Obviously 13.5:1 isn’t lean in outright terms buts it leaner than I’d like to see.
I think i understand the graph now, So it shows the engine is at its leanest at 4500 rpm?
The blue line is with the other induction kit and it is a little leaner at the top end?
Would the ecu be able to learn that the engine is a little leaner with the itg and over time compensate?
Some engines can compensate if they are fitted with wide band lambda sensors i.e. it can output a signal which is proportional to the AFR but I would imagine that the Lotus one simply says rich or lean so it doesn’t know if its running 10:1 or 14:1, its just “rich”.
If you do something to improve the performance to a car like the Exige which is fitted with a Mass Air Flow (MAF) meter it will recognise that the airflow has gone up and will injector the appropriate amount of fuel to give the ideal AFR. The fact that above 7200rpm it starts to lean off in a very uniform manner suggests that the injectors are pegged wide open (or at least getting into the range where they stop giving significant increases in fuel flow with longer pulse width, which at ~80%).
The fuel pressure regulator is in the fuel tank on the Exige so its not easy to get to it to modify. To get more flow you’d need to fit larger injectors.
Runing an AFR of 13.5:1 is generally okay upto about 6000rpm but its generally about this point that the exhaust temperature limit is reached (~900�C is the limit for the head). Above this speed you need to squirt in lots of extra fuel which simply quenches the heat (p1ssing on a bomfire springs to mind) so leaning out at peak power might not drop power (although on the graph shown above it did!) but it will lead to a significicant reduction in engine durability…
Some engines can compensate if they are fitted with wide band lambda sensors i.e. it can output a signal which is proportional to the AFR but I would imagine that the Lotus one simply says rich or lean so it doesn’t know if its running 10:1 or 14:1, its just “rich”.
If you do something to improve the performance to a car like the Exige which is fitted with a Mass Air Flow (MAF) meter it will recognise that the airflow has gone up and will injector the appropriate amount of fuel to give the ideal AFR. The fact that above 7200rpm it starts to lean off in a very uniform manner suggests that the injectors are pegged wide open (or at least getting into the range where they stop giving significant increases in fuel flow with longer pulse width, which at ~80%).
The fuel pressure regulator is in the fuel tank on the Exige so its not easy to get to it to modify. To get more flow you’d need to fit larger injectors.
Runing an AFR of 13.5:1 is generally okay upto about 6000rpm but its generally about this point that the exhaust temperature limit is reached (~900�C is the limit for the head). Above this speed you need to squirt in lots of extra fuel which simply quenches the heat (p1ssing on a bomfire springs to mind) so leaning out at peak power might not drop power (although on the graph shown above it did!) but it will lead to a significicant reduction in engine durability…
Why would Lotus do this, i mean if anybody should get the map right it should be the oem?
Maybe they did not want to have different injectors to the standard car, for cost reasons, and decided it would be ok?
So to recap, the brakes are made of cheese, the intercooler works more like a heater…and now the engine runs lean at high revs!
I must admit, i often find myself mildly dissapointed by Lotus. The car is great and i love it, but it does not seem to have the engineering depth and integrity of a Porsche (wash my mouth out… )
Could it be that the blip at 4500 is the cam change, and thats why its difficult to get the mixture exactly right?
I would be interested to know if the S injectors are the same as in the 2006 Cup, which i understand also has four injectors. If they are, then they are not the limiting factor…unless the Cup runs even leaner
I wish someone would come up with some simple tuning options for the Exige S. So far I have a pipercross filter and 2bular exhaust but thats probably just helped sound and made it lighter. I know its a new car etc but its frustrating, I have cash waiting to get the car to 265bhp but nobody sells anything yet. I will bide my time…
The Exige S i think is selling very well and so this will become the case more and more. Tuners will have to experiment sooner or later. Potential to make a lot of money here.
Hey any luck with the blower manifolds? I’m running 440cc injectors with no lean issues…I’m using an Xede piggyback and a non learning stock ECU so that any tune I make is not erased by the stock setup…So far this is giving me 225rwh…but would still like to add a charge cooler without having to do too much custom work…so if someone can tell me if the Lotus manifolds can be bought over the counter I’d be greatfull…thanks
According to my workship manual-s/c supplement the later cup cars have 4 “larger” injectors whereas the S has 4 “standard” injectors. I’ll quote the text verbatum when I get chance later on.
Both the 240R and early 240 Cup cars use an additional injector.
Regarding the manifold I’ll try an ask. I copied the VIN off an S in the showroom the other day so I should be able to get that…
The Exige S i think is selling very well and so this will become the case more and more. Tuners will have to experiment sooner or later. Potential to make a lot of money here.
We need a cup dealer, who can change the injectors (if neccessary) put on the 240 cup pulleys, re flash the ecu with the 2006 map and we’re done.
As i have said on a few occasions, 265 is what the lotus cup guys in europe are getting with a manifold, de cat and stage 2. They are however having leaning issues and the same loss of performance we suffer when the intercooler gets hot.
I think the first stage is to get the S consistantly producing its claimed power. This can be done without warranty problems etc, coz we would just improve the airflow for the cooling of the intercooler.
The second stage would be 240 maps pulleys etc we do not need to re invent the wheel. The 240 cars are out there, tried and tested and all the parts are readily available (i would assume) from the cup dealers.
Then a complete exhaust system and a consistent 265 would be rather nice.
…and keeping our improvements in the family so to speak…The Circuit car is said to be 272 and the map etc for that should becomne available when that car is launched. Its presumably more than a cup car coz it will not have to meet emissions etc…which to be honest is not my top priority either
Which means they need to bring in air from the side intakes. I hope they are bigger than on the exige…coz the cup cars engine bays overheat when they steal air from the sides.
…just checked, they are very small. I hope they get some cooling air from somewhere…
The injector for exiges S part #A120E6360S.
I am lucky enough to have ONE Lotus dealer down here in third world…Mexico, maybe in few hundred years I will have CUP dealer.
Tomorrow I will meet with Stefano D’Este, he runs in the WTCC, and they have a race in Mexico. He is also a tuner specialized only for Lotus in Italy http://www.pbracing.it/.
He his preparing a kit for the exige S I will keep you updated.
We need a cup dealer, who can change the injectors (if neccessary) put on the 240 cup pulleys, re flash the ecu with the 2006 map and we’re done.
Expect that in the States by the end of the year. I’m told to expect it as a buying parts over the counter as opposed to an official retrofit in “kit” form.
