As you would expect I have been doing some datalogging
Scott (sdminus) eluded to the fact that Tesco99 would have a different stoich value to vpower - he was right i think.
Same map on the ECU.
Same Wideband O2 sensor
Tesco 99 shows 11.16 AFR
Vpower shows 10.8:1 AFR
Quite a difference
Same day, same car, same everything.
I am guessing that depending on map on your car it would have differring impacts. If you car is mapped lean as it was, this could reduce the performance, if mapped rich then maybe tesco99 could improve performance.
Feel free to tell me to get a life but hey someone has to get some facts :lol:
Tesco99 is 5-8% BioEthanol. So would have a similar efect on the AFR/stoichiometric value as running same %Methanol.
You are right in your observation of AFR at current IDC. You can work out the exact stoich by dividing out eg stoich for 10% meth is 13.83
As Gary has explained to me many times, you are better off working in lambda. Because lambda 1 is the same no matter what. Does take a bit of getting used to though :? Personaly I prefer AFR but lambda= AFR/Stoich so a better system really.
Incidently I have also been experimenjting with Meth & Toluene blends. With 10%meth my car is happy running 12.5AFR on normal wideband, providing the EGT's are safe. If the exhaust gas temperature was safe then I would go as lean as 12.5:1 which is about the theoretical point for best power.
Safe EGT is determined by how long you want the engine to last, piston to bore clearance, piston material, exhaust valves, exhaust manifold and turbine wheel/housing capability. 850C is conservative, 950C is considerably braver, 1050C is arguably insane (but can be safe with fancy exhaust valve materials etc).
As usual though you have to find the right trade off that makes power on the setup and fuel you use. On a good race fuel I would expect it might be at about 12.5:1, you can run as much boost as you can without overspeeding the turbo (see compressor map) or overcoming the structural limits of the engine, and then adding timing until it either stops making more power, or knocks, or again you reach the structural limits of the engine (more timing can give higher cyl pressure spikes).
Race fuel will lead to fewer of the usual compromises, and you can get very high outputs without the cylinder pressure spikes you get on 98/99 RON, whilst keeping the EGTs cool, so you can safely run a lot more power even on a stock engine.
Great info there Ross but I wasnt after a discussion on mapping
Just observing that Tesco 99 leans out the engine compared to vPower. Works fine on mine because I map it rich but some people may find it drops performance etc.
[quote="dynamix"]Great info there Ross but I wasnt after a discussion on mapping ]
In theory Tesco99 Or a Methanol blend will lower power output on a car that is mapped on SUL. The calorific value of Meth blends is lower than that of SUL, but it is more det resistant hence *in theory* to raise the power output you would need to either raise the dynamic compression or add more advance.
