MoTeC Global Forum

I have attempted to rewrite my post from earlier today hopefully this is more clear and less offensive to those reading it as this is just the facts regarding Map only and Map/Baro or Emap or Aux V and to correct my earlier statement this is the only proper way to calculate efficiency using a pressure sensor as everyone knows the only proper way to calculate efficiency is to not calculate it at all and use a Mass meter.

Sea level - WOT 101.32 Kpa MAP and 101.32 Kpa BAP = 100% efficiency - deliver pulsewidth based on main table value (lets assume 100) and IJPU assume 10. So deliver 10mS to Injector

Now go to denver at WOT - 80 Kpa MAP and 80 Kpa BAP = 100% efficiency - deliver pulsewidth based on main table value (100) and IJPU (10) but reduce to 80% (roughly) because of MAP comp since the air density is now 80% of what we had at sea level (8mS)

Now the next one - this is harder to get.

Sea level cruise - 50 Kpa MAP and 101.32 Kpa BAP = 50% (about) efficiency - deliver pw based on 50% efficiency site (assume 38) and IJPU (10) so 3.8mS but then reduce that to 50% because of MAP Comp so deliver 1.9mS.

Denver cruise - 40 Kpa MAP and 80 Kpa BAP = 50% efficiency - deliver pw based on 50% efficiency site (assume 38 again)and IJPU (10) or 3.8mS but then reduce to 40% because of MAP comp so deliver 1.52mS.

We are saying essentially that the Efficiency of the engine (Intake Pressure versus Exhaust Pressure) is the same in Denver as sea level (50% in this case) and that because this is so - we need only take into account the density change to fuel the engine properly.

Now here is the problem with the MAP only as the efficiency.

Sea level - WOT 101.32 Kpa MAP and 101.32 Kpa BAP (but not used in calculation)= 100 efficiency - deliver pulsewidth based on main table value (lets assume 100) and IJPU assume 10. So deliver 10mS to Injector

Now go to denver at WOT - 80 Kpa MAP and 80 Kpa BAP (but not used in calculation) = 80 efficiency - deliver pulsewidth based on main table value (assume 75) and IJPU (10) but reduce to 80% (roughly) because of MAP comp since the air density is now 80% of what we had at sea level (6 mS) Compare to correct Efficiency value from other calculation - Engine Runs Lean because with equal pressure on both sides of the cylinder the cylinder is actually operating at 100% efficiency not 80, but that is not indicated by MAP only.

Now the next one - this is harder to get just like the other one.

Sea level cruise - 50 Kpa MAP and 101.32 Kpa BAP (but not used for calculation) = 50 (about) efficiency - deliver pw based on 50 efficiency site (assume 38) and IJPU (10) so 3.8mS but then reduce that to 50% because of MAP Comp so deliver 1.9mS.

Denver cruise - 40 Kpa MAP and 80 Kpa BAP = 40 efficiency - deliver pw based on 40 efficiency site (assume 32) and IJPU (10) or 3.2mS but then reduce to 40% because of MAP comp so deliver 1.28mS - Compare to correct Efficiency value from other calculation - Engine Runs Lean!

So in this case what we are saying is that 40Kpa intake with 100 Kpa exhaust (which is how it will be tuned on a sea level dyno) will not fuel the engine properly when in Denver at 40Kpa intake with 80 Kpa exhaust because with the reduced exhaust pressure compared to intake pressure the efficiency is greater than what is reflected in just the manifold pressure sensor. But since you have no way to reference what the local pressure is using MAP only, you will underfuel the engine because it's true efficiency at this altitude in these conditions is 50% not 40.

Perhaps I am all wet on this - but "God" taught me this so if I am wrong, then so is he.

By "God" you mean Allan Hines?

Hi Shane,
The MAP/User1 efficiency calculation method has not been included in the initial release of M84. This has something to do with the way the software was put together and was not intentional but including it would have caused a delay in making the M84 available. We are planning a software update in the very near future to include a nitrous function and some other changes and we will include appropriate alternative efficiency calculations at the same time.

Now em - how soon can we expect that release??

Thanks for the attention in this matter.

I expect to have something out fairly soon. We will finalise details in about 2 weeks, I am hoping to have something available next month.

Hi Ross,

we have a project regarding M84 which include the nitrous function,the engine will be ready for the dyno in mid-January,coud we expect a release for that time?
Best regards

So when is this new software going to be out?

Hi All,
I have been testing the M84 Nitrous function today and all seems to be going well. We will hopefully be able to release this soon. I can't really give an exact date becasue our workload is a little dynamic here.

Just so you know, the Nitrous function is the same as the M800 but with only one stage not 3.

thanks

HI Mark,

good news!!! waiting for a release to test!!