According to a race car tuning expert (engineer I spoke to), the best fuel ratio for a cars best performance is 12.7:1 - to meet EPA and other fuel regulations (gas milage requirements etc.) the car companies do what HD does and through the ECU forces the fuel ratio to in some cases like Honda to 15.0:1. By remapping or changing the fuel ratio back to or at least below the 15.0:1 will give more performance and a cooler engine but at a gas milage expense.

He does`nt know the HD bikes but assumes it would be a similar situation. By remapping to 14.1:1 or even less as some of the XiED`s do we would get similar results - cooler/more power/ less milage. He does`nt believe the XiED would harm the engine in any way and it is just another way to remap.

Granted the SERT has many maps for different loads and throttle positions but he does`nt believe that having one setting that is below the 14.7:1 will harm it in any way - we may get better / more tuned performance with a SERT with several maps but just the one setting is much better than running really lean and hot all the time.

Just another opinion form someone - I`m still reading all posts before I make my decision - but to be honest, everyone who posted here that uses it has not reported a problem so even it it is`nt doing anything, it does`nt appear to be hurting anything either.

I do understand FBRR`s arguments but there`s a difference between the price of a SERT /Power Commander and the XiED and if I`m not racing do I really need one - I`m just looking to run cooler.

 

First of all there is NO one A/F ratio for best power!

The fuel requirements for high load ( or near WOT) are very different than part throttle. ( That too is not a guess but years of dynamometer development)
If you look at JUST WOT A/F ratios, the MBT ( Max. Best Torque) A/F ratio changes from low speed to HIGH speed. It is very dependant on chamber design. And in many cases you will reach the KNOCK limit of a "squish" chamber before you can reach MBT at many speed and loads.

Just as an example:
The last engine I did for production had Power enrichment A/F ratios that started at 13.4 ( for MBT at 800 RPM ) and went to 11.8 at 6500 RPM.
So just setting ONE A/F ratio across all speed and load ranges is not "optimized" or tuned for best power.

Running an engine richer than needed not only wastes fuel, but also can be a lose of power. Stoich A/F is complete combustion. That point of stoich is dependant on fuel.

My comments on fuel control are based on experience not conjecture.
( And knowledge of how the software actuallt works, not guess work.)

Hope that helps.
Cheers

 

It does help - I guess that`s why the XiED web site recommends the 14:1 ratio for a sportster rather than some of the other lower ratios for bigger bikes - I don`t want to (as you said) run richer than needed.