The computer learns by itself by adjusting to knock. The fastest way to make knock occur is generally WOT. Once the engine is warmed up, floor the throttle in a lower gear before shifting up, likely freeway on ramps or on the freeway as a pulse after a pulse-and-glide. I generally get stuck like a sardine in traffic, and am limited to roughly 200 ft "sprints" so I just let my GE slowly relearn over 3 tanks. Although the torque increase was still noticeable within the first 100 mi.

 

I didn't feel that on a base GE I borrowed. However, I didn't have it long enough to experiment with, or do more than generalize about ATs.

 

I found this HowStuffWorks "Premium Gasoline and Engine Performance" and a half second is worth 10-15 hp or more in a race car. Ive felt the better shifting but thats after a few tanks so the ecu adjusts.

 

Found a face book explanation to adaptive learning ecus. Understanding Adaptive ECUs (again, more pathetic oversimplification) and using fuel additives | Facebook

 

Great article! Now I'm curious does any of these small mods like intake, exhausts make any difference...does the ecu just compensate to keep the fit within the manufactures settings? How can we reset the ecu without just reseting the factory settings? I feel cheated that I can't control my own computer on my car.

 

It seems like after doing a new mod you should reset and run the piss out of it to get the most out of the factory settings...if hp is what one is after. I don't know much about it, but that would seem logical to me.

 

The ecu is not set up for max hp. When running premium you will get max torque for the fuel air of 14.7 at full throttle. You can do bolt ons up to 10/15 percent more HP before the ecu cant run them then you need bigger injectors and a fuel injection controller.



Dont know what the additive is but I can guess its a product like vicson that the military used to prevent jet fuel from exploding but found out it makes the fuel burn more complete.

 

It looks like good stuff especially for a racer. I may have got off the subject a little, but I think the conclusion is that the change in octane would be something that would be noticable and would be learned by the ecu after a few tanks. I think when gas drops to about $3.50 I will do some testing of my own.

 

I come from the mind set to use 87 and if the engine starts knocking because of weather or the age of the vehicle you give it higher octane...many vehicle manuals say this. You have made a strong case why to run higher and I think I may change my way of thinking on this and like you said what is a few extra bucks when it costs $40 to fill the tank. the benefits present and long term out weight the two bucks per tank at the pump. thanks for all the info.

 

Wow! I told SilverBullet that I thought that there were a lot more open minded people on FitFreak lately than I have seen in the past.... You should be able to feel a difference in torque at lower RPM and need less throttle to accelerate or maintain speed.

 

I put in regular like the owners manual suggests. Why shell out an extra few bucks for a higher grade just to feel a difference in "shifts"?

 

Hey Coyote, new faces are beginning to see the light. Took Silver and a few others a while to get me on board, but this old dog is a believer. I've felt the difference and continue to run high-test. I have monitored fuel trims and haven't seen that premium fuel changes them, but the timing advance is certainly up - over 50d at times.

Lot's of folks believe all gas comes out of the same hole in the ground. Grade and brand of fuel are quite important. Personally, I like to pay for Sunoco - 100% domestic fuel as well as being the fuel of NASCAR. My FIT runs well on their 93ultra. BP is also 100% domestic, but no where to be found in my parts.

I'm curious as to why it's near impossible to see where gasoline companies draw their market lines.

 

Keep an open mind is all I can say. It will catch you after a while. How many miles on your Fit?

 

JDP36 There's no Premium Gas Stazi running around, you are free to do what you like. But your statement is a gross oversimplification of what actually occurs when using a gas blend rated at AKI 93 vs. 87. What you are referring to is the amount of timing allowed during the particularly knock prone areas where an auto trans is changing ratio and the TC is locking/unlocking. The amount of timing before and after can and will have a significant effect on how the car performs during and after the shift. There is actually a separate table for this in our ECU.

This is just one facet of what is occurring.

K_C Fuel trims really only tell you how the engine is compensating for various conditions, or how close you are to reality when dialing in a new tune in terms of VE and Injector/Fuel Pressure settings.

I wouldn't focus on them too much. Timing and O2 volts should show you what you are looking for!

 

My fuel trims fluctuates but returns to -3.1 winter or spring but will see what summer brings. Cars are complicated and I have learned why instead of just believing. I think the biggest mpg gain is that acceleration is faster with faster shifts and more coasting with the 1-2 percent from the gas alone which add up to 10 percent for me. Ive used Sunoco and its very good, and very similar to BP but using Bp the mpg is easier to maintain probably because of butanol instead of ethanol.

 

Yes, simple. I'm not sure if ECU microcontrollers are at the point whether they have enough performance to dynamically create a knock-limit ignition-timing-advance vs RPM map for the fuel actually in the tank...

It would be nice to see some documentation on whether the knock-limits for lowest-possible-or-tested and highest-possible-or-tested fuel octane are fixed values...to which the ECU has to decide one one or the other. Or whether the ECU has enough clock cycles to analyze inputs and create an advance vs. RPM knock limit for the actual octane of fuel in the tank.

It's not shifts. Old systems were designed for worst case conditions. Modern electronics allow for fine control over multiple inputs including octane.

With automatic transmissions and the need for more cell-phone-talk-time, etc while driving, the ECU can properly handle things so consumers don't have to worry about operation. However, it's up to the consumer to decide whether they carry too many people/stuff, drive up steep hills, want better acceleration, etc where the improved torque curve from higher octane helps.


I suspect it's lack of control over the source of base fuel. Locally, my major refinery is Chevron, and that is what I use. I believe it's best to use the brand from the closest local refinery which should also be a major brand, rather than a brand or base fuel shipped from elsewhere or even competitor brands derived from the local refinery's base fuel.

Although there should be multiple safeguards against poisoning competitors, and to ensure quality is about the same, I suspect more care is taken with one's own brand. Top tier brands should guarantee some level of additives, but the refinery operator should know their product or base fuel the best (in order to add the correct amount/type of additives). However, I don't know how refineries work, so maybe my assumptions are off.

 

From my experience, it's been that the ECU will run as much timing as the fuel and atmospheric conditions will allow before knocking. Then it backs off timing and enrich the mixture to where there is a bit of margin for error.

That is at least what I have seen in every car I have ever tuned, as well as what my OBD2 Logger reported.

Most ECU's assign an arbitrary Octane rating (they may not use that phrase but it comes up in several setups) using an arbitrary scale, like 0-255, where the 255 tables were calibrated with a 100RON fuel and the 0 tables were done with 90RON.

In some ECU's, not necessarily the Fit's ECU, every time the computer registers a KeyStar value of 1, the octane rating is reset to MaxOct or 255 from my earlier example. Then the knock sensor ultimately dictates where that ends up.

 

Here is what Hondata has to say about Honda knock control. Knock control tables

 

I'm off watching the trims. What should I be looking for on the timing/O2?

BTW your car's looking good.

 

KC look at the knock tables again. My car operates in MBT of the graph but at full throttle I seen as high as 28.5 degrees of timing with a max of 47 at light throttle. DSM needs to explain O2 volts, I understand it a little.