Hello,

If the HD Street Tuner fuel ratio is limited to the 14.4 - 14.6 range below 3750rpm (what I've read), what benefit is it to add more air to the engine on a Stage 1 upgrade ?? Would not a Hi-Flow AC cause the engine to run even more lean with all that extra air flow?? Is not the ECM controlling the AFR at a EPA approved level of 14.7 on a stock bike?

It's not like having a Power Vision tuner that could adjust the fuel ratio to a lower number so as to balance/compensate for all that additional air from a Hi-Flow in order to make more power.

regards,

 

I don't have my HD Street Tuner software accessible but I remember the f/r going to around 13 to 1 WOT right where that extra air flow is needed. Possibly some more knowledgeable can verify my memory that at some point the system goes closed loop with set a/f ratios that are well down in the low 13s.

 

This is interesting as I do a lot of car tuning and in gneral for a naturally aspirated, pump gas engine: 14.7-1 is considered stoich, that would be seen during part throttle cruising. Peak torque (maximum brake torque) would be closer to 12.5-1 and peak power would be in the low 13-1 range.

Foe those in the know- are HD's tuned to these general AFR's or are they different? Almost all modern cars use wide band O2 sensors now and tuning is based off 1.0 as stoich instead of 14.7-1, wide band sensors are much better for fueling (mapping) tuning.

 

Yes, the street tuner does go to a richer AFR at WOT (and above 3750rpm). But I would venture to say 90 plus percent of riders both shift at and cruise below 4000rpm (except when passing?).

So for 90% of riding what is the benefit of a Hi-Flow AC with a stage 1 upgrade?

regards,

 

Stock map stock bike.
Stage 1, 2, 3, 4, etc maps are adjusted to run within the parameters of those modifications. The amount of fuel needed on a 50hp engine to reach a given afr is different than a 100hp engine. That's what the maps do.

 

Totally agree IF I was running a Power Vision tuner.

Again fellow members, I truly want to understand. On a stage 1 build how does introducing 20, or 30, or even 40 percent more air flow and only .2 percent more fuel with a HD street tuner not make the engine run even leaner then a stock engine below 3750rpm?

regards,

 

don't the 02's provide feedback to the ECM in closed loop to compensate/adjust to achieve 14.7?

 

Hoped you'd chime in.
What I've read on HD's tutorial site for the Street Tuner is that the map fields below 3750rpm are set for the O2 sensors to adjust/regulate the F in AFR at 14.6 with their Stage 1 map.

And say for arguments sake, a Hi-Flow AC provides 25 percent more air over stock. How am I not, in reality, running leaner. Don't I need more fuel to match the higher percentage of air now delivered to the engine? Am I missing something??

regards,

 

I'm not a tuner nor do I intend to pretend to be one on the internet..just a very limited understanding so deferring your question to the subject matter experts on the forum..i just think the efi/electronics, etc. do what they do to make sure the cruising range stays EPA compliant..beyond that think the values are fixed but I'm not sure how all that works

 

I've tried alot of AFR ranges and 14.3 is the sweet spot for my M8 under 4k rpm's