(Quasar @ Sep. 27 2006,14:09)
(InfiniteReality @ Sep. 27 2006,13:53) Just curious, what kind of RWHP do people put down with only a full system, K&N and PC?
It will fluctuate naturally as everyone isn’t being dynoed on the exact same dyno with the exact same air density/humidity levels. Roughly 165 RWHP can be anticipated, but keep the following in mind…If you tune your Hayabusa’s RAM-Air inducted engine to an absolute peak RWHP while sitting on a stationary dyno, which is missing one of your engine’s essential elements for maximizing its horsepower (its RAM-Air induction), you will have detuned it for street or track use and therefore produce slightly less RWHP, as it WILL be receiving its RAM-Air induction, which further leans the A/F ratio that had been tuned perfect for peak dyno HP numbers.
Yes, the air box pressure will compensate the A/F ratio however, only to a point. The ECM uses predetermined algorithms for the air box pressure it detects. These algorithms are based solely upon the stock fueling tables inherent within the ECM. Therefore, any alteration to the stock map via a Power Commander, Techlusion, Yosh Box, Yosh EMS, etc... indirectly alters the fueling correction factor that the ECM would otherwise apply based upon its air box compensation algorithms. These air box algorithms are merely a percentage added to the base fuel table and this base fuel table is modified by the external fuel remapping device therefore, the RAM-Air compensations are not fixed amounts of fuel added. There is no means to directly alter the predetermined RAM-Air compensation applied by the ECM. That would require reprogramming beyond the abilities of simple add-on devices such as a Power Commander and the like.
This would NOT be an issue if the ECM based its air box correction factor on actual sampled O2 content from its exhaust, as it would simply add (or remove) the appropriate amount of fuel to maintain a peak A/F ratio however, this simply is NOT the scenario on current day Hayabusas. Their air box correction factor remains a fixed algorithm and there is no sampling of the O2 gases whatsoever (at least not on current U.S. models), so at best, its air box algorithms are yielding approximations in the A/F ratio based upon the stock airflow rate of a stock Hayabusa engine and the air box pressures that normally accompany a stock flowing engine.
This is why RAM-Air corrections CANNOT correct appropriately for modified engines and why dynos typically rob the engine of some of its HP potential on the street or track. The engine in a modified, higher flow engine still has the stock RAM-Air (air box pressure) algorithms applied to compensate its fueling, which can ONLY prove itself less than adequate. Making things still worse, is the following...
The air box pressure in a modified engine verses a stock engine is not the same even at the same given forward velocity and the same engine RPM. As you’d expect (but may not have given much thought), the modified engine is flowing more air due to its ability to draw more air. What does this do to the air box pressure? It makes it more negative, as it is drawing more air per second than the stock flowing engine. The more negative the air box pressure, the less fuel compensation applied as per the stock preprogrammed/predetermined algorithms.
So, the modified engine pays the further penalty unless the tuner is wise enough to ADD appropriate fuel compensation rather than remove it as often guided/persuaded 100% by the dyno O2 levels detected during the dyno run.
One thing becomes clear, if you are trying to win a dyno horsepower shoot-out, tuning on and for the dyno is the absolute best method however, if you are attempting to max your horsepower for use in practical application, like when actually riding or running it on the track, tuning from an on-board O2 source is the ONLY way to achieve absolute max usable HP. It is the only method that actually allows you to compensate for the engine’s RAM-Air induction as applied and sensed, to yield its max HP potential. The dyno can NEVER yield a RAM-Air inducted engine’s max HP potential for the street. Until dynos can supply an algorithmically controlled RAM-Air supply of fresh air to a RAM-Air inducted engine during stationary dyno tuning, dynos will remain only a ballpark tuning device. They only get you close but always short of max HP potential. This is why I never get hung up over dyno numbers and why I went with on-board O2 collection on countless Hayabusas with every mod conceivable...
Dyno-tuning Turboed and Supercharged Engines:
On things like turboed or supercharged engines, dynos are a great tuning tool since the engine is in fact receiving ALL its intake air via its forced air induction.