But my guess is that 90% of us (me included) ride at less that 20% throttle most of the time so real world - it's all a bit moot.

Interestingly a mate put a Data logger on his Rocket, when we went for a ride, the entire trip I don't think he exceeded 8% throttle opening ! :eek: And it showed up some interesting A/F ratios !
 
IMHO, because the Rocket needs so little throttle for normal speed street riding, the MAP and throttle position sensors are too "coarse grained" to adequately control AFR, especially when un-restricted and the timing tables are changed accordingly. The difference between 2% and 8% in throttle positions in the Rocket is vastly different than in a 4cyl Nissan automobile, which to equal the desired response is probably close to a 25% change in the Nissan. Add to that a lack of a plenum, which adds volume reducing the pressure fluctuations between an individual cylinder's valve opening events and then between cylinders' valve events. The sensor and ECU have more time to measure and respond to averaged pressures in a plenum than the real time pressure changes in a single TB runner. Hence, any deviation from normal in the Rocket's TPS's operational characteristics is felt immediately by the rider and shows up in AFR deviation, where as in the Nissan a similar change isn't felt at all.

Sometimes, I ride at steady slow speeds one gear higher than I care to just to reduce the sensitive, even twitchy throttle response (in part due to very rapid AFR changes.) One of these days, time permitting, I am going to add an adjustable volume accumulator between Map sensor and the three-way hose tee. By buffering pulses between cylinders, the Delta P processed by the ECU will be reduced. It will be an interesting exercise.
 
IOne of these days, time permitting, I am going to add an adjustable volume accumulator between Map sensor and the three-way hose tee. By buffering pulses between cylinders, the Delta P processed by the ECU will be reduced. It will be an interesting exercise.
It will indeed. Give me an idea of the volume range required ;) centilitres, decilitres?
 
I am thinking centiliter range approaching a deciliter. The hoses already do act as buffer, but more volume may be better for improved operator feel though likely at a detriment to emissions control.
 

David freiburger (long time editor of hot rod magazine) and Steve Dulcich (engine Masters magazine) do a show where they dyno test different theories. The above linked episode they put different sized headers on a mild small block Chevy (if my memory serves; been a while since I watched it). Anyway, the gist was that oversized headers really don't hurt anything. I was surprised by the results. Not real hard science, and clearly not rocket specific, but it changed my view on how much to worry about primary size. Bigger isn't always better, but it's generally not worse, either.
 
Well, I re- watched the episode this morning, and clearly my memory sucks. The biggest header lost about 1% at the low end, and gained very little. And it was a 550hp 400ci. That said, you won't feel 1% on the street.

Another thought, their engine displaces 50ci/ cylinder, and makes about 70hp. A stock rocket displaces 47ci/ cylinder and makes under 50hp. Power bands of both engines peak around 6000ish. The 400 made the most power with a1 3/4 primary.
 
I am going to add an adjustable volume accumulator between Map sensor and the three-way hose tee.
@Speedy
Spurred on by others, I am looking at options. Think I am going to prototype using C/F tubes that sleeve into each other (makes volume adjustment a cinch).
Would you fit the plenum "inline" - or via a "T"? - My gut says inline, but a "T" would make plenum location a fair bit easier.
 
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