ESE's works engine tuner

[wobbly]

How steep is too steep - depends entirely upon the belly diameter and the end use.
In your case Neil, your pipe will not be fat, and as you are needing wide range power then changing from 18* to 24* will kill all the bottom end dramatically.
There is never a free lunch, and even using a two or three angle rear in your application, everything you gain in front side and top, is taken away from the bottom.
Then there is the issue of overev.
Again, your pipe will be " long " and the shallow rear cone combined with that length easily allows a wide flat band of power, running into overev without shutting off hard at all.

[Flettner]

How steep is too steep - depends entirely upon the belly diameter and the end use.
In your case Neil, your pipe will not be fat, and as you are needing wide range power then changing from 18* to 24* will kill all the bottom end dramatically.
There is never a free lunch, and even using a two or three angle rear in your application, everything you gain in front side and top, is taken away from the bottom.
Then there is the issue of overev.
Again, your pipe will be " long " and the shallow rear cone combined with that length easily allows a wide flat band of power, running into overev without shutting off hard at all.

It's 18 at the moment and has excellent bottom / mid range (with the powervalve in operation) but does go a little flat around 11, 000. I want more but don't want to fuck up what I already have.
My pipes mid section are equivalent to 114mm dia.
My next cylinder (54×54) will have 90mm (×2) mid section. This is the engine I'll run my pipe 'warping' system on. Haha, perhaps I'll call it Warp Drive.
It will also be a disc valve engine with my 'sliding gib' arrangement. Because of rules, it will have to stay carburetored unfortunately.

[F5 Dave]

Is that related to the steamer collapsing thingy you posted a picture of Neil?

[F5 Dave]

Could the powerjet of the very lean carb be an injector?

[wobbly]

Two 90mm pipes on a 125 = 127mm single pipe.
That certainly isnt fat, but is a little bigger than most 125 MX pipes, so could probably deal with a steeper 24* rear cone, especially with a PV and the Gibbs in action.
Again, this approach would need a shorter overall TL as well, or it will make more upper and peak power, then fall flat off a cliff before 11000.