Hitchcocks Forum

sometimes, i swear, i am almost the only american that knows how to tune an engine...

Anyway... i have 39.7 HP theoretical @ 175 psi @ 5K5 rpm

flame front speeds are difficult to calculate;
but just roughing it out, i would not recommend pushing the 535 past it's stock rev limit ... that's a 9cm stroke.

engines can outrun their flame fronts,
( the rev limit should be at the rpm beyond which the exhaust valve would be opening while the charge is still burning )

so idea here is a Max Power Stoich Tune;

that's how i tune, because:

1 ) i don't like wrecking engines

2 ) the fact that liquids don't compress;
is no reason to use a rich mixture to artificially increase the compression ratio, with wasted fuel.

3 ) outrunning the flame font by using a mixture too rich to fully combust to blow the flames off your exhaust valves, might keep your valves from seizing for awhile; but your not making anymore HP up there in the flat line past that, just making smog that no one appreciates, with wasted fuel...

granted...39.7 HP is Theoretical...but let's shoot for 38 peak..

this is a meticulously polished chamber and crown, high test only, go at it..

i am talking breaking any sharp edges on the spark plug, with worn out 400 grit wet/dry, here...polished.

One of the advantages that our UK models have is the under seat B.P.D.F. It helps immensely.

anyone who follows this with a carb;

you can get an A/F ratio meter with an O^2 to swap in for tuning.
( 14.7 is Stoich, and you want the number to be that, or a little less )
after it is warmed up, just try to keep it above 14 if you can.. but don't go over 14.7

i do not condone exceeding the stock rev limit, so i am not going to talk about that.

i don't have a RE 535 CGT yet, ( i will let you all know if that works out )

just studied the design for awhile, and need some numbers to get my virtual 535 dyno running, so i can start tweaking it up.

mainly i need:

1 ) Rocker Ratio
2 ) stock cam timing data
3 ) length of the intake runner ( from the mouth in the air box to the valve stem )
4 ) approximate exhaust length ( from the end of the pipe, with the muffler off, to the exhaust valve stem )

also see my other thread here entitled:
"535 Horse Power Upgrade ( Mono-Directional Crankcase Breather )"
i am hoping Hitchcock's picks that up, and has a product available in kit form, if the proto gives some go..

Duke of Wybourne. wrote: ↑

Mon Jan 31, 2022 10:50 pm

One of the advantages that our UK models have is the under seat B.P.D.F. It helps immensely.

i have to ask you to de-cript the acronym ... i am new here.

If you're going to calculate inlet pressure wave trumpet lengths, I can save you some time. You'd need to start by offsetting the rear wheel.

If you off set it by 5/3" you should be about right
But then you would need a 4" trumpet

is "B.P.D.F" some sort of closed loop auto tune box for the ECU ? ... am i supposed to guess ?

stinkwheel wrote: ↑

Tue Feb 01, 2022 12:20 am

If you're going to calculate inlet pressure wave trumpet lengths, I can save you some time. You'd need to start by offsetting the rear wheel.

5/3rds and 4" intake trumpet .

i will get an MT-03, and hope someone get's something out of what i wrote here someday..