lets talk about torque

[davidblythe]

the other thing people forget about is how the torque curve translates through the gearing onto the road

a really useful graph that a dyno can/should be able to produce are thrust curves through the gearbox against speed, they highlight when the power is too peaky for the gearbox or if the gearbox is under/over geared, optimium change points etc

[carlos fandango]

So all that said what makes up a torqey engine as opposed to a revey one... in laymans terms????????

A wide low exhaust port ........smaller carb ....... longer stroke........box / low revving pipe........ gearing.???????

What else????? compression...transfer timings/area????

What effect would welding the casings up and opening the trans. up ?? torque or rev???

Im im looking at a torqey engine as my next project for spain ive got a welded up 200 casing, rb250 barrel (F@@ked), 60mm alpha crank, jl3 and jl4 .
Thinking of a 70mm steel liner (with the 60mm should be 230cc ) welded up ex port single bridge.

All advice welcome
thanks
Russell

[davidblythe]

always cracks me up when you see a graph with the cross over point elsewhere in the rpm range

Ours cross at 5252......and i like it that way........but when you see graphs that dont, its only because they are using different scales for bhp & tq.

On such graphs, if you check the ft-lb reading at 5252 and the bhp reading at 5252......they will both match.

an example this weeks MCN have done a 5 way dyno test with the BMW S1000RR, showing the BMW tops with 183bhp, compare the torque graphs and its all nonsense

BMW must have paid a fortune for the advertorial

[cezeta]

me and my brother are off to the land of flat caps and clogs in the new year to get the ball rolling on an mbd 255 rt. mark sent us a dyno sheet on the rt kit, its darrels engine v marks isle of man carbon deposit racer with a 255 monza motor.

give or take a bit for differances between dynoes, it looks good so far? torque is high and the 5k torque bhp crossover is where you want it.

bloody impressive from a piston ported motor, i know some people have said that mbd dont publish their dyno results.....well i have an in box full of them and asked mark if he minded me posting them on forums to get feedback and he was quite happy for this to happen.

[soosh]

It does seem that these types of motor are hard to come by the way some go on about them.My 185 used 4.8 ratio and pulled two up very well and still screamed and my 200 uses 4.8 but soon to change to 4.5 ratio and that uses a PM pipe aswel.But the guy who tuned them said it was the norm and there is no reason why they shouldnt pull that gearing.The exhaust port on the 200 is wider than a lot may be willing to go so guess that helps aswel.

[Ian Hepworth]

i know some people have said that mbd dont publish their dyno results.....[/img]

Took a lot of lateral thinking on my part.

The dyno computer is still on windows 98 and the graphs look better on the screen than when printed.

Had to fart about burning drivers onto a cd to allow Mark to print dyno screen to file then copy onto memory stick.

There are 100s if not 1000s of runs to compare. Mark and Max spent a solid month playing with RB and TS1 kits, result was tge new racetour tune that works better than the old stage 1,2 and 3.

[cezeta]

It does seem that these types of motor are hard to come by the way some go on about them.My 185 used 4.8 ratio and pulled two up very well and still screamed and my 200 uses 4.8 but soon to change to 4.5 ratio and that uses a PM pipe aswel.But the guy who tuned them said it was the norm and there is no reason why they shouldnt pull that gearing.The exhaust port on the 200 is wider than a lot may be willing to go so guess that helps aswel.

i dont think anyone is saying they are rare, its more about seeking out the ideal rather than ground breaking technology and so as consumers that have gone through various set ups some of us are finding the dyno graphes quite handy in identifying what we want. having had and condemned race set ups and made marks ears blead over the subject we are now asking for and getting what we want more accuratly.

you are right though 4.8 is quit normal, the rt255 will be replacing a rapido running a clubman and 24mm mikuni which pulls 4.6 one up but fully laden and makes quite a nice scooter with only 15bhp so another 10bhp and an additional 7 lb of torque should be quite pleasant. my crappy standard mugello with 12bhp still pulls 4.9.

i wonder what darrels rt255 will pull?

[Ian Hepworth]

i wonder what darrels rt255 will pull?

It'll pull Darrell.

Sorry Darrell, pot calling kettle black.

[bsso78]

Ive never used a dyno to set up a race motor but out of interest i put my Group 4 on Chiselspeeds after i won the championship in '04.
It was only making just over 21hp but it went up to that very low down and held it right through to about 8500rpm on a third gear run,it revved on to about 9500 and dropped to somewhere around 19hp running Cadwell gearing which is about 4.8
Cant remember what ft/lbs torque read but it was quite high i seem to remember,ill have to try and dig out the printout if ive still got it.
This was running a cast Indian barrell with Honda piston,39mm Dellorto,AF Rayspeed crank and exhaust made by Steve Riley who makes exhausts for AF Rayspeed.
I think a lot of people are fixated with high hp figures but end up with an engine which is a pig to ride.
Ive got all sorts of different tuned engines but ive come full circle and use my "standard" for going any distance these days,its running 4.8 and will pull 65-70 but i can hold it flat out without worrying about it blowing up or anything dropping off,as for torque i snapped a gear cable on it and got it to pull away in third

[Train Driver]

[quote="cezeta"]me and my brother are off to the land of flat caps and clogs in the new year to get the ball rolling on an mbd 255 rt.
I think Cezeta might be slightly off with his description of the fine people of Doncaster, if anything they seem slightly grey if this picture of a young mark broadhurst trainspotting and trying to get into the cab of a deltic is anything to go by