60 hp club

[timbomoose]

Actually the dip and curve was changed from a differnt cam grind. I modified the stock cam and used a diffenent cam timing for the opening and closing of the valve. Have dynoed other ones with the duals and the dip was still there and fell off at the same rpm, but gave about hp from 8000 to red line and the same power 8000rpm and less. The next mod that I'm trying is the same opening and closing timing as this but a more agressive lobe.

[timbomoose]

"Ya I really like it! At first I didn't know if I made a good choice trading my honda for it but it was just the stator so not a big deal there. Ive been thinking about sending my motor to you so you can port and polish it! I can't let stephen be faster than me and right now I'm right there with him. I'm going to be racing mx in the spring and have also thought maybe I don't need it port and polished for mx? What do you think? "

Sometimes there's a couple bugs to work out but when they are you forget all about them because they're such a blast. For mx its would depend on the track you're riding. With the stroker crank you have you already have some extra hp and alot more torque for the corners. The porting doesn't improve bottom end but ALOT from mid to topend about 8hp. If racing tracks with some straight aways it will be helpful, but even with the setup you have now should be competetive with alot modded quads out there and from the way Steve says you ride they better watch out. Keep us all informed on your season in race reports.

[wayneschofield]

QUOTE (timbomoose @ Nov 21 2007, 08:10 PM) <{POST_SNAPBACK}>

Actually the dip and curve was changed from a differnt cam grind.I modified the stock cam and used a diffenent cam timing for the opening and closing of the valve.Have dynoed other ones with the duals and the dip was still there and fell off at the same rpm,but gave about hp from 8000 to red line and the same power 8000rpm and less.The next mod that I'm trying is the same opening and closing timing as this but a more agressive lobe.

(For the benefit of readers as Timbo no doubt knows already)...... Dips and peaks are caused by pressure waves travelling up and down the intake and exhaust tracts and the way they interact with the cylinder on the overlap phase (helping or hindering the cylinder scavenge). Change the resonant lengths or the cam timing and the dips and peaks are likely to move.

The main 'culprit' is the very strong pressure wave that sets off down the exhaust system as the exhaust valves open when the piston is part-way down the power stroke. There is still a lot of cylinder pressure at this point and the 'bang' going down the pipe is reflected by the silencer (usually) as a returning positive wave (the pipe-end reflects it as a negative).

At certain rpms this positive wave could arrive back at the exhaust valves when they are just at the end of their duration, when the inlets are also open (the 'overlap' period). This hinders cylinder scavenging considerably, keeping spent gasses trapped in the cylinder, and often making a strong 'barking' sound in the intake (also causes lots of 'stand-off').

If you make the pipe longer it takes longer for the wave to return and, by that time, the valves may have closed, so you would not get the dip (at least not at the same rpm).

Likewise, if you make it shorter, the wave may come back before the overlap and be 'pushed away' by the gas exiting the cylinder being pushed by the piston. Just 'behind' the strong positive wave there is a strong negative, and this can be used to help scavenge the cylinder, and this helps to make more power.

When the positive wave reflects off the open end of the exhaust it returns as a negative and, by 'tuning' the exhaust system in the correct way you can optimise the power delivery of the engine. This goes for the design of the silencer as well as the pipe length.

Clearly, with such a close interaction between the pressure waves in the pipe and the valve's opening times, changing EITHER the cam timing OR the exhaust/intake lengths will change the position of the dips and peaks through the rpm band.

Often engines are designed so that when the exhaust is working to help the breathing at a particular rpm, the inlet is such a length that it is hindering performance at the same speed and vice-versa. This makes for a 'smoother' power curve as one 'peak' counters the 'trough' of the other tract.

By making a change of either length in this case 'peak' power can often be improved considerably but, as the 'trough' before and after the peak is usually deeper, the 'area under the curve' is no better.

Area under the curve through the rpm band that gearbox forces the engine to use is the real measure of performance, not just the 'peak' power......

[cannondale27]

I just hope to join this club in next week or so!

[Happyboy]

60hp ain't nothing no more. Join the real men's club. 70!

[timbomoose]

This is the natural non steroid method of 60hp and is rare without the squeeze of juice just I just missed 65 by less then a pony and a 1/2. 65hp is a dyno run away I believe with the changes I made. Later going for the unlikely goal of 70hp with the big mouth head and a little engergy drink of U4 more than like won't happen but gotta set your goals high. Look out because after so many runs the nos seringe runs out,but the natural way keeps on PULLIN and PULLIN! 65hp setup is finishing up its diet before motor install to be a lean mean all brand stomping machine!

[sillysspeed]

Dang!!!!! I'm guessing you have a monster throttle body to support it...

[cannondale27]

He made one to match!

My Ti valve stock stroke 450cc motor didn't make the 60hp mark. Bummer. 56hp race ready. I am determined to join this club soon if not hand the Nitrous bottle over

[cannondale27]

13:1 480 Timbo stroker single Aaen exhaust.Run on TurboBlue race ready.Oh so close but still not there.
[attachment=10382:480_Race_Quad.jpg]

[cdale55]

Thats sweet !!!