Bigger Power Valve?

TwoStroke Institute · Post by **TwoStroke Institute** » Sun Aug 16, 2009 9:53 am

HERE is a hint

JanBros · Post by **JanBros** » Sun Aug 16, 2009 12:09 pm

TwoStroke Institute wrote:HERE is a hint

any idea off power-output off that engine ? max rev's ? useable power range ?

just to have an idea iff data/exhaust could be used on a KR

or do you know what formula's/programe best to use to calculate expansion chambers ?

mj43 · Post by **mj43** » Sun Aug 16, 2009 12:32 pm

TwoStroke Institute wrote:There is an easy 2HP gain per cylinder in the exhaust duct outlet.

Have you tried this or are you going to try it?
Never known 4hp to be easy to find - but that would be a monster step up.

TwoStroke Institute · Post by **TwoStroke Institute** » Sun Aug 16, 2009 2:50 pm

After vin posted the RS 125 website I stand corrected it's about 1HP gain having a step over the outlet matching the flange diameters(more precicely not a 1HP loss).I have just started to incorporate this style of outlet into a cylinders I do.So I don't have, as yet some hard data.Still that's 2+HP that's easy to find, I have done a few vintage MX cylinders previously ported with outlet matching the flange with no hump in the port floor.Restoring the hump and step resulted in better throttle response and more mid range.Unfortunately these bikes ain't ever going to be dyno'ed.
The Maxter 125 has about 40HP@14,000 in standard trim(held back by the shitter PVL ignition and the 30mm carb) but the cylinder is as good as it gets.I doubt a belly diameter of 135mm would even fit on a KR let alone be useful.Plus the form of that pipe is dictated to.
Designing a pipe is not just punching numbers into a program and then sitting back. Usually works with a simulator to gauge the results. There are many free downloads to try some are good some are shit.Most are based on the Blair formula's.

JanBros · Post by **JanBros** » Sun Aug 16, 2009 6:00 pm

so which ones are good [-o<

mj43 · Post by **mj43** » Sun Aug 16, 2009 8:46 pm

TwoStroke Institute wrote:After vin posted the RS 125 website I stand corrected it's about 1HP gain having a step over the outlet matching the flange diameters(more precicely not a 1HP loss).I have just started to incorporate this style of outlet into a cylinders I do.So I don't have, as yet some hard data.Still that's 2+HP that's easy to find, I have done a few vintage MX cylinders previously ported with outlet matching the flange with no hump in the port floor.Restoring the hump and step resulted in better throttle response and more mid range.Unfortunately these bikes ain't ever going to be dyno'ed.
The Maxter 125 has about 40HP@14,000 in standard trim(held back by the shitter PVL ignition and the 30mm carb) but the cylinder is as good as it gets.I doubt a belly diameter of 135mm would even fit on a KR let alone be useful.Plus the form of that pipe is dictated to.
Designing a pipe is not just punching numbers into a program and then sitting back. Usually works with a simulator to gauge the results. There are many free downloads to try some are good some are shit.Most are based on the Blair formula's.

Lomas pipes have a 120mm belly and I reckon that is about the limit in terms of ground clearance - unless you introduce flats on to the belly.

At what rpm does the Maxter produce peak power. Found with direct drive karts peak power is about 10000 rpm they just have loads of over rev. OK Maxter is a gearbox engine but still...
If I extrapolated my power curve from 10,500 to 14,000 the KR would make over 80 Dynopro HP which is the best part of 90 Dynojet which is about 100 at the crank !!!!

KR-1R · Post by **KR-1R** » Sun Aug 16, 2009 9:41 pm

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ROUGH ESTIMATE OF PORT MAP FOR MAXTER MX125-04 KART ENGINE (+/- 0.2mm approx)

BUGGER ALL IN THE WAY OF COOLANT PASSAGES

TwoStroke Institute · Sun Aug 16, 2009 11:55 pm

Jan there is a free download on Ian Williams Tuning website that is OK. Want anything better you'll have to pay for it, and even then there are good and bad.
I just had a look and a tuned Maxter is about 46-7HP at 14,000 which is very good for the carb and ignition it's stuck with.The 08 TZ250 Yamaha quotes as 93ps most 250 twin superkarts are 100+HP so that's all pretty fesible. The maxter cylinders are very expensive(like most things 4 wheels) the head/dome/cylinder and cylinder liner are all separate items $$$$$

KR-1R · Post by **KR-1R** » Wed Jul 06, 2011 9:17 pm

TwoStroke Institute · Post by **TwoStroke Institute** » Fri Jul 08, 2011 2:42 pm

What did you want to know?

JanBros · Post by **JanBros** » Sat Jul 09, 2011 9:47 am

TwoStroke Institute wrote:What did you want to know?

is it worth recreating this ?

TwoStroke Institute wrote:After vin posted the RS 125 website I stand corrected it's about 1HP gain having a step over the outlet matching the flange diameters(more precicely not a 1HP loss)

say, I make my own pipes, and in stead off using the seal's, I make an aluminium ring with that step ? what shape should that step have to be, and how many mm's ?

TwoStroke Institute · Post by **TwoStroke Institute** » Mon Jul 11, 2011 2:30 pm

Best made by welding the exhaust duct, say your exhaust duct outlet ID is 36mm, you weld the top and bottom of the duct to get 28mm so then you will have an oval 36mm wide and 28mm high. Usualy 3-4mm is the step. If you have a 36mm ID exhaust outlet 37-38mm header pipe would be acceptable.