BHP with a reed valve?

[druist]

How much roughly would an imola 186 or similar reed valve system, differ in terms of BHP or mph gain to a 175 with basic tuning (blueprinting and a basic tuning) 28mm phbh carb, expansion pipe?

[Knowledge]

Drew,

You may see no BHP improvement with a reed valve over piston ported engines. In fact, you'll probably see more peak power out of a piston ported scooter (think of Keith Terry's sprint machine, or even Charlie Edmonds group 4). However, reed valve does have advantages in low and mid range performance, as the reed reduces overfueling. This should be evident in a comparison of dyno graphs.

Where reeds have a distinct advantage is what it allows you to do in addition to reducing the over-fueling. For example, 360degree inlet timing can be achieved once holes have been cut into the skirt of the piston. Boost ports can be cut from the inlet into the top of the barrel, as can feeder ports into the existing transfers. These improvements all help boost bhp, but reed valve alone does not. Afterall, a reed in the inlet manifold is a restriction......

[druist]

Martin, thanks for the explanation. I was curious (not thinking of buying one though) seeing claims that are on the good old LCGB http://www.lcgb.co.uk/workshop/bolton.html where 24bhp is mentioned which i couldnt quite see how it got to that from 15bhp just through tuning alone. Is this more of a wild claim like many car manufacturers make eg it will do 120mph when in fact 100 is all you will get unless you go over a cliff, with a strong tailwind?

[shocky]

im sure 24 bhp is achivable but at what cost ....... lowdown and mid range for one prob has peak power at 8-9000 rpm and a very narrow powerband with no torqeu bellow this effectively a full race engine piston life will be very short as will crank life, the gp4 scoots that stuart day races has a new piston every race at over 100 quid a time
the old gp 3 scooters(standards up to 158cc) were very hard to ride compaired to the gp4 200,s as then needed loads of revs of the line and a very close ratio box and had to be slammed through the gears to keep them going i suspect a reed version of this or 186cc will have better low down grunt but would still need to be thrashed to make the most of its potential ,fuel consumption would be bad as well as would clutch life

[tony]

I'd agree with martin. The reed motors are nicer to drive too. I'm not sure what martin means by over fuelling tho..but he is right about the power delivery. What happens with a large inlet timed motor is bad carburation low down, poor port flow low down. You need some clever thought to get the thing to work well at low rpm with big inlet timing.

[FrankF]

I'd agree with martin. The reed motors are nicer to drive too. I'm not sure what martin means by over fuelling tho..but he is right about the power delivery. What happens with a large inlet timed motor is bad carburation low down, poor port flow low down. You need some clever thought to get the thing to work well at low rpm with big inlet timing.

Fluid diodes seem to work well on piston ported engines at low rpm instead of a straight inlet manifold. Maybe one day it will gain more intrest as a type of inlet manifold and maybe see diodes manufactured, instead of the people who are using this type of inlet tract having to bodge thier own.
Dyno tests on small RC airplane engines i.e. have shown a 25% increase in scavenging and delivery ratios, and in the one I played with it cured most of the blowback from an over-timed inlet port on a 190 barrel, but I never got as far as taking it to a dyno, so it could have problems in other rev ranges; eg lower BHP at higher revs.

[sean brady scooters]

heres a bit of a read/info as regards fluid diodes
http://www.kiwibiker.co.nz/forums/showt ... 1129286737

[drunkmunkey6969]

Ben at AF has a cylinder that he's been toying with, using a diode set-up.....has had a few problems though, not sure what.

[RinB]

Problems with these on lammy is the room to get forward & reverse track flow angles & size right, plus the expansion bowl size being the correct ratio of the diameter of the inlet track

Its nothing new Japs been playing with these since 71 ish Ive got a paper on it if any one is intrested PM me

[J1MS]

Problems with these on lammy is the room to get forward & reverse track flow angles & size right, plus the expansion bowl size being the correct ratio of the diameter of the inlet track

Its nothing new Japs been playing with these since 71 ish Ive got a paper on it if any one is intrested PM me

I'm Interested..!! PM sent...