Intake length

[delray]

just found this old thread and thought i would revise it with my intake i made away back for my built clone engine. i originally only intended to make this intake to help keep my carb hanging out and possibly getting damage from trail riding it. i no longer have this setup on my fox bike and now have it on a drag bike that run's 125ft dirt/clay. i see alot of positive feed back on long intakes. with this intake setup on my drag bike it pulls so hard that it will lift front tire off the ground the first 10ft about 4-5inch with a 130 pound drive(kid,my driver) and then come back down. my question is . this type of intake that i made with a forward design forcing cold air into it have a big part in making this engine run so good at 125ft?

 

[fistfullabar]

Sorry i got no info but if you come up with a good design for the ohh tec on the thunderbolt for a intake i would like one also. Im got the same bike now:laugh:

 

[massacre]

delray-

IMHO it is far more likely that the length of runner made power, over the "ram air" effect of the forward facing filter. I forget what speed you would have to reach in order for that to become effective, but I would think it is faster than minibike speeds. I could be totally wrong though but it's my suspicion.

 

[control4userguy]

I prefer longer

Where's Michael Scott...

 

[FirePowerMinis]

delray-

IMHO it is far more likely that the length of runner made power, over the "ram air" effect of the forward facing filter. I forget what speed you would have to reach in order for that to become effective, but I would think it is faster than minibike speeds. I could be totally wrong though but it's my suspicion.

He's right, you know. lol

In the late 80's when sportbikes were developing rapidly, plenty of testing was done. I think a Gen1 ZX7 broke even in the 120mph range. A mini would have to be tossed off of a pretty tall building to achieve any variance in intake pressure/vacuum. Cooler air, to the tune of 1% added power/10f temp drop, as well as the pulse tuning, would certainly add power. These engines, with a few wild exceptions, are port/valve stingy. Packaging and emissions are the OE design targets, not optimized cylinder filling. Compression and quench help some areas, hurt NOX output. Runner length has become more useful, even OE autos are using variable length setups. I feel these can use the help, too. I'll be doing some testing on my GC160 as it's ideal for a long straight tube that's easy to chop.

 

[Newoldstock]

just found this old thread and thought i would revise it with my intake i made away back for my built clone engine. i originally only intended to make this intake to help keep my carb hanging out and possibly getting damage from trail riding it. i no longer have this setup on my fox bike and now have it on a drag bike that run's 125ft dirt/clay. i see alot of positive feed back on long intakes. with this intake setup on my drag bike it pulls so hard that it will lift front tire off the ground the first 10ft about 4-5inch with a 130 pound drive(kid,my driver) and then come back down. my question is . this type of intake that i made with a forward design forcing cold air into it have a big part in making this engine run so good at 125ft?

][/url]

I made one something like that a long time ago.
Most of my curve was on the side with dense air up stream of my carb.
www.oldminibikes.com/forum/photopost/data/500/thumbs/20150607_102045.jpg[/img

What a mess....
I will never ever ever ever post a picture here.
OldMiniBikes has no taken my pictures and I can not even link them properly let alone delete them if I want.
In short I made one guess what it looked like....

 

[CarPlayLB]

A longer runner makes more torque down low. That is why most new cars have a long intake track. Look at an older 5.0 Furd or a TPi Chevy. The runners were long so you had more power down low, with a sacrifice of high rpm's, which street driven emissions cars do not need.

The big mistake we see here with people building engines is too big of cam and too large of a carburetor. Intake velocity helps fill the cylinder. Lose your vacuum and velocity and the engine would be a dog!

 

[delray]

fistfullabar

if you come up with a good design for the ohh tec on the thunderbolt for a intake

if things go well for my ohh-tecumseh. i just might have a crazy intake on it. lot little modifications bring done to that engine i have never seen anybody else do. time is ticking and windber is almost here......:doah:

 

[delray]

FirePowerMinis

I'll be doing some testing on my GC160 as it's ideal for a long straight tube that's easy to chop.

that will be interesting to see. it won't really replicate whats going on with my engine,but still very interesting to see your results.
i maybe be wrong on this, for example if you had a engine built for performance application and your carb was mount right up to the head.
wound it act more like turning a faucet on and not allowing fuel to optimzer as well if it was a longer intake. i know it's kind of a open question.

 

[FirePowerMinis]

FirePowerMinis

that will be interesting to see. it won't really replicate whats going on with my engine,but still very interesting to see your results.
i maybe be wrong on this, for example if you had a engine built for performance application and your carb was mount right up to the head.
wound it act more like turning a faucet on and not allowing fuel to optimzer as well if it was a longer intake. i know it's kind of a open question.

I just came back from recycling where I pulled the intake and carb from a Tec Powersport. Coincidence or sinister forces? lol

Atomizing takes place before leaving the carb and drops during travel through the manifold more than mixing better. Now, some hi-rev engines are moving injectors farther back and it aids charge cooling, but that's a pressurized mist, not a suction deal. Long/short-ram Mopars had heated plenums to help atomize in colder temps. So, LSS, runner length is more for timing the resonance of wave strength at valve opening. Runner area, valve events, RPM and which bounce you want to tune for are all factors to determine desired length from valve seat to atmosphere.

Some real basic calculators: Intake Runner and Peak Torque Calculator

 

[delray]

seeing alot info coming up with long intakes help improve low end and that is one thing i really note on my bike that it pulls real hard when taking off up to mid range at 125ft on clay/dirt.