Ram air induction

[Kells]

I've been thinking about this for a while now. I went to work experience today (for my automotive engineering course) and since there was nothing on for a couple of hours I told my boss about my idea for ram air induction. to cut a long story short I chopped up a section of radiator hose and after two hours strait of cutting and fiddling with the carb I now have my '90 razz doing 55+ km/h (from ~47).
(both speeds are without air filter)

if anybody's interested here's my words of wisdom (i.e. list of random info.)



ride the scooter before hand to find where the air stream is because if the inlet is too close to the scooter you won't get the full velocity of the air.
it can sound rubbish if you have a really long pipe
you'll most likely lose function of the kick start.
my pipe is about 4-5 inches long.
length is critical!
obviously start with the pipe as long as possible and cut 1/2 inch rings off it. then fiddle with the carb to get the best setting for that length. you'll obviously want to start much longer than mine is at the moment.
from what I gather, the longer the pipe the narrower the power band. this is in no way the definitive rule though.
I've probibally missed something here. just ask if you want to know anything.

[fastrazz89]

Do you have any pics of it on the bike?

[Kells]

I just took this one now

[seanisaboob]

so that actually works ? y dont you put something on it to collect more air ?

[dwsracing]

My razz gets one speck of dirt in carb and runs with a bog. How do you filter it ????

[robotguy]

Sounds like you'll just be running lean,
unless you rejet the carb..

[fastrazz89]

HA! Your Razz is the same wierd color as mine! (click the link in my sig to see a pic of it).

[88 PS190]

Quick thoughts for you.

1. Did you try tuning the carb before you added this component?

2. Did you try running w/o your airfilter or with a nice clean air filter before the mod.

Reason for the thought. Your pipe is an inner diameter of maybe 2.5" At 55 KM/H you really do not have much force on that pipe (lets call it nill because really in the grand scheme of things you are not forcing air into that sucker... sorry but I will bet even at speed that thing is still not pushing much pressure.

And finally, RAM air on cars with much larger intake pipe diameter, going much faster is still considered not worth it. Doesn't create enough pressure to really change the amount of air forced into the cylinder.

And... these things are limited by the CDI... fix that and we'll talk.

[Kells]

My razz gets one speck of dirt in carb and runs with a bog. How do you filter it ????I hope to get a pod filter for it soon. I haven't run a filter for a while but I thought the dirt was in the fuel because it blocks the jet seemingly from the bottom.



Sounds like you'll just be running lean,unless you rejet the carb..that has actually been a bit of an issue, do you just buy bigger jets for the razz?

[Kells]

Quick thoughts for you.

1. Did you try tuning the carb before you added this component?

2. Did you try running w/o your airfilter or with a nice clean air filter before the mod.

Reason for the thought. Your pipe is an inner diameter of maybe 2.5" At 55 KM/H you really do not have much force on that pipe (lets call it nill because really in the grand scheme of things you are not forcing air into that sucker... sorry but I will bet even at speed that thing is still not pushing much pressure.

And finally, RAM air on cars with much larger intake pipe diameter, going much faster is still considered not worth it. Doesn't create enough pressure to really change the amount of air forced into the cylinder.

And... these things are limited by the CDI... fix that and we'll talk.it does seem to make a reasonable difference. I just realized I wrote that wrong and I'll correct my statement. 47 was with the 2.5 tyre. I installed a 3.00 inch tyre and it struggled to go past 50. with the pipe it has quite a bit more torque at high revs.

I'm not saying I have the cure to all of our problems but it seems to make some difference and I am putting the idea out there because to my knowledge nobody has tried it and I thought it might have potential.

[dwsracing]

Now were back too the cdi, the main problem that is still there. So whats the latest on the razz and its CDI ???

[Kells]

I've managed to get 60ish down short hills with a tail wind (km/h) I don't think anybody has managed to get another cdi to work successfully with the razz yet. maybe if we contacted Yamaha?

[dwsracing]

I've tore a spare on down, hard too do, but Im close to done. I have a guy that works on like slots, vidio games, basic repair man for a game room. Lets see if we can find a symatec for the yamaha razz cdi.
Let me know

[Kells]

I've tore a spare on down, hard too do, but Im close to done. I have a guy that works on like slots, vidio games, basic repair man for a game room. Lets see if we can find a symatec for the yamaha razz cdi.
Let me know
lol that reminds me. my classmates decided they'd try to hotwire my scooter a couple of weeks back and started playing around with the electronics and fried the cdi. no skin off my nose cause they paid for a new one, so my mate and I ripped into the dead one. It wasn't pretty though, with bits of resin and PCB everywhere. I can imagine it being quite a tedious job pulling it apart so that you had something usefull at the end. good luck man.

[dwsracing]

Ya, it sucks but its really basic stuff. Look at it this way, Why do people climb mountains, cause their there.

[OveRReV]

ram air won't work with just a tube pointed to the front, you'll just lean the mixture too much & cause a major bog which will make the motor fall flat on it's face.

the proper way to do it is to build an airbox where the carb is fully enclosed so the float bowl is equally pressurized with the surrounding atmosphere & jet the carb a bit richer for the slightly increased air pressure at higher speeds.

for a scooter there is absolutely no need for ram air, it's better to concentrate on areas where real power gains can be had & that is the pipe, porting, crankcase & carburation.

on my yamaha jog mhr team 70cc dragscooter we are making 22+hp at the rearwheel with no ram air.

[dwsracing]

thats great.With the razz we are limited with the cdi. I know get a jog motor, but I have so much razz stuff around. All 5 of my razzs go different speeds ( from 25mph too 37mph)
If I move the fastest bikes cdi to the slowest it becomes the fastest. Guess its in the cdi

[OveRReV]

if you're jog engine has a 2JA or 3GF stator you can use a CDI from a pre-2003 yamaha aerox scooter, it has no rev limiter whatsoever so you can even use it on a full race engine but i much prefer an inner rotor ignition.

[Kells]

the best idea would obviously be to put the carb in a pressurized box with the fuel tank pressurized to the same pressure. but then you've probably got a delay while the higher pressure gets forced down the fuel lines..... maybe it's not worth it. (update, I'm actually running without it now, after a lot of experimentation. it seems to be more reliable. basically what I think I had was the pipe had to be tuned to give power at high revs, so no power down low, and then it leaned out at high revs.)

off topic slightly, my tutor knows a guy that supercharged a 100cc two stroke moped (proper moped) but engine life wasn't exactly what one would call satisfactory. he used an old die grinder / dremel inner core. he would take it on annual moped runs but would have to strip the motor at the end of each day and usually arrived at their destination on the back of a truck.