Freez,
The slider was modified as yours.

Did the testing on a old paved rode.
My sons 05 has a tach.
While in 3rd gear, 3000 rpm, then hit the throttle.
Kept drilling the extra holes till tach showed no flat stops.
When holes were small, accelerate fast till 6500rpm,
then flat to 7500rpm, then really slow to 8000rpm.
Kept opening holes till reved great all the way to 8000rpm.
Ended up where you said to go. Hmmm
Tried stock spring and even though it reved to 8000rpm,
it was flat 7k to 8k.
I have the holes maxed out and I did not want to drill another hole.
I think the new spring will be better also for elevation changes.
Let spring pressure control bottom and negative pressure control top.

The needle is what you have been using. In the lowest groove(6th)

The emulsion tube is a custom. It was built for me and at no charge.
This engineer wants to keep the design and I will have to get a price if
I want to purchase more. I was the guinee pig.
I want to do a dyno run to show before and after.
This kit maybe too expensive for the average guy.
At least I am getting this project done. Over an year.
Hard to convence your son to test when motor sometimes backfires.
He doesn't understand that the more mistakes you make, the more you learn.
He doesn't like to be a guinee pig.

 

Who said there has to be a vacuum in the air box to open the slider? (although, if you are running an air box, there is a vacuum in it, otherwise no air would ever get into it). By changing the air box configuration or snorkel, you change the vacuum waive and air speed of the intake tract.

"....are telling you it needs a vacuum to open the carb, when air PRESSURE opens it, NOT a vacuum...."
....." This vacuum is then fed to the breather pipe, then to the carb breather passage, where it competes with the vacuum on top of the slider diaphragm. The two vacuums are competing with each other, causing the slider to open slower and smaller"

so, which is it? pressure pushing the slide open or is it competing vacuums?
hint: not pressure pushing it open, which is why the following statement is true:

".....install a small K&N breather filter on the carb breather pipe. Now you will not have a vacuum underneath the slider and free flowing air can move in there when the slider moves up. This means a smaller vacuum is needed to open the slider and it helps it to move quicker and open larger with less vacuum."

222

 

"If the airbox is flowing correctly, it will not suck that intake pipe closed. The pipe being sucked closed is a sign of poor airflow and a massive vacuum on the intake system. The bigger the vacuum on the intake the less power you will have. "

??? Any ds that is flowing enough air and/or turning enough rpm will suck the breather tube down. It is a sign of GOOD vacuum in the intake system, which is what brings the air and fuel flow into the engine and makes more power (that is unless your running a supercharger on yours).

222

 

"Understand how the carb really works and then you will be able to make that DS breath properly. Jet it correctly and you will get the power. It is that simple."

Which is why it's better for most people to leave it alone! I applaud Oldmanracing (and Freez) for his 1.5 years research to "make" the carb work for his type of racing and class rules- it can be done!
Removing the lid, tubes, and/or airbox moves the horsepower around. Jetting must be changed, which is easy, but it doesn't make any more Peak horsepower, it just moves it back about 700rpm earlier. For a drag race, give me the same power at a higher rpm. If your gearing is off on a hill shoot, the earlier horsepower can help you. Now, do all the work Oldmanracing has done....I can believe he has made it work better, but there's alot more to it than rejetting.

222

 

The turbulence Oldmanracing referred to is the turbulance through the carb, not like airplane turbulance over the bike. Intake tract turbulence is dramatically changed by things such as direct mount filters.

By the way, the fastest Pro Stock bikes are running, of all things, air boxes now! They are special designed and pretty trick, but it gives us something to think about?

222

 

Hightower do you run your 90s pointing down or in or out?I cant tell from you pics.
It almost looks plugged in your seat cover pic.

 

Hi 222. The following was a statement to prove a point.

"....are telling you it needs a vacuum to open the carb, when air PRESSURE opens it, NOT a vacuum...."
....." This vacuum is then fed to the breather pipe, then to the carb breather passage, where it competes with the vacuum on top of the slider diaphragm. The two vacuums are competing with each other, causing the slider to open slower and smaller"

so, which is it? pressure pushing the slide open or is it competing vacuums?
hint: not pressure pushing it open, which is why the following statement is true:

I told people to blow into the breather to show them that it moves up when you blow into it, not because it works like that on a running bike. Blowing air into it, simulates a vacuum on top of the diaphragm. If you blow into it, to move it up, it means it does not need a vacuum on the breather to open it, as some people say it does. To make the slider move quicker you need to remove the vacuum on the breather pipe, which is generated by the intake. Hence me telling people to install the K&N breather and to block the hole on the rubber intake. That way, there is no vacuum under the slider and the vacuum on top of the diaphragm has no competition to open the slider..

Now to your second response.

"If the airbox is flowing correctly, it will not suck that intake pipe closed. The pipe being sucked closed is a sign of poor airflow and a massive vacuum on the intake system. The bigger the vacuum on the intake the less power you will have. "

??? Any ds that is flowing enough air and/or turning enough rpm will suck the breather tube down. It is a sign of GOOD vacuum in the intake system, which is what brings the air and fuel flow into the engine and makes more power (that is unless your running a supercharger on yours).

The more vacuum there is between your motor and the surrounding air, the less air flows, or the more restrictive your intake is. The intake tube being sucked closed shows that the motor is straggling to pull in air, ands the vacuum in the cylinder is passed onto the intake side. If you remove the airbox, install a high flow air cleaner, the vacuum is less between the motor and the surrounding air and the intake tube is not sucked in so much. This means it is flowing more air and the motor is breathing more easily. The vacuum is caused by an airbox and air cleaner that is not able to flow and keep up with the demands of the motor. This creates a vacuum that is so strong, that it now sucks in the rubber intakes. To be 100% correct, the air pressure from the surrounding air is actually pressing in the intake, due to the vacuum inside the intake

You can test this yourself. Take a soft rubber tube, put your mouth on one side and close it with your hand on the other side and seal it off. Suck on it. The pipe is sucked in, because of the vacuum. Now make a very small air opening in the pipe and suck again. The vacuum is less, since air is now flowing into the pipe, and you are not able to create the same vacuum, or dented pipe, as before. Now take that same soft tube, remove your hand and try and suck it closed with one side open. It is impossible, right? Reason being that the tube is now flowing more air that the vacuum you are generating. A motor works exactly the same. If is sucks a soft pipes closed, it means your air cleaner and airbox is restricting. Remove them and it will be impossible for the motor to suck that pipe closed. You cannot run an open intake/carb, so the better your airbox and air cleaner is able to flow, the less vacuum it will have in the intake system. The stronger the vacuum in the intake (not talking between the carb and the cylinder), the less airflow your intake has and the less power the motor makes. Keep the vacuum between the carb and cylinder, not between your air cleaner and the cylinder.

Then to your last post.

Airboxes can be a good thing, but the stock airbox and filter is too restrictive. You will find that the aftermarket airboxes are much larger than the stock unit, and there is more clearance between the box and the air cleaner itself. This is to allow air to move more freely around the air cleaner and creates a uniform surface area for airflow. If the box is small, and air is only flowing from one direction, the filter will tend to flow more air on the side the air is supplied, causing poor flow or one way flow and turbulence.

Then, you will most likely find that the intake between the carb and the airbox is a long pipe, sometimes tapered like the stock DS intake. This is to smooth the airflow and turbulence before the carb. The length has two advantages. One is to smooth the air, as I mentioned, the other is to create a tuned pipe, where shockwaves are generated inside the intake pipe, to aid airflow (RAM AIR). The tuned pipe can actually force air into the cylinder, helping the motor to breath more air than it can actually suck in. The downside to this is that is only works at a narrow RPM band and not across the whole RPM. But, tune it to co inside with the RPM where max RPM is generated or to extend your RPM range and the bike will accelerate quicker.

I agree with you that these carb mods do not add more power to the top end, but the low down and midrange, especially the torque output, gets a whack more power, since the carb is able to open quicker and larger and supply more air with less engine vacuum to open it.

 

I took a few days to go camping with my family and did this dicussion become interesting.

What I am trying to accomplish is to bridge the gap between bottom torque, horsepower and throttle response.

Freez - On a dyno where you are recording data in one gear from 3000rpm and up, your tuning is correct.

222 - In the world of drag racing, MrHP and you have got the broadest curve and throttle response.

Freez/222 In a race in 5th gear from 5500rpm to 7500rpm Freez would win.

In a race from from dead stop to 55mph 222 will walk Freez.

Both you gentlemen have got your acts together. Just that Freez likes highest hp numbers,
where 222 likes acceleration numbers.

Peak acceleration involves broad torque/hp, and great throttle reponse with taking off and between shifts.
When you drag race, you rev the motor to 7000rpm(stock machine) and drop the clutch.
The motor rpm's will drop with traction, and with an airbox with the lid removed, there is no inertia to maintain airflow velocity, and thus the throttle slide will fall. Quad will wheelie and you loose.
Doesn't anyone remember the pictures of MrHP's first DS drag quad with the real skinny rear tires.
He was using these small tires to keep tire spin up for the first ten feet till carb could regain velocity.

I was not able to test this last weekend. More air does make more power, if your present setup needs more. To have a setup with more air than the motor requires causes turbulence and poor inertia.
A cv carb requires high inertia to have maintain throttle reponse during take off and between shifts.
I think the reason the factory built a small airbox was to maintain inertia and use two inlet tubes with high velocity to maintain this inertia.
I need to do more testing to find out how to increase volume, without hurting inertia.

My original question, in more detail, With the airlid removed, can you leave the inlet tubes on or will the inertia be reduced?

 

Hi Oldmanracing.

On the dyno, the mods I talked about actually boost low and midrange power on the DS. On the dyno the DS did not have the low end grunt at about 2500 RPM to around 4500 RPM a raptor pushed out. After the carb mods, the DS low and mid range power is now similar to the raptors. The top end power has not changed much with my mods.

The torque curve is not nearly flat, after the mods.

Oldmanracing, you have combined a few things, which might have helped the top end you are talking about.

I did some dyno runs with the lid on and off. Power wise there was not a major difference, BUT, the acceleration time on the dyno run showed that without the lid, the time to go thru 4th gear was quicker without the lid. The DS was equipped with bigger intake tubes to the airbox, which is basically the same size as running the hole open.

 

Good Afternoon Freez,

This is going to be short, my computer internet provider is having problems.

I agree with you that with lid off low and mid are awesome.
My son says that he can rev better till he hits rev limiter with the lid on?

I am changing to bias tires for next tests, need more tire spin off line.

I feel there is a few extra horses on top because the emulsion tube is atomizing the fuel better. Better burn.

I am going to install velocity stacks into the inlet holes of the air box. Want to have bottom and top both. As air is moving faster, does the air start to tumble with lid off?
Volume and tumbling maybe causing velocity turbulence. Inertia must be falling off.

Freez or anyone with suggestions, please jump in.