I agree with Freez , u know its real interesting when somene who has actually done a heap of dyno time disputes what others say , for example , i have recently made a statement on this forum about stock carbs and other slight adjustments making as good a power curve as , say other carb options ( I wont mention brands again here )

I got heaps of people bashing my findings .....but the real interesting thing was the huge response in P.M's from people who agreed with my findings , but wern't as dumb as me to print there thoughts/ findings.

Good on ya Freez , its nice to see someone else , with an educated opinion giving the time to explain there findings in the hope that it helps others to make better decisions before purchasing products.

I wish this had been the case before i bought a particular (very expensive) carb and throttle setup.

keep up the good work all those who dare to make public there findings , we are better for it !!

Cheers

 

Well, all i want to know did someone yet try what Freez said?? and see if there was a difference??

 

most people just want to right. and have a hard time admitting when there wrong. I am not talking about anybody in paticular. so dont bash me. I see it everyday where I work. I am a deisel machanic for a large bus company. most guys there have a hard time asking for help and addvise. you have to learn somehow. and why not from somebody that has done what you are trying to do. keep a open mind. I dont totally agree that there is no vacume in the snorkle. I have done countless filter restriction tests. there has allways been some vacume behind the filter. even brand new clean filters. maybe there is something else I dont understand about the quad intake.but, I have learned something here that I did not understand. so, keep the good info comeing. and dont be affended when someone disagrees with what you think.

 

Bushmechanic, I did not say there is not vacuum. The air filter has some restriction and this will result is a small vacuum inside the rubber intake. That vacuum will depend on how restrictive the air cleaner is. Dirty or low flow air filters will cause more of a vacuum inside the tube. The more the air cleaner can flow the less vacuum it will have.

With an open air cleaner, that vacuum will not suck the pipe to deform. To do this you need much more restriction than what an air cleaner will give you. This is where the small intakes to the airbox come into play.

If you have a tuned intake, you can actually cause a positive pressure inside the rubber intake. If you make intake resonators you can actually create lots of pressure inside the intake before the carb.

Just remember that the air flows in pulses, so there will be pressure and vacuum during the intake process.

Now I would like to answer some of the other questions.

The fact that bomb reinforced the intake shows they know that the pipe deforms. Does this mean they made the new pipe to make more power? Maybe?

Think of it this way. The BMW F650 uses the exact same motor. Before 1999 these motors where fed by dual carbs, similar than the raptor setup. The new F650 are fuel injected. That same motor is pushing more HP in the BMW than the motor in the DS.

Why do the DS produce less HP? I believe it's due to propose built in restrictions. The stock exhaust, and intake system is very restrictive. This is done to reduce noise, fuel emissions and maybe even to keep the power down on these big quads. The exact same things are being done to Kawasaki, Honda, Yamaha and Suzuki. In all cases the exact same motors in other applications are making more power than in the quads.

Like I said before, Bomb designed this quad to work well with the stock parts and not with a new exhaust and an open airbox. They do not consider new cams, carbs and bolt on mods when they build these quads. Ever thought they built the airbox restrictive on purpose to keep the top end speed down? Maybe they built it like this to keep water out, and they had limited space to work, hell only they will know. I heard rumours that the stock quads are always built to run less than 80 to 75 miles per hour. Airbox and exhaust restrictions are a good place to keep the motor down on power, yet leave the motor untouched so that there is room for improvement if the owners like to get more out of it.

The lastly. I have dyno proof that the no lid setup gives the DS about 1 second quicker acceleration time thru 3rd and 4th gear. The owner also said his seat in the pants tell him that the quad feels more lively and has better throttle response than running with the lid in place. He is running a yoshi slip-on, dynojet kit and needle, K&N and no lid. The spring was cut and the slider has extra holes drilled into it. This combo works and makes a differance.

I might have an explanation to why some of you might get more power from running the lid on. If you open the lid, more air is available to the motor. To make power from the extra airflow you need to supply the right amount of fuel to keep the mixture right. Now if you are running the wrong needle or the wrong slider setup the mixture can be messed up real bad with the extra airflow. The mixture can go either rich or to lean and this will rob power. This might explain why some of you feel less power. You might have tried different main jets to try and fix it, but without a dyno and an air to fuel ratio meter, you cannot tell for sure if you are doing the right thing to the carb.

The volumetric efficiency of the DS, even after new pipe and airbox mods, are still low. 85% is average for a 4 stroke. That exact same motor in a BMW is making a VE of 92% with STOCK exhaust and intake. With new pipe and better intake that motor is making a VE of nearly 100% in the BMW.

The dynos posted by some people on the DS shows it gains about 5 to 6 HP up from stock. My dyno shows the same gains, so I am not disputing that. If you get the VE closer to 100%, you should be expecting gains of 8 to 10 HP. The BMW motor is doing this, so maybe one has to see if the dual carbs are working better or it might be due to the fuel injection. MAYBE it’s got to do with finding the right intake system. Maybe its time people throw the stock intake out the door and see if they can get a new, better setup, starting from scratch. This is not easy and requires lots of dyno time and hit and miss attempts.

I will do some extensive testing on the dyno to see what happens to the mixture when the lid is on or off. If you have more air and you can get the mixture right, the motor has no other option but to make more power.

 

I have been reading this thread with interest,

I was just thinking if the only worry with running no lid is that the slide will not fully open is there no way of checking that after a run it has fully opened.
using marking blue or somthing ? I have tried the lid on and of but only for short runs around the house so its hard to say if it made a big diferance but I would say i definettly didnt feel a loss of power like i have if the diaphram hasnt sealed correctly. I might go to the beach today and try some timed runs with the lid on and off.

Any way whoever is right or wrong keep up the discussion its all good

 

what else would it take to bring this on line? or would it just make more sense to go with KMS? I would like to see more options for injection. Freeze, have you run a injected ds on the dyno?

 

Ok
I went to the beach and tried lid on and lid off back to back,
result
Inconclusive ?
I think it definetly felt better when cracking the throttle open at low revs , response was better this is where i would have expected the lack of vacum problem to arise if it was going to.
It could be that the lid off suited my jetting better than with it on its probably a bit rich as its running a 180 at the moment.

Full throttle flat out was hard to say as the extra noise of having the lid off may have given the impression of more speed.

any way i would have to say the bike definatly didnt lose any thing during this experiment.
i forgot to bring a stop watch and only had a stock 400 ex to run against so maybe next time if i have somthing better matched to run with it will show up a bit better.

i like the bmw injection idea , would probably need the ECU thingy to make it work

 

Blue ?? you didnt disconnect the vent hose off the intake tube to see if less vacume from the breather helped or not?

 

Blue, glad you noticed the throttle response improvement. Before I forget, make sure you remove the rubber seal around the airbox lid opening. With the seat on and sitting in the right place you can actually close the hole up again. Without the rubber seal you will not have this problem. It just pulls off, and you can put it back whenever you need it.

You can also try installing bigger intake tubes to the airbox, instead of running without the lid. One of the 1st mods the guys do here is to chuck those restrictive black tubes and their rubber fittings in the airbox and fit bigger pipes. They use a clear pipe that has a metal coil in it and fits the hole in the airbox perfectly. The metal coil then acts like a screw and you just turn it and the pipe fits nice and tight. That alone will nearly double your airflow into the airbox.

No, I have not played around with a fuel injection DS yet, but I know some guys that are busy testing this setup. It's the same guys that won the Paris to Dakar race last time on the DS. They have a nice shop and they always tinker with the DS for their racing team. I will try and have a chat to them about their progress.

To be honest, I don't think you will get much more power by running the EFI, maybe I am wrong. If the carbs are producing the right air to fuel mix, then fuel injection is not going to give you much more power. Better throttle response and better torque here and there should be possible, especially at low RPM. The reason why I say that fuel injection is not going to make a massive difference is because of the location of the injectors. Most high performance engines will place the injectors very close to the intake valve opening. This is done to get the best fuel atomization and to prevent fuel fallout of droplets forming on the intake tract. Placing the injectors way before the intake valves might result in a poor atomization and the bends and curves in the intake tract will effect it even further. The stock DS head is not designed to handle fuel injection. It has too many bends and curves in the intake. If you are thinking about fuel injection I would personally try to mount two injectors inside the metal intake that is now between the carb and the head. If you can, you might have to drill some metal out of the head to have the injector as close as possible to the intake valves. Spray fuel directly into the valve opening.

In the late 90's a guy in the UK was helping Yamaha to build a fuel injected, supercharged 660 engines for the Paris to Dakar race. That 660 is the same motor the raptors are running today. When he got the fuel injection online and working correctly, he had to modify the head so that the injectors were mounted directly into the head and spraying fuel directly into the intake ports. Without it, he could not get the performance he wanted.

Imagine a fuel injected, supercharged motor in a quad. Turbos suck my dust.

I added the link of the fuel injected Rotax motor as used by BMW. They also modified the intake tract to get the fuel injection to work better. They made the intake port straight, without bends. This way the fuel injector is also facing the intake port directly. If you are thinking about using the BMW setup on a DS, you need the BMW head and you will have to move the fuel tank to make space for the intake setup they are using.

Fuel injected version used by BMW.

I would also like to know if the dual carb setup would work better than the single carb. The dual carbs from the BMW should just bolt on and might be an easier mod than the EFI. There is lots of talk about dual or single carb setups. The theory is that two smaller carbs will improve fuel atomization and provide much better throttle response. BMW and Yamaha are using this setup instead of the single carb. Some of the Ducati race bikes also used dual carbs per piston. This might be an interesting project for the DS, especially if you can get a hold of the ones used on the BMW.

Rotax motor with Dual carbs as used by BMW.

 

that injected version looks like it would turn in to a modification nightmare. the carb version is interesting. what size are those carbs?