278 replies to this topic

[James]

Well I'm glad this topic has arisen because I have similar issues with my 900.

The surging isn't a big problem, at 30mph/3000rpm/3rd gear it's there but not too intrusive. The snatchy on/off throttle at low revs, particularly over bumps, I do get. Again, mine might not be a bad as others out there because in the short time I've had the bike I've learned to ride around the problem. As I said, it's not that bad or perhaps I'm just insensitive! Knowing that it's not just mine that does it is a comfort.

I'm pretty certain that the CO positions won't have been altered or the air box mod done on this bike. I haven't looked at either yet but everything else on this bike is as it left the factory - suspension settings, etc. I have it in mind to try 'richening' the CO settings and see how it reacts before doing the air box mod, but I'm going to try and get all methodical about it

Edited by Jim, 05 May 2016 - 10:24 pm.

[fixitsan]

Another mod i did, which I haven't heard of anyone else doing, is to disable the exhaust auxiliary air system (I forget what Yamaha calls it on this bike).

 

I observed when the solenoid opened and closed and concluded that at lower revs there were times when that system would interfere with the engine's demand for air. Also, the solenoid opens on overrun and lets air go straight down the exhaust to help the catalyst and to dilute the pollutants....if the solenoid is slow or the valve seat not sealing perfectly then the turbulence in the airbox, i felt, might cause rising and falling pressure pulses when you go back under load.

 

The air for the this air system is taken from the lower left side of the airbox....all I did was remove the pipe which goes to the solenoid and fitted a thick piece of polythene over the moulded pipe exit of the airbox and then refitted the solenoid's air pipe.

 

What i might do this weekend is remove the plastic sheet and see if I notice any difference ....when I first fitted the mod I was also making a few other changes too so it was difficult to say if it was this or that which improved the low speed running.

 

 

 

If you adjust the CO values, i found that when I set both values the same the engine ran worse. I followed everybody's advice and it made things worse so I decided to figure out another way, so i assumed that any increase or decrease should be made with respect to the original factory set value..... I have nothing to prove if this is right or not though

[celticbiker]

Also worth baring in mind is that air flow in the air box causes c2 to run considerably hotter than c1 and this can also be a reason for the disparity in settings

[frits44]

Oké I did read story, bud it make no sense to me why the CO has to be different.

I am not a mechanic and I am trying to learn how to do things with my machine.

Here in my country everybody has there settings on both cylinders the same.

I know that every engine is different in there CO settings.

I always think that These CO settings must be the same for the balance of the two cylinder.

IT is strange that in Holland almost everybody drives with CO settings from by example:

19/19 or 20/20/or 21/21 and with open exhaust CO settings on 25/25.

 

I also know that you must test it on a CO tester to see if it is good.

 

My TDM 900 first CO settings are 14/14 that was from the fabric, know it is 25/25 and it runs very fine 

From very low RPM till high RPM.

 

It is difficult to understand but I am trying.

 

Many thanks for your answer.

 

Greetings,Frits

[fixitsan]

C2 also runs hotter, I've been told, because it's right side isn't open to the air, unlike the outer side of the left cylinder. The cylinders are not aircooled but i guess their may be some mileage in the idea. Therefore it would benefit from being run richer, apparently.

 

I don't see any logic in believing that both must always be the same...not unless you are measuring CO levels with a probe. The fact that there are two adjustments and two cylinders suggests there may be a good reason for allowing you to trim them independently. bu t having said that on some Yamaha 4cyl engines, C1 = cylinder 1 and 4, and C2 =cylinder 2 and 3. the inner cylinders always run hotter and may require different values because of that

Edited by fixitsan, 06 May 2016 - 07:35 am.

[frits44]

Oke, but how do you measure these CO settings in a correct way ???

 

Frits.

[fixitsan]

You need to use a CO measuring device, with a probe in the individual exhaust downpipes.

I actually suspect that you could use a Colortune device, with the engine set to a fast idle....it would get you very close at least.
Or just keep the difference between values and only ever change both by the same amount at the same time.

[fixitsan]

Just thinking about this some more......and I might just be talking out of a hole in my head but the facts are fairly compelling....

 

Exhaust gas temperature, EGT, is directly affected by air fuel ratio, AFR

 

On a normally aspirated petrol engine the lowest EGT tends to come at about a 14.5:1 AFR

 

I suspect that it may be possible to use a high temperature thermometer, either a laser based non-contact device or one using thermocouples, to trim the AFR, using the CO settings, to dip the temperature to it's lowest point, because a 14.5 AFR is not bad

 

At least, it ought to be possible to set both cylinders so that the EGT , and therefore the AFR(using the temperature of the downpipe wall as a proxy) are the same.

 

Just a thought

[frits44]

Thanks for the answer,

 

I will measure my CO like you said, and see if my machine is running good.

 

I also will measure my AFR, because I put a 6K Ohm resistance between my air sensor. ( fool the ECU )

 

So I have to find a company who can do that for me

 

Many thanks for your answer. 

 

Greetings, Frits from holland

[frits44]

How about this,

 

Is it possible that the  top of the air box creates air turbulence and maybe vacuum??

 

When you see the inlet there is a construction for the air flap

.

So we all do the air box mod  by JBX thanks for that, but we do not look at the top of the air box.

 

So this is what I did today, I removed  the hole mid section where the air flap was from the air box

 

And I glued a flat piece of plastic on the top of the air box.

 

Now I have a bigger air inlet and no turbulence in my air box.

 

And I have a better airflow.

 

http://s1175.photobu...html?sort=3&o=0

 

I hope you understand what I mean.

 

Greetings, Frits from holland

[frits44]

I was thinking all the time that it has to do with too lean in the fuel, I mean the jerkiness in low rpm.

 

But, is it possible that the TDM 900 has a too small air inlet in our airbox and a bad airflow and there  for a engine that runs

 

not fine in low rpm???

 

I did the mod today with the top of the air box and I did not a test ride because the glue was not dry. 

 

 

Greetings, Frits from holland

[muddy]

I was thinking all the time that it has to do with too lean in the fuel, I mean the jerkiness in low rpm.

 

But, is it possible that the TDM 900 has a too small air inlet in our airbox and a bad airflow and there  for a engine that runs

 

not fine in low rpm???

 

I did the mod today with the top of the air box and I did not a test ride because the glue was not dry. 

 

 

Greetings, Frits from holland

If you can find cause and  cure you'll be the Carpe Messiah

[celticbiker]

I think you will find turf this will create a lot of noise from the air box.
Induction roar sounds great from the sidelines but when you're sat on top of it,it gets annoying very quickly.
Also remember that the shape of the air box is specifically designed to help the engine breathe correctly,that's why rubber tubes inside the air box are different lengths so they don't interfere with each others air flow.
By changing the shape of the air box you will be changing the air flow inside and could potentially be starving one or both cylinders of air.

Edit.
A modern engine with valve overlap will naturally have a dip in the torque at about a third to a half the red line rpm. If the air box is tuned to have minimum resistance to air flow at this rpm, the dip in the torque curve will be partially filled in by the ease of pulling air into the engine.
So, your air box is most likely designed to add horsepower in the mid-range. The air box will have little or no effect on peak hp.
Years ago, before airboxes were designed as resonant systems, it used to be popular to cut additional holes in the air box to allow more air flow for high rpm. This is no longer a good idea. Modern air boxes can flow much more air than the engine will ever use. Modern engines have throttle bodies or carburetors with throats that are typically about 45mm in diameter, about 16 sq.cm in area. The inlet snorkel to a modern air box will be roughly 300 to 800 sq.cm - much larger than the throttle body or carburetor throat. The idea that the snorkel makes for a significant impediment to air flow into the engine is questionable at best. Drilling holes to let in more air is exactly equivalent to drilling holes in your speaker cabinets to let out more sound. Removing the snorkel from your air box is the exact same thing as removing the port in your speakers, the tube that's carefully engineered to have just the right diameter and length to reinforce the bass on your speakers at low frequencies. By altering your air box in any significant fashion, you're most likely going to cost yourself three to five hp in the mid range, and gain nothing measurable at high rpms.

Source
http://www.calsci.co...o/Airboxes.html

Edited by celticbiker, 08 May 2016 - 05:58 pm.

[frits44]

Oke , but I am talking about the top of the air box  not the part below where the tubes are.

 

Just look at the inlet and you know what I mean.

 

Greetings, Frits

If I may say so the air box has not a good desigh 

 

If you look at the inlet you do not have a great airflow

 

There for I changed it

 

Greetings , Frits

[celticbiker]

Above post edited for clarity.
I fully understand what you mean, I have been tuning and racing bikes since I was six years old.

[frits44]

Did you see the picture I made ??

Me to tuning two strike engines and turbo diesels

 

Just think about it thats al I ask

 

Greetings Frits

[frits44]

The inlet is now one opening before that there were two channels for the air inlet

[Andy25]

How soon can you test the modified air box Fritz ? ( More out of curiosity than anything else as I'm riding an 850 )

Andy

[JBX]

Another mod i did, which I haven't heard of anyone else doing, is to disable the exhaust auxiliary air system (I forget what Yamaha calls it on this bike).

 

I observed when the solenoid opened and closed and concluded that at lower revs there were times when that system would interfere with the engine's demand for air. Also, the solenoid opens on overrun and lets air go straight down the exhaust to help the catalyst and to dilute the pollutants....if the solenoid is slow or the valve seat not sealing perfectly then the turbulence in the airbox, i felt, might cause rising and falling pressure pulses when you go back under load.

 

The air for the this air system is taken from the lower left side of the airbox....all I did was remove the pipe which goes to the solenoid and fitted a thick piece of polythene over the moulded pipe exit of the airbox and then refitted the solenoid's air pipe.

 

What i might do this weekend is remove the plastic sheet and see if I notice any difference ....when I first fitted the mod I was also making a few other changes too so it was difficult to say if it was this or that which improved the low speed running.

 

 

 

If you adjust the CO values, i found that when I set both values the same the engine ran worse. I followed everybody's advice and it made things worse so I decided to figure out another way, so i assumed that any increase or decrease should be made with respect to the original factory set value..... I have nothing to prove if this is right or not though

 

This is called the AIS.

This is an exhaust anti-pollution system which works only when the engine is idling or until the coolant temperature is below the standard working temperature.

It does not interfere with the engine max power or torque, removing it is not really useful.

Many R1/R6 riders remove it under the false belief it will increase max power. it actually only allow some weight gain.

Edited by JBX, 08 May 2016 - 10:48 pm.

[JBX]

I think you will find turf this will create a lot of noise from the air box.
Induction roar sounds great from the sidelines but when you're sat on top of it,it gets annoying very quickly.
Also remember that the shape of the air box is specifically designed to help the engine breathe correctly,that's why rubber tubes inside the air box are different lengths so they don't interfere with each others air flow.
By changing the shape of the air box you will be changing the air flow inside and could potentially be starving one or both cylinders of air.

Edit.
A modern engine with valve overlap will naturally have a dip in the torque at about a third to a half the red line rpm. If the air box is tuned to have minimum resistance to air flow at this rpm, the dip in the torque curve will be partially filled in by the ease of pulling air into the engine.
So, your air box is most likely designed to add horsepower in the mid-range. The air box will have little or no effect on peak hp.
Years ago, before airboxes were designed as resonant systems, it used to be popular to cut additional holes in the air box to allow more air flow for high rpm. This is no longer a good idea. Modern air boxes can flow much more air than the engine will ever use. Modern engines have throttle bodies or carburetors with throats that are typically about 45mm in diameter, about 16 sq.cm in area. The inlet snorkel to a modern air box will be roughly 300 to 800 sq.cm - much larger than the throttle body or carburetor throat. The idea that the snorkel makes for a significant impediment to air flow into the engine is questionable at best. Drilling holes to let in more air is exactly equivalent to drilling holes in your speaker cabinets to let out more sound. Removing the snorkel from your air box is the exact same thing as removing the port in your speakers, the tube that's carefully engineered to have just the right diameter and length to reinforce the bass on your speakers at low frequencies. By altering your air box in any significant fashion, you're most likely going to cost yourself three to five hp in the mid range, and gain nothing measurable at high rpms.

Source
http://www.calsci.co...o/Airboxes.html

 

The shape of the air box after the air filter is one thing, the design of the cover of the air box - before the air filter is another thing.

The (rather funny) source site makes the confusion between the two things, it just forget what is an air filter : it act as a resistor inside the whole air box and this damps any resonant system inside the whole air box.

While there is actually a resonant system in modern air boxes, it is only the part that is after the filter.

This part should therefore stay unmodified.

 

Btw I had some work on the air box cover to remove the whole flap actuator mechanism at the same time I disabled the flap, a long long time ago !

The result is a little bit more intake noise but only when fully opening the throttle bodies at low rpm.

And the engine is much more usable at low rpm.