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MAP Sensor Tubing Caution

gypsy_100

New member
A note of caution here in replacing the rubber vacuum tubing that runs from the MAP sensor to each throttle body. Several have reported the short lengths of tubing getting brittle and cracking causing vacuum leaks and poor running. They have replaced it with either generic vacuum tubing or perhaps the official BRP part. I just had that problem to a minor extent in that I was getting intermittent P0174 codes (#2 cylinder running lean). It was finally diagnosed as a loose connection where one of those rubber tubes fits onto the MAP sensor. The tubing hadn't cracked, it felt flexible and the bike ran fine but threw the code. Must have dried out just enough to not be tight on the fitting.

Now here's the caution. In reading the fine print of the shop manual, I discovered that BRP says these two rubber tubes are of a "calibrated" length and "should not be tampered with". If the length is not as prescribed "the engine may be improperly calibrated". Hmmm... Anyone using generic rubber tubing should be sure they make the lengths exactly the same as what they remove. The manual shows it as 85mm or 3.34" (the manual incorrectly shows the conversion as 4.33"). I measured mine at about 85mm. If I hadn't read that warning in the manual, I might have bought some tubing and just cut it to a convenient length that makes for a nice easy connection.

I mentioned this to Scotty and he had a further question: if the inner diameter were slightly different,would that also cause an error? You could buy tubing that fit well and felt tight but if it were slightly different (say English size versus metric size), would that make a difference?

I don't know if the BRP tubing is a higher quality that holds up better to the high temps in that area. It obviously doesn't last forever (30K miles in my case) but maybe generic vacuum tubing would fail even quicker. No idea.
 
yah

:banghead:rode mine a few blocks and the engine failure screen lit up like a Christmas tree and went off after a few mins. , then engine light stayed on permanently. towed it and later the tech called and told me those hoses were bad and were replaced with NO other problems.
I have the 2012 RT SE5 with only 5600 mi....what gives! really disappointing for my spyder to be in n out this many times for problems.
just saying......:shocked:
 
Sorry but I'm calling BS on the length of the hose having anything to do with performance. Unless the line is so long that it kinks or so short that it doesn't fit on all the way.

The ID of the 2 lines on the RS are different but the OD is the same. So, the wall thickness is MUCH thinner on the one line. I can see the thin wall breaking down much easier.

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Sorry but I'm calling BS on the length of the hose having anything to do with performance. Unless the line is so long that it kinks or so short that it doesn't fit on all the way.

The ID of the 2 lines on the RS are different but the OD is the same. So, the wall thickness is MUCH thinner on the one line. I can see the thin wall breaking down much easier.

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I dunno Drew but it sorta makes some sense. To maintain an accurate vacuum The ID must be a certain size and length. Vacuum is like air a bigger or smaller area will make a slight difference in the BAR pressure and flow. If the volume is calibrated by the hose it will vary. How much difference :dontknow: it may be another quirk with these engine. I am gonna guess the one you mention as smaller ID is longer correct? If so then both will have the same vacuum pressure due to same volumetric area. Think like a car intake using a radiator hose vs. the large one that they use instead. Just thinking out loud here.....
 
I dunno Drew but it sorta makes some sense. To maintain an accurate vacuum The ID must be a certain size and length. Vacuum is like air a bigger or smaller area will make a slight difference in the BAR pressure and flow. If the volume is calibrated by the hose it will vary. How much difference :dontknow: it may be another quirk with these engine. I am gonna guess the one you mention as smaller ID is longer correct? If so then both will have the same vacuum pressure due to same volumetric area. Think like a car intake using a radiator hose vs. the large one that they use instead. Just thinking out loud here.....

Yea, who knows....:dontknow:
The main reason I don't think the length of those lines is critical is that this is the same motor setup that has been used for about 10 years in the Aprilia bikes. Those bikes have the map sensor in the airbox so the lines are different lengths for sure. These motors are not known for being all that finicky.
Also, if you look up the part number for the Bosch map sensor it's used in about 20+ different BRP machines...:shocked:

The RS is a bit different than the RT. We have a line for the map and a line for the fuel pressure regulator. I honestly don't remember which was the thinner one.

I agree that diameter and length can affect vacuum. However, I don't see it happening in a 85mm long piece of tube that is about 4mm diameter. Maybe if that tube were significantly longer or significantly larger in diameter?

A bigger concern would be a tube that is to long/kinked or if a type of tube used is not designed for vacuum and it crushes under vacuum.

I was really surprised how thin the tubing wall was on one of those lines! Easy to kink, crush, crack, collapse. I did swap mine out with thicker wall tubing.
 
If they are using 2 hoses, one to each cylinder then it makes perfect sense. They do the same thing on their outboards with the oil injector. 6 cylinder engine and 6 identical length hoses even though the injector is real close to some cylinders and farther away from others, oil would always go out the shortest hose first so they make all the hoses the same long length. This would work in reverse for vacuum pulled from each throttle body. I don't think it has anything to do with volume in the hoses but "reaction" time since the throttle plates work in sync.
 
tubing length

I had the hose problem last year. 2011 RTs with less than 5000 miles. The hose to the rear cylinder was brittle and had split into two pieces and the bike would not run. Called the closest dealer and the tech suggested that I replace both hoses with good quality vacuum hose. When I tried to remove the second hose it also broke and had to removed the remaining ends on the nipples in pieces. I did not have much to work with on length. Spoke to the tech again and he said just cut the tubing to a length that allows the tubing ends to reach both connections without stretching. I really did not know the correct length. Replaced them and the :spyder2: started right up and ran fine. Just had the 9000 mile service and the dealer checked the hoses and said that they were nice and flexible. Perhaps I just got lucky and arrived at an acceptable length by accident. Not sure why the original hoses failed but the replacements are still in place and the :spyder2:functioning well.
 
Tubing length not so critical

Sorry but I'm calling BS on the length of the hose having anything to do with performance. Unless the line is so long that it kinks or so short that it doesn't fit on all the way.

When we had the "Cracked Vacuum Hose Problem" at one point I had a 12" length of hose on one port and the OEM piece on the other port. Ran fine. I eventually replaced them both with the BRP hoses but we carry a spare set made from auto vacuum hose cut to 4".

Much discussion on this here...
http://www.spyderlovers.com/forums/...-after-Storage&p=598270&viewfull=1#post598270

There are other threads on cracked vacuum hoses and their effects.
 
Ford Tempo used to have a silican hose running to the evp sensor, it was of very good quality exhaust gasses didn't bother it.Still have a couple in my tool box will have to see if they will fit
 
Ford Tempo used to have a ☆silican hose☆ running to the evp sensor, it was of very good quality exhaust gasses didn't bother it.Still have a couple in my tool box will have to see if they will fit

That's the ticket.
 
A theory

Noone posted this thought, so I will. The "early" failure of the tubes is due to the excessive heat under the bodywork. If correct, there will be other problems waiting to be discovered.

Jerry
 
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