Air tubes from a GS on an RS?

[Aroundthebend]

New guy here, my first post.

I have a 95 RS and I read somewhere that changing the air intakes to the GS, longer tubes, made for a more tractable ride. There's supposed to be more usable torque, but less top end. Anybody care to comment on this? Thanks

[John Dickens]

It's not that the GS tubes are longer. They are smaller in diameter.

This speeds up the airflow at low revs at the expense of a little less total airflow at high revs.

You get a little more tractability at the expense of a little less power at high revs.

[Joe Frickin' Friday]

It's not that the GS tubes are longer. They are smaller in diameter.

This speeds up the airflow at low revs at the expense of a little less total airflow at high revs.

You get a little more tractability at the expense of a little less power at high revs.

 

The dynamics of air movement during an intake event are somewhat more complex than this. The length and diameter of the tubes interact with the total volume of the combustion chamber to create a Helmholz resonator. The effect is similar to that of a port in a subwoofer, which port's length/diameter are chosen to tune the resonant frequency of the sub's enclosure.

 

Likewise, the length and diameter of the intake runner are chosen to produce maximum air intake at a given RPM, at which the timing of pressure pulses/waves moving through the intake tract arrives a smidgen before the intake valve closes, cramming in that last extra bit of mixture.

 

For a fixed intake runner geometry, variable valve timing is a common way to extend the RPM range over which this effect is beneficial: at higher RPM, the intake valves close later, allowing more time for that pressure pulse to arrive at the valve. However, on high-end supercars such as the Ferrari Enzo, the intake tubes feed each cylinder from an airbox, and actually telescope in/out of the airbox on computer-controlled glides: as the RPM increases, the intake tubes shorten so that the engine breathes its absolute best over an unusually wide RPM range, producing a very flat/smooth torque curve.

 

After all that...yes, the GS tubes will produce the described effect on the RS motor. This mod has been dyno tested, and many owners (myself included) report an unmistakable change in engine performance: more mid-range torque, no holes in the torque curve, at the expense of high-RPM torque (where you hardly spend time).

[John Dickens]

I knew all that. I was just pretending honest.

[tom collins]

i did it on my 97 and it made the bike feel totally different in a good way. my only gripe was that the idle was a little rougher afterward, but i might have been able to tune that out had i taken the effort. as a bonus, it also dealt the death blow to a tiny bit of residual surge i still had at that time. for $35, you just can't beat it and you can change back if you don't like it.

 

tom collins

[rdfarr]

I put the GS tubes on my RS. Couldn't really feel any difference but I'll accept that I had more midrange torque. The tubes sounded different on acceleration, sort of like a car when you take off the air cleaner, and exactly like a GS.

[Wolfy]

I put the GS tubes on my 02 R1150RT. What a change! It was so easy to do. Totally eliminated the torque hole at ~3200 rpm. Well worth the cost. And the cool unexpected thing was an slightly louder throaty noise from the airbox. Now I do not get razed as much that no-one can hear me coming. 8-)

[DEF]

It's not that the GS tubes are longer. They are smaller in diameter.

This speeds up the airflow at low revs at the expense of a little less total airflow at high revs.

You get a little more tractability at the expense of a little less power at high revs.

 

The dynamics of air movement during an intake event are somewhat more complex than this. The length and diameter of the tubes interact with the total volume of the combustion chamber to create a Helmholz resonator. The effect is similar to that of a port in a subwoofer, which port's length/diameter are chosen to tune the resonant frequency of the sub's enclosure.

 

 

I guess this means my GS is a baritone and you other guys are riding sopranos....

[malcpowe]

I have just fitted GS intake tubes to my 1150 RT and I must say it has made quite a difference. The main area I have noticed an increase in torque is between 3000 and 4000 rpm. 3500rpm in sixth gear equates to 70 mph which over here in the UK is our motorway cruising speed. With the standard tubes roll on at this speed was ok but now it is much more instant. I also find I can use a higher gear than previously. eg using fifth instead of fourth on some twisty baack roads.

 

Best wishes, Malcolm.

[charlie b]

Did this to my RT-P a couple of years ago, very cost effective and worthwhile mod. As has been stated, noticeably improved mid range torque around 3-4000 revs, which is where you need it, makes the bike much more squirtable in city traffic and better roll on when on the open road.

A 'can't lose' mod!!!

As a bonus, a slightly throatier sound from the airbox when throttled from low revs, makes the ride more fun!!

Regards

Charlie

[Al Navecky Jr]

As anyone that put on GS tubes had any lean problems? I seen some posts of lean problem after the GS tubes where installed

[Jim Moore]

As anyone that put on GS tubes had any lean problems? I seen some posts of lean problem after the GS tubes where installed

I did. I had terrible pinging after I put the GS tubes on my RT. Of course, that was in 110 degree Yuma, AZ weather.

[Bart Anderson]

FWIW, I just put the stock tubes back on my RT after running the GS tubes for three years. Yes, the GS tubes do seem to make the bike pull harder at lower RPMs, but on my bike there were two things that bugged me:

 

1) It seemed like there was a dip or suckout in the power curve at about 4200 RPM, then the power came back on at 44-4500. Not terrible, but mildly annoying especially when rolling on from that range.

 

2) The bike really seemed to be running out of breath at about 6000-6500 RPM. Roll-on from that point was not impressive. Impossible to get to the rev limiter in 5th gear - it'd get to about 7000 RPM and that'd be about it.

 

Did a 580 mile day yesterday with the stockers. Seems to pull less hard but more consistenly all the way to redline now...I like it. I guess what changed more than anything is my riding style; for the first fews years of ownership I babied the bike, or at least thought I was babying it, which is probably why it didn't really break in 'til about 30k. Then, based in part on advice on this board, I started riding it like many say here it was meant to be ridden. Now, I like to rev the sucker up - and the engine doesn't seem to mind.

 

Haven't had the opportunity to try to find the rev limiter in 5th gear yet, but hope to by the end of the season.

 

Bottom line: do the mod and see if you like it. Then try un-doing it after a while. I liked it when I did it, and I'm liking it now that I un-did it. It's a cheap, easy way to modify the character of the bike.

[FrankT]

I changed the air intake tubes to the GS parts immediately after my bike was out of warranty, along with doing the canisterectomy. Your 95RS is probably similar to my 97RT regarding a flat spot in the torque curve around 4K rpm. The GS tubes eliminated the flat spot and smoothed out the torque curve in the mid range. I don't dispute the torque loss on the high end but I don't ride there so it's not an issue for me. One thing though, I retained the stock cat code plug after reading reports here of pinging problems by switching to the GS plug.

[stubble!]

Can anyone comment on this mod's applicability vs. an R1150RS? I've only got one intake tube, and it's a long one.

 

I've got no problems with the torque curve to be honest, it seems to pull nicely and evenly all the way to the limiter, but I'm curious what the difference is say between Wolfie's RT and my RS of the same year.