Word of caution on doing the 1.8L "ribbon delete"

[jethrof16]

OK, so I finally got around to doing the ribbon delete that the mechanic at my Yamaha dealer recommended doing. From his opinion and my own research it sounds like everyone is getting 300-400 more RPM from this mod and about another 100 RPM by swapping out the factory filter for the Riva Racing K&N filter. This nets (supposedly) about a 3 MPH increase. I'll let ya know after my own water test.

This issue is that the bolts the hold the intake space to the intake manifold (made of plastic) are threaded into inserts in the plastic manifold. These bolts were also installed with thread locker. So...be VERY slow and careful when you go to take these four bolts out. I started out slow and careful but as I was getting toward the finish on the 2nd engine I had my technique down and was moving faster. The extra torque of quickly removing the last bolt cause the brass insert to come loose and start to spin (yea..oh $hit is right). So after several hours of trying a couple techniques to stabilize that insert I gave up and cut the hex head off the bolt and drilled out the bolt from inside the insert. Upon, reinstallation of the spacer I used a through bolt with lock washer and nut on the back side to make sure it was stabilized and securely tightened. I spent about 8 hours all told and about $20 to correct Yamaha's poor design and my overzealous wrenching.

I have attached photos showing the before and after shots and the removed "ribbon".

 

[biffdotorg]

I'm anxious to hear your results. I hope you had some good baseline performance numbers prior as well. Good luck! Nice write up!

 

[jethrof16]

I'm anxious to hear your results. I hope you had some good baseline performance numbers prior as well. Good luck! Nice write up!

I'll move this over to a new thread but the boat loves not having that "ribbon" (flame arrestor) in the mouth of the intake manifold. It is important to note that the factory paper style filter needs to be changed to prevent a possible (but probably highly unlikely) filter box fire. I did get the 3-400 RPM increase on the top side but due to the fact that I had a completely loaded boat (12 people and all the coolers, boards, stuff etc) I can't give you a potential top speed increase. I've never run the boat flat out with this kind of load but I did yesterday in windy conditions and choppy water. I saw 44 MPH on the top side in less than ideal conditions.

That said, wow, the throttle response is definitely much improved. I did not expect this but instantly noticed how much better the engines responded from idle to get the boat on plane. In my opinion, this is the best reason to do this mod. It's clear that the engines are getting more air sooner and the ECU is compensating for this with more fuel...end result...more usable power on the bottom end.

Riva racing also makes an aluminum intake ring the goes in place of the ribbon so there is not lip for the air to go around which would create some turbulence in the intake manifold which is not desired. I elected to not spend the $80 because they didn't have any information on what this sleeve would do verses just removing the ribbon. I don't think it would be very much but we would need dyne numbers to know for sure.

When I have a light load and light boat I will get back with top end MPH.