Riva throttle body spacer.

[Williamsone46]

Here at high altitude I wasn't getting the rpm everyone had been getting at lower elevations. So I installed these Riva throttle body spacers to gain as much rpm as I could, allowing me to re pitch my impellers as little as possible. I gained 200 rpm for about $80.

 

[Bruce]

Thanks for sharing. Did you remove any factory parts?

 

[Williamsone46]

The second and third picture show the spark arrester that was removed.

 

[johnk]

HI William,

Did you notice any other gains like smother throttle response snappier bottom end etc.....

I noticed huge gains on my supercharged waverrunner model with this mod and was thinking of installing on both naturally aspirated motors in my AR240.

 

[biglar155]

The second and third picture show the spark arrester that was removed.

Is that legal? I thought there was a requirement to have a spark arrester on inboard boat engines. Maybe I'm thinking of something else...

 

[bucks448]

The air filter should/needs to be replaced with one that has a flame arrestor. The removal of the flame arrestor will never be found unless (probably) an insurance claim is being made for fire damage.

 

[Williamsone46]

Is that legal? I thought there was a requirement to have a spark arrester on inboard boat engines. Maybe I'm thinking of something else...

You can install an aftermarket air filter that also acts as a flame arrestor to comply with state/fed law.

 

[Julian]

What do the spacers do vs just removing the spark arrestors?

 

[Ronnie]

I think that they smooth out the air flow by taking up the space that the outer ring of the flame arrestor normally does.

 

[Ronnie]

I think that they smooth out the air flow by taking up the space that the outer ring of the flame arrestor normally does. Here is a pic of the R&D version that Island Racing sells ($50 each). FYI Another member said that the edges on this are very sharp.

 

[Nick Hughes]

Sorry to bring up an old thread, but is the correct model number for the 2015 242, mwv-rimuk-vx-11? The yamaha website seems to want these to be for the waverunners. And its the same model for the California emissions engine?

 

[Ronnie]

I am not certain but I believe that All normally aspirated 1.8 liter Yamaha marine engines use the Same intake modification / part number. I recall that someone here discovered that the supercharged engines use a different part number because the size is differentt/bigger for the supercharged engines.

 

[swatski]

I am not certain but I believe that All normally aspirated 1.8 liter Yamaha marine engines use the Same intake modification / part number. I recall that someone here discovered that the supercharged engines use a different part number because the size is differentt/bigger for the supercharged engines.

No they are not. 1.8l 2015 intake manifold is different than 2016, with different ribbon diameter.

@Nick Hughes I would check the part numbers (throttle assembly, ribbon) of the exact boat model number in one of the microfiche suppliers.

I don't think there is a difference for CARB models, but you will find that in parts, too.

 

[swatski]

For example, for 2015 242 Limited S:

http://www.powersedge.com/oemparts/a/yam/54453cb7f870020ad8f5dad8/intake-1

 

[Ronnie]

@swatski , The CA and non-CA powered boats use ribbons with different part numbers. The part number for the ribbon in a 2010 through 2012 242 ls are the same and start with 6bh. In 2013 Yamaha introduced the CA (aka CARB) models to the 242 line. From 2013 through 2016, the CA 242 LS boats use the ribbon with the part number that starts 6bh, whereas the non- CA 242 LS boats (I.e., the non-carb models) use a ribbon with the part number that starts with 6d3. It is not clear how the two parts differ but there is a considerable difference in price between the parts with the 6bh at $59.32 and the 6d3 at nearly $42.95, who new these ribbons cost so much? This distinction holds true for the 2016 190s, interestingly their is no CA version of the 192 listed on the power edge site so the sx 192 and ar 192 use the ribbon with the part that starts 6d3.

@Nick Hughes , here is a url to riva's page containing both intake upgrades available from them. The one with the part number ending 12055 is the one I ordered and it is a perfect replacement for my stock ribbons with the part number starting 6bh.

http://rivaracing.com/search.html#!sq=Intake manifold upgrade

As previously stated by others above, by removing the stock ribbons you are removing the flame arrestors, to replace this functionality riva and r&d and probably other companies offer metal mesh, cleanable/reusable air filters that double as flame arrestors. At least that is what was printed on the packaging of the r&d air filters I got for my 2010 LS, this was printed directly onto the r&d air filters I got for my 2006 sx 230. Whether or not you need a flame arrestor on the water is debatable but it is a legal requirement in most if not all states.

 

[swatski]

No they are not. 1.8l 2015 intake manifold is different than 2016, with different ribbon diameter.

@Nick Hughes I would check the part numbers (throttle assembly, ribbon) of the exact boat model number in one of the microfiche suppliers.

I don't think there is a difference for CARB models, but you will find that in parts, too.

@Ronnie I'm glad you took my advice and looked up the parts numbers for specific models using suppliers microfiche.
Thank you for doing your research!

 

[Ronnie]

@swatski , no thanks necessary, I only did it so it to avoid giving Nick bad advice. The intake manifolds may be different between the 2015 and 2016 models but the ribbons are the same in the CA to CA and non-ca to non-ca boats, which upgrade to purchase requires a determination as to which boat the upgrade is for.

 

[Greg M]

the reason these work vs stock is because they allow less restrictive air flow due to turbulence (laminar flow basics). When air/liquid pass through a tube they behave the same way. Any place they touch creates friction and turbulence. The backfire screen installed in the throttle body, that means air has to flow around the metal used to make it, that means drag, turbulence, and a smaller overall opening. Add all of the metal facing up, and say you have a 40mm throttle body opening, when in reality you only have 34mm because of the metal veins taking up space inside that 40mm and on top of this the turbulence from all those metal edges and more importantly the sides of said veins!

The sad part, the inner and outer shape of the spacers from riva have literally zero to do with the gains made. Go to a machine shop and make your own out of aluminium for a fraction, unless youre in salt water you dont even need to coat it. Have it turned down so the inner diameter is identical to the throttle body inner diameter and the outer lets it fit in the space the arrestor was sitting in. Flat out removal of the stock arrestor and not putting anything in will give you some gain but then you kill the flow (turbulence again and it matters!) when the lip the arrestor was sitting on (see his third pic back of the new riva insert) comes into play and kills the laminar flow.

Also note, you should see some fuel efficiency gains from this as well. Not drastic ones, very very small ones but they will be there. (talking .01 of a gallon but over time, adds up)

 

[swatski]

Flat out removal of the stock arrestor and not putting anything in will give you some gain but then you kill the flow (turbulence again and it matters!) when the lip the arrestor was sitting in (see his third pic) comes into play and kills the laminar flow.

@Greg M There is a (very) strong consensus on the benefits of removing the ribbon (in 1.8l engines), but I am not so sure there is a consensus on any benefits of replacing it with the RIVA ring. Some put it in, some don't. I don't think there is data out there showing additional benefits of inserting the ring, on top of removing the ribbon. Please correct me if I'm wrong.
Of course you are right, in theory, about the air flow. However, when it comes to these engines and pumps, things that make theoretical sense rarely work in practice.

It is all a game of figuring out what the limiting factors are.

--

 

[Greg M]

@Greg M There is a (very) strong consensus on the benefits of removing the ribbon (in 1.8l engines), but I am not so sure there is a consensus on any benefits of replacing it with the RIVA ring. Some put it in, some don't. I don't think there is data out there showing additional benefits of inserting the ring, on top of removing the ribbon. Please correct me if I'm wrong.
Of course you are right, in theory, about the air flow. However, when it comes to these engines and pumps, things that make theoretical sense rarely work in practice.

It is all a game of figuring out what the limiting factors are.

--

Unless I have this all wrong, and PLEASE let me know if i do, and Im basing this on Williansone46 pics, the ribbons are made into or attached to the throttle body insert? (item 17 on the exploded view). If you can just take out the ribbon, youre golden and know it for a fact. If you have to remove the insert itself to get the ribbons out (they are attached in a way that you cant remove them without removing the entire insert) you have to put something in that void so your airflow laminar matches the throttle body, otherwise the lip the insert is riding on will ruin anything you gained by removing the insert.

And Im not endorsing Riva. Even said its shape had nothing to do with it. (BUT when i raced jetskis they are damn good!) I even state that if you have to remove the insert, here is how to make one ;D

Also, when air/liquid flow are talked about, often what the pencil says you see in the real world. Not trying to argue you, but honestly, you do have it backwards. What you DO often see is misapplication or not taking the system as a whole into account so the science gets discredited when in actuality what you changed (streamlined) did work but the bottle neck was elsewhere and on boats, the main bottleneck is the exhaust.

The exhaust on our boats, or any mass manufactured engine, is so restrictive, optimizing it can give you HUGE benefits to both power and fuel consumption. But federal regs, say that certain things have to happen in exhaust systems for a clean burn.

The best part of this, and its the reason the pencil/theory gets dismissed, you have to look at the air flow from the engine compartment until it exits the boat. You can help one area but it doesnt "feel" like it because 2 other areas are a bigger bottleneck.

(sorry Swatski, at lunch and bored to tears! lol)