951 RAVE Valve Mod

[acuratech481]

When drilling the RAVE valves on a 951 to make them mechanical and no longer rely on the electric solenoid, does anyone know what to do with the pulse hose from the crank case that goes to the solenoid?

Can the Solenoid be removed and left unplugged? Or will that causes fault codes?

Does the vent hose from the solenoid to the tunnel of the hull get cappped?

Do you cap the pulse hose at the fitting on the engine block?

So far, I've looped the RAVE valves together with a piece of hose.

This is the last piece to my puzzle so any input would be greatly appreciated!

 

[pagoda81]

Did you ever solve this? I pretty much signed up to this site to ask this exact question.

 

[NCGator25]

Although I haven't tried it yet, someone mentioned on the Facebook forums that you don't need to modify the rave valve housings. Instead, take the pulse line and plug it directly into the rave valve t fitting. This accomplishes the same thing as drilling the housings, and uses the engine pressure to drive the rave valves. I plan on giving it a shot next summer.

 

[tobytd]

Plug the line at the crankcase port.
If you connect the line at the T the valves will be open all the time

 

[NCGator25]

Agree, if you've already drilled the rave housings, then you'd want to plug the crankcase port. The option I mentioned above eliminates the need to drill the rave housings.

 

[Grim]

What does that mod really do? Does it provide more reliability? or just take out the switch to simplify the system? Interested in reliability for sure. I saw the drill method and not sure I want to try and drill at an angle...but if you can just reroute hoses for the same effect...might be something to look at. Is the juice worth the squeeze?

 

[NCGator25]

My understanding is that it smoothes out the powerband. The solenoid acts as an on/switch, and so it's noticeable when it activates. The modification eliminates that feeling and creates a smoother transition.

I haven't done it yet, but I plan to give it a try next summer.

 

[NCGator25]

Reliability shouldn't be an issue since some of their other engines operated the raves off the crankcase pressure.

 

[Grim]

My understanding is that it smoothes out the powerband. The solenoid acts as an on/switch, and so it's noticeable when it activates. The modification eliminates that feeling and creates a smoother transition.

I haven't done it yet, but I plan to give it a try next summer.

So to make it work , using the diagram in this thread, you just remove the switch. item number 4, and put a T fitting there?

 

[NCGator25]

You'd remove the tube #3, and plug that tube directly into the T fitting closest to the rave housings. This allows the crankcase to control the raves directly.

 

[tobytd]

EXHAUST pressure opens 787 rave valves, NOT crankcase.

 

[mikidymac]

You only want the RAVE valves open at higher RPM because they change the port timing and exhaust sonic wave to give you more top end. You would not want them open at low rpm because you would loose bottom end.

Do not connect them to a pulse line as the pulse line does just that, pulses so it will not open the RAVE valves, you either need a vacuum or exhaust pressure. Drilling them allows them to open by exhaust pressure like in a 787.

 

[WhiskeyD]

You only want the RAVE valves open at higher RPM because they change the port timing and exhaust sonic wave to give you more top end. You would not want them open at low rpm because you would loose bottom end.

Do not connect them to a pulse line as the pulse line does just that, pulses so it will not open the RAVE valves, you either need a vacuum or exhaust pressure. Drilling them allows them to open by exhaust pressure like in a 787.

Exactly. Connecting RAVES to pulse port is a horrible idea. Some bad advise in this thread.

 

[WhiskeyD]

Reliability shouldn't be an issue since some of their other engines operated the raves off the crankcase pressure.

This is incorrect.

 

[NCGator25]

Please stop giving advise. This is incorrect.

As I mentioned in my first post, this is not my advice, but anothers from one of the Facebook forums.

The port referenced as the pulse above is the port that is directed to the solenoid, not the pulse line that goes to the carbs.

When redirecting that pressure directly to the raves instead of the solenoid, it seems the raves would still only open under higher pressures, the same which happens under the solenoid. At the end of the day, we're simply talking about engine pressure controlling when those ports open.

So my question to you...why wouldn't this work in the same manner as drilling the rave housings?

Why does it matter where the pressure is coming from as long as the pressure is able to open the raves when needed?

Do you have first hand knowledge from trying it, that it doesn't work?

Since you seem to be absolute in your opinion, please share any references you have that indicate it doesn't work! I'm interested in looking at them.

 

[NCGator25]

Here is a screen print from the group discussion. Todd's mentioned it in other posts I've seen as well. I'm not sure how to share the direct link.

 

[tobytd]

Once the basic principles of operation are learned and understood it will become apparent.

 

[WhiskeyD]

How much pressure does the pulse line produce? And wouldn't the pulse cause the RAVE to not fully stay 100% open?

 

[tobytd]

Without the one-way check, I would not expect it to do anything

 

[NCGator25]

Once the basic principles of operation are learned and understood it will become apparent.

Well, that's what this forum is for! Please enlighten us on why Todd's method will not work. I'd like to hear specifics in why you "know" it will not work. Have you tried it on a 951 engine? Are you a mechanical engine? Did you work for Sea Doo in designing the engine?

You seem very sure in your knowledge of why it won't work, so please share the specifics after answering the above questions for us.

Thank you.

 

[NCGator25]

How much pressure does the pulse line produce? And wouldn't the pulse cause the RAVE to not fully stay 100% open?

I see you edited your post above. Why were you so sure it couldn't be done, but know you don't seem to be sure? I'll ask again since you didn't answer my questions before:

So my question to you...why wouldn't this work in the same manner as drilling the rave housings?

Why does it matter where the pressure is coming from as long as the pressure is able to open the raves when needed?

Do you have first hand knowledge from trying it, that it doesn't work?

Since you seem to be absolute in your opinion, please share any references you have that indicate it doesn't work! I'm interested in looking at them.

 

[NCGator25]

I'd also like to hear from both of you as to what harm will happen to the engine if this modification is attempted? Is the engine going to blow up? Will it simply not open the raves? What would go wrong by giving it a shot in your opinion?

You both seem very confident in your responses that it won't work.

In my opinion, if the modification Todd lays out isn't going to hurt the engine, I think it's worth a shot to try. If it does work you've managed to avoid the possibility of screwing up the rave housings by trying to drill them. If it doesn't, so what, you put things back the way they were, and look into drilling the housings. I don't see the downside of giving it a try before you start drilling.

 

[NCGator25]

Without the one-way check, I would not expect it to do anything

He specifically states to leave the check valve in place in his post.

 

[Grim]

So my thought on this is to ask why was the solenoid designed into the system in the first place......if leaving it off would make it function just as good? Only possible thing I can think of, other than it doesn't work (well) that way, is that it helps with emission standards of the time....we all know how the govt can make crap complicated.
Looking at the system, it seems like this mod is very similar to the "drill" mod, unless the pressures(exhaust vs crank case) are different in a way that would make this mod not work. I'm wondering if the solenoid acts like a pressure regulator to help smooth out the rave valve actuation, and without it you may get stuttering...just an idea!

 

[tobytd]

Crankcase pulse is turned into positive pressure by one-way check valve. This positive pressure has the gas and oil mixture in it also. Until the rave valves are activated, this pressure flows thru the solenoid and out the back of the hull, we can’t be dumping fumes in there. When the mpem closes the solenoid, the pressure goes to the rave valve diaphragms, moving the guillotines and effectively changing the port timing. When the solenoid is deactivated, diaphragm pressure is released to atmosphere out the back of the hull.