Possible high altitude performance tweak

[djsquid]

I have read quite a bit around this forum and the other forum about the dramatic affect that high altitude has on Yamaha jet boat performance. And I have noticed it in my 2014 212x. Many of you talk about 55-57 mph (gps) top speed. I have measured mine with similar load conditions at altitudes from 3600 ft (Lake Powell) to 6900 ft (Flaming Gorge) and 4 other lakes in between (Utah Lake, Deer Creek Reservoir, Jordanelle Reservoir, Bear Lake). My top speed at WOT is directly affected: 45 mph at Lake Powell to 38 mph at Flaming Gorge and relative top speeds at the altitudes in between.

So, my question to you is based on a trick we do with our ATVs when we are going to ride really high altitude, we have them jetted for 5500 ft, but they still run like crap at 12,000 ft (top of Paiute Trail) so we have drilled a few 1 inch holes in the top of the air filter boxes and put rubber plugs in the holes, and then we unstop a few holes as we go up in elevation which makes more air available to the engine, and then we plug them back up as we come down. And it really works to help with performance.

So I was thinking that if I were to unclip the air cleaner boxes all the way around in my 212x and put in a few 1 inch rubber spacers to keep the two clam-shell halves apart and a few pieces of duct tape to keep it all together it would provide quite a bit more air flow to the engine and I may be able to experience the "raped ape" performance that some of you have talked about.

Any thoughts on that before I go ahead and do something dumb and screw something up?

Thanks much,
Dave

 

[dan144k]

You could remove the air box cover and filter and do a test run. Do both runs on the same day stock vs open air box and you may have your answer. The boats are fuel injected so their is no jetting to adjust, the computer should sense the extra airflow and compensate automatically.

 

[Speedling]

With high altitude any extra air can help.
I don't know how the 1.8's are designed but they have a more tubular intake right? If that is the case, the tube can actually help increase the velocity of air so anything you do be sure it's before the filter. And then pull the filter. And do the ribbon delete.

 

[Speedling]

For those with mr1 engines, a few notes for ya:
Removal of filter and flame arrestor will gain you a bit of speed or power but very little.
The mr1 being based off a 998cc engine that goes to 14,000 rpm actually means it is set up for more airflow than the engine can handle .
Mr1 ho is 1052 cc and 10200 rpm. At this rpm we still have intake runners that are too large!
Don't think forced air either as the ecu is fickle and hard to work with.
Altitude is best countered with boost. A modded scarab "should" handle it better.

 

[utahrd]

I have read quite a bit around this forum and the other forum about the dramatic affect that high altitude has on Yamaha jet boat performance. And I have noticed it in my 2014 212x. Many of you talk about 55-57 mph (gps) top speed. I have measured mine with similar load conditions at altitudes from 3600 ft (Lake Powell) to 6900 ft (Flaming Gorge) and 4 other lakes in between (Utah Lake, Deer Creek Reservoir, Jordanelle Reservoir, Bear Lake). My top speed at WOT is directly affected: 45 mph at Lake Powell to 38 mph at Flaming Gorge and relative top speeds at the altitudes in between.

So, my question to you is based on a trick we do with our ATVs when we are going to ride really high altitude, we have them jetted for 5500 ft, but they still run like crap at 12,000 ft (top of Paiute Trail) so we have drilled a few 1 inch holes in the top of the air filter boxes and put rubber plugs in the holes, and then we unstop a few holes as we go up in elevation which makes more air available to the engine, and then we plug them back up as we come down. And it really works to help with performance.

So I was thinking that if I were to unclip the air cleaner boxes all the way around in my 212x and put in a few 1 inch rubber spacers to keep the two clam-shell halves apart and a few pieces of duct tape to keep it all together it would provide quite a bit more air flow to the engine and I may be able to experience the "raped ape" performance that some of you have talked about.

Any thoughts on that before I go ahead and do something dumb and screw something up?

Thanks much,
Dave

As another altitude Utah Boater, I am looking forward to hearing some test results.... I have a feeling that undoing the bimini will do more than venting the airfilter, but then again, its time to experiment!

 

[djsquid]

Thanks to everyone for your comments.

Well tomorrow is Saturday, and the weather is beautiful here in Utah. I will see if I can head out to one of the local lakes and test out my theory. I posted this question just to make sure that I wasn't going to break some delicate computer setting by running with the extra venting.

I will let you know how it goes.

-Dave

 

[djsquid]

Well it was too windy Saturday to go try it out, sorry. Hopefully I can get out this coming weekend and test it out.

 

[Williamsone46]

My 212X would go 53mph @ lake Powell and 51 @ Utah lake w/ riva spacers and different impellers w/ more over lap pitched for altitude. You could even go one step further and do high flow air filter & crank case breather. I bet you could get 400rpm prior to getting re pitched impellers.

 

[djsquid]

@Williamsone46 thanks for that help. Is this the crankcase breather you mentioned that will fit my engines?
Engine Breather Upgrade Kit by RIVA®
mwv-ry190-40-14

 

[Ronnie]

I assume the power plenum on the following website is what you mean by high flow air filter (right?)

http://www.islandracing.net/240242.html

Crank case breather?
What's that?

 

[Speedling]

The idea behind a crankcase breather is to let the hot gasses inside the engine escape without going back into the engine, thus letting cooler air enter the engine and make more power.
As the pistons go up and down, they also need some air movement inside the engine.
I would recommend that this is especially unwanted on a boat.
First, it would just vent any fumes associated with your oil churning around and such directly into your engine bay which could be hazardous. Please please if you do this mod be the type of person that runs the blower for a few minutes before you do anything!
Second, the typical fuel injected system uses the vacuum in the intake system to suck these fumes and gases into the intake, where they are combusted safely before exiting the vehicle as simple burnt exhaust fumes. This is usually where the PCV is on cars, allowing the fumes to go out, but not allowing anything to go into the engine.

I did this on my Mustang back in the day but that was because I had a 60mm turbo on it and was scared of any back pressure in the engine to just simply get out of there and escape. That was on road, on a moving car, for short times only. NOT on a boat where we seal off the engine hatches best we can for sound deadening.

Just my 2 cents.

 

[djsquid]

@Speedling Good advice. Everything is a trade off in performance mods. The Yamaha (by Riva) Engine Breather upgrade kit disconnects the tube from the intake and caps that hole. And the kit adds a new engine breather tube with a filter of some sort on the end of it. Before I would buy the kits and do that engine breather mod I think I would go ahead and test it by disconnecting the stock tube and capping the intake hole and then put a temporary make-shift filter on the end of the factory breather hose. After testing for real, measurable hole-shot, mid-range power, and WOT RPM benefit I could then weigh out that benefit against the danger and added care necessary to mitigate vented gasses into the engine compartment.

-Dave

 

[RForester]

Kudos to the discussion. I boat at lake conchas, New Mexico and have the same 2014 212x. I have the same issue with speed, I can only run about 45. Top up ur down. I have only been to a lower elevation lake once and was in hopes of higher speeds, but it was way too rough and windy to open it up. Anxious to hear your results! Robert

 

[RForester]

I could not get the island racing site to work. Is this what you guys are talking about?
http://www.4-tecperformance.com/index.php?main_page=product_info&cPath=16_82_114&products_id=1953

 

[sysinu]

Tomorrow is supposed to be nice, and Monday even nicer. You going to make it out to test? I'm trying to talk the wife into spending a break-in trip to Utah Lake tomorrow (to test perfect pass that I just installed today).

 

[djsquid]

@RForester yes, that is the kit. But definitely do the Riva throttle spacer first. I just ordered two of these today from my local dealer.
https://www.yamahapartsandaccessori.../intake-manifold-upgrade-kit-by-riva?b=Search

This is the one for our boat: MWV-RIMUK-FZ-11

 

[djsquid]

@sysinu We went to Utah Lake (4500 ft) this afternoon (Sat) weather was nice, water calm. So we wake surfed for a while, water is 57 degrees, pretty cold. I did test one part of my theory. My top RPM at WOT is 7000 with 3 people and two surf boards in the rack, bimini not used, full tank of gas. Cracking open the air filter boxes an inch did give me about 80-90 RPM more. So the air cleaner box is restrictive. My plan was also to remove the air filter completely and try that but the wind came up and it got too choppy to make a valid test.

But I did order the Riva spacers today so I will be installing those this week. I may order the R&D plenum that replaces the filter and cleaner box: 200-01805 if I don't get what I want from the Riva spacers.
http://www.rd-performance.com/newProducts/popup.asp?partno=200-01805

We will see.

 

[sysinu]

@sysinu We went to Utah Lake (4500 ft) this afternoon (Sat) weather was nice, water calm. So we wake surfed for a while, water is 57 degrees, pretty cold. I did test one part of my theory. My top RPM at WOT is 7000 with 3 people and two surf boards in the rack, bimini not used, full tank of gas. Cracking open the air filter boxes an inch did give me about 80-90 RPM more. So the air cleaner box is restrictive. My plan was also to remove the air filter completely and try that but the wind came up and it got too choppy to make a valid test.

But I did order the Riva spacers today so I will be installing those this week. I may order the R&D plenum that replaces the filter and cleaner box: 200-01805 if I don't get what I want from the Riva spacers.
http://www.rd-performance.com/newProducts/popup.asp?partno=200-01805

We will see.

Awesome! I think the 212X has much higher probability in that 55MPH level of performance than my 242 does.

With all the stuff I did to my boat (re-doing the impellers) ... imrpo's said (last week) they should have shipped mid this week. My advice would be to take the scientific approach of guess test and revise, one test at a time . Those spacers make a BIG difference and I changed out spacers and impellers at the same time (now I blow out my holeshot unless I'm either at the gorge or at 'Nelle with the boat loaded down).

 

[djsquid]

@sysinu Adam at Southvalley suggested that with these mods I probably should leave my impeller stock and not change the pitch unless I am sure I need it.

 

[Ronnie]

Please help me understand or validate my understanding here guys. I've always read and experienced that our engines are rev limited. On the 160 hp mr1 (1,052 cc) i maxed out at 10,200 rpm at sealevel. On the 1.8L engines I think I see around 7,800 max. If this is correct than most of the bolt on performance improvements (adding spacers, making the air flow into the engine less restrictive with better or no air filters, etc.) will only help me get to the max rpm faster they won't improve my top speed.
Is this correct?

Changing the pitch of my impellers is the only way to increase top speed at max rpm. Is this correct?

Misc.: As far as I know, top speed and acceleration are inversely related when it comes to pitch changes (I.e., you can have one or the other but not both and increasing one means a corresponding decrease in the other).
Any disagreements on this?