2017 response txi question

[OscawanaSkier]

@jstaab3 Do you have pics of inside of motor box around billet? How much difference did that step make? How much plastic did you remove? Additional noise after removal? I took a close look at the billet today, but haven’t ventured down that road yet.

[jstaab3]

I will take some pics when I’m in the boat next and post them, most of the gains came when I installed the blower

[GregHind]

You need about 200 litres per second to run a ski boat v8 at 4000rpm. That is a lot of air, a 5 amp 75mm fan hooked up to a Flexi duct would never move that much. Clearly the testing has proven it helps so it must be to do with heat soak more than air volume

Still it would be very interested to measure the difference in air pressure at 4000rpm with the engine cover shut vs ambient. The negative pressure could be significant and looks like it would be with the way these engine covers seal and such long paths to get air in.

All that supply air restriction is “negative boost” the opposite of turbo charging. Easy to measur for any aircon tech who has a decent manometer.

[UWSkier]

Back when Malibu had the cone-style air filter and intake on the back of the Monsoons (starting around '03ish), there were those who swore their boats ran better with the cupholders removed...

[LeonL]

I can confirm that the local (fairly local anyway) promo guy blocked the engine cover up with a couple of 2x4s and it didn't help. So, engine cover seal and air path seem moot points.

[jstaab3]

 

[Dacon62]

The older style Malibu motor box (2014 or older I think) had a passive vent just above 3 cup holders on the rear of the box. Maybe they should just go back to using those?!

[GregHind]

@jstaab3 that photo looks like a breather blocked by ski ropes? What are you showing us?

[Conor]

@GregHind I believe you are seeing ski ropes that are coiled up on the floor. You see them because @jstaab3 cut out the black baffle behind the billet aluminum piece on back of motor box . With the motor box all the way open, that vent rests on the floor which is where the ropes are seen.

[jstaab3]

yes that is correct, @Oscawanaskier asked for a picture of the motorbox cut out so I opened and took a picture, rope happened to be on the floor under motorbox

[braindamage]

@jstaab3 what did that do for engine noise?

[jstaab3]

@braindamage no change on noise, but really changed performance of boat, skis great!!!

 

Jason Staab

[OscawanaSkier]

One additional thing to check: Last weekend driver seat heater wasn’t blowing air. I pulled the plastic bin behind the starboard bow seat to see if the hose had come loose. Sure enough it had. THEN also found out the motor box vent hose had also fallen off!! Two metal hose clamps later (factory had used plastic wire ties), and hoses were securely fastened.

 

Can’t say for sure how much difference it made, but AIT seemed to be a bit lower today over yesterday. It certainly didn’t hurt.

 

If you’re seeing high AIT’s double check your vent hoses behind both bow seats.

[DW]

Looked at a new TXI and concluded that the air inlet path is pretty tortuous and with the tight confines certainly any steps to improve the ambient air path to the air filter will pay some dividends. As noted by @jstaab3 he improved his condition with the changes made. The newer engine setups also have quite a bit more heat soak material and reduce open space under hood which will aggravate the issue. Not sure why the air inlet is now a low pressure area rather than neutral or positive pressure.

[Golfguy]

This seems like a fairly recent issue for the engines. Is there another factor involved, such as the addition of catalytic converters. Hotter air is less dense so more is needed.

 

[dvskier]

It seems like the catalytic converters have added a lot more heat.

[Gar]

My 2008 Malibu had those seems that issue has already been accounted for?

[bbruzzese]

Hey has anyone installed the heat shield that's supposed to go between the IAT sensor and the alternator? If so, do you have a picture?

[OscawanaSkier]

Someone in another thread asked that I post my solution to the IAT problem with my '18 TXi, so I decided to revive this old thread and post it here. Apologies in advance for the REALLY long post. I wanted everyone who has this problem to have all the info.

 

I've been using this solution since about May, including rapid fire course skiing, also in 100deg+ weather, so I'm very confident I've solved this for the long haul. Be aware though, my solution is a band-aid, but a very workable and easy to apply one. Also, I'm not a mechanic or an engine expert, just someone trying to troubleshoot this annoying problem.

 

First, a summary of the IAT problem (hopefully saving others from having to piece together the same info from the above thread). What people have seen is that the 17-19 TXi, after being run for a while (like skiing a couple sets worth) starts to have noticeably slower starts. Typically the solution has been to open the engine cover for a few moments, letting the hot air out (unacceptable from my POV). Upon further investigation, it turns out the engine's Intake Air Temperature (IAT) going above 140degF triggers the engine's electronics to hold back the timing and engine output (the cause of the low engine performance and slow starts). One note - IAT is NOT the temp you see on your dash's main screen. To see the IAT, you need to go to "Settings" and "Engine Diagnostics" and look for the IAT line. Also note, the IAT is only accurate if the engine is running.

 

Now for my many conclusions based on my testing earlier this year. These are based on a lot of conversations with Dennis Kelly at Malibu (who has been a fantastic help), and a ton of in-boat testing, including temperature sensors added in different locations under the engine hood.

 

Conclusion #1 - Is there a problem with the TXi's air path? No, I don't believe so! When the boat is moving (causing airflow through the vents in front of the windshield), the IAT always seems to go DOWN, proving that air is moving through the vents, the ducts in the boat's hull, and through the engine compartment. Could it be better? Maybe. Hard for me to judge

 

Conclusion #2 - When does the IAT climb? After the boat stops moving after a high RPM run (like a skiing pass). Obviously not ideal for a ski boat. As soon as the boat begins moving again though, the IAT goes down, but when you stop at the other end of the course, the IAT climbs higher again, and usually higher than the end of the previous pass, eventually climbing above the 140deg.

 

Conclusion #3 - How accurate is the IAT? Is it really that hot at the flame arrester (the silver mesh dome at the top/front of the engine - where the IAT sensor is located)? - When the boat's at rest - YES! The IAT was always within 5degF of my added temperature sensors when the boat was stationary.

 

Conclusion #4 - How quickly does the ACTUAL temp in the top of the engine compartment go down? Almost instantly once above about 10mph. HOWEVER, the IAT reading on the dash touchscreen never seemed to react that quickly - there was always a lag (which might be the sensor, or the touchscreen - who knows). This lag seems to be a contributor to the IAT problem as the engine thinks the temp is higher than it really is for the first few moments of a pass.

 

Conclusion #5 - Is the close proximity of the alternator to the IAT sensor the cause of this problem? Probably not - but it isn't helping things. Dennis sent me one of PCM's prototype heat shields - a piece of metal that you bolt between the alternator and the flame arrestor. But guess what - it's metal! And it did what metal does, conduct heat - so within a few minutes, the shield was nearly as hot as the alternator. I then wrapped it in insulation, dropping the shield's surface temp much lower - but it still didn't solve the problem. The IAT did seem to climb more slowly, but eventually it crossed that 140degF threshold.

 

Final Conclusion - Heat buildup when the boat isn't moving, along with additional heat from the alternator, along with a slowly reacting temp sensor - combine to create the +140IAT reading, causing the low-engine performance.

 

Now to the solution I'm using. This is largely based on @jstaab3 's addition of a secondary blower into the engine compartment. But Jason sent me a video of his, and the noise was just too loud for my liking. So I set out to find a high CFM, low-noise blower that could work. I then found a place to mount that blower lower in the engine compartment (cooler air), and then duct that air efficiently (without losing air flow) directly up to the flame arrestor and the IAT sensor. In testing many different ways to do this, the ONLY way it worked all the time was to blow air RIGHT on to the flame arrestor.

 

Here are a few photos of the install:

 

 

These are the parts I used. Total cost $110:

Bilge Blower 112cfm: https://tinyurl.com/yxo3f5bv

Shop Vac Hose: https://tinyurl.com/y3otgkfe

Shop Vac 90deg Brush: https://tinyurl.com/y3f2tdgb

 

I mounted this very quiet blower in the rear-portside corner of the engine compartment. At least on my boat, it actually sits there on its own, but I did add a piece of Velcro to the back of the blower motor, and attach it to the end of the fiberglass floor (see below)

 

 

For the hose, the more rigid shop-vac hose moves air very efficiently. Luckily, this particular hose has an end that perfectly press-fits into the above blower (not designed that way - just lucky). I also cut the hose to the perfect length, and moved the hose connector (easy to do).

 

At the sensor end, I took the 90deg shop-vac brush, removed the brush part, which gives you an efficient 90deg bend (MUCH more air flow then bending the hose).

 

I then zip tied the hose down along the path. One note - you MUST remove the red engine cover (just pull up on it). The hose will not fit under it, or over it. One more thing, I left the heat shield in place (you can see it in the photos above), which made mounting of the 90deg elbow easy. But I think it's doable without it too.

 

To finish this off, I wired the blower into the boat's electrical system by disconnecting the LED within the engine compartment (this is under the fiberglass floor plate that wraps the pylon - remove the three screws, and carefully slide the floor piece up. Be very careful not to strip out the fiberglass when you reinsert the screws!). You can see a photo above in my post from Sept 2018. I simply disconnected the LED, inserted the power leads from the blower into the connector, and carefully wrapped with electrical tape, then zip tied it so it would never sit in water at the bottom of the engine compartment. I will likely buy the same connector over the off-season and replace.

 

With the blower wired into the system - I can turn it on/off by using the "Storage" lighting control switch on the touch panel.

 

The end result: I now have easy control over this nearly imperceptible blower, which keeps the IAT at approximately 125degF, and the best part - the TXi is now a BEAST! All the complaints from my ski buddies are gone.

 

One thing you might be wondering - will this band-air hurt the engine. Again, I'm not an expert, and I suppose I'm taking some risk applying this fix, but I came to the conclusion the risk was minimal. I leave this blower running the whole time I'm skiing anyone, which seems to keep the air temperature in the top of the engine compartment quite consistent, not just at the IAT sensor.

 

I hope the above helps at least a few of you. If you have any questions, just post and I'll try to reply as soon as possible (I'm on a skiing staycation this week!)

[jstaab3]

nice work!

[JaredSmith]

@OscawanaSkier Thanks for the detailed post. This is something Malibu should have fixed by 2018 and warrantied!

[OscawanaSkier]

Yeah...my guess is that there's a lot of finger-pointing between Malibu and PCM, and probably not a lot of desire on PCM's part to work the problem as Malibu is now making their own engines. Sadly we get caught in the middle.

 

I'm going to send Dennis a link to the above, as I haven't shared the final outcome with him yet. I'll let everyone else know if I hear anything back.

[WBLskier]

I’m looking at buying an ‘18 TXI. Owner says it’s had zero issues. Has this problem been resolved? Does it affect only certain boats? The one I’m looking at has a monsoon. Has this issue been with a specific engine model and if so is it the 6.0 monsoon?

[UWSkier]

@WBLskier it's been with a very small subset of boats

[OscawanaSkier]

@WBLskier My ‘18 TXi is a 6L. I really can’t comment on what percentage of boats have had this issue. I have heard from a number of people who ski tournaments and course skiers who have experienced this issue. Based on my findings, if you free ski mostly, where you’re running the boat for more than 45sec at a time, you’ll likely be fine, as the IAT has time to come down during your run.

 

Also, my desire to solve this issue was also rooted in our physical course setup - which is pushed close to shore on one end. The boat struggled to hit 32mph before hitting the gates (now that happens about 75ft prior). If that’s not an issue for you, or you and your buddies don’t want/need a lot of boat on your starts...you won’t care about the IAT problem.

 

You should know...my wife and I LOVE this boat. You will too. I went to TN and toured both MC and Malibu, and ultimately chose Malibu for its great design. It’s a great boat for many reasons. I have done a number of other tweaks as well, so if you end up getting one, let me know and I’d be happy to share my list.

[OscawanaSkier]

PS - written from said boat!

 

[bbruzzese]

Hi, I have a 2018 and am thinking of making this, what looks to be, easy mod. Before I started I thought I'd just check back in and see if things were still running well and if you'd made any changes now that you've been running it a while.

 

Also, I love this boat as well.

 

Thanks

[UWSkier]

Rather than tying it into a light, any thoughts of having it run any time the screens are powered up with a switch to interrupt it when you just want to sit and listen to tunes or something?

[stxskier]

I bought Staab’s boat mentioned and shown in this thread a year ago. Haven’t had any issues with it.

[OscawanaSkier]

@bbruzzese - Still works great. Only change I made this year was to make a better connection to the boat's electrical, essentially T-tapping into the wiring harness to the light, so I can have the blower AND the light together.

 

@UWSkier - There might be some circuit that is "hot" while the touchscreen is on, but I found the engine compartment light an easy way to get control, and while the blower is very quiet (most people never notice it) it's really not needed except when skiing the course - so no need to put extra hours on that little fan motor.

[bbruzzese]

Thanks everyone. Parts on order.