TPS Values When WOT for MR-1 HO with 4 throttle butterflies.

[Beachbummer]

So I hooked up the YDS today to check on my TPS sensor hoping I may notice something odd causing the loss of 500 or so RPM at the top on the starboard engine. Both engines had very similar values for the TPS but I was surprised that WOT values are 80 degrees and 3.82 volts. Is there anyway to set or indicate to the ECU that this is WOT? seems 78 degrees is not quite WOT although the throttle plates are actually dead open at 90 degrees.

I was hoping this number was low and could affect fuel delivery on Starboard, but port runs perfect and has the same numbers.

Anyone noticed their TPS values with the throttle fully opened and remember what it was? Any way to adjust it? I'll be looking at other possibilities to find my missing RPMs since the values are consistent across both engines and the one engine works great, but I wanted to confirm with others if possible.

Thanks!

 

[capt]

Please keep us informed if you figure this out. My starboard is at 9500-9600 @ wot can't figure out why.

 

[Gym]

Not to be Capt Obvious here but I'm assuming you guys have changed spark plugs, removed air filters, swapped coil packs between engines, checked throttle cable adjustment @ throttle body & checked impeller/liner clearance to make sure the impeller is not making contact with the liner as mine was.

 

[Beachbummer]

Coil pack not swapped yet, all others yes for me.

 

[Gym]

Coil pack not swapped yet, all others yes for me.

Regarding the coils. you could have one that's not putting out peak voltage due to breakdown or a high tension leak. It would be an easy check. It's also possible you could have a dirty injector causing a bad spray pattern. Possibly a can of Sea Foam or sending out the injectors for overhaul might resolve.

 

[Beachbummer]

Thanks for the thoughts!
I will swap coils and gauge to start, then go from there.

 

[Mainah]

FWIW most throttle body systems are 5v reference.

 

[Beachbummer]

FWIW most throttle body systems are 5v reference.

Yes, it shows on the YDS screen too as the range 0-5v which gave me hope that was the issue. Since the other was identical I don't think that's the issue.

 

[buckbuck]

@Beachbummer Here are some WOT numbers I caught on the YDS. Please note that this was during a time I was tracing an overheat issue. I don't think it would alter the TPS information.

 

[Beachbummer]

THANKS! this is very helpful. Not sure why WOT reads this way, but it does.

TPS voltage (0.5-4.5)	3.94​	V
Throttle valve opening (0-90)	81​	deg

 

[Beachbummer]

So I tested after swapping coils and it was a no go. same behavior. I also thought my engine compartment sealing could be starving the engine from air, so I tried opening the engine cover slightly to see if the RPMs went up, but they did not. When I did a compression check with the borrowed gauge from Oreilly, the gauge kept going up and up, I got all the way to 210 on one cylinder, the other all made it past 180 and I stopped cranking. This seems really high, so maybe some carbon build up or dirt in valves. I got a seafoam spray can to try to clean the intake and valves, but did not get to try it this weekend. It won't be in another 3 weeks due to traveling that I will get a chance to try that. If that's not it, I'm planning to figure out how to remove the injectors for cleaning. Ideas welcome.

 

[buckbuck]

Cleaned my injectors once. I remember it being a big job to get them out. Be careful with the manifold pressure sensor. I broke mine when removing the hose.

 

[Beachbummer]

I tried swapping the pump for another I have on hand, and both pumps seem to spin freely without issues, and the boat did not improve with the pump change. I will be trying the Sea Foam intake cleaner with some hope. If that fails I will likely have injectors cleaned next winter. Any other ideas are welcome!

 

[Midnight2V]

Just FYI but most systems dont read beyond 81-82. The reason for this is that the throttle blade shaft, which is significantly wider than the blade, shadows the blade when opened beyond 81-82 degrees. There is virtually no increase in airflow beyond that point as a result.

 

[Beachbummer]

UPDATE!!!

So with high hopes I replaced the injectors on the boat today, and no dice. I also cleaned the bottom of the boat and the boat gained quite a bit of speed, but the RPM difference remains. Starboard is still much lower than port, even with the "soft" stock port impeller on it.

My next attempt in hopes that somehow the fuel pump is not pumping with enough power is to switch fuel pump hoses from one to the other for just a trip, to see if it makes any difference. I have fuel separators on order and I will try that as a brief experiment next. Anyone ever had low fuel pressure result in lost high RPM? I'm thinking if that's not it I may swap the whole throttle body from one engine to the other... I'm close to stumped.

My starboard starter is also going bad.. Clicks and nothing for a while until I retry enough and it eventually works. It's on order we'll see how I can get that installed.

 

[Gym]

@Beachbummer. I haven't gone through this whole thread but

UPDATE!!!

So with high hopes I replaced the injectors on the boat today, and no dice. I also cleaned the bottom of the boat and the boat gained quite a bit of speed, but the RPM difference remains. Starboard is still much lower than port, even with the "soft" stock port impeller on it.

My next attempt in hopes that somehow the fuel pump is not pumping with enough power is to switch fuel pump hoses from one to the other for just a trip, to see if it makes any difference. I have fuel separators on order and I will try that as a brief experiment next. Anyone ever had low fuel pressure result in lost high RPM? I'm thinking if that's not it I may swap the whole throttle body from one engine to the other... I'm close to stumped.

My starboard starter is also going bad.. Clicks and nothing for a while until I retry enough and it eventually works. It's on order we'll see how I can get that installed.

Have you checked the throttle cable Interface in the engine compartment? Is it all the way to the high stop at full throttle? The starter issue could be your starter relay contacts are burnt.

 

[Beachbummer]

On Mine the cable drives the throttle body directly, and, the movement of the throttle goes to wide open when the lever is forward.

The Engine does emit a loud click when the starter does not crank...To me it sounds loud enough that I'm hoping for the starter and not the relay... Any thoughts on that?

 

[Beachbummer]

So, Starter Relay replaced, and starting issue was resolved, so that's good.

Injectors replaced, but same behavior remained. RPMs are matched between the two engines and same throttle opening, until about 4,000 RPM, then they start deviating slowly, after cleaning hull quite well, with the soft impeller on the startboard side, indicated RPM for port is 10,400 and starboard is 9,600.

I also swapped Fuel Pump (lines) from one engine to the other for a ride as a test, and my hope that it was caused by low fuel pressure was a fail. Problem remained with starboard engine. I plan to connect YDS again and try to see if anything is revealed. I was reading a bit about the Intake Pressure sensor also... Anyway, I'm hoping YDS will reveal something.

So far tried...
Verified Throtte Body opens all the way
Different Pump and "softer" impeller
Cleaned Hull with Barkeepers best Friend (WOW, Cleaner than ever, regained 4 MPH with a light boat)
Swapped Ignition Coils
New Spark Plugs
Swapped Air Filter
Sea Foam Spray on intake
New Injectors

Ideas welcome.

 

[buckbuck]

Is it possible inputs to the ECU are reporting different numbers at WOT? For instance, the TPS on the port engine is different than the TPS on the starboard. Would this effect the mapping enough at WOT to cause an 800 rpm difference?

 

[Beachbummer]

The TPS looks good, but I need to check the others. I was wondering how likely the Intake Pressure sensor was in contributing if it was slightly messed up. I'll save some data next time.