Closed Cooling System on Port Engine Running Hot(ter)

[tpenfield]

Me again . . .

Also found some stuff that gives a scientific explanation (via an engine lab testing) to the effects of ignition timing and the peak pressure built up within the cylinder as well as the exhaust gas temperature that exists the cylinder.



So, if the ignition timing were off (late) by about 5 degrees of the optimum, it could result in the exhaust temperature being about 70-100 degrees F hotter. Interesting stuff . . . versus the folk lore.

 

[HT32BSX115]

So, if the ignition timing were off (late) by about 5 degrees of the optimum, it could result in the exhaust temperature being about 70-100 degrees F hotter. Interesting stuff . . . versus the folk lore.

Later (retarded) timing also usually results in a fair amount of LESS power too.

Shouldn't that also result is a higher (required) throttle setting, compared to the other throttle?

Let me also say that in aircraft engines, a 100 degree higher EGT (Exhaust Gas Temp) results in a barely noticeable increase in cyl-head and oil temp.

That same increase might be less noticeable in a liquid cooled engine....

 

[tpenfield]

Definitely less power as the timing is retarded. I may want to check the performance of the boat versus my testing a few years ago. I have a boat speed vs engine RPM chart that I made before this engine heat thing all started.

One of the things that I am thinking about is that if the port engine also has less power, then the starboard engine is picking up the slack. I should see the net result in a lower boat speed for a given RPM, since the port engine is more or less 'going along for the ride'. I generally try to keep the engines at the same RPM, but the throttle settings are pretty crude, never were identical because of the control cable adjustments being a bit off. It is certainly something I can pay closer attention to though to see if there is a noticeable difference.

 

[HT32BSX115]

the throttle settings are pretty crude, never were identical because of the control cable adjustments being a bit off. It is certainly something I can pay closer attention to though to see if there is a noticeable difference.

Vacuum (or manifold pressure in IN HG ) is a pretty good indicator of throttle setting.

Since you do not have adjustable (governed) propeller pitch control, and they're identical, if the engines were otherwise identical in power producing capability, setting the same manifold pressure *should* produce the same (or very close to the same) RPM.

It works with carbureted engines, but might be variable with EFI because the ECM might try to compensate with changes in timing and/or fuel delivery at a constant RPM, but vacuum (or manifold press) should indicate throttle butterfly angle (and commanded throttle setting)

 

[tpenfield]

Vacuum (or manifold pressure in IN HG ) is a pretty good indicator of throttle setting.

Since you do not have adjustable (governed) propeller pitch control, and they're identical, if the engines were otherwise identical in power producing capability, setting the same manifold pressure *should* produce the same (or very close to the same) RPM.

It works with carbureted engines, but might be variable with EFI because the ECM might try to compensate with changes in timing and/or fuel delivery at a constant RPM, but vacuum (or manifold press) should indicate throttle butterfly angle (and commanded throttle setting)

Seems like I would have to have both engines connected to a Diacom computer to compare them at that level in an apples-to-apples fashion. Among that, steering the boat at a reasonable speed, and the cooler of beer, it all seems like a lot to juggle at once

 

[HT32BSX115]

Seems like I would have to have both engines connected to a Diacom computer to compare them at that level in an apples-to-apples fashion. Among that, steering the boat at a reasonable speed, and the cooler of beer, it all seems like a lot to juggle at once

You're just going to have to break down and let someone else drive your boat.......(although it would be very hard for me!!!)

 

[tpenfield]

You're just going to have to break down and let someone else drive your boat.......(although it would be very hard for me!!!)

True.

 

[achris]

RPM versus boat speed will tell you nothing. That's something that will affected by the weather, condition of the hull and boat load, but not the engine power. As long as the engine can produce enough power to turn the prop at a given rate, the boat will run at x speed. What you're looking for is how much fuel the engine is using at a given load, and that's a lot harder to find. I can't remember, does your ECU report gallons per hour back to Diacom? (Mine does, but that's a PCM555, yours is a MEFI1). I think checking the base timing is going to be your best starting point.

Chris......

 

[achris]

You're just going to have to break down and let someone else drive your boat.......(although it would be very hard for me!!!)

Me too!

 

[tpenfield]

I do get a GPH reading from the Diacom. Not sure if it is directly from the MEFI or if Diacom is calculating it.

The bay should be flat today, so maybe I can get some decent runs at cruising speed and record them with the Diacom.

The whole ignition timing thing is fairly interesting . . . the design challenge is taking fuel, which burns at a fairly constant rate, to effectively operate within an engine that varies its combustion cycle speed from idle to WOT by a factor of 8-10. The timing advance tries to compensate, but it cannot increase the rate at which the fuel burns to match the speed of the combustion cycle.

I'm sure there is an optimum speed of an engine based on how fast the fuel can burn. :noidea:

 

[alldodge]

Don't see how the MEFI 1 can measure or calculate a flow rate, it doesn't have a flow or water pressure sensor. Real low ability of checking much with only 7 points

 

[achris]

....I'm sure there is an optimum speed of an engine based on how fast the fuel can burn. :noidea:

That's why we have knock sensors. The ECU will advance the timing until it detects a knock (piezo crystals cut to oscillate at the frequency of detonation and produce a voltage output). It will then back the timing off until the knock disappears. Then it will start the cycle again. All this will be done at a rate of a hundred times a second, giving you the optimum timing for the quality of the fuel and the load and speed of the engine... And they (the 'horse and cart' crew) tell us points and carbs are better. :facepalm: Well, let's see them perform that little trick.

Chris......

 

[achris]

Don't see how the MEFI 1 can measure or calculate a flow rate, it doesn't have a flow or water pressure sensor. Real low ability of checking much with only 7 points

As far as I'm aware, no MPI engines have flow sensors. It's done mathematically. They know the engine speed, and how long they are commanding the injectors to open. In the programming will be a constant which is the volume the injectors will flow at. Simple x times y times z will yield gallons/hour.

I do a similar thing in my boat. I do have a fuel flow sensor in the incoming fuel line (I fitted a few years ago, Navman Fuel2100). The readout is on the instrument dash. I also have a GPS chart plotter giving me my speed in knots. Simple math gives me litres of fuel per nautical mile. eg. I'm traveling at 24 knots, and the flow meter is reading 29 litres per hour. 1 litre per NM would use 24 litres, but I'm using 5 more, so 5 divided by 24 is roughly a fifth, so consumption is 1 and a fifth (1.2) litres per NM..... All us older folk who didn't grow up with a calculator or smart phone glued to our hand were taught how to do that.

Chris......

 

[alldodge]

Fuel flow rate I get no problem-o even for this old guy, but water flow rate no. My understanding is Ted was talking about two different flows or was I missing something again :facepalm:

You might be right with reaching knock and back off, but that sounds like a plan for disaster. My research and discussion with other engine builders indicate another method. When the motor is first being throttled up the ECM (MEFI 2 and higher) advances the timing to get a knock prior to motor reaching full rpm to programed advance curve. If it detects a knock then timing is reduced to normal rpm and is allowed to go full advance for the rest of the run time. If it does not detect a knock the timing is retarded about 5 degrees and a code 44 is set. During normal run time and no code 44 at start up the motor is advanced per its programed curve.

The MEFI 1 does not have a code 44 to set so if the knock sensor is not working it has no way of knowing

 

[tpenfield]

Chris,

The IAC that you gave me the link to appears to be the wrong one. It has a shorter throw length than the original and when I put it in the engine, it revs to about 1700 rpm and won't go any lower. I tried several IAC resets to no avail. I am thinking it is similar looks, but not the right one.

When I ran the IAC reset on the original one, I got an error. The starboard engine IAC seems to be fine the thing reset with no errors.

The only part number I can get off the original IAC is 00016 C2007

The ones you referred me to have the following number 00016 C3245

Any ideas on what the correct IAC would be at the auto parts store?

They don't seem to be referenced by the number stamped on them

 

[alldodge]

I used your part number 805224A1 and Rock auto shows it as AC5 and list the Merc number. If you go to rock auto and search just your number a one item will show up. If you select info it shows

Alternate/OEM Part Number(s): 17111809, 17111811, 17112350, 17112351, 217419, 805224A1

They sell for 23.79

You can back search the other numbers and they all come back to AC5, at summit and others. If you search GM IAC 217-415 it still looks the same but comes back as a higher price at Amazon and ebay

https://www.amazon.com/ACDelco-217-419-Original-Equipment-Injection/dp/B000C9I5FQ
http://www.ebay.com.au/itm/High-Energy-AC5-Idle-Air-Control-Motor-87-05-GM-/400462293045

 

[tpenfield]

OK my bad on the IAC . . . I did not get the throttle assembly put back together properly. All better

Even with the new IAC and it idling properly, I am getting an error on the test/reset.

No Mode 8 Reply

I am getting those errors on other tests too

 

[achris]

Wonder if MEFI1 is playing up. Is it easy to swap the ECUs across the engines?

 

[tpenfield]

BOAT FOR SALE . . . BOAT FOR SALE :facepalm:

I feel so defeated

I started out the day replacing the distributor and rotors. It turned out that one of the distributor cap screws was hanging on by a thread. When I went to fasten the new one down, the threads were completely stripped. :facepalm: Of course they are . . . why wouldn't they be

No, problem, I figured, I'll just put in a nut on the back of the distributor flange to hold that side down firmly. . . . Turns out that it is a #6 FINE pitch (40) thread . . . I had none, all the stores in town had none :facepalm:

So, I spent a few hours trying to rig something up . . .

Anyway . . . onto the timing. I used the Diacom to set the engine(s) into base timing mode and I checked the timing. They were both dead nuts on 8 degrees BTDC

So, I tested the IAC's, which is just resetting them. That is when I got the error message on the port engine. The starboard engine 'passed' all of the tests.

I then replaced the Port IAC, figuring it was the problem. That's when I messed up putting things back together and the engine was revving high at idle. Once I got that sorted out the engine idled fine.

I then did another series of tests on the port engine and got the error message on all of them. So, I checked the connections on the MEFI . . . disconnected and reconnected the 2 big connectors and remounted the MEFI, figuring it might be a faulty case ground or something like that.

Still error messages on the Port MEFI while doing the tests.

One thing I have noticed is that the starbd engine MEFI gets 'discovered' right away by the Diacom, whereas the port engine takes a while. I'd say 2 seconds for the starbd engine and 15 seconds for the port engine.

I'm thinking it may be a connector issue on the Port MEFI. I could swap them pretty easily, so GOOD SUGGESTION . . . hadn't thought of that.

And due to all that fuss and confusion, I brought back a fairly full cooler of beer :facepalm:

 

[tpenfield]

Another day, another run at it. . .

So, yesterday, I had planned on doing:

1) Change distributor caps and rotors (done)
2) Check/set base timing (done)
3) Test engine temperatures (done) No change, port is still 15-20 degrees F hotter
4) Check spark advance at idle (not done)
5) Test IACs - (partially done)

That is when I noticed the errors on the communication with the Port engine MEFI

6) Check fuel pressure (not done)
7) Compression test (not done)

So, the game plan for today is:

1) Swap MEFI Units between the engines . . .

Chris - you had mentioned in an email that the Starboard engine was set as the 'master' and the port was the 'slave'. . . and typically it is the other way around on twin engine setups.
---> Not sure where in the Diacom software it shows that. :noidea:
---> Will swapping the MEFI units change that?
---> also, a footnote . . . both MEFI units show substantially less hours that what the hour meters at the helm show. I am thinking/guessing that the MEFI units were replaced or re-flashed at some point earlier in the boat's life.

2) Check engine operation, temperature, etc with the MEFI's swapped . . . see if the temperature problem stayed with the engine or moved with the MEFI
3) See if I can run the tests on each engine . . . see if the communication problem stayed with the MEFI or with the engine.

4) There is a Fuel Pressure Test as part of the Diacom. . . and I am wondering if that will give me a go / no-go on the fuel rail pressure ??? :noidea:
4B) Otherwise, I'll do a fuel rail pressure test.

5) If I get bored, I'll do a compression test.