New member and new Suzuki owner DF40A

[mmanuel]

2014DF25ARS- If you take off the air cleaner cover and the air cleaner, then open the throttle wide open so you can see past the throttle butterfly, you can see if its got a restrictor. I looked at mine, wide open! I think the ECU should be able to figure it out. The one thing about automotive systems is that the ECU uses the O2 sensor to measure the resulting exhaust and fine tune the fuel curve and the outboards don't seem to have an O2. lean fuel curve = HOT!

[mmanuel]

2014DF25ARS - the ECUs have different part numbers, the assumption being different firmware

[Moonlighter]

Lets all not forget that the DF40/50/60 A series are all built on the same block, cylinder head etc. Although they do have different ecu part numbers so that is clearly different. But we can compare other parts in that series between motors to see what the difference is.

So we cant go comparing their parts with the DF25/30 series. You could compare the 25 with the 30, though.

As for O2 sensors, i am not 100% sure if they have them or not, cant see anything specific in the Suzuki literature for this series, although I know they were introduced on the larger hp engines such as 100 and above when the A series ("Lean Burn") versions were released.

Edit: Ive checked the parts listing and it appears that there is no O2 sensor on these smaller engines, though.

[mmanuel]

Moonlighter- Yeah we have had this discussion of DF25/30A similarities before, mrpister has just re-kindled the conversation with his observations on the 40/50/60

[Moonlighter]

All good!

It is going to be interesting to see how things progress with your 40, i have one on a little river tinny, and if it all goes well with your "improvements" we might follow suit!

Cheers and keep us updated on how things go.

[mrpister]

Silencer holder picture for the 60hp attached.

I tried my "40" with the 50 silencer holder and 1" larger pitch prop. It came with a 13" pitch and I bought a 14" pitch. I am still hitting the rev limiter at 6200 rpm with the 14" pitch, but only sometimes. I gained 7 km/hr (from 50 to 57).

Time to try a 15" pitch.

I still need to pull a plug to see if it is running hot. Although even the stock setup looked like it was running lean when I changed the plugs this spring. I guess Suzukis truly are "lean burn".

Some on the Yamaha forum say the Mitsubishi ECU compensates for the extra air and some say it doesn't.

[mrpister]

I am worried about running the engine too lean obviously as many experts say the ECU cannot adjust for the extra air flow. Before I install the 60hp silencer holder, I want to be sure I won't blow her up.

Reading about how the ECU can compensate for the extra air flow without an O2 sensor, I found this and it makes sense:

"The Manifold Absolute Pressure (MAP) sensor is a key sensor because it senses engine load. The sensor generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment.

When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine sucks in more air, which requires more fuel to keep the air/fuel ratio in balance. In fact, when the computer reads a heavy load signal from the MAP sensor, it usually makes the fuel mixture go slightly richer than normal so the engine can produce more power. At the same time, the computer will retard (back off) ignition timing slightly to prevent detonation (spark knock) that can damage the engine and hurt performance.

On engines with a "speed-density" electronic fuel injection system, airflow is estimated rather than measured directly with an airflow sensor. The computer looks at the MAP sensor signal along with engine rpm, throttle position, coolant temperature and ambient air temperature to estimate how much air is entering the engine."


I have ordered the Suzuki SDS diagnostic tool and software so I can read the ECU and see what temps the motor reached with the 50hp silencer holder. My brother is a mechanic so I will have him look at the plugs as well.

[Moonlighter]

Good work, you are approaching this in a very sensible and thorough way.

Looking forward to further updates.

[Pot Hole]

MPR,

Since I chimed in on this DF40 upgrade discussion, I am following this thread as well. Really looking forward to what you can find out and any progress you make. I've got limited equipment, but if this mod is something fairly simple, I can make it happen.

Please keep us updated.

[mrpister]

Sorry for the delay. I received the SDS tool, but have not had a chance to hook it up. Work has me very busy.

Rest assured, as soon as I have more information, I will post any news.

[allycat]

Allycat

Hi guys, just coming in on this thread but wondering if you felt an increase in out of the hole response ie; torque, the problem i have with my DF40 is my hull sticks a bit and is lazy getting up but once running will reach max rpm. An increase in torque would definitely help this out.
Cheers
Just another thing about the ECU's,I priced a DF60A ECU the other day off a dealer using part #33920-88L80, interestingly he asked for the VIN# but I explained I wasn't near the motor so he had a look on his parts software and said that the part # I gave him fit the 40-50 and 60 ???? So I will be keen to see your results.

[Pot Hole]

...Just another thing about the ECU's,I priced a DF60A ECU the other day off a dealer using part #33920-88L80, interestingly he asked for the VIN# but I explained I wasn't near the motor so he had a look on his parts software and said that the part # I gave him fit the 40-50 and 60 ???? So I will be keen to see your results.

If that's the case, then an ECU change may not be necessary for the mod?

Mrpister, keep us posted.

[allycat]

I have now rang another dealer using the part #33930-88L20 which is the actual part # on the ECU off the DF40a that I have and asked if this will fit "my DF60a" as I needed to replace a failed ECU and the ECU I "found at the wreckers" was off a DF40a, again the answer was that it will fit, I asked whether it would have different parameters and the reply was that his info says it is a direct replacement. I'm beginning to think that the different ECU part numbers are used to throw us of track so that we will purchase the ECU which is priced to compensate the difference in new engine prices between 40-60.
Still await the results of some tests though.
Cheers.

[n816kc]

another data point

I have a 2003 DF40 and have been waiting for MrPrister to update his findings. Well, I got a little impatient and decided to open up my restrictor holes to approximate the 50 restrictor. I pulled the silencer and surprise, no restrictor in place. I'm guessing the prior owner of the boat had already pulled it. I have no way of comparing the before and after performance, but have been running the boat for the past 5 years with no issues whatsoever. Plugs look good and the motor performs well. He did upgrade to a larger stainless prop, RPM tops out at 6000+-. If I get motivated, I may put the original prop back on for comparison purposes. Will post results here when/if I do.

[Moonlighter]

I have a 2003 DF40 and have been waiting for MrPrister to update his findings. Well, I got a little impatient and decided to open up my restrictor holes to approximate the 50 restrictor. I pulled the silencer and surprise, no restrictor in place. I'm guessing the prior owner of the boat had already pulled it. I have no way of comparing the before and after performance, but have been running the boat for the past 5 years with no issues whatsoever. Plugs look good and the motor performs well. He did upgrade to a larger stainless prop, RPM tops out at 6000+-. If I get motivated, I may put the original prop back on for comparison purposes. Will post results here when/if I do.

Now you must realise that the 2003 Df40 was a different motor to the DF40A series.

The reason why this discussion is about the DF40/50/60 A series engines is because they all share the same engine block and cubic capacity, and other features. So they are the same "engine family".

So you would need to go back and check the specs for the 40 in 2003, i think you will find that it is not in the same engine family as the 50 and 60 from that era.