PCU Tuning

[ChrisXS2003]

I have twin stock 260's on a Stoker 22 SST. Idles well and runs very well when on plane.

The problem is planing the boat. If I hammer the pedal, she'll jump out of the water. Easing it on makes it go flat until I double pedal it. Motors are fresh, electrics are good, fuel pressure is fine...etc It's in the off idle tuning of the PCUs.

Anybody have an experience in the best way to adjust a PCU for good off-idle performance?

It's fun to drive this way, but my little girls won't like it tubing!

[STV_Keith]

Do you have a steam wheel? Does it like more or less fuel at this point in time? If you have the software, once you know if it wants more or less, you can get in there and tweak the map.

[ChrisXS2003]

I don't have steam wheels or software.

I think it's lean, although I didn't think to push in the keys to see if it would pick it up or not.

I'm wondering whether I should use the accel sens & volumn or the individual RPM bands to adjust it. I did increase the accel comps with very little difference.

Tried to call Tony and he wasn't in....

Thought or experiences?

Chris

[David - WI]

From what you describe, the acceleration enrichment is working when you "work" the pedal... but the accel sensitivity is too low to pick up your gradual pedal movement when you "ease into it".

[Fl Boy in ILL]

Chris

Do you have a Digitron and can monitor exhaust gas temps? I feel along with the PCU it is an ecential tuning tool

Rick

[pirogue]

also make sure the fitting for the map sensor on the horn is not plugged up.

[ChrisXS2003]

Thanks for the input guys!

I thought it was accel comp too. I did increase both sensitivity and volumn and it made little difference. I only increased them 2-3% though.

No EGTs installed...couldn't afford them after putting the motors together right. I agree they would be handy, but not sure how much help they would be at low RPMs....?

MAP sensor fitting is clean.

I did a search and found an old thread where guys were saying they needed to increase the 1000-1500-2000 RPM adjustments. I have Tony's 260 curve in them and I'm not sure what curves the others were running.

I had the boxes at ~105% during break in and the off-idle performance was the same. They're at ~101 now, so I know it's going to need at least +5% in those ranges if that's the right approach.

Thanks for input guys

Chris

[YELLOWSS]

i live by my egt's!!!!!!!!!! for tunning tony set mine a little hotter than the stock 260. i told him what i had he almost nailed it. i could be a little leaner on the top, but that is it. he played it safe which is smart!!!!!
you need to talk to tony.
i use my steam wheel all the time. it is a great tunning tool, but it is great for long idle zones too. no more loading up!!!!! my stock box was so rich i don't know how they ran it.

egt's give you a base line, so u know which way to go, and @ wot it is a must.
steam wheel can do the same thing as your running.

u really need one of them

you could lean it out and burn up those rebuilt engines.

call tony

good luck roy

[Carter Powell]

Chris:

Try richining the part throttle dial inside the the ECU. This took care of the same problem for me.

Carter Powell

[skydog]

Chris:

Try richining the part throttle dial inside the the ECU. This took care of the same problem for me.

Carter Powell


Mine too!! My EGT did not help me AT ALL!! It said i was so lean it was NUTS!! If i put the fuel to her to get the egts to about 1250 or so it was so so fat it would not even clean out!! My EGT read 1400-1450!! For two summers long!!

Skydog

[YELLOWSS]

depends on the location of the probes. also when you are very rich the probes can b reading the flame temp. the best way is piston, and plug reading. the egt's can help if installed at the right location and your are in the ball park.

roy

[skydog]

Yep piston wash and plugs!

[ChrisXS2003]

Heard from a couple guys that had the same problem. They increased the 1500 RPM adjustment +7%.

I like this approach the best because it only affects that part of the curve. In my case, the engines run fantastic at idle and above planing speed. I'll post what happens when I run it again.

Thanks for all the input guys!

Chris

[ChrisXS2003]

Finally got a chance to do some tuning on the PCUs.

I've got it pretty close now and just need to do some final tweeks to get them perfect. I added ~+8% in the 1000 and 1500 RPMs, and ~+4% in the 2000 RPM.

Using the "push to choke" function in the key switch is almost as good as having a steam wheel. If she picks up when pushing to choke, it needs more fuel in that range. If it falls off, it needs less or it's good where it's at.

On thing that's interesting. Even though I tried hard to build these (2) 260's identically, they don't act the same when tuning. They're close, but not the same. I've always heard that no two motors are exactly alike....proved out in my case.

[STV_Keith]

One thing to remember is that the pots on the box adjust the curve at only the very high MAP cells (closest to WOT). You need the software to adjust the lower MAP cells (say, under 3/4 throttle) in those RPM spots.

[Sam Baker]

How do you know what the EGTs should be reading at say 3500 RPM? I have EGTs, and I know on a 225 ProMax, the temps should be in the 1200-1250 range (they run a little hotter than a 260 from what I hear), but in the lower RPMs, there won't be as much heat due to less frequency of combustion. Is there a rule of thumb as to what the temps should be at various RPMs....any sort of a curve? I just ordered the software and should be getting it any day so I'll be able to look at the curve graphically. I also have a pyrometer that records and charts temps so I'm hoping I can marry the two together.

[tomoad]

I was wondering about that question too, In low RPM from 2000 to 3500 what should the EGT be. mine is running 900 to 950, after i get to 4000 temp comes up to about 1050 1100 but in the 2000 to 3500 motor spits /spudders (4 stroking rich) also just curious on a stock mercury box (ecu) of what the egts read in low rpm

[stvhelm]

it sounds like you need to turn down the part throttle adjustment.
everyones low speed adjustments may be a little different depending on how much vacuum your engine is pulling. svs / horn run different. On mine i had to richen the 500 + 1000 and lean the part throttle.

[YELLOWSS]

mine idles about 420.. steady increase through out he rpm range.... @ 3000 im about 750... everybody will be a little different!!!!!! i have some mods to mine and have some extra air coming in too.. mine kinda pulses up to 2000 rpm's too, if i go into it slow with a big prop 32p..... race props it just rocks!!!!!!! i have the steamwheel, and the software to program. tony gave me a drag program for my other powerhead too... super nice people.....

roy

[jimmybrie]

but it is great for long idle zones too. no more loading up!!!!! my stock box was so rich i don't know how they ran it.

good luck roy

I really need that PCU so I can lean it up when I need. Just missed the one sold by Mitch Hardee. Too bad...