Brucato ACU.....Where Are Your Settings!

[WillySteve]

Pretty sure Tony sets hes up to run at or around sea level. If your above 1000ft shes going to be rich. For my 225Promax I had to play around with everything at 2200+ ft above to get the right mix. if you have a steam wheel and pyro meter you can cut setup down considerably. Plug checks from WOT and turn off the key are not a lot of fun some times. haha If you let it idle at all your not going to get a true plug read. thats why a pyro and steam wheel would be best for set up. i had to lean the crap out of mine and increase fuel with shaved heads also as tighter heads love to eat fuel. Increase the air fuel as altitude has thinner air ect ect.. Once i found the right settings and plugs read great i never opened it again. That was 9 years ago and still running strong. i have a book i would write what I had and every change and its effect down. you have to do this our its easy to get lost. once i was getting into the ball park the slightest adjustment made a difference. Better rich than lean. But finding the sweet spot is going to take some lake days. Always use the same prop when testing also. You dont want to many variables. Weather temps also. I went to the same lake the same prop and recored everything. im happy with the result big time but it took some farting around doing it old school. Mods like tight heads will effect the acu calibration. I set mine up to run best at were I boat the most at 2200ft. Not as good at 3000ft and sick fast at 900ft. If I were to boat at sea level i would have to richen her up a little. An example my main is at -7.5 stock was +3. sens is +7 With 33cc heads from stock my vol is at +6, part is -1 idle -2 so its reads like this. -7.5 +7 +6 -1 -2 Stock for sea level was -4 +7 +4 0 0. As an example as my motor is not a 260 its a 225pm.

Doesn't the ACU compensate somewhat for altitude and temp changes? My original Mercury box which I ran for 21 years did and I thought the ACU did also?
Tony set my 260, (with 130# compression, mild port work, relieved exhaust chest and rod slots), at 0, +4, +4, 0, 0!

[WillySteve]

Please take my advice knowing I'm not an experienced boat tuner...but lots of learning on 2stroke snowmobiles. Your pistons look lean IMO. Fingernail size wash at intake ports is target on sleds (clean spot on piston at intake ports) - I cant see why it would be different on any other 2stroke. Whipper posted great photos last year (maybe 2?) of what I thought was perfect wash. Would hate to see you burn down.... again JMO.

Yes I do agree, after studying the pics and the way the engine ran I am going back to richer settings. One reason I feel it needs this is because the last time I ran at 6000rpm's for about a mile, I noticed that when I came down to an idle inside the 5mph bouys the engine was idling a good bit faster than normal which I should have caught immediately as possibly being lean!
I've really noticed the engine seems to be sluggish when I 1st nail it on holeshot until it reaches about 3500rpm which makes it hard to run a prop over 24P, even though a 28P runs super once the boat's up on plane! It just doesn't seem crisp off idle and with 1.87 gears it should pop out good with a 26P?
BTW, I never had a meltdown on this engine, it was rebuilt because it was just flat wore out after 21 years of running!

[WillySteve]

I talked with Tony this morning and he suggested my ohming out the engine temp sensor!
He also emailed me the specs on the sensor and being it's 21 years old, i suspect he may be on to something!!!!
More on this after I check it out!

[fiyashot]

Just wondering for a little comparison where everyone with a Brucato ACU have their adjustments set for a 260??
Mine was at but still piddling:
main= +5
sens= +5
volume= +4
part throt= +4
idle= 0

The ACU settings on my 260 with 150psi compression at sea level with the stock intake horn is:
main= 0
sens= +4
volume= +4
part thr=0
idle=+1

I lean the main and idle a bit when running the SVS system (i have a pyro and steamwheel installed)

[whipper]

i found I had to play with my air fuel screw to get a good idle going from a stock box to the digital ACU box. Yes stock box adjusted some what for altitude. But Tonys you have to set it for were you are. With tighter heads you need to add fuel to them. This wasn't stressed buy Jay enough. They need to eat to work best. i would see if turning your sens up a little Useing a magnifying glass!! LOL to +5 and buy increasing your sens it will decrease the threshold of throttle movement required to activate your Accelerator pump and might help hole shot? If your still a little rich try -1 or -2 for on the main also leaving sens at +5. If running real good check a few plugs #5 top port especially. Watch temps. If still rich turn down main .5 at a time. i found the main was the best one when testing after I messed everything up!! haha If your at 0 on the main and hole shot is week you have to much fuel at idle and its loading up. By trying .5 to a whole at a time and turning the key off from a reasonably high rpm 6000 or more and gliding to a stop will be your best reads on the plugs. if you idle the plugs get washed and your reads wont be accurate. At 130 comp you have way more room to play with than 145-160+ as far as to lean or rich goes. You lean out a 160+ comp motor to much and melt down is going to happen way faster than yours. I was a lake a few weeks ago and im at -7 on the main thats at 700ft above sea level like were your at. i ran hard every day for 21 days without issue at -7 were as -2 is wear Tonys settings were stock. Because you have a little mild work done to your motor its very hard for Tony to know exactly were the numbers will be for someone like you or me looking to get every ounce out of her. so i wouldn't be afraid to go into the Neg a little for one pass and see how that is. also it takes a little bit for the acu and your motor to adjust to the new settings. I would drive around a few min at different rpm before I made my plug read pass just so the adjustments had some time to take effect. Once you have good acceleration midrange and top end but idle sucks try turning the screw a little while at idle untill you get a decent idle. i mean the air fuel mix screw. Front port side bottom corner hiding back there. Final thing. is your cowl a stock merc cowl or after market? If its an after market that will change everything!! The Bobs cowl like mine doesnt have as big of holes for air and no duct work inside to direct the air flow were the stock merc ones did. i had to drill bigger holes in mine to get performance as I wasnt getting proper air fuel mix. Just a fyi. I got a little carried away with mine and now have about 20 holes and have adjusted my acu and my performance is very crisp for a 225 pm any were from hole shot on up. After a long idle though they all dog a little on hole shot untill the plugs clean up.

[texasvector]

The ACU settings on my 260 with 150psi compression at sea level with the stock intake horn is:
main= 0
sens= +4
volume= +4
part thr=0
idle=+1

I lean the main and idle a bit when running the SVS system (i have a pyro and steamwheel installed)

Less air with the svs??

[whipper]

The ACU settings on my 260 with 150psi compression at sea level with the stock intake horn is:
main= 0
sens= +4
volume= +4
part thr=0
idle=+1

I lean the main and idle a bit when running the SVS system (i have a pyro and steamwheel installed)

There go thats what you needed to hear Willy. See if Fiyashot is at 0 with 150 comp you can go -1 on the main with 130 comp. Because he has SVS he also wouldnt need as much sens as the SVS increases his throttle response over a non svs motor. So bumping up your sens +5 might be a good idea also. The rest looks the same as yours. i was typing my story book when he posted those numbers sorry for the LOOOONG explanation. haha Also he has the steam wheel and pyro so he was able to fine tune better than you could ever without those. i would work with those numbers and fine tune only a little from there. All at your own risk off course. haha

[whipper]

More air Texas vector. it probably also increases the fuel flow hence a little leaner with svs. Throttle response is increased along with fuel delivery much more better. Makes more power so takes more fuel.

[fiyashot]

Less air with the svs??

I drag raced when the svs was installed so i ran a higher egt around 1200 opposed to 1100 or so with the horn normal everyday running

[W2F a V-King]

Please take my advice knowing I'm not an experienced boat tuner...but lots of learning on 2stroke snowmobiles. Your pistons look lean IMO. Fingernail size wash at intake ports is target on sleds (clean spot on piston at intake ports) - I cant see why it would be different on any other 2stroke. Whipper posted great photos last year (maybe 2?) of what I thought was perfect wash. Would hate to see you burn down.... again JMO.

http://www.screamandfly.com/showthre...s-rich-or-lean

[WillySteve]

The ACU settings on my 260 with 150psi compression at sea level with the stock intake horn is:
main= 0
sens= +4
volume= +4
part thr=0
idle=+1

I lean the main and idle a bit when running the SVS system (i have a pyro and steamwheel installed)

Tony sent mine at:
main= 0
sens= +4
volume= +4
part thr=0
idle=0

With those settings I was having a problem with coming out with a clean holeshot and then kept noticing that the fuel enrichment would speed up my rpm's between 1000 & 2000rpm.
This is why I've been messing with it!
Talked with him today and he suggested turning up the sens. for the 1-2K lean mixture.
I ran a little today with:
main= 0
sens= +6
volume= +6
part thr=0
idle=0

and it felt pretty good but still, it really bogs in the hole with a 26P until it gets to 3000-3500rpm then runs like a big boy!!!!!!
My SM gearcase is a 1.87 ratio, 1" above pad and I think it should scream with a 26P prop on holeshot.....it does with a 23P...hold on to yer azz!!!!

[texasvector]

More air Texas vector. it probably also increases the fuel flow hence a little leaner with svs. Throttle response is increased along with fuel delivery much more better. Makes more power so takes more fuel.

He said leaner curve with svs ..tells me less air than horn??? No?

I get more air = more fuel= more power....but he said opposite

[texasvector]

Then again I could see...mani psi changing with svs there fore adding fuel when unwanted...in turn turning fuel down to compensate

[fiyashot]

I plan to reinstall the SVS next weekend to play with idle and accel volume myself. One of the reasons i went back to the horn was to compare holeshot. The horn currently leaves harder out the hole however the svs has stronger midrange and was 4mph faster in the quartermile testing back to back on the same day. I've been advised that there's a strong possibility the motor was loading up due to less vacuum with the svs. For some reason the motor difinately ran much stonger and was quicker with a leaner setting with the svs maybe that will change when i lean out the idle and experiment with the accel . On another note i did have a bogging issue in the past when i went from dual stage reeds to single stage (with the svs) and for some reason i had to lean as much as -9 to get a pretty decent holeshot but i didn't pressure too much on top because i didn't have a pyro at the time.

[texasvector]

Good info....-9 on idle circuit or main?