Thread:

tunning

correct procedures for tunning or the ten mistakes we make learning curve bbc natual asperation

Originally Posted by ohflat

correct procedures for tunning or the ten mistakes we make learning curve bbc natual asperation

The best thing you can do is put it on a dyno

The data on the dyno can spot trouble spots in power curve

And establish base line performance levels

Once tuned and jetted correctly,@ those Air temp,baro, relative humidity.

There are jetting formulas to correct for air changes you will experience during the season or altitude you boat at.

Originally Posted by TNYoungblood

Can you elaborate on the formula Steve. Mine was alittle fat on the dyno(done in February) and is alittle lean out on the river in the summer time.
Thanks

If your engine was lean at the river in the summertime..... it was not rich on the dyno in the winter....... unless you dynoed on top of a mountain and ran the engine in the boat in a low valley..... ..

[QUOTE=Gearhead;1582203]If your engine was lean at the river in the summertime..... it was not rich on the dyno in the winter....... unless you dynoed on top of a mountain and ran the engine in the boat in a low valley..... ..[/QUOTE

True enough!!!

Originally Posted by TNYoungblood

Plugs look alittle on the lean side After a pass Gear And of course my dyno session was junk

Gonna start fresh come springtime and get her dialed in

The constant load of a jet on the lake likes fuel Don't be timid about adding more while watching your tach, plugs, gps and time slips. It will show you what it wants

Gear

I WAS running a pump gas 9.3 comp. n/a 540 w/2 850s and a msd ignition. i was told reading the plugs when running the msd, that you look at the threads of the plug not the electrode. The msd has such an efficiant fire that it will burn the carbon off the electrode. I was told that w/msd that around 3-4 threads from the end of the plug should have a little color change (slight carbon). My header pipes were a very light chocolate color at the end of the collectors, some days it would be white to light gray (like race fuel) depending on air temp and quality.

Originally Posted by TNYoungblood

Can you elaborate on the formula Steve. Mine was alittle fat on the dyno(done in February) and is alittle lean out on the river in the summer time.
Thanks

how fat is fat on the dyno? what were the a/f numbers at WOT and do you have them for each cylinder or just from a collector?

And how are you determining that its lean in the summertime?

If it truly is lean, it could be due to the exhaust and/or fuel system in your boat, if you didn't tuen the engine with those exact parts on the dyno.

Originally Posted by TNYoungblood

No time slips but i can do everything else .. I had these carbs on a 468 and then put them on the 540 and took it to the dyno .. Dyno man said I was alittle on the fat side, witch I like, but we never pulled a plug to have a look .. I always liked to see alittle black on the back of the boat at the end of the day and noticed when I would go out it was clean so I pulled a few plugs after a pass and noticed they looked alittle lean .. I'm gonna go up a few jet sizes until i get the plugs looking better


FWIW
BBC 540 runnin on 93
2 QF 750s
Primary jets 72
Secondary jets 84
Power Valve 4.5

Boat runs great at mid RPM range and at WOT.. I'd just like to get a little fatter tune on it

black on the tansom is not necessarily and indicator that the engine is running fat at WOT. that's likely from idling or part throttle operation. And unless you are making a pass with brand new plugs and shutting the engine off immediately after and pull the plugs to look at them, you are not getting a proper plug reading. lots of guys mistake a sooty looking plug as the engine running fat when it really isn't because they've been driving all over the lake before pulling the plug to check it.