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Discussion Starter #1
I'll appologize in advance since I'm sure this has been discussed before, but an hour of searching didn't uncover the answers to my questions.

I have a stock '03. ST4s ABS and want to core the exhaust to get a little more sound. I think I'm already running a little lean judging from the plugs, and I'm afraid opening up the exhaust will only make it worse.

I thought I had read somewhere that the ECU could be adusted by turning a screw, but after searching the site it seems that maybe that's only on older versions. Can anyone confirm? Would the dealer be able to make some adustments if I'm too cheap to buy a VDST?

At any rate, does anyone have any experience with how much leaner the bike might run with the exhaust opened up a bit? Am I asking for trouble by making mods without adjusting the ECU?

Thanks
 

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The ST is actually very tolerant of aftermarket pipes while not having the DP ECU. You will still want to enrich the mixture to prevent leaning out at higher speed, however.

My understanding is that all of the 5.9 ECU's can have the mixture trim adjusted by the software, and there is no physical screw since the 16M CPUs.

I originally had this done on my '04, since when I bought the bike, there was no DP ECU for that model yet. I later added the ECU.

Another option is getting the stock ECU re-flashed by Motowheels or similar. The problem there is finding an appropriate map.
 

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ECU trim adjustment

Hello
I, too, have an '03 ST4s ABS and I had the stock ECU adjusted on the dyno at AMS in Alvarado, TX some years ago. They advised me not to go with the DP unit (that was my intention) and they completely transformed my bike in about 30-40 minutes of dyno tuning.
It is now the most responsive, smooth, and predictable motor you could imagine. Low speed running really shines!
Picked up both torque and HP across the chart.
I had just added the DP airbox mod and Arrow exhaust cans prior to the adjustment.

Find a good dealer with a dyno and some patience and go for it!
 
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