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I am a little confused and puzzled about the building of the ST4s.. The 2004 ST4s has a 996 motor in it, with the same power output of the 996 confused. I could not get a straight answer from the dealer because he was not sure how Ducati produced the ST4s.

It is my understanding that Ducati just pulled the 996 superbike motor off of the shelf and put it into the ST4s chassis. So basically all ST4s owners have a 996 motor in a relaxed chassis? Is this true?

I just had a custom map made for my PCIII with a great out put of 118 Horse and over 70lb of torque. And after looking at other 996's my ST4s is identical.

Can someone with a little more knowledge explain the building process of the ST4s.
 

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I think the cams are a little different. The 996 in the ST4s was a little better than the 996 if you read what some of the mags said. I think they basically advanced the intake cam a little?
 

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Exhaust cams are identical, intakes are same lift but 10 deg longer duration. The longer duration means more overlap and a slightly less responsive throttle down low but marginally stronger up top...1 maybe 2 ponies at best. Valve sizes are identical (36/30mm) as are gearbox and primary ratios.

The chassis is indeed slightly more relaxed with iirc 1/2 degree slacker rake and more offset resulting in something like 6mm greater trail. I believe the swingarm may also be slightly longer to maintain proper weight balance. Take care
 

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The 996 engine in the ST4s is a bit different than the Superbike 996.

They "lowered" (?) the head in the exhaust area to allow it to be tilted further forward in the chassis to help with weight distribution and to fit it into the ST frame.

This is why the ST4s 996 uses different cam belts than the Superbike 996.

-Bob
 

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The exhaust system on the ST4s is also better than the 996. There's less restriction with the ST4s exhaust and this gives the ST4s a few more ponies than the 996.
 

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Turbo said:
The exhaust system on the ST4s is also better than the 996. There's less restriction with the ST4s exhaust and this gives the ST4s a few more ponies than the 996.
I have read this as well. The exhaust pipes of the ST4s go pretty much straight back from the engine whereas those of the 996 bend a lot to reach up under the seat.
 

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"They "lowered" (?) the head in the exhaust area to allow it to be tilted further forward in the chassis to help with weight distribution and to fit it into the ST frame."

what does this mean?
thanks in advance
 

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acpdx said:
"They "lowered" (?) the head in the exhaust area to allow it to be tilted further forward in the chassis to help with weight distribution and to fit it into the ST frame."

what does this mean?
thanks in advance
I think it means that the Superbike 996 head is taller (thicker?) than the ST4s head. Which makes the ST4s engine shorter.

I found it mentioned here:

http://www.motorbikestoday.com/reviews/Articles/ducati_st4s.htm


-Bob
 

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Been Checking And The Heads Are Different Barrels Are The Same
 

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ST4s heads look angled towards the exhaust cam where the 996 heads are square across the top. This was true of the 916 engine in the ST4 as well. I also read the S4 Monsters and 02 748s use these same heads. Belt covers and cam belts from the two designs are not interchangeable.

The ST was built from the 851 SBK chassis by the same guy who designed the original Monster.
 

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ST4s Torquier?

Hello
I'm speaking mostly from hearsay and assumptions, so don't place much value in these statements/questions...

I thought the 4s motor had a slightly de-tuned valve timing. I.E. less overlap than the 996 motor, with, I thought, the same lift numbers. I thought this was done to enhance lower RPM torque curve.
The slightly smaller diameter throttle bodies also helped in this regard, by increasing air velocity at lower engine speeds, encouraging better mix and burn efficiency.
From what I've read elsewhere, the improved exhaust configuration actually allowed the above lower-engine speed mod's to work without compromising the higher-engine speed capabilities.
Therefore, the ST4s motor makes a stronger bottom (torque) due to it's valvetrain and fuel-injection mod's, and also makes incrementally stronger HP #'s due to it's more efficient exhaust.
Kinda makes the underseat exhaust thing seem a bit more "form" than "function" to me, but it does look pretty darn fast....

JMHO...
guido in Houston
 
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