^ NOT really, only two differences that matter, ONE with a turbo your intake air temps will be lower, and TWO, cam timing and or duration play a larger role.

Case in point, REF Brian (speed racer) and these books ,

a supercharged motor will behave more like a N\A motor as in there is no restriction on the exhaust ports that a turbo will cause, with a turbo motor, having a *stock* like cam timing will effectively "blow" your intake air out of the combustion chamber, however, with a supercharger, it CAN help the savaging effect of the motor, depending on

A: boot presser
B: combustion chamber geometry
C: intake runner velocity VS volume.



Moving on,

The command air fuel ratio, or if you will, base AFR is the number the motor is shooting for, with a supercharged motor, as with a turbo charged motor, a richer burn is desired to help get elevate detonation, or at least help prevent it, HOWEVER a leading cause of this is HEAT, witch is why leaner can be done with a turbo, but you guys with turbo’s usually run more boost so we are back to step one. The 2ed leading cause of detonation is combustion chamber geometry, we will call them hot spots, in easy terms, its any sharp edge in side of the chamber, auto manufactures use these "squish pads" to aide in compression, that in turn helps the efficiently of the motor, but also can cause detonation.

An ecotec motor has a relatively good combustion chamber design, and high velocity intake runners, (I’m guessing this is why GM makes AJT cam gears for them.) if it where mine, I would start with the stock GM tune and go from there, but no way in hell would I go leaner. Again I like to be safe.



Chris



'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08

Above 12.2 i notice knock and other than keeping the AFR below 12 the only other way to eliminate it was to lower timing which isnt something you want to do, id rather run it richer and be able to advance a few degrees



1989 Turbo Trans Am #82, 2007 Cobalt SS G85

Taesch... actually they do function differently and they ARE tuned differently... being that a turbo motor thrives off of heat and a supercharged motor has no benefit from it...

A supercharged motor you treat much like N/A... a nice chunk of advance, decent air fuel ratios... you don't need to worry about driving your compressor because the belts are taking care of it... your main enemy with the roots setup IS intake heat... so you have to deal with that unfortunately.

With a turbo motor, heat is your friend... exhaust heat. Since the turbo is driven by exhaust pulses you want to get velocity up and heat up to drive the turbo... intake air temps of course change as you said, but CFM's are way different... which is why generally a turbo motor has a higher BSFC. For the most part, there are many methods in tuning you can use to help spool a turbo... and I have to say DSM guys have a lot of neat little things they do to help their cars run a lot better, especially during spool time.

I would assemble a turbocharged motor completely differently from a supercharged one. Different compression ratio, different cam design, different coatings... for a supercharged motor I would run higher compression, lower boost and go about it that way. A turbo motor would be different, since I would personally want to raise temps to drive the turbo.

Anyway with that all said, - as I said - you can't just pick a magical AFR out of the air. Depending on the engine design and form of power adder the afr and timing maps change...

Either way I think we're agreeing to disagree on this one, just saying things in a different way. Overall if I had to build 2 motors side by side, one s/c and one t/c and tune them... they're be handled quite differently.

Rodimus - why do you feel you don't want to lower timing at all? Advancing timing isn't the only way to gain power in a motor - if you're pinging it means your combustion chambers are too hot, throwing fuel at it works but so does pulling a bit of timing in the right spots... Keep in mind GM's timing maps for the LD9 S/C kit are designed for their stock pulley, with maybe a bit more - as well as emissions. If you notice after a certain KPA the timing chart just flatlines right out almost, as if they just said "Eh this'll do for 180 kpa onwards, they'll never see that KPA anyway"...

-Chris-



-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...