[NomadTW]

w/ the continuation of templar's S/C kit... i was thinking

all the numbers given are for the 2.5 basically,

my question is the difference in the engine size is relatively large when it comes down to it...

now the S/C on the RS will produce an estimated 6 psi at redline on the 2.5

now that's based on the CFM that the charger puts out, and the volume of the engine....

now w/ the smaller engine will the pressure increase because it still flows the same CFM or will the pressure stay the same and the CFM go down?

also will power is directly prop. to the amount of fuel/air burned in an amount of time,

now if the CFM of air going into the engine say 2000 (again, just a number) remains the same, and the amount of fuel that is reacted to that same amount of air is the same, won't the 2.2 and 2.5 both end up w/ a total final HP of the same amount?

225 which makes the 2.5 gain 80 hp, but the 2.2 gain 100hp...

this is theoretical, and if my theory's are unfounded plz let me know
also i'm excluding things like comp ratio, and exhaust layouts, and other outside factors...

 

[RalliTek]

It's good to see you thinking for yourself.
The pressure will determine how much air is in a volume.
The volume is changed so the power would not be the same.
You would have to run more PSI on a smaller engine to make the same power. Which is what will happen if you used the same pulley size as the 2.5. The PSI will rise and you will have to tune it much differently. Will it make the same power, if you tuned it properly, mechanically and your timing and fuel you could make the same power, it would just be harder to do because the boost is so increased you have to worry about detonation.

 

[5252]

woohoo good posts!

 

[NomadTW]

i am getting much more into this forced induction thing
the longer it sits here, and the more commited i become the more i think about it, and the more i think about it the more questions arise and i need answers to further my knowledge

now i guess my next question is for templar or someone else working on the dnt S/C...

but
when they make the 2.2L version, i figure they won't use a different pulley... because he's having to fab it from scratch anyway. so the question is is how differently will the afc controler need to be adjusted, will it be an easy thing to notice/change?
or will it be a pita?

 

[Templar]

Hey,

Wow, looks like this stuff has been weighing on your mind as much as it weighs on mine.

First to nip this issue in the bud, the 2.2 will be using the next smaller size unit in the Rotrex line. The SP30-94, that will be used on the 2.5 kits is for use on engines of 2.5-4.5 litres.

However, in response to your theories, the 2.5 liter kit would still produce more horsepower in the end if the two were using the same compressor and pulley. But the gap between the two will probably decrease somewhat.

There are formulas for determining te airflow of an engine N/A and what kind of airflow it needs to make a certain pressure ratio (ie boost). I have these formulas in a reference, and I can work them out on here sometime if you really want me too. Personally, I would rather not go through that mathmatic hell again right now.

Suffice to say that the .3 liters of displacement difference would allow for slightly more pressure to build in the combustion chamber on the smaller engine, but the higher compression ratio of the larger engine would make up for part of that as well.

Your thinking is along the correct track though. If you really want to get into this algebraic world a little more for your own understanding, I recommend picking up Corky Bell's new book "Supercharged." It is excellent and contains all the formulas and theories that are necessary.