Side drafts VS down drafts
 

YES I know there is a thread EXACTLY like this in the archives. I read it and I have a question...

Down drafts make more peak HP than a side draft, and side drafts make more lower torque, basically from the length of the runners. This is the same concept as putting spacers below the carb to lower the torque curve.

Well I got a question... I ran a side draft before. I had both the wrap around, and a lake city manifold. The Lake City manifold was a short and stubby manifold that had the carb pointing towards the passenger fenderwell. I noticed this has more of a snappier response than the wrap around.

Question being... if there was a Weber 48IDA and a Weber 48DCOE with the Lake City manifold, would the DCOE make more peak power than the IDA simply because the manifold runner length is shorter?


EDIT: Archive thread in question:

https://www.rx7club.com/showthread.p...ght=side+draft

and for a second i was going to think i would tell you you needed to search, and that you of all people where being a hyporcrite....

but in regards to your question, i think it would help the torque, but i believe there is also a difference in the design of the carb and the way it flows that may play an important role as well.

Believe me I have searched. Most of what I have read was that the runner length is a good factor on when the torque and HP curve will show. That is why I am asking about if it is just the fact that the IDA puts out more HP than the DCOE regardless of runner length.

I have searched on multiple forums.


Also, it is hypocrite :)

I think the IDA will still out flow the DCOE all things being equal as you have stated. Maybe a webber expert like wacky can chime in with some proofs for us.

just on manifold design, a longer intake manifold will generally make optimum power lower in the revolutions, whereas a short runner length will make usually a few more units of power but at the peak end of the power band. A lot of manifold designs are meant to just look pretty at the cost of performance.

Case in point, look at the 787 4 rotor. Had variable length runners that got shorter as the rpms got higher. That way it was always making the best power it could.

As for the carbs themselves, the difference is just is how the fuel gets into the carburetor. The inside diameter is the same, so they will flow....the same! Gravity has little to do with anything since we are talking gases and the vacuum of the engine would negate any effects it would have.

Im working on a side draft style setup on my 12a. Fuel injected with a Atkins side draft manifold (much like the lake city one). As for the throttle body, im either going to use a Ford 5.9L throttle body or actually spend money on the TWM style ones.

Stu, check out the NA forum for all kinds of edutainment and enlightenment. Its focused on NA issues.

https://www.rx7club.com/naturally-aspirated-performance-forum-220/

The IDA is just really good at moving lots of fuel and air. The LC manifold does wondors for throttle response because it's short and has no bends. Even though the IDA has one 90* bend it still is a fantastic setup. And it's easier to spray carb cleaner & power foam down it's throat. Sidedraft does atomize fuel better than downdraft.

that was a typo, FTR however i wouldnt be surprised if i did spell it wrong.

:tonque: Just giving you a hard time