all testing was done on a 1.8L honda. I know its OT, but there is some good tech!!

short runner bottom mount:

http://www.full-race.com/catalog/pro...products_id=40

VS.

long runner top mount:

http://www.full-race.com/catalog/pro...roducts_id=317



Trian (one of the engineers who hangs out here) is doing his master's thesis right now on exhaust manifold design. We are working hard and documenting a number of different variables in manifold design.


HP datalogger



top mount testi-fold



bottom mount testi-fold


Jeff Evans already graduated, hates college and probably wont go to grad school. So he did a much simpler test:

GT30R top mt vs bottom mt



huge spool & tq gains, the top mt torque line eats the bottom mt hp line as the turbo spools


GT35R top mt vs bottom mt




again, significant gains to be found most everywhere, including faster spool despite the longer runner length.

 

nice comparison! any plans for a topmount for the evo?

 

innnteresting, tho am I the only one that's having a hard time reading and interpretting the data? Which one is top mt and which one is bottom? What are the different lengths?

 

well, obviously the better curve is the top mount since he says it eats the bottom mount alive.

get it?

 

This is interesting data, but I would like a little more information, if possible.

Are we to assume that this is exactly the same car with the same mods, boost levels & fuel. Same day, same dyno? Any tuning with the new headers?

Also, I would like to hear your thoughts on specifically why the the longer header peforms better.

I could be incorrect, but it appears that on the 35R test the differences are not as great until you reach the higher rpms. Is this due to the amount of boost you are running on this specific test?

Also, is there a "ideal" runner length and what specific variables determine this?

How much does total displacement, head design, fuel, exhaust and boost levels affect the ideal runner length for street driving?

 

Nice info Geoff,after reading some books:

Scientific design of exhaust and intake system (Smith and Morrison)

It seems to me that my engine (hence abit stroked 2,2L) must kind of use ~ 44-46mm runners and would be 8-900mm long (not possible in an evo engine bay)

So my question is have you tried to "use" such a long runners and what is your conclushion of it.

 

Something else you can infer from that book is that there is more than one scavenging wave. You can use the second wave for scavenging during overlap and, though not as effective as the first, it does not require nearly as much runner length.

You guys should make a WRX header. The pre-turbo exhaust length is long enough to pulse-tune to the first scavenging wave at high RPM with a 4-1 header, and in the mid-range RPM with a 4-2-1 header.

Edit: also, have you considered a 4-2-1 header for the Honda application? It does not need nearly as much runner length to pulse-tune for a given RPM because, as you know, the effective "stopped length" delays the scavenging wave.

 

very interesting!

 

Any news on this one,Geoff?

 

Thats pretty cool. Im headed back to school in the fall, targeting the same basic ideas behind what I want to accomplish in the future. Cool to see others involved in stuff like this.

Just the same, the super street manifold for the Evo seems of fairly long runner design....

Any plans to reinvent the wheel here? The manifold seems serious when it comes to overall performance, i dont see what would be necessary to improve on it.

 

I would like to know the anwer to this question also. Thanks Geoff!

 

Bump for updates on this!