Can anyone elaborate about the use of long or short runner manifolds other than to keep or delete the airpump or other parts on the engine.


What route to go to affect spool up, top end / low end power....

thx

 

short runners are good for higher rpm use, while longer runners are good lower rpms..
from my understanding..

 

Long runners will help spool.

It's not as simple as saying short runners for high rpm and long runners for low rpm.
An proper header need a specific length according to the application..
There's many variables involved.

Let's take a Small block chevy as an example.
One engine has a rpm range of lets say 5500~9000
This engine will probably need a header with 26~28" headers.

The same engine with a rpm range of 3500~6500
would probably need a header with 32~34" headers..

Now another example would be Formula 1..
There upwards of 19,000 rpms..
Their headers don't look to have short runners do they?

 

Are we talking about intake or exhaust runners?

 

longer exhaust runners seem to be what top engineers are doing.

 

i was assuming intake....

 

Turbo BEST is short direct and low pressure losses.

Look and learn





Exhaust tuning theory and lengths don't hold true on turbo machinery, ANY loss of heat and extra pressure loss and thus energy loss has a negative effect on turbocharged cars....... the only time "horse **** manifolds" benefit is when you don't have room to fit an efficient designed ideal short runner manifold.

 

So... A-Spec's long runner don't help spool at all? The whole "matching up exhaust pulses into a divided inlet using long runners for maximum spool" is all hogwash?

 

Long runner exhaust manifold's are great for Drag Racing. They help you keep you in "boost" between shifts. From my standpoint short runner exhaust manifold's are where you see a quicker spool up assist. If you're looking at a short runner manifold you're more than likely a highway racer...

 

^ Divided turbine housings and equal lengths to allow evenly timed pulses help all the time, they also lower turbine inlet pressure over single entry set up's.... horse **** lengths do not, they impose more pressure loss and more heat loss = inferior turbine efficiency and response.

All of the fastest rotary track cars in Japan ALL use short divided pulse manifolds like the one I pictured, they do run circles around any other turbo rotary circuit cars last time I checked two are amongst the fastest outright superlap specification vehicles on earth so the comment of street, highway racer is pretty lame but also totally wrong as well., it is the nirvana for rotary exhaust manifolds, equal, divided, and short as possible without compromising flow is the only caveat here (as in my original post, the ONLY time you ever want to do the inferior long type on a turbo car is if short is restrictive *very rare on a FD3S and normal turbo charger size*.

You can read some theory from Mazda themselves and also Garret turbo engineers if you wont believe and internet hobo like me http://foxed.ca/RX-7/SAE%20papers/New-tech90-1-6.pdf

 

So what are the possible benefits of the a-spec long runner manifold?

In an autocrossing environment, what would be the optimal spool manifold?

The only reason I am asking these questions is because I am about to send my money to A-Spec. However, I a=want the fastest spool possible as the car will be use for autocross.

 

Sean is not making the long runner manifold anymore(I think he said he would on special request though, not sure). Check the "New Stuff For 09" thread in the A-spec vendor section.

 

Some good reading.

https://www.rx7club.com/showthread.p...=header+length

 

YEP !!! short runner here !!!!

 

Nice exhaust backpressure pickup .

 

what is that? ^^

 

A pressure sensor for the exhaust. It reads pressure in the header between the motor and turbo (backpressure).

 

Thank you for taking the time out of your busy schedule to post useless and nonfactual information about turbo charger exhaust design in the community. I see that you have only half the amount of post as I do, so I understand your a novice . I would like to inform you that it is not fair to the community to post garbage, and secondly to use profanity when referring to engines is unbecoming. I can clearly see your lack of knowledge on the subject, please not the Red Bull Racing Plane. Note! Length is no substitute when it come to the bedroom or to turbo manifold design.

 

JEROME!

Any Mechanical Engineer, who knows something *UNLIKE YOURSELF!!!!*

Will tell you exhaust tuning theory does not apply to turbocharged machinery!!! I strongly suggest you get some basic education on this topic before blessing me with your dribble again

Post total does not equal knowledge, however research, education, and results does when you equal what I know feel free to open up your hole and pass wind again

Anyone in doubt, please go refer to any credible source and you will find that what I say as always is correct, factual, and backed up by the highest minds at the cutting edge of technology.

Do not confuse yourself with packaging constraints (as I outlined) and think you are correct in your view when you dont even understand what your talking about

You only need to look at F1 cars to see that heat and turbine efficiency take #1 precedents over a FALSE misunderstanding of "pulse tuning" for turbo machinery....... the concept DOES NOT EXIST in reality, but it does in some peoples minds so do UFO's and the Devil LOL !!!

 

https://www.rx7club.com/showthread.p...+length&page=5

RXHeaven WA, so the people in this thread are wrong too?

Plus, BDC went to the shorter manifold due to the long runners not being very compatible with a v mount setup.


And your comparison to F1 cars is flawed. They run more than double our redline.

 

is that picture of your engine? who's manifold is that?

 

Thats an HKS FD Manifold, and RX-Heaven is correct about the turbo manifolds...

 

Short manifolds .the way to go.

But their is more to a manifold then just runner length. Pipe size makes a difference as well.
I am no engineer but using same turbo, same pipe size, shorter manifold spool much faster.(not what someone told me, what i have found on same car).

RXHEAVEN_WA, you seem alot like rice racing. For a second in that post, it sounded like peter.....

 

It is rice racing. RXHEAVEN_WA gave him his account.

The original RXHEAVEN_WA wouldn't even know what a exhasut manfold is. :P

 

nah man it's Luke, I love drifting, rice just answers my technical questions when I have them