cock head

OK I know how a equal length manifold is better because the gases reach the turbo at the same time instead of two at a time. I would think that the quicker the gases travel to the turbo the better it would be, right? But some of the equal length manifolds are long like the first, second and fifth manifolds on this thread https://honda-tech.com/zerothread?id=364672. Don't get me wronge those are beautiful manfolds, and very effective but the runners are long, so it takes that much longer for the exhaust gases have to traves to the turbo blades, and a lot more curves to go through, and loses speed, right? But the seventh manifold in that thread has a lot less piping to travel to, and less turns, and seems all the runners are equal length, but the middle two have bends in them so that might be a factor, but that should be the best one?

I am not a expert in liquid dynamics or have a enginering degree (WORKING ON IT), or own a lab so this is all based on my common sence and little experience. I would really like it if some one could educate me, thank you.

bottlefedb18c1

i am tring to find the one to go with myself also

SEFIxCivic

I'm not any kind of expert or anything on exhaust design, but I think having longer runners to an extent is beneficial to the motor because it helps the motor breathe.

What I mean by that is that short runners cause a lot of backpressure between the manifold and head, and while this is good to spool the turbo, it causes contamination in the combustion chamber when exhaust gases backflow in. I believe this increased difficulty in expelling waste gases decreases a motors efficiency. I think this a major component in why the torque curve starts dropping at high boost in our motors.

Also, the longer runners in conjunction with a merge collector more effectively conserves exhaust energy. Instead of the exhaust pulses bumping into one another, they are gently routed into the turbine in a sequence.

Most quality equal length manifolds are also made of stainless steel. SS naturally insulates heat better than mild steel & possibly cast iron. This gives the turbine more available energy to do what we want, which is make power.

PrecisionH23a

up so geoff can answer this

cock head

Ok that makes sence about the back pressure, but for all race appliation where room is not a issue, a person would be better off with long runners with no bends?
I dont know if this makes sense but wouldnt it make sence if the gases were kept apart (in their own runners) untill they reach the turbo, because when all the gases meet in the mearger right before they enter the turbo; the gases "collide" with each other and, well get disturbed instead of being smooth, that make sence?

BudaKai

With a larger turbo running more boost you want the manifold to hodl enough volume for the exhaust gases to exit the cylinders, and push through the turbine. The larger the turbo the greater the air flow and the more power you're making, correct?
With this greater amount of flow you'll need to have more available volume for thr gases to expand into. With-out this greater volume you'll run into a brick wall where the pressure in the manifold is greater than the pressur in the charge piping and intake. Once this occurs you either need to do two things.
Run a larger turbo, which your really not solving the problem. You'll just
end up hitting the same wall down the road. Only this time you'll lose
a vast majority of your efficiency; due to back-pressure in the exhaust.
Run a larger smoother flowing exhaust manifold. You solve the problem,
and you are able to boost more with-out losing as much efficiency
with the same turbo.

The equal runners also speed up your exhaust gases; by offering ittle resistance. There's a lot more to it than that, but that is simplified explaination. Equal length will simple support more flow, or power. Whatever you wish to call it.

DefiantGSR

well said SEFI8LOxCivic. also, torque curve goes down as we put more boost b/c more boost equals higher temperatures. compressor efficiencies also play a role in temperatures. from what i've read what plays a major role in developing the manifold is wastegate and turbo positioning. since the oil return has only gravity to remove the oil from the turbo, the turbo is usually positioned so the oil return line is vertical.

As far as the wastegate is concerned, it is vital that exhaust gases be given an easy job of changing direction from the route toward the turbine to the bypass through the wastegate. If flow has any difficulty changing direction to the exit through the wastegate, boost control may simply disappear a la boost spike. so when you look at turbo manifolds such as the hytech, you can see that the exhaust gases can easily enter the wastegate. you dont want exhaust gases to turn 90 degrees to get to the wastegate b/c it wont happen especially at the speed that they are travelling. you want equal or better distribution of exhaust gases to the wategate. pictures will easily explain what i said.




[Modified by DefiantGSR, 9:55 PM 12/31/2002]