Just Off The Dyno

[The Dan]

If the thing flows a bit better, flows more evenly and is better at equalising cylinder filling across all cylinders...doesnt it stand to reason that a "weaker" cylinder will not ping earlier then the "better" cylinders...maximising the effeciency of the engine?

Don't forget a turbo acts like a fuel pump. It only pushes air. It requires a restriction to create boost pressure. It is moreso the boost pressure combined with the flow of the turbo which determines volumetric efficiency. The smallest area the air must get through is the valve space. There is no 'weak' cylinder as they are not all on intake at the same or similar times. It is the turbo which must continue to push air once the valve opens and there is a pressure drop in the system. If the turbo fails to provide a volume of air suffiecient to fill all cylinders at once then it will not be able to keep up at high rpm, air speed is reduced and power drops. What the design of the plenum does is maximise the 'efficient' space that the turbo can store air before the valve opens. Go too big and you will suffer in the lower end of the rev range for torque but increase your max rpm potential....go too small and the inverse is true. Usually a good plenum size is around twice the capacity of the engine. Runner length also has a major role to play in choosing a plenum/intake manifold as you want to achieve maximum torque at a desired rpm. The longer the runners, the lower the rpm you will have your torque band....and the same applies for this as the plenum in that you don't want to go too far. Runner design is important in that if you just weld some pipe to a barrel, you won't need to put it on a dyno for me to tell you it's not going to be efficient. Instead, bell mouth runners inside the plenum that taper down to the inlet port of the cyliner head to increase air speed as it enters the cylinder head is the better option. Once again there are more factors that play here and also protrusion of the runners into the plenum, diameter of runners, plenum shape, throttle body size in comparison to plenum size and then all of the above compared to engine capacity and whether or not it's forced inducted or not.

As you can see there is much more then just size and shape.....it's not always a case of what looks good, works well. I'm not saying that the aforementioned plenum does not work....I have not seen it or inside it for that matter. Just the usual educate the masses and help them make their own decision saga. Yunno the one about the 'teach a man to fish'. lol

[Devils_Advocate21]

Nice work, but how do you fish? That makes sense though what you said dan. I dare say it would make a difference, but to actually compare the before and after would be a better scenario, and also to compare b and a for any car for that matter would give a much better proven result so we can accept closure on this matter. On that note more than one car would have to prove this statement whether nay or yay it does actually improve results by that much. I dare say that IF there were more people willing to actually go through with this and share results of before and after would be of most benefitial for all of us not alone the plazmaman plenum dealer.

Cheers A

[Roy]

Don't forget a turbo acts like a fuel pump. It only pushes air. It requires a restriction to create boost pressure. It is moreso the boost pressure combined with the flow of the turbo which determines volumetric efficiency. The smallest area the air must get through is the valve space. There is no 'weak' cylinder as they are not all on intake at the same or similar times. It is the turbo which must continue to push air once the valve opens and there is a pressure drop in the system. If the turbo fails to provide a volume of air suffiecient to fill all cylinders at once then it will not be able to keep up at high rpm, air speed is reduced and power drops. What the design of the plenum does is maximise the 'efficient' space that the turbo can store air before the valve opens. Go too big and you will suffer in the lower end of the rev range for torque but increase your max rpm potential....go too small and the inverse is true. Usually a good plenum size is around twice the capacity of the engine. Runner length also has a major role to play in choosing a plenum/intake manifold as you want to achieve maximum torque at a desired rpm. The longer the runners, the lower the rpm you will have your torque band....and the same applies for this as the plenum in that you don't want to go too far. Runner design is important in that if you just weld some pipe to a barrel, you won't need to put it on a dyno for me to tell you it's not going to be efficient. Instead, bell mouth runners inside the plenum that taper down to the inlet port of the cyliner head to increase air speed as it enters the cylinder head is the better option. Once again there are more factors that play here and also protrusion of the runners into the plenum, diameter of runners, plenum shape, throttle body size in comparison to plenum size and then all of the above compared to engine capacity and whether or not it's forced inducted or not.

As you can see there is much more then just size and shape.....it's not always a case of what looks good, works well. I'm not saying that the aforementioned plenum does not work....I have not seen it or inside it for that matter. Just the usual educate the masses and help them make their own decision saga. Yunno the one about the 'teach a man to fish'. lol

LOL...yeh all very good. You have read some texts on manifold desing...but none of what you have said is specific to the RB25 or manifold in question

Doesnt change the fact that if you pull the plugs on a std RB they are never the same...you are tuning based around the average of the air the cylinders are consuming and the fuel youre dumping in them. Even then you are only tuning based around the fuel coming out of all the cylinders. One cylinder will be detonating before the others...that limits the ignition/tune you can get into the engine.

You dont need an engine dyno and Motec logging individual cylinders (though speak to those that have set up their RBs on dynos with Motec and they do actually use the individual cylinder injector settings)...the plugs tell you that not all is right. Could also be the fact that cylinder 6 runs the hottest, could be the injector rail isnt equal for all cylinders. Could be the airflow in the manifolds is a compromise....and a better manifold specifically design for a performance application on RBs can help get around this problem

Anyway...i dont really care...need to do some numbers and see whether i should go Plazmaman or jsut go RB26 head

[WogsRus]

hay o got over 200 rwks at 12 psi and hit 217 rwKws at 14 psi, the more boost i had the harder the car went. LOL.