here is a video on the subject i am not say it is the be all and end all of runner length theory and testing but it is the start of a conversation
https://www.youtube.com/watch?v=Eh4P8lvBuCU
https://www.youtube.com/watch?v=qSQSABXvr3A
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here is a video on the subject i am not say it is the be all and end all of runner length theory and testing but it is the start of a conversation
https://www.youtube.com/watch?v=Eh4P8lvBuCU
https://www.youtube.com/watch?v=qSQSABXvr3A
I am wondering for a while now what would happen if ours was shorter so you can acces the rear spark plugs....
Some lower torque and some higher hp would be good for the stock block...
Nice to see that you take the time to look deeper in to this topic, I appreciate it. As I wrote those points in the twin turbo topic I felt like this isn't easy to convince people as this starts to be the gray area of tuning.
But there is always some theory and physics behind engine tuning.
I can copy some of my writings from that other topic in here if these could get some discussion to start with.
"Air velocity creates pressure waves as intake valve closes it bounces from there back to plenum and from there back to valve, the key is to have right length runner so the wave arrives to the intake valve as it opens."
"Then for the optimum length of the runner also the intake cam duration plays a big role, for the stock cam standard manifold lenght is pretty close optimum, but if you have intake cams with longer duration the intake pulse have less time to travel back to intake valve. So again there you need shorter runners.
Runner diameter determines the pulse "power" smaller diameter works great in the low rpm range as it creates greater velocity to increase the pulse effect, but in the higher rpm:s small diameter is a restriction and larger diameter is needed."
"Runner pressure waves works with harmonics, sometimes short runner might work in the low rpm range and high rpm range but not in the middle. (First, second or even third harmonics, as how many times the wave bounces back and forward before the valve opens).
As said the harmonics work the same way still if we got boost pressure, only difference is that air molecules are packed tighter."
yep i am always open to leaning something new.
if somebody says something i dont agree with i will check the data sorces and consider all the option and revise what i thought was the truth and move on. Every day is a school day.
The moment you stop learning is the day you die.
it is a complicated topic, but it can be worked out and explained full with Maths/Physics.
which is why i was so impressed with a Normally aspirated system from one of the USA universities that had a continually variable runner length with an applicable trumpet on the end based on a rpm and load map. the ideas started flowing, but the fixed turbo requires a much greater consideration with a sealed chamber (plenum) with movable runner contained inside not too dissimilar to Porsche and the Vario ram system but that was with long or short, nothing in between.
it is an interesting topic.
Something i have heard recently from many different sources is "whatever a N/A engine will do, a forced induction engine will just do more of the same as long as the boost is constant and stable across the rev range. it will just lift the power and torque curve up in the numbers. which is completely logical and understandable. but it is not what we have all been told for the last god know how many years.
all hail the dissemination of knowledge.
Tuning a car is not a black art, it never has been. you have been told that it is, but it is not.
it is just Maths/Physics and this can be learnt and it can be taught.
It depends on how much would you cut it shorter.Quote:
Originally Posted by metaripley
This can be calculated if you got your engine displacement, intake cam duration (I believe that you should use 0.050" as the air is starting to move at about this lift not at advertised duration),
Then you need the rpm area where you want your peak hp to be. This is one calculator that i found from google: Calculator
But as always you should not take the results as THE right one, there are always so many variables that I think this is the guide line that gives you idea about the lenght of the runner.
Best results can be archieved when on the dyno and you have the capability to test different lenghts.
Sounds interesting study, do you have a link for it I might take a look.Quote:
Originally Posted by Davezj
Continuously variable length intake runner is indeed not easy to implement, that's why so many systems rely on only two different lengths. But yet again that one length might work great for RPM range of 1000-2500 not perfectly but enough sufficiently to provide boost for economy and performance.
Another topic that can be discussed could be the shape and radius of the "trumpet" or the plenum end of the runner, these also make an impressive differences to performance. Again mr. google founds many studies that compare different shapes and sizes. for exmple this
I am glad that I started my tuning hobby with N/A engine, there is all these little things that sums up and you can make power, it's not easy and you really can't make huge amount of power at the end.
With factory turbo engine most people are happy after turning up the boost, that's perfectly fine as I can assume that not everyone are interested that deeply about physics behind engine.
Yes that's about right, of course there comes these little things as more heat and certain restrictions at the exhaust and intake side because of that charger.Quote:
Originally Posted by Davezj
It's fun to hear that some people are talking about "putting a turbo to an N/A engine" and then thinking that how the magic is going to work because it didn't come with the turbo from the factory, this makes some confusion sometimes. /popcorn
At the end it's the same thing, it's an engine and you want more air in it.
log time coming but this is what i was think of.
https://www.youtube.com/watch?v=EPcpmSdip_0
https://www.youtube.com/watch?v=JMVioC2XGO0
https://www.youtube.com/watch?v=YZhSgwYs08k