[Dessertrunner]

Okay I plane to throw some ideas out for discussion and would like to hear a bit of feed back,
As everyone is aware I have been working on roller throttles and Matt has also installed a set of IDTB ( he said the car goes like a stung cat), also I got a bunch flow bench work done. All this has confused me which mean its all running around in my brain till I sort it out.

- Harvey has always said that on the exhaust side you need a pipe coming off, a head with out a exhaust won't work as well. In the past I was convinced he was wrong but good manours stopped me saying so. Now I am 100% convinced he is right.
- Over the years you read about how people redo the intake on the head to get maxium flow and expect it to make a big difference. I am convinced that is a wrong assumption UNLESS.
- People talked about how long the intake ram pipe has to be eg, longer for low revs, shorter for high rev, its suppose to do with harmonics.
- Mark suggested on my roller throttles to go back to a 40mm inlet size instead of the current 45mm the SVX have standard now. (common sense would tell you that is a really stupid idea) BUT HE IS RIGHT.

Lets look at the intake, I fully understand the harmonic (shock waves) have a part to play but I would like to start on the simple steps first.
Here goes, when the intake valve opens the pistion is roughly on the down stroke so air and fuel runs in due to the vacum. In simple terms the amount of air that fills the chamber is directly related to the sucking pressure less the drag (restriction) on the intake parth. So reduce the restriction (port the head for example) and you will get more power. As the piston reaches the bottom of the stroke suction decreases so airflow reduces. If a engine has a long intake part then it needs to be as large as possiable to get the maxium flow into the head.

So why does IDTB get such a bang for there buck if it all about in airflow restriction. Why did Mark think cutting the intake size was the right thing to do. I think the answer lays with the movment of air. With a narrower dia intake pipe but short we may have the same sort of restriction when the intake valve first opens but when the piston is no longer suction the air in the intake pipe is at such a high volicity that in continues to pump into the cyclinder under PRESSURE not vacum. Simple rule is that air under pressure contains more fuel and Oxygen then when its under vacum. The flip side to this is that you can delay the closing of the intake valve for a longer time when its on the up stoke due to the air raming against it.
Back to harmonics/sound waves, I would suggest that the issue is closing the valve before the air/pressure wave gets back out the intake. In other words lower revs mean slower air velocity in the intake for a given size, the soluation is to either lengthen the parth (Ram Pipe) and or reduce the intake diameter.

So team jump in, feel free to disagree with me I won't ake it personally.
Have a great day.
Tony