Inlet port length

[Os7213]

Hi everyone

I am building a Toyota 4age 16v 1600cc and for a few months now I'm studying intake manifold and inlet ports length.
I have found an interesting article about intake/port length which can be "calculate" with desired rpm versus cam timing ABDC:



Basically the intake length "calculated" is from the middle of the inlet valve to the end of the inlet trumpet.

I have done the "math" for my particular cams setup 2x 272deg 9mm lift timed at 64 ABDC with peak power band between 8000-8500rpm. So if I follow the diagram the inlet lenght from middle of the valve to the end of the inlets trumpets should be aprox. 8.5 inch

Unfortunatly I dont think inlet length can be calculated with precision with cam timing and desired rpm.

What do you think about that? Do you have another theory or fact about intake length?

Thanks
Hugo

[Guy Croft]

Hugo, interesting but will have to wait till I get time to study it.

Certainly, as you remark, predicting inlet and ex lengths is a job for top-level software and even then it takes all day to work it out to a level of accuracy that is any use...

In the meantime I don't go with your cam timing 'timed at 64 ABDC'

I suggest you download the attached cam timing diagram (it's Excel) and have a play with it. It's 'read-only', right click and save-target-as.

GC

[Os7213]

Hi Mr.Croft

No problem for the waiting time! patience and knowledge are the keys

Thanks a lot for the Excel document really helpfull.
Also for the timing you suggest I work a little bit more on it and I have figured this chart:

http://www.sendspace.com/file/innrn4

With a timing at 71 ABDC. I really dont want to bother you with this but if you don't approve the timing your advises are appreciated.

And to return to the orignal topic I have forget to mention that I will change injectors location. I have not calculate the exact position yet but I will put them outside head ports.

I think the "best" injectors position is outside trumpets but im almost sure than can alter air-flow but I have no infos to look at. The second option can be the modification of the trumpets to fit the injectors.
Also do you think injectors relocations can change the equation of a calculated intake lenght?

Thanks
Hugo

[Guy Croft]

Hugo, hi

well done for using the chart I sent.

You should quote FL (full lift) position when referring to cam timing - in your case 114 deg inlet and ex - not valve closure (71ABDC), OK?

In other words 'my cams are cams timed at FL 114/114'

More later,

GC

[Os7213]

Hi Guy

I have quote at valve closure ABDC reffering at the inlet lenght diagram.
I use it even if it not accurate just to give me a basic and non-calculate lenght of the intake. I forgot to specify it in my previous post.

Next time I will follow your advises and quote with total cams timing.

Thank for your time and good infos
Hugo