Fiat Cam flow analysis - Another by Terry

[bruce]

Take a look at some of these. There's a lot of tabs. Be careful if making
any changes!

Applicable Notes:


The FiatCam Flow Analysis contains a bunch of analyses. Looks at some of my early flow bench development on the 2-liter Twin Cam, examines cam and valve relationships, rod ratios and effects of piston velocity, and where max piston velocity occurs, overlap events, throat areas vs. curtain (recently posted as "window" area) flow areas, and plots for just about everything that I looked at. Some of the calcs may be a little cumbersome
in how they're laid out, but done to simplify and allow checking fairly easily. Cites all referenced works, with applicable formulas. A ton to be learned from this one, with many applications to what others who read this Forum are after.


This file is to large to attach so I made it a seperate download:

[larrycavan]

There's a lot of data there, that's for sure. Thanks Terry for sharing that information.

On a side note and with all due respect, the head appears to be severely lacking in the CFM department considering the size of the intake valve. I've seen similar CFM with 37.5mm intakes in ported Kaw 2V heads that would be comparable to the stock Fiat head flow values.



Larry C

[2T4T]

Hello Bruce ,
Best wishes from France for this new year. This site has no equivalent at home and in Europe and I am happy to read you every day.
Lot of formulas seems to come from SAE book PT-53 : Design ... engines.
I am trying to test engines using the Honda info. You can find an Excel file (and Gnumeric format for those wich do not own Excel) on my web site (only in french) :. See download section : Remplissage Honda.zip

Did you dynoed your engine ? I am using an Italian wave simulator (like Dynomation) and I tested some engines from various SAE papers. I am looking other engines power curve from accurate inputs to check if Honda rules applied well or not.
I choosed to show the motorcycle YZ426 due to huge difference in power curve shape using different exhaust pipes :
Base : LT=1025mm d=38mm
P1 wide power band : LT=990mm d=64mm (!)
P2 high rev , max power : LT=270mm d=39mm
Honda assume that from a "supercharging" index Z that IVC will match a value depending of inlet length , diameter and Cd.
For a same engine , the derivated info calculated (Z , mean Cd= Cim) are not identical and show the limit of these expectations.
This helped me also to understand how engine parameters interact between each others.
But other details can be extracted such as inlet tuning frequencies locations.
If interested , I will translate it
Regards
Alain

[2T4T]

Hello ,
File translated. Need some others to complete the job.
R.

[2T4T]

[color=#000000]Hello Bruce ,
I added the prof Blair calculation for Time-Area with your fiat data. GP Blair divide inlet and exhaust valve lift in periods :
- inlet :
overlap = from opening to TDC
pumping = TDC to BDC
ramming = BDC to closure (air mass inertia)
- exhaust :
blowdown = opening to BDC
pumping = BDC to TDC
overlap = from opening to TDC
Time-Area for each phase is a calculation base on valve area , swept volume ; rpm and can be analysed to BMEP level on the engine.
In my file , each "S area" require manual adjustement each other valve lift timing and to commun angle (180,360 or 540

[Terry_Zakis]

(Thank you Bruce for posting the additional files I sent in.)

Thank You Alain,

I picked up a copy of the Blair book a few years ago, and was just blown away by it. Incredible. No doubt why the Virtual 4-Stroke programs are so expensive!

Thanks again for your input.

Terry T.