Tuesday, 9 August 2011

Gas Flowing

Gas flowing, porting, cylinder head tuning, whatever you want to call it , it's a critical part of extracting power from an engine.
  After a couple of disasters letting others tune our heads Steelcraft racing http://www.steelcraft.biz/ decided the best thing to get a job done well is do it yourself. The basic theory is simple, get the most amount of gas possible to pass through the port, past the valve guide and valve and into the cylinder, and at the other end out through the exhaust port, OK its not that simple, factors like turbulence and swirl complicate matters but this is the Janet and John version. The problem is, if you are relatively inexperienced, how do you know that what you are doing  improves the flow?
  The answer is a flow bench. A device used to measure the amount of gas that can flow at any given valve lift. So we looked into buying one. We had a couple of quotes and after getting back up of the floor decided the only option was to build our own. We got hold of some plans and and spoke to a very clever friend by the name of David Holmes about some software. Thus we began the build. Again we needed some help (thanks Les) and had the wooden cabinet built
The cabinet with inlet and outlet valves made from stainless bowls from a pound shop

Then we needed some fans, so a trawl through the supermarket special offers gave us five vacuum cleaners for less than £100. They were duly stripped giving us the suckers/blowers we needed

Vacuum motors fitted
The other parts were assembled and fitted, it was painted a nasty blue colour, because we had some in the workshop and finally the vertical and inclined manometers were added.

I won't go into detail about how it works or the other details of the build, it's all out there on the interweb if you're interested, enough to say that we can now measure the inlet and exhaust flow of a head at any given valve lift.
 It soon proved it's value as improved gas flow from porting could now be measured.

Ducati head with Gardener carb being tested

Measuring the flow at 28" of pressure
In the photo above you can see the bolt used to lift the valve in 0.050" increments. Measurements are taken from 0.050" to max valve lift, we usually allow for 0.450" on Ducati heads  as most cams lift a little less than this. From this via a clever bit of software we can produce a graph showing flow in cubic feet per minute (CFM).

Typical flow graph for a 250 Ducati

The pink line shows the flow before porting and the and the blue line after. The X axis shows valve lift and the Y axis CFM The shots below show more detail of flow rates before and after average flow is shown in the bottom right corner. This example is of a head previously flowed by someone else which we have improved (we hope) and will soon be back use back in use at UK race meetings

Before porting

After porting
What it's really all about is more horse power

Ducati head part ported

The head above is part ported, the three angle seat has been cut and basic porting work is complete on the inlet

Aermacchi head  after porting

This head is ready to go, the port is polished and the guide has been flowed. Valves also need to be flowed to finish the job.

   Steelcraft racing can now offer this service to the public, porting starts at around £200 + vat depending on spec, contact details can be found by visiting http://www.steelcraft.biz/

                A famous racing saying goes "Speed costs money, how fast do you want to go?"

1 comment:

  1. hi nice work
    i did bild flowbench to and ended with car parts
    i did use opel corsa/agila 1.0l airflow sensor
    and map sensor + watercolom

    good luck greets wilco1v