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One I forgot to upload at the weekend - it'll be a worse view still when the body's mounted, as you're looking through a letterbox with your post sat in the middle 
The firewall that'll be built into the body, will have what's called a doghouse to encase the back of the blower and injector - called that as it's pretty much an upside down dog house.
To explain the steering wheel, the centre mouted plate has some holes visible, one is for the air shifter button, I believe the other two had a function for other buttons in a previous life - namely as where a switch was located for a manual high speed lean out of the fuel system at the top end.
Ordinarily you feed these engines as much fuel as you can find, what you encounter though is the efficiency / output curves of the fuel pump and supercharger aren't the same. The supercharger tends to become less efficient at higher speeds, and with the fuel volume being based on engine speed, can only increase with engine rpm (to its dictated fuel flow limit in accordance with the rules). A high speed lean out takes fuel away from the engine to maintain or alter the fuel air mixture. These are normally pressure induced with a poppet valve - at a certain fuel pressure, it bypasses fuel back to the tank rather than through the barrel valve into the engine.
The advantage of a manual high speed is it allows the driver to do it whenever they like; normally after you've slammed it into high gear and the engine rpm drops, you might take fuel away to bring the engine rpm back up. This is over the course of about a second, roughly 4.0 seconds into a run, having changed gear at around the 3.0-3.5 second mark.
In the Nostalgia Funny Car rules, a 21.0 gallon pump is quite small, meaning you aren't producing enough fuel to actively be wanting to take any of it away on a run, unless you have a brand new blower with an inlet shoe that helps it stay on song at the top end. In this instance, it's just a regular race spec job, so every drop of glorious nitromethane goes through the engine .
Back in the 70's when you were allowed to use innovation and different approaches, there were all manner of weird and wonderful ways to play with the fuel system on a run. Since you don't use the clutch pedal on a run, one very clever chap devised a rocker pedal that with some heel or toe action could either fatten up or lean the fuel system out at any point. Quite novel and it didn't really catch on, in that form at least. Years later when clutch and fuel timers in big show Top Fuel and Funny Car came in, the ability to control fuel volume at a set point in a run became a numbers game, predetermined via computer.
In other news, the tin work is back from anodising (I wish I'd remembered the steering wheel needed 'un-golding'!). A nice dark green, photos soon when it's back in the car and fettled a little more. |
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Author: Chevyonfuel
Author
24-11-2019 22:34:10
