Supercharged Blackjack Avion

[andrewc]

Tonight I programmed both the initial normal advance curve and then the second MAP vacuum advance / boost retard curve - all from my phone via Bluetooth.

The MAP curve is pretty simple, with 4 points between 0 kPa and 100kPa for the vacuum part and a further 5 points at 20kPa intervals between 100kPa and 200kPa for the boost part. All pressures are absolute and you enter the amount of retard you want at each point. I'm starting using the Alan Allard rule of thumb of 1.5 degrees per 1psi of boost. It's fairly simplistic, but I keep reminding myself it's a lot more sophisticated than a K3 Magnette or a Blower Bentley.

Not far off seeing if it runs now!

[Geoff Ryall-Harvey]

Programming the ignition on your phone using bluetooth sounds pretty sophisticated to me!! Getting closer now...

[andrewc]

Yesterday it started and ran. But only for 10 seconds, as I had to shut off due to a monumental amount of fuel coming out of the fuel overflow on the SU HIF38 carb. So no photo's/video taken and no chance to check how much boost was being generated. We now have a brief interlude (hopefully) whilst the carburettor is sorted.

But it ran, which must mean some air/fuel mixture got through the supercharger to the combustion chambers, and we must have had some sparks at roughly the right time in the 4 stroke cycle.

We're nearly there

[andrewc]

We're still not quite there. A "new old stock" HIF38 carb off Ebay was my fix for the fuel leak. I swapped the needle and spring over from the leaky carb, and it ran. However, it wouldn't rev above about 1500rpm. After much head scratching I eventually realised that the wire reinforced hose connecting the carb to the supercharger (visible in the previous photo's) had been collapsed - I'm assuming by the suction created by the supercharger. Photo below shows what I mean. I'm taking this as encouraging evidence of the supercharger doing something more than just making a noise.

I'm making up a new bracket which moves the carb inboard and upwards, allowing a much straighter run with some much thicker walled wire reinforced silicone hose - some of it is visible in the background of the latest photo. A quick trial with the new bracket g-clamped into place revealed the new solution doesn't collapse and I saw 3000rpm.

I'm away with work for a few days, so I'll have to wait until next weekend to see if this is the final modification required - will it get a test run on National Drive it Day?

[Geoff Ryall-Harvey]

Well done. Pioneering work.

[hutchii]

I've just been looking for suitable flexible hose for connecting my SU manifold to the inlet port stubs, and noted on the Roose Motorsport Performance listing for Silicone hose that it's not suitable (to use their words) "for diesel or petrol passage". I assume that this refers to fuels in a liquid form but, has anybody had problems using it for fuel air mix? Any pictures I've seen of non metalic manifold links, including Andrews' pipework, appear to be using Silicone hoses.

[QFAD]

Hutchil,

I have seen it used many times as the hose supplying air to the carb, but not as a joiner between the carb and the inlet manifold. If no one on the forum can confirm suitability, I suggest you give one of the reputable suppliers a call to confirm - they may offer an alternative hose type.

Steve

[andrewc]

Not having my own TIG set, silicone hoses is the quickest (only?) way to get it all running and see if it all works.

Anyway, momentous news for today is that I've been for a test drive and seen positive boost for the first time.

Last week end was a bit depressing, as I couldn't get it to idle below about 3000rpm. It must have been caused by one or more vacuum leaks, as after a cooling off period and a bit of thought I re-tightened all the hoses/manifold joints etc. yesterday and it now idles OK.

It pinked on the short test drive, so I've retarded the ignition a bit using the 123 ignition App, and given it a 1/4 turn of mixture on the SU as a precaution. Its started raining now so no chance to see if this has worked.

Link below to a short video of it running in the garage before the test drive

[https://www.youtube.com/watch?v=uT9WJadSP28]

[Geoff Ryall-Harvey]

Denom Tweeks sell Samco silicon hose for this purpose. Given the way that the hose gets deformed, I wonder whether you might be better using stainless pipe as centre sections for the pipes and using pieces of the existing hose at each end as joiners? You wouldn't then need to weld flanges on to the ends. As well as straight sections you can get short mandrel bens of various angles.

You're really close now...

[Geoff Ryall-Harvey]

How did it drive BTW???