Thursday, March 3, 2011
If it ain't broke, don't fix it!
The Giles G-200 was going well last year. No squawks, all sorted, going really well. I flew the NSW Champs at Temora and immediately afterward went to Tamworth and got my Unlimited LLP with the CASA-man. Full steam ahead for a solid summer of training with a view of maybe moving up to Unlimited in 2011.
But, the A$ was so strong - what could I buy? I HAD to take advantage of it. So I ordered a Sky-Dynamics sump, cold air intake and 4-1 exhaust. I didn't NEED any of this, the 'plane had more performance than I could currently use, my only concern on occasion was oil pressure drops. Regardless, off went the money and in due course it all arrived. Merry Xmas to me..
In between harvest and New Year I fitted it all up, changing some cable runs and oil cooler hoses etc, all with the goal of less weight and less complexity. I was really happy with the finished job - neat, sanitary, light and simple! There was only one problem - it ran like crap. Rough, some cylinders lean, some rich. At WOT it felt like two cylinders dropped out altogether. Horrible it was, really bad. And it was hotter. Oil temps had always been marginal, now they were over redline after a sequence on a warm day.
I tried to sort the problems, but nothing really helped. I suspect oil temps were up due to the loss of cooling from the fuel/air mixture going through the sump, and maybe a hot cylinder or two.
The cold-air intake with no plenum, no heat from the oil and sharp bends to the intake tubes just would not play nicely with the Ellison TBI I'd used with success up to then.
So what do I do now? Put it back to original? I'd trashed my old inverted oil lines to make the new ones. I'd spent the money....and the exchange rate is so good, right? So.........
I investigated fuel injection options and ordered an Airflow-Performance FM-150. Delivery will be six weeks....what! So much for Summer training.
Eventually it arrived, after only three weeks, and I started installation. Not as straghtforward as you would like. Due to the previous mixture conniptions, I'd bought and installed a 4-channell EGT gauge. I also had to change the low-pressure electric boost pump (Facet - simple cheap type) for a high-pressure one (Weldon - heavy, dear). Luckily I had the old one that was in the airframe when I bought it. The engine driven fuel pump also needed changing for a high-pressure type. More $$ and a bastard to change with the engine on.
And, surprisingly (or maybe not, it is an aircraft after all...) the servo orientation was limited by the Sky-Dynamics intake support struts, making the throttle and mixture cable runs more difficult, and putting the fuel supply and outlet ports in less-than-optimum positions. I thought being in neighbouring US States and this being a 'typical' acro combination, it would fit up sensibly.
Solution - simple, drive to Sydney (400km one way) and purchase special hose fittings to do what I needed.
Finally it is all on, and ground runs are complete. Seems to run OK. Not as tidy an install as the Ellison, and substantially heavier. I haven't weighed it yet, but it won't be sub-900lb as it was before. And the CG will be further forward.
So for my $X,0000 I got a heavier, less balanced aircraft! Maybe, hopefully, I gained a few HP and guaranteed oil pressure in all attitudes.
Somehow, I think my $$ would have been better spent on avgas. So, next time - if it ain't broke, don't fix it!
Postscript: So far two test flights and some gentle aeros. The A-P FI is doing as it should, only the idle needs adjusting up a little. EGT's mid 1200's at WOT leaning to mid-1400's before power goes down (my probes are 6-7" from exhaust flange). 25-30F max. EGT spread most of the time. The trim has changed, as expected. Time to boogie!