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Old 02-08-2019, 05:58 AM
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FlyFastJP FlyFastJP is offline
 
Join Date: Dec 2013
Location: Livingston, TX
Posts: 148
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Hey Dave. Thanks for the info. It doesn't make sense that SARL would make you run in the gold class with a 360. That's the limit in their rule book. I'll ask Mike about that at the first race here in Texas this year in April. I bought my plane, and have yet to do any type of measurements as far as inlet/outlet areas. I normally run 205-209mph here in the 95+ deg Texas summer at 1500 agl. My CHT's top out at about 345-348 with one being in the low 330's. I don't have a FF gauge yet, but best I can figure after fill-ups is it burns about 15.5-16.0 at those speeds. Oil temps hits 220 as well. With the current prop, she turns right at 2800. I just bought the 2nd electronic ignition and will put that on in the next month. Mine is carb'd and I have a few idea's stolen from here for a ram air tube to try and gain a small bit of MAP. My new wood race prop is almost done, which means I need to get the 10:1 pistons ordered and put in. Plan is to spin it to 2900-3000 during races, but I'll need the extra ponies to be able to.

Like your's, my CHT's could be higher. Mine is overcooled as well given the conditions I fly in. I would like to reduce the inlet sizes, but that requires the plane being down for an extended time making a new cowling. I enjoy flying it too much to do that yet. I'm thinking about experimenting with tape or fabricated block off plates to see how that works in reducing them. Also, I need to fabricate some type of tunnel in the lower cowl to help the air exit better. I'm sure those mods alone would increase the speed a bit.

I'd love to pick your brain a bit about your cooling drag improvements. I've tried the few links (older) that are posted here but they have all been taken down. If there are current links you could point me to, I would be greatly appreciative.

Safe flying,

Johnnie

Quote:
Originally Posted by Dave Anders View Post
I know that running in Gold class would normally mean your running a larger engine. I have asked about that but I was told it was because of the modifications that I had done, because I have an angle valve IO-360 running 10 to 1 CR. It's down on hp since my last component changes in the engine a few years ago. Actually I don't think the the airventure cup ever let me run in any other class. The most the engine ever made was around 235 hp but now it is more in the range of 200. It's max FF on the deck is 14.5 gph at WOT 12.6 AFR and running 2800-2850rpm. (I am working on a tuned induction system currently and the first tests seem encouraging) So at 2700 rpm it may be about 190 just for comparisons. During the airventurecup race it ran 1 CHT at 340 and the other 3 around 330 and i think the OAT was in th 80s and that was at about 1700 MSL. With my inlets, plenum and augmented exhaust, it's over cooled. However, it does allows my to climb from my 600' rwy to 17500' in about 10 mins at 110 IAS under max power conditions in the summer here in Calif. I see 1 cylinder at 380 and the other 3 don't break 370 and that's as I go through about 12000' then it start cooling down. The oil temp will make about 218 under those conditions but it also starts dropping at around 12000'. All in all i wish i had on made the inlets a bit smaller and followed my original calculations in 1995 but since I'm not an aero engineer, I oversized them 10% by volume and they're too large. I run a 75-78% outlet to inlet ratio and have a total of 34 sq ins of inlet. I would like to see about 410 CHTs or so in a race. I think the plane would be a bit faster. But it runs pretty good now and that would be a LOT of work to change my carbon fiber cowl. BTW, my rv with an angle valve IO-360 and a hartnell constant speed prop weighs in at about 1010 lbs (empty weight) with all the weight management I've tried to do. I was able to get the weight down to 975 lbs for the triaviathon competition with the battery, starter still on the plane and day VFR legal. That was according to the CAFE foundation.
Cheers guys,
Dave
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