flyrotary@lancaironline.net Mailing List Archive

John,

My turbo REW engine now starts almost instantly and runs very smoothly at all rpm ranges. There's little if any soot on the prop so long as I don't run too rich on take-off. My static used to be 4050. Lately it's been in the 3900's with 46 MAP. More MAP (I tried briefly up to 50 today) doesn't do a damn thing. There's plenty of power to take-off and climb, but not as much as I had way back when before a thousand changes because of which I can't pinpoint when the power changed. Could be fairly recent (in terms of hours) and after the new turbo was fitted. Could be partially a result of the hi-flow turbo, but I think not all.

As I recall, you commented after getting your turbo reworked that you lost allot of power. If it has a higher A/r ratio, that would be expected. The turbo is now turning less RPM's at cruise power than it used to. That should greatly extend the life of the turbo, but at the cost of some power, especially at low end.

Your RPM's are way low. The HP curve on the rotary goes up directly with RPM's. If you aren't getting the RPMs up, you are really limiting how much horse power you are producing, as well as how much boost, since your turbo is running a high A/r ratio. I'm running about 5300 RPMs at 5lbs of boost on take off. I limit my boost to 5lbs with the throttle, to try to keep my stock turbo alive for now. Wide open throttle seems to max out at 8lbs of boost, but I'm not sure about the RPM's, as I didn't keep it WOT but for a few seconds. BTW the power was awesome.

Personally, I'm going with a T4 turbo. I have a Garrett .96 A/r on the exhaust side, 46mm wastegate, and a 304 SS exhaust manifold. I forget what trim it has on the air side, but it will produce up to 25 lbs of boost if you let it. It should run all day at 5-8 lbs. I still need to fabricate the exhaust pipe with a "T" for the wastegate. I'm not in a big hurry to get it changed over, since my factory turbo is still doing fine.

I'm currently flying on 87 Octane. Could this be impacting my ability to produce power this much? I'm working my way through the possible octanes to see how she behaves so as not to get caught out later. The next tankful will be 91, then 100LL. I've tried clean (not new) plugs. That's my next experiment. Any other thoughts or suggestions welcome.

I'm also running 87 octane, but now that you mention it, I'm wondering if I should run 91. I have the stock low compression (turbo) rotors in mine, so I "assume" that 87 octane is OK. I'll be interested to see what kind of feedback you get on this.

Steve Brooks