8KCAB Exhaust

[djpacro]

The previous owner fitted a https://www.powerflowsystems.com/ exhaust to my Super D when he rebuilt the engine and prop so didn’t get a direct check on the effect of the PowerFlow system. It has an MT prop, cruise speeds slower than the book but slightly better fuel flows. My friend has a ‘78 model fitted with new wings, a Superior engine, new Hartzell metal prop and Power Flow exhaust at the same time so again no check on the effect of the new exhaust - his cruise speeds are better than the book.

Wondering if anyone else has fitted a Power Flow system and can provide performance data?

 

[Bob Turner]

I don't think cruise speeds are a function of max power.

My Super D is a 120 kt airplane (at 7500'). I think the book is 136 Kts. I get that going downhill.

The big advantage in changing exhaust systems is that AD. I think metal spar wings increase cruise speed a bit.

 

[JimParker256]

No experience with PF on a Champ-type airplane, but on Grumman AA5 Traveler / Cheetah aircraft, the PowerFlow adds about 10% more power, which increases the rate of climb by about 150-200 FPM – much appreciated in a Traveler / Cheetah. Top speed doesn't change unless you change the pitch of the prop, since you're turning the same RPM with the same prop pitch. But that required some attention to avoid exceeding max RPM, since the additional power would allow exceeding redline.

On the speed side, however, some reported they could maintain 75% power at higher than book altitudes, thus their cruise TAS was better than book values (albeit at slightly higher-than-book fuel burns, as well). We're talking 2-3 knots here...

 

[rjgritter]

I know this is an ancient thread, but can anyone give details on the PowerFlow system installed on 8KCABs? I've asked PowerFlow about a system for the Decathlon a couple of times now and each time I've been told they don't offer one. Are people using a system intended for a different airplane? If so, which one?

 

[djpacro]

Apologies, I haven't been here for ages and ages.

I don't think cruise speeds are a function of max power.

True. I would expect lower fuel flows from the PowerFlo system for the same speed. Now that I have put a standard system back on my Super D I can check that.

I know this is an ancient thread, but can anyone give details on the PowerFlow system installed on 8KCABs? I've asked PowerFlow about a system for the Decathlon a couple of times now and each time I've been told they don't offer one. Are people using a system intended for a different airplane? If so, which one?

Per our recent discussion on Facebook.
The original owner of my 2007 Super D fitted it after a year or two. Approval by an Australian equivalent of a 337 form. Been repaired a few times and my welder said no more so recently fitted the std system. Had to rework the cowl to standard as the PowerFlo needed a bigger hole. Seemed to work fine but I have no direct comparison with the std exhaust.
I told PowerFlo about it at Oshkosh some years back, they were surprised obviously.