Exhaust and Intake Risers Touching?

Any DA40 related topics

Moderators: Rick, Lance Murray

User avatar
Rick
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Rick
Aircraft: DA40
Registration: N171PS
Airport: KROA

Posts: 1438
Joined: Tue Jul 06, 2010 10:09 pm
Has thanked: 99 times
Been thanked: 233 times

Re: Exhaust and Intake Risers Touching?

Post by Rick »

I have owned both non-PF and PF DA40's, and there was a noticeable difference in climb power and cruise speed. I lube the joints at every annual. The removal, disassembly and cleanup takes me about 2 hours. The mechanic then looks it over and approves it for reinstallation, which takes me another hour. But I'm not particularly fast, and I do spend a lot of time cleaning up the joints. We have replaced the exhaust pipe hanger once in 8 years.

The other expense is the exhaust pipe insert, which must be replaced every few years. I usually get 3 years out of mine before enough of it wears away to require replacement. A new insert runs about $260 form PowerFlow.

So the additional cost of running the PowerFlow is a couple of hours labor at each annual, plus $260 every third year. Remember, too, that the stock muffler also requires the heat shroud to be removed annually for inspection of the muffler, which probably offsets one of the two hours labor.
2007 DA40 XL - Roanoke, VA (KROA)
User avatar
blsewardjr
4 Diamonds Member
4 Diamonds Member
FIRST NAME: Bernie
Aircraft: DA40
Registration: N377DS
Airport: KCHO

Posts: 316
Joined: Tue Jul 26, 2011 11:19 pm
Has thanked: 60 times
Been thanked: 62 times

Re: Exhaust and Intake Risers Touching?

Post by blsewardjr »

Rick- Agree. I just had my exhaust pipe insert done at the annual.
Bernie Seward, IR, AGI
2003 DA40 N377DS
KCHO Charlottesville, VA
User avatar
shoffert
2 Diamonds Member
2 Diamonds Member
FIRST NAME: Stephen
Aircraft: DA40
Registration: 506DS
Airport: KAVL

Posts: 28
Joined: Wed Jan 15, 2020 2:20 am
Been thanked: 9 times

Re: Exhaust and Intake Risers Touching?

Post by shoffert »

Powerflow on order.

Very nice used, but in need of an adjustment, stock exhaust for sale. Great shape. Any takers?!
User avatar
Davestation
3 Diamonds Member
3 Diamonds Member
FIRST NAME: David
Aircraft: D-JET
Registration: NDJET
Airport: KFTW

Posts: 136
Joined: Tue Mar 12, 2019 7:49 pm
Has thanked: 58 times
Been thanked: 36 times

Re: Exhaust and Intake Risers Touching?

Post by Davestation »

Haha "stock exhaust" we think, maybe.

I'm more concerned with the aftermarket ignition harness flapping in the breeze though TBH, have them correct that while they're at it.
User avatar
shoffert
2 Diamonds Member
2 Diamonds Member
FIRST NAME: Stephen
Aircraft: DA40
Registration: 506DS
Airport: KAVL

Posts: 28
Joined: Wed Jan 15, 2020 2:20 am
Been thanked: 9 times

Re: Exhaust and Intake Risers Touching?

Post by shoffert »

To close out this thread...

...it appears that during an exhaust repair the shop allowed themselves to shorten up the riser to my #1 cylinder, slightly changing the angle in an area where things were already pretty tight.

Of note, no mechanics could find any guidance on the minimum spacing between exhaust risers and intakes on the IO-360.

One mechanic even said it was okay to touch as mine were. I don't like that, but in his defense there was zero marking on the intake tube after flying that way for at least 40 hours (that was when the engine was overhauled, but the exhaust work was well before that so it could have been even longer). PowerFlow, in their install manual, defines the minimum space between the two as 0.03"...three thousandths...pretty tight.

My solution was to swap out the old exhaust with the PowerFlow...PowerFlow did a great job and got the new one to me in less than a week. Install with 2 people was about 4 hours. I added the Arizona Baffle at the same time as was recommended, and that took about 3 hours. I'm seeing a 4KTAS speed gain at 8,000' and my CHTs are about 15deg cooler for comparable power settings and airspeeds.

I recommend this upgrade to any of us with the older planes that don't have it standard.
User avatar
Davestation
3 Diamonds Member
3 Diamonds Member
FIRST NAME: David
Aircraft: D-JET
Registration: NDJET
Airport: KFTW

Posts: 136
Joined: Tue Mar 12, 2019 7:49 pm
Has thanked: 58 times
Been thanked: 36 times

Re: Exhaust and Intake Risers Touching?

Post by Davestation »

.03” - 3/100 ~1/32”. For minimum spacing on the factory install you’d probably have to talk to engineering. No sense in prescribing it in the field if it was it designed to be adjustable.

I think they want juuust enough space so they don’t touch when vibrating, although I’m still surprised it’s so low. They have you put a shield around the engine frame on the left side and that’s already at least 1” away.

Touching is definitely not good, not just because of wear over time but also the exhaust would significantly heat the intake air.

Thanks for the feedback on the PowerFlow, 4kts is more than I would have expected. Glad you’re happy with it.
User avatar
Rich
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Rich
Aircraft: DA40
Registration: N40XE
Airport: S39

Posts: 2765
Joined: Mon Aug 30, 2010 12:40 pm
Has thanked: 71 times
Been thanked: 460 times

Re: Exhaust and Intake Risers Touching?

Post by Rich »

Any spacing would be fine. The notion of mutual wear from vibration would be the major factor. The amount of air in the intake pipe that could be heated by the very small area where the exhaust and intake pipes cross is minuscule. Every intake stroke for a given cylinder is trying to pull in 90 cubic inches of air. Given the diameter of the intake pipe, this means about 37 inches of equivalent pipe length. This happens roughly 20 times per second, which means there is only 50 ms to transfer some heat to that small region.

I figure that heat shield for the engine mount is more to protect the paint from radiant heating and long-term oxidation that could result.
2002 DA40: MT, PF, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210.
User avatar
Chris B
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Chris
Aircraft: DA40
Registration: N171CB
Airport: KRHV

Posts: 817
Joined: Wed Sep 26, 2012 1:52 am
Has thanked: 187 times
Been thanked: 192 times

Re: Exhaust and Intake Risers Touching?

Post by Chris B »

Congratulations. And thanks for following-up! :thumbsup:
shoffert wrote:
Mon Jul 13, 2020 8:14 pm
I'm seeing a 4KTAS speed gain at 8,000' and my CHTs are about 15deg cooler for comparable power settings and airspeeds.
You should also experience a noticeable climb rate increase with the Power Flow exhaust.

Chris
Post Reply