Shotgun

I'm installing a 6port 13B in a Dyke Delta, a 200mph, 4-seater, homebuilt airplane. See my website if you're interested.



http://ernest.isa-geek.org



My interest here is the very interesting discussions on porting. I have learned a lot, but I still have one specific question.



I'm considering removing the wall between the secondary ports and combining the runners, both for more power and to make the constuction of a my custom intake manifold simpler. Max RPM will be around 8000 (limited by prop tip speed), and cruise RPM will be between 6500 and 7000 (limited by fuel on board).



I've read Judge Ito's remark that this setup will have a rough idle and very little low RPM power. Neither is a concern in an airplane application. In an airplane there are basically three modes of operation. Taxi to end of runway (very little power needed as you shouldn't exceed the speed of a fast walk). Take off and cruise (you firewall the throttle and leave it there, unless it is a short week and you're trying to save gas). Landing (you need to throttle back so the airplane will come down. Slower idle makes for a steeper decent, which many consider safer, but it's not critical).



So, my question is, "Would combining the secondary ports make sense in this application, and what sort of gotchas will I need to look out for?"

kahren

if you are going to remove the divider dont do it at the face of the rotor, the port will become very large, and unless turboed or spun to a crazy high rpm will not make good power. you can knife edge the manifold side of the secondary and aux ports for better flow from a single runner manifold to those two ports. how far into the port you take the knifeedging is up to you.

ColinRX7

I agree with kahren Just knifeedge the manifold side of the irons, that's what I did in my RX7, and using TII intake manifolds, the car pulled very hard all the way to redline.



Low end torque took a shot when WOT, but what's the difference to you in an aircraft application.



I wouldn't combine the ports on the inside, just smooth them together on the manifold side of the block..

Syonyk

You also probably want to consider the shape of the auxiliary intake ports. With the 6 port sleeves removed, there's a nice long cylinder for the air to flow down, with a solid wall at the end, and an opening about halfway down the side. Smoothing that out (similar to what the Pineapple inserts do with the stock 6 port sleeves) will help power up at the high end.







-=Russ=-

ColinRX7

I wouldn't trust pineapple sleeves in an airplane





They take OEM sleeves and PRESS in that aerodynamic piece



Street cars equipped with those have had sleeve failures where the piece has come out and destroyed the engine...





At least on the ground you can pull over and scratch your head, not so lucky in an airplane..

Syonyk

Not entirely true.



First, I never suggested he use Pineapple inserts. I said that shaping the end of the aux runner along those lines would probably lead to some better flow at high RPM.



Second, that piece cannot exit the sleeve and get into the engine. The problem was that it came loose in the sleeve, slammed back and forth, and eventually broke the rod that the actuators join with to turn the sleeve. THAT rod came off and went through the engine, not the actual insert.



Finally, when properly secured, a Pineapple insert isn't going to leave. Most people now secure them very well. Locktite + dinging the sleeve in front of them is a commonly used method, as is drilling into the rear of the sleeve (and insert) and using a screw to hold the insert in.



-=Russ=-

ColinRX7

Don't be so defensive I wasn't attacking you I was attacking pineapple





Regarless of which piece came apart and destroyed the engine, the fact remains, the pineapple sleeve was the cause, and engines got wrecked.



I wouldn't run that risk in an airplane

diabolical1

[quote name='kahren' date='Jun 14 2005, 11:32 AM']you can knife edge the manifold side of the secondary and aux ports for better flow from a single runner manifold to those two ports. how far into the port you take the knifeedging is up to you.


[/quote]

kahren ~



i'm having a bit of trouble visualizing what you said here. could you please explain it for a simpler mind.

Syonyk

Didn't mean to sound defensive above, just clarifying some stuff.



And I'd be happy to fly in a plane with pineapple inserts, so long as they were well secured.



As for knife edging the manifold side, the way I understand it is as follows:



The iron has two separate passages leading into it - the secondary port area, and the aux port area. There's a chunk of metal between the two, and on the outside of the iron it just forms a bit of a wall.



When feeding from a single intake manifold, if you grind that down so it's a knife edge, you'll get better flow. ASCII art following to kind of make my point.



Stock: Manifold goes on the left.



----------

Secondary port

----------

|

----------

Aux port

----------



Now, after knife edging, it would look something like this:



----------

Secondary port

___----------

\

----------

Aux port

----------



Kind of. Basically, take the solid wall off the iron and make it a point to split the airflow better with less turbulence. Correct me if I'm wrong, please.



-=Russ=-

banzaitoyota

[quote name='ColinRX7' date='Jun 21 2005, 10:58 AM']Don't be so defensive I wasn't attacking you I was attacking pineapple

Regarless of which piece came apart and destroyed the engine, the fact remains, the pineapple sleeve was the cause, and engines got wrecked.



I wouldn't run that risk in an airplane


[/quote]





The Pineapple insert did not fail: THE INSTALLATION FAILED