813KR$

When I hear about street porting an engine, it is always about smoothing and opening the close of the intake port with out removing too much metal so you dont break into the coolant passages or allow seals to fall out. Why dont anyone talk about opening the start of the intake? Their is no seal interferance and enough metal to remove with out hitting coolant passages atleast 1/16th of an inch can be removed from the start of the port with out breaking into coolant. Why not do this?

RETed

Does it have anything to do with your attached pic???
That pic looks like it's just an extended port - close time is delayed.
I don't see it opening earlier?
If you do, it is possible.
Just don't cut too much into the corner seal path, or the corner seal will fall into the port itself.


-Ted

813KR$

The pic has delayed close of the port and also opens early. The yellow part would be the new port shape. The yellow, early open part of the port is no where near any seals. The only problem I would see is having to stay away from the coolant, which wouldnt be a prob.


Any opinions?

modrx7

iTrader: (1)

try nopistons.com they talk alot about engine porting/building there.

Edan

peejay

The opening edge is the edge on the left side of the pic. Not at the bottom.

Bridge ports are so the port can open earlier, and still leave a "bridge" of metal to support the side of the apex seals as well as the corner seals and the ends of the side seals.
You can't open the existing port earlier very far without running into trouble, starting with munching up the side seals.

RETed

What he said...

Going down doesn't open the port earlier - you're getting a bit confused.
Going "LEFT" opens the port earlier.

Porting down gets you no where, but you do start to intrude on the oil seal path - check the cross between the two grooves around that area.


-Ted

z8cw

Make yourself a template of plexi glas of the sideplate and watch your rotor pass by the ports when your engine is apart. This will be the best way to learn. All the explanations are helpful but best is to see for yourself.

CW

RacerXtreme7

iTrader: (2)

http://www.rotaryengineillustrated.com/index.html

http://www.rotaryengineillustrated.c...s/an-RE4a.html

http://www.rotaryengineillustrated.c...s/an-RE3a.html

Go get your learn on.......

~Mike..........

813KR$

This is what I got:

http://artisticperformance.com/v-web...Gallery?page=4

I was thinking about doing another port configuration on a spare set of side plates? Im now rethinking and will probably stay with what I got?

What do you think?

813KR$

Stayed with what I had:

http://artisticperformance.com/v-web...Gallery/street

It is together with old shity housings, not extremely bad, but bad enough and rough bearings. New apex and solid corner seals, new springs under every seal but the oil rings. With the corner seal springs being fd's. We will see how it runs!

diabolical1

iTrader: (3)

question, peejay ... when you bevel the rotor, isn't that technically opening the port a tad earlier? or have i totally missed the point to rotor bevelling? i know the original question focuses on the port itself, but ...

peejay

Yes it is, and no you haven't.

It's more than just a tad, too.

813KR$

So what type of increase would come from beveling the rotor? Would a big street port with bevel rotors be similar to a bridge? as in the power increase? dont you have to get the rotor assembly balanced after that?

diabolical1

iTrader: (3)

i doubt if rotor bevelling will get a streetport to run neck-and-neck with a bridge in terms of power, but i honestly don't know. from what i've seen and my limited understanding, i honestly don't see how it could.

the way i see it, bevelling is probably going to make the most difference with forced induction, but i may be full of sh ...

for the balancing, i've read where 2 people so far have claimed to bevel rotors for themselves and did not re-balance because they said they removed the exact amount of weight from each rotor with their cuts. HOWEVER ... i'm pretty much a Murphy's Law kind-of-guy when it comes to engines, so i would recommend a re-balance. i'd rather spend extra money (or time) and just remove one more possible failure point than have to repair or trash an engine.

my 2 revs ...

oh ... and thanks, peejay. you always help ...

peejay

If you think of forced induction as just artificially raising atmospheric pressure, then what difference does it make?

What gets air into the engine. The rotor moves around and makes the chamber volume expand. This makes a low pressure area inside the engine that the pressure in the intake manifold pushes air into - whether you're sitting at a light at 15 inches of manifold "vacuum", wide open throttle at 5,000 feet above sea level, wide open throttle at sea level, or cranking 10 pounds of boost into the engine with that big yummy turbocharger.

diabolical1

iTrader: (3)

i can visualize what you're saying at idle and at low RPM, but i'm having trouble with the high RPM-stuff. with the ports staying open for a comparatively less time, why wouldn't the positive pressure (of any measure) at high RPM make a difference in two almost identically built engines, only difference being bevelled rotors on one and not the other?

TrentO

If you look at the air path into the engine, rotor beveling would cause a slightly earlier opening, but with the airflow path haing to turn abruptly to enter the chamber. With a trailing edge bevel you could gain extra open duration as the beveled rotor edge would extend the time the port remains open and would give a smoother shot.

my $0.02
-Trent

peejay

The air path has to turn abruptly anyway during the port-opening phase. This is a major reason why bridge ports shine and peripheral ports are king - the airflow doesn't have to make a 180 degree turn at port opening. Nearly straight shot in no matter how the rotor is positioned.


But OTOH you don't really *need* a closing time later than what can already be achieved with a decent extend-port. Closing the port later just drives the powerband higher and hurts the low-end. Achieving all this with the port instead of the rotor allows the port to blend the airflow into the chamber at a nicer angle.

813KR$

So with all this being said, or not said, I would think you could get comparable power gains between a street port with bevel rotors compared to the bridge? My reason being I know with EFI and street port you can get 250hp, so shouldnt the beveled rotors with the big street port atleast gain 10% over the already 250hp of the EFI SP?