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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Oct 12, 2012 2:36 pm 
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With the 6 port plate instead of BPing it can you get rid of the bridge(before BP) and make a large mild port?


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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Jan 25, 2013 10:22 pm 
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hi guys,

looking into building a new 13b turbo motor and wanted to get some feedback/answers on if the idea will work.
car is a s2 that will be street driven but want to do some track days and just have a fun car that i can really push when i want to and it be able to handle the punishment
im looking to have the porting and dowelling done by a shop most likely (not up to that myself yet)
the idea is to build turbo extend primaries (a little easier on the rd wen i hav to drive slow) and then have turbo bp secondaries
is this port combo something that will work with the right settings?
from reading around thinking of a t04/t04z turbo...good start with enough guts to wind up later?
i have a s4 13b turbo block currently...will this work for the combo? am i going to need to change anything rotors or housings for better results/reliability? or will this depend on the condition of them when the engine is torn down and inspected?

currently car is running a kevin potts 13bbp with 48mm ida carby motor that goes really hard but would like more response and power and keeping this motor for another car that will be "old skool" style

posted in this thread for some input on the porting idea but if id be better of posting elsewhere point me in the right direction plz =)

cheers scully

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Jan 26, 2013 5:26 am 
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alco wrote:
With the 6 port plate instead of BPing it can you get rid of the bridge(before BP) and make a large mild port?


how can you have a large mild port....
a large mild port is an extent port, so no you cant. I have seen them opened right up into a very large extend port before, no idea how it ran though, I wouldn't bother...


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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Mon Feb 04, 2013 7:16 pm 
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get rid of this making a some kind of port(big)


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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Tue Feb 05, 2013 12:27 pm 
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biggest isnt best.. inlet airspeed is higher on the separated port runners and that has implications in chamber filling efficiency and atomisation / fuel stratification

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Mar 15, 2013 3:47 pm 
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first time back yard porter here.

i have got hold of some second hand N series plates and want to have a play with some home porting.

looking at just a decent extend port for starters.

my question is regarding the 11mm measurement mentioned quite a lot in this thread for the outer maximum edge of the port ?

what is the best way to measure this on the earlier plates which obviously have no water seal grooveto measure from ?


is there a dimension to widen it based on the existing port edge ??

thanks

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Mar 15, 2013 7:13 pm 
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old plate should have a visible mark from the water seal on it .. however that 11 mm measurement is VERY ambiguous and i would not go anywhere near that

if plates are worn then you may have a slight trace that shows where the leading edge of the side seal passes.. try not to port this away ,, thus keeping the side seal ends captive

if not captive then you have to ramp the closing edge and push it out wider to avoid scissoring the seal against the opening edge of the port and to avoid rubbing or nibbling the end of side seal against the closing edge

this is why you get a template !! absolutely a must for first timers to get things reasonably same and safe for side seals

with N plates ,, you have a rare opportunity to port all 4 the same .. a large advantage in top end power over those stuck with unequal ports and there really isnt much need to push the port for absolute maximum early open edge

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Mar 15, 2013 7:52 pm 
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I've never understood why you'd use the water seal groove as a reference when it's not always in the same place :roll:

Sorry for the poor picture quality I just whipped down the shed and took these in the dark, but you'll get an idea.

This is an old mild ported R5 end plate (from a carby Jap import TXQ equipped Motor) out of a mates motor we ported and built in 1990. These were ported in a mates workshop one evening after hours in a hurry so are a bit rougher than what we did for customer motors, but it was a tough motor none the less. Centre plate was a tall runner N plate to get the primary ports just as big.

It gives you an idea of distance from the rotor housing surface in any case and a basic idea of how the port was shaped. Be aware that where I measured was the closest the port gets to the rotor housing, as it goes up it basically tapers back to somewhere near the original top outer edge of the port is.

Also If you are going to go that high with the port be very careful with depth otherwise you'll hit water.

Image
Image

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Mar 15, 2013 8:52 pm 
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It's probably also worth noting that you can see where the side seal has been scissoring/catching at the top of the port, modern porting styles are squared off to avoid this awkward re-introduction of the side seal.

Here's an example of what I mean, see how the top right (left in Dazz's pics) is squared off more. This gives the side seal a better path.
Image

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Mar 15, 2013 9:40 pm 
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thanks guys,

there is a mark from the water seal but i'm not confident using that as mentioned.

if i do come in 11mm from the water seal that line is about 3.5mm from the outer edge of the existing port.

there are quite a few visible wear marks so maybe i can pick out the side seal marks.


i have noticed quite a few comments about squaring off the top of the port as mentioned.


the hard thing at the moment is i have only got plates, no housings or rotating assembly to try and line things up.

might try and track down a template..

any recommendations for an angry extend port ??

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The new one - not so stock anymore S3 - http://ausrotary.com/viewtopic.php?f=21&t=223532
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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Fri Mar 15, 2013 10:43 pm 
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brown hornet wrote:
any recommendations for an angry extend port ??


Yep, like the pic I posted :lol:

Any marks on the plate are from the debris from the stationary gear collapsing, there is no side seal issue with those ports or the design if finished properly. These same ports were in multiple motors back in the day and all performed brilliantly and were perfectly reliable.

Similar shaped ports with the addition of being bridge ported have been in circuit motors for years with no issues at all. So again don't just use blanket statement to classify all ports of a similar style together as the exact positioning does vary even though some pots may look the same.

Square top edged inlet ports tend to have a different characteristic to their power band, tending to have a little less mid range than the nicely flowed rounded top version. Unless you have a very top end orientated inlet system, very free flowing exhaust, and close ratio gearbox/low diff combo, you want the port that gives the broadest spread of power across the whole rev range you use, not just the last 500rpm.

We tried a motor with similar inlets with squarer tops, and similarly squarer exhaust ports which in theory give slightly more top end power, and it did, BUT, overall on road acceleration in a similar car was no better.

To clarify that more, the more rounded ports gave a stronger mid range so you had better power over 90% of the rev range, slightly better drivability, and unless you were well up into the revs would accelerate better from lower rpm.

You can get away with sacrificing mid range in a turbo motor with porting as the turbo brings its own mid range, but an aspirated motor relies on air pressure alone, so you have to make sure what you have is right to begin with as there is no way to artificially increase torque.

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Last edited by Dazz on Sat Nov 09, 2013 11:17 am, edited 1 time in total.

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 12:09 am 
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i wish i took pics before i bolted it up but i'm sure i 'rounded' everything as much as possible on my bridgeport, as depicted in pics above. i didn't know what i was doing when i drilled into my plates and didn't use a template, so it'd be unlikely i went the 'precise' squared off route.

i reckon the mid-range driveability of my bridge is good.

i had a professionally drilled extend port previously and the bridge doesn't seem that much different mid range (obviously at high revs there is a huge difference).

but i'm not quite sure i have my head around the 'scissoring' effect on the side seals a rounded port will have.

does it load up on the last tiny bit of side seal left hanging over the port and flex in? whereas the squared off port is more 'on/off' as far as the side seal being suspended over the port goes?

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 2:38 am 
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Quote:
but i'm not quite sure i have my head around the 'scissoring' effect on the side seals a rounded port will have.

does it load up on the last tiny bit of side seal left hanging over the port and flex in? whereas the squared off port is more 'on/off' as far as the side seal being suspended over the port goes?


as the rotor travels past the port the leading edge of the side seal should pass always over metal ( on all but early open extend ports )
as it continues to travel.. the side seal is also moving in an inboard direction and the middle portion of the side seal is visible exposed across the open port, unsupported,, even on stock engines

rotate further and when it gets to the trailing edge of that same side seal.. the side seal is now moving outward towards the opening edge line on the port

with a bad port .. the trailing end.. not on exactly the same path as the leading edge, can drop into the open port slightly
- when it does so,, the scissor action of the outboard motion of the side seal will trap and pinch off the last 1/5 or so of the side seal because it is lower than the edge of the plate ( the end having dropped into the port )

.. so a bad early open extendy can round or nibble the leading side seal edge .. and can also pinch and scissor the trailing part of the side seal

similar can happen in some bridgeports when turned over backwards .. some templates have a small tick at the top outer corner of the main port to counter this during reverse rotation

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 3:03 am 
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Quote:
any recommendations for an angry extend port

xtreme ( very straight ) , racing beat ( have to cut yourself ,, atkins sell same ) , pineapple ( straight and sharp tip ) , judge ito ( good if you can manage to track him down ) , mazdatrix ( pricey, similar to the RB one )

edit.. and this bloke > swear thats almost a copy of mine !!!
viewtopic.php?f=7&t=227530


some ( RB ) you cut out yourself.. all align with dowels
..some exhaust port templates come with a frame to line them up.. others you line up manually with the edges on a through bolt hole


myself sit in both camps.. i have built lolly pop ports ( having to clean up someone elses shocker ) and straight top ports ..

and have settled on one with a slightly rounded top.. middle ground and its very similar to the RB one , takes the open edge out only a couple of mm


be aware the closing face of the rotor as it closes the port is not straight..... and is in fact a slight curve
.. straight edges look nice but serve no real purpose beyond being nicer to look at and easier to match up


... which port is actually best where will be equally determined by a whole stack of other factors like induction length , exhaust system and also the exhaust port shape and are difficult to quantify one to another

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 Post subject: Re: Everything You'd want to know about Porting on a Rotary
PostPosted: Sat Mar 16, 2013 11:58 am 
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What you need to think about is the whole package and style of driving you are going to be using the motor for.

I can give you some insight from someone who knew an awful lot about these things, via some e-mail conversations we had in regard to motors current;y used in front running IPRA cars, and it basically goes as follows:

"I've noticed a lot of people now using that angled but very straight top edge of the main port style of porting, as opposed to the slightly radius'd style you prefer to use".

"This is what’s in "Driver A's" car. Works a treat at high RPM as it causes a sharp cut-off and consequently a crisp pressure reversion. The exhaust is pretty square as well, which makes for that crisp pressure reversion. (Consider the different sounds you get from a bugle by changing the lip tension – the lips act as reeds, as does the inlet an exhaust ports).

By rolling the top of the port, you are squeezing the incoming charge and you get better torque, but a softer tone, and hence the ram tuning effect is not as great. With this style of porting "Driver B" can (and does on a regular basis) plant his foot flat at 4,500 RPM. Try that with "Driver A's" motor and it will shake the fillings out of your teeth! Horses for courses.

"Driver B" couldn’t drive a motor like "Driver A’s, as it has to be kept up on the pipe above 6,000 rpm all the time (I was looking at the RPM logs, and Driver B never lets it get below 7,000 RPM – he’s got a very Close Ratio dog-box in it). Driver B on the other hand, even with the Jerico Close Ratio box, can’t keep the motor on the boil – half his trouble and why he’s not quite as fast. However, his motors have so much mid-range torque that he doesn't need to keep the motor that high in the rev range to achieve similar if not better off the corner acceleration.


There was another instance where a direct comparison was had with two engines, one from another engine builder that used the very peaky style porting, vs the lower "Hollywood RWHP" motor.

"when Driver A re-fitted my "old dunnger" engine as a last resort (he'd run out of money - (grenading 2 x 15K race engines doesn't do ANY racer's budget much good), the "gearbox and tailshaft" vibration magically disappeared - funny abouy that too!. What's more, he was able to do the SAME lap times as with the Big HP Motor, even though mine was supposedly down 35 BHP right at the top end - it's just that you diddn't need to rev the sucker any where near as hard (9,500 instead of 10,500) as it had a torque corve like the Nullabour Plain. Pulled like the proverbial 14 year old schoolboy!

The advantage of all this "fart arsing" with the ports is the broader torque curve. But as proof of the pudding, I dyno'd the new Series 6 13B in "Driver C's" IPRA car last Monday night. 270 BHP (corrected back to standard temp & press - it was running 38 Deg C MAT on the dyno - it was a HOT and humid night!) at the back wheels - which was the best Dave Flood's seen on his new dyno, and not much less than the best Leanne Ferrier had from her championship winning motor.

Bear in mind that the manifold on the car is still the old unequal length steel contraption I cobbled together purely for testing back in 2004. As well as that the inlet runners are bigger on the new engine compared to the previous motor, and there is a 10 mm step from the manifold to the bottom of the port (aids gas flow NOT!!). Nevertheless, Dave Flood commented that he cannot believe the mid range torque that I'm getting from this thing compared to the other motors he's dyno'd."


So, take all of that any way you want, but we are talking direct comparisons with top shelf competition motors, with data logging that shows the characteristics very well in regard to what rpm band the engines will work in, as well as back to back dyno numbers and comparative lap times in a real world situation.

My point is if you are running a motor in a street car, with a non close ratio gearbox that will not allow you to keep the engine in a narrow power band, even though you might find 10 more hp right at the top end, you will be losing the same amount or more across most of the usable rev range, as well as suffering worse drivability to boot due to the nature of the porting, mainly that slightly less stable part throttle drivability and low rpm smoothness.

Anyways, opinions are like arseholes, everyone has one, but there's some insight for digestion for those with an open mind.

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