Porting Efficiency
05-10-2005, 12:13 PM
#41
Senior Member
Join Date: Aug 2004
Posts: 426
[quote name='Rub20B' date='May 9 2005, 08:54 PM']Yeah, WOT starting didn't help, I'm not going to put a car in front if I didn't tried to start is with WOT, if the plugs are wet the chance is big you'll need to do it that way..
[/quote]
what flash do you have?
i think it's the N 1/2 that got rid of the flooding completely (but don't hold me to it)... we never had any problems starting the bridgeport.
or maybe your side seals look like the ones i posted?
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[/quote]
what flash do you have?
i think it's the N 1/2 that got rid of the flooding completely (but don't hold me to it)... we never had any problems starting the bridgeport.
or maybe your side seals look like the ones i posted?
05-11-2005, 12:09 AM
#42
Senior Member
Join Date: Nov 2004
Location: Europe, Belgium
Posts: 147
Car has 30.000km... 1.5 year old..
As I'm not an official mazda dealer anymore I don't have the equipment to flas new rom versions in the ecu, but I went to a friend of me who has a big Mazda garage an they fashed an updated rom version in it, is it normal a renisis doesn't idle as smooth as a REW?
But the time it flooded was after that, If you don't start it much without driving around a while you flood it.. but if you say to the custumers not to do this and when they start is a few times without driving that they drive a bit so the unburnt fuel gets out..
As I'm not an official mazda dealer anymore I don't have the equipment to flas new rom versions in the ecu, but I went to a friend of me who has a big Mazda garage an they fashed an updated rom version in it, is it normal a renisis doesn't idle as smooth as a REW?
But the time it flooded was after that, If you don't start it much without driving around a while you flood it.. but if you say to the custumers not to do this and when they start is a few times without driving that they drive a bit so the unburnt fuel gets out..
05-11-2005, 12:26 AM
#43
Member
Join Date: Oct 2003
Posts: 69
[quote name='guitarjunkie28' date='May 7 2005, 08:03 AM']
but the renesis has its own demons. side exhaust is really restrictive and beats up on the side seals. i'm looking into dinding a company that will coat the side seals with something for more durability.
[/quote]
I feel the same way about this. In the older rotary, the peripheral exhaust put more strain on the apex seals. This and the fact that the apex seals got heated from both sides during cumbustion events. The apex seals being thicker can withstand this kind of abuse however, with the side exhaust of the renesis, the much thinner side seals now have to travel over a hot exhaust port and the seal now gets heated from both sides during the process. Though the side still isn't under as much stress as the apex seals, I feel the thinner side seal will become more brittle with age. Brittle and high mileage aren't a good combination especially if they ever turbo the engine.
but the renesis has its own demons. side exhaust is really restrictive and beats up on the side seals. i'm looking into dinding a company that will coat the side seals with something for more durability.
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[/quote]
I feel the same way about this. In the older rotary, the peripheral exhaust put more strain on the apex seals. This and the fact that the apex seals got heated from both sides during cumbustion events. The apex seals being thicker can withstand this kind of abuse however, with the side exhaust of the renesis, the much thinner side seals now have to travel over a hot exhaust port and the seal now gets heated from both sides during the process. Though the side still isn't under as much stress as the apex seals, I feel the thinner side seal will become more brittle with age. Brittle and high mileage aren't a good combination especially if they ever turbo the engine.
05-11-2005, 02:29 AM
#44
Senior Member
Join Date: Dec 2003
Posts: 162
[quote name='GMON' date='May 10 2005, 07:33 AM']For ***** sake el spit it the **** out. 
I am very curious to see how flow bench numbers correlate to HP/TQ numbers. My guess is that the ports of a rotary engine are so dynamic that flowing the open port is really no indicator at all of wether or not it will make more power.
Think im crazy? Put a rotor in the housing with the apex seal directly in the center of the exhast port and tell me what flow does.
[/quote]
Nothing to say you can't flow with the rotor in there.
I am very curious to see how flow bench numbers correlate to HP/TQ numbers. My guess is that the ports of a rotary engine are so dynamic that flowing the open port is really no indicator at all of wether or not it will make more power.
Think im crazy? Put a rotor in the housing with the apex seal directly in the center of the exhast port and tell me what flow does.
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[/quote]
Nothing to say you can't flow with the rotor in there.
05-11-2005, 10:04 AM
#45
Fabricator
Join Date: Jan 2004
Location: Central Ohio (Hebron) Zephyrhills Fla.
Posts: 1,322
[quote name='BDC' date='May 7 2005, 09:36 AM']That's true, but that still doesn't answer my question -- how is the sharp edge on the stock port's closing edge detrimental to how the charge flows into the chamber?
B
[/quote]
Because the higher the flow velocity, the more pronounced the venacontracta.
There are just 13,000 (I counted them) things to consider when thinking about changing any port or port/runner combination.
The best way to see this and many more of the problems of flow is to go to a small airport on a cool misty morning and watch as a plane warms up. The high humidity will flash to water vapor as it passes through propeller and you can see clearly what happens to the stream of air after it passes through the propeller.
The flow is accelerated, yes? And Bournuli says that a velocity increase yeilds a pressure decrease, yes? So the flow along the cowl is compressed as local air pressure is now higher than the flow and squeezes in along the fuselage.
So so in the engine, the flow enters the cavity through your sharp edged port at high velocity. The local air pressure in the cavity closes in on the entering flow and chokes it down to a dimension smaller than the port shape. Enlarging the perimeter of the port, increases the exposure to the local pressure and in the first small increases in port shape there may be a decrease in flow at certain RPM.
One method of reducing the affect of local pressure interference is to radius the edges of the port so that some of the velocity is spent holding back the local pressure. A poor way to explain it I admit.
So, you see a large radius on intake ends of induction systems. You see exhaust megaphones on tuned exhaust systems (where sound is not restricted).
At very high speed the long side of a port may be flowing most of the charge. When you look into the runner you cannot see the short side. So if you were an air molecule at near sonic velocity, would you want to go in a straight line or go around the short side and through the bridge of a bridge port?
So nearly a thousand of those items is how the port being blocked by the rotor can slow the charge and increase its pressure at certain points and then the rotor sort of sitting in the way guides some flow through the bridge port or around the short side until it starts to move out of the way.
So, the short side will flow better if the radius around the the port is uniform to avoid changing the velocity, and has less than a polished finish. Note that a slightly rough finish adds to boundry layer energy and that decreases pressure along the surface, and that helps hold the flow along that surface. Bournuli again.
Along the long side there is little requirement for the same rough surface, since Newton is wanting to maintain the straight line flow. So when you add a bit of a radius to the long side, that little bit of material removed it in the direct path of the flow you want to improve. It reduces the venacontracta in that area. I polish that area up like chrome.
Everything affects everything. Grinding on anything at the junction of port and sealing surface changes port timing. It changes charge velocity. It changes local interference. It changes pulse tuning in the runner. It changes mixture suspension.
It may change overlap. It alters exhaust requirements. It alters exhaust tuning. It changes exhaust flow requirements.
Everything means everything.
For flow bench work, you need to build a setup that has a housing and one iron with your flow bench sucking on the exhaust port (for exhaust port work) and a piece of a rotor with the apex seals installed. Always have the test done at the same rotor angle that has the whole port uncovered. Have the inlet air enter though a big hole in the rotor face. Cover the housing with Plexiglass and tape in bits of string so you can watch what the flow is doing. Correct to sea level/temp and borometer after each test. And of course flow depression (how much suck in inches of water). If the bench has no levels built into it. Bring your own and level it before each use.
Most of the flow is done before the port is fully open, as (with a good flowing exhaust system) initial flow is supersonic and there will be a short period when there is negative pressure in the chamber. Note that there will generally be two RPM where the engine is over 100% VE on the dyno.
So what the port looks like above about 3/4 of full open has little affect in a street engine. (this is NA stuff. I don't know **** about turbos) So I radius the open line and the sides and leave the top close to stock.
Read Paul Yaws tech series until you can recite them on command.
Just 12,000 plus items left to go over.
About the picture....Breath in........................
Lynn E. Hanover
B
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[/quote]
Because the higher the flow velocity, the more pronounced the venacontracta.
There are just 13,000 (I counted them) things to consider when thinking about changing any port or port/runner combination.
The best way to see this and many more of the problems of flow is to go to a small airport on a cool misty morning and watch as a plane warms up. The high humidity will flash to water vapor as it passes through propeller and you can see clearly what happens to the stream of air after it passes through the propeller.
The flow is accelerated, yes? And Bournuli says that a velocity increase yeilds a pressure decrease, yes? So the flow along the cowl is compressed as local air pressure is now higher than the flow and squeezes in along the fuselage.
So so in the engine, the flow enters the cavity through your sharp edged port at high velocity. The local air pressure in the cavity closes in on the entering flow and chokes it down to a dimension smaller than the port shape. Enlarging the perimeter of the port, increases the exposure to the local pressure and in the first small increases in port shape there may be a decrease in flow at certain RPM.
One method of reducing the affect of local pressure interference is to radius the edges of the port so that some of the velocity is spent holding back the local pressure. A poor way to explain it I admit.
So, you see a large radius on intake ends of induction systems. You see exhaust megaphones on tuned exhaust systems (where sound is not restricted).
At very high speed the long side of a port may be flowing most of the charge. When you look into the runner you cannot see the short side. So if you were an air molecule at near sonic velocity, would you want to go in a straight line or go around the short side and through the bridge of a bridge port?
So nearly a thousand of those items is how the port being blocked by the rotor can slow the charge and increase its pressure at certain points and then the rotor sort of sitting in the way guides some flow through the bridge port or around the short side until it starts to move out of the way.
So, the short side will flow better if the radius around the the port is uniform to avoid changing the velocity, and has less than a polished finish. Note that a slightly rough finish adds to boundry layer energy and that decreases pressure along the surface, and that helps hold the flow along that surface. Bournuli again.
Along the long side there is little requirement for the same rough surface, since Newton is wanting to maintain the straight line flow. So when you add a bit of a radius to the long side, that little bit of material removed it in the direct path of the flow you want to improve. It reduces the venacontracta in that area. I polish that area up like chrome.
Everything affects everything. Grinding on anything at the junction of port and sealing surface changes port timing. It changes charge velocity. It changes local interference. It changes pulse tuning in the runner. It changes mixture suspension.
It may change overlap. It alters exhaust requirements. It alters exhaust tuning. It changes exhaust flow requirements.
Everything means everything.
For flow bench work, you need to build a setup that has a housing and one iron with your flow bench sucking on the exhaust port (for exhaust port work) and a piece of a rotor with the apex seals installed. Always have the test done at the same rotor angle that has the whole port uncovered. Have the inlet air enter though a big hole in the rotor face. Cover the housing with Plexiglass and tape in bits of string so you can watch what the flow is doing. Correct to sea level/temp and borometer after each test. And of course flow depression (how much suck in inches of water). If the bench has no levels built into it. Bring your own and level it before each use.
Most of the flow is done before the port is fully open, as (with a good flowing exhaust system) initial flow is supersonic and there will be a short period when there is negative pressure in the chamber. Note that there will generally be two RPM where the engine is over 100% VE on the dyno.
So what the port looks like above about 3/4 of full open has little affect in a street engine. (this is NA stuff. I don't know **** about turbos) So I radius the open line and the sides and leave the top close to stock.
Read Paul Yaws tech series until you can recite them on command.
Just 12,000 plus items left to go over.
About the picture....Breath in........................
Lynn E. Hanover
05-11-2005, 10:24 AM
#47
Senior Member
Join Date: Nov 2004
Location: Europe, Belgium
Posts: 147
[quote name='Old Splatterhand' date='May 11 2005, 05:14 PM']damn, killer post I can choke on for a while as non-native english speaker ;D
thanks for the detailed write up, Lynn
[/quote]
Same here, very nice post!
thanks for the detailed write up, Lynn
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Same here, very nice post!
05-11-2005, 01:59 PM
#48
Senior Member
Join Date: Dec 2003
Location: Minneapolis,MN
Posts: 500
:kungfu: