Streetable pp engine.
01-13-2010, 03:39 AM
#22
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Join Date: Jul 2002
Location: Portland, OR
Posts: 2,467
02-13-2010, 08:16 PM
#23
Senior Member
Join Date: Jun 2004
Posts: 524
Well, if you think about it, if engine vacuum is really low, like 4" of mercury or so, then the engine is almost running the equivalent of wide open throttle, right there at idle.
For a given exhaust system, a peripheral port exhaust won't be much louder than a street port when under the same load. The trick is, at idle and such the peripheral port is struggling to stay running so it's effectively under a lot of load.
A lot of noise comes from the intake tract at higher throttle openings, and there isn't much you can do about that.
I drove one around like a normal car, the only difference was like you noticed, you have to be accelerating or decelerating, if you just try to cruise then it shakes the fillings out of your teeth. It was quite oderiferous at stoplights.
02-17-2010, 02:45 PM
#24
Senior Member
Join Date: May 2002
Location: California
Posts: 22,465
Well, if you think about it, if engine vacuum is really low, like 4" of mercury or so, then the engine is almost running the equivalent of wide open throttle, right there at idle.
For a given exhaust system, a peripheral port exhaust won't be much louder than a street port when under the same load. The trick is, at idle and such the peripheral port is struggling to stay running so it's effectively under a lot of load.
A lot of noise comes from the intake tract at higher throttle openings, and there isn't much you can do about that.
I drove one around like a normal car, the only difference was like you noticed, you have to be accelerating or decelerating, if you just try to cruise then it shakes the fillings out of your teeth. It was quite oderiferous at stoplights.
For a given exhaust system, a peripheral port exhaust won't be much louder than a street port when under the same load. The trick is, at idle and such the peripheral port is struggling to stay running so it's effectively under a lot of load.
A lot of noise comes from the intake tract at higher throttle openings, and there isn't much you can do about that.
I drove one around like a normal car, the only difference was like you noticed, you have to be accelerating or decelerating, if you just try to cruise then it shakes the fillings out of your teeth. It was quite oderiferous at stoplights.
but at the same time it fires right up and will idle @1100rpm cold with no choke...
02-24-2010, 01:11 PM
#25
Member
Join Date: Mar 2004
Posts: 37
Would using the 2nd gen n/a rotor housings with the exhaust diffuser to dull the exhaust sharpness tone be do-able? How much restriction does that diffuser really create?
Also how about a smaller intake port to increase intake velocity and reduce some overlap. Say 38mm?
Also how about a smaller intake port to increase intake velocity and reduce some overlap. Say 38mm?
03-13-2010, 01:42 PM
#26
Senior Member
Join Date: May 2002
Location: California
Posts: 22,465
Would using the 2nd gen n/a rotor housings with the exhaust diffuser to dull the exhaust sharpness tone be do-able? How much restriction does that diffuser really create?
Also how about a smaller intake port to increase intake velocity and reduce some overlap. Say 38mm?
Also how about a smaller intake port to increase intake velocity and reduce some overlap. Say 38mm?
in moving houses, i got a chance to drive mine some more. mine is MFR port style. smaller ports would probably help its manners, but really its not that bad though.
noise isn't really even too bad, the thing is really that the college kids have never seen a car that isn't domesticated. its like having a tiger in a herd of veal cows....
05-08-2010, 03:04 PM
#28
Senior Member
Join Date: May 2002
Location: California
Posts: 22,465
i've been running a pacesetter into a 3" glass pack into a borla. the new system is RB header, into 3" by the axle into the same borla
05-15-2010, 08:55 AM
#29
Fabricator
Join Date: Jan 2004
Location: Central Ohio (Hebron) Zephyrhills Fla.
Posts: 1,322
Would using the 2nd gen n/a rotor housings with the exhaust diffuser to dull the exhaust sharpness tone be do-able? How much restriction does that diffuser really create?
Also how about a smaller intake port to increase intake velocity and reduce some overlap. Say 38mm?
Also how about a smaller intake port to increase intake velocity and reduce some overlap. Say 38mm?
I found that the Periphery port engine was more tractible than the bridgeported side port engine. The Pport we drove around like a stock car. The side port had to be towed around the paddock. This was with Mandevile modified housings with huge rectangular ports and very late closing. It had no power at all at low speed. It had poor hot starts and very poor starting in cold weather. Like propane torch on the intake manifold cold starting.
Most streetable designs had small periphery ports, and had good performance.
If you port it so it runs great at 10,000 RPM it may not be any fun at all below 6,000 RPM. When it comes to poor low speed performance, nothing beats a Pport. We usually ran a 60 MPH first gear, and if the pace lap was slow we were screwed on the start. So on short tracks we had a 5:12 rear gear for the Speedway quick change.
An intake port with about 30% more area than the stock exhaust port and about the same shape, should work fine.
Two features of the Pport combine to ruin low speed (streetable) performance. Just like a late closing intake valve in a piston engine, the late closing intake port in a rotary determines low speed performance.
Later closing means that the piston, or rotor is past bottom dead center and the cylinder or chamber volume is decreasing, so some of the intake volume is pushed back into the intake system and is not trapped in the chamber to be compressed. So, less volume being compressed into a fixed headspace means lower effective compression ratio.
The engine (in effect) has become smaller in displacement, has it not?
At high speed the mass of the inlet gasses over-fill the chamber and are then trapped to be compressed. Volumetric efficiencies in excess of 100% are possible. The engine has become larger in displacement (in effect) has it not?
Early intake closing does the reverse at lower engine speeds. Traps more volume in the cylinder or chamber after port closing. More volume is compressed into the the fixed headspace, and the effective compression ratio goes up. The engine gets larger in displacement (in effect). Heat of compression is higher, and gets you better hot and cold starting performance. Heat of compression is higher and fuel vaporizes more effectively. Of course high RPM power is reduced.
The second problem is the overlap. Where intake and exhaust ports are open at the same time. The unobstructed ports flow well in both directions, so any pressure developed in the exhaust system will cause spent and some times still burning gasses to gleefully flow right back into the engine and up into the intake port. Ouch!!!!
One way to reduce this problem is to use a bit smaller primary header tubing diameter, and longer runs before the collector. This gives higher velocity in the header, and puts each pulse further along the tube per unit of time. I would try running both tubes to the rear of the car before collecting as in early RX-2 and 3 racers. 102" of primary was the rule.
A well designed muffler is important as well. Less heat damage will be seen with the muffler at the end of the system. Mechanical damage may be increased. The hammering that rotaries do so well.
So don't move the exhaust port closing point up any at all. You could go a bit wider, and open a few degrees earlier if you just cannot put the die grinder down. Or,leave it stock. Keep the intake open point as late (high)as possible. And intake closing point as early as is possible. That means a short wide intake port. Less is more when it comes to good low end performance. The periphery intake port is much more effective than any side port or even a bridge port, so street performance will be great.
Lynn E. Hanover
05-28-2010, 02:45 AM
#30
Junior Member
Join Date: Jul 2008
Posts: 28
I found that the Periphery port engine was more tractible than the bridgeported side port engine. The Pport we drove around like a stock car. The side port had to be towed around the paddock. This was with Mandevile modified housings with huge rectangular ports and very late closing. It had no power at all at low speed. It had poor hot starts and very poor starting in cold weather. Like propane torch on the intake manifold cold starting.
Most streetable designs had small periphery ports, and had good performance.
If you port it so it runs great at 10,000 RPM it may not be any fun at all below 6,000 RPM. When it comes to poor low speed performance, nothing beats a Pport. We usually ran a 60 MPH first gear, and if the pace lap was slow we were screwed on the start. So on short tracks we had a 5:12 rear gear for the Speedway quick change.
An intake port with about 30% more area than the stock exhaust port and about the same shape, should work fine.
Two features of the Pport combine to ruin low speed (streetable) performance. Just like a late closing intake valve in a piston engine, the late closing intake port in a rotary determines low speed performance.
Later closing means that the piston, or rotor is past bottom dead center and the cylinder or chamber volume is decreasing, so some of the intake volume is pushed back into the intake system and is not trapped in the chamber to be compressed. So, less volume being compressed into a fixed headspace means lower effective compression ratio.
The engine (in effect) has become smaller in displacement, has it not?
At high speed the mass of the inlet gasses over-fill the chamber and are then trapped to be compressed. Volumetric efficiencies in excess of 100% are possible. The engine has become larger in displacement (in effect) has it not?
Early intake closing does the reverse. Traps more volume in the cylinder or chamber after port closing. More volume is compressed into the the fixed headspace, and the effective compression ratio goes up. The engine gets larger in displacement (in effect). Heat of compression is higher, and gets you better hot and cold starting performance. Heat of compression is higher and fuel vaporizes more effectively.
The second problem is the overlap. Where intake and exhaust ports are open at the same time. The unobstructed ports flow well in both directions, so any pressure developed in the exhaust system will cause spent and some times still burning gasses to gleefully flow right back into the engine and up into the intake port. Ouch!!!!
One way to reduce this problem is to use a bit smaller primary header tubing diameter, and longer runs before the collector. This gives higher velocity in the header, and puts each pulse further along the tube per unit of time. I would try running both tubes to the rear of the car before collecting as in early RX-2 and 3 racers. 102" of primary was the rule.
A well designed muffler is important as well. Less heat damage will be seen with the muffler at the end of the system. Mechanical damage may be increased. The hammering that rotaries do so well.
So don't move the exhaust port closing point up any at all. You could go a bit wider, and open a few degrees earlier if you just cannot put the die grinder down. Or,leave it stock. Keep the intake open point as late (high)as possible. And intake closing point as early as is possible. That means a short wide intake port. Less is more when it comes to good low end performance. The periphery intake port is much more effective than any side port or even a bridge port, so street performance will be great.
Lynn E. Hanover
Most streetable designs had small periphery ports, and had good performance.
If you port it so it runs great at 10,000 RPM it may not be any fun at all below 6,000 RPM. When it comes to poor low speed performance, nothing beats a Pport. We usually ran a 60 MPH first gear, and if the pace lap was slow we were screwed on the start. So on short tracks we had a 5:12 rear gear for the Speedway quick change.
An intake port with about 30% more area than the stock exhaust port and about the same shape, should work fine.
Two features of the Pport combine to ruin low speed (streetable) performance. Just like a late closing intake valve in a piston engine, the late closing intake port in a rotary determines low speed performance.
Later closing means that the piston, or rotor is past bottom dead center and the cylinder or chamber volume is decreasing, so some of the intake volume is pushed back into the intake system and is not trapped in the chamber to be compressed. So, less volume being compressed into a fixed headspace means lower effective compression ratio.
The engine (in effect) has become smaller in displacement, has it not?
At high speed the mass of the inlet gasses over-fill the chamber and are then trapped to be compressed. Volumetric efficiencies in excess of 100% are possible. The engine has become larger in displacement (in effect) has it not?
Early intake closing does the reverse. Traps more volume in the cylinder or chamber after port closing. More volume is compressed into the the fixed headspace, and the effective compression ratio goes up. The engine gets larger in displacement (in effect). Heat of compression is higher, and gets you better hot and cold starting performance. Heat of compression is higher and fuel vaporizes more effectively.
The second problem is the overlap. Where intake and exhaust ports are open at the same time. The unobstructed ports flow well in both directions, so any pressure developed in the exhaust system will cause spent and some times still burning gasses to gleefully flow right back into the engine and up into the intake port. Ouch!!!!
One way to reduce this problem is to use a bit smaller primary header tubing diameter, and longer runs before the collector. This gives higher velocity in the header, and puts each pulse further along the tube per unit of time. I would try running both tubes to the rear of the car before collecting as in early RX-2 and 3 racers. 102" of primary was the rule.
A well designed muffler is important as well. Less heat damage will be seen with the muffler at the end of the system. Mechanical damage may be increased. The hammering that rotaries do so well.
So don't move the exhaust port closing point up any at all. You could go a bit wider, and open a few degrees earlier if you just cannot put the die grinder down. Or,leave it stock. Keep the intake open point as late (high)as possible. And intake closing point as early as is possible. That means a short wide intake port. Less is more when it comes to good low end performance. The periphery intake port is much more effective than any side port or even a bridge port, so street performance will be great.
Lynn E. Hanover
wow awesome lyn what sort of intake and exhuast timing would be good for him to use he could use almost factory open and close on the intake could he not?