Any Peripheral Ported Street Cars Here?
12-19-04, 03:43 AM
#6
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My NSU Ro80 is a PP, from the factory. Doesn't drive yet though, waiting to be restored. Back in 68, when they were new, the Ro80's were the smoothest driving car on the market, so PP is very much streetable, but has a bit less torque and won't last as long as a side-ported engine. With modern parts, a rebuild NSU engine is expected to last about 100.000miles.
However, a race-ported PP is quite a bit different. It really depends on how serious the timing/overlap will be. I'd say: buy it. If it really turns out too racy, I'm sure it's easy enough to get it sold and buy a "normal" rotary engine. Swapping engines isn't very hard in RX-7's.
However, a race-ported PP is quite a bit different. It really depends on how serious the timing/overlap will be. I'd say: buy it. If it really turns out too racy, I'm sure it's easy enough to get it sold and buy a "normal" rotary engine. Swapping engines isn't very hard in RX-7's.
12-19-04, 03:53 AM
#7
Yeah, I'm guilty of driving 8,000 miles in a 1st gen with a peripheral ported 13B, Weber 51IDA, 4.88 gears, puck clutch -- and, yes, pulling a "half RX-7" trailer -- over a period of about 10 days (Oregon to Florida and back). Other than being way too loud (due to being a real "racing" exhaust; not intended for the street), it was perfectly streetable. A properly tuned PP13B is not peaky...mine made the same torque at 4K as it did at 9K, with hardly any variation between. It pulled the 600lb+ trailer with ease and I averaged 15mpg. 19mpg without the trailer.
The only real challenge to driving a PP on the street is managing the noise. Best power is made with an unrestricted open exhaust, but that can make your ears bleed. However, the real trick is to use a very large volume muffler as far forward as possible or, failing that, go with something slightly restrictive as a compromise. Also, the intake can be responsible for a suprising amount of the overall noise, so a sealed airbox with remote cone filter is advised.
I'm not sure I would want to civilize a race car with a PP, however. Race cars are harsh and unpleasant by nature, and it would be very hard to soften one suitably for the street. Also, real race engines tend to make very low oil pressure at low RPM and certainly have lived a harsh life on the track. If you are really lucky, the engine would have ceramic seals but carbon-aluminum seals are more likely (relatively short life span). It would be better to use it as a track car that can be driven there and back, rather than turned into any sort of daily driver, IMHO.
The only real challenge to driving a PP on the street is managing the noise. Best power is made with an unrestricted open exhaust, but that can make your ears bleed. However, the real trick is to use a very large volume muffler as far forward as possible or, failing that, go with something slightly restrictive as a compromise. Also, the intake can be responsible for a suprising amount of the overall noise, so a sealed airbox with remote cone filter is advised.
I'm not sure I would want to civilize a race car with a PP, however. Race cars are harsh and unpleasant by nature, and it would be very hard to soften one suitably for the street. Also, real race engines tend to make very low oil pressure at low RPM and certainly have lived a harsh life on the track. If you are really lucky, the engine would have ceramic seals but carbon-aluminum seals are more likely (relatively short life span). It would be better to use it as a track car that can be driven there and back, rather than turned into any sort of daily driver, IMHO.
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12-19-04, 12:11 PM
#9
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Originally Posted by rotary emotions
PP is very much streetable, but has a bit less torque and won't last as long as a side-ported engine.
Engine longevity is entirely up to the engine speeds you use, on a naturally aspirated engine. The higher you rev the lower the lifespan.
Ro80s have always had problems with their apex seals, but this isn't due to the peripheral port design, but rather NSU's lack of technology in the field. Mazdas of similar vintage also had wear problems, but Mazda largely solved that by the mid-late 70's. NSU never really had a chance.
12-19-04, 12:14 PM
#10
Old [Sch|F]ool
Originally Posted by Blake
Also, the intake can be responsible for a suprising amount of the overall noise, so a sealed airbox with remote cone filter is advised.
12-19-04, 02:04 PM
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Originally Posted by peejay
Not quite.
Engine longevity is entirely up to the engine speeds you use, on a naturally aspirated engine. The higher you rev the lower the lifespan.
Ro80s have always had problems with their apex seals, but this isn't due to the peripheral port design, but rather NSU's lack of technology in the field. Mazdas of similar vintage also had wear problems, but Mazda largely solved that by the mid-late 70's. NSU never really had a chance.
Engine longevity is entirely up to the engine speeds you use, on a naturally aspirated engine. The higher you rev the lower the lifespan.
Ro80s have always had problems with their apex seals, but this isn't due to the peripheral port design, but rather NSU's lack of technology in the field. Mazdas of similar vintage also had wear problems, but Mazda largely solved that by the mid-late 70's. NSU never really had a chance.
Yes and no. One of the problems with PP designs are the fact that the apex seals will pass big holes every time they come around the intake/exhaust. They'll be pushed in there a bit every time. This puts more stress on the seals then with a no PP one. Even if you use Renesis seals in a 13B they'll still last a bit less then in a Renesis. But indeed, NSU never really got a chance. They also weren't half as bad as people believe. About 80% of the "broken" engines came in with nothing else but carburator settings etc being wrong! Indeed, only 20% of all broken engines was really broken, and of those quite a few were screwed up due to lack of maintance (oil) etc.
12-19-04, 02:05 PM
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Originally Posted by peejay
Makes the engine sound a bit more high pitched and "whispery". Don't really have the words to describe it.
12-19-04, 02:41 PM
#13
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But the peripheral port engines don't need to rev as high to make the same power... NSU's 10A sized engine was making 120hp at 5500, which is more than Mazda's 12As made, at higher RPM. I'd think the tradeoff is a fair one, given that seal wear goes up at a greater than linear rate with engine speed.
I don't like the sound of a wide open intake, actually... it's just weird. It's anemic sounding, instead of beefy.
I don't like the sound of a wide open intake, actually... it's just weird. It's anemic sounding, instead of beefy.
12-19-04, 10:39 PM
#15
Originally Posted by Rotarx7
ive posted this pic before. This was my dads 73 pport. It was his daily driver for 4 years. He drove it to work and back, everywhere.No problems at all. Just broken axles. The ford 8.8 solved that prob though.
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