| SilverFire |
OK, So I was talking with some guys at work about exhaust systems, and it occured to me to wonder if rotaries have a minimum amount of backpressure we need to maintain for good operation/max HP. One would think less restriction = more flow = more HP, but I KNOW that isn't necessarily the case with piston engines.
I was poking around on RX7club.com, and couldn't find anything really useful. Most posts are saying more flow = more HP, but there were a number of post talking about S4 N/As needing enough backpressure. Is that purely so that the aux intake ports function or is there some other reason?
Anyway, hope you guys can solve this for me. Thanks!
Ben |
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| Mobius |
quote:
Originally posted by SilverFire
OK, So I was talking with some guys at work about exhaust systems, and it occured to me to wonder if rotaries have a minimum amount of backpressure we need to maintain for good operation/max HP. One would think less restriction = more flow = more HP, but I KNOW that isn't necessarily the case with piston engines.
I was poking around on RX7club.com, and couldn't find anything really useful. Most posts are saying more flow = more HP, but there were a number of post talking about S4 N/As needing enough backpressure. Is that purely so that the aux intake ports function or is there some other reason?
Anyway, hope you guys can solve this for me. Thanks!
Ben
With N/A's you need exhaust gas velocity to provide enough pressure to open up the 5th and 6th ports. Back pressure also helps with this. Other than that, you can run open headers and still run fine I believe. Don't take my word on it though.'
But, the sheer noise level would be monumental. |
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| McFly |
i was going to come and preach velocity:)
but you sumed it up great. |
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| Mobius |
quote:
Originally posted by McFly
i was going to come and preach velocity:)
but you sumed it up great.
Thanks. Every once and awhile the odds are I'll get something right lol. |
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| luv'n my 7 |
| you can wire the 5th and 6th ports open. mine never worked i was missing some part that opened them. I checked by putting some white grease on the plunger of the "port valve" forget what its called, and went for a drive. When i got back the grease hadn't been rubbed down the shaft of the plunger. Get what im saying. So i wired them open for a little bit. I took the car to the track and made passes both with them wired open and closed, one wired open the other closed etc..... And i didn't really see any difference in performance on the 1/4 mile. Thats my point of the day, i have no point!:D :D :D :dunno: |
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| ccthompson |
| when i got my exhaust done on my n/a i was asking around... and i was told that n/a's need a fair amount of backpressure... one exhaust place told me they did a 3" straight pipe on a n/a just a couple months prior to me coming there and they said it had a hard time firing up again after the exhaust...:dunno: |
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| red88.n/a.rx |
| on my old 86 n/a I had a ported engine with the 5th and 6th ports removed and I had headers to a single 2.5" straight pipe to a straight through muffler so there was no back pressure really and I felt that my car would of been a little faster if it had more back pressure. |
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| Mobius |
quote:
Originally posted by red88.n/a.rx
on my old 86 n/a I had a ported engine with the 5th and 6th ports removed and I had headers to a single 2.5" straight pipe to a straight through muffler so there was no back pressure really and I felt that my car would of been a little faster if it had more back pressure.
And why do you think that? |
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| SilverFire |
| Yeah, why DO you say that? I ask, because that's EXACTLY what I have for an exhaust setup. Minus the ported engine, but the rest is right. |
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