Brisky

This is out there but does anyone have experience daily driving a semi pp rotary? I got my fd at 16 and it’s been almost 2 years now that im 18 and I’ve put 45k miles on the car myself. I absolutely love it and when the rebuild comes I was going to go single with a semi pp. just wanted to see if it’s reasonable to still try to daily.

c0rbin9

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c0rbin9

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Pros:
-braps!
- +50 hp

Cons:
- compromised driveability
-reduced longevity
-single-digit MPG
- +50 hp (why is this a con? increased stress on transmission, axles, differential; driveline becomes consumable after certain power level)
-more difficult to maintain

It sounds like you like to drive your car, which is awesome. Mazda gave us a very nice package with a good mix of sportiness and practicality from the factory. It is very easy to turn your car into a compromised mess that is miserable to drive on the street, and ripping out your functioning sequential TT setup for a PP single turbo setup is the quickest way to do that.

DaleClark

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Of course you'll get a lot of opinions from us old grey hair dudes

Those types of ports are considered race ports for a reason. Zero low end, many times the power is all or nothing - like idle and full throttle, trying to drive part throttle (which is 99% of street driving) is jerky and no torque.

The other thing that you have to understand is having a TON of power isn't as useful in an RX-7. You have a lightweight car with no traction control. You can easily have a setup that just turns tires to smoke - neat but you aren't going forward.

There's a reason it's called a "street port" - it's good for a street driven car. It's the equivalent of a mild cam.

If you really want more power, the turbo is where that all comes from. A good turbo will make all the power you want. IMHO a BW 8374 is probably the perfect turbo for the FD if you go single - crazy low end power, very drivable, but easy low 400's.

Also the "brap brap" idle is fun for about a month then just gets obnoxious.

Dale

c0rbin9

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This video is an interesting illustration of the difference between an FD built for response, and one built for horsepower. Check out the driving portion:




Basically, TJ's FD is heavily ported, he drives Tommyfyeah's which is built with a much smaller port (and a smaller turbo, granted) and is blown away by the response.

Slides

Power via increased rev ceiling puts less load on the drivetrain than turbocharging bud.


If you swap in rx8 crown and pinion and get a decent tune you will probably enjoy it. I swear half the people on this forum would be better driving auto cosmos than rx7s.

I drive a diesel ute with single mass flywheel and Detroit diff and fd with os gearset and short diff gears every day, I will be running a primary bridge and single turbo when I rebuild, these bring turbo on sooner. I hate the flat spot the sequential create in the midrange, especially roll on out of a corner which is different to WOT pull from low rpm.

GoodfellaFD3S

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No.

--Ted

SETaylor

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You certainly could if you wanted to. Just keep in mind that during most street driving, you will likely not be at the proper rpm(s) to make use of that kind of porting, and you can blow the tires and you can blow the doors off of 99.9% of the stuff you'll see on the road with a properly sized single turbo. In my experience, less is more with these cars. I'm at around 310 wheel on twins and it is wild.

Billj747

Not all porting is the done the same. So you'll get greatly varying feedback here (and performance) pending on how the porting is done. It can be streetable and responsive, or it can be compromised and lose low-end.

Sgtblue

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OP, no, the heavy porting you’re suggesting is not a good idea. The single depends.
And please don’t listen to people who want to export stupidity to rationalize screwing up their cars for the street. That stupidity would likely be magnified since you’re in California with strict emissions testing and, probably, a typical teenager’s limited budget.

arghx

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Semi peripheral port requires a gazillion custom expensive things. Remember, a peripheral port (or semi peripheral, meaning a combination of side and peripheral ports) means a machine shop drilling into the rotor housings and having a custom intake manifold that can accomodate that. A peripheral port is NOT a bridge port! They're not the same thing.

Emissions aside, why not start with a single turbo? That's a big project in and of itself even if you just buy a ready made kit that bolts to the stock intake manifold, because you have to deal with a fuel system, tuning, clutch, etc.

Slides

To be fair semi-pp is pretty much plug and play these days, most of the port timing is fairly standardised or you can request it to suit, enough to port match off the shelf manifolds, of which there are several options, many people replace manifolds on side ports to balance and improve flow anyway.

It probably is worth going single turbo first if you still have compression and your water seals are intact, gives you a better point of reference. Plenty of guys in Australia daily drove large Bridgeport and PPs in R100/1300s, rx2s, rx3s etc with oversized Weber carbs and loved it, some still do. If you are smart about manifold selection, injectors and mapping you can make a modern high overlap engine a lot more drivable than those, and if you don't overdo close timing you don't loose your bottom end like a large secondary extend/bridge or full PP.

TeamRX8

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still waiting for ripvanwinkle to wake up and do it properly with an actuated valve arrangement that doesn’t open them until over 5000 rpm … so much technology, so little obviousness … c’mon, even the Renesis intake was designed almost 20 years ago and many people still to this day just don’t get it.
.

SwappedNA

iTrader: (1)

I'll echo what Dale Clark said here. Street ports are called street ports for a reason. Anything above that you compromise drivability, reliability, & longevity. Look what goes into a Bridgeport or peripheral port. The idea of these ridiculous ports made more sense decades ago on N/A rotaries built for race use because that was the only way of gaining a decent amount of power. Anything you'd gain by doing this would likely be the equivalent of a few pounds of extra boost. Don't do it.

Edit: Also just noticed you are in California. No way you would pass smog with that.

j9fd3s

iTrader: (3)

i've never driven a Semi PP, although i do own a car with a full PP. the mild cam thing is actually right on the money, the full PP is like a 320 degree cam, it is something that you are going to notice....

the full PP is more streetable than you'd think, but the semi PP is quite different. there is a lot of scope to end up with the Semi PP being less streetable than the full PP setup...

BLUE TII

iTrader: (9)

Most semi p-port rotaries will have worse driveability than a MFR spec full P-port because there are more compromises in most semi p-port set-ups AND a turbo to boot.

Using stock style LIM and long runner intake is terrible for driveability on full bridge (pri & sec) and semi P-port engines.
The high overlap rotaties want each rotors intake runners separate and much sorter runners since you are now using helmholz frequency (negative pressure from initial pressure wave exiting runner) and not the positive wave continuing from one runner to the other rotors port.

Using a 4150 4 barrel intake, a newer Projay intake or even stock upper intake cut down and modified to a plenum all will help.

Then on top of intake runner configuration you have the turbo.
The turbo increases exhaust port back pressure which affects high overlap porting greatly and you also have turbo compressor surge line and powerband dictated by turbo rpm affecting driveability.