RixRotary7

I have a 1985 RX-7 GS (12A engine) with a Racing Beat Full Exahust. Which option would you recommend, supercharge the car with a Atkins blower or street port it? Also, when people refer to "porting" their car, are they talking about the exhaust and the intake? What would be the benifit to porting the intake rather than the exhaust or vice versa? Thanks for your time.

RixRotary7

Also, what would be the cost difference and where could I have my porting done at?

MRGSL-SE

go supercharge.... its different....

Jeff20B

iTrader: (13)

Do both, er all three. Intake, exhaust and supercharge.

mar3

iTrader: (8)

Do neither...
.
.
.
.
nnnnnnaaaaaawwwwwwsssssssssssss!!

SoRRoW

Is this backed by performance evidence?

The first step to acheive any power on a rotary is to go ported,now theres diffrent types of porting for your needs,

I personally dont like the Supercharger ,Figure $2200. for how much more HP?Dont think you can just slap on on and thats it,You need a bigger carb,bigger fuel pump,etc etc..

If you want to go with any type of forced induction,go Turbo,Theres 2341235235 diffrent things you can do,but theres other engine upgrades you have to do also,


First figure why and what you want to do for the car,
Is it daily driving?
How much HP do you want?
How much cash you got to spend?

REVHED

Why one or the other? Forced induction engines benifit from porting just like n/a engines do.

twigg

Dont listen to this turbo doods, Turbo is evil and will destroy ur motor much quciker. Supercharing is the way id go.


Turbo = cancer

RixRotary7

This car is going to be used on the street.

MIKE-P-28

iTrader: (1)

I think a SC is a hell of a lot of money to spend, for almost nothing... What is it like 90 hp for like $3k , screw that.. Go for the *****, blow through turbo

fatboy7

Ummm....... no, you obviously don't know a thing about either, cause each have its pros and cons. You can blow your engine just as fast with a SC as a turbo, as it all comes down to tune.

wwilliam54

Go for the port
it will cost a gasket kit and template at least
figure 90 kit + 50 in templates + 20 in grinding bits and sandpaper

2100 cheaper

you would be able to use the $$ difference on a nice side draft and RB exhuast

SoRRoW

Do a V Tec swap

81Rex6port13b

lol omg, that would be funny to see some one accualy think that is posible.

haha

sorry but thats a good one.

nlc1179

nnnnnnnaaaaaawwwwwwwsssssssss is for ****** that are too cheap to upgrade there cars the real way.
you can only have nnnnaaaawwwwsssss if you can't really do much else to help it in speed.

SoRRoW

So your saying if I used Nitrous on top my bridge port to hopefully get int he low 11s or 10s,then its *****?

Directfreak

iTrader: (2)

karism

Depends on how much you want to spend.
Do you mind a lumpy type of idle ?Does economy count?How is emissions in your area ?

think about all that.SC is alot of money for la smallish gain.There will also be extra costs involved.

SoRRoW

wtf?

Looks like extra package hanging back there

rotarygod

iTrader: (1)

Now for a completely unbiased and dignified response...

You have a 12A and want more power. Many ways to do this depending on what you want to spend, how you intend to drive the car, etc.

1) Port it. What type of driving do you do primarily? Emissions to worry about? A good streetport with proper tuning can get you close to 200 fwhp. A bridgeport depending on the size can get you up to almost 250 fwhp or so and a peripheral port can take you to around 300ish. The bigger and more radical the port, the higher and narrower the powerband becomes, the worse the emissions. Add to this worse gas mileage, lumpier idle, and the need for some serious induction, exhaust, and fuel system requirements and suddenly it can get very costly and hard to drive around at anything other than full throttle. For everyday use a streetport gets my vote in the porting department. Minor retuning of the carb with minimal other needs. Depending on who builds it you could spend as little as a few hundred dollars (build it yourself) or up to a couple thousand.

2) Supercharge it. If you are looking for a modest gain in power with great drivability on the street then this may be a good route for you. A positive displacement supercharger (roots style) such as the one from Atkins will yield you about 30% or so more power than what you have now. The beauty of a system like this is that it gives you a great boost in power throughout the entire rpm range. You'll notice immediate power when you step on the gas regardless of rpm. This is fantastic for daily street use. Some downsides are cost, gas mileage, and ultimate power potential. Cost is $3000+ and then you have to install it. Your current carb will not work properly and will have to be replaced. You fuel system will also need upgrading. As with any style of porting, gas mileage will suffer a little. Since there is no bypass valve as on an Eaton supercharger you are always under boost. More air needs more fuel and therefore worse fuel economy. If ultimate high power isn't your goal then efficiency shouldn't be a concern. A roots blower is an inefficient machine. It heats the air up greatly since compression is not internal but rather in the intake manifold. High heat, lack of intercooling, limited power potential on pump gas. Also robs power off of the crank. Very driveable though.

3) Turbo it. A turbo has the potential to provide nearly unlimited power if done properly. Prices can vary greatly depending on how you do it. It is possible to blow through your existing carb but you will need to do several mods to it to enable it to function properly under pressure. Your fuel system will need some special attention too. Also depending on how much power you want to get you need to address the subject of intercooling. It is always recommended as cooler, denser air is going to give you more power and less chance for detonation. A popular option for the 12A is to use a turbo and intercooler from a 2nd gen turbo II and then custom manufacture what is needed. Plan on still spending $2000 or so when it is all said and done. 200 hp with a good power range is very easily attainable from the setup. Money and imagination are the only truly limiting factors. A turbo will always have a degree of turbo lag though. Its not as bad as everyone makes it seem though and depending on how the system is done this could be of minimal concern. Gas mileage will suffer a little though even when not on boost since the turbo is small restriction in the exhaust.

4) Nitrous. Many RX-7 people are scared of it. There are several who swear by it and then there are others who just hate it with a passion. Many claim that the limit for potential gains is about 50-75hp on a rotary but this isn't quite true. Those who experience problems merely just bolt on a kit and go for it. Nitrous requires the same amount of attention to tuning that any turbo or supercharged car requires and in some ways more. On a carb'd car I personally (others may disagree) recommend a wet shot if you are going to use nitrous. This will always maintain the correct air/fuel mixture. Fuel requirements are extremely important here since you don't ever want it to run lean. An upgraded fuel pump is a must. Some form of progressive nitrous controller would probably be wise since it can vary the amount of nitous initially injected when it first comes on and then over a period of time (milliseconds-seconds) depending on how its set up the power could be increased. This would help save the internal seals from the added shock of instant power. As with any other form of power adder too much can be very bad. It is just as easy for the inexperienced person to blow up a turbo/superchared engine as it is to blow up a nitrous fed engine. The key is in the preparation, tuning, and real world expectations of the user. A nitrous system including the needed upgrades could run around $1500 or so initially. Remember that the bottle doesn't stay full for long. Refilling a bottle could run you $30 or so a time. This will add up over time to become a long term expense. The plus side is that you car is just as drivable as it is now with power available when you want it. The only reason your gas mileage will suffer is because you always have it floored.

5) Any combo of the above. If you add a power adder to any degree of porting then your power gain gets all that much more impressive. So do your costs.

Decide what YOU want after weighing all the options and then do it. Its your car. If someone else has a problem with it, too bad. If your engine is getting old and tired you'll probably benefit most from a fresh rebuild and port job. Adding anything else on an old engine isn't going to make it last any longer. In fact it is just the opposite. Good luck on whatever you decide to do!

mar3

iTrader: (8)

Funny what brings the peanut gallery out. Must have had a bad experience with wome....er, I mean, nitrous. I didn't think anyone still used the word, pu$$y...talk about lame and passe at the same time....

Cloud

Rotary god - show me a person who tried to tell you about using a dry kit on a carb'd application. I haven't slapped anyone in awhile.

rotarygod

iTrader: (1)

I don't know anyone who has used a dry shot on a carb. That's a good thing. There must have been someone who's tried it in a big way and regretted it. A good friend of mine has a hell of a big wet shot on his stroker 383 in his Camaro. Works beautifully.

WackyRotary

I think one other reason to avoid a super charger is the pulley ratio of the supercharger is not optimal for the whole rpm range of a rotary engine-especially a roots type like the atkins. If you gear it for the max power at low rpm for torque, you will over spin it at 7000rpm or be damn near the point you don't want it to be operating at. And if you set up the pulleys for 7000rpm operation without overspinning it, you will be sluggish at the low rpm levels. This is the problem with the old paxton supercharger kit offered for 6port engines, and it had weak brackets also. No bracket is needed with a turbo-just custom manifold.

A properly sized turbo will have both highend and reasonable lowend response torque without too much lag.

nization

Personally, from the options previously listed (turbo, supercharger, porting, and NOS) I would suggest the port first and then plan to do all options in any order, if you'd like to just go all out!