I know this topic has been convered in a round-about manner a million times before, but I'm looking for quick definitive answers.

I have a '91 FC3C with 85k on the current motor... runs great, but is just a little slow for my taste. I would like to know from the community out there what is the EASIEST, CHEAPEST way to get more power out of it. Ideally, I would like to get 250+ HP, but I would settle for 200+. I have read a lot about the TII conversion, but have heard that the parts are VERY hard to come by for an s5. I have seen tubo conversions on NA motors, supercharger kits, blowers, better exhaust, etc. No one though, seems very good at comparing all of these options together. (Everyone has different goals, ya know?) The point here, is that I don't care about having a non-bastardized engine (i.e. the N/A>turbo conversion is not out of the question). It doesn't have to look pretty, it just has to get me more power.

Any thoughts?

 

Nitrous.

 

The most you will ever get out of a streetable NA motor is around 200hp; more than that and you will either need forced induction, very large ports -- which aren't typically very streetable, or some sort of injection (eg. nitrous). If you just want to get some more power out of your current motor, and perhaps speed up your acceleration, there's a few basic upgrades you could perform first:

- Lightweight Flywheel - Not an actual power gain, but it will greatly improve your acceleration and throttle response, the car will rev much faster and more freely. Racing Beat's Lightweight Steel Flywheel is perfect, a good deal lighter than stock but still streetable)

- Strip All Emissions Equipment (aka. Rat's Nest) - On your car, you will need to run an S4 harness after doing this, but you should notice a nice difference in fuel delivery and throttle response.

- Remove Secondary Throttle Body Butterflies - Improves throttle response and air flow.

- Headers + Header-Back Exhaust - Racing Beat makes great headers, and you can get a really nice full custom header-back exhaust made from mandrel bent stainless steel piping. Single 2.5" would give you the best flow, but many people opt to go with the dual setup, it's up to you.

- Cone Filter + Intake Piping - Just freeing up some ariflow, helping the car to breathe a little better.

- Remove 6-Port System or Use Pineapple Racing 6-Port Sleeves - Again, improves airflow for greater high-end HP. You will lose some low end torque, but it's a rotary, who cares. The high end HP gains will make it well worth while.

These are just some things you can do to make your NA motor a little faster and more responsive. If you want to be up in the 200hp range you're going to need to port and/or turbo/supercharge your motor. If that's what you want, you may want to look into forced induction now, and plan your mods accordingly... Here's a rundown on that...

The TII Swap: This is simply putting a TII motor in an NA car. They're used because they were built for turbocharging, they have lower compression rotors to handle the additional air (and subsequent fuel) that a forced induction system will feed them. 13B-TII motors are capable of putting out some fairly large HP numbers, 400+ in a streetable car is quite reasonable. All you really need to get big numbers out of them is a larger turbo, wastegate, bov, boost controller and fuel computer, possibly some bigger injectors, intake and exhaust.

NA-Turbo: This is obviously turbocharging an NA motor. It has higher compression rotors which means you can make a lot more power on lower boost (350+ hp on ~10psi is quite realistic). A factory S4/S5 Turbo would be more than adequate for this task. This build is appealing because you can make fairly large HP numbers (400+) on relatively low boost, and it would have a lot flatter torque curve, wit ha lot more at the low end, over a TII. Because of the higher compression rotors however, there is a limit to how much boost can be run (probably around 14psi safely), and as such, how much HP it will give.

NA-Super: The advantage here is that a supercharger is basically spooled off idle. There's no turbo lag. These can be run successfully to make some pretty decent HP numbers, with tons of low end torque. They do have their limits though as they're only really good to boost low end torque and hp, and run out of steam up high where the rotaries like to be.

If you're wondering about my own setup, I have an S4 NA Streetport with all of the above listed mods, estimated power is around 185-190rwhp (according to the GTech anyways) and I am going to be turbocharging it over the winter (S4 Turbo).

 

Or, yeah, just bolt a big huge bottle of nitrous in.

 

Yeah, just fill your tank with nitrous and get a HP fuel pump LoL... Thats safe.
Upgrade your injectors and/or get a new fuel pump. Rerun the wires to the fuel pump. That gave me a fair amount of power... Port your motor, too. I found that to be hte best source of power ever!
BUT FIRST, intake and exhaust. Run 2.5" piping from a stock header to stock mufflers with nothing inbetween and you will be fast

 

I've read numerous places that if you did upgrade to a turbo you would have to use a 93 octane. Looks like you already got great advice here...

 

in this forum is the time slips and dyno time, Judge Ito posted a thread about an na with around 200.73 rwhp or so, read it, it requires nitrous though.

 

thats because its a fact, and its not 93 octane, its the highest octane possible. i'd go into why but you can search for the answer

 

damn it, i can never get all my thoughts together when i post, i was about to tell you that you bought the wrong car to make fast. you bought a convertible, its a convertible, not a coupe, enjoy the ride.

 

Any turbo car pretty much requires 93 octane at least. Anything less and you'll detonate, even with those goofy trailing plug eliminator things.

 

"damn it, i can never get all my thoughts together when i post, i was about to tell you that you bought the wrong car to make fast. you bought a convertible, its a convertible, not a coupe, enjoy the ride."

When ever you are ready you can race my vert/t2 and then tell me its the wrong car to make fast.

 

thats different man thats a TURBO vert. the n/a verts is the LAST car to try and make quick. Unless he does a trubo swap, there really is no point. When my half bridgeported supercharger project is over, if im in your area i will give you a call.

 

Any RX-7 has the potential to be fast, I don't care if it's a convertible. Try and tell me a 300rwhp Turbo-NA Convertible will be slow, or even a 200hp Half-Bridge NA Vert.

 

There are only losses when removing the aux ports. Anyone that thinks you will gain any HP by removing them has no clue or had non functioning aux ports. The only way to get any gains by removing the aux ports is to do porting.

 

now your talking going stand alone....N/A ecu and a half bridgeport don't go together

easiest way would be, a heavy street port, intake, port all your manifolds out a bit, straight pip exhaust, and a bottle of nitrous

 

Depends. Define streetable. For me, streetable means peripheral port. For you, this may be different.

Not necessarily true. Ligther flywheels will cost you "off the line" as they have less momentum (stored energy). Yet they are better for things like road racing and autocross because they allow the engine to rev more freely and offer crisper throttle response.

Difference in fuel delivery and throttle response? Huh?

You'll definitly notice a difference in throttle response. It will be worse, and probably more prone to hesitation.

But can cause hesitation.

Make sure to add a cold air box to that, otherwise the gains from the filter may be negated by the hot air the engine is now breathing.

Absolute and complete BS. There is no gain up to by removing the sleeves unless your 6 port system wasn't working properly before.

Depends on the turbo. Not on the stock turbo.

Not true. You can push as much boost as you want, as long as fuel, ignition and air temperature are properly managed.

On my turbo-NA, I have full boost from 1200 RPM up.

 

10psi on the stock turbo on a high compression is ~250.

 

 

Well for throttle response stuff.

It's small but I was amazed after I disconnected the OMP rod. It made it touchier to my inputs.

When I removed my stock fan and went efan I did notice a little quicker response due to the removal of the rotational part.

All these have ups and downs though.
Have to go premix and make a really good efan shroud to keep up w/ stock cooling levels.