S5's make 160 stock, don't they?

I would think you could get 170 with just a good exhaust and cai.

:dunno:

i also thought all fc's were 6-port. Which ones are 4-port?

Turbo's are 4 port.

From what I understand - N/As can gain power by lessening backpressure. (i.e. True Dual Exhaust). In a turbo car you want to do the opposite. If you lose backpressure in a turbo you will lose power. If you lose backpressure in an N/A you will typically gain power.

EDIT: Correct me if this is wrong. I also assume this is why turbos have 4 ports and N/A's have 6. Yes?

Cheers,
iSP33D-for-J3SUS

That's flywheel HP, not at the wheels.

You've got it backwards. Turbo's make the most power with the least restriction (backpressure) and n/a's need some backpressure to make power/torque

Umm NO

You are Backwards, Turbos like less backpressure

Dangit! So close.

Cheers,
iSP33D-for-J3SUS :bigthumb:

325 is what the fuel system your builder told you to put in is capable of and a bit of overkill for your setup and will only cause problems unless you have a standalone EMS.

Do not BP the aux ports please. Just IMO clean the ports up add some advance shape the lips and if you want more top end power bring the P port down and possible close it a little bit latter if you want. Or do a real BP on the motor. Anything drastic like a real BP or later closing I suggest a new designed intake manifold. If you are going to continue to make power run a fuel controller or EMS and true duels if you can afford it. That should be about as good as you can get without allot more money for a nice running NA. N2O is always a cheep choice you can consider.

No back words.

NO car needs BP no car likes BP. BP is always bad!

However S4 NA's have the 6pt setup to utilize BP found in OEM system. You will make the most power by converting the AUX ports to another style of opening and removing BP from the system but while retaining the highest amount of velocity from the exhaust

ive heard of 170 to the wheels with an S5 engine, exhaust, intake, and standalone.

You just used the same acronym for two different sets of words. :)

BP = Bridge Port
BP = Back Pressure

LOL

That's because I am gangster

oohh ok i got wat u mean with the 325whp..
and as for back pressure with most cars turbo = less back preasure the better. n/a = more back pressure less hp but more torque to an extent..

Back pressure NEVER makes torque. Back pressure is ALWAYS the enemy! Period. The thing that many people fail to think about is flow and velocity. Yes you want flow. In a perfect world you want a pipe that flows a proprtionate amount of air to the engines needs. At lower rpms the engine flows less air. Velocity in the exhaust stream is important in making power as inertia will help pull more gasses along the pipe between power pulses. If you make the pipe too large you decrease this effect and hurt power. More or bigger is not always better. This includes with porting. Too many people go too large and this is especially true on exhaust ports.

Why then does a smaller pipe make more low end power than a larger one? It's not backpressure. It's flow! A pipe of any given size can only flow so much air with so much restriction. When testing this on a flowbench we need to determine a base pressure. It's worthless to state any flow level in cfm without also having a reference pressure. Let's say pipe A flows 300 cfm and pipe B flows 200 cfm. From looking at it we'd come to the logical conclusion that pipe A flows more. Are we sure? Were they tested at the same reference pressure? What if pipe A was tested at a reference pressure of 28" H2O and pipe B were tested at a reference pressure of 14" H2O? If we tested them both at 28" H2O, pipe B would actually flow closer to 400 cfm (maybe not exactly but you get the idea). How would you know?

I needed to tell you that so my example would be a little bit clearer when it comes to flow. Keep in mind that I'm making all of these numbers up but do assume that they are all at the same reference pressure.

Let's say a 2" pipe flows 100 cfm, a 2.5" pipe flows 200 cfm, and a 3" pipe flows 300 cfm. More is better right? Is it? Is the 3" pipe really a restriction? What if the engine at 8000 rpm's only flows 200 cfm? Was the 3" pipe really better? Both it and the 2.5" pipe could flow the required amount of air but the 2.5" pipe would have higher velocity inside and would make more average power. Yes going larger kills low end power. What about going smaller? Let's say we change our pipe down to a 2" pipe. We can already tell that top end power is going to suffer. This is because we have too much backpressure. Remember that backpressure is always a bad thing. Let's say our engine flows 100 cfm at 5000 rpm. We can see that our pipe would be sized to flow the perfect velocity at this rpm. This means that average airflow through the pipe is also faster on average below this point than in a larger pipe. More velocity is more power. Velocity is what makes power. Once our pipe becomes a restriction (wahtever that rpm may be), the effort required to squeeze and speed up the air going through the pipe is greater than the gain from having higher velocity and power starts falling. This car would have more power to about 5000 rpm than the car with the larger pipe but it wouldn't have the top end power. Yes it has a smaller pipe and yes that pipe is adding backpressure. But it only does it above 5000 rpm yet low end was increased. This is because it wasn't the backpressure at all that was making better low end power. It was velocity!

Remember I made these numbers up but the example is sound. There is more to exhaust tuning than this of course but I was merely tryling to dispell the whole backpressure and low end torque misconception.

Keep true duals OFF of bridge or peripheral port motors if you want to get max power out of them. Yes you'll make power on them with true duals. Just not nearly as much as a proper collected system can.

Hmm... Just as a point of interest guys RB claims a 53% increase in horsepower on an '85 6 port 13b when you install their Dell'orto carburetor, two piece manifold and road race exhaust.

That equals 206hp at the fly
Assuming a 50% BS factor thats still 162 hp N/A on box stock internals + whatever you can get out of ignition, porting etc.

Just thought I'd stir the pot a bit :)

Oops correction on the above ^^^ Here is a quote from the original RB catalog:

Dellorto Intake System Kit (Non-Ported Engine) 984-85 GSL-SE RX-7(6-Part Induction)



The Dellorto Intake System Kit utilizes your original stock 6-port induction lower intake manifold, complete with the 6-port valves and actuators, to retain the excellent low speed torque and good mileage characteristics that make the 6-port induction something special among street rotaries. The kit contains a cast aluminum upper manifold, a modified Dellorto 48 DHLA carburetor,a large, cleanable K&N filter element and cannister, linkage and gaskets.When tested on a stock 13B 6-port engine, the combination of this intake system, our header, our Power Pulse Presilencer, and our Prima Flow Muffler boosted the peak power from a stock135 to 177 HP! This kit includes all the hardware necessary to install the system on a Mazda automobile, including metering oil pump linkage,vacuum source for the brake power assist unit, and cruise control connections, but eliminates all emission control fittings. Throttle response and driveability are outstanding, and gas mileage is approximately equal to stock for equivalent driving. The intake system comes completely assembled to help assure quick, easy installation.


The 53% gain was on a 12a engine w/ similar extras.

ahh shit.... here we go with the scientific reasonoing.

#1 little secret i will tell you is scientific reasearch is not always as on the dot as most of us would like to think. my most recent delve into this subject was on a truck with lugnuts that were LH threaded on one side and RH threaded on the other side, i'm sure someone had scientific reasoning to back that one up as well. smaller pipe does increase velocity but also does create a small amount of backpressure.

most guys straight out of college with too much time on their hands always tend to think they are right and will never admit to being wrong. personally i don't care either way.

and no i couldn't stand to read the whole thread or replies.

Most of the times RotaryGod is correct, Most of the time :spew:

IIRC the Mazda MPV produced 155HP @ 4900 RPM and 185lb-ft tq @ 3950 RPM with the same tranny and a 3.0L V6. He shouldn't have a problem with the auto tranny.

And that has what to do with the FC's auto tranny? :dunno:

well, I didnt see the dyno run or anything, but I saw the motor itself and heard the beast run. Ito has a ported (forget what type of port) 6 port with a carb on it that makes 230 and sounds really nasty, in an incredible way. I imagine with just a mild port, if you tuned the intake and exhaust (runner sizes AND length AND plenum volume), and went with a stand-alone (for the price of a good fuel controller you could get a megasquirt kit to completely control fuel and spark and any other features) to lean out the map, you could get close to 200 after some tuning

Same transmission.

:rolleyes:

Well that explains that. Now I know. :)

:ugh2:

God forbid I ask a question that involves non-FC specific information. :rolleyes: