MrFC3S

I know this has proly been anwsered a million times before, but what are some effective low and high cost ways of tunning an NA S4 13B?. I know that you can port an intake but thats all I know... you can't just add higher compression apex seals or rotars or somthing right? just trying to come up with some good ideas...

88IntegraLS

Best mod for NA hands down is porting, but best bang for buck is a header, by a big margin. Then comes the cat and cat-back exhaust. Search for peoples' opinions on their favorite exhaust setup.

andrew lohaus

the only way to raise compression would be to use s5 n/a rotors.

on the cheap and/or easy: FULL TUNE UP, TB mod, intake manifold porting, cold air intake, exhaust, weight and accesory reduction.

expensive and/or hard: port the engine, use s5 rotors and/or intake manifolds, SAFC, or standalone EMS.

searching any of those will give you some good ideas.

if your engine is already in good shape, leave it alone and go for the easy/cheap stuff. if its tired (low compression) and you have the means, rebuild it with a port.

unless you are going for every last bit of power and have the money ($500+ for the whole rotating assembly) the s5 internals arent much of an improovement for the $$$.

also read the "beefy n/a" thread in the second gen archive.

scathcart

Majorly disagree here, sorry.

Replace the header, leave the rest of the exhaust stock... almost no gains, but huge increase in noise.

Replace the exhaust with straight pipes, leave the stock manifold... best bang for buck. Then, replace the stock manifold with a header... power/torque gains are minimal, but noise skyrockets.

I state this from back-to-back testing datelogging rpm versus time in fourth gear pulls.

A header is worthless on a stock engine. All it does is amplify noise. If you haven't tune your intake track, intake port, and exhaust ports, why try tuning exhaust pulses.

It is a completely different ballgame when the engine is ported.

I make this statement about both RB headers and others.

88IntegraLS

Yep I put my header on a medium streetported NA and got .8 sec in the 1/4 mile from it, stock cat and cat back behind it. I didn't do it on a stock rotary so I stand corrected.

peejay

My stockport runs over a second quicker than stock and all that's been done to it is a header.

Yeah, worthless, right.

Well, it *is* a carbed 12A and not some FC thingie, oh wait a friend of mine was getting good times with his FC with just a header and a S-AFC to un-richen the engine (Mazda goes to 10:1 over 3800, this is baaad for power!)

88IntegraLS

That's the other thing I was thinking, the FC's have the stock ECU which might go lean on the extra airflow. My S4 certainly needed a bit of fuel added in when I got my SAFC and started playing around with tuning it. Another variable would be the exhaust diffusers which I removed but stock engines still have..... seems they would really dampen the acoustic pressure wave scavenging effect of a header.

MrFC3S

thanks for the ideas, so what ive gathered is that i should use the stock mani and strait pipe(or gut the pre-cats and such) and try and get an SAFC, and eventualy get a street port...
also i heard from a friend that if i use the S5 Intake Plenum and TB, ide get like 20Hp just from that... True?or not?

Im replacing the shortblock with one thats not blown and taking the blown one and converting it into a TII, but wanted to stir up somthing mean beforehand... You know, scare people im my town with an NA 7, then Turbo it and keeping it close to stock. So plugs wires and Tune up stuff would help, and a true cold air intake too. Im wanting to custom make everything(accept the AFC ofcourse) I though also about using TII Injectors and Fuel Pump, but didnt know if that would help...(more fuel for bigger power...) Or if I could find it, Individual TBs for each intake port...
What power can be seen from NA tuning? and what are some ways to increase my Tourqe. and also what are some parts I would be better off getting at a Junkyard? Thanks guys

scathcart

Just going by my observations.... I wasn't using a butt dyno test, I was datalogging RPM vs. time graphs, which gives an excellent indication of change in acceleration, which is what we're really concerned about.

Putting a header onto an otherwise stock S5 or S4 N/A showed almost zero improvements in acceleration, and putting a header onto a stock engined S5 with an intake cone and straight exhaust also showed no improvements.

Putting the same header onto a ported engine showed large improvements over the stock manifold.

I can't really speak for 12A's; I never deal with first gens. I have zero information.

I've also never seen a stock N/A or modifed FC go to 10:1... what was this car? S5 N/A's I found would go to 11.2:1 at the lowest, and it took pulling out 25%-27% of fuel in the upper rpm ranges to get the maximum acceleration. S4 N/As tend to run quite a bit leaner than the S5. I've found largely ported S4's need fuel to be added in the upper rpm ranges.
I am curious if your friend's extra power came more from the fuel tuning than the header.
Guess I need to do some more testing.

RandomHero

iTrader: (2)

It is certainly true that a header on an engine with other volumetric efficientcy mods (like engine porting, or even a cone filter) will make a wide range of power increase. Prolly not even noticeable if the engine is pretty stock, but the more mods you have, the better the increase will be (to a certain point of course). But why go half-*** if you plan to upgrade all the intake parts and leave the stock exhaust manifold?

Unless you go with some kind of crazy port, i cant see why the airflow meter wouldnt be able to keep up with a small increase in airflow on an n/a engine.

peejay

I don't datalog, I look at timeslips....

scathcart

Fair enough. Both are relevant comparisons of change in acceleration.

scathcart

I don't feel the major increase in noise and induced NVH associated with a header are worth the gains on a stock port 6-port engine. I'd rather lose out on the 1-2 hp with the stock manifold and still enjoy driving the car on long trips without having to wear earplugs.

If you plan on doing some major intake and porting work, then by all means, throw on a header, but I wouldn't personally want to throw a header onto an engine that I don't plan on opening up.

There's more to enjoying a car than just power.

MrFC3S

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csvimports

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