Need help Exhaust setup
 

Hello, im from Jakarta, i need your opinion on my exhaust setup, since we have very limited and scarce aftermarket parts, i decided to do custom exhaust instead.
The car is 2012 FT-86 automatic.

1. Custom Catless 4-1 Equal Length Headers 1.625" OD
2. Stock Overpipe
3. Custom 2.5"(ish) Catless Front Pipe with 15cm long resonator tube
4. HKS Legamax Premium Cat-back

I've done some looking and decided that the Cat-back give the least HP/torque gains, and i'm not really satisfied with my cat-back sound, so im thinking to do a custom one.

So, what kind of cat-back should i make ? Mufflers or straight ? diameters ?
and will it give pretty much same HP/Torque as the HKS ? is my current setup bad and bottlenecks ? Thank you in advance.

How are your local laws around emissions and noise? If I ever had to redo my exhaust I would stick to a few general rules.

1. UEL for best sound that utilizes the stock overpipe unless you are running forced induction (if you arent worried about emissions, I would run a catless UEL)
2. Keep the stock front pipe unless you are running forced induction
3. Catback is up to your personal tastes if you are catless in the header a louder catback may not be the best idea if you want to avoid drone. If you are catless get a muffler, if you have a catted header, just resonators in the catback will probably be fine.

well, to be honest the laws on emissions and noise dont apply here, as long as its still tolerable then its fine.

i dont think i will be running FI, and i already did a custom header, frontpipe, and muffler. "custom" here means copying the design of the stock parts, but with slightly increased diameters.

I actually have HKS legamax cat-back but combined with Catless header and frontpipe, it doesn't sound good to me, too raspy/dry even with resonator in frontpipe. I still use the HKS midpipe, but i replaced the muffler with a custom one.

what really concerns me is whether my current setup gives extra power, because i cant really tell the difference.

Cat-Back gives nearly 0 power gain.

Headers (Name brand) AND a tune will get you power.

Otherwise you are doing pretty much nothing but changing the sound.

So you made a header that copies the stock design and just increased diameter a bit? Did you get rid of the cat in the header? Really hard to gauge performance gains as a header can be finnicky. Contrary to what people say about back pressure and crap, having nice smooth tubes with good velocity will increase power, but you could design it in a way to lose power. When I installed a UEL header and off the shelf tune I knew there was an increase in power, you should too!

How expensive is shipping for exhaust parts? I think it would absolutely be worth one of the cheaper UEL headers and pay for shipping for peace of mind and performance.

It doesn't have to be "name brand" in order to get more power with a tune from it. There are plenty of "off brand" headers on this forum that have seen a power increase with a tune.

That is correct, im running catless full exhaust, all of them are customized except for the centerpipe, im using HKS legamax premium catback but with replaced muffler.

The main reason i prefer customized parts is that the price gap is way too far, and branded parts are very rare for this car, and also, shipping them from outside the country is barely an option due to crazy tax rate, shipping cost, and passing the customs. For example, a Tomei UEL header here costs around 2,000 USD, while a custom one only costs around 200 USD.

My local tuner said that these parts will give extra HP/Torque best after a tune, but before that, theres not enough gains to notice. Then how can i know that the parts really contribute power after a tune, better than the stock parts with a tune also ?

I meant that literally.
As in anything someone else makes and sells.
Including the knock off brands.

Wow, that is quite expensive I had no idea. Did you have the car on the dyno before and after? Could compare gains to something like the Tomei.

Can you post some pictures of Jakarta?

Don't judge your power increase by dyno, judge it by 0-100 and 1/4 mile times.

Dynos are for tuning, oh, and dyno numbers are for circlejerks

Im planning to install Dastek unichip + dyno sometime soon, but before that i want to be sure that the exhaust setup does gain at least some power. I was told that if i had dastek installed, changing any exhaust part means i have to re-tune it again, and tune + dyno isn't cheap here.

By the way, i did some amateur 0-100kmh run and the best time was 8.0 to 8.3 seconds with full exhaust system, with the stock one it was 8,5 seconds or something. I thought this car goes 0-100kmh in about 7.7 seconds ? whats wrong with mine ?

When a manufacturer quotes a 0-100 it done with a professional driver, in the best conditions possible.

Track surface, temperature, tyre pressure, hell, even tail winds have been used.

They will do multiple attempts to get the best number.

In the end the main thing is the driver.

For me, I use a nice section of local road, have about 5 attempts, and see where they sit.

Going to a prepared drag strip will give the best and most consistent results.

A power increase is best judged, objectively with a dyno as it has the least number of variables. I never suggested that he uses dyno numbers for bragging rights, but rather to know exactly how much and where he gained power. May want to re-think before you post, why else would all of the top tuners have a dyno?

"Top tuners" use a dyno because they need on to tune efficiently, you cannot tune cars without one safely, yes people do road tune and log, and test and adjust, BUT, you can miss things which can lead to catastrophic engine failure very quickly, or, deal with the law for speeding.

As for dyno's, the same car on the same dyno with the same tune on the same day can and do give varying results.

From my experience from building and tuning multiple platforms I see it all the time.

+ or - variations are seen, the amount is dependent on power levels, but there is a variation on every run.

As for different chassis dynos on different days, my old Skyline would put down anywhere from 380kw to 415kw, same fuel, same tune, just different dyno and day.

That's a 35kw or 8% discrepancy.

Spit balling that: example - a 100kw engine running on different dyno's could read around 96kw or 104kw dependant, and thats if they are calibrated typically.

When I post a reply it is based on prior experience.

Yes, the area under the curve tells a story, but the numbers are only a estimate based of a algorithm.

What do you base your assumption that my statement is incorrect.