Introduction
This write-up is to help our car newbies in upgrading their car performance in a minimal way, and the correct way of course. No surbo, no micro compressor, no cyclone, no turbo jet, nor stromberg, heck not even stupid magnet gimmicks nor fake blow off valve! And the most important thing is, this guide will retain street drivability and very minimum noise increase (if possible).

Intake modification
The factory airbox has its own benefit such to avoid your filter from water splash as well as to reduce engine noise. Some people might think that the factory airbox is restrictive, but it is not always true since there are also aftermarket performance airbox as well. For example, the infamous Mugen air filter box (for Honda) which is actually smaller than OEM airbox. Another famous brand is ARC, which also makes intercooler, oil cooler and other performance stuffs.

1. Standard drop-in filter
If you hate engine noise, OEM filter replacement is what you would want. The standard drop in filter is actually not that bad. It is just that it has less surface area which restricts intake air suction. You can get those aftermarket performance drop-in filters such as K&N, Pipercross or HKS (just to name a few). However, I would like to remind that sponge type filter (such as HKS SPF) might have the best airflow but it's the worst in filtration. To choose a good aftermarket drop-in filter, you must make sure that it has more surface area compare to stock, else it is just no better. Performance drop-in usually does not give the best high-end power, but expect some good low end gains.

Pros : less noise, good low end power, low profile look
Cons : a little restrictive, sometimes no better than stock

2. Open-pod type filter
The airbox is removed and cone or dome/mushroom shaped filter is installed. Open-pod usually have more surface area compare to drop-ins because it has more surface area, thus more air can be sucked. However, this setup tends to suck hot air from the engine bay especially when the car is in parallel. Hot air is not good because it tend to have lower mass compare to cold air. Cold air has more mass, and more oxygen for combustion thus creates more efficient burning and more power. Somehow, this is not an issue when the car is moving especially at higher speed. Some people make heatshield to avoid hot air from the engine being sucked to the air filter area. Another good way to get cold air source is by having a cold air intake or air duct to supply air from outside of the car. Usually the air duct is placed behind the bumper. Another idea is to use custom long intake ram pipe and the air filter is positioned behind the bumper. The downside to this setup is that the airfilter can get dirty easily since our road is quite dusty and we have rain throughout the year.

There are many choices out there but most people would get K&N due to its reputation and availability. Another recommended one is the APEX'i Power Intake. This filter has one of the best filtration per performance compare to other competitors. HKS Super Power Flow is somehow not recommended for street usage due to our dusty road condition since it has poor filtration. For a user with tight budget, Simota would be a good choice if you want to try open-pod setup plus the aggressive sound of the engine.

Pros : better intake suction, more midrange to high end power
Cons : more noise, possibility of sucking hot air, can get dirty easily

3. Aftermarket intake ram pipe
Some of you might wonder whether to get aftermarket ram pipe or use the stock one. If you are getting aftermarket ones, make sure it is built with quality. If possible, avoid stainless steel ram pipes because they tend to absorb heat easily, thus increasing the intake air temperature. Iceman makes good ram pipe which is heat resistant. Size is also important. The smaller the diameter, the higher air velocity and the bigger the more air mass is allowed. Too small would be restrictive and too big is a waste. However, there is a type of ram pipe design which is fat in the middle. You can find this type of setup in some Honda. I am yet to find out the advantage, but the design is probably optimized for VTEC operation.

Pros : smoother air flow
Cons : possible heat issue

This post has been edited by antonio_zth: Feb 16 2006, 07:18 PM

Exhaust modification
Many people are just too careless in exhaust modification. They love the cheap loud exhaust, which gave them additional 20 psychological horsepower. For the extractor, everybody seemed to be suggesting 4-2-1 extractor, which could be just right for their street cars but the problem is they chose a custom made extractor made by some non-reputable company or by normal apek workshop. Those extractors are no more than factory standard, or might be worse. Making an extractor is not as simple as wielding steel pipes together, or bending the pipes as you wish, but the calculation of the length and the curve of each pipe which are the most important. That is why tuning house or performance part companies produce tuned extractors at expensive cost. Playing with extractor is no joke. Cheap ones are waste of money.

1. 4-2-1 type extractor
This setup gives power through out the rpm range. Drivability at lower rpm is quite good, making it the most suitable setup for street usage. Expect more top speed compare to 4-1 type.

Pro : Good power all across the rpm range, more top speed, good for cruising
Cons : Weak top end power, torque ends earlier

2. 4-1 type extractor
This setup gives more top end power. The low end power is weaker compare to 4-2-1 setup, but usually the power gain is significant from the midrange up to high rpm. This causes the torque range to come later, thus creating more horsepower at high range rpm compare to 4-2-1 setup. 4-1 is best for high revving motors like VTEC and MIVEC (just to name a few.

Pro : More midrange and top end power, higher hp, good for acceleration
Cons : Poor at lows, lower top speed compare to 4-2-1

3. I drive a Proton/Perodua.... which extractor should I get?
For Proton with 4G13/4G15, one of the best extractor by far in the local market is the PowerZone 4-2-1. It is made for better street performance and developed under proper R&D. HotBits also make extractors for 4G13/4G15 but a few reviews mentioned that it tends to get cracked after awhile. I would say, stay away from custom made extractors if you are looking for some performance gain, or else just get any brand/custom made if you just want to replace your old rusty ones. For those with 4G92/4G93, the OEM 4G92 MIVEC extractor should be good.

As for Perodua, there is not much choice for normal aspirated application. But if I am not mistaken, PowerZone do have tuned length extractor for Kancil.

Other than that, HotBits probably have extractors for various Proton/Perodua models.

4. Exhaust piping
Exhaust piping diameter is a crucial part in the exhaust system. For those with 1600cc engines and below, stick with anything less than 2.0" except if you had extensive jobs on the engine such as higher compression pistons or performance camshaft upgrades. For stock VTEC or MIVEC 1600cc and above, around 2.0" to 2.25" is acceptable. Some people even use 2.5" on stock VTEC (like myself) but the result is poor at lower rpm because the exhaust gas have less velocity to travel. Apart from the diameter, the piping route is also important. Straight pipes are not really advisable for street because they tend to get in the way when you're running on a road bump. It is annoying and you will get scratches on the bottom of the pipe, or worse bent pipes. Piping that follows the original route is the best. While it gives you stock appearance, many people claim that it gives better low end to midrange power compare to straight piping. While weak at low end, straight piping somehow tend to give better acceleration power because exhaust gas gets out easily because of the shorter pipe compare to stock.

5. Muffler
Muffler is more to cosmetic rather than performance. There is minimal difference in power output if we compare straight-thru type muffler (also known as N1 type) with s-flow type muffler (which usually have big resonator box). The later is seemed to be more preferable for street usage because more silent, thus giving more pleasant driving experience especially while in cruising mode. Personally, I would recommend Tanabe s-flow like the G-Medallion series because they are very silent when idling and cruising. This avoids attention from the authority. If you are going for N1 type, make sure it is made of good quality. Avoid imitations, they are widely sold by Wei Yip (tidak tipu customer) at surprisingly cheap price. Good exhaust doesn't come cheap but they are worth it. Try to spend some time to go to 'kedai potong' and try look for used branded exhaust. They are worth it. Other than that, exhaust with JASMA tag (not JASMA brand) should be good enough for street. From my experience and observations, JASMA approved exhaust tend to be quiet, unless the used mufflers are already running out of fiber. If your setup is still noisy, it is advisable to install a resonator (bullet silencer) in the middle.

The newer Proton Saga/Iswara has very good example on bad muffler setup. The exhaust tends to get noisy and noisy after awhile because of low quality fiber inside the muffler. Besides, normal cars should not have noisy exhaust, it is lame. They are even louder than my Tanabe even when my car is in VTEC mode!

6. Catalytic converter...to remove or not?
It depends. Cat converters are the biggest restriction to the exhaust gas flow. Removing it will definitely release some more power, but it is bad for environment. If your engine is badly tuned or always running rich, I suggest that just leave them on. Cat converters do not contribute anything to exhaust noise.

7. What is bullet silencer?
Some people also refer this as 'cherry bomb'. It is a small cylinder shaped resonator which usually placed in the middle of the exhaust piping. It functions as a muffler, to reduce exhaust noise. Due to its size, it is not as good as the rear muffler but still helpful because usually there is no space below the car that allows one to put a big muffler. To choose a correct size, the inner diameter should be more or less equal to the overal piping diameter to avoid restriction or bottleneck.

8. Flexible pipe
Usually installed after the extractor. The purpose is to minimize exhaust piping vibration and avoid the piping joint from being cracked. This is because the engine tends to vibrate and flexes backwards when rammed, so a flexible pipe will make sure that exhaust piping is not bent.

Somehow, rear wheel drive engines are exceptional because of the longitudinal engine layout that flexes to the left or right instead of front and rear.


Important notes!
* Top end power = power at higher rpm level
* Top speed = possible highest speed achieved

Feel free to comment and discuss. I will update this write-up once in a while.
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Useful links :

Advanced Header Design Tech Information by Team-Integra.net
Exhaust Theory and Design by Burns Stainless LLC

This post has been edited by soulfly: Apr 28 2006, 06:37 PM

forced induction should be quite easy and not much hassle compare to NA...

but i'll try to gather some information regarding banana type and normal type turbo manifold

That should be another level of mod.

Oversized throttle body : Might be a good idea for turbo. For NA, it's only benefit if you have extensive mods on your engine, like performance cams, high compression pistons or re-stroked engine

Extra injectors : If you're running stock turbo, you injector still can supply enough fuel eventhough you run higher boost than stock because no matter how high you set the max boost, stock turbo has its limitation. Install extra injector if you're not confident or just to be safe. For bigger turbo and higher boost, very advisable to get bigger cc injectors instead of just extra injectors.

ITB : good idea for NA tuning, but not advisable for noobs if they don't know what they're doing.

did i mentioned anything about max speed for 4-1? no i did not.

This post has been edited by soulfly: Feb 15 2006, 06:38 PM

I leave it as a discussion.

So cheap.... high probability that those are custom made ones.

Performance wise? Argueable... since the right extractor design must be properly tuned. Different primary/secondary pipe length leads to different kind of powerband.

Proper tuning is made under proper R&D and benchflow testing is one of it.

fish scale is neat, but sometimes it may leak as well

piping weld shows how skillful the shop worker is

This post has been edited by soulfly: Feb 16 2006, 12:50 PM

Zenden is most likely fall into 'accessories' category... same like Marco, F-1 Racing, Datco, Rimus (imitation of Remus) and various other generic brands that makes exhaust. I believe they stand for OEM replacement category instead of true performance.

PowerZone's 4-2-1 extractor was RM400 the last time I ask for pricequote. You'll get two for RM800

For me, a step by step would be extractor -> air filter -> muffler -> camshaft -> piping.

The only problem for camshaft upgrades nowadays, none of the manufacturers seemed to bother making cams optimized for automatics.

I put piping for the last is because oversizing the exhaust piping does not do much. You could even feel power loss at lower rpm. Besides, you're on automatic. For automatic, the best performance mod is to gain as much power as possible from the lower till the midrange rpm.

For the muffler, maybe you could try look for 2nd hand Tanabe s-flow.... they're usually priced below RM400. For value setup, maybe you can get an 'F-1' brand muffler. It's kinda 'cap ayam' but my cousin had one of those last time... s-flow type with big 'stomach'. The sound is not noisy. And probably, you can remove the catalytic converter and replace it with bullet silencer to reduce more noise.

camshaft makes most power compare to everything else

I've never been to JFA, but I bet they don't have benchflow test.

However, turbo manifolds should not worry too much, as long as they're of matched length and good quality.

It's just for the NA that matters.

my engine is louder than my muffler at WOT w/VTEC

You know EON at Saberkas commercial centre there? They got PowerZone stuffs. My friend is working there.

Most accessories shop will have it. But I prefer Tiong Hee, because they have plenty of stuffs, many choices.

If you're looking for original K&N, I think Siong Fah has it.

Some drop in will actually cost powerloss.

There was a test done on an Acura RSX with K20A2 engine with drop in K&N filter, the result was lower by 1hp for max power compare to stock

muffler gives very very minimal difference... sometimes almost none, or worse.

most of the time muffler is just for noise reduction and for appearance.

For the center piping.....

There is always the minimum, and the maximum specification before you get power loss for the whole system. I cannot confirm you what's the max and min size, because it also depends on the engine characteristic and the input at each cycle.

An example....

Let say the piping is 50mm at stock, giving you a lot of torque from 4000-6000rpm.

Then you increase the size to let say 55mm. The possibility is that you may gain torque only later, at around 5000-7000rpm. You see... your max torque has been shifted to higher rpm. To make it simple.... just say that the power comes late. The advantage of a late torque is you may have more maximum hp, but of course at much higher rpm.

However, there might be another situation where increasing the size would surpass the maximum spec... let say 65mm... where your engine had some power loss and your torque is lower all across the rpm range. This is possibility too.

One of the things that really gave significant extra power was the removal of catalytic converter. It's the biggest restriction in the exhaust system.

the previous one was 4-1? what car was it?