Originally Posted by
enVmyIX
**I am by no means claiming that this is my write up, it comes from chaotichoax over at evom. **
I have found this writeup to be very very imformative and would like to share it over here at SoCalEvo, maybe we could even sticky this?
"So you decided you want to modify your Evo?
This thread is dedicated to helping you learn the basics and choose the parts that are right for you.
I am by no means an expert when it comes to these cars. This is all my opinion. I have had a few setups on my car and I have read numerous threads as well as reviewing time slips and dyno sheets on others' cars.
This is merely a guide to help anyone that doesn't know anything in regards to what works and what doesn't.
**I made this to help eliminate the "what mods should I do to my evo?" threads.**
**If you guys have anything you'd like to add just PM me (I'll give you the credit.)**
Basic Bolt on Mods:
Turbo-back Exhaust (TBE):
This is one of the most common and most rewarding starting points when it comes to modding. Turbo back means you are changing your dowpipe/cat/midpipe/catback. Adding a full exhaust will open up the airways so your turbo breathes more easily.
Evom has plenty of vendors that offer multiple exhaust combos so you have the ability to pick and choose what you are looking for.
- Evos with ACD require a different downpipe than Evos without ACD (fitment issues)
- As far replacing the catalytic converter is concerned (For off-road use only of course): You can use a straight through test pipe/high flow cat/resonated test pipe.
- 3" is the standard among aftermarket exhaust replacements.
- All exhaust will yield different gains based on design and pipe diameter.
- A re-tune is required to make higher gains out of an exhaust.
Boost Controller (MBC/EBC):
You have two main options when it comes to boost controllers. First, a manual boost controller. Second, an electronic boost controller. The purpose of this mod is to allow you to control your boost and yield higher gains. DO NOT ADJUST TO HIGHER THAN STOCK BOOST WITHOUT A TUNE!!!
Manual boost controller (MBC): They have a simple design and require no wiring what-so-ever. All that is involved in them is rerouting vacuum lines. They will decrease boost taper and give you full adjust ability over the boost of your turbo. You will need a boost gauge or data-logging equipment to check your boost.
Electronic boost controller (EBC): They are obviously electronic and require a little more setup time. They allow you to dial in your boost more accurately and some allow more than one preset setting (ex: high and low boost). They also compensate for changes in weather (density of the air) and are less likely to experience boost creep in the cold.
- MBC are much cheaper and have only one working part.
- EBC can cost as much as four times what an MBC costs but provide better adjust ability and more precise control. They adapt to weather and allow for multiple settings.
- GET THE CAR TUNED BEFORE YOU TRY AND TURN THE BOOST UP!!!
Boost Gauge:
The purpose of a boost gauge is obvious; monitor your boost level. You can get manual boost gauges or electronic ones; same concept as MBC's/EBC's. Cost and accuracy are factors here. This is a very necessary mod and not having it is similar to playing with knives blindfolded.
- Helps with tuning.
- Available with and without vacuum readings
Wideband - Air/Fuel Ratio Gauge
The purpose of an AFR gauge is to monitor the ratio of air/fuel to 1. This allows self tuners and pro tuners to tune a car to it's maximum level. They are primarily digital and require being welded into the downpipe of the vehicle.
- Aside from a boost gauge this is the most important gauge to have
- Most commonly used is an AEM UEGO AFR gauge
- Vital to tuning
- The higher the number the leaner the air/fuel mixture is
- The lower the number the more rich the mixture is
- 12:1 is pretty much as high as you want to see at WOT
- 14/15:1 is average for spooling
- 14/15: is also average for idle
- If the car runs rich it will foul spark plugs quickly
- If the car is lean it will pull timing and possibly knock
Fuel Pump:
Upgrading your fuel pump is a cheap mod and can save you an engine in the long run. They are inexpensive and allow you to up the boost since the amount of fuel can be upped with the boost.
- VIII's had a less capable fuel pumps than IX's do.
- VIII - 300whp or more the pump should be changed out (just my opinion)
- IX - 350whp or more the pump should be changed out (just my opinion)
- 99 out of 100 people use a Walbro 255lph fuel pump; it is a drop in replacement.
- A tune is needed to make full use of an upgraded fuel pump.
Intake:
Many will tell you that a stock intake box with a drop in element is your best bet. This solution is good up until about 400whp. There is nothing wrong with that solution but an open filter intake will yield gains. Some open filters use the stock intake pipe some require their own. When upgrading the intake a tune is very important. Especially if you eliminate the stock rubber intake pipe and substitute it for a metal one. The intake pipe wreaks havoc on your MAF readings and cause a jumpy idle. They can even cause the car to stall in certain situations.
- Some open filters are dry and some require oiling.
- If you replace the factory intake pipe, be prepared to deal with an erratic idle.
- A tune is needed to see gains and improve drive ability.
Diverter Valve/ Blow Off Valve (DV/BOV):
Do yourself a favor; kill the ricer within you now. Evos do not respond well to BOVs. Especially if they vent 100% atmospherically. The stock IX diverter valve (aka JDM MR diverter valve) is a very capable and inexpensive solution. The IX diverter is metal and can handle 25 psi without any issue. You will experience very limited, if any drive ability issues. Partial throttle situations will be manageable and not violent.
- If you have an VIII, do yourself a favor and get a IX diverter valve.
- Don't be a ricer, unless you have an aftermarket ecu then stick with a recirculated diverter.
- Aftermarket diverters tend to have partial throttle issues and will never be as daily driving friendly as the stock IX diverter.
Intercooler (FMIC):
The stock FMIC is very well matched to the stock turbo and really doesn't need to be upgraded. However, a 3" FMIC will decrease the chances of heat soak and provide some minimal gains.
- Not much to say here.
Intercooler Piping (UICP/LICP):
The upper intercooler piping (UICP) isn't going to do much in terms of gains but it will limit you to a stock flanged DV/BOV. The lower intercooler pipe is a great mod. It will improve spool up. Reason being, the stock LICP tapers towards the turbo and has unnecessary bends.
- UICP: Not really a necessary mod unless you need a different flange or you are using a mini battery and have the room to use a shorter route UCIP.
- LICP: Definitely a great mod, you'll see HP/TQ gains as well as quicker spool up.
- It's not a bad idea to upgrade the stock pipe couplings. They tend to expand under boost.
O2 Housing:
An O2 housing is what the downpipe on the exhaust bolts to. The idea is the same as the TBE; open up the exhaust to increase hp/tq ratings as well as improve spool up time. This mod requires a bit of time and disassembly.
- You can get them ported and coated to retain heat.
- Can cause boost creep because of how much they open up the exhaust.
Under Hood Shifter Bushing:
Sure, they won't make your car faster but they will make it more enjoyable. The shifter feel in an Evo leaves something to be desired. These bad boys are the solution. They'll eliminate the sloppy feel of the shifter and help make your shifts feel much more precise.
- They will also help eliminate high RPM lock out some aftermarket clutches can cause.
- Cheap mod and well worth it.
Tune:
The most common method of tuning these cars now a days is a simple reflash. Evos have a few programs available for download that have tons of logging parameters and can be used to log and tune these cars. Any evo tuner can do this for you or you can do everything yourself with a laptop/Tactix cable/programs. You can get the car street tuned or dyno tuned. Either way, a tune is the true way to unlock the potential of an Evo. It gets you the most out of your mods and allows proper adjustment for fuel/boost/etc. Bottom line, GET A TUNE!!!
- I only mentioned a reflash because it is the most sensible option for someone new to modding
- Search the forums for tuners in your area or those that offer mail in flashes.
- Increases power as well as gas mileage.
- A TUNE IS THE MOST WORTH WHILE MOD FOR THIS CAR - WHETHER YOU INTEND TO MOD IT OR NOT!!!
Methanol Injection:
Basically this is an alcohol container with a pump attached to it not so unlike your windshield fluid tank. These devices are usually preset to come on during some kind of trigger say... boost, throttle position, or maybe even a combination. What they do is flow methanol or some other alcohol into the intake stream via a nozzle. You can buy nozzles of different sizes to increase the amount of fuel flowing in. What this does is not only add additional fuel to the engine so your injectors will work less but increases the octane rating because methanol and ethanol both have much higher octane ratings than standard pump fuel. An additional side effect is the intake charge temperature is lowered due to the evaporation of the alcohol, just like when you get some rubbing alcohol on your hands and it feels cold same effect.
If you plan on getting one of these kits make sure you get a tune. A stock Evo already runs very very rich and by adding more fuel your only going to make it worse.
Water Injection:
Water injection is by all means absolutely the same idea as methanol injection but water does not provide additional fuel nor does it provide additional octane. The reason people do this is the combustion chamber contains a lot of residual heat left behind by the burn. The water enters the chamber and rapidly cools down the air in the chamber allowing you to run more boost and more timing but the downfall is the octane is still limited so it will not be as effective at controlling detonation.
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Beyond bolt on mods:
All Courtesy of RoadSpike
Built Block:
This means that the lower end (rods, pistons, and sometimes the crank) have been replaced with high strength forged parts capable of taking additional abuse. These stronger parts will allow the motor to rev higher as well as take the increased power output of high output turbos like the gt42r even when pushing to or above 1000whp.
Stroker Kit:
The stroker kit increases the displacement of your motor by increasing the stroke or rotating size of the crank. These kits include a complete rotating assembly (pistons, rods, crank). Stroker kits increase the torque output of the motor due to its increased size but limit the safe rev limit of the motor when compared to built motors with the stock crank.
Head Work:
The most basic mod to your stock Evo head would be to put upgraded springs and retainers into it. This increases the safe rev limit of the head preventing valve float, where the valves don't properly seat in high rpm operation due to low spring pressure. This of course is assuming your bottom end will take the abuse the stock bottom end isn't known to be very reliable beyond 8k rpm. Additionally to springs you can opt to have your head port and polished. This means that the heads will be gasket port matched so the opening to the head is the exact size of the gasket creating a smooth transition and increasing overall flow. The last thing done to heads is the use of oversize valves. Over sized valves allow for large valve openings which again increase over all flow of the head.
Cams:
Generally thought of as one of the best bang for the buck mods cams increase the power of the motor by allowing the motor to breathe more efficiently at some rpm range. Cams are measured by lift, how high the valve is opened, and by the duration which means the amount of time the valve stays open. There is also another measurement called ramp rate which is the speed in which the valve opens or closes. Stock valve trains can only safely lift the valves 10.5m to 10.8mm at mild ramp rates as seen in the hks and gsc s1 cams. Aggressive cams like the JUN 272's require the use of aftermarket springs to account for the high ramp rates and lifts the cams produce.
Besides the obvious number on the cam 264 and so on you need to consider the valve lift the cams produce. It should seem pretty obvious that if you lift up the valves more then more air will rush into the chamber. Now combine that with how fast they open and how long they say open for and you'll get an idea why some cams like the JUN 272 are VERY AGGRESSIVE and why the HKS 272's are not.
Defining Aggressive:
Lets use the GSC "S" series cams as the example here for how duration and lift effects the power. With the S1 cams you have a 268/266 cam combo with just 10.5 mm lift this cam would be effective from 3000-8000rpms. The S2 cams have even larger lifts (11.2/11.1) and durations (274/272) making them quite aggressive pushing the power band to the right 4000-9000rpms. S3 cams have what i consider insane lift (11.5mm) and large durations (290 or 280) making their application strictly geared towards all out power, don't expect these to idle with no effort.
As you make the cam more and more aggressive what happens is at very low engine speed ,IE idle, you start to loose running vacuum. This is because of valve overlap which means simply the duration of time when the exhaust valve is still open and the intake is opening. Some where in the 20's or 30's some genius figured out if you open the valves when the exhaust is being pulled out it improves performance however if you do this too much then your idle suffers since the charge of air will be diminished if you leave the exhaust valve open for too long air escapes out into the exhaust. However on the flip side at higher rpm overlap helps improve the air charge into the combustion chamber making more power.
Now you may believe that HKS 272's are aggressive based on the S2 specs but really they aren't because the lifts they produce are much less than a S2 cam. The lift of HKS is 10.8mm intake and 10.2mm exhaust, this shows it has higher lift than a s1 on the intake making the intake more aggressive and lower lift on the exhaust making it less aggressive there. This kind of combination would make less midrange power but come into range at slightly higher rpm ranges than the S1 cams. Now as a curve ball the JUN 272's are very aggressive with lifts around or maybe even higher then the S2 cams making their power band along the lines of the s2 cams. If your purchasing cams from a shop and your confused as to how aggressive they are I suggest just calling them and asking them questions.
Cam Selection:
If you plan on sticking with a turbo from stock up to gt30r series then the kind of cam selection that would benefit you the most would be a moderate to very light cam in terms of aggressiveness. There are many cams out there anything along the lines of hks 272/264, S1, or some other lower lift 272's out there would be fine.
If you plan on stepping up the turbo to a gt35r and beyond then larger cams will certainly add power in those turbo's effective ranges 4k+ rpms. If you plan on trying to beat the current HP records then maybe the S3 cams are right for you
The only other notes i can give is that the larger the duration of the cam then the larger the overlap will be and thus your idle will need more adjusting. If your going for aggressive cams your going to need to get a tuner to help you dial them in.
Cam Gears:
The idea behind cam gears is very simple, basically what your doing with cam gears is changing either the center location of the cams, the overlap, or both. So with the gears you can fine tune your cams shifting the power band from left to right but usually at the cost of performance somewhere else.