Ok, With the increase in questions reaguarding the 1.8L recently, I felt it was in the forum's best interest to have a 1.8L FAQ (We have one for ever other engine, why not this one?) I am going to try to go as detailed in this as possible.

I am going to start this off with what seems to be the most popular question regaurding the 4G37 (1.8L) engine.


To be blunt, there is really only one option to make this engine fast. Turbo. Now mind you, this option is NOT for the faint of heart. It requires A LOT of custom work, researching, time, and most of all, cursing. I will go into more detail with this in another section but for now, let me give you some links to basic bolt-ons that will help a little (And I stress the term "little".)

A.) Cat-back Exhaust System - The building block for all performance on any car. The very first performance mod you should do. We have all heard of this in one way or another. Weather it's driving down the street only to hear the cry of a "pissed off bumblebee", or learning about it in your college's Fluid Dynamics course. Whatever the reason, you NEED this no matter what your goals are. However, with this said, the type of exhaust you choose is rather strait-forward. The first thing you are going to need is a performance muffler. There is a WIDE variety of these out here, but how do you know which ones actually work? Well, to answer your question, There aren't many. The ones that are pretty popular in the DSM scene tend to be as follows: Magnaflow, Megan Racing, Apexi N1, HKS Ti, Tsudo and off the top of my head that about covers it. I am sure there are more, but the best advice I can give you is simply try to stay away from knock-offs, whether it be from Ebay or elsewhere. The next exhaust piece you are going to want is a high-flow cat (Catalytic Converter.) Again, there are many, many brands of these but the two that people tend to trust most are Magnaflow, and Megan Racing. Both are relatively cheap. The last piece of the cat-back system is the piping. This piece (or pieces if you will) is a VERY touchy subject. There is a lot of debate as to whether the back pressure of a naturally aspirated motor needs back-pressure or not. Some will tell you that it does need it for various reason, while some will say get as big of pipe as you can. I, personally, don't know what to believe on this subject, but I will say one thing: there is no reason why you would need bigger than 2.5" pipe on a N/A vehicle. With this said, if you are turbocharged, or are planning to in the future, then I would get 3" pipe. It will allow the engine to breath better while raising your volumetric efficiency even farther past 100%.

(IMG:style_emoticons/default/cool.gif) Exhaust Manifold (Header) - Ok, before I go into this I want to make something clear. It is NOT headers!! a 4 cylinder car only has ONE manifold, thus it is called a HEADER!! I get VERY upset when people say this wrong. Why? I have no idea. At any rate, it is far more politically correct to say Exhaust manifold or simply, manifold anyway, so please do us all a favor and try to expand your vocabulary pallet and use this term instead. Now that my rant is finished, on to the point at hand. After much searching and research I have come to a rather unfortunate conclusion. These are rare, very, VERY rare. Your best bet as to getting a manifold that actually does something besides make your engine bay look like 50Cent's teeth, is to have one custom made. The best design for our motors is, hands-down, a tubular design. RP Fabrications (http://www.rpfabrications.com/) makes a very nice affordable manifold. Check them out. Your only other option is to just find an exhaust shop that can mandrel bend pipe and have them make you a tubular manifold using 1.5" pipe for runners. Don't ask me for a price, since it will be different with each shop.

C) Intake OK. First a little lesson in the types of intakes. There are two major types, short ram intakes (SRI) and cold air intakes (CAI). Theoretically the latter of the two SHOULD make more power due to the fact that colder air yields to better combustion, however the reality of this subject is not too compliant with theory. In small engines it doesn't make enough of a difference to matter. THE BEST intake I have found for the 4G37 is made by a company called Cosmo Racing. It only costs 99.75 USD + shipping and fits nicely.
http://cosmoracing.com/productinfo.asp?cid=131&pid=394

D) Spark Plugs - NGK. 'Nuff said. Go to your local parts store and pick up a set. Not too expensive. Also, the only ones that are available pre-gapped are the BRP6ES-11's, however, if you wish to go colder there are some BRP7ES-11's from other motors that will fit, but they will require you to gap them yourself, however, that is rather easy. Just keep in mind that you shouldn't really go colder unless you are running boost.

E) Spark plug wires - Honestly, there really aren't any "performance" plug wires out there. The best advice Ic an give you is to head over to http://www.sparkplugs.com/ and grab a set of NGK wires. They are pretty much OEM replacement, but NGK have been proven over and over on many different motors and are hands down the best brand out there. Besides,, they come with a nice warranty to boot. (IMG:style_emoticons/default/biggrin.gif)

That about covers bolt-ons. I know it isn't much, but do you see now why your only real choice is to boost?

The next part off this section is internal mods. These are probably the hardest mods to do if you do them yourself, however, they are crucial for a turbo build, and will give you some decent gains in a N/A build.

A) Bore - The factory bore of the 4G37 is 80.57mm (80.6mm), if you bore this out a bit, you can force some extra ponies out of your block. the MAX I would bore it out is .060 over but even that is pushing it. Any more than that and you will be seeing coolant jackets. If you plan to turbo it and shoot for higher HP numbers, I would just take off as little as you can to perfect the cylinder walls. This way you have less of a chance of cracking the block.

(IMG:style_emoticons/default/cool.gif) Forged Pistons - There really are no forged pistons for the 1.8L. However, there are a couple options. Ross and Weisco are both reputable names in the DSM world and both of them are so gracious as to offer a custom piston option. If you give them the specs you want they will fab them up and send them to your door for the small fee of 495 USD. Go ahead, send them a thank you e-mail. You know you want to. Before you go ordering though, I should probably inform you on what you are looking for. If you are going N/A you want some higher compression pistons. If I was truly building a Solid N/A motor and had absolutely NO plans to EVER go turbo, I would probably go with 10:1 or 11:1 pistons. This will allow for hbetter volumetric efficiency and net some decent hp and torque gains. Also note that if you decided to bore your cylinders then you will need to take that into account when ordering. If you plan on going turbo, best bet is anywhere form 8:1 to 9:1. The higher the compression ration, the more power will be output, however, the higher comp ratio, the harder it is to tune and the more stress is put on your internals. There is also another option. IPP (Import Performance Parts) offers a "performance rebuild kit". It includes wiseco piston made to order along with various other nice little pieces.
Here is the link: http://www.importperformanceparts.net/impo...mitsubishi.html

C) Stroke - No, this is not what your grandfather suffers after being scared, this is the distance the piston travels in the cylinder. The factory stroke of the 4G37 is 86mm. Aside from a custom made crankshaft (Since there are none available for the 4G37) there is really no way of changing this.

D) Connecting Rods - The 4G37 rods are actually pretty strong. from the factory, the rods are said to support 300whp, however, if you still want to upgrade, the only real options is to either have them custom made (Pauter does some very nice custom rods, but they are rather expensive [~850 USD]) or have your factory rods cryo-treated (This is MUCH cheaper). Unless you are goin' all out and not leaving a single component untouched, there is no reason that the factory rods won't suffice, however, even if you decide upon the latter option, I would still recommend getting some new Eagle OEM spec rods. You never know how much life is actually left on your stock rods.

E) Camshaft - http://www.importperformanceparts.net/impo...mitsu-cams.html Schneider is the ONLY company that makes camshafts for the 4G37, and event these are simply regrinds. Since, ideally, when it comes to cams you want some that will work all the way to the red line plus a little over the red line, the best option they have is the 3000-7000rpm option. However, this really depends on your personal preference.

F) Valves/Valve Springs/Retainers - Whenever you go with a different grind cam, it is standard practice to upgrade your valve springs as well. To my knowledge there are no aftermarket valvetrain components other than camshafts that are supplied for the 4g37, so your only option here is to go custom... again. There are four different materials used in these components:
I) Titanium - This is the best, hands down, however, it is also the most expensive. These are VERY lightweight, thus allowing you to safely rev much higher than you would be able to with other materials.
II) Stainless Steel (SS) - SS is VERY durable, and least prone to breaking, however, because they are SS, they are rather heavy compared to other materials, thus limiting your rev capabilities.
III) Steel - This is what most factory components are made from. it is not as lightweight as titanium, but at the same time it is not as heavy as SS, however, it is also the least durable of all materials.
IV) Chromeolly(sp?) - These are second to Titanium when it comes to performance. They are lighter than the SS, while not as light as titanium, but they are stronger than titanium, while not as strong as SS. These are your all around springs.
When it comes to valves, a lot of people like to run oversized valves. I do not recommend this, as the 4G motors have very low valve clearance to begin with and milling the head enough to run even 1mm oversized valves creates the possibility for piston tap.

G) Port/Polished Head - Since, from the factory, the VE of the 4G37 is only 78% (compared to the 4G63's ~89%), your main focus should be getting this as close to 100% as possible. Something that REALLY helps is porting and polishing the head. the factory size of the intake/exhaust passages of the 4G37's head is 1.25". Most enthusiasts choose to port them out to 1.5" for increased airflow.
Keep in mind that if you go turbo, your VE will be over 100%. Port and polishing the head just further escalates that value.

H) Knife-Edged Crankshaft - Since odds are your motor has many miles on it, when rebuilding the motor, you should MAKE SURE to have your crankshaft knife-edged. this will smooth out all of the nicks and scratches on it and make it flawless again, which will help performance a bit and keep your motor running nicely. More of a maintenance mod than a performance mod.

I) Head Studs - A common practice on ANY built motor is to replace the factory head bolts with aftermarket head studs. Most of you are probably asking, "WTF is the difference?", well the difference is this, when you torque down head bolts they expand, thus rendering them useless if you ever remove the head again, meaning you will have to buy new ones. Head studs are stronger and do not expand upon torquing, meaning they will last you forever. The best brand out there is ARP. However, no brands make them for the 4G37, let alone one as prestigious as ARP. There is, however, an alternative. If you drill/tap the holes on the head/block to accommodate for the size of the ARP head studs for the 4G63, you can use them. Just make sure you only drill 3/4" down as the studs are shorter for the 4G63 than the 4G37.


-All rights to this guide belong exclusively to Jon Bonazza. All unauthorized use or reproduction is punishable by law.

This is a very very complicated procedure to do. I will Try to keep this as noob-proof as possible, but I can only do so much.

Things you will need for the build:

A) Turbo - Ok, if you really didn't know you needed this then you probably should be driving a short bus rather than a DSM. The choice of turbo will pretty much govern the rest of your setup. You don't want something too small or it will be basically pointless, but at the same time you don't want something too large or you will drown your motor in turbo lag. Remember, you have a much smaller motor than the 2.0L 4G63. The two major turbo manufacturers that develop good turbos for the 1.8L are MHI (Mitsubishi Heavy Industries) and Garrett. MHI turbos are nice, and alot more economically friendly, however, they tend to be pain in the ass to pipe. The Garretts have a rotatable housing which help to ease piping pains. Popular choices for the 1.8L include the 9B, 14B, T-25, 15G, 45-Trim, and the 50-trim. The 9b comes factory on the the Mitsubishi 3000GT/ Dodge Stealth R/T TT. The 14b comes factory on the eclipses/talons/lasers with manual transmissions from 1990-1994. The T-25 came on turbo eclipses/talons/lasers from 1995-1999. The 15G came on the 1984-1987 Mitsubishi Mirage/Dodge Colts equipped with the 4G32BT motor. Lastly, 45-trim and 50-trim are Garrett turbos. Before choosing a turbo, you should decide what you want out of the car.

(IMG:style_emoticons/default/cool.gif) Turbo Exhaust Manifold - One of the many pieces that will need to be custom fabricated. RP Fabrications (http://www.rpfabrications.com/) makes some really nice manifolds for the 4G37. They have three different styles available: Ram-Horn, Equal Length, and Log. The Equal Length is the best, but also the most expensive. The next step down would be the Ram-Horn. This looks the coolest, though. The log is an economic friendly manifold. Its far inferior to the two aforementioned styles, but is about half the price. Another option here is a bit cheaper, but a bit hard to locate. from 1984-1987, The dodge colts and Mitsubishi Mirages had a turbo trim that had a 4G32B (A.K.A G32B) motor in it. It was the same platform, except it was 1.6L rather than 1.8L and the exhaust ports on the head were smaller. If you can locate a turbo manifold from one of these, you can just have it ported and have an adapter flange made for the turbo you want to use (Unless you use a 15G or 9B. They will bolt right up.) Now you may be saying to yourself, "Well hell, I will just go to the dealership they will have it!" Sorry, buddy. You fail. This item was discontinued years ago. The only two places you will find this is a junkyard or online somewhere. Good luck. I am going with a custom manifold, since it will flow much better than the G32B manifold.

C) Wastegate - This item is tricky. If you are using a MHI turbo, they are internally gated, so you won't need to buy one of these. MOST Garrett turbos use an external wastegate setup though, so if you have one of these, keep reading. A popular choice for any turbo app is a Tial 38mm wastegate. You will also need to have a wastegate flange welded onto your manifold. This means that if you somehow managed to find a G32B manifold and went with it, then you will be forced to use an internally wastegated turbo (I.E. MHI turbo). Some people on the 4G63 apt to use the Tial 44mm Wastegate instead of the 38mm. The choice is really yours.

D) External Wastegate Dump - If you use an external wastegate, you can still get the dump, it just requires a diffferent piece. I would highly reccommend, however, that you recirculate the wastegate into the downpipe. This will keep those hot exhaust gases out of your engine bay. If you do decide to dump, be ready to run REALLY hot!

D) O2 Housing - Again, you can dump or not dump. Again, I recommend recirculating. Dump just makes a really nice sound anyway and honestly, gets very annoying after a while.. In some rare cases some turbos may suffer from boost creep, in which case a dump housing will help with this, but generally it comes down to personal preference, really. If you are using an externally gated turbo, then you will not use one of these. The downpipe will connect strait to the turbo.

E) J-Pipe - If you go MHI, get one that matches the turbo you chose. If you go Garrett, this is not needed as the compressor housing can be rotated to adapte to your intercooler piping needs.

F) Intercooler - You can either choose a side mount intercooler (SMIC) or a front mount intercooler (FMIC). A FMIC is MUCH easier to pipe and mount than a SMIC. There is really only one place to mount a SMIC and that is on the passenger side towards the front of the engine bay. Even then it is a tight fit. CXRacing makes really nice intercoolers for a reasonable price.

G) Intercooler Piping - This will have to be custom. Make sure you find an exhaust shop that can mandrel bend piping since compression bends will restrict airflow and look like crap. You CAN opt to use aircraft grade hose for the lower piping, however, I would recommend steering away from this. 2.5" pipe should be sufficient for this. Another option is to buy a universal piping kit off of ebay (They usually run around $100) and make it work yourself.

H) Downpipe - Simple. Go to a mandrel bend capable exhaust shop and have them fab one up. Size should depend on the size of the rest of your exhaust. You want it to match. You will also need to order a flange to match the turbo you use A good website for flanges is http://weirtech.ca/catalog/product_info.ph...products_id=116

I) Blow-Off Valve (BOV) - There are two differnt ways you can do this: The first of which is to vent the BOV to the atmosphere. This method can ONLY be done if you have a stand-alone ECU (such as AEM or Megasquirt) that allows you to convert to a speed density setup or a MAF-T Pro piggy back. The second option is what you HAVE to do if you are running a MAF and not setup for speed density. This option is to recirculate the BOV into the intake pipe. Keep in mind, if you are running speed density, you don't even need an intake pipe. You can just clamp the filter to the turbo.

J) Adjustable Fuel Pressure Regulator (AFPR): Aeromotive and Fuel Labs makes good ones. they are pretty much universal. Just make sure its a 1:1 AFPR and you get the right fittings and lines to go with it. This is optional, but greatly helps with tuning.

L) Injectors - 390cc+. You can use the 450cc's from the factory 1g's if you wish. The size you use will depend on your goals and other mods.

M) Tuning Device or Stand-Alone ECU -There are a few options here, but the most common are the Apexi AFC or the Megasquirt stand-alone. The AFC is nice and much easier to use, however, it can only correct +/- 50% of the factory injector size. This means, the biggest injectors the AFC can tune at acurately are 450cc. That is still pushing it tho. The best thing you can use is the Megasquirt stand-alone. This is a DIY kit, so if you aren't good with electronics and soldering I DO NOT recommend this. However, if you aren't good with the two things mentioned, then there IS an alternative. DIYAutotune.com makes pre-assembled kits that ease the installation a bit, but you will still be required to modify the pre-assembled unit to fit the 4G37's ignition system. This is a full stand-alone, so it controls everything from spark to fuel to air to timing. Also, with the Megasquirt, the injector sizing and everything else is limitless. Also, as of recently, DIYAutotune constructed a ready-to-go kit for the 4G37. You can find it on their website.

N) Fuel Pump - Walbro 255 or 190, depending on your goals and setup. 99 USD + shipping. Cheap. The 255lph and 190 lph are the same price however, so why not just go with the 255?

O) Boost Controller - Trust me on this one. Get a manual boost controller (MBC) electronic boost controllers (EBC) are nice, but no where near worth the money you'll pay for one. Plus MBC's are so much simpler to use and hook up. Hallman makes a nice affordable MBC (~$75)

P) Stainless Steel Oil Feed line and Fittings - You will need to buy a rather large length of SS line, since the next 2 items will also require the use of it. I would go with about 10ft. This isn't normally available over the counter at parts stores, you normally have to travel to a performance shop or even order offline. Summit Racing (http://www.summitracing.com) has it for fairly cheap. For the oil feed, just tap it off of the place where the oil pressure sending unit screws into. just insert a T-fitting behind the pressure sender. Also, keep in mind that SS line is very hard to work with. Installing the fittings is a HUGE pita. I highly recommend having a shop do it or at least teach you the first time, as if you do not know what you are doing you cna cut yourself pretty bad.

Q) SS Oil Return Line and Fittings - This one is a bit more complicated. Best way to do this is to weld a 1/2 to 3/4 NPT bung into your oil pan, then screw a -10 AN fitting into the bung. On the turbo just use a -10 AN oil return line flange. Another option is to use a 1/2" NPT oil return flange for the turbo with a 1/2" NPT Hose barb fitting screwed into it and instead of screwing a -10AN fitting into the bung on the oil pan, screw in a hose barb and use transmission coolant hose. This will stand up to the heat and is a bit easier to work with.

R) SS Water/Coolant Lines - This is pretty self explanatory. Same concept as Oil feed. except you use banjo fittings for the turbo. If you are using a ball-bearing or journal-bearing turbo, you will not use this line.

S) Intake - Your best bet is to have a mandrel bending capable exhaust shop bend you some 3" pipe and weld in a bung for the BOV recirc and buy a filter housing from Cosmo Racing (http://www.cosmoracing.com) and connect them with a silicone coupler. This way you can easily connect your MAF.

T) AEM UEGO Wideband Kit - This is the best out there, hands-down. A wideband o2 sensor is mandatory for tuning your car. Another option is an Innovate wideband O2 sensor with your choice of wideband O2 gauge.

U) Boost Gauge - Try to get a mechanical one. They are much more accurate. Many brands out there. AEM, Autometer, Glowshift, Prosport, Defi. Pick one.

V) MAP Sensor - This is ONLY needed if you are running a stand-alone with a speed density setup. Here is a link to the MAP Sensor you need:
http://www.diyautotune.com/catalog/map-bar...14c0e7ddb2bf05f
You will also need this:
http://www.diyautotune.com/catalog/sensor-pigtail-p-163.html
and this:
http://www.diyautotune.com/catalog/open-el...gtail-p-62.html
You will have to do some wireing as well, so be ready for that if you decide to go this route.

Optional pieces:

A) Oil Cooler - This will help you keep oil temps down, and make your engine run a bit safer. If you choose to run an oil cooler, you will want to tap it from your turbo return line, NOT your supply (feed) line. best place to mount it is right behind the plastic shroud in the front of the radiator.

(IMG:style_emoticons/default/cool.gif) Data Logger - There are a few of these out there. The most popular seem to be a palm pilot with a data logging software.

-All rights to this guide belong exclusively to Jon Bonazza. All unauthorized use or reproduction is punishable by law.

This cuts down on my search for cheaper/ correct parts by far! thanks for going through the trouble!

version 3.0 of this article as been released. It offers more knowledge than the previous versions.