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Ok first off lemme just say, PLEASE do not flame me for this. This thread is soley an attempt to educate people on how to turbo a 1.8 or 420a. I realize that Kalani did a write-up on DSMTalk.com on this but he left out a good deal of stuff so I am going to attempt to elaborate on the topic.
The first thing you will need, is of course, a turbo. Now if you are working with the 1.8L 4g37 then you will want a relativly small and fast spooling turbo, alot of people tend to opt for a stock 14b or a T-28, although Garrett T3 turbos are probably the most Ideal if you can afford one. Your turbo choice will rely on many variables such as HP goal, Intercooler choice, etc.. but to ease your decision I will throw a couple pointers at you. first off, mitsubishi turbos are a PAIN in the **** to pipe to an intercooler, FMIC or SMIC dont matter... (im talking about on 420a and 4g37 motors. you need to work with whatever angle to compressor housing happens to open up with (btw you will be required to get a custom made manifold so that makes it a bit easier) Garrett turbos are more flexible, and you can rotate the compressor housing to suit your angle needs and ease piping pains. I will give a few other options a bit later.
Manifolds - This one is tricky. In a perfect world we could just bolt up a factory 4g63 manifold and call it a day. Unfortunately, it is not that simple. I am going to break this up into two (2) sections, one for the 1.8L 4g37 and a second for the 2.0L 420a.
- 1.8L 4g37 -
OK this is quite the pain in the **** sincce there really are not that many options to choose from yet none of the options are exactly easy either.
Your first option is to somehow locate a turbo manifold from a 1984-1987 dodge colt/mitsubishi mirage 1.6L turbo. These are INCREDIBLY hard to find but are a direct bolt on to the 4g37. the engine code for the colt/mirage is the 4g32b (AKA the G32B). if you cna find one of these you will need to have the openings ported to match those of the 4g37 motor since the 4g37 has slightly bigger ports than the 4g32b. Also, you will need to have an adapter flange fabricated to fit the turbo you selected. If you REALLY want to make things easier on yourself a 15g turbo is a direct bolt on to the 4g32b manifold which will save you the trouble and money of having an adapter made. TEC makes 15G Upgrades for the 3000GT, so try looking there. Another option (and the one I chose for my build) is to have a custom manifold fabricated by an exhaust or machine shop. It will be alot more expensive but will flow alot better, look prettier, and net a little better hp gains. Which path you take is ENTIRELY your choice.
- 2.0L 420a -
Ok this one is a bit easier. 420a turbo manifolds are all of there place, Ebay is probably the first place I would start. I am sure other people on this forum who have already turboed their 420a can point you in the right direction. just make sure the manifold is tubular rather than cast. cast manifolds are OK but tubular are alot more durable and will net FAR better flow characteristics than that of a cast manifold. Of course, as with the 4g37, you also have the option of having one custom fabbed.
the next step is finding a Wastegate that works with your turbo. Most sites sell the wastegate with the turbo. SBR has an amazing list of wastegates you can buy, along with a large list of turbos. Also, keep in mind that some turbos, like the 14b and 16g, are internally wastegated, which means you dont need to buy one of these.
As far as BOVs go Please, PLEASE do yourself a favor and get a stock 1g BOV or one that vents back to the intake rahter than the atmosphere. Venting to the atmosphere SEVERELY upsets the AFR, sometimes enough to drown the motor between shifts. If you do want to vent to the atmosphere then you will need to spend countless hours tuning the crap out of your fuel and air mixture. Worth it? As for the 420a they do not have a MAF so your only option is to vent to the atmosphere and tune to compensate.
Here is another curveball. You will need a 3" downpipe. for you 4g37 owners your only choice is to have one fabbed. shouldnt be too expensive as there is not much to them. As for all of you 420a guys and gals, you have the mentioned option or there are a few compnanies out there that produce them. just make sure it has a 3" diameter. If you are running relatively low boost a 2.5" would suffice but might as well get a 3" if you ever plan on running over 10psi.
upper and lower IC piping.Same as above but the lower piping you may opt to use a length of aircaft grade hose make sure its the good stuff tho and not radiator pipe. I however prefer to have it fabbed.
Let's see.. next up is intercoolers. FMIC, SMIC, it doesn't matter. unless you plan on big boost and even bigger power (only applicable to the 420a obviously lol) then a factory SMIC should be fine.
Tuning is another thing that relys heavily on personal preference. There are many options to tune your newly turboed DSM. These include: One of the three versions of Apexi's AFC (SAFC, SAFCII, AFC Neo), or a standalone unit such as AEM or haltech. The AFCs are the easiest to use, however, once you start running really big injectors (around 550cc) then you will start to notice the fuel mappings become pretty crazy and uncontrolable. The final option is the standalones. AEM and haltech are both amazing but also expensive as hell. If you can afford them, though, they are the best option.
Let's see.. whats next? Oh yes, fuel upgrades.
- Injectors: for the 1.8 just throw some factor 450cc injectors in and be done with it.. any bigger is way overkill. For the 420a it pretty much depends on how much boost you plan on running what internal mods you have etc... if your only running around 10-11 psi then 450cc will suffice. if you plan on running more 650cc is probably your best bet.
As for Oil lines, make sure to use braided stainless steel oil lines...nothing else.. they aren't normally available over the counter at most auto parts stores but you can usually find them at hot rod shops or even online (Summit Racing has them). You can tap the oil feed off of the place the oil pressure sender screws into. Just screw in a T-fitting behind the pressure sender. The oil return will depend on your turbo. You will need to drill, tap or weld an elbow onto your oil pan for the oil return. If you use an oil cooler, hook it up to the oil return from the turbo. That's where the oil is going to be its hottest. We want it at about operating temperature. Nothing below.
Oil coolers are of course optional but I HIGHLY reccomend one. a simple 4-pass oil cooler is rather cheap, only around 100 USD, so do yourself a favor and get one. It will save you many headaches in the future.
Your only real choice for an intake is to have one fabbed. depending on your turbo and how your IC piping is set up you MIGHT be able to fit a turbo for a GS-T or GSX on there but it would be much easier just to have one fabbed. I also reccomend a good filter such as K&N or something similar.
With a turbo app you will want to get your compression as LOW as possible without sacrificnig too mucch performance. using two head gaskets you will get around 8-8.2:1 depending on the manufacturer. with the 1.8 the pistons are domed. To me, adding another headgasket is the same as increasing the deck height, which doesn't change the geometry of the chamber as much as different shaped pistons, and doesn't change the behavior of the engine as much as shorter connecting rods would. The quench area in the chamber is different, but since the pistons are domed rather than dished, they don't have that foot-ball shaped quench area, they have a boomerang shaped area. the geometry of the 420a much different so this will not apply to the 420a. Upgrading the internals of the 420a is HIGHLY recommended and REQUIRED for boosting over 8psi.
You will also need a Manual Boost Controller or Electronic Boost controller (I prefer manual along with many other enthusiasts) SBR makes a really good MBC for merely 45 USD.
Next up - Boost gauge. The brand is completely governed by preference. I chose Glowshift but that is just me. Many people prefer AEM or ProSport.
Wideband - again, a luxury. but I HIGHLY recommend one.. will make your life SOOO much easier. (rather costly tho... and be sure to get the AEM UEGO... only one worth the money...)
Also, something that I probably should have mentioned MUCH earlier. Make sure to get 2.5-3" piping from the cat back. whichever you choose make sure to get a muffler and cat with the same diameter.
I hope this info is of help to someone. I just thought I would make an entire post dedicated to this since so many people liek to ask about it. Maybe a sticky would help?
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Turboing A 1.8 Or 420a
Jul 5 2008, 09:16 PM
