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Most users ever online was 31 on Mon Feb 27, 2012 6:49 pm

    420a Turbo path


    Car : 96 RS
    Posts : 137
    Reputation : 0
    Join date : 2011-11-30
    Location : Boise, ID

    420a Turbo path

    Post by Shake_Zulla on Tue Jan 24, 2012 6:05 pm

    Turboing a 420A is not as easy as one would think but it is possible. In fact there are a ton of turboed 420a's out there! It is a lot of work though and a lot of parts. Here is a walk through on what you will need to build your own turbo kit! Now this will show you everything to get for a standard 8PSI build. The internals of the 420A are not forged so they will not handle more than 8psi. In fact even running this amount of boost could damage your pistons so be warned. However, there are plenty of people out there running 8psi on stock internals on 100,000 mile plus engines. What if you want to run more then 8psi though? Well watch for my next article on "building a 9+psi 420a", coming soon.

    Step 1: Exhaust Manifold
    Difficulty of install: Easy
    A turbo requires it's own special exhaust manifold. These will come in two different styles depending on if you want an external or internal waste gated turbo. If your goal is the standard 8psi build and you don't think you will ever want to run more I would suggest going the internal waste gate path. Chances are you will be able to save a little money and an internal waste gate turbo works really well on lower pressure systems. "Log" style manifolds are more simplistic and a lot of times less expensive, however higher priced manifolds will flow a lot better.

    Step 2: Turbo
    Difficulty of install: Easy, depending on room (some styles require smaller radiator fans or a deletion of your ac and power steering belt.)
    OK time to buy a turbo! So your going to want the biggest turbo you can find right! WRONG. Now it's time to think about what you want out of your car. Smaller turbos will spool faster and give you more power throughout your whole rpm range while bigger turbos will produce greater gains at higher rpms. This is referred to as "Spool rate" and if your goal is to stick at 8psi you do not need a big turbo. Depending on your goals or if you bought the manifold already you will need to choose an internal or external waste gated turbo.

    Step 3: Waste gate
    Difficulty of install: Easy, depending on room.
    If you opted to get the internal waste gate then you can skip this step. Waste gate size will depend on what your exhaust manifold requires. This is what allows the extra exhaust that the turbo does not need to escape. They have different springs that will open and this prevents you from exceeding your desired psi. It is important to note that there are other things that can control this (boost controller) but its a different topic for a different time.

    Step 4: Blow off valve
    Difficulty of install: Medium
    A blow off valve is often referred to as a BOV. This is what releases the pressure when you let up off the gas. If you do not have a BOV when the throttle plate closes it will cause a surge damaging numerous parts. Some people recirculate this back into the intake after the throttle body while others just vent it into the atmosphere. Difficulty of install depends, if you buy a intake pipe with a flange it will be easy, otherwise you will have to weld a flange in.

    Step 5: Intercooler and piping
    Difficulty of install: medium to hard
    An intercooler is not required for a turbo system but is strongly recommended especially at 8psi. Basically a turbo compresses air and cold air compresses better than warm air. There are 2 main styles or intercoolers and that is a side mount and front mount. You can get a better surface area with the front mount but they are a little more expensive. Install can be difficult due to the piping because most people have to cut bigger pathways. Again, like the turbo, bigger is not always better. You want a lot of cooling area, however, you still want your air to flow well through the intercooler. This link provides pictures of which intercoolers flow the best.

    Step 6: Downpipe
    Difficulty of install: Easy
    A downpipe connects the turbine outlet to the rest of the exhaust system. A muffler shop is your best bet to get one of these if you lack the fabrication skills. Be sure to include a O2 sensor bung and if you have a external waste gate its not a bad idea to connect that downpipe with this in one solid Y-piece.

    Step 7: Fuel pump
    Difficulty of install: medium
    Adding a turbo means you need to add more fuel and the stock fuel pump is not up to that challenge. Will the car run with stock? Well... yes but at mid to high rpms you will be doing damage to you internals and you wont have a running car for long. It is pretty standard for people to go with a Walbro 255L so stick with the tried and tested.

    Step 8: FMU/SFMU
    Difficulty of install: Hard
    Ok so you have the ability to pump more fuel but because our car runs off a MAP sensor and not a MAF we need to trick it into pumping more fuel. A 12:1 FMU will do the trick. Install on the 95's AND SOME 96'S are a little bit easier but the late 96 model and up you have to add a fuel return line (write up coming soon). A SFMU will allow you to adjust your fuel but in my opinion a FMU works so save your money for a better fuel management system such as MegaSquirt.

    Step 9: Missing link/fuel cut defender
    Difficulty of install: Easy
    The thing that really sucks about a MAP(mass air pressure) sensor is that when a N/A engine is accelerating the pressure lowers so the ecu knows to add more fuel. Well when you add positive pressure the ecu doesn't know how much fuel to add so as PSI increases, fuel decreases and thats bad news for you internals. Now this only effects the late model 96 and up 420a's and there is two ways to fix it. First you can use something called a missing link, second you can use the more popular and more reliable fuel cut defender (FCD). Both will trick the ecu and in combination with the 12:1 FMU you will run a bit rich at idle but be in good shape and mid to high rmps.

    Step 10: Oil Lines
    Difficulty of install: medium
    Most turbos require oil so you must tap lines in your oil pan to run to you turbo then back down to your oil pan. Some turbos even use water in addition to oil to cool the turbo, however, this would be a bit overkill for our application.

    Step 11: Misc
    Difficulty of install: medium to hard.
    You will need some misc stuff to polish off your turbo kit. Besides the fittings you need for your oil lines you will need a cone style filter and a short section of pipe to go to the compressor. The valve cover will also need a little filter or oil catch can setup. You will also need misc vacuum lines and high pressure fuel lines.

    Strongly recommended: I would also suggest that you get a wide band and a a/f ratio gauge. There are tons of people out there that have had problems with their missing link or fuel cut defender and you want to be sure to not run your car too lean. I would also suggest you replace your head gasket with a MLS gasket and get some APR head bolts. Any time you add pressure your head gasket takes a beating so a new one is a good idea, remember though that a MLS REQUIRES you to take the block and head into a machine shop so they can make sure the mating surfaces are perfectly flat. I would also shave an 1/8" off the head bolt on the far front corner next to cylinder 4. Chrysler neglected to drill the head bolt hole down far enough on this one spot and that is why there are so many head gasket failures on the 420a.

    This might seem like a daunting list for some so here are some vender's that can you can buy these parts from.
    and ebay

      Current date/time is Fri Jul 20, 2018 12:26 am