Getting cheap power from your 6.2 diesel

[Sterling]

Its about time someone writes up about the cheap power mods to make your 6.2L GM Diesel get up out of its own way.

I will list from lowest to highest cost

1) Turning up the Injector Pump - FREE

There are many how to write ups on this, so I wont go too far into detail to save space. But essentially what you are doing is setting the MAX fuel output of your DB2 injector pump. So now when you slam your foot to the floor, you have more fuel going to the cylinders. In diesel engines, you really can't run too rich unlike gas engines. All you do is just waste diesel (black smoke) but it really doesn't effect preformance. That is why high power diesel trucks shoot thick black smoke when doing a 1/4 mile run, because they want to use every last bit of AIR in the engine. At this point, your only limiting factor is air, hence why many put turbos on their diesels, to shove more air into the engine. Just don't get too carried away with turning up this pump, your Exhaust Gas Temperature goes up when you do this, and if it gets too high (over 1200 F) you'll start melting things. Usually an 1/8th of a turn of the fuel set screw (allen screw) is safe.

2) Cold air intake - $10

What you want to do here is bring fresh cold dense air into your air cleaner housing. My truck came with an intake tube that went to a rain deflector on the passenger side of the grille, just above my coolant bottle. All I did was get expandable HVAC 3" ductwork (the metal kind) and a 3" to 4" HVAC adapter. The stock air deflector (keeps rain from entering your intake) has a 4" output. I decided to keep the stock deflector because it takes in fresh air from up front, and flow will increase as my speed increases, and it flows pretty well. I then used the adapter to bring that intake down to 3" so I can use 3" hose. Then I ran the 3" duct/hose to the air cleaner box which has a 3" oval input. All I did was sort of bend the metal hose into an oval shape, and connected it to the air box with a rubber sleeve that used to connect the air box to the stock air hose/air muffler.
Instantly I noticed about 15 HP increase, and a lot less black smoke at full throttle, which means more fuel is being burned due to more air entering engine. Get rid of that restrictive intake muffler, and run $10 of HVAC hose.

3) Fuel Filters - $10-$20
This is a general maintenance item. If your fuel filter(s) are clogged, you aren't getting good fuel flow.

4) Fuel LIFT pump - $20
The mechanical fuel pump on your engine. Yeah these wear out over time. And your injector pump pulls enough pressure to keep the engine running if this is bad. Get fuel flowing to the IP again with a new Lift pump if yours is bad. Easy way to check is to loosen the output line from the Lift pump and turn the engine over, if fuel comes out, its good, if not, better head to NAPA

5) Cotton "lifetime" air filter - $20-$50

We all know about K and N air filters. Well FRAM at one point made the "air hog" filter, which is pretty much an orange K&N filter. Rock Auto still has some of these on closeout (fram stopped making them) and you can get them for cheap. They are the same numbers as fram tough gaurd filters, but instead of CAXXXX its PRAXXXX. I found mine on ebay. And if you cannot find a fram one, use a $20 off order of $50 coupon code at Advance Auto and get a K and N. As I said before, you want as much air flow as possible with your 6.2


6) Intake Manifold - approx $60

Most of our 6.2L came with EGR equipped manifolds. If you open your air cleaner, and see this big round thing in the center of the manifold, you have EGR. EGR is a big restriction for our engines, and let me be honest, stops properly functioning within a few thousand miles of when your engine first ran, due to poor design and soot buildup. And it blocks air flow. Lucky for you, many 6.2L were used by the ARMY that came WITHOUT egr. Many army surplus intake manifolds are being sold for very cheap. The best flowing manifold you can get (more air = more fuel that can be burned = more power) is the 6.2L HMMWV hummer manifold. It is a single plane manifold. The only mods you need to do for this is make a 3-4" spacer, because this manifold sits lower then your old one and your air cleaner box will hit the injector pump. I made my spacer out of 6" diameter PVC pipe I got at Home Depot, and just cut to the height I needed. Works great and is cheap. Make sure when you buy a new intake manifold gasket, you get the NON egr gasket, this gasket has a metal plate in the center EGR hole to block EGR gas flow to the manifold. I believe though, All of the Fel Pro gaskets for our engines come with the block off plates. Ive bought 3 sets and they all had them if you needed them.


Have fun hot rodding! also for those who know about the HMMWV headers, I would have mentioned them, but unless you can weld, good luck getting them to not dump out into your firewall.

-Sterling