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Okay, just another air induction Idea and question.......

Discussion in '1982-Present GM Diesel' started by mpascino, Mar 14, 2002.

  1. mpascino

    mpascino 1/2 ton status

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    I have a 6.2 suburban on 3/4 ton axles with about 32 inch tires and 3.73's. On the highway my max speed is around 65 MPH, loaded up. I can get the truck to move quicker but I really have to get on it to do it, which I don't like doing. It's not that I want to go faster, I just feel like I really have to push the truck to keep up with upstate traffic. I have a 700r-4 with not to many miles on it. When normal driving around town I have no complants, powerwise. My first question; Will swaping to a j intake really make that big a difference and if so any one have numbers? Second hair brain Idea.........A lot of newer sports cars use ram air induction to increase air flow at Highway speeds, what do you guys think about trying to do something like that to a diesel? I figure at 60 there is a lot of air flow, why not try to use some of it? What do you all think. Again, I could be completely off the wall on this one, but then again that's what the forums are for.
    Thanks for any input in advance,
    Mike
     
  2. arveetek

    arveetek 1/2 ton status

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    You're exactly on the right track!

    Lee Swanger over on the Diesel Page made his own air intake modifications by enlarging the air cleaner to accept two air filters stacked on each other, making a new snorkel for the air to enter the air cleaner, and the using 4" hose all the way to the grill to get a sort of ram air intake. The stock air cleaners have that larger silencer hanging off the side, and if you'll notice, the hose that goes from the grill over to the silencer is terribly reduced right there. That silencer is restrictive. Getting rid of the silencer and using unrestricted hose from the grill to the air cleaner is a great start. Modifying the air cleaner to get more air in is also a good idea.

    I believe that the later model trucks get their air from the grill in a different fashion than the early style trucks. I believe that the older ones basically have a hole in the grill for air to get in to the intake hose. The newer ones have a sort of s-trap to make sure water and snow don't get into the intake. If you don't worry about getting snow and junk into your intake, you might look at using an early style intake opening in the front cowl.

    As far as J code intakes go, I'm going to try and find out once and for all how much power, if any, can be gained just by swapping intakes. My '81 C-20 diesel conversion has a C code intake (EGR) on it right now, and I've got a single-plane, open-plenum J code intake to put on it. What I'm going to do is, use a G-tech meter to record some 0-60mph times before and after, and also tow a trailer up a hill to record top speeds, also before and after. Hopefully this will help determine how critical the intake is by itself.

    I've seen lots of performance articles where they've swapped intakes, but they've also done other mods at the same time, so it's hard to tell how much the intake manifold itself played in the improvements.

    Hopefully this weekend I can get this all done.

    Any way to get more air into a diesel will result in more power. My next project after the intake swap is to install a turbocharger, the ultimate in air induction!!!!

    Casey
     
  3. Tybee

    Tybee 1/2 ton status

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    Are you sure you have 3.73 and your overdrive is working? I have 3.73s, 700R4 and when I had my 31s I could do 80 easy, I know its a burb but there cant be that much of a difference.
     
  4. arveetek

    arveetek 1/2 ton status

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    Yeah, Tybee is correct. There is probably something wrong with your fuel injection system that needs to be checked out if you can't get above 65 mph without much trouble. I had an '86 Suburban, 6.2L, 700R4, 3.73 gears, and 26" tires, and it would cruise all day long above 70 mph. My '81 with 6.2L, 700R4, 4.10 gears, and 27" tires will do the same. My '86 K-10 doesn't like to go above 70 mph, but that's just because it has no overdrive.
     
  5. mpascino

    mpascino 1/2 ton status

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    I am positive on both, the working OD, and the 3.73's. On level ground there is no issues. When I hit the open road and the terrain varies is mostly when I have problems. the slightest hit of a upgrade and I get passed by rigs and school buses.....
     
  6. arveetek

    arveetek 1/2 ton status

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    Well, then we definitely need to find out what is wrong with your truck. You shouldn't have a bit of a problem maintaining speed uphill, though you'll probably have to downshift into third.

    How many miles on the truck? When was the last time you changed fuel/air filters?

    Casey
     
  7. mpascino

    mpascino 1/2 ton status

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    Truck has about 153 K on it, transmission was done 20 K ago, filters prob about 6 k ago. Motor also had head gaskets I believe like 30K ago right before I got the truck. Also some more info, the engine is very loud, but I have been told that the 6.2 were always very loud, you think it's possible that the injector timing is off, is there any way to check besides seeing if the the lines between the injector pump and the engine is lined up?
    Thanks yet again,
    Mike
     
  8. arveetek

    arveetek 1/2 ton status

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    Define loud......do you mean it has a lot of diesel "rattle" or "clatter?" If so, that's hard to say.....noise is very subjective.

    In my opinion, GM diesels are very quiet compared to the Ford and Cummins engines. Most folks don't realize that my truck is a diesel until they walk right up next to it.

    The lines on the pump and engine block are more of a guide. From the factory, the scribe marks should be lined up, but if the pump has been removed, worked on, replaced, etc., then those marks are just a general rule. They should be lined up, and no more than a 1/4" apart at the most.

    If you look at the lines, and the line on the pump is more than a 1/4" to the right of the line on the block, then the timing is advanced too much. This could cause excessive clatter, but it shouldn't hurt performance very much.

    If the line on the pump is to the left of the line on the block, then the timing is retarded. This would make very poor performance, but I'm not sure that it would make a noisy engine.

    If the lines are well apart, you might loosen the pump and move it to get the marks to line up.

    I would definitely find somebody with a diesel timing light to check your timing.

    Casey
     
  9. OFFRDK5

    OFFRDK5 1/2 ton status Premium Member

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    I took 4" PVC pipe and made my air intake system. I took a rubber 3" to 4" converter at the air breather and used a tie wrap to hold it in place. Works really well. A bit louder, but who cares about a bit of noise? Mine also converts for underwater applications......
    <a target="_blank" href=http://community.webshots.com/rz/r1/3/7/76/24530776IMCZEsMdHc_ph.jpg>http://community.webshots.com/rz/r1/3/7/76/24530776IMCZEsMdHc_ph.jpg</a>
     

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