Increase horsepower or max speed or engine power

Discussion in 'Mechanic and Repair' started by deeps, Jan 2, 2006.

  1. deeps

    deeps LawnSite Member
    Posts: 6


    I have a 1997 Chevrolet W4 tiltmaster 14' box truck. Its the same as any Isuzu Npr trucks. Do anyone know the best way to increase horse power or engine power without damaging the engine or anything else. Right now it able to curse around 65, but I want it to do 75. What the best to way get another 10 mph out the truck. It doesn't have any RPM meter or anything, which makes things harder for me. Thanks
  2. DEEJ

    DEEJ LawnSite Member
    Posts: 230

    To increase ground speed you could swap out the final drive gearing by replacing the differential of the entire axle assembly. Doing this will increase ground speed, but there is a trade-off with power for acceleration, hill climbing etc. Think of your mountain bike. Go to a smaller sprocket in the rear (the differential) and the bike is capable of going faster with the same pedal speed (engine speed). BUT, does the engine have the power to work with this higher final drive gearing?

    What engine is in the truck? Is it tired, what is the tune-up status, is it regulated somehow (from a previous use) to 65mph, is the matting under the gas pedal preventing the pedal from being pushed further, is the throttle cable loose or stretched prvenbting the throttle from being opened fully (seen this a few times), will performance options help with this engine ... so many questions and possibilities ...

  3. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Posts: 9,544

    If the truck has a 4 banger diesel not much you can do with it if you have one of the trucks with a 350 gas engine then you have some options. Those trucks are usually geared pretty low in the diff your probably running out of rpms.

    I converted the mph to kms and you want to push the truck that fast :confused:

    The cheapest option is trying to get some taller tires does the truck have the 16" wheels or the oddball 17" wheels ?

    If you could squeeze a set of 255/85R-16s onto the 16" wheels it will give you some road speed on the flat but would sure knock back the pulling power.
  4. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613

    You really need a tachometer on that engine, we need to know if this is a diesel application, as stated you are likely running out of rpms or against the governor. If you do get a tach on it, max engine rpms is probably going to be 2800-3400. Or, if you could figure out what your rear axle ratio is probably 6 something :1, we could better advise on the tire size to help out. Get a tach!

    UNISCAPER LawnSite Bronze Member
    Posts: 1,426

    Living in San Jose, you have about the same terrain as we do here. Hills and Valleys. Those W series trucks work well on tight short routes with the diesel engine, which is a pretty reliable unit. It is just a gutless wonder.

    If you want more top end, take that engine out and install the 350CID Chevy motor that comes in the W series. You will be able to hit 90 without any trouble. Other than that, if you gear the rear higher, that engine is so gutless you will need a few more transmission gears. As far as I know, they did make a 175HP version of that engine for a few years, I'm not sure it is legal in this woe is me hug a tree environment we live in. You gotta love liberoids for deciding what works best for you in your business. Thats about all I can offer. You could trade for the 4500 series and go with a Dmax engine, but that's going to cost some money.
  6. deeps

    deeps LawnSite Member
    Posts: 6

    More information add to my question. Truck is a 14' box and diesel engine, which only 90,000 miles on it dispute its 1997. I just brought so I was trying to make it go normal highway speeds, which is about 75mph. Its a 4 cylinder engine 3.9L. its in preety good condition. Thanks
  7. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Posts: 9,544

    You are trying to push a small engine a little too far look at the wind drag you have. I think you are SOL on trying to get the truck to go faster just suffer with going a little slower.
  8. deeps

    deeps LawnSite Member
    Posts: 6

    The reason because I was trying to push this engine little farther is that I have rented these trucks before, which went up to 75mph. The only difference was that is truck is 1997 and the one I rented was 2003 and 2004, but other then that they were identical trucks inside out.

    OR If someone knows what things can I add to the engine to increase power to make it go little more faster like extra parts you can add to cars to increase their power. I am not taking about 0-60 staff, but on the highway like I-5. Thanks a lot.

    CLARK LAWN LawnSite Silver Member
    Posts: 2,526

    the 03-04 you rented where speced out different when ordered. all depends on the rear gear. when i used to work on trucks we had a few of them they have no top end at all 65 is about all you are going to get out of it. sorry for the news

    UNISCAPER LawnSite Bronze Member
    Posts: 1,426

    That 350 Chevy is sounding like a better option all the time.

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