I recently bought a 2002 GMC 2500HD Duramax. I struggled to get 50 MPH while towing our approx. 6,800lb camper up the mountain passes in Colorado where I live. Once the engine built up speed it usually didn't have a problem maintaining the speed unless I had to brake (which was an experience when the Allison tranny dropped a couple of gears and red lined the engine to "assist" with braking). I need more power and have read numerous threads. I am confused with what I've read. Several threads state that the only way to increase power is to use a tuner and that intakes and exhausts do nothing more that lower EGTs and make noise. Why wouldn't increased airflow in and out increase power? One thread I read stated that the stock exhaust was plenty, swisscheese the airbox and use a tuner. Another stated start with an intake, then add an exhaust and then add a tuner if desired. Anyone's experience and advice would be great! I'm not after tons of horsepower for having fun (although if I could afford the thousands of $ I would), I just need a reasonable power increase to tow our camper relatively easily uphill.
JKG
2002 GMC 2500HD Duramax, stock as the day she was born.

There is something wrong. You should be able to pull 6800lbs as fast as you want.

Any idea what could be wrong?

I had the same problem, got the injectors replaced and it is PERFECT!

Are there any other problems I should be having that would let me know the injectors need to be replaced. The truck seems to run fine. That's what I get for buying a used truck. :mad: Would a bottle of Stanadyne or similar product clean the injectors and fix the problem or do the injectors have to be replaced? I can call a dealer tomorrow, but I would like to know a little about the problem before I call.

Do you know when the filters were changed, specifically the fuel filter? I'd start with the basics first. Change the oil, oil filter, tranny filter and fuel filter, then see where you are.

A friend in town has a 02 D/A that he bought new. At around 45k the thing was running fine around town and when driven normally----but when pushed or when towing it would just lay down. The injectors were the problem and was fixed under warranty. Guess it runs fine now. RR.

OK, thanks for the help. I'm calling GMC this morning. And yes, I've been on top of the basic stuff since I bought the truck.

To answer the part of your question about more power. Before you add a power enhancer, swiss-cheese the airbox and add a 4" exhaust. The result will be a cooler running truck that is more responsive. Add whatever power enhancer you want, using either a "tow tune" or a conservative setting. If your truck is running good to begin with, this combination will knock your socks off pulling your trailer.

Thanks Fred, that was the answer I was looking for before the injector problem sidetracked me. By the way, the dealership called me and said they can't find anything wrong with the injectors. They said their computer isn't giving them any codes, so what gives on the power. Anyone else tow in Colorado over the mountains, I-70 through the Eisenhower tunnel, Berthoud Pass, Vail Pass etc. in a stock truck?

Not to ask the stupid question but you were'nt in tow/haul mode were you. I had a ford before I had the duramax and just assumed it work the same. The first time I towed my trailer up a grade I was in the tow mode and had less power then my 460. Worked much better with it off.... Also mine is a 2002 GMC crew and I did not use additives for the first year or so. During that time the power seemed to decrease and so I started using stanadyne. It took several tanks but my mileage and power are back up. Additives are like motor oil - there are different brands that work different ways and everyone has an opinion (which no one seems to mind sharing) on which is better but the dearler and the local diesel injection service both recommeneded the stanadyne so I went with it. If you havn't yet you can run a vin check (in the approriate forum of course) and see what work has been done on your truck.....Bill

To answer the part of your question about more power. Before you add a power enhancer, swiss-cheese the airbox and add a 4" exhaust. The result will be a cooler running truck that is more responsive. Add whatever power enhancer you want, using either a "tow tune" or a conservative setting. If your truck is running good to begin with, this combination will knock your socks off pulling your trailer.
:exactly:
The only thing I'll add is get some gauges.

Your target tow RPM is about 2100. It does it's best between 2100-2500. Sometimes it's best to tow in 4th if you have OD lockout.

I would be inclined to get your truck dyno'd. It should make 240-250HP at the tires stock. If it does, start looking elsewhere than the motor.

If you are looking for more power, consider this:

Your stock exhaust is 3.5" dia. This is more cross-sectional area than a Big Block runs. It's plenty for a stock engine. Ditto for your intake. This is why your not going to see huge gains with a stock motor by opening these up.

Put a mild tuner on it. You'll be VERY surprised how much it wakes the motor up. Even a 40HP tune makes big gains in acceleration and climbing when towing.

Exhaust will make a nice difference. I've dyno tested same truck same day before and after my exhaust was installed mapping HP, TQ, EGT, and boost which is more than any exhaust mfg I've ever seen do.

Let's say a $400 exhaust picks up 25rwhp on a stock truck (unlikely, but just to make point). A $400 tuner will pick up at least 40rwhp. No comparison.

Thanks for all the help/opinions, McRat seems to make alot of sense. I have decided, however, that I will slowly add all three performance mods. First will be the exhaust (based on what Kennedy wrote and what others have written about EGTs), then the tuner and then an intake if I find one that filters air well (like the ProGuard7). Anyone have a used mild tuner collecting dust they would like to sell? I like how quiet the engine and turbo are, just how loud does the turbo get with PG7 intake?

I wouldn't start dumping money on aftermarket products yet. You have something wrong with your engine. My 04 lb7 will run up the Colorado mountains towing my 13K fifth wheel all day long, and at highway speeds. Start by checking fuel filter or injectors.
Dave

I brought the truck in today and the dealership told me they didn't get any loss of power codes or show any injector problems on their balance test. He said without any codes or injector failure indicated GM will not do the warranty work. He said he test drove and didn't notice any problems. But neither do I under normal driving. It's when I put a load on the engine and go up grade that she won't go much faster than 50 MPH... and my camper is about half the weight of yours. The fuel filter is good for another 5K, but I will change it anyway. I use Stanadyne in the fuel already. The oils everywhere in the truck have recently been changed and I do frequent engine oil/filter changes myself. Do you use the tow/haul button, someone in this thread stated he thinks he loses power using it. Maybe the 04 Duramax is just that much better than the 02.

I live in Oregon and the state I swear was born on a mountain.With that said I tow my camping trailer at approx.8000 lbs.I set cruise at 70 mph and roll over just about any terrain.Truck is stock.Scary what some mods would do to engine.I'd probably kill myself or somebody.

Jkg,
What hills are you climbing under load, I70 west out of Denver or other? I tow in T/H mode. I just got back from Arizona pulling my 5'er and 3K lb boat and never went under 60 except going downhill, that was on I40 and I25 however. I still think you have a problem that aftermarket stuff won't fix. Good luck
Dave

To answer the part of your question about more power. Before you add a power enhancer, swiss-cheese the airbox and add a 4" exhaust.

Fred, what exactly do you mean by swiss-cheese the airbox? There is one LARGE opening in the box currently. Are you suggesting that on the other 3 sides to cut more holes? Will this really make that big a difference in a stock truck just running the Hypertech?

Thanks for your help.

http://www.kennedydiesel.com

Look under tech tips.

Ben

http://www.kennedydiesel.com

Look under tech tips.

Ben

Awesome! Thanks.

ask the dealer what the frp fuel flow rate is and ask if they can ramp the fuel pressure to full pressure. frp fuel flow rate should be 800-1200 at idle and should make 158.5-160mpa of fuel pressure when ramped with a tech 2 if not with in spec theres a problem.