I get a dyno emission test every year here in Colo. In my town (Colo Springs), all the stock 7.3s seem to generate 205-215 rwhp on the dyno. My truck did 184 the first year, 175 last year, and 177 this year. Prior to this last test, I did the hutch mod, a 6637, and tightened the intercooler boots, which were notably loose. I have done a boost-leak test. Correcting for my oversize tires puts me at 184 hp. The dyno guy commented that opacity is kinda low (1-2%) and that he suspected 'not enough fuel'.

The truck runs great and I got 17.5 mpg on the highway the other day - no complaints there. I hate to mess with a good running stock engine.

If I add gauges, would I see low EGTs if there were not enough fuel? Would an AE help me possibly spot the problem? Where should I go next? I have cleaned the EBP tube and boost is 15-16 max at 7000'.

Thanks!

 

First of all, I don't think your EGTs will be lower due to "not enough fuel." The fact that you are getting respectable gas mileage seems to indicate things are running fine. But, if you think there is a fuel problem, make sure you are not getting any air in your fuel lines (Hutch mod is good to prevent, as long as you replaced the fuel lines all the way up to your fuel pump). May want to put a fuel pressure gauge on your fuel bowl (pre or post filter) to make sure it looks good. Your FPR may have a slight restriction, but your economy looks really good.

Make sure your fuel bowl is cleaned out well under the heater plate / element. Sometimes crud gets built up in there, and will definitely restrict fuel. That's free to do, except for maybe replacing your fuel filter while in there.

As for HP, you will want to add gauges BEFORE doing any major HP enhancements. Small enhancements would be things like a HP oil crossover hose, a fuel crossover "regulated return," etc. Maybe remove your AIH and put a plug there ($8 mod). Open up your exhaust with either a straight-thru muffler or a 4"-back system. To get real HP increases, things like a chip, upgraded injectors, etc. are what boost things bigger.

Overall, if your truck is running fine, getting great mileage, and you don't NEED the bigger HP for any particular reason...why mess with a good thing? I don't NEED it for towing or anything, but like the truck to accelerate faster. I love the power. It's a want, not a need.

 

Thanks! I did replace all the fittings up to the pump and installed a low-side fuel pressure gauge on the bowl. It reads 50-60 or so, depending on engine temperature. The fuel filter is clean and I installed 30 micron filter after the tank, as part of the hutch mod.

I would like to get my stock horsepower back before considering tunes....

 

Keep in mind that at 5000'+ your hp will be lower than at sea level. Because of the turbo maybe not as dramatically compared to a normally aspirated motor but 10-20% at 5000' is pretty respectable.

 

Well, that all sound perfect. So, I think the guy's comment about it not getting enough fuel is wrong. Your PSI numbers look great.

Are you sure you don't have a boost leak somewhere? Definitely check your up pipes, as they can lose a lot of boost if leaking (mine are leaking on HIS Excursion). Even a pinhole in one of your many boots can cause a boost loss, and therefore HP is lowered.

If you get your valve covers off at some point, run the engine to see how the injectors are performing.

I'm no expert, so I can't think of anything else that's obvious at this point.

 

Am I missing something?

 

Duck Fan wins the prize -you're too high to get full HP. You mentioned you're back to the original HP after your repairs/mods this far, it sounds like you're done getting it to run correctly as stock.

• 17.5 is pretty good for 6000 ft.
• 15-16 boost at 6000 ft. is good as well.
• 184 on the dyno looks like your magic number (new and now).

You can keep trying new and more exotic things, but I think you've peaked your economy for 70-75 MPH. There might be a little room (very little) for improvement if the 17.5 was at 60-65. I got 19-19.5 MPG at 1200-1500 feet going 65 MPH, but a bump to 75 take it down to 18-18.5 MPG.

I had 17 PSI boost max at 600 ft before mods. Adding bellowed ups was part of the mod process, do you have soot building around any of your exhaust components?

You mentioned AE. AE is very helpful if you have somebody to guide you, a manual on the truck, or you are really technically savvy. My AE pointed out a bad HPOP, which explains why my acceleration is better if I back off the pedal. The readouts are fine, but recording the data on the road is where I'm finding the real usefulness of the AE.

If you want more power, you will need three things: Gauges, more air in and out, and a tuner dialed for you altitude. Some say air out isn't that important, but my 4" helps my stock tune with boost.

 

Steve, my 7.3 probably doesn't make the power that many do. I get great mileage, no oil consumption, quick reliable starts, good (enough) pulling power and smooth running throughout the power band. So....... I'm happy ! It's bone stock except for the air filter and exhaust and a trans cooler that I haven't added to my signature. Would I be willing to "wake up some problems" for a few more horses? No way...... I figure the planets have aligned, all the parts like each other and play well together. An engine with over 200k has earned the right to be in the groove it enjoys. I figure this truck is like me, a little long in the tooth, set in its ways, has a routine , doesn't like change and will do anything for you but "her way".

To each his own, we are all different and I respect that. If you want more power go for it and who knows..... you might get me motivated to try something new! Meantime I'm gonna keep chugging along ! Keep us posted buddy and I'm sure there are folks on here that can help you wake that beast up and have her shaking the ground !!!

 

Wise words. I opened a real can of worms when I tried to add more power and fuel economy. I'm finally winning the battle, but at the cost of blood and treasure. If I had it to do over, would I stay stock? No freaking way! I have great MPG and I now know better/cheaper ways to get where I'm at, but more to the point... you can never go back from the rush of poking a tuned 7.3L monster with a stick.

 

You are so right Tug...... It's the devils candy !!!!!

 

With the covers off, you can watch how the oil is being discharged by the injectors, which can determine if one is not performing normal. It should not make a mess.

Of course, once your VCs are off, you can also ohm your glow plugs and injectors, etc, and make sure your harnesses are plugged in correctly (they tend to come loose over time, if they are the original design). And, since you're already in there, might as well make sure EVERYTHING is torqued-down to the appropriate specs.

C125Bob: Glad to hear you aren't planning on "fixing a problem that doesn't seem to be broken." As I said earlier:

 

Hey, to each his own I say. But.... I'm still thinking as long as the 250 is doing the job I'll have fun with my Jeep Wrangler, what the heck !

 

OK,

lol

that comment just gave me a vision of someone standing beside the truck with the valve covers off, and the engine running, saying "oh ya, looks good!" lol

 

Before you get to far pulling things apart try this. Take a look at the pigtails coming off the valve cover on the drivers side. They might be burnt/melted and not seating correctly. Clean them up and see how it runs. You will need to replace them but in the meantime you can reclaim some of your hp loss. (I know this from experience.) Oh yeah I live in Colo Springs also and we go to the same place to have our trucks checked.

 

I have been offline for about a week. Thanks for all the great advice.

What's odd is that after rechecking my dyno numbers (I was wrong in my earlier posting - my old numbers were in the low 190s), my power has actually gone DOWN after adding the 6637, fixing the boost leaks, and doing the hutch mod.

Friends have cautioned me to leave well enough alone, but I'm a gearhead and like to have all my stuff performing as well as it can/could. I will pull the valve covers one of these days to replace some/all of the glow plugs and I will check injector torque values and other issues. I believe my injector connectors are properly connected and not burned/corroded.