For those who aren't familiar my truck is a 96 GMC Yukon with an '02 24 Valve, it is backed by a 6 speed Allison transmission. The tires are 285/75/17 and I have regeared so that at cruising speed (70 MPH) I am right at 1960 RPM. I am currently getting about 10 MPG and I am trying to figure out why. I run a Quadzilla on standard tune, level 4 and I have a bit of a lead foot but most of my driving is freeway miles. I also run a FASS 150 and a 5" straight exhaust with 4" down pipe.

 

Now then...at cruising speed I am approximately 20% throttle and my EGT's are in the low to mid 800's. My load ranges between 30 and 36% based on the slope of the road. The boost at cruise is 11psi and I never really paid attention to the IAT's until recently but they stick in the mid 130's; because of space constraints I use an air to water intercooler and I noticed a drip from the filler cap recently so there's a chance the fluid is low. I recently adjusted the valve lash and I have plans to clean the IAT sensor and MAP sensor in the next week but from what I understand about the sensors if they were dirty they would read low not high. I am admittedly not an expert in the field, in fact this is the first diesel truck I've ever owned or even driven.

 

So the question is: Where can I start looking for inefficiencies or out of service conditions that are burning extra fuel? I would really like to take the old girl to the coast in the spring but at 10mpg I'd need a second on the house. Any help is appreciated.

3 hours ago, NIsaacs said:

 

You need to find out what/why it is ingesting foreign objects. Is your air filter being eaten alive? You may have intercooler/engine damage.

I was using this for the air filter, mounted directly on the turbo inlet. That cute little chrome button in the middle got tired of being there one day and tried to escape through the turbo. Needless to say I'm running a different style filter now. I'm sure some small particles made their way to the engine but I'm guessing most of it is hung up in the intercooler. 

9 hours ago, Scottfunk said:

I believe it was 315. They said they should settle into the middle of the range once the seats wear in.

 

I don't have an exhaust brake yet, but I would like one. A 4" outlet would be nice too! Maybe a 35/40 with a billet wheel? hmmm...

 

Thanks for the info. Let me know how 315 does with your injectors.

 

My first question is do you have an HX35 or an HY35 turbo?

If you plan to get an exhaust brake I would highly recommend a turbo mounted one. The ones that go into the exhaust pipe are neat but take a while to build back pressure when braking, and tend to leak.  In your case, if it can be fitted i would go with an hx40/35 swap.

 

I do believe BD makes a larger turbo that will bolt onto their own exhaust brake that is larger then a 35w compressor wheel.

 

 

1 hour ago, Scottfunk said:

I was using this for the air filter, mounted directly on the turbo inlet. That cute little chrome button in the middle got tired of being there one day and tried to escape through the turbo. Needless to say I'm running a different style filter now. I'm sure some small particles made their way to the engine but I'm guessing most of it is hung up in the intercooler. 

 

I wouldn't doubt that this filter is the cause. These filters and other re-washable filters don't filter worth a poop.

 

18 hours ago, Marcus2000monster said:

Yea your compressor is toast. I wouldn’t buy a cheap eBay turbo they won’t last.

 

I'm going to challenge this. Do you have any first hand experience that dictates a turbo off of eBay won't last? I'm not talking about a random internet forum post either. Yes I realize that the general online consensus seems to be that buying eBay turbochargers is a mistake... But who here has personal experience with this and can speak to reliability?

 

Don't forget that a large chunk of purchase price with performance parts is based off of the brand name. Anyone that's researched push rods and valve springs for our engines will attest to this, and it doesn't stop there. You have to give a certain level of respect to the individuals that broke trail and performed countless hours of R&D to design these components... However at some point, guys like me get tired of being bent over and paying a premium for old technology with a slick brand name.

 

All I'm saying is don't discount a product just because it doesn't say HOLSET (or any other popular name) in big bold letters.

Edited January 2, 20196 yr by kzimmer
Typo

7 hours ago, kzimmer said:

 

I'm going to challenge this. Do you have any first hand experience that dictates a turbo off of eBay won't last? I'm not talking about a random internet forum post either. Yes I realize that the general online consensus seems to be that buying eBay turbochargers is a mistake... But who here has personal experience with this and can speak to reliability?

 

Don't forget that a large chunk of purchase price with performance parts is based off of the brand name. Anyone that's researched push rods and valve springs for our engines will attest to this, and it doesn't stop there. You have to give a certain level of respect to the individuals that broke trail and performed countless hours of R&D to design these components... However at some point, guys like me get tired of being bent over and paying a premium for old technology with a slick brand name.

 

All I'm saying is don't discount a product just because it doesn't say HOLSET (or any other popular name) in big bold letters.

Although somewhat indelicately said, I would mostly agree with this. There are basically three types of knowledge: the type of knowledge gained through personal experience, the type of knowledge gained through research, and knowledge gained from third parties. You could talk until you're blue in the face and you would never convince me that Craftsman tools are not the best mechanic's tools out there...personal experience. My truck has a Cummins engine but an Allison transmission...research. Not saying I'm right or wrong with either of those but I have a personal connection to the information and so I trust it. The trouble with third party information is that you have no personal connection to the information, so you can only validate or invalidate it through one of the other methods. There really just is no way to know without trying. That being said, I rarely rule anything out because of the label on it until I've personally evaluated it. I have a Harbor Freight MIG welder out in the garage next to my Everlast TIG welder. I only expect to get 3 years out of my Harbor Freight welder that I paid $200 bucks for, while I might hope for 10-15 years out of my $1000 Everlast. Does that make the Harbor Freight welder a bad value? For me, no. I forked over my money knowing that eventually I'd have to replace it. There's nothing wrong with buying an inexpensive turbo off of eBay as long as you go into it knowing it MAY not last as long as others. It may or it may not, but either way when it bites the bucket you'll know if it was the right choice for you and have the personal experience with it to know whether you'll make the same choice in the future.

I'm definitely a believer of you get what you pay for.

 

Example is I once replaced a HE351VE turbo on a 6.7 Cummins with a Napa reman due to oil seal failure. The Napa reman went bad less than 2 weeks later with a seized VGT. The genuine Cummins/Holset turbo was $1500 more than the Napa and probably would have not come back under warranty. This is just one story of many where Napa parts have failed quickly and I was performing discounted or free labor doing the job over again.

 

I'm a firm believer in oem parts only. Vatozone, Napa, and O'Reilly's do not have access to the quality parts such as you will get with Genuine Cummins. At least if a genuine Cummins part fails under warranty Cummins will actually reimburse labor fairly to where the chain parts store or eBay seller will tell you to kick rocks.

This is what I heard from few people that rebuilt turbos. EBay special turbos are a 50/50 chance you take, they ever last or don't and if don't they could grenade and cause serious engine damage. Personally I have too much time and money invested in my truck to put anything of importance on my truck that came from who knows where. If you got something for cheap just to beat on, sure why not. I have a buddy that can pice some junk together and beat the crap out of it and for the most part it will last, but would it trust it going from state to state, no..... 

Here in the odd duck once again buying mostly NAPA parts. Typically avoid Cummins parts excessive price that does not always mean quality. There has been a few things I bought from Cummins because it was cheaper then the Diesel Vendors.

 

Remember Cummins doesn't manufacture a lot of parts. They are reboxed with Cummins logo. I think there is only 3 companies the manufactures thermostats and Cummins is not one of them.

Edited January 3, 20196 yr by Mopar1973Man

1 hour ago, Mopar1973Man said:

Here in the odd duck once again buying mostly NAPA parts. Typically avoid Cummins parts excessive price that does not always mean quality. There has been a few things I bought from Cummins because it was cheaper then the Diesel Vendors.

 

Remember Cummins doesn't manufacture a lot of parts. They are reboxed with Cummins logo. I think there is only 3 companies the manufactures thermostats and Cummins is not one of them.

I'd have to agree for the most part. I sure learned my lesson with Spicer ball joints thinking I was buying quality with a brand name. I wasn't. Something like a turbo though I'm not sure I'd cheap out on for the reasons DF posted.

@Me78569 was another fell into the trap of buy OEM parts like Spicer ball joint and they didn't hold up.

Stop talking about Spicer ball joints, I just put a set of them in  although I did buy them from Sadler powertrain where they built a lot of axles and not from eBay I hope there is a difference

Mine came from Ventures Truck Parts.

I have Spicer axle joints on the shelf too that I'm scared to put in now if that makes you feel any better  

Edited January 3, 20196 yr by dave110

20 hours ago, Dieselfuture said:

This is what I heard from few people that rebuilt turbos.

Again... Heresay, and not personal experience. Of course people that rebuild turbos are going to tell you not to buy cheaper brand new turbos. Telling you otherwise would be bad for business, regardless if it's correct or not. I'm not saying that one should always take the cheapest path in life at every opportunity either, don't get me wrong. I just tend to take opinions with a grain of salt. Much like my opinion, of course you won't take it for its weight in gold, I'm a random person on the internet, haha. Trust no one!

2 hours ago, kzimmer said:

Again... Heresay, and not personal experience. 

 

Heresay is going to be what most people go on for turbos, and many other parts too. Not that many people replace them, and no one wants to do it twice so many are willing to spend the money on name brand.

 

I’ve personally only ran 2 turbos, but I’ve talked with several people over the years who haven’t had luck with no-name turbos. Not forums, but personal conversations.  So that’s not a personal experience, but it’s good enough for me. 

 

Yes, the internet is full of horror stories as most people don’t chime in when something works as advertised... but sell them a crappy part and they’ll tell everyone. Then again when I was younger and the internet wasn’t much of a thing I bought a lot of car parts store parts and I replaced them often! They just weren’t worth their price, but I had no way of knowing how many others had the same issues. So the internet isn’t all bad ?

 

I’ve been researching water pumps for my 4.0 TJ and almost bought a AC Delco (a brand that generally gets good reviews) for 1/3 the price of OEM. All my research led me down the OEM path thou, no complaints on OEM and lots of aftermarket complaints... some brands worse than others. 

 

I also just put a cheaper fuel pump in my VW Jetta, despite some reviews but it never leaves town... so it’s not as important to me as the Cummins or Jeep that I’ll head to the hills in.

 

Long story short, but buy what you want to spend your money on. Take others people experiences for what they are, realizing many are jaded but still normally valuable experiences. 

Well I got the new compressor wheel in today. Didn't see any drastic changes in EGT or Load% but there was some improvement. The guy at the shop where I got my injectors rebuilt said to expect to burn through a little extra fuel in the first 10,000 miles so I guess I'll just have to be patient. The improvement in power was DEFINITELY noticeable though. YEEHAAAAA!!! Ignore the tooling marks around the outside of the wheel that was just me trying to get the wheel off without pulling the whole cartridge. 

 

I use a diaper rash paste to check the alignment when I set up ring and pinions, it's basically fish oil with a zinc additive. Would this be a safe substance to use to wipe a little around the tip of my fuel tubes to check the seat in the injectors? I just recently read the specs on torque for the fuel line/fuel tube retaining nut and I grossly overtightened them. I don't have any specific reason to want to check but I'm a bit of a worry wart and even more of a perfectionist.

13 hours ago, Scottfunk said:

Well I got the new compressor wheel in today. Didn't see any drastic changes in EGT or Load% but there was some improvement. The guy at the shop where I got my injectors rebuilt said to expect to burn through a little extra fuel in the first 10,000 miles so I guess I'll just have to be patient. The improvement in power was DEFINITELY noticeable though. YEEHAAAAA!!! Ignore the tooling marks around the outside of the wheel that was just me trying to get the wheel off without pulling the whole cartridge. 

 

I use a diaper rash paste to check the alignment when I set up ring and pinions, it's basically fish oil with a zinc additive. Would this be a safe substance to use to wipe a little around the tip of my fuel tubes to check the seat in the injectors? I just recently read the specs on torque for the fuel line/fuel tube retaining nut and I grossly overtightened them. I don't have any specific reason to want to check but I'm a bit of a worry wart and even more of a perfectionist.

That wheel looks much better man! Should make a difference in everything. 

How is that turbo balanced? As a unit or each individual part?

On 1/5/2019 at 8:51 PM, Scottfunk said:

The guy at the shop where I got my injectors rebuilt said to expect to burn through a little extra fuel in the first 10,000 miles

 your kidding

Also make sure your check back side of compressor housing for Boost leaks with soap water,  I ended up selling mine with light coat off rtv

@pepsi71ocean I cant make up my mind on what injectors to get. Im thinking about a setr of genuine Bosch RV275s flow matched adnd popped to my specs. What would you have a set of RVs set at? 

15 hours ago, Dieselfuture said:

 your kidding

Also make sure your check back side of compressor housing for Boost leaks with soap water,  I ended up selling mine with light coat off rtv

Nope. I buy that one though because the seats aren't "lapped in" like a high performance set of valves would be. Now that I have a better understanding of how much pressure these things make it makes sense to me. If the orifice sizes are measured in thousandths of an inch then a ten thousandth of an inch variance from the manufacturing process could have a measurable effect. The tech that rebuilt them said he recently rebuilt his own injectors and went from 20mpg to 14. Believe me I'll be watching cuz crap mileage was what sent me on this journey anyways.

 

As far as boost leaks I did make a plug for the turbo inlet and test it. I'm surprised I was able to make any boost at all! Leaks everywhere! This is my first experience with turbos and diesels and such so it was a bit of a learning curve but I think I'm gaining on it. Wish everything didn't have to rattle itself loose though, lol. Even the dang half moon hold downs that keep the turbo cartridge attached to the exhaust housing were coming loose. I really don't know how this thing even ran. If nothing else I have really enjoyed learning more about these amazing engines and I'm finally getting to where I've rebuilt everything in the truck twice and am finally happy with it. On to the interior...

19 hours ago, AH64ID said:

How is that turbo balanced? As a unit or each individual part?

Ya know, I've heard it both ways. But here's my take...the compressor wheel doesn't even press fit onto the shaft, nor does it have any splines on it. It simply slides on and is held in place by the reverse threaded nut there. In my opinion if the engineers had thought it was that critical to maintain the alignment they would've put some sort of positive retention in there. Just my $.02. Also, I like that it has an odd number of vanes and I believe that helps. If you ever spend a bunch of time just staring at the rims of the cars around you almost all of them have 5 spokes to the wheels. I think this is done to minimize out of balance issues but I could be wrong. Again, all totally just my opinions but I believe the facts speak for themselves.

2 hours ago, Scottfunk said:

If you ever spend a bunch of time just staring at the rims of the cars around you almost all of them have 5 spokes to the wheels. I think this is done to minimize out of balance issues but I could be wrong.

Tire tread is kind of designed that way, none of the knobs are identical but they look the same. Has something to do with harmonics.