GM8 vs Various Turbos

[DennisG01]

So, for a while now I've been tracking some numbers with various turbos. Although there's a couple other "tests" I've done, the main one I've been concerned with is a hill "climb", so to say. Akin to the "diesel Page" pull-offs.

Let me start by describing my method. I've tried to keep things as much "apples to apples" and unbiased (ie, no "seat of the pants" comments) as possible. The weight behind the truck is always my boat - a 28' cruiser that weighs just a few pounds under 10K - for all practical purposes it weighs 10,000lbs. While we tow this boat everywhere from the Chesapeake Bay in MD to the coast of Maine, we also take it to local lakes, here in PA. On the way to one of the lakes is a nice highway that happens to have a good hill, approximately 1.1 miles long (from the place where I pull over to a pole at the top of the hill). I start in the same place (from a standstill) every time and go flat out the whole way up, with the gear selector in 3rd.

If you take notice, the 2nd and 3rd lines are with an ATT turbo - but I was one of the ones that received the wrong sized turbine housing - hence the high EGT's. As seen in other threads on The Truck Stop, Dennis (Slim Shady) is on top of this and I will re-do the test once I get the correct housing.

The "Mitsubishi" turbo is courtesy of Turbine Doc - thanks Tim!!! Generally speaking, though, you can see the numbers are relatively similar (except, of course for the EGT's with the wrong sized ATT). I'm excited to try out the new (correct) ATT and hoping that will provide some noticeable improvement over what I've seen so far. One thing to keep in mind is that I have an 18:1 engine, so my results may be different than those of you with 21:1's.

As a side note, I also want to say that Dennis (Slim Shady on The Truck Stop) has been absolutely fantastic to deal with. He never once led me to believe that I would be "stuck" with that wrong-sized ATT. I know he received some flak (unjustified, in my opinion) a while back, but I have talked/emailed/texted with him more times than I can remember (including before, during and after all that trash talk took place). Many times, it was he who initiated a new conversation to find out how things were going. No question about it - he's a stand-up guy.

I'll know more once I get the new turbine housing, but it seems like the ATT turbo is, at a bare minimum, a good replacement for an GM8. Even with the too-big housing, it wasn't too far off from the GM8 and it costs less than a new GM8, as well. As a side note, people with a 21:1 seem to report even better results.

http://www.thedieselpageforums.com/photopost/data/500/medium/1_1_Mile_Hill_s_Winter_2011.jpg
http://www.thedieselpageforums.com/photopost/data/519/medium/1_1_Mile_Hill_s_Winter_2011.jpg

[More Power]

Thanks for posting. Real life tests are the best way to see what's happening. Where is your pyrometer probe located? Before/after the turbo, in the manifold, in the crossover pipe, or in the turbo downpipe?

Jim

[DennisG01]

Yeah, I figured this would be something interesting to look at/discuss - especially for anyone considering replacing their turbo. I'm looking forward to getting that new turbine housing to see what it does!

My pyro probe is in the manifold - directly under the turbo - I tapped it into that "square boss" that is on the outboard side of the manifold.

[john8662]

so far the ATT looks like a dog, no improvement over the GM8.

[Kennedy]

Wow I hadn't heard from you so I just assumed you had things finalized already. What's it been about 6 months now?

[DennisG01]

so far the ATT looks like a dog, no improvement over the GM8.

No improvement the way it is - but hoping the new turbine will change that. From what I've read on TTS, though, it seems the guys with a 21:1 are having better results - but again, I've got the wrong housing. In the interest of fairness, I wanted to post everything I've got, though. I want this to be as unbiased as possible.

[DennisG01]

Wow I hadn't heard from you so I just assumed you had things finalized already. What's it been about 6 months now?

Yes, taking longer than expected. Taking longer than Dennis (ATT guy... not me) expected, too. I think it was sometime in Dec when everything got figured out regarding the larger housing. He's been in contact with me (not leaving me hanging) and I never told him I was worried about a time frame.

But, once things were figured out on his end, at that point, he had to first convince the factory that a mistake was made and then go about getting them to re-tool and re-produce.

[sctrailrider]

What size housing did it come with and what size are you going to try next..

[DennisG01]

I don't know how to measure it. The only thing I know is that he told me that the factory messed up and it was made out of spec. The new one will be smaller - but as far as specs go, I don't know.

[JorgeNY6.5]

I dont see why ppl waste there time with these non gated turbos. A member over at TTS got the "wrong size turbo" and his truck would blow a butt load of soot, waste in my eyes. So basically your truck is not running top notch and you have no idea when he will make it right?

[rustyk]

With the right IP, injectors, CR, and timing, the right non-wastegated turbo is fine. My AMG (Peninsular Engines) long block came with my choice - non-wastegated.

It smokes black only when accelerating cold. 100' up the driveway, it runs clean. When it smokes slightly when warmed up, I know its overdue for an air filter change.

[DennisG01]

I dont see why ppl waste there time with these non gated turbos. A member over at TTS got the "wrong size turbo" and his truck would blow a butt load of soot, waste in my eyes. So basically your truck is not running top notch and you have no idea when he will make it right?

If you look at the numbers, the truck is running about the same as the GM8, just the EGT's are a little higher due to the sizing. From a "seat of the pants" feel, it doesn't require as much throttle for the rolling hills - seems to straighten them out a bit.

I was one of the ones with the wrong size housing, but I believe there are actually somewhere over 100 people that are satisfied with their ATT. Based on their reviews, it appears the ATT offers an improvement over the GM8.

I've never rushed him to "get this done". I honestly believe he's a good guy and I have no doubt he will take care of me. I'm not making excuses for him, but he has a very demanding full-time job and this is a part-time gig for him.

[DennisG01]

Stay tuned - just heard from Dennis and the new turbine housing will be on it's way to me very soon!

[greatwhite]

Subscribed for the final outcome.

I've actually believed the GM8 isn't that bad of a unit overall for a while now and guys tend to gripe about it too much sometimes.

Mine did fine helping to tow my 8500lb TT:

http://i40.photobucket.com/albums/e235/gr8twhite/1237d529-1.jpg

across the continent:

http://i40.photobucket.com/albums/e235/gr8twhite/Maps/comx-gander-1-1.jpg

with only the help of a diamond eye exhaust, a turbo master and a Heath PCM......at around 60 mph (passes were down to around 50-55 unless traffic was slower, which it usually was) and not one complaint. Lookout pass was a butt-kicker, but everyone was slower than me, so no worries. CGVWR was probably somewhere around 16-17,000 lbs all loaded up.

Well, not from the turbo that is. I popped a piston crown in Washington state and that's how I ended up with a new GEP Optimizer 6500 under the hood.

My wallet still hurts.......:(

[Robyn]

The exhaust housing on the GM Huffer is one of the biggest troubles with the final outcome.

The underhood layout just makes the available room far too cramped to really do a smash bang up job on outlet flow.

Drive side pressure tends to be a little too high and results in the EGT's staying up too.

One local fellow has the turbo off of a Power stroke on his 6.5
I have no real info on this swap, but I see the rig from time to time.

Not sure if this is a good thing or not.

Hope this all comes out good for ya.
Do keep us posted

Missy

[DennisG01]

GW - are you retired? That's one heck of a trip!!!

I just put the new turbine housing on tonight. I'll drive it around this week and feel it out. Then do a few 0-60's. I'll take notes on PSI at various MPH/Percent Load, as well, to compare to my notes with the other turbos. The boat is still under wraps, but should be coming out of hibernation within the next few weeks. Then I can do the real-deal testing while towing.

[greatwhite]

GW - are you retired? That's one heck of a trip!!!

Nope. I'm military, Search and Rescue.

http://i40.photobucket.com/albums/e235/gr8twhite/Me/DSCN3598.jpg

I was transferred from west coast to east and had to move.

We were trying to make a nice trip of it, and then the engine calved on the second day.

That was pretty much the end of the "nice trip" and it became a flat out sprint to get to my next post on time.

Had lots of time to see Ellensburg Wa though...:rolleyes:

[DennisG01]

Nice bird!

Ellensburg... for the history, right? ;)

[greatwhite]

Nice bird!

Ellensburg... for the history, right? ;)

Yup.

:rolleyes:

[racedaymechanic]

I think that the HX40II is a great improvement over any of the GM turbos, EGTs drop 200+ degrees spools fast and makes great power, I have put about 6k miles on the one I have and alot of that was towing my 5th wheel She pulled right up Fancy Gap passing semi's and other RVs going up, egts never got above 1100 and I keep the boost under 18#, There are at least a dozen that I have sold Downpipes to and have yet to hear of any problems

[DennisG01]

I've read about that one, too. But, the problem is that I don't have one to try out (got an extra one?;)). And the only way to do a factual comparison is to do it on the same truck with the same load behind it. I'll have the "correct housing" ATT ready to go in a very short time. It's on the truck, but I had a different problem with the truck that is almost fixed. I might have a line on another, different, turbo - but I gotta keep that one under wraps for now.

[sctrailrider]

My build is still going a little slow, I have posted some pics in my album " My 6.5 towing build" getting ready to start my thread a little later. For now, I plan to use a Holset Pro HX40, I bought it with a 18^2 turbine knowing that housing was too big. Another member here has said he would do a mod to my turbo for some cost for his R&R on this turbo which is great, (I don't know what will be done and don't care as long as it works), I can say that I haven't gotten a reply to my emails in a while from him, i know this may be low on his list right now, and I am not yet ready for the turbo anyway.

With that said, if this mod with RJ doesn't go through, I was thinking about going to a machined HX35 14cm Gated turbine housing behind the Pro 40 compressor ??

The new build is for towing only with Kennedy 18:1 pistons and John (Unique Diesel) will be building my DB2833 pump, so I think I will be able to supply enough fuel. I am building for the 2000-3000 rpm range.

Any thoughts from anyone, I haven't seen anyone but RJ use this turbo and get it to work and that was in the pull off's.

[JeepSJ]

Which Mitsu turbo did you use? I've got the TE06H and I'm not really impressed with it. I've been considering a HX35 due to the nice selection of housings and wheels. Unfortunately I've got a crap 4911 and I may just sell off the Jeep because I just don't have the time to play with it.

[DennisG01]

Which Mitsu turbo did you use? I've got the TE06H and I'm not really impressed with it. I've been considering a HX35 due to the nice selection of housings and wheels. Unfortunately I've got a crap 4911 and I may just sell off the Jeep because I just don't have the time to play with it.

I honestly don't know. I sent a PM to Tim to see if he can shed some light.

[greatwhite]

The turbo available from a certain retailer is a mitsu TD07-22A, with a few tweaks IIRC.

Tim helped to trial/develop it, so he would know for sure...

[DennisG01]

UPDATE UPDATE UPDATE

FINALLY, got the boat out. It's been a busy Spring/Summer so far and haven't really had the time to do much boating. So, the other day I did another hill pull with the proper sized ATT turbine housing. Results were slightly better than the wrong-sized housing, but still extremely comparable to the GM8. So, for now, the GM8 is back on until I find something else.

Here is what the hill pull with the proper ATT yielded:

Ambient: 83*
Max Boost: 15.5 PSI
Max Speed: 67 MPH
Max EGT: 1150
Elapsed Time: 75 seconds

Everything was done exactly as I always do so the only variable is ambient temp and the turbo.

[greatwhite]

UPDATE UPDATE UPDATE

FINALLY, got the boat out. It's been a busy Spring/Summer so far and haven't really had the time to do much boating. So, the other day I did another hill pull with the proper sized ATT turbine housing. Results were slightly better than the wrong-sized housing, but still extremely comparable to the GM8. So, for now, the GM8 is back on until I find something else.

Here is what the hill pull with the proper ATT yielded:

Ambient: 83*
Max Boost: 15.5 PSI
Max Speed: 67 MPH
Max EGT: 1150
Elapsed Time: 75 seconds

Everything was done exactly as I always do so the only variable is ambient temp and the turbo.

That is very interesting.

Looks like the "smaller" housing jumped EGT's up to near GM8 comparable levels even with the jump in ambients considered.

I've been able to pull comparable hp and tq using a GM8 to what the current claim is for the ATT (dyno sheet has been posted elsewhere). Numbers are in my sig, but those were a dyno specific calibration we made up while it was on the rollers and I wouldn't run it on the street. Too much advance for my comfort, among other things....

I flash my own PCM and can "tweak" whatever I want with the software/hardware at my disposal. No, it wasn't cheap.

If I had it to do again, I probably would have just done a 12V swap and be done with it.

I may be entering into a project to see what I can pull out of an ATT (my truck is a 20.2:1), but lots of stuff has to line up before we go down that road....

[DennisG01]

That is very interesting.

Looks like the "smaller" housing jumped EGT's up to near GM8 comparable levels even with the jump in ambients considered.


The "smaller" ATT did indeed compare pretty evenly with the GM8, but the 4th line in my table is the Mitsu turbo (from Tim), not the large housing. The smaller housing actually lowered the EGT's as compared to the larger housing.

[Slim shady]

The turbo was returned and after all the time and a little less than 6000 miles the purchaser was refunded his money for not being satisfied. I am sure most vendors would have bought back a 6000 mile turbo and refund the customer their money after using the turbo for almost 7 months. After all that is the right thing to do if the customer is not happy (right?)

Just for the record the turbo works fine on a number of trucks with the 18:1 configuration stick and Automatic. And for the turbo being comparably larger than the GM eight with considerably less back pressure on the exhaust, having the same times and egts as the gm eight is not that bad. I also have a customer with 2 trucks both having vendor specific tunes similar to Dennis truck and he has no problem with his trucks and the turbo. Not sure what happened here, waiting to hear about Dennis's next turbo?

Would someone be able to tell me the technical reason for the test being conducted in third gear and not a run through all of the gears? Like starting in drive, not third.

[DmaxMaverick]

The turbo was returned and after all the time and a little less than 6000 miles the purchaser was refunded his money for not being satisfied. I am sure most vendors would have bought back a 6000 mile turbo and refund the customer their money after using the turbo for almost 7 months. After all that is the right thing to do if the customer is not happy (right?)

Just for the record the turbo works fine on a number of trucks with the 18:1 configuration stick and Automatic. And for the turbo being comparably larger than the GM eight with considerably less back pressure on the exhaust, having the same times and egts as the gm eight is not that bad. I also have a customer with 2 trucks both having vendor specific tunes similar to Dennis truck and he has no problem with his trucks and the turbo. Not sure what happened here, waiting to hear about Dennis's next turbo?

Would someone be able to tell me the technical reason for the test being conducted in third gear and not a run through all of the gears? Like starting in drive, not third.

3rd gear (w/converter locked) on a 4L80 is direct (1:1 gear ratio). No gear compounding, other than the primary running gear. The formula used to calculate the output values rely on this. The gear selection may be different, depending on which gear is actually "direct", on other vehicles/transmissions.

[greatwhite]

That raises an interesting discussion point:

In my stock 1998 L65 calibration, TCC is disabled in direct 3rd and 4th.

There is an option to enable TCC in 3D and 4D, but you need to alter the calibration as delivered from the OEM.

That's the cal I got off TIS2web (well, through a vendor) so I'm reasonably sure the most current one.

Can't say about other years, just the one I have in front of me on the screen.

I do find it odd that the cal would be like this as I'm pretty sure I remember it differently from when I last read the 4L80e component book. IE: compression braking and lockup in direct.

But the gray matter is getting older and I might not remember that exactly right. Need to do some "refreshing" it seems....

Regardless, one would think that if the turbo was the deciding factor there would be differences in the testing points (in this case egt, mph and time to mph) if all the other variables are kept the same (ie: gear selection, rpm, tow weight, grade, ambient, tps %, etc).

Very curious indeed......

[More Power]

The GM-8 is really a great turbo for 95% of the 6.5 owners out there, 95% of the time. Where it falls down is when you ask the truck to pull heavy, especially at higher engine speeds (like 2nd gear WFO on a long steep grade). Turbine drive pressures rise rapidly at higher engine speeds and the compressor has a fairly small efficiency island, which puts it into a low engine speed and boost realm. Ask for more boost and flow, and the IAT goes too high.

A GM-8 on an 18:1 engine that is asked to deliver ~15-psi, especially at higher engine speeds, is being pushed well outside of its comfort/efficiency zone.

The key is finding a turbocharger that is capable of remaining reasonably efficient (IAT/Drive pressure) when running the engine at higher rpms and asking 15+ psi boost pressure from it. All this assumes the system is running with an intercooler. An efficient turbo that allows the engine to run at higher engine speeds without excessive drive pressures or IAT is what we need.

There are variations of the Holset HX35 on the market that were produced for a variety of applications. When I reference it, I am specifically discussing the stock version removed from (designed for) a Dodge/Cummins truck. I have a number of first-hand reports of HX35 turbo installations on 6.5s. All those report a big performance gain and lower EGTs when compared to the GM turbo. In fact, I'll have a new story about a 1998 6.5TD K3500 dually that runs at a GCVW of 26,000-lbs. According to the owner, the Holset/Intercooler made the single most significant improvement in performance, considering all of the typical power mods we all know about.

[DennisG01]

I should add something in regards to my "3rd gear" selection.

First, I've done this simply from a recommendation by Bill Heath to me many, many years ago. Second, unless there's some type of special ECM programming going on when one selects 3rd gear, this may all be for nothing. The reason I say this is that even I did the test in 4th (OD), at the final speed I've been able to attain, I wouldn't be going fast enough to where the ECM would command an upshift, anyways. So, even if I started in 4th, I would still be in 3rd at the end of the test.

Also, as a side note, I may not be logging in much over the next week and half - we're on vacation about half-way up the coast of Maine and cell coverage (and my access to wi-fi) is extremely weak.

[greatwhite]

When you select 3 direct, you move a spool valve inside the housing.

It also disables the torque converter lockup in the program. At least, as I mentioned, it does in the l65 program I'm looking at.

How does this effect the test results?

Meh, doesn't matter as this is a comparison between the gm8 and the ATT. Deposing each to the same variables is essential in an apples to apples comparison.

Now, that doesn't mean that one or the other will return better results if parameters are changed.

Ie: current test points may favor the gm8, yet up the rpms above 2600 and the ATT may show better performance....

[DennisG01]

It also disables the torque converter lockup in the program. At least, as I mentioned, it does in the l65 program I'm looking at.


Sorry, I did read your comment about the lockup and I forgot to address that. My TC still locks up if I manually select 3rd gear.

[greatwhite]

Sorry, I did read your comment about the lockup and I forgot to address that. My TC still locks up if I manually select 3rd gear.

Interesting.

Could be a difference in the Kennedy calibration.

Dunno, only one man can really answer that.....:rolleyes:

[JeepSJ]

There are variations of the Holset HX35 on the market that were produced for a variety of applications. When I reference it, I am specifically discussing the stock version removed from (designed for) a Dodge/Cummins truck. I have a number of first-hand reports of HX35 turbo installations on 6.5s. All those report a big performance gain and lower EGTs when compared to the GM turbo. In fact, I'll have a new story about a 1998 6.5TD K3500 dually that runs at a GCVW of 26,000-lbs. According to the owner, the Holset/Intercooler made the single most significant improvement in performance, considering all of the typical power mods we all know about.

Well, I guess I'll get to test that. I've decided to get back into the Jeep project and get her running again. I've got too much time invested to just let it go. Pump should be out this weekend and off to the rebuilder.

I thought that a smaller housing would be good on the HX35. Then again, I haven't taken the time to really calculate anything. Local diesel/turbo shop swears by the GM-8 for the 6.5 so he isn't being much help. So you are thinking a HX35 just as it sits on a 5.9 is the way to go?

On a side note, know anyone that wants a good used MHI TE06H?

[phantom309]

K, i,m just a little confused,.
3D? would mean third gear direct? (converter locked)
4D? would mean,......???? as 4th is OD,.

mine locks the converter in 3rd gear at 88kph, at anything less than 90% tps,.
locks same spot in OD at less than 65% tps.
I have 265's and 3:42's so i don't mind the gm4 as the rpm is usually always under 2k,.

Nick

[sctrailrider]

I know this thread is a little old but I am going to bring it back ...

Dennis, have you been able to test the "powertrain" turbo from Ron Schoolcraft as compared to the others?

What did you end up leaving on your motor?

[DennisG01]

I'm still working on some things, Chris. Unfortunately I'm in a bit of a holding patter right now as the thing I use to do my towing tests is my boat. Currently it is shrink wrapped for the winter. I don't think it would be a true "apples to apples" test if did a towing run with it, since it usually just has the cockpit cover on.

I am able to do 0-60 runs, but I don't want to publish anything since this is not done at a track (just done on a relatively flat road that goes between a corn field) so we really couldn't compare one vehicle to another. I do use a ScanGaugeII for these runs, so at least that takes "me" out of the equation (ie: the "variable" of me pushing a start/stop button on a stopwatch).

[More Power]

A long-time member and friend of the Page, who is a fabricator/welder/machinist, will soon be offering a slick bolt-on downpipe adapter for the HX35. I should have an early example to photograph and discuss before long. We'll get a documented story soon afterward that compares the GM8 to the 35 in a variety of operating environments.

His first prototype has been in service for many months, which replaced a GM turbo. He's also working with the HX40, so that might become an option as well. :)

Jim

[JorgeNY6.5]

Yep, got my kit last year


A long-time member and friend of the Page, who is a fabricator/welder/machinist, will soon be offering a slick bolt-on downpipe adapter for the HX35. I should have an early example to photograph and discuss before long. We'll get a documented story soon afterward that compares the GM8 to the 35 in a variety of operating environments.

His first prototype has been in service for many months, which replaced a GM turbo. He's also working with the HX40, so that might become an option as well. :)

Jim

[sctrailrider]

It would be good to see the "Powertrain" turbo tested also in the mix. Maybe Ronniejoe will see this don't know. I have one and love it altho I did make some minor changes to it to better suit my DB2, but it is a really good setup from the start as it came..

[JetBoater]

I would consider installing an HX35 if the adapter kit was made available...the turbos can be purchased for a reasonable price.