GM8 vs Various Turbos

[1999gmc]

That stinks it didn't work out. Mine tows so much better with the ATT, and would never go back. I thought Dennis(Slim Shady) was running 18:1 also? So yours doesn't feel any more responsive with the ATT than the GM 8? Reason I'm asking is I had the GLE tune and ATT on my truck for a couple months and a couple trips towing the toyhauler. Then I wanted to see something and put the stock computer back in. We took a trip and about 30 minutes into it my wife asked if I did something to the truck. I said, what do you mean. She said it just seems to kind of struggle, not as smooth, and is seeming to downshift more. I thought holy crap, she isn't even driving and can tell the truck doesn't run as well. Good luck. Wish it would have worked out. And good luck getting a vendor to refund your money after installing the turbo. It would be interesting to see if the ones on ebay would.

 

[Brooklyn Tow]

Are you saying I'm "heavy"????

NOOOOO, Just can't understand why some experience such a noticable performance increase with the ATT......But your numbers speak for themselves.

 

[Slim Shady]

They can be had on ebay fairly priced. And believe me, there isnt much time involved at all. You can have it bolted on and running same day!

Check out the ebay and other threads on the forum here. Many members are having great luck with these turbos including myslef!

By the way, your not the only one i have heard of having the same poor results with the att.

Jorge nice shot at the ATT, there are a few people that I know running the Hx clone your raving about that also have had issues with it, There will always be differences in the way parts run on any truck. That being said thanks I would like to know who else is having a problem with their turbo. They have my number.

Would your vendor take the turbo back after almost a year and 6000 miles later? I doubt it. I know two people now that had to replace their HX clone turbos from excessive shaft play after only a few thousand miles. The vendor would not do anything for them. At least I could rebuild the turbo for you and make some type of attempt, not so with a non vendor. Probably the reason nobody sells just the turbo they don't want the liability. Yes warranty costs money as well.

My 18 to one truck runs fine with the turbo as do a few others with 18 to one. Dennis test was also done in third gear which I have yet to figure out the benefit or technical reason why. There are anomalies in every thing. Once again thanks for the objectivity.

 

[WarWagon]

It occurred to me that it is always said the ATT is not a stoplight to stoplight turbo. To see that it will hold it's own vs a GM8 on a short 1.1 mile run gives you an idea of how close the trade off for top end vs. bottom end is on shorter runs with a load.

I know the GMx is leaving the line hard and then falling over. The ATT is not leaving the line as hard but is running down the GMx in the upper rpm.

It has a lot of room left in it for steeper grades that are longer. Like on long grades your are floored in the upper RPM just to maintain speed. This is where the cooling fan will stay off longer. It is also where you are in the sweet spot of the ATT.

I have yet to see how the HX40II does in normal driving as the AC is under repair with vintage parts (hoses) taking over 2 weeks to get. I do feel where I run out of turbo with the HX40II in the upper end. It simply doesn't pull as hard to redline as the ATT does. A difference I can feel. I have yet to see if the trade off makes a difference in less demanding around town driving where the 10% grades sneak up on you. I have also yet to test it on the pickup with the 4.10's.

Testing in 3rd gear I would suggest you look at my ATT dyno runs and see that 4th gear sometimes had more power than 3rd on the auto. IMO due to higher load.

Install is a one time event, however, a Kit like the ATT is a cakewalk to install vs. the build and modify your own turbo. Especially when you have to let it sit in mid-project waiting on a part. Again a one time install that isn't as important as the final results.

 

[1999gmc]

It occurred to me that it is always said the ATT is not a stoplight to stoplight turbo. To see that it will hold it's own vs a GM8 on a short 1.1 mile run gives you an idea of how close the trade off for top end vs. bottom end is on shorter runs with a load.

I know the GMx is leaving the line hard and then falling over. The ATT is not leaving the line as hard but is running down the GMx in the upper rpm.

I wonder if something was wrong with my GM8 because my truck pulls harder from idle on up with the ATT over my GM8. It was really noticeable when I put the GM8 back on after having the ATT on for a couple months. I would think I would have low boost or smoke with the GM8 if something was wrong. But maybe not.

 

[JiFaire]

Curious about this, also:

http://www.thetruckstop.us/forum/showthread.php?36278-BD-Quick-Spool-Valve-Install-with-Pics

I love people who innovate and try things.

I love it even more when somebody innovates, and then shares or markets that innovation for the rest of us.

I really love it when those people step up and provide a service for their peers, support their innovation while it grows, and sponsor the community that they built their product in, for the people who tested it out and grew it for them.

I love it a lot less when people think they have to put somebody else down to pull themselves up.

Let's keep this friendly, boys. That's what sets us apart.

 

[DennisG01]

Let's keep this friendly, boys.

Yes! Thank you. I couldn't agree more.

I've said this a few times, but let me reiterate: Dennis ("Slim", not "heavy") has been absolutely fantastic through this process. He was in contact with me throughout and I NEVER felt like I would be stuck. Now, as we are ending this process, he has, indeed, kept his word and is working with me on a return. Although I am disappointed that the turbo didn't work, I have ABSOLUTELY NO COMPLAINTS about him or his customer service. A guy can't ask for anything more than that.

I would add that, if I was simply looking for a replacement for the GM8 (for example, if my GM8 crapped out), I would have no problems using the ATT. It is a fine turbo - it just isn't working for my application.

Oh, something else to help explain why it's not working on my truck... throughout a day of driving, I would occasionally get a P0236 (low boost) code. No big deal, as I can clear it while I'm driving. But, I haven't read about that before with other guys.

 

[great white]

.

Oh, something else to help explain why it's not working on my truck... throughout a day of driving, I would occasionally get a P0236 (low boost) code. No big deal, as I can clear it while I'm driving. But, I haven't read about that before with other guys.

Low boost depends on what your calibration is calling for in the look up tables and what the ATT is putting out.

I believ Kennedy's calibrations take in to account the stock turbo so the tables may be calling for more boost on transient response than the ATT is delivering.

The PCM just sees boost below it's maximum variance (tolerance) from the called for boost and sets the low boost code.

 

[1999gmc]

I got a low boost code with the stock PCM but not with the heath one. I'm thinking you should have tried the KOJO tune before you sent it back. I had a lack of power in OD with the Heath PCM and ATT. I am trying the KOJO one now and it solved my OD problem. So now I have to order my own KOJO tune.

 

[Paveltolz]

When I upgraded my Max E Torque GLE I too got a P0236 code. Hadn't even got two miles down the road. After a couple of hours of checking over the tune line by line and testing over and over to ascertain what was possibly wrong, Bill and I changed the Boost sensor. No code! Might be worth checking out.

 

[Brooklyn Tow]

I got a low boost code with the stock PCM but not with the heath one. I'm thinking you should have tried the KOJO tune before you sent it back. I had a lack of power in OD with the Heath PCM and ATT. I am trying the KOJO one now and it solved my OD problem. So now I have to order my own KOJO tune.

KOJO is tuning OBDII?.......Or is this old news?

I thought he only made OBDI tunes?

 

[1999gmc]

I don't if it was old news or not, but yeah he is tuning OBD II.

 

[DennisG01]

Yes, you guys are right about the low boost thing. I'm not sure why I worded my post that way. We were rushing to get out the door for vacation..... You know how that goes!

So, let me re-explain:

There were absolutely no drivability problems, at any throttle input. The turbo reesponded well, even though the boost was lower than the GM8 at light throttle. I would imagine that I was probably right on the edge (according to JK's programming) of setting the code, or not. I also would hypothesize that if I had a 21:1 it may not have set a code.

Regarding the KOJO tune, I did discuss that with Dennis. But, and maybe I'm wrong, I just can't see it makin a noticeable difference. I already get a light haze under full throttle and we dump more fuel in, wouldn't that haze start to turn black and just waste fuel?

 

[great white]

Yes, you guys are right about the low boost thing. I'm not sure why I worded my post that way. We were rushing to get out the door for vacation..... You know how that goes!

So, let me re-explain:

There were absolutely no drivability problems, at any throttle input. The turbo respond well, even though the boost was lower than the GM8 at light throttle. I would imagine that I was probably right on the edge (according to JK's programming) of setting the code, or not. I also would hypothesize that if I had a 21:1 it may not have set a code.

Regarding the KOJO tune, I did discuss that with Dennis. But, and maybe I'm wrong, I just can't see it makin a noticeable difference. I already get a light haze under full throttle and we dump more fuel in, wouldn't that haze start to turn black and just waste fuel?

Well, yes........and no.

Building a calibration takes into account more than just fuel.

If you just dump in more fuel and leave everything else alone, you'll get more smoke in your case since it sounds like you're just below the "smoke point".

However, timing has a huge effect on everything from smoke to power to egts to turbo transient time.

It's a balancing act.

For example: you may adjust the timing at you current fueling level and find the turbo hits it's minimum boost (for the engine demand) sooner. This allows you to bring in fuel sooner, which increases available drive pressure, which brings the turbo on speed sooner and makes more mass flow, which enables you to adjust timing, which........and on and on.

There's many other things to consider also, like transmission shift points, lockup, line pressures, abuse management, scalers, etc, etc, etc.....all of which can have a visible effect on the turbo response (one of the things we all like to watch).

This is why it costs a fair bit for a custom "tune" in the average Joe's eyes: there's hundreds (sometimes thousands) of hours in development and more money than I care to think about in fuel and hard parts in testing to optimize a system. Even after all that, most guys never even get there...heartbreak, just pure heartbreak (not to mention wallet abuse).

The thing lots of guys seem to forget (or not understand) is that you can't just adjust one variable (in this case, turbocharger) on an engine system and call it a day.

Well, you can, but you're not getting what it's capable of.

You need to adjust all the components of the system to work with each other. That means intake paths, exhaust paths, calibration, gearing, and so on and so on.....changing one factor starts a "domino effect" and halfway through the domino run you may look back to discover something you've done has stood the first domino back up again and brought you right back to the beginning, starting the domino's falling again....sheesh.

In this case, you've changed the nature of the turbocharger and it's interaction with the engine system. In turn, you need to optimize the entire engine system to give the turbo what it needs to give the engine what it needs to give your right foot what it needs to put that big "S-eatin' grin" on your face.

That's what it's all about anyways......isn't it?

 

[1999gmc]

Well, yes........and no.

Building a calibration takes into account more than just fuel.

If you just dump in more fuel and leave everything else alone, you'll get more smoke in your case since it sounds like you're just below the "smoke point".

However, timing has a huge effect on everything from smoke to power to egts to turbo transient time.

It's a balancing act.

For example: you may adjust the timing at you current fueling level and find the turbo hits it's minimum boost (for the engine demand) sooner. This allows you to bring in fuel sooner, which increases available drive pressure, which brings the turbo on speed sooner and makes more mass flow, which enables you to adjust timing, which........and on and on.

There's many other things to consider also, like transmission shift points, lockup, line pressures, abuse management, scalers, etc, etc, etc.....all of which can have a visible effect on the turbo response (one of the things we all like to watch).

This is why it costs a fair bit for a custom "tune" in the average Joe's eyes: there's hundreds (sometimes thousands) of hours in development and more money than I care to think about in fuel and hard parts in testing to optimize a system. Even after all that, most guys never even get there...heartbreak, just pure heartbreak (not to mention wallet abuse).

The thing lots of guys seem to forget (or not understand) is that you can't just adjust one variable (in this case, turbocharger) on an engine system and call it a day.

Well, you can, but you're not getting what it's capable of.

You need to adjust all the components of the system to work with each other. That means intake paths, exhaust paths, calibration, gearing, and so on and so on.....changing one factor starts a "domino effect" and halfway through the domino run you may look back to discover something you've done has stood the first domino back up again and brought you right back to the beginning, starting the domino's falling again....sheesh.

In this case, you've changed the nature of the turbocharger and it's interaction with the engine system. In turn, you need to optimize the entire engine system to give the turbo what it needs to give the engine what it needs to give your right foot what it needs to put that big "S-eatin' grin" on your face.

That's what it's all about anyways......isn't it?

Tuning is definitely a big part. When I went from the stock tune to Heaths with my GM 8 6 years ago, there wasn't much improvement over the stock one. I actually sent it back to them the first time thinking the programming didn't take because I really didn't notice any difference in power. When I got it back the second time it seemed a little better maybe and the shifting was a little different so I just kept it. But now with the ATT going from the Heath to the stock one there is definitely an improvement with Heaths over the stock tune. And then from the Heath tune to KOJO, there is better response than Heaths off the line, but way better in OD with the KOJO one while towing. The Heath tune had to downshift just to barely accelerate while towing our trailer in OD, but the KOJO tune accelerates pretty well towing in OD.

 

[Turbine Doc]

A lot of R&D into the ATT Heath tune, more to come (I hope; because I fear that at some point the quest for more becomes moot for most that are fine with improved vs. maximum performance and Bill will say that is as good as she gets Tim ).

I'm on about tune 8 with my ATT tune from Bill, each time we whittle a little more improvement out of it, since Bill doesn't have a ATT'd OBD-II at his disposal some of what has been done has been done the hard way with back & forth PCMs and trials on my truck and that has been since 2008 so it is/has been a long process us fitting in time & testing between our 2 work/life schedules.

By accident early on I got a stock tune back from him and the ATT ran okay with it, but you definately knew the enhancements for the Heath HP programs that were peaked for the GM-8 were missing, especially in the L-56/S(EGR) program, stock L65/F(non EGR) does better because of the higher fuel delivery program even from GM max fuel 56mm/3 vs. 65mm/3 in the L65.

Often asked will the ATT work with a stock tune, answer is YES, works better with a reflash set for the ATT's operational envelope, same with a tune folks would try from another turbo like HX whatever a tune developed for it will not work exactly for the ATT, running a GM turbo you need a GM tune set for that setup, same for HX to ATT or ATT to HX; just swapping over is not going to be a full performance match to make same-same comparisons on turbo flow requirements, the turbos are different enough to require a specific set of timing-fuel-boost-shift curves matched to the turbo being used and even changes in final gear ratio come into play.

As Dennis found his testing here maybe 18:1 with auto trans is a variable to be considered as well, towing in 3rd vs OD also another variable, hard to nail down all variables unless one has capability to tune, and then dyno or road test under same conditions time after time.

 

[DennisG01]

I'm going to be online very sporadically over the next week and half as I won't always have access to the internet (or decent cell coverage) up here on the coast of Maine. So, please don't take offense if I don't respond to something right away.

As far as tuning goes (and thanks for the insight and clarification of tuning), I'll first say that I won't pretend to understand all the intricacies of making a good tune and what goes into that. But, what I do know is that the guys who do it spend a lot of time and money in perfecting it. It certainly isn't something where one can "wing it" - it takes a big commitment on their part to do it right.

I also won't deny that an ATT-specific tune will work better. I'm just not convinced that it is going to make a BIG difference. I know I'm just shooting from the hip on this and I have no way of truly quantifying this, but I can only guess that differences I would see be limited to a very small percentage. Along the same lines, there's many guys out there who switched to an ATT with just the stock programming and ARE seeing a noticeable difference. Don't get me wrong - I'd LOVE to be one of those guys who is seeing a big difference. It just doesn't seem to be working for my setup.

As far as the 3rd gear thing (and there was more talk about this on another site), I do that because that's what Bill Heath recommended to me a number of years back. But, what I do know, is that with the weight I'm pulling over the course of the hill pull, I never get enough speed going to where the ECM would call for an upshift, even if I did start in 4th (OD). Unless there's some special programming that is going on (I think not?) by having it in 3rd, it might be a moot point.

 

[DennisG01]

... To add to the above...

For reference, when I manually select 3rd gear, the TC still locks up.

 

[bgiovan]

Absolutely love my ATT & KOJO tow tune (yes a ODBII tune)! Pulling a 10,000lb 30' Keystone Travel Trailer and it is night and damn day from the GM8 stock I had. No brick behind the 'Burb is even more fun. The power band really is most impressive, at least for my rig, when I nail it at 40MPH. I'm at 90 before I know it. A little black smoke of course upon mashing the pedal but the boost is impressive. Highest boost so far at WOT is 14psi and recently just started throwing a little more black smoke than usual. Once again, just at pedal mash - it clears quickly. Still some tweaks but love it. EGTs are high and am looking at an intercooler as my next project. Slim has been wonderful to deal with - I had a shop do the install for me and he took the time to talk with them multiple times during the process and we've talked several times also. Been a great experience so far and am looking forward to learning more from you guys.

 

[NVW]

Absolutely love my ATT & KOJO tow tune (yes a ODBII tune)! Pulling a 10,000lb 30' Keystone Travel Trailer and it is night and damn day from the GM8 stock I had. No brick behind the 'Burb is even more fun. The power band really is most impressive, at least for my rig, when I nail it at 40MPH. I'm at 90 before I know it. A little black smoke of course upon mashing the pedal but the boost is impressive. Highest boost so far at WOT is 14psi and recently just started throwing a little more black smoke than usual. Once again, just at pedal mash - it clears quickly. Still some tweaks but love it. EGTs are high and am looking at an intercooler as my next project. Slim has been wonderful to deal with - I had a shop do the install for me and he took the time to talk with them multiple times during the process and we've talked several times also. Been a great experience so far and am looking forward to learning more from you guys.

Make sure your turbo to intake clamps are tight, a slight leak can drop boost and give more black smoke.
With the high EGT's, is that in OD or drive, dropping to drive helps a lot.