A-Team Turbo VS CKO-40(hx-40 knock-off)

[turbonator]

So If I use a smaller turbo that chokes at 14 PSI about the time the starter disengages then I should be happy with only 14 PSI? I am here to tell you I HATE the GM3’s 14 PSI hard limit vs. an ATT 14 PSI. Let’s compare the exhaust back pressure for an ATT at 14 PSI to a GM4 like Buddy did and I reposted here with permission.

http://www.thetruckstop.us/forum/showthread.php?33098-Info-on-why-you-would-want-an-A-Team-Turbo

The A Team Turbo generates 14 PSI of boost (16.8psi exhaust) with less back pressure than a GM3 (19.6psi exhaust)

The hard limit of a GM3 before it generates more heat than boost is around 14 PSI. More fuel just turns to smoke and most people start to squirm with the EGT’s seen. After all the EGT gauge goes to 1600…

So at 2200 RPM the GM3 turbo is simply done and the engine feels like a boat anchor above 2200 RPM. With the ATT and the lower boost, 13 PSI, due to B99 fuel I am running the engine can breathe above 2200 RPM and will pull till redline. I have had the ATT at 18 PSI and pulling strong on #2 diesel. So the ATT has potential for more boost, however, even when not used it is still allowing more power than a GMx due to less backpressure, etc.

Engine RPM vs. boost is a major change with small vs. large turbo’s. The engine with no throttle will generate 6 PSI of boost on a GM3 at 2000 RPM – in effect a turbo exhaust brake. 6-14 PSI and popping the wastegate open doesn’t take much throttle at all! The GM3 is boosting from idle till it chokes at 2200 RPM. The ATT starts boosting around 1700 RPM with the tach moving up fast from there. The boost will drop to near zero if you take your foot off the throttle.

This is why 14 PSI is just a single number when MPG, HP, ECT, EGT, MPH are also important and to some MPH and MPG are a lot more important than what # the boost is at.

What exactly is the point of asking the difference between the ATT and the Mitsubishi turbo that was the basis for the design? Dennis is not selling a Mitsubishi turbo! Rather a knock off or whatever you want to call it with changes specific to work on our 6.5. This knock off is up to Dennis to control the quality of and is what a lot of testing was done on. This is the turbo that anyone can buy and what we should be concerned about. Differences between them, if any, are not relevant for the ATT vs. GM3 vs. Holset. Quality and consistency of the ATT turbo is relevant vs. quality/performance many knock offs of a Holset or GM8.

I have pushed the ATT to 1550 EGT sustained while tuning and only burned the turbo blanket some. We changed the tune, however. I still have a running engine making EGT only one of many factors that can predict an engine meltdown. Different timing with lower EGT may be an issue. We were doing 55MPH with the ATT when we hit EGT’s that high. With a tune change due to the 6.2 precups we were able to still do 55 MPH but with lower EGT’s. The GM3 going that hot was at ~40MPH. I noticed the GM3 did discolor the paint on the floorboard where the downpipe goes past.

IMO when I cranked up the fuel and stomped it from a stop I could smoke a GM3 for about 3 parking spaces. With the ATT I could smoke it for 6 Parking spaces. Keeping the RPM a little higher for the bigger turbo is about the only downside some may need to get used to. Searching for another turbo to be in the middle is starting over and not a kit. So quality of the sourced turbo will need to be refined and getting all the right parts in one place at the same time… Well lack of proper parts in the same place is why the Holset wasn’t tested by us over Thanksgiving.

It would be interesting to get an answer to the question of how it stacks up.

dennis mentioned that he had the turbine wheel modified, i was just curious what the change was, i did not ask the differences between the mitsu and the knock off.... if there was changes made, i would like to see the before and after... pretty simple.

we run an H1C, which spools up 500rpms sooner than the A-team does with 1:1.2 drive pressure ratio, and low egts with a fully cranked db-2... i agree that the gm-x turbos are junk, and would never go back....

 

[WarWagon]

dennis mentioned that he had the turbine wheel modified, i was just curious what the change was, i did not ask the differences between the mitsu and the knock off.... if there was changes made, i would like to see the before and after... pretty simple.

we run an H1C, which spools up 500rpms sooner than the A-team does with 1:1.2 drive pressure ratio, and low egts with a fully cranked db-2... i agree that the gm-x turbos are junk, and would never go back....

Now we are getting somewhere. Assuming spools at 1200 RPM? How is the boost when you get completely off the throttle at 2000 RPM? Is there a RPM ceiling you reach with it where the engine falls over? (Like the GMx is what I am thinking.) The data on other turbo's is scarce in reference to running em on a IDI engine vs. the DI they came from.

My high EGT's are from small precups in the 1995 w/ 6.2. The DB2 on the 1993 has gotten lower EGT's with the ATT even after being cranked up more and in more places than the GM3 could handle. I can crank it some more, but, the EGTs are below 1100 now and below 800 on the B99. I'll double check the filters etc. just in case they are causing trouble again.

Several posts mention questions about the differences between the ATT and the Mitsu so the above was an observation to it's relevancy and as you pointed out a curiosity.

 

[turbonator]

Now we are getting somewhere. Assuming spools at 1200 RPM? How is the boost when you get completely off the throttle at 2000 RPM? Is there a RPM ceiling you reach with it where the engine falls over? (Like the GMx is what I am thinking.) The data on other turbo's is scarce in reference to running em on a IDI engine vs. the DI they came from.

My high EGT's are from small precups in the 1995 w/ 6.2. The DB2 on the 1993 has gotten lower EGT's with the ATT even after being cranked up more and in more places than the GM3 could handle. I can crank it some more, but, the EGTs are below 1100 now and below 800 on the B99. I'll double check the filters etc. just in case they are causing trouble again.

Several posts mention questions about the differences between the ATT and the Mitsu so the above was an observation to it's relevancy and as you pointed out a curiosity.

when running on the highway at 90km/hr, we see around 1.5-2psi boost,400-500*egts and not enough drive pressure to measure on a mech. gauge,when we put the foot into it we spike up to 15 psi at WOT, with 1000*egts and 16.5psi drive pressure... so we need to find more fuel ....all of that data collection is pulling 10,000lbs. ....... and we are running the same pre-cups as you non turbo 6.2l na.... one thing we found with those cups, when we took the heads off to inspect our rattle can ceramic coating on the pistons, and durability of the cometic MLS head gaskets, we found that the cups were very cracked, in some cases out past the fire rings... that was when we were running the 351vgt past 25psi, we think it was a pressure thing, as we never seen egts past 1000 with it, and we put 5000 miles on the motor before the inspection...

 

[racedaymechanic]

Doing some mock up stuff now should be up and running by the weekend, Here is the setup I made for the oil return to the engine

Airbox and Turbo

another angle