ATT run vs. HX40II

[WarWagon]

Statistically the power output on the 1986 6.2 Military engine is the same for both turbo's. There is bragging rights if I was selling an air filter. Except one turbo wins torque while the other wins HP. Yet, the numbers are so close - less than 5% there isn't a clear power winner IMO. Driving it the SOTP feels the same.

In summery it looks like the HX40II has 7-16 HP more but 20 FT LBS less than the ATT. I would call this the ATT giving a genuine ass kicking to the HX40II. You see I was running 23 LBS of boost (Bout as much as you would want to run without an intercooler.) with HX40II and only 14 LBS of boost with the ATT! We know the ATT can get 17 PSI on this engine, but, these rollers have trouble winding it up. Regardless the ATT is not working the engine as hard with lower backpressure and boost numbers to get near the same power. So less boost by 50% and nearly the same power. MPG because of this change I will post up when I have a tank or two measured.

For reference my 1993 runs around 18 LBS of boost after spooled up with a sustained load.

Temp was the same today 72 degree vs 66 degrees last time with the HX40II (the HX40II dyno run) and if anything slightly damper.

I tried several tunes including a very dirty one I didn't run on the HX40II. No real difference from the tunes.

Again this engine has precups limiting what I can do.

The run files are available if anyone wants to go over them.

Shown are the ATT runs with the last two runs the best HX40II runs. See how the HX40II is on top for HP, but, on the bottom for Torque? :skep: Other than 50% less boost used it is really a draw. The peaks are shifts and are ignored.





This is specific to the unique 6.2 setup I have. The 1993 with 6.5 NA heads is a different animal. Your rig with turbo precups will also be different. So this isn't the ultimate last word. It is just a point in time with a specific build and close weather conditions. :thumbsup:

 

[Big T]

Good stuff.

I've seen 17 psi on my ATT, but that was while towing a bass boat up HWY 330 to Big Bear, CA. It was also during the steepest sustained section. Otherwise, the most I see is typically 14, maybe 15 psi. I would be curious what specs I could produce on the dyno, or maybe the experts here could fathom a guess?

 

[JiFaire]

Good test, WW ... gotta love it when somebody brings data to the table! We've heard a bunch of guys talk about how the ATT pulls, and how it gets better mileage, now we can see why.

I'd love to see data on another vehicle, with different engine/gearing/precup configuration. Anybody else thinking of duplicating this?

 

[Paveltolz]

Eventually, I'll work a few turbo's through the system starting with the GM-8 and the ATT if I can get it back from across the lake. HX40 may be in the works if the job holds out and then there's a couple of projects being R&D'd by others I'd like to run as well.

 

[Twisted Steel Performance]

Good work WW.... if it wasn't so much of a hassle to change the cups it would be interesting to see what difference larger cups made to the mix.....

 

[6.5L]

There is a lot of information out there between the stock GM turbo's and the ATT that I have done comparing numbers and mileage

 

[Paveltolz]

There is a lot of information out there between the stock GM turbo's and the ATT that I have done comparing numbers and mileage

And good information at that. My efforts are to see where the old motor compares with the new motor running the same GM and ATT then work in other turbos as time, desire and $$ permits.

Here's to discovery and the 'ever learning and never able to come to a complete knowledge of ____________ (insert hobby here).'

 

[THEFERMANATOR]

Judging from the lower boost of the ATT during the dyno run, I would be curious to see what the results would be on a dyno that could actually load it down. I know spooling non wastegated turbos on a dyno has always been a challenge.

 

[tanman_2006]

x2, once again I feel the dyno doesnt tell the whole story. I'm surprised the HX didnt have the higher torque given the extra boost down low. I also figure the ATT would be better up top in HP but the dyno couldnt load it. Then add in the Precups, too many variables but atleast the variables were constant.

 

[Big T]

Joshua, how far apart time wise were these two Dyno runs? How long did it take to change from one turbo to the other?

 

[DieselSlug]

After replacing the center section of my WH1C i could have now afforded to buy an ATT. Always how it works..

 

[WarWagon]

Joshua, how far apart time wise were these two Dyno runs? How long did it take to change from one turbo to the other?

Runs on 2-23-13 and 3-9-13. Took an afternoon to swap the turbo's, intakes, and including tapping a new port for the boost gauge.

Loaded or not for the ATT the baseline for it shows it on par with the HX40II at lower boost levels. This should show you a single factor like a boost number doesn't guarantee results. Especially if the drive pressure or other factors neutralize the benefit of higher boost.

Again the precups are a serious limiting factor on my engine. The tune steps around this with reducing/eliminating smoke and the goal. These precups smoke bad vs. my 1993 if not fueled and timed carefully.

 

[Jorge6.5]

Thanks for going through all the time and work to share. Do you monitor drive pressure? If not, maybe in the future?

 

[1999gmc]

That's what I tried telling them over at dieselplace. That my truck with the ATT pulled harder with 0-2 psi than my GM 8 did at 4-8 psi. They just kept arguing it's 4.10 to 3.42 gears and yada yada yada BS.

 

[Turbine Doc]

That's what I tried telling them over at dieselplace. That my truck with the ATT pulled harder with 0-2 psi than my GM 8 did at 4-8 psi. They just kept arguing it's 4.10 to 3.42 gears and yada yada yada BS.

They are wrong and you are right I've got 3:42s in my burb and my results with the "bad gears" for ATT mirror yours, the unbiased tester there.......not so much

 

[6.5L]

Lower spooling with the hx I don't think would yield higher torque. When I put the quick spool valve on my ATT, I made torque a little sooner but it actually made 10ft lbs less. If I recall correctly, peak torque wasn't achieved until 3000 rpm or so anyways. At least with mine.

 

[Big T]

Lower spooling with the hx I don't think would yield higher torque. When I put the quick spool valve on my ATT, I made torque a little sooner but it actually made 10ft lbs less. If I recall correctly, peak torque wasn't achieved until 3000 rpm or so anyways. At least with mine.

Do you think the quick spooler was worth the cost and time & effort to install?

 

[WarWagon]

Thanks for going through all the time and work to share. Do you monitor drive pressure? If not, maybe in the future?

Buddy monitored the drive pressure on his I did not. After 6 PSI and some other steps the drive pressure ratio on the GM4 goes up a lot. The ATT stays steady.

That's what I tried telling them over at dieselplace. That my truck with the ATT pulled harder with 0-2 psi than my GM 8 did at 4-8 psi. They just kept arguing it's 4.10 to 3.42 gears and yada yada yada BS.

IAT and drive pressure make a difference to the power you feel. Gears do make a difference, but, with 3.73's and 4.10 I have there is still a difference by changing turbo's. Mainly after the 6PSI drive pressure ratio increase takes place at 2200 RPM killing the GMX while the other bigger turbo's still have pulling power.

 

[6.5L]

It was definitely worth the cost. Wouldn't go back

 

[Bostonguy]

Just installed my ATT on Friday. It sat next to my bed all winter so was more than excited to get it on. I have to say it meets all the hype and worth what I paid. Also installed that stove pipe diamond eye sells, a little loud for my taste. I use my truck for hauling heavy steel. Can't wait to get 4000lbs in the body and climb some hills! Kojo tune coming soon!