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Turbos & intercooling

6.5dragracer said:
what kind of turbo do i have to use i'm looking for one i think mine is bad think the bearing is going out in it...
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Probably a GM-4, read the metal tag on it, it will say,, on edit I thought you were asking what kind do you have, any GM turbo will work, but the ATT works better and costs less new than a reman GM turbo

Don't waste $$$ on electric fans in your sig, they don't flow enough air better to buy a Heath cooling system upgrade.
 
ercaduceus said:
Thanks, I think i'm learning. Shhh!! Don't tell anyone.
If this is a bigger turbo, why does it not have lag?
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It does but not significant enough lag that it is negatively impacting the driveability of the truck, and why from day one as was posed in the other thread it has always been suggested as a towing turbo vs. a race turbo, removing the IC that started this whole thread improved that lag.
 
ercaduceus said:
Slim. I notice you have an 18.1 motor. Does it make a noticable difference running the ATT with lower compression? With 18.1 should you up the boost to make up for the drop in compression? I guess that would take a design change to the ATT since there is no wastegate. What compression would work best with this turbo?
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I do have an 18 1 motor because I spend a lot of time in the higher rpm range with 4.10 gears so I don't really have an issue with lower compression. I would stick with the factory compression ratio if I had a higher gear ratio for highway use. I set mine up for towing heavy at highway speed. The motor is smooth as glass at higher rpm and boost pressures of 10 psi or greater, it really shines at 2500 rpm and about 10 to 12 psi of ATT turbo boost.
 
ercaduceus said:
Thanks, I think i'm learning. Shhh!! Don't tell anyone.
If this is a bigger turbo, why does it not have lag?
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As Turbine Doc said it doesn't have enough lag to be an issue, but it is a noticeable improvement over the gm series turbo.
 
6.5dragracer said:
what kind of turbo do i have to use i'm looking for one i think mine is bad think the bearing is going out in it...
Click to expand...


You can buy one from me if you decide the ATT A-Team Turbo replaces all of the factory turbos, with improved results . The turbo is 700.00 plus shipping PM me if you are interested.
 
Slim Shady said:
I do have an 18 1 motor because I spend a lot of time in the higher rpm range with 4.10 gears so I don't really have an issue with lower compression. I would stick with the factory compression ratio if I had a higher gear ratio for highway use. I set mine up for towing heavy at highway speed. The motor is smooth as glass at higher rpm and boost pressures of 10 psi or greater, it really shines at 2500 rpm and about 10 to 12 psi of ATT turbo boost.
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Sounds like a sweet set up.:D
 
Turbo-lag is less noticeable with an automatic transmission than a manual transmission because the hydraulic coupling is a constant load on the crankshaft, even in PARK\NEUTRAL - when any gear range is selected the torque-conversion function further increases that loading - to get a sense of the auto\manual difference, select P\N, rev the engine a few times, noting Boostability - then select any of O-3-2-1, give the throttle a few blips, again noting Boostability - crankshaft loading increases exhaust energy, particularly at off-idle where the GM-X series were specifically spec'ed to operate in order to get torque up to move the load
 
gmctd said:
Turbo-lag is less noticeable with an automatic transmission than a manual transmission because the hydraulic coupling is a constant load on the crankshaft, even in PARK\NEUTRAL - when any gear range is selected the torque-conversion function further increases that loading - to get a sense of the auto\manual difference, select P\N, rev the engine a few times, noting Boostability - then select any of O-3-2-1, give the throttle a few blips, again noting Boostability - crankshaft loading increases exhaust energy, particularly at off-idle where the GM-X series were specifically spec'ed to operate in order to get torque up to move the load
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Agreed, I know with the manually shifting gears it really takes the bite out of a turbo. You have to spool that lost energy back up, the ATT does very good at recovering from those shifts. The NV4500 leaves a lot to be desired between the 2-3 and 3-4 shift, the gears are spaced out a little to much for my liking, if they were closer in ratio towing would be much improved. I can't imagine how smooth an automatic must be towing with the ATT turbo, because the load on the engine is much more constant.

I
 
ATT question - turbo thoughts

Have any of the ATT-users monitored turbine drive pressure? That might add some useful data to the discussions. I wonder if comparing developed boost pressure - vs - turbine drive pressure on these different setups wouldn't help us better understand what's going on.

Also curious about the dual scroll on this turbo & if it's a Mitsu design I haven't seen before. I'm familiar with some of the twin scroll turbine sections, but these would require an exh manifold setup that keeps 1 bank of exhaust "putts" seperate until they hit the turbine wheel. They're often used on 4 cyl's; the exh manifold simply divides down the center - 2 cyl on each side.

My understanding of the twin scroll concept is that each exhaust "putt" coming out of its exhaust port only expands into 1/2 the exh manifold & turbine throat volume - so it loses less velocity (as compared to an undivided maniold/turbine throat) & in theory imparts more energy on the turbine wheel.

On the wastegate/no wastegate subject, most of the OEM (GM-X's & Holset HX-35) wastegate passages designs could be better. The way the bypass exhaust exits & re-enters the exh stream causes turbulence.

Using an external wastegate(s) w/ correctly sized turbo(s) might allow for a lower boost threshold/rpm & still avoid too much restriction at the higher flow rates. Food for thought, although that's probably more fabrication than I'm interested in doing.

1995 K2500, 8600 GVWR, 6.5TD, NV4500, 3.73:1, 18:1, balanced, Fluidampr, DSG timing gears, '97 cooling upgrades, 2100 psi/pop injectors, K&N air filter, 4" exhaust, ceramic coated exh manifolds/turbine housing/crossover pipe, Autometer: pyrometer, boost, oil temp, oil press, fuel press, & water temp gauges, remote oil filter, B&M plate-style oil cooler w/ braided SS oil lines, 30 micron Racor fuel filter - pre-lift pump
 
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ak diesel driver said:
Just curious how you would be able to measure that?
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I've seen trucks at truck pulls with a copper line running off the exh manifold, but it wasn't the pyrometer line. Couldn't see in the cab but figure the line ran to something like a 100 psi blower gauge.

Don't know if the length of copper line keeps the gauge well enough isolated from the egt's, or if something specifically designed to monitor turbine drive pressure is needed.

I mentioned wondering about turbine drive pressure as I read all the discusion on turbos for the 6.5 w/ interest. Years back I participated in forums for modders of the 1st generation AWD Eagle Talon's w/ a 2.0L turbo gasser. (I bought a '91 new & eventually built in into a 3200 lb car capable of running low 11's at 125+ mph in the 1/4 mile - impressive at the time, from 2.0 liters; but not so uncommon now).

Watched over time as many different turbos were tried & knowledge of what worked evolved. The turbo discussions were similar to the 6.5 turbo discussions now. Understanding turbo theory, collecting & analyzing real-world data, & trial-n-error all can contribute to advancing the hobby. I'm just thinking knowing the boost:turbine drive pressure ratios of these setups might be an objective measure of what folks are trying to describe.
 
Since it was only meant to be a temporary thing, I bought a $20 boost/vac gauge some copper line, and tapped the exh collector just below the turbo inlet adjacent to the EGT probe. Have it hanging from the cup holder for now, probably going to make it a permanent install when I swap out my engine.
 
I have it somewhere maybe a scrap of paper, but I thought I had posted it, I'll go back and look at replacement thread, basically less than 20 psi BP at WOT & 13 psi boost, with GM8 WOT 30+ BP @ 15 psi boost. Cruising 2500 rpm with ATT 5 psi BP @ 3psi boost.
 
Turbine Doc said:
I have it somewhere maybe a scrap of paper, but I thought I had posted it, I'll go back and look at replacement thread, basically less than 20 psi BP at WOT & 13 psi boost, with GM8 WOT 30+ BP @ 15 psi boost. Cruising 2500 rpm with ATT 5 psi BP @ 3psi boost.
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Yeah, I suspect it's challenging (intended understatement) to come up with a setup coming verclose to the magical/almost mythical 1:1 ratio - given the relatively wide rpm/load range we'd like our pickups to perform in. But certainly better than the GM-X at cruising speeds.

Wouldn't it make sense that this is the cause/effect answer to folks seeing/feeling better performance at a given boost level?
 
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