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Low Boost/slow spool on GM3

6.5L

6.5L

Old Iron Runner
Messages
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Location
Northwest Wyoming
When I was running my GM-3, it didnt start to even spool at WOT until 1700rpm. That was with the added fuel and everything. Is it because I have a manual? All these people seem to talk about spooling with the stockers right off the line. I never had that or experienced it. I think I actually have less smoke with the ATT than I did with the GM-3. And before you ask, the GM-3 was in perfect working condition. Nothing broken or bent and no play at all.
 
I have no experience with a GM3. Is it the one with the mech. factory waste gate? Maybe your spring was weak if that is the case?
 
6.5L said:
Can anybody explain my GM-3 issue? I am really curious
Click to expand...

Off top of my noggin, the GM-3 is less efficient than the newer turbos and more back pressure impact in it than say a GM-8 does, IIRC the GM-3 is also a spring actuated WG, and a stiffer spring or a TM fully adjustable WG is what could have let it have more performance
 
Didn't you have your IP rebuilt for a stuck advance piston? Timing affects boost.

The WG flapper inside can come loose and bind up if you have manually opened the WG. The WG shaft can also bind up. It normally doesn't open that far, but, will reach a point that it generates boost even wide open.

The factory spring is weak only holding ~6PSI of boost. As I recall it wasn't very snappy aka a dog in factory trim. I added a Turbo Master after turning up the fuel and that made it snappy. The newer vac systems may work better by holding the WG closed biased off boost not exhaust backpressure.

Restricted kitty does NOT apply. :cool:

No. My GM3s with a TM would spool up about the time the starter kicked out. Of course you factor in the converter slip and it quickly gets to a higher RPM than a manual with full fuel applied. Don't forget you loose turbo RPM on each MT shift throttled or not due to load changes. Had 2 GM3's on 2 6.5's in the past few years and they were always snappy off the line with a Turbo Master. Then they fing choked, rolled over and played D E A D! :mad2:
 
Even after the fresh motor and rebuilt injection pump, when I had to run my GM-3 for about 3 weeks until the ATT went on, it still didnt spool until about 1700rpm, that was with my custom wastegate setup. I had it set to open at 18psi. And I was wondering where this thread went. I kept looking for it haha
 
My gm8 didn't spool under 1500. If I recall correctly, it wasn't till closer to 1700 that it really came alive.
This was a 2829 pump with fuel screw in against.
 
My gm8 didn't spool under 1500. If I recall correctly, it wasn't till closer to 1700 that it really came alive.
This was a 2829 pump with fuel screw in against.
 
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