twin tuning help!! at a loss!!

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nickg9785

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Mar 14, 2012
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ok, so i have a 1997 12v,
63/68/14 over e.d. 475 1.10 housing
5x.016 injectors
26* timing
full cut dvs
benched 180 pump
air dog 165
tork tek 60 ofv
built auto
goerend triple disk 1800-2000 stall
o ringed head. 60lb springs
4k gov springs
rack plug
from what everyone is telling me i should be in the 700hp area with this setup, just from driving it i am not impressed at all. i have been tuning for 5 months and am getting nowhere. truck makes 80psi overall and 40 out of the primary at wot, primary starts to build boost at about 15lbs which i guess is when the wastegate is opening?? maintains 45lbs of fuel pressure at wot. right now i have a stock 180pump gov spring in the afc to control smoke. the problem im having is the truck has no low end and slow spool up. i had a single 62 before this and you could floor it from a dead stop and it would spin both tires now it wont even do that when it lights. i have a cable ran to the pre boost in cab so i can adjust without popping to hood 50 times while driving. when i set my afc up i used reguated air to make max rack travel at about 70psi. and set the pre boost just to touch the diaphram. and did 1/8th turns from there. am i doing something wrong? any help wpuld be great im going nuts here trying to figure it out. my next step is compression check just to start rueling things out.
 
You have a major drive or boost leak, if the primary is not making any boost until you see total at 15psi there are some big leaks you need to start tracking down.

also loose the full cuts, those just bog down the motor on just about any setup.
 
i have checked for boost leaks and cant seem to find any. i did find a few small ones when i checked last time but fixed them all. as far as drive leaks i dont see any soot under the hood or around any clamps. and when should i see the primary gauge start to move?
 
nickg9785 said:
and when should i see the primary gauge start to move?
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At around 5psi. Loosen up your afc spring so you see max travel at around 45psi. Apply regulated air to set your wastegate so that it just starts to open at around 15-18psi.
 
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benched 180 and 5 x 16s are alot of fuel. Should be ripping.

Maybe try lowering the timing to 22*?
 
If there are no major boost or drive pressure leaks, I'd try 30* of timing and see how it runs.

Maybe your 26* isn't really 26*...
 
I timed it using spill port method, the only thing I didn't do was find true tdc I used the pin to make my mark. I've heard of it being off up to 3*. So worse case scenario I have 23*, do you think that's holding me back? And how would I go about finding true tdc?
 
I like to unhook the big turbo to set the wastegate exactly how I want it. Also lets you know if you have boost creap. This takes the guessing out of it. With the full cuts in a good pump with decent injectors are you putting to much fuel in to early?
 
Not going to know without a dyno, the track, or a Gtech.....80psi should be strong, my 160hp pump truck made 601rwhp at 65psi.
 
thats whats hard the closest track to me is 3 hrs away and same for a dyno. im doing this all by feel and trying to find a safe place on the street
 
i spoke to garmon diesel and they recommended switching to a open delivery valve holder. any one have any thoughts on that? all i see is .093 and .120's
 
I gained 4hp with dv holders...you need a baseline. I would get a Gtech and start testing on the street. They're like $200, and they give acceleration times, g-force, 0-30, 0-60, 1/8th mile, quarter mile, rpm, etc. Even have a tach option so you can see where your trans is shifting. Very useful tuning tool if dynos and dragstrips are far away.

More here:

http://www.dieselpowermag.com/tech/1006dp_gtech_pro_ss_data_logger/
 
i'm thinking he is too aggressive on timing.... i was at 25° but spool was way slow :!:
 
angelic0- said:
back down to 18-20° and see if it does the trick !!!
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I strongly disagree, high boost and low horsepower is a tell tale sign of not enough injection timing creating high back pressure from all the fuel burning in the exhaust tract, spinning the turbine up really well to make boost but not enough timing for the motor to soak up the cylinder pressure and transfer it to the wheels.
 
I would try lowering the timing if it is that gutless on the bottom end. Less timing, more heat.
 
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