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Tall gears and big tires... how to adjust my tune?

Oscar135
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Oscar135

Oscar135

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I've been fooling around with moparman1973's tunes on my 2nd gen cummins and figured smoke was just a way of life. However I was recently cruising threads and saw a comment alluding to a required step to adjust something when tuning for a truck with large tires and tall gears. I think I have the absolute worst case for this issue so help or guidance where to adjust would be greatly appreciated. My concern is not mpg but rather managing the fuel and timing curve to light the turbo well and hopefully minimize smoke

 

2001 5.9 valair twin disk nv4500 3.56 with 35" tires. 

SB intake, holset cheetah, afe intercooler and piping, banks high ram, 150hp injectors, 5" exhaust, quadzilla adrenaline using varieties of moparman tunes. 

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Mopar1973Man

Mopar1973Man

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First off welcome to the site...

 

As for your setup your final ratio is too low. With 35 inch tires on 3.55 gears is going to produce 3.27:1 ratio to the ground. You need to change the tires or the axle gear to fix this. You need a final ratio of 3.55 to 3.73 to 1. Optimally if you changed to 4.10 axle gears it would give you 3.71:1 ratio final to the ground with 35 inch tires. 

 

Smoke is going to be a problem till you raise the final ratio. Like myself I'm running 30 inch tires and produces a final ratio of 3.69:1 with 3.55 gears. Turbo lights nearly instantly because of proper final gear ratio. 

 

8 minutes ago, Oscar135 said:

My concern is not mpg but rather managing the fuel and timing curve to light the turbo well and hopefully minimize smoke

 

Tuning will not fix a poor final ratio. The high engine loads to launch will always be there. Being your launching with 35 inch tires is like me launch in 3rd gear. 

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Me78569

Me78569

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Have you followed the steps in the tuning guide to find what your 0 psi tune setting should be for your setup?  The extra load and bad final ratio won't help, but you should be able to clean up a good bit of smoke if you follow the guide.  

 

Mike's tunes will be a good place to start, but messing with the canbus fueling curve should help.   

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Oscar135

Oscar135

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I did! But dang it is low. Using valet power to start with my 0psi level it needs to be at 65%. And can bus is backed off to 60%. I dropped timing a lot under 2000 rpm. Down to 12* and 16* for 1500/2000 respectively to help the turbo spin up. As well as using the low psi timing reduction. This seems to help as once I get over about 10-15psi the exhaust cleans up significantly.  Just one puff of smoke when I push the throttle then a slight haze if I stay on it. It's a slug off the line at 65%. But I noticed it responds much better jacking up 0psi fuel then dropping it to 65% by 2psi. It comes off a stop much better (i always used 2nd gear starts) and I'm off 0psi fairly quickly so I dont leave a plume at the stop. 

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Me78569

Me78569

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34 minutes ago, Oscar135 said:

I did! But dang it is low. Using valet power to start with my 0psi level it needs to be at 65%. And can bus is backed off to 60%. I dropped timing a lot under 2000 rpm. Down to 12* and 16* for 1500/2000 respectively to help the turbo spin up. As well as using the low psi timing reduction. This seems to help as once I get over about 10-15psi the exhaust cleans up significantly.  Just one puff of smoke when I push the throttle then a slight haze if I stay on it. It's a slug off the line at 65%. But I noticed it responds much better jacking up 0psi fuel then dropping it to 65% by 2psi. It comes off a stop much better (i always used 2nd gear starts) and I'm off 0psi fairly quickly so I dont leave a plume at the stop. 

who's injectors?  my starting % with 7 x .012's ( ~200's)  was 68-70.  

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Oscar135

Oscar135

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Adjusted 1500 rpm to 14* and my injectors are "150hp" which I think are 7x.010. But I'm also running the big fuel line upgrade, airdog150 lift pump and "high output" vp44. Advertisement said worth 100hp whatever that is good for. I have a feeling with all this fuel stuff it pumps way for fuel than the truck thinks it is. But managing it down low has proven difficult! 

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Me78569

Me78569

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I was hoping that was not the case.  

 

There is no hope in cleaning up your injectors.  DDP does not use the stock spray angle, or a spray angle I approve of for a vp44 truck.   

 

Various people have tried to tune out the smoke and it never works, the injectors spray too much fuel outside of the bowl resulting in a dirty burn...... which REALLY sucks because DDP are extremely expensive.    

 

A set of run of the mill @dieselautopower injectors run 3x more clean for a given injector size.    

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Oscar135

Oscar135

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Well that's unfortunate! Is there some sort of advantage to the spray angle of DDP for a certain application or is it just messed up? Sounds like move 1 should be different injectors for the smoke management. 

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