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Discussion Starter #1
My buddy just had a DSP5 installed by a local tuner on his 05 LLY EC/LB 3500, and when I asked him how he liked it he said he was kinda disappointed. When I asked him why he said the truck wasn't making any power, so we went for a ride.
On all switch positions the truck is a dog until 2000rpm then it takes off like a fighter jet. It sounded to me like the turbo wasn't even beginning to spool until 17-2000rpm. Told me it was even worse on cold start-up, and that when he was pulling a 35ft gooseneck loaded with hay up an incline last week the truck downshifted revved to like 3 grand then limped the tranny??
I want to help him out since he's a close friend, but I told him to go back an ask the guy who did it to look over the tunes and if it didn't get better I could look at em.

My main question is what do you guys think is going on and what should I be looking for if he asks me to check them out?

Tunes are:
mod stock
light tow
heavy tow
Street/Race
Race(idk how much rwhp)
 

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Hang it!...Fire!
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that doesnt sound right at all considering its got a vvt. go back to the tuner cuz i build boost way faster than that when i was stock
 

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he needs a mouthpiece for one... and from what i understand when you install your ECM you can bend the pins and it can cause trouble like this..... also when was the last time he changed the fuel filter.... with my tunes from ROB i roast my 37s like no other
 

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also who are the tunes from??? does he have the V2? i have heard that some tuners create high end power and the other produce low end... personally with mine it feels like its power all over the place
 

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Does it whistle more than normal?

Does it blow a whole bunch of smoke before it spools................
 

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If he has a different air intake it may be that the MAF needs to be rescaled. That can be done with EFI and the tuner should have asked about that and made the appropriate changes. My LLY was acting the same way as I had installed a different MP and a LBZ Banks intake. After the rescale the drivability was much better.
 

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Discussion Starter #8
Does it whistle more than normal?

Does it blow a whole bunch of smoke before it spools................
I haven't seen it cause it was dark when I rode in the truck but he says it rolls coal like a freight train.

also who are the tunes from??? does he have the V2? i have heard that some tuners create high end power and the other produce low end... personally with mine it feels like its power all over the place
Tunes are from a local tuner Logan Deck, he's done a number of trucks that lay down some good power all over, this is the first one I've seen that has had problems.
If he has a different air intake it may be that the MAF needs to be rescaled. That can be done with EFI and the tuner should have asked about that and made the appropriate changes. My LLY was acting the same way as I had installed a different MP and a LBZ Banks intake. After the rescale the drivability was much better.
He's already done the S&B LBZ intake w/ LBZ turbo inlet, so i'll tell him to have the MAF rescaled and see if it gets better.
 

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Quicker Then Brian!
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The maf needs to be rescaled for the bigger intake tube. however the one thing that worries me is that if MAF limiting is or is part of the issue it shouldn't smoke a ton.

my flow rate table with the 4" intake looks as follows

85.179688
99.359375
115.921875
135.343750
157.921875
183.835938
213.148438
245.898438
282.039063
321.515625
364.281250
410.335938
459.703125
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000

Works well for me after much playing

Also, remember LLY's are the laggiest of all duramax's IMHO
 

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Discussion Starter #10 (Edited)
Also, remember LLY's are the laggiest of all duramax's IMHO
I hadn't heard that about the LLYs, somthing new to keep in mind I guess. Can you explain more about the MAF limiting tables, I kind of understand whats going on but some of it still isnt' too clear. If it is part of the problem the trucks getting to little fuel?
Thanks I'll pass this info along and hopefully they get it straightened out.
 

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Quicker Then Brian!
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Yea, it will make the truck a pig. i had this issue when i first switched to a 4" intake.


Bacially the MAF takes the place of the aneroid valve in a machanically injected motor,.

If you just let it fuel based in throttle position alone it would smoke like no tomorrow and be highly innefficent. basically the MAF limiting say's to the injection system "hey there, you need more air to burn this much fuel...so i''m going to allow you x amount of fuel that i know you do have enough air for. kthxbi"

then you increase diamater of the intake piping you loose air velocity. which is what the MAF sensor reads. it uses a forumla to figure the air flow based off velocity and pipe size. when you increase size and lower velocity without telling the truck you did so, it thinks you're getting far less air due to the reduced velocity.

Hope that helps
 

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Discussion Starter #12
Now it all makes sense, Thanks for the explanation :drink
Theres still so much out there for me to learn when it comes to EFI, can't wait to get into the good stuff
 

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Yea, it will make the truck a pig. i had this issue when i first switched to a 4" intake.


Bacially the MAF takes the place of the aneroid valve in a machanically injected motor,.

If you just let it fuel based in throttle position alone it would smoke like no tomorrow and be highly innefficent. basically the MAF limiting say's to the injection system "hey there, you need more air to burn this much fuel...so i''m going to allow you x amount of fuel that i know you do have enough air for. kthxbi"

then you increase diamater of the intake piping you loose air velocity. which is what the MAF sensor reads. it uses a forumla to figure the air flow based off velocity and pipe size. when you increase size and lower velocity without telling the truck you did so, it thinks you're getting far less air due to the reduced velocity.

Hope that helps






Fuk'n A Beech that is the best way of explaining it that I have ever heard. Good Job
 
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