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Discussion Starter · #1 ·
There are tuners out there claiming 200HP gains or so. My stock LLY has 310 HP; 200 more horses is a 65(ish) percent increase. Spark engines are lucky to get 10% more power from tuning alone, so why are diesels so much different?

Is there some downside to adding so much power through tuning changes (other than paying for a Suncoast tranny)?

Without adding any engine hard parts (turbo(s), injectors, fuel pump), how much gain can be had through tuning alone? With the advent of EFILive, it seems the power ceiling will be found soon. Anybody know what that number will be?
 

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When we talk hp ratings on this site we are talking rear wheel hp. (rwhp)
An average LLY duramax will put out somewhere around 250 hp to the rear wheels.

Right now the high hp winner is the PPE Hot xcellerator +2 stacked with the Van Aaken box. This is good for around 470hp at the rear wheels or about a 220hp increase.

Your results may vary.
 

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I don't think you will see anymore then about 500hp with a stock turbo on an LLY.
 

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Discussion Starter · #4 ·
Cripes! From 250 RWHP to 470 RWHP is an 88% increase with tuning alone!

Why are diesels able to achieve such gains when spark engines are not (with tuning alone)? There must be a serious downside to such endevours if the manufacturers choose not to exploit such (seeming) potential, right?

And before I forget, thanx for the education Max!
 

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because Diesel is a more efficient fuel, we have turbos stock, and a Diesel engine will burn almost all the diesel you dump into it providing you have enough air "boost"
 

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the stock computer limits amounts of boost and also limits the fuel pressure.
Adding a tuner increases boost while increasing fuel rail pressure to compensate, the result is lots of horsepower and tons of torque. They do have their limiitations though so don't think if you want big power that you won't have to do some tranny upgrades and stuff.
 

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the biggest problem is EPA, don't think any of the 400+hp trucks would pass a smog test.
 

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Would it be a fair statement to say that these engines are underpowered because of Emissions so increasing the power by 100HP is really what the engine is meant to run? I mean, the engines can run a lot more power but the manufacturer detunes them greatly to pass!?!?!?
 

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The reason they don't run it at higher hp levels is that the current levels are where they feel safe with all the drivetrain components as well as the engine itself. Look at what all they changed and reinforced just to hold another 50hp of the LBZ.

Believe it or not GM does have longevity in mind when they are building these trucks.
 

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Cripes! From 250 RWHP to 470 RWHP is an 88% increase with tuning alone!

Why are diesels able to achieve such gains when spark engines are not (with tuning alone)? There must be a serious downside to such endevours if the manufacturers choose not to exploit such (seeming) potential, right?

And before I forget, thanx for the education Max!
A gas engine only converts something like 8-9% of its energy in to usable energy and a diesel engine converts somewhere around 35% of it energy.
Also manufacturers have to keep all the tree hugger people in washington happy!!!!!!!!
 

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Please don't tell me that the redesign of the LBZ engine wasn't just to strengthen it for 50 more HP. Please do tell me that GM plans to bump it up by 100HP. Actually don't tell me that, I can't afford a new truck for another 4 years, it would kill me to have a 400HP stock Dmax out by fall.
 

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To go along with what Max Power said. They're looking for long term reliability as well as ensuring you don't have problems passing EPA inspections. Tune it down and you've got a cleaner running motor?

It's probably a bad enough image for GM when we're out on the street with our tuners laying down the smoke...

But it's soooo much fun!
 

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Please don't tell me that the redesign of the LBZ engine wasn't just to strengthen it for 50 more HP. Please do tell me that GM plans to bump it up by 100HP. Actually don't tell me that, I can't afford a new truck for another 4 years, it would kill me to have a 400HP stock Dmax out by fall.
I don't know what GM's intentions are. I guess it all depends on where the HP race takes us.
 

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They redesigned the LBZ b/c all (or most) of the LLY's overheating. Lowered the CR back to what the LB7 is and coated the pistons. I think GM did their homework on this engine. Mine doesn't overheat anymore; it just spits coolant once a day and my upper radiator hose is always hard. Dealer, here I come...-:t again.
 

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Also, comparing the small increases to a gas engine you are probably thinking naturally aspirated, it is possible to get pretty big power gains from just tuning on a turbo gas motor as well, same rules, more boost, more fuel.

Cheers,
Ross
 

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They redesigned the LBZ b/c all (or most) of the LLY's overheating. Lowered the CR back to what the LB7 is and coated the pistons. I think GM did their homework on this engine. Mine doesn't overheat anymore; it just spits coolant once a day and my upper radiator hose is always hard. Dealer, here I come...-:t again.
LLY and LB7 have the same CR I thought... 17.5:1
 

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