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Discussion Starter #1
I’m researching the durability of doing a turbo system on a ’08 2.9 and you guys are about the only source of “applied experience”. First a little background on me. Spent 29 yrs in a Buick Dealer service department, actually grew up there. Bought new and raced a ’78 Turbo/Regal. Slight mod to the induction system resulted in 21lbs boost, 14.10 sec. ¼ mile times with a 292:1 “open” rear gears. Car lived for 24 years and 130k miles before I sold it and was still on original motor and turbo, never having to be opened for repair. I stayed in the business till ’97 so not a whole lot of ‘practical’ knowledge of OBD-II systems.
So now my questions, I see a lot of modifying the “torque management” program during ECM tunes. On Our trucks what parameters is T/Q man. monitoring and what functions does it control? Anybody have information on the harmonic distortion point of the 2.9 Atlas engine? If I upgrade to forged bottom end parts is there any data on rebalancing, including the balance shafts? Anybody know of a source for intercoolers that are not in front of the radiator? Is anybody marketing an exhaust header to place the turbo near the right side of the motor (I don’t have resources to fab. one)? Does anybody have such a set up that lived more than 1 ½ years with a boost limit of 10 lbs.? That’s enough for now, maybe even too much.
Thanks for letting me twist you ears, err eyes,, err brains.
 

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There's no manifolds currently for the 4 cylinders. Cory(05quick4door) would probably make a set-up for you if you left your truck with him. Torque management effects timing and the transmission on automatics.

Tuning for a turbo is much more in depth than removing torque management. You need to understand volumetric efficiency and calibrating the mass air flow sensor as well as fuel injector table modification for the larger injectors you will install.

If you keep the boost mild(10psi and under) with a properly sized turbo a stock motor will last just fine. Most the guys that blew up pushed the timing too far and ran too much boost. Cory our resident expert blew up because he got 87 octane labelled as e85, but he was pulling around 500hp out of the stock 3.5L block. I've been running a centrifugal supercharger at 7psi for about 8 months now and other than some adjustments to the tune every now and then it can be daily reliably. I make a little over 325hp/tq on 7 psi which is plenty for me to have fun with. If I baby it I get better gas mileage than stock as well.
 

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Discussion Starter #4
Horsepower is not the concern for me. My concerns are based on actual torque and what the power train can handle as a whole. I'm not looking to negate your question, and I really don't want to start the whole HP vs Torque debate. If I do an install I'm looking for max torque out put that the power train can handle. In my day, GM's ID of trans units were THM 400, THM 375,THM 350 etc. The number, say 350, meant the trans was designed to handle a max torque input of 350 lb-ft. I as yet have not found the design torque input for the 4L60-E trans but that will be just one of the limiting factors.
My questions are directed at information for planing an installation that will allow max torque without ripping everything apart any time I put the hammer down.
The questions about balance are because I believe the bottom end of this engine is weakest at the pistons and especially the rods. If I were to upgrade to forged rods and pistons the rotating mass would need to be rebalanced. Every engine has a harmonic distortion frequency related to rpm. Changing rotating mass changes the rpm level as well as all of it linear and exponential levels.
My V-6 had its first order level at 2800 to 2900 rpms. So all mods had to be calibrated to keep max power out of that range as well as it's other multiples. I can't help but believe that some engine failures others have had were more caused by harmonics than just boost,detonation, or lean fuel supply.
Sorry for getting carried away. I do believe that the 2.9 will not handle more than 10 lbs boost with a stock bottom end. If data I gain indicates what I expect, likely max boost will only be 6 to 7 lbs.
 

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Melted pistons and floated valves say otherwise. You're thinking way to far into it. If you want a forged bottom end you will be paying for it to be engineered. We dont have off the shelf parts for the bottom end. Our engines also dont have opposing cylinders which amplify the effects of harmonics.

Trans and rear end are good to 450-500 range. Much safer to stay under 400 though.

Sent from AutoGuide.com Free App
 

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I daily my truck with somewhere in the neighborhood of 430hp at the crank (365rwhp)

Nothing has broken. Yet.

I do have a forged bottom end, but valvetrain, trans, rear end, drive shaft, are all stock. And I drag race 2-3 times a month, plus I attend other events on the regular.
 

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Discussion Starter #7
Thanks for the input. Don't misunderstand my brief background info. My tune intentions would be to get either Cory or somebody such as Supermod. I know the original OBD II hardware and interfacing but I'm not a programer. I can use the GM tech II and other type diagnostic tools but I'm lost at writing code. Having left the industry in '97 I'm not up on the changes since then.
Matt, I have read your saga and honestly I agree with some of the ideas on why the destruction with the ceramic pistons happen. But I think it went further than just poor piston fitting and failed coating. Find a tech that worked the Northstar engines and ask about the wash board cylinder walls. Detonation is one problem with high boost but from your pictures you suffered pre-ignition and that is way more destructive. Would have liked to see pics of your plugs.
Anyway I digress, Fixxer ( don't know your given name) thanks for your info. My desires would be to put together a package that would make moderate HP but for me toque is always the quest. I believe something in the range of 325 to 350 lb-ft is where I want to be. From some of the set ups on this sight I think that could happen with around 7 lbs boost. Any more than that would result in traction problems and down here in Louisiana would make the rainy seasons a bitch. If boost comes in too hard I'm sure y'all know how the rear wants to pass up the front.
When backing down the T/M system are we also reducing the spark knock detection response. Back in my day T/M retarded timing and fuel delivery and in some models actually used anti lock brake system to add brake drag in extreme conditions. So I'm looking for info on how the "mechanicals" are used to accomplish control.
As to the harmonics I mentioned earlier, on the Buick turbos believe it or not the first order frequency was around the 2800 to 3000 rpm range. The trick was to get the engine above that point quickly. Too tight of a converter and you were in the middle of the first order and you could feel the shudder through out the chassis. Too loose on the converter at it was hard to launch with out extensive traction work. That's why so many of the pumped up Grand Nationals would lift the front wheels.
Fixxxer I do value your knowledge, I'm just trying to wrap my head around what I might be getting into. I have to keep daily drive ability in mind. The kind of burnouts in Matt's videos are great but with a damp road down here you will be in the ditch quick
 

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Names Justin.

We have a separate system for knock detection and also a thing called piston protection programmed in which adjust timing and fuel according to knock detection from the sensor.

The torque management does have a transmission and engine segment. The engine side messes with the timing and engine parameters, removing this completely is smart. The transmission adjusts shift pressures to limit the trans to a specific torque value but also slips the clutches and messes with the convertor to achieve this. Which is a silly sacrifice in my eyes designed to have your transmission at the dealer once the warranty runs out. Limequat(jeremy) limeswap.com and Cory are your best bet for a tune, they both have plenty experience with boosted atlas motors.

One thing to remember you have a returnless fuel system, meaning the regulator is in the tank built into the pump and you have one single line feeding to the rail. This holds you back from the higher power levels because the stock pump is limited. You probably won't have fuel over any more than what your goals are. I'm running the 60lb injectors and I would certainly run out of fuel WOT over the 7psi I have now. So keep that in mind. Cory, Matt, and the other guys will be able to give you more info on exactly where you will run out.

About the harmonics remember a v6 you have a new set of forces because of the v design. The pistons oppose the crank so not only do you have the rotation, but you also have the opposing diagonal forces hitting the crank each time it goes through the firing order(firing order was a main ingredient for this with the buick v6's). On an inline they push directly down in one direction so it naturally opposes them much better than a V configuration. There are still certainly harmonics but far less critical on the engine. We have a balance shaft as well running down below to combat it further. I understand your concern but with these modern engines it's something you don't really have to sweat unless you are seriously changing the dimensions and weight of the internals. Matt's is a 5 cylinder with custom internals and he hasn't complained of anything resembling it on his current set-up. The 5 cylinders should in theory basically rip themselves apart but for some reason it seems to be a magic number for inline engines with the additional balance shaft, the audis overseas pull some ridiculous numbers out of their 5 cylinders.
 

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Volvo also runs 5 cylinders and so does Ford now. I have 0 complaints about my new engine. The reason the first one failed was detonation, which we knew. The second engine (first forged bottom end) was bad due to a fault by the piston manufacturer (BTW, FUCK THOSE GUYS!!!) We then started with a fresh block (we had to after the sleeve fell apart) and changed the spec that JE Pistons fucked up on and here we are, nearly 10k miles later making more power than before.

There has been talk of removing the balance shafts after having the rotating assembly balanced, but I do not recommend trying. The load created by the shafts is minimal at best and not worth the time to experiment with.

For what you want to get out of your truck, a small turbo is going to be great. If you wanted, you might not even need to run an intercooler, just use methanol injection instead but I would get Cory's input on that. He is much more familiar with the climate you will be in and what your motor will want.

Now, for the fuel pump, most guys are saying around 400rwhp is the absolute maximum on the stock returnless setup. Thankfully Aeromotive makes a fuel pump that can be used with PWM controlled pumps. I believe the Stealth 340 is what you will want to look for. There is also a theory that a stock supercharged CTS-V pump will work, but no one can confirm this yet. Otherwise, you can always switch over to a return style system and take any guess work out of it.
 

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Check out LLV.MA5's build. His goals are pretty similar to the OPs. 2007 LLV 11 lbs boost, 29 mpg, runs high 13s.

Torque management is just what it sounds like. It manages the torque levels for various reasons including traction control, shift comfort, etc. It is normally accomplished via closing the throttle slightly and/or reducing timing.

The bottom end of the motor is good for / reliable to 13 psi assuming a safe tune.
You asked for someone who's been safely boosted for 1 1/2 years? Check out autoroc's build: vortec4200.com ? View topic - Vortec 4200 Turbo engine swap into an IROC Z
I6, but same engine. Boosted since November 2012. Boost levels ranged from 7 psi at the start, to one crazy 17 psi run and then back down to a daily 13 psi. Most of this was done, not only on stock rods/pistons but on stock sparkplugs.
 

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Forgot to mention about the crank.

The crank is solid. Rod journals are 2.2" versus a 2.0" V8. I've heard of one guy who broke cranks. He was running a crazy twin-charged I6 dragster. He was breaking cranks at 1800 hp.
 

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Discussion Starter #12
Thanks so much for the replies from everybody. Based on the info given my main problems with a turbo set up will be cost (wife is a cancer patient in remission) and especially down time of the vehicle. It is my daily driver so things like "send the truck to him for a few days and he could make up a header for you" just really won't work. My hopes are that sometime in the near future somebody could come up with the header matched to a standard turbo flange. Exhaust from the turbo back could be done by locals and the inlet side I can do. For the tune I would have to rely on one of you guys and give you the most accurate details of the overall set up for the tune. There are a few guys around here that do custom set ups and tunes including dyno time but they won't even talk about a tune for these trucks. They specialize in the high end Chevy,FoMoco,and Mopar cars.
So for now I'll keep putting some cash aside in a "me" account and keep my eyes and ears open for those parts I can not have done locally. Again, thanks to all of you!
 

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I've been thinking about balance shafts for a while and here's the conclusion I came to:
The balance shafts are there to damp harmonic vibrations, not to balance an out of whack rotating assembly.

That said, here's what I'd do:
1. Balance the assembly neutral (like you would any other internally balanced engine)
2. Leave the balance shafts there to work their magic on the harmonics
3. Rest easy

You'll love the turbocharged 4cyl. I just moved this week and did some towing with mine (I turned boost down to 8psi for the occasion). It pulls really well and still gets better mileage than an unloaded V8.
 

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Discussion Starter #14
Well Jake, and I'm not trying to start and argument, but I dug up an old contact with GM Service Engineering and you won't like what he said. While it is true that rotating assembly balance is different from harmonic balance, the engineering behind balance shafts is dependent in part to rotating mass. If forged rods, forged pistons, heavier or lighter flywheel, etc. are used the rotating mass has changed. Therefore the vertical and lateral distortion also changes. One of the reasons two shafts were used and where they are placed is that the two forces were 90 degrees apart. One shaft is timed for the vertical and the other for the lateral. He pointed out that on Buick's V6s the shafts have different part numbers between the 3.8L and the 3.0L. Both can use a single shaft with multiple weighted sections because the distortional pulses are more nearly vertical than on an inline engine. But because of the different bore and stroke their masses are not the same. Yes if they used the same bore their piston mass would likely be the same but stroke also plays into the initial distortion rpm and all of the next orders there after.
He reminded me of back in the '80s the "A" chassis car with the 3.8L and standard axle ratio would hit First Order distortion at 55 mph, approx. 1450 to 1500 rpm. The entire car would shake so bad owners thought they had tire balance problem. Some reported hands getting numb holding the steering wheel, others claimed it was so bad they got nauseous. No such complaints from owners with A cars using the 3.0L and all other options the same. The distortion was so bad that the engine would cause the entire body shell to flex. A "special policy" was enacted to add reinforcement bands to the underbody making the uni-body more rigid to prevent the flexing. If the owner was not satisfied the car was bought back. Next model year the 3.8L was not offered in that chassis and the following year the series II engines came out with balance shafts.
The problem with "forging" our engines is the tech. support to develop shaft's for our motors does not exist. There is no way to tell how little or how large of a change in rotating mass cold result in a problem and at what rpm. So his suggestion is being forged components would likely have to be custom built every effort should be made to use material that would allow the forged parts to be as close as possible in weight to that of the originals'.
 

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With current cnc and solid modeling technology, matching the weight of custom rods and pistons to stock is a very simple task. All we have available for our engines are custom parts anyway, so when you order yours, simply specify piston weight along with big and small end rod weight.

Done. :thumbup:
 

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Thanks so much for the replies from everybody. Based on the info given my main problems with a turbo set up will be cost (wife is a cancer patient in remission) and especially down time of the vehicle. It is my daily driver so things like "send the truck to him for a few days and he could make up a header for you" just really won't work.
If I might make a suggestion;
You only live about six hours from Cory. If he were willing to custom fab the parts you need, and if he would require your truck, is it outside the realm of possibility for you rent a car during that time? Seven, maybe ten days? Drive your truck up to him, rent the car locally (as local rentals have unlimited mileage), go home, then bring the car back when he's done with your truck. For the money you intend to invest in this system, a rental car for that amount of time would be well worth it; he would have your truck to work his magic, and you would still have a vehicle.
 

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You're over thinking this. Balance the rotating assembly independent of the shafts and put it together as normal. My internals are over 100g lighter per rod/piston combo and have nearly 10k mi of use and abuse.
 
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