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There has been A LOT of chatter on here lately about the boost numbers that the MTW Turbos are making (namely with the Hybrid Turbo) and everyone is concerned that say a MTW Stage 2 or Hybrid turbo only makes 24-26psi of boost where their stock turbo makes upwards of 30 psi with the same tuning. Now while there are some things that play into turbo spool up and top end boost, the fact of the matter remains that folks are concerned that they may not be getting "all" of the performance that there is to get from these turbos since their boost numbers aren't the same as the stock turbo.

I need to pause for a second here to say that I am in no way trying to do anything here but put out what I believe to be factual information based on research that I have done and what I have been able to observe/read about with respect to turbo performance (kind of like an independent party if you will).

Ok so I did some digging and due to the dimensions posted by Adrian of his turbos and the fact that they are made by Garrett, I went and looked the compressor maps and plotted where these boost numbers were falling out at. The stock turbo is a GT3782 compressor and based off my calculations (derived from the formulas in the Garrett Tech articles), I find the stock turbo to actually be flowing between 40 and 45lb/min of air at 30psi of boost. The Stage 1 turbo is based off the GT3788 compressor (same one as the Powermax) and at 28-29psi of boost (this was the highest that I ever saw with my truck) I find that turbo to be flowing appromximately 60lb/min of air. Lastly, the Stage 2 (while on my truck made 26-28psi) only seems to produce 24-26psi. At 24psi, the Stage 2 (according to the GT4088 compressor map) flows approximately 65lb/min of air.

Now of course one can make the argument that these are only calculations and that I don't have any basis for saying that these turbos are actually performing when in fact I do have real world experience that can be vouched for. Both Matt and Chris of the GPDA have nearly identical trucks when it comes to performance enhancing mods and both trucks even run 35in tires. Both trucks were ran on the same day with the same dyno, using different ECM tunes but the same FICM tune and had the stock turbo and dyno'd 451rwhp (Matt) and 454rwhp (Chris). Then they went and dyno'd on a hotter day a few month's later (again on the same day), this time, Chris with the Stage 1 turbo and Matt with the Stage 2 turbo (before it went on Bill's truck for a while). This time Chris dynos in for a best run of 473rwhp with the Stage 1 and Matt dynos a best of 485rwhp with the Stage 2.

I know folks want tend to want to ignore the math and the calculations and the graphs and charts and just go bolt stuff onto their truck (I know because I am one of those guys), but I really think folks need to learn about this stuff so they can know for themselves of what to expect from a certain product before they buy it. I wish we had more data and could do more runs like the guys at GPDA did here but the bottom line is that the math works. I know no one wanted to believe that 600-640hp with 190s was possible with a single VGT turbo, but I know Adrian did the math and the math said it was and low and behold it was true.

One last correlation of data here. I went to Turbo Engineering Corp's (TEC) website and looked at the data that they are claiming for their turbos (as they use some similar wheel sizes to the MTW Turbos) and their claimed numbers fall right in line with the same results being produced by the MTW turbos.

Based on the GT4088 compressor map, I really think that the max boost that should be ran with this turbo is about 32psi as there just isn't any more of a gain in airflow with that boost pressure and at that pressure, there is about a 5lb/min increase in airflow to what is currently being produced by the Stage 2 which I think might just be what a truck with a healthy set of stock injectors, fuel system, and the right tuning might be able to use to hit that ever elusive 500hp mark for stock injectors.

If nothing else comes of this thread, I hope it spurs some good discussion and encourages more folks to research and understand how they can develop an idea of what to expect from the product they choose to buy.
 

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We we have to take it down. A notch or two on the itellegence scale and set the charts and graphs down for a bit. That numbers are created as a best case senerio. The way I see it.. if you are useing a pnewmatic tool, same tool,same size air line, the only way to increase performance is psi. It does not matter the size of compressor on the other end. 20 psi is 20 psi. Recover will change and initial charge rate will change but if a smaller compressor can keep up at a certain psi the tool runs the same. I realize the smaller one working harde hill heat the compressed air more acting like less psi but this is if it is operated outside of its effiecency range. If other variable are change such as coupler fiting or size of hose then yes the volumn will change at the same 20psi. On my truck egt and maf # tell me that the psi I see is the same between stock an the hybrid. I am now capable of monitering the back pressure and might put the stock snail back on in a bit to see the difference.
 

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The way I see it.. if you are useing a pnewmatic tool, same tool,same size air line, the only way to increase performance is psi. It does not matter the size of compressor on the other end. 20 psi is 20 psi. Recover will change and initial charge rate will change but if a smaller compressor can keep up at a certain psi the tool runs the same. I realize the smaller one working harde hill heat the compressed air more acting like less psi but this is if it is operated outside of its effiecency range. If other variable are change such as coupler fiting or size of hose then yes the volumn will change at the same 20psi.
This analogy is not really accurate in relation to turbos. The main factor in determining the perfomance cabability of a turbo is not the max boost pressure, it is the mass flow rate of the compressor, measured in lbs/min. The mass flow rate is the product the cross-sectional area of the path of flow (which is constant in this case), the velocity of flow, and the density of the air charge. Turbo Compressors that flow more air will do so by increasing the velocity of the airflow, and increasing the density of the air charge. Both of which can be done without necessarily increasing boost pressure. The rings on a compressor map represent the percent efficiency at a given pressure ratio and mass flow rate. If a compressor is operating more efficiently, it will deliver a cooler, denser, and higher velocity air charge, meaning a higher mass flow rate at that pressure ratio than a less efficient compressor.
 

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The only way to increase velosity through the same orifice, in this case the intake manifold and ports, is to increase pressure. Velocity is measured at maf. If this number is the same between two compressors smame amount of flow minus heat but if both chargver are running in an efficient range this variable would be minimal... Intercooler would be more cost effective. Other wise and I believe this to be your and nates case is you are measuring potential not actual.. potential means nothing if it can not be reached.
 

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I'm really hoping to hit the 500 mark on stock injectors. I don't want to sound arrogant, but I (along with other people) believe my truck is going to be the one to do it. I hit the rollers on the 29th..
 

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Discussion Starter #6
The only way to increase velosity through the same orifice, in this case the intake manifold and ports, is to increase pressure. Velocity is measured at maf. If this number is the same between two compressors smame amount of flow minus heat but if both chargver are running in an efficient range this variable would be minimal... Intercooler would be more cost effective. Other wise and I believe this to be your and nates case is you are measuring potential not actual.. potential means nothing if it can not be reached.
I too am referring to actual gains in performance and not only potential. While you are correct in thinking that A (not the ONLY) way to get more air through the same size hole is by increasing the pressure of the driving force for that air. Now pressure is nice and volumetric air flow is nice but just because those to values are the same DOES NOT mean that the Hybrid is flowing the same amount/mass/# of molecules (whatever you want to call it) of air as the stock turbo; as you are forgetting about the temperature of the air. I say this because if you look at the compressor maps of the the GT3782 (stock turbo) compressor map and compare it to the GT4088 (Hybrid and Stage 2) compressor map, you'll see that 28-30psi of boost (with the calculations provided by Garrett) puts the Hybrid in a WAY more efficient part of the compressor map than in comparison to the Stock turbo and therefore, simply due to this increase in efficiency, the Hybrid flows more cool air than the stock turbo at the same boost pressure and volumetric flow rate of air; BUT since the temperature of the air flowing in is lower with the Hybrid, the actual mass of air is more and therefore more oxygen is reaching the cylinders in comparison to the stock turbo. Again this has been shown to be the case with both the Stage1 and Stage 2 turbos on the same dyno. I hope this makes sense.

I'm really hoping to hit the 500 mark on stock injectors. I don't want to sound arrogant, but I (along with other people) believe my truck is going to be the one to do it. I hit the rollers on the 29th..
What is the gear ratio in your truck's rear end DeepDish?? I ask because if you have anything lower than a 3.73 (i.e. 4.10s, 4.30s, etc.) then you will be at a little more than a 1:1 ratio and the true output of your motor isn't being reflected at the wheels of your truck because most folks only really accept the 3.73s with stock tires as the 1:1 ratio. This is the same thing for the guys running 35s or 37s with 3.73 gears as they will not make as much power as the guys with stock tires and gears because their trucks are less than a 1:1 ratio and again a true reflection of what their motor is putting out is not being reflected at the rear wheels because their drive ratio is off. So for either case, if the guys with larger tires put lower gears in then their rwhp numbers would go up and if the guys with lower gears and stock tires put larger tires on, their rwhp numbers would come down and both would be a true reflection of what their truck's motor is really putting down to the ground. I hope this makes sense and doesn't seem like I am trying to be difficult or anything. Just trying to accurately peoples' expectations.
 

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Boost is also a reference of restriction. Doing much needed port jobs, cleaning up the intake, etc...can actually lower boost but improve performance.

The common turbo maps show lb/min airflow and pressure ratio. Pressure ratio is ((boost+14.7)/14.7). The thing to think about is that if you want to push 25psi at 2000rpms vs 4000rpm's. You will need much less lb/min at 2000rpm's vs the 4000rpm's. Just make sure you push the turbo past its surge (demanding high boost #'s at low rpm's) or the opposite end of the spectrum (high boost at high rpm's). I use to know how to calculate the need lb/min of a engine at a specific rpm but that is eluding me right now.

Looking at the compressor maps you can see how the 4088 will flow more lb/min at a certain pressure ratio vs the 3782.

PV=nRT

Pressure x Volume = moles (R constant) Temperature. It isnt exactly the perfect equation (its one of those textbook equations, real world is obviously different) but should give you an idea.
 

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We we have to take it down. A notch or two on the itellegence scale and set the charts and graphs down for a bit. That numbers are created as a best case senerio. The way I see it.. if you are useing a pnewmatic tool, same tool,same size air line, the only way to increase performance is psi. It does not matter the size of compressor on the other end. 20 psi is 20 psi. Recover will change and initial charge rate will change but if a smaller compressor can keep up at a certain psi the tool runs the same. I realize the smaller one working harde hill heat the compressed air more acting like less psi but this is if it is operated outside of its effiecency range. If other variable are change such as coupler fiting or size of hose then yes the volumn will change at the same 20psi. On my truck egt and maf # tell me that the psi I see is the same between stock an the hybrid. I am now capable of monitering the back pressure and might put the stock snail back on in a bit to see the difference.
There is a lot more than just 20 psi is 20 psi in reference to a turbocharger or supercharger. Volume of air being pushed, efficiency of compressor (both adiabatic and volumetric) as well as any other supporting mods on any specific truck can affect boost levels and power.

That being said you can make MORE power from LESS boost with a more efficient compressor....as air is compressed it creates heat which is not condusive to making power once you reach a certain level with say a stock turbo it will just become inefficient at making more power. Go to a more efficient compressor and with the same or less boost you can make more power.

Without getting to technical that is the basics and what nate posted in much more detail. I learned much about this from the engineers at paxton/vortech when we designed the first supercharger setup for the hemi cars. You can make more power with the same boost just by bolting on a different trim blower that was more efficient. That is why turbos and superchargers are NOT one size fits all.
 

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There is a lot more than just 20 psi is 20 psi in reference to a turbocharger or supercharger. Volume of air being pushed, efficiency of compressor (both adiabatic and volumetric) as well as any other supporting mods on any specific truck can affect boost levels and power.

That being said you can make MORE power from LESS boost with a more efficient compressor....as air is compressed it creates heat which is not condusive to making power once you reach a certain level with say a stock turbo it will just become inefficient at making more power. Go to a more efficient compressor and with the same or less boost you can make more power.

Without getting to technical that is the basics and what nate posted in much more detail. I learned much about this from the engineers at paxton/vortech when we designed the first supercharger setup for the hemi cars. You can make more power with the same boost just by bolting on a different trim blower that was more efficient. That is why turbos and superchargers are NOT one size fits all.
note that I did refer to the differences in charge temprature temptature and any differences,of which I have yet to learn or see from the garret page is lessened with the cac. Allthough I agree that there is a difference it does not equal the increase that is possible by increasing boost 1-5 psi while staying inside the effiecency range and with out over boosting.
 

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When the boost numbers are observed are they on a mechanical gauge or through the map sensor? Also what year trucks are these numbers observed on? I am under the impression that the 03-04.5 trucks will boost more due to the ECM deboosting the engine. Does one think they could see higher boost numbers on a 03-04.5 truck with a mechanical gauge as apposed to a 06 with a map sensor boost gauge?
 

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When the boost numbers are observed are they on a mechanical gauge or through the map sensor? Also what year trucks are these numbers observed on? I am under the impression that the 03-04.5 trucks will boost more due to the ECM deboosting the engine. Does one think they could see higher boost numbers on a 03-04.5 truck with a mechanical gauge as apposed to a 06 with a map sensor boost gauge?
I have 3 boost gauges. The insight, my snow controller which measures absolute manifold pressure and my 05 came stock with the analog in the dash. I do not know how that one recieves its info. All three are consistant. I have read, any thing through the obd port will read 29 max. I have the snow controller hooked to back pressure and it will read 40+.
 

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I have 3 boost gaugeg. The insight, my snow controller wish measures absolute manifold pressure and my 05 came stock with the analog in the dash. I do not know how that one recieves its info. The stock one on the dash reads from the map just like your insight All three are consistant. Have read any thing throu the obd port will read 29 max. This is true, the map is only a 3 bar sensor I have the snow controller hooked to back pressure and it read 40+.Welcome to the world of VGTs
An intercooler cannot negate the effects of temperature on the density of the air. The intercooler is only so efficient. If hotter air enters it, hotter air will come out. The statement that the only way to increase flow through an orifice is not completely true for a gas, it is for a liquid because liquids are incompressible. If you have lots of time on your hands, google Euler's equation and get ready for some dry reading. Euler derived an equation that relates pressure, velocity/flow rate, and density and trust me it is rather complex, but it gives a reason why this isn't as simple as an increase in boost pressure equates to an increase in the airflow into the engine.
 

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The way I see it, boost is a measure of restriction. X amount of air will flow only as unobstructed and as straight a shot is the path. Alot of folks say they lose a little boost when they put an intake manifold on, but the truck runs better, because it's flowing the same amount of air with less restriction.

But, you have to have so much pressure to load the cylinders.
 

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Yes boost pressure is a measure of restriction to the air flow, and increasing the air flow will result in a gain in power but due to the compressability of air it is possible to increase the volume of air (via compression) increasing it's density with out seeing a substantial rise in boost but you have effectively increased the amount of air being pumped into the cylinder.
 

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The way I see it, boost is a measure of restriction. X amount of air will flow only as unobstructed and as straight a shot is the path. Alot of folks say they lose a little boost when they put an intake manifold on, but the truck runs better, because it's flowing the same amount of air with less restriction.

But, you have to have so much pressure to load the cylinders.
Agree, the quickest and easiest way to over come restriction is with pressure. Staying with in efficiencies. Second I would say is by increasing volumn. Ported intake manifold and head. I would guess boost should be similar until the compressor can not truly keep up with demand. This is with all other variables and peramaters removed. Just talking flow as a mesurement. Third in my opinion would be density. Expecially that some ways to achieve this have all ready been put in place... CAC.
I just noticed Adrian posted psi #'s for the stage 2. They seem quite high for such an efficient compressor.
 
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