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My turbo build. 5.3/t56 with a GT45

Time:2012-05-19 17:28Turbochargers information Click:

Turbo Build 5 my 10

and then plotted the 15 psi of boost on the map guess what, I will try to keep this short...... Here goes. Boost is the EXTRA air a 35.html">turbo is trying to pump into a motor. If the motor flowed the air as fast as the 35.html">turbo tried to pump it in, and thats the max and still being on the map. If you asked well at what hp level would it be working at peak efficiency for 11 psi....it would be about only 425hp !! this would also be working at a pretty decent efficiency around 600 hp. I am looking to turbo a 4.8 so my boost to go 800hp would have to be higher than 11psi i was just using 11 psi because alot of the guys on here are running 5.7's and 6.0's around the 11 psi range. If I needed 15 psi to run 800hp on a 4.8, you would never get into boost. This is most noticeable during spool up or during the lag stage. The motor is wanting to flow more air than the turbo so we dont have pressure building in the intake. Once the turbo starts spinning fast enough that it starts out flowing the motor air will start backing up in the intake manifold and the boost gauge starts climbing. So that part is pretty basic...... the compressor section of a turbocharger is a centrifugal compressor. A compressor like this wants to do TWO things as is spins faster. In the case of a turbocharger feeding a motor air it will want to do these two things. It will want to flow more air AND it will want to build more pressure. Because of this when you pick a turbocharger you pick it based on how much HP you expect to make AND at what boost level. You do not pick a turbo based on I want to make 700hp.... you pick a turbo based on I want to make about 700hp at 12 psi (for example). This isnt voodoo magic this is just how a pump or a compressor of that style works. Spin a turbo faster it wants to flow more air and wants to build more pressure. If you look at compressor maps over and over and you pay good attention to them you will see a couple things: 1. Alot of times the advertized hp capability is actually off the graph. Like with my GT4202R, at 750 hp I fall off the map. At the 15psi I would be at peak efficiency around 500hp and a decent efficiency up to about 680hp. In the case of my GT4202R being rated to 1000 hp..... If i wanted to make 800hp with this turbo @ 15psi of boost on a 4.8 it would be too small! Could i hit the number? could it do it? sure but it wouldnt be working well. I am going to make a guess here.... Turbos are getting more and more popular. They are really catching on and are being put on a whole lot more motors that werent turbocharged from the factory. This is really cool for a turbo fan like myself. The problem is the market has been driven by the four and six cylinder crowd for years. Its a simple matter of thats where the customers and their money was. Now enter the LS guys with their stock motors with their high flowing stock heads and roller cams. You guys are making so much hp naturally aspirated that the flow to boost ratios are basically off the damn charts! In the turbo world its always been considered better to error a little small on the turbo selection especially for a street car. The LS guys may be the first crowd that gets told you better go a little bigger than you think you need HTH , if you plot out 1000hp on the compressor map for that turbo on garretts site you are literally off of the graph. infact about 950 hp is about where the efficiency islands stop being plotted. 2. Most modern turbos like to build boost. They have very vertical compressor maps compared to some of your old school turbos like say a 60 dash 1. Because of this the center of about every single compressor map out there is around the 24 to 27psi of boost range. Now this is the middle of the map, so what boost range do you think they are in at close to the rated up to hp for a given turbo?? Its usually in the 30's some where. In the case of my GT4202R the up to 1000hp plots around a max of 950 with 0out going off the graph and it does this in the 33 to 37 psi range. lets stick to this GT4202R a bit longer. Lets say I want to put it on an LS motor and run 11 psi of boost. If I then look at Garretts compressor map for this turbo and look for whats the MAX Hp I can make with it and atleast still be on the map. Its approx 650hp,。

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