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Thread: Project - 408tt Vx Ss

  1. #1
    duke5700's Avatar
    duke5700 is offline Substantial Contributor to the Forum Last Online: 29-03-2024 @ 06:51 PM
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    Project - 408tt Vx Ss

    Now before we go any further, not everything in this post may be correct. Im not a genius and this is only what I do for fun not for profit. There may be some mistakes, please feel free to pick me up on them. I do have a very similar thread on another forum, this has some updates and changes to it from over there.

    Well lads the time has come to move on in this world from N/A puke to forced induction wannabe hero...

    The parts are on there way, I have a sizeable dent in my spendings account and a fair bit of work ahead of me.

    I have spent a fair bit of time re searching on what i need and where i should buy certain parts. I had a plan in mind from the start to make 500+rwkw so I sort of sat down and thought about how easiest this was acheived. The only thing other than to be a show off is to point anyone else in the right direction for the cheapest parts, easiest companies to deal with. I hope to inlcude problems along the way and what i learnt so someone else can do it easier. Hopefully this will include plenty of photos and maybe give people some idea of the headaches and what it takes to build a motor from scratch, size turbos to use and with fuel system to suit.

    I also hope that people on this forum can contribute and help me along the way.

    If the Mods allow I will post the place where i bought each article from and how much i paid including shipping for that item/s. As im a tight ass and dont have a hell of alot of money to throw round anyway you will find a budget conscious underlying tone throughout the build. Mind you in saying that, i have budgeted in the vicinity of around $15,000-$20,000 possibly more but again Im going to do it as responisbly as possible. I dont smoke or drink excessively and cars is basically my ownly hobby.

    Really I have 3 goals for the car.

    1) 500+rwkw
    2) 10.xx 400m @ 130+MPH
    3) Turn it into a tarmac rally car and really enjoy it.

    Anywhoo where I'm up to...


    Engine
    Bottom End


    Block - LS6 Iron Block 4" bore, block prepped for a eventual 4.030" bore. There is a few options for this, a guy on ebay selling them for $950 plus shipping, then there is places like suburban imports @ around $1250 plus shipping or any of the site sponsors.

    Stroker Kit - Eagle 4" crank and 6.125" H beam rods with arp 2000 series bolts. Pistons are Mahle LS1 turbo pistons -32cc dish. Bearings are Fedrul Mogul competition series. Arp Stud kit holding it all together. Compression with the heads im using will be around 8.5:1. This was purchased from dynoflo in the states. As it turns out to get it through customs as it is made in the USA you only have to pay a customs clearing fee of $45 odd dollars and then GST on the purchase+shipping price so all up it was about $25-2600dollars AUS delivered to my door. These guys where a pain to deal with, so I would reccomend steering clear though they are quite cheap. With the way RUSSO are offering there LS6 Ironblock bottom ends, I would of done that easier cheaper and faster, gauranteed product.

    Sump - Not sure exactly where im going to go with this yet as I would like a higher capacity sump. Being a cast aluminium factory sump Im going to assume they are a bastard to TIG weld and hope only to have to weld in -10 returns for the GT35/40's.


    Heads - Will be using L92 heads from Scoggin Dickey sealed to the block using cometic MLS gaskets, they had a special on some CNC versions that flow 345cfm at 600' lift on 4.125" bore. The specs for them are as follows

    Casting Number 12595364 or 12582716
    Valve Angle 15-degree
    Combustion Chamber 70cc*
    Intake Port Volume 279cc*
    Exhaust port Volume 99cc*
    Minimum Cylinder Bore 4.000”
    * Approximate, Numbers are within +/- 2cc’s

    Milling Information for Combustion Chamber Sizing
    - Approximately 0.006” per 1-cc
    For 68-cc Chamber Remove 0.012”
    For 65-cc Chamber Remove 0.030”

    Specifications:
    Springs: SDL1650VS
    Max Lift: 0.650"
    Locks: Manley
    Retainers: Titanium
    Valves: Manley

    Flow Chart:
    Flowed @ 28” H20 on a 4.155” Bore

    Lift 0.100 0.200 0.300 0.400 0.500 0.600 0.700
    Intake 69 154 222 266 309 345 358
    Exhaust 46 100 136 166 189 202 209

    For around $780US each they seem like good value. Freight here im still working on as I hope to get them sent USPS. ( DIDNT HAPPEN CAME FEDEX)

    Lifters, pushrods, pushrod guides, are all Comp Cams stuff off the shelf. i purchased most of this from Alantic speed on Ebay. With the pushrods I went standard in length but I have a feeling i read somewhere that I need longer pushrods, If anyone can confirm or deny this that would be nice.

    Timing chain is rollmaster double.

    Rockers will be yella terra rollers when they are ready

    Camshaft- Not for me to decide. Originally I was going to go off the shelf but realising a cam could make or break this combo, Ive left it in the hands of my engine builder. Needless to say when I was talking to him about a Comp off the shelf he said they dont make one big enough for what you want... go figure. I have an inkling to what size he is going for as I spent an afternoon punching in the numbers, I now know exactly what specs he is going to use but, that is his hard earned knowledge and if you want it you can pay for it. Lets just say is lots of duration lots of lift lots of LSA and no overlap. Clear as mud.

    Intake Manifold/Throttle Body- will be a factory L76/92 manifold. I will see how this performs, Im sure it will meet my goals and HP figures but if it proves to be to restrictive, other than spending a fortune on the new wilson manifold Im not to sure in which direction I will take. RUSSO offer a sheet metal style manifold aswell. This manifold will come from Scoggin Dickey @ $225 US Throttle body will be a BMI brand 90mm cable driven and is around $600AUS.

    FUEL SYSTEM

    This is probably the item that I will fabricate myself the most. It will consist of a Walbro intank feeding a 4.5l surge tank mounted underneath the car, sort of the same position as where say a Mini-Pro mounts. It will have a -10 feed from the tank and a -10 return, 2 -10 feeds into a pair of aeromotive A1000 pumps which will feed into the factory fuel lines (albit with one extra) into Fast Fuel rails into a Aeromotive A1000 Injected Bypass Regulator, P/N 13101 then back via a -10 stainless line into the surge tank. I have drawn a diagram of sorts see attached. Let me know what you think. I will use Bosch 660cc injectors. I calcultated these to do in excess of 500rwkw based on a return system. My thoughts where backed up a few weeks later when a another car that was being tuned albit a 360ci LS1 witha pair of GT28/76r's went 520rwkws with the same injectors.






    The FI side of things
    This is the parts I havnt purchased yet.
    This took me quite some time to work out and took many a debate and crunching numbers to come up with what I was happy with. In the end I settled on a set of manifolds by a gentleman in Queensland. See attached.




    These are built to suit a pair of Garrett GT35/40's internal gate. I will be using external gate and Kyle will make them to suit. More on this later. I cant remember the new part numbers for the Garretts but it will be a 4bolt 1.06 rear and a .70 front housing. Basically as big as i can go without going aftermarket in a GT30 series Garrett frame.The Turbo's are around $1600 ea.





    Boost ControlI will be using a pair of Tial 44mm Wastegates. Boost Control will be with a Eboost(thanks JEZ for the advice on this one). I will also be using two plumback GFB BOV's to keep is as stealth as possible


    Exhaust - I currently have a diffilipo dual 2.5" but will be selling it off for a dual 3" funds permitting, if not a xforce.

    The final engine assembly should begin soon just waiting on a few more parts. I will then have the motors swapped and it will be put on a trailer so i can finish of the fuel system and intercooler piping. Im going to take as many photos as possible and hopefully make this a decent running story.

    Now for the fun stuff.... Turbo sizing...

  2. #2
    duke5700's Avatar
    duke5700 is offline Substantial Contributor to the Forum Last Online: 29-03-2024 @ 06:51 PM
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    Re: Project - 408TT Vx Ss

    Now someone who is more knowledgeable may be able to help more here but this is how I made it work.

    OK Guys as promised... How I picked my Turbocharger/s

    At first, when I was being sensible I was looking at turbocharging my stock engine. After much deliberation I choose a pair of GT28/76's, basically as large as you can go in a Garrett GT28 size frame. The compressors flow 440hp worth of air each and being realtively small ball bearing units would see full boost below 3000rpm, making 5 or 6 pounds at about 2300rpm. In other words a massive lower/midrange but only very slightly tapering off towards 6250rpm when they start to lose there eifficiency.

    I sized these turbos up on the large cubic inch motor, and talk about come on boost hard. Anyway, these turbos where pretty much aperfect match for a 346-360ci engine but where starting to struggle on the larger cubic motor. If you can keep your turbo's efficent and your charge temp down, you can run more timing less fuel and make more power. A gentleman I know is using these on his forged 360ci. Stock heads, good sized turbo cam, made 522rwkw. Great little turbo's. Though he was running exotic fuel, so on pump roughly a 450rwkw pair of turbos.

    So the hunt was on for another pair of suitable turbos.

    No for those of you who want to cheat, and size your turbos the easy way I suggest this website. Though you will need to know your VE of your engine and a few other bits a pieces.

    http://www.turbofast.com.au/javacalc.html
    http://www.buicks.net/shop/reference/carb_cfm.htm

    I would just like to state this is not my work... I found it on the internet but served me pretty well until I bought a decent book on the subject. The text in bold is mine and most likely has the errors.


    The purpose of this little paper is to show the reader how to calculate the volume and mass of air moving through his engine, and how to size a turbochargers' compressor to move that quantity of air. It should also offer some enlightenment of the effects of temperature, pressure, and intercooling on the engine's performance.
    Engine Volumetric Flow Equation
    This equation is for finding the volume of air going into the engine. The displacement on our cars is 231 cu.in. We have a four stroke engine; the intake valve on a cylinder opens once every 2 revolutions of the engine. So, for every 2 revs the engine takes in 231 cu.in. of air. How many pounds of air is that? That depends on the pressure and temperature of the air in the intake manifold. But the volume is always 231 cu.in. every 2 rpm.

    volume of air (cu ft/min)= engine rpm x engine cid / (1728 x 2)


    So therefore (cu ft/min)= 6500rpm x 408ci / 3456 = 767CFM @ 100% VE

    Now at this point its easy to go one step further and times this equation by your VE and you will have your calculated CFM, you can either do this with an educated guess IE 80% or work it out via this next method

    - worth noting for you guys with maf's still in place i believe you can work out your VE by simply calculating your CFM @ 100% efficency then comparing actualy CFM as measured by the MAF then work it out like so

    actual CFM Measured / Calculated CFM x 100 - This will give you a VE %

    So therefore at my guesstimate of 85% VE It works out as such

    (cu ft/min)= 6500rpm x 408ci / 3456 x .85 = 652CFM


    Ideal Gas Law/Mass Air Flow
    The Ideal Gas Law is a handy equation to have. It relates the air pressure, temperature, volume, and mass (ie, pounds) of air. If you know any three of these, you can calculate the fourth. The equation is written:

    PV=nRT

    where P is the absolute pressure (not the gauge pressure), V is the volume, n is related to the number of air molecules, which is an indication of the mass (or pounds) of air, R is a constant number, and T is the absolute temperature.

    What are absolute temperature and pressure? Do we care? Of course we do!

    Absolute pressure is the gauge pressure (measured by a gauge that reads 0 when it is open to the outside air) plus atmospheric pressure. Atmospheric pressure is about 14.7 psi at sea level.

    Example: a boost gauge reads 0 psi before it is hooked up. Hook it up, boost the car, and it reads 17 psi. 17 psi is the gauge pressure, the absolute pressure at sea level is 14.7 + 19 = 33.7.

    A pressure reading is marked psia or psig. The "a" stands for absolute, the "g" for gauge. (The psi stands for Pounds per Square Inch). As we just showed, 17 psig = 33.7 psia. A perfect vacuum is 0 psia, or -14.7 psig.

    The absolute temperature is the temperature in degrees F plus 460. This gives degrees Rankine, or deg R. If it is 80 deg F outside, the absolute temperature is 80 + 460 = 540 deg R.

    The Ideal Gas Law can be rearranged to calculate any of the variables. For example, if you know the pressure, temperature, and volume of air you can calculate the pounds of air:

    n=PV/(RT)

    That is useful, since we know the pressure (boost pressure), the volume (which we calculate as shown in the first section "Engine Volumetric Flow"), and we can make a good guess on the temperature. So we can figure out how many pounds of air the engine is moving. And the more pounds of air you move, the more power you will make.

    Here is the Ideal Gas Law rearranged to the two handiest forms, with the required constants:

    To get pounds of air:
    n(lbs/min)= P(psia) x V(cu.ft./min) x 29 all divided by / (10.73 x T(deg R))


    To get the volume of air:
    V(cu.ft./min) = n(lbs/min) x 10.73 x T(deg R) all divided by / (29 x P(psia))

    Celsius to Rankine Conversion http://www.metric-conversions.org/te...to-rankine.htm


    So for lbs a minute in my case hoping to run up to 20psi n = (14.7+20) x 652 x 29 all divided by / (10.73 x 549) = 111.4lbs/min

    Volumetric Efficiency
    If life was perfect, we could fill the cylinders completely with air. If we had 17 psi boost in the intake manifold, we would open the intake valve and get 17 psi in the cylinder before the intake valve closed. Unfortunately, this doesn't usually happen. With some exhaust remaining in the cylinder and the restriction offered by the intake ports and valves the actual amount of air that flows into the cylinder is somewhat less than ideal. The amount that does flow divided by the ideal amount is called the volumetric efficiency.
    For your basic stock small block chevy, I think this number is around 0.85 (or 85%). Things like big valves, big cams, ported heads, tunnel rams, etc... get this number closer to 1.0 (or 100%). With tunnel rams some normally aspirated cars can get over 100% at certain rpms due to the ram effect.

    To take this into account when we calculate flow into the engine, we multiply the ideal amount of air by the efficiency to get the actual amount of air:

    actual air flow = ideal air flow x volumetric efficiency

    Example
    Time for an example. Lets calculate the pounds of air flowing into an engine for two different cars, an intercooled '87 and a nonintercooled '85. For both cars we will use a volumetric efficiency of 0.85. For both cars the engine is turning at 5000 rpm. What is the volume of air it is using?

    volume, in cu.ft per minute = 5000 x 231 all divided by / 1728 x 2 = 334.2 cfm


    This holds true for both cars, both intercooled and nonintercooled will be moving 334.2 cfm of air into the cylinders at 5000 rpm. As we will see however, the mass of air flowing is not the same.

    Suppose the car an '85, so it isn't intercooled. The temperature in the intake manifold is about 250 deg F. The car is running 19 psi boost. What is the mass of air the engine is using?

    Absolute temperature = 250 deg F + 460 = 710 deg R

    Absolute pressure = 19 psig + 14.7 = 33.7 psia

    n (lbs/min)= 33.7 psia x 334.2 cfm x 29 all divided by / 10.73 x 710 deg R = 42.9 lbs of air per minute (ideal)


    lbs air per minute actual = lbs/min ideal x vol. eff.
    = 42.9 x 0.85
    = 36.4 lbs air/minute

    What if the car is an '87, it IS intercooled, so the temperature in the intake manifold is only 130 deg F. This car is running 17 psi boost.

    Absolute temperature = 130 deg F + 460 = 590 deg R
    Absolute pressure = 17 psig + 14.7 = 31.7 psia

    n(lbs/min)= 31.7 psia x 334.2 cfm x 29 all divided by / 10.73 x 590 deg R = 48.5 lbs of air per minute (ideal)


    lbs air per minute actual = 48.5 x 0.85 = 41.3 lbs air/minute

    Notice that the '87 car is getting MORE lbs/min of air (41.3 for the '87 to 36.4 for the '85) even though the boost pressure is lower. This is because the intake manifold temperature is so much lower. And more pounds of air means more power!

    Compressor
    The compressor is the part of the turbocharger that compresses air and pumps it into the intake manifold. Air molecules get sucked into the rapidly spinning compressor blades and get flung out to the outside edge. When this happens, the air molecules get stacked up and forced together. This increases their pressure.
    It takes power to do this. This power comes from the exhaust side of the turbo, called the Turbine. Not all of the power that comes from the turbine goes into building pressure. Some of the power is used up in heating up the air. This is because we lowly humans cannot build a perfect machine. If we could, all of the power would go into building pressure. Instead, because of the design of the compressor, the air molecules get "beat up", and this results in heat. Just like rubbing your hands together will warm your hands due to the friction between your hands, the friction between the compressor and the air and between the air molecules themselves will heat up the air.

    If you divide the amount of power that goes into building pressure by the total power put into the compressor, you get the efficiency of the compressor.

    For example, if the compressor is 70% efficient, this means that 70% of the power put into the compressor is used in building air pressure. The other 30% of the power is used heating up the air. That is why we like high efficiency compressors; more of the power is being used on building pressure and less is used heating up the air. Turbos, Paxtons, and Vortechs are all centrifugal superchargers. The are called this because the centrifugal force of flinging the air molecules from the center of the housing to the outside edge is what builds air pressure. The maximum efficiency of these kinds of superchargers is usually between 70% and 80%. Roots blowers, like the 6-71, work differently and have much lower efficiency, like about 40%! With those, when you try to build lots of boost you have to put in a lot of power and more than half of it gets used heating up the air instead of raising pressure.

    If the temperature goes up a lot when you increase the boost you can end up with fewer pounds of air going into the engine, so you lose power. That's why a Roots blower is bad if you want lots of boost. Screw compressors, like the WhippleCharger for the 5.0, have good compression efficiency. That's why the Top Fuel guys are starting to try them out, and getting good gains from them.

    So? How Hot is the Air Coming out of the Compressor?
    Well, I'm glad you asked. The equation used to calculate the discharge temperature is:
    Tout = Tin + Tin x [-1+(Pout/Pin)0.263]
    efficiency

    Example: the inlet temperature is 70 deg F, the suction pressure is -0.5 psig (a slight vacuum), the discharge pressure is 19 psig, and the efficiency is 72%. What is the discharge temperature?

    Tin= 70 deg F + 460 = 530 deg R
    Pin= -0.5 psig + 14.7 = 14.2 psia
    Pout= 19 psig + 14.7 = 33.7 psia
    Pout/Pin = 33.7/14.2 = 2.373 (this is the compression ratio)

    Tout = 530 + 530 x (-1+2.3730.263 ) all divided by / 0.72 = 717.8 deg R - 460 = 257.8 deg F

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    Re: Project - 408tt Vx Ss

    So the theoretical outlet temperature is 257.8 deg F. I sure would like to have an intercooler to cool that hot air down before it goes into my engine!

    Compressors do not always operate at the same discharge pressure. The discharge pressure that the compressor produces depends on the volumetric flow into it (not the pounds of air, but the CFM of air), and the rpm that it is turning. The performance of a compressor can be shown on a graph by a series of curves. Below is a compressor map from the Turbonetics catalog attached, it is the file called H-3.JPG. [The graph is included here, and is available for download via the hotlinks provided....Ed.]





    turbo graph



    This is for their Cheetah turbo; take a look at it. The bottom of the graph shows the lbs/min of air that the compressor is moving, corrected to a standard temperature and pressure. The standard industry practice is to put this part of the graph in actual volumetric flow (such as ACFM) since the compression is constant for a given volumetric flow and compressor speed, NOT for a given mass flow. Unfortunately they didn't do their curves that way, and to use the Turbonetics curves we have to figure out the pounds of air moving and correct it from the actual inlet temperature and pressure to their standard temperature and pressure.

    The left side of the graph shows the outlet pressure to inlet pressure ratio.

    There are two different sets of curves in the graph; efficiency curves and rpm curves. The area where there are lines drawn is the operating envelope. It is best to operate the compressor within its envelope. It will still run if you go to the right of the envelope, just not well. To the left of the envelope, where it is marked "surge limit", the flow through the compressor is unstable and will go up and down and backwards unpredictably. This is surging. Do not pick a turbo that will operate in this area! It can be very damaging.

    The Turbonetics catalog says to pick a turbo that is close to the peak turbo efficiency at the engine's torque peak while still maintaining at least 60% efficiency at the maximum rpm of the engine.

    Here's how to read the graph.
    Figure out the pounds of air that you are moving through the engine. In our '87 example, we were passing 41.3 lbs/min of air, at inlet conditions of -0.5 psig and 70 deg F. Now correct that flow to the standard temperature and pressure.

    Corrected flow = actual flow x (Tin/545)0.5
    (Pin/13.949)

    Note that I am using 13.949 because we are measuring everything in psia instead of in inches of mercury, which Turbonetics assumes.

    13.949 psia = 28.4 inches mercury absolute.
    29.92 inches mercury is atmospheric pressure at sea level, so 29.92 - 28.4 = 1.52 inches mercury vacuum.
    That is their standard suction pressure.

    Their standard temperature is 545 deg R, or 545 - 460 = 85 deg F.

    So we are correcting the flow from 70 deg F and -0.5 psig to 85 deg F and -0.75 psig (or 13.949 psia, or 0.75 psi vacuum, or 1.5 inches mercury vacuum, or however you want to look at it.)
    Again, temperature and pressure have to be absolute.

    Tin = 70 + 460 = 530 deg R
    Pin = -0.5 + 14.7 = 14.2 psia

    Corrected flow = 41.3 x (530/545)0.5 = 40.0 lb/min
    (14.2/13.949)

    So we mark that point on the bottom of the graph, and draw a straight line upward from that point.

    An alternate and better way of getting airflow at less than full throttle is the use of a scan tool. The scan tool (such as TurboLink(tm)) reads the mass air sensor output. TurboLink(tm) gives this in grams per second. To convert that to pounds per minute just multiply by 0.1323. For example, if TurboLink(tm) says 18 gm/sec @ 45 mph, 18 x 0.1323 = 2.4 lb/min of air.
    Correct that to standard conditions and plot that on the compressor map. Unfortunately the MAS will only read to 255 gm/sec. If you are moving more air than that, the MAS won't show it. That is why you need to go through the above calculation for full throttle air flow.

    The next step is to figure out the compression ratio, using absolute pressures. Using our example, we had 17 psi boost in the intake manifold. Let's suppose the pressure drop from the turbo outlet to the manifold is 3 psi; so the actual compressor outlet pressure is 3+17=20 psig. The air pressure is 0 psig, but since the turbo is sucking air to itself the pressure at the inlet is lower than that.

    Let's say it is -0.5 psig at the inlet. Then the compression ratio, Pout/Pin is :

    Pout/Pin = (20 + 14.7) = 2.44
    (-0.5 + 14.7)

    So then we find about where 2.44 is on the left side of the graph and draw a line horizontally from that point. Where the two lines meet is where the turbo will operate.
    Look at the efficiency curves, which look like circles. Our point is just a little inside the 72% curve, so when we are running at 5000 rpm and 17 psi boost with 70 deg air outside and 130 deg air in the manifold then the compressor efficiency is a fraction over 72%.

    The other curves are rpm curves. Our point is above the 105,500 rpm curve, so the turbo has to spin about 108,000 rpm to get the pressure up to 20 psig from -0.5 psig. The Turbine has to provide enough power to spin it that fast.

    Change any of these numbers, and the point at which the compressor runs at changes. More engine rpm means more air flow, so the operating point moves to the right. Colder intake temperatures means more pounds of air which moves our point to the right. Raising the boost probably means more air into the cylinders, but also the compression ratio goes up so our point definitely moves up and should move right. And so on.

    Summary
    So, how do tie all this together? Well, suppose you are in the market for a new turbo. Which one to buy?
    First, I would pick about 4 different operating scenarios. Highway cruise, part throttle acceleration (say 2/3 @ 2700 rpm), full throttle acceleration at 3500 or 4000 rpm, and full throttle acceleration at 5500 or 6000 rpm sound like 4 good points to me.
    Second, calculate the volumetric flow for each one of those cases. Then, making estimates of the intercooler outlet temperature (or turbo outlet temperature if nonintercooled), turbo discharge pressure, volumetric efficiency, manifold pressure, etc.. calculate the mass air flow for each case. You may also want to check the difference between summer and winter, ie air temps at maybe 90 deg F and 40 deg F. This will affect the manifold temperature and so the air flow. Note that when cruising and at idle, even though the manifold pressure is at a vacuum the turbo discharge pressure is not. It has to pump up the air some, even if it is only to 0.5 psig or so. You can check it out by moving your boost gauge to some point upstream of the throttle body. Besides the mass air flow, calculate the Pout/Pin for each case.
    Third, and this is the hard part, find the compressor maps for the turbos you are interested in. Turbonetics has maps for their Cheetah, 60-1, and 62-1 in their catalog. The other vendors may not want to let you have the maps for theirs. Plot the points from the 4 cases on the compressor map.
    Fourth, evaluate the proposed compressors performance. Are the idle/cruise operating points to the left of the surge line? Then this turbo will surge and isn't a good choice. Is the 5500 rpm point so far out to the right that it is off the map? Then this turbo doesn't flow enough for your application. You want all the operating points within the map, and preferably at as high an efficiency as you can get.
    If you are trying to choose between 2 turbos, pick the one with the better efficiency where you do most of your driving.
    Good luck!

    OK so after reading all that you get it right.... I wouldnt worry to much about it. If you think about it a XR6 turbo runs a GT35/40 running a 1.06 rear its 4L, Hm I have to 3.4ish L banks on my engine plus better heads and nice manifods and the like. So two 35/40's would go pretty close right maybe a smaller rear housing like a .86. Well yes and no but a hell of alot of people just go on what other people have done or get someones else advice that has done it before.

    But anyway I mapped out 5 points and plotted on my turbo flow map.

    2500rpm denoted by the green spot
    3500rpm denoted by the red spot
    4500rpm denoted by the black spot
    5500rpm denoted by the orange spot
    6500rpm denoted by the pink spot

    Again all this can be done via the Ray Hall Turbocharging Website if you cant be bothered, though it only has the older T series turbo compressor but some of them are the same as the GT series anyway.

    So first of all I worked out my CFM for each point

    250CFM @ 2500rpm
    350CFM @ 3500rpm
    450CFM @ 4500rpm
    550CFM @ 5500rpm
    650CFM @ 6500rpm

    Then calculated the lbs/min as most turbo graphs are in this form

    So Im using guestimation for temps rankine but will ramp to a max temp of 549deg Rankine or 50 DegC and PSI as i would like it to be.

    (15.7x250x29)/(10.73x504) = 21bls/min @ 2500rpm at 1psi of boost pressure over atmosphere
    (19.7x350x29)/(10.73x522) = 35.7lbs/min @ 3500rpm at 5psi of boost over atmosphere
    (24.7x450x29)/(10.73x540) = 55.7lbs/min @ 4500rpm at 10psi of boost over atmosphere
    (29.7x550x29)/(10.73x549) = 80.4lbs/min @ 5500rpm at 15psi of boost over atmosphere
    (34.7x650x29)/(10.73x559) = 109lbs/min @ 6500rpm at 20psi of boost over atmosphere

    So we have to divde these by two as Im using two turbo chargers

    And this is where it plots on the graph, I only did this rough as alot of values are estimates and not actual calculations but it looks ok to me. Im not probably going to run 20odd psi in the car at any stage but it just goes to show you the more air flow vs boost the less efficient your turbos become thus heating up your charge air.

    Last edited by duke5700; 11-06-2008 at 10:08 PM. Reason: Automerged Doublepost

  4. #4
    mustanger's Avatar
    mustanger is offline Considerable Contributor to the Forum Last Online: 18-07-2020 @ 08:46 PM
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    Re: Project - 408tt Vx Ss

    I think you have to do some more homework. One of your calculations was out by .000001.

    Congrats Duke and all the best with your mods

  5. #5
    TAKEITEZ's Avatar
    TAKEITEZ is offline Fair Contributor to the Forums Last Online: 15-08-2016 @ 03:03 PM
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    Re: Project - 408tt Vx Ss

    far out!...
    i think i'm going to have to read this after work tomorrow...
    will be watching with interest though mate... it appears that you've left no stone un-turned...

    good luck with everything, and i hope you achieve your goals with minimal fuss

  6. #6
    TommyVTss is offline Fair Contributor to the Forums Last Online: 05-12-2015 @ 07:50 PM
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    Re: Project - 408tt Vx Ss

    hey mate hope it all goes well, you sure did your homework.

    tom

  7. #7
    brock05's Avatar
    brock05 is offline Forum Contributor Last Online: 10-09-2019 @ 03:35 AM
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    Re: Project - 408tt Vx Ss

    would be interesting if tuna could comment on your research and selection?

  8. #8
    Delft Maloo's Avatar
    Delft Maloo is offline Fair Contributor to the Forums Last Online: 04-03-2024 @ 05:26 PM
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    Re: Project - 408tt Vx Ss

    Quote Originally Posted by duke5700 View Post

    Really I have 3 goals for the car.

    1) 500+rwkw
    2) 10.xx 400m @ 130+MPH
    3) Turn it into a tarmac rally car and really enjoy it.
    How funny is it that your goals are nearly the same as mine.
    A pair 35's with a 1.06 rear will certainly give you a massive top end, im running a single atm and when i upgrade it with a larger single i will still be only running a .96-1.05 rear a/r. I would have thought a pair of .84 rear a/r's would have been more then enough for the total output and given you a more midrange grunt.

    good luck with it and do keep us updated with pics please.
    cheers tim.

  9. #9
    vuss383's Avatar
    vuss383 is offline Fair Contributor to the Forums Last Online: 31-03-2016 @ 05:54 PM
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    Re: Project - 408tt Vx Ss

    I had speced a pair of GT35/82R's for my 383 a while back . Was going to try with the .82 -.86 rear & if it wasn't large enough go up to the 1.06 . I opted to throw on a set of Tuna's TTZ's ( roughly 30/60's I was told ) on for some R&D . My research is now done & have a cast 6lt block awaiting to be built . When time permits my build will begin, aims for some serious RWKW out of this 1 !

    Duke you have done your homework & an A+ would be awarded for your effort !!


    Troy
    Last edited by vuss383; 11-06-2008 at 11:30 PM.
    2007 Textralia LS1 Drag Nationals LSSS WINNER
    2007 V8 Owners Willowbank private day DYO WINNER

  10. #10
    vpstroker is offline Forum Contributor Last Online: 01-07-2012 @ 10:58 AM
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    Re: Project - 408tt Vx Ss

    goodluck in the project champ sure did your homework congrats

  11. #11
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    duke5700 is offline Substantial Contributor to the Forum Last Online: 29-03-2024 @ 06:51 PM
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    Re: Project - 408tt Vx Ss

    Quote Originally Posted by Delft Calais View Post
    How funny is it that your goals are nearly the same as mine.
    A pair 35's with a 1.06 rear will certainly give you a massive top end, im running a single atm and when i upgrade it with a larger single i will still be only running a .96-1.05 rear a/r. I would have thought a pair of .84 rear a/r's would have been more then enough for the total output and given you a more midrange grunt.

    good luck with it and do keep us updated with pics please.
    cheers tim.
    Sounds good lads ^^

    Your dead right .86 would speed up the gas flow and give better response, but I dont think it will be to bad with the way it is. When i look towards track days and so forth a set of .86 rears will probably be swapped onto it. I just want to get this engine done make the power I want to achieve run the times I want to at the strip, full street trim (MT streets) run a 10.

    I really wanted to steer clear of some of the kits as I believe they where poorly engineered APS kit aside. Though certainly some of the kits now I would'nt think twice about, like the ASE etc. There was that issue plus they wouldnt get me where I wanted to go, well that and I thought I could do it better for not alot of dollars more.

    I really do have to thank some of the Forum members and Sponsors (you know who you are once its all done cartons of whatever are comming your way) otherwise I wouldnt of got as far as I have.

    Im hoping that this engine will go close to 500rwkw on 10psi

    When I have time I will go into how I plan to run the car on Methanol, wind the wick up and see if it wont make some real boogey for dyno days etc etc

    Any guesses what it will make? Im going to start the bidding at 600rwkw.

  12. #12
    Delft Maloo's Avatar
    Delft Maloo is offline Fair Contributor to the Forums Last Online: 04-03-2024 @ 05:26 PM
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    Re: Project - 408tt Vx Ss

    Quote Originally Posted by duke5700 View Post

    When I have time I will go into how I plan to run the car on Methanol, wind the wick up and see if it wont make some real boogey for dyno days etc etc
    mate i think 2 great minds think alike as ill be persuing this same path for some big number action and mostly for extra safety on the drag strip.

    I agree with you when it comes to buying off the shelf turbo kits, there are a couple of good ones around now but when i first built my f/i setup it was pretty limited and the $ were ridiculas so i thought i could build my own for cheaper and i did. i originally was going to do a tt setup up with the 2 t04's i got but when i looked into it they just would have been way to big for a stock and decided to go with a single setup which i like better in my setup. My single to4 was still good foe 390-400rwkw.
    We should catch up when all this gets under way so we can check out the 2 setups.
    cheers tim

  13. #13
    joffa's Avatar
    joffa is offline Forum Contributor Last Online: 02-01-2022 @ 12:08 AM
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    Re: Project - 408tt Vx Ss

    Subscribing

    Good luck dude!

  14. #14
    michaels1v8's Avatar
    michaels1v8 is offline Fair Contributor to the Forums Last Online: 23-01-2018 @ 12:40 AM
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    Re: Project - 408tt Vx Ss

    Awesome thread mate

    Looking forward to the build

    Good luck

    definately appears as if you have done your research

    I learnt ALOT!

  15. #15
    duke5700's Avatar
    duke5700 is offline Substantial Contributor to the Forum Last Online: 29-03-2024 @ 06:51 PM
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    Re: Project - 408tt Vx Ss

    Quote Originally Posted by michaels1v8 View Post
    Awesome thread mate

    Looking forward to the build

    Good luck

    definately appears as if you have done your research

    I learnt ALOT!
    Yeah spent a bit of time playing with my own VL Turbos and mates boosted cars. Realised I didnt know as much as I should know on the topic, bought a few books read alot of forum's and hunted around the web for good information. Took a while but it was well worth it in the end.

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