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Re: Turbo Manifolds 2008
do some dyno runs. put the log on and run it. then throw the tubular on and run it. it would be good info to have posted up and that would show you the difference. i dont know where your at but by me you can get 3 runs for like 80 bucks. just see if you can run once then pull your car off and swap ---- out and run it again for the same price. it would show you the difference in the power band and what not.
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Re: Turbo Manifolds 2008
run a mini ram, they're bottom mount.
http://www.omenspeedworks.com/images/pagan-2-done-1.jpg theyre a good split between ram and log |
Re: Turbo Manifolds 2008
To add on to what Inquisition said about scavenging and preventing reversion in a log mani, cam overlap is a key factor in bumping up both of those. It helps promote scavenging by utilizing some of the forced air being pumped into the engine to help keep the exhaust moving quickly, and at the same time obviously prevents reversion. The only big losses are a drop in boost pressure (very slightly and can be made up for with a boost controller) and a slight drop in bottom end power and slightly later spool time.
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Re: Turbo Manifolds 2008
that manifold pictured is pretty nice, it would be hard to do much better as a high end geared compromise between decent spool and outright power.
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Re: Turbo Manifolds 2008
Originally Posted by fe3tcourier
that manifold pictured is pretty nice, it would be hard to do much better as a high end geared compromise between decent spool and outright power.
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Re: Turbo Manifolds 2008
1 Attachment(s)
what style manifold do i have ? and can you guys pick out any floors from the photo's?.
Im still running the Standard turbo camshaft, when going to a tubualr manifold should one aslo increase the lift in the cam? i have heard increasing the duration on a turbo cam will decrease performance. Im defiantly going log as the Tubular hasnt worked out for me. Which manifold would supply more flow? Both of these manifold with supply better spool than the loggy? 4-2-1 Manifold Attachment 21903 Or Pure Log http://www.rcautoworks.com/images/uploads/IMG_2754.JPG |
Re: Turbo Manifolds 2008
the first one is nice for a log. if the inner runners were also curved and angled toward the merger, it would be better, but its good.
the second one uses the rounded both ways T pieces for 2 and 3, i dislike those because they offer no direction to the escaping gas and significant reversion could/will occur. try http://www.mx6.com/forums/1g-mx6-forced-induction/ for f2t mani pics and places like http://www.clubprotege.com/ for bpt ones. |
Re: Turbo Manifolds 2008
That first on you just posted will flow smoother than a straight log. I think it's pretty sexy.
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Re: Turbo Manifolds 2008
Originally Posted by Schwitzer Turbo
what style manifold do i have ? and can you guys pick out any floors from the photo's?.
Im still running the Standard turbo camshaft, when going to a tubualr manifold should one aslo increase the lift in the cam? i have heard increasing the duration on a turbo cam will decrease performance. Im defiantly going log as the Tubular hasnt worked out for me. Which manifold would supply more flow? Both of these manifold with supply better spool than the loggy? 4-2-1 Manifold https://i238.photobucket.com/albums/...s/DSC00754.jpg Or Pure Log http://www.rcautoworks.com/images/uploads/IMG_2754.JPG Hi Schwitzer , have a look at this link , gives a good explanation on turbo camshaft selection and the different characteristics that a log manifold and tubular header tuned length manifold prefers in turbo camshaft profiles. Schwitzer can you quote you camshaft specs please ? http://www.forcedinductions.com/help.htm Turbo Cam Selection 101 How to select a turbo cam Duration: Duration is critical to a turbo setup since its probably the single most important event of a turbo motor (i.e. time valve sits open and closed). Since the air is being forced instead of drawn into and out of the combustion chamber, duration will be your largest variable on how that incoming/outgoing air is managed. Duration when using a manifold or log design on most turbo cams is usually about 6 degrees more intake duration than exhaust duration (226/220, 240/234). This is mainly because a manifold/log design will typically see higher then a 2:1 pressure ratio in the exhaust ( as high as 4:1 with some logs). By using a reverse split duration this will somewhat help prevent from getting exhaust gas reversion. Duration when using an efficient header setup with most turbo cams will usually be (230/230, 224/224) or better known as a dual pattern cam. The thinking is with the exhaust backpressure being only 2:1 you can leave the exhaust valve open a little longer then if the exhaust backpressure was 3:1 or higher. Also some of the new turbo designs produce a much lower backpressure with the advent of better flowing turbine wheels and housings which further decrease the total amount of backpressure created by the system. Overlap: Overlap definition, is the time period when both the exhaust valve and the intake valve are open at the same time. The exhaust valve needs to stay open after the piston passes TDC in order to use the vacuum created of the exiting exhaust gases to maximize the amount of exhaust gas drawn out of the cylinder. The intake valve opens before TDC in order to use the vacuum created by the exiting exhaust gases to start drawing the intake charge into the cylinder. This sequence of events above are controlled by the duration and LS (Lobe separation) of the cam. On a typical N/A motor this is essential since you have no pressure being developed on the intake side to push the charge into the combustion chamber. The problem with this event is a turbocharged motor will create a larger amount of backpressure on the exhaust side. Due to this event the above definition will not apply. Reason being is, when the intake valve opens at BTDC, the burned gasses in the chamber will exit out the intake since the pressure is lower than the exhaust. Since this is true you would not want to open the intake valve until the piston has started going down, ATDC. This will lower the combustion chamber pressure till it's below the intake manifold pressure. To calculate the overlap of your cam simply follow these steps below: **Example turbo cam:** Duration @ .006 218/212 Lift .544/.544 lift Lobe Separation (LS) 114 Add the intake and exhaust durations Divide the results by 4 Subtract the LSA Multiply the results by 2 Overlap is -6.5 Degrees of overlap **Example N/A cam :** Duration 236/242 Lift .568/.576 Lobe Separation (LS) 112 Add the intake and exhaust durations Divide the results by 4 Subtract the LSA Multiply the results by 2 Overlap is 15 Degrees of overlap Above was the process on how to calculate your cams overlap. As you can see, the overlap in the 2 cams differ greatly. Running the N/A cam example on a manifold setup would be a horribly in-efficient setup and the engine would be operating well below its potential output. While running the example turbo cam would work well even with the most in-efficient of the header systems out there. Typically a overlap ------ of -8 degrees to +2 is a safe bet. Of course this will differ with whatever combination header, turbo and exhaust is used, so those #'s could be higher or lower. Lift: How much lift should I get in my cam? Well that will depend on your heads' flow characteristics. To choose the correct turbo camshaft, you really need to know how your cylinder heads flow. Reason is if your cylinder head flows X amount of air at X amount of lift, choosing a cam that has a lift much greater then that will gain you nothing except extra heat and premature wear of the valve spring. Airflow through a head reaches a peak as the valve is opened, then starts to drop off as the valve is lifted beyond that peak. Most of this of this will hold true to definition, but with a forced induction motor, valve lift is not as critical since the incoming air is pressurized. A good rule of thumb is to select a cam that will lift the valve 20-25% past its peak flow point. So be the definition above if your head flows best at 0.500" of lift, use a cam that will lift the valve between 0.600" and 0.625". The reasoning behind this is, if you lift the valve only to its peak flow point, then the valve only flows best when it's wide open. The cycle is brief and would only happen once per stroke. So to benefit from you peak flow the most, you want to lift the valve past its peak. That way the valve will pass its peak flow twice in the cycle. The result is more flow during the opening and closing event of the valve. You do not want to raise the valve much past the peak flow though, or you lose total flow by going too high. Calculating the best lift: 0.500 X 1.20 = 0.600 0.500 X 1.25 = .0625 Conclusion: There are way too many factors to just say XX cam will make XX power with your combo. Things like "114LS is best, or 117LS, or ..etc", are just blanket statements. Backpressure, RPM range, boost level, target horsepower, A/R of turbo, turbo frame (T3, T4, T6/Thumper), head flow, cubic inches, and even location of turbo...etc. All of these factors are extremely important in determining the cam that best suits your needs. There is no rule of thumb with a turbo cam. There are too many variables and the only way to get the right cam is to take all of those your parameters into consideration, and only then can a proper cam be selected. All of the points of reference above are just to get you on your way to building the best and most powerful turbo system for you. Study your design and ask questions along the way and you will be smiling the next time your opponent lines up next to you. Feel free to contact us for your needs. Also once you have read this and want to know the theory behind turbo charging, check out our advanced look at the engineering behind turbochargers. |
Re: Turbo Manifolds 2008
Originally Posted by slo_crx1
To add on to what Inquisition said about scavenging and preventing reversion in a log mani, cam overlap is a key factor in bumping up both of those. It helps promote scavenging by utilizing some of the forced air being pumped into the engine to help keep the exhaust moving quickly, and at the same time obviously prevents reversion. The only big losses are a drop in boost pressure (very slightly and can be made up for with a boost controller) and a slight drop in bottom end power and slightly later spool time.
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