Hey guys, I am working on a protype 2 piece billet intake manifold for a single throttle body. This is a pet car project of mine that is going to take some time to finish from beginning to end. I will be using a 105 mm tb. The manifold will be finished shortly. I just haven't decided if the top piece is going to be oval or flat. The billet aluminum will start off as ~300lbs and will be cnc down to ~ 40lbs. Here are some pics.
My design allows for different length velocity stacks that screw on. The stacks that I will be using will actually sit on the floor of the plenum for turbo applications. With different velocity stack lengths that are interchangeable, one can tune a N/A car for hp and torque at specific rpm levels. It also helps the head porter so that he can easily take the stacks off and port match the runners with the heads. Unlike other company designs, the outside runners start out as oval to match the heads and flare out to a much larger round design that attach to the plenum to create a funnel effect for the air to travel into the cylinder heads. IMO my runner design works better than a straight oval or straight round design but that is only my oppinion. Actually I talked this over with a couple of fluid and thermal dynamic engineers. As far as I know, I'm the only one with a billet design- no welds here buddy. Everyone else uses welded sheet metal. It took my machinest 3 days to do the bottom piece. He said it would take another 1 or so to do the top piece. I wanted to get manifolds from other companies but they told me it would take 6-8 weeks at least. For me to make a replica it would only take less than one week in the cnc machine. And as long as I have the base program, I can make changes on the fly. If I wanted to I can design my fuel rails as part of my top piece cover and when the cover bolts down, it will also be bolting down the rails as well. This is my little pet project. Everything is based on theory but I am going to give it a try. I'm looking to do some R&D against a stock manifold and just see how it goes. It is ~3x the volume as the stock one and by using a 105 mm tb with 5" intake piping, it should flow alot of air through the top mount 91 mm turbos sitting on top of the hood.
My design allows for different length velocity stacks that screw on. The stacks that I will be using will actually sit on the floor of the plenum for turbo applications. With different velocity stack lengths that are interchangeable, one can tune a N/A car for hp and torque at specific rpm levels. It also helps the head porter so that he can easily take the stacks off and port match the runners with the heads. Unlike other company designs, the outside runners start out as oval to match the heads and flare out to a much larger round design that attach to the plenum to create a funnel effect for the air to travel into the cylinder heads. IMO my runner design works better than a straight oval or straight round design but that is only my oppinion. Actually I talked this over with a couple of fluid and thermal dynamic engineers. As far as I know, I'm the only one with a billet design- no welds here buddy. Everyone else uses welded sheet metal. It took my machinest 3 days to do the bottom piece. He said it would take another 1 or so to do the top piece. I wanted to get manifolds from other companies but they told me it would take 6-8 weeks at least. For me to make a replica it would only take less than one week in the cnc machine. And as long as I have the base program, I can make changes on the fly. If I wanted to I can design my fuel rails as part of my top piece cover and when the cover bolts down, it will also be bolting down the rails as well. This is my little pet project. Everything is based on theory but I am going to give it a try. I'm looking to do some R&D against a stock manifold and just see how it goes. It is ~3x the volume as the stock one and by using a 105 mm tb with 5" intake piping, it should flow alot of air through the top mount 91 mm turbos sitting on top of the hood.
While screw in runners may be very nice for NA applications, you really do need to watch. I very strongly predict that given the limited height in a Viper application, you are going to see a lot of flow reducing turbulence caused by the trumpets sticking out like they do. This will of course cause uneven air to fuel. Only making it and testing it will bear this out, but if I were you, I would have individual O2 or EGT's in every runner for testing. However, it is nice to see a plenum for NA performance. I know that's Mitech's is a turbo specific plenum, although it would work well for high revving NA as well.
As far as funneling air down into the engine, I think you will find this to yield little or no improvement...quite possible detrimental effects actually. Causing the air to change shape, and more importantly volume when at a high reynolds number will most likely cause a choking in the throat which will cause the flow to back up and become more turbulent. This will reduce flow and cause the air to heat up more. When given the opportunity, it is generally best to keep your pipe in a short runner the same cross sectional shape as long as the material is super smooth (which it should be). Fluid dynamics are hard to predict and unless your engineers ran CFD, the only way to know for sure is to test it. It sounds like you are going to do just that.
I like the billet idea, I just think it is gonna cost a metic ass ton and end up eating bits and wasting a huge amount of material. However, if you have access to it and have good recycling programs in place, go for it.
Good luck. I anxiously await the results. You should CNC a straight runner and flow bench them both. It would be easy to do and take away the guessing.
The runners are very short 2” in length and expand from oval to round rather quickly and most likely would not change the air flow characteristics very much. If you look at the intake manifold for exotic engine development – exoticengine.net, the are using the same principle/philosphy with their runners although I’m not sure how long they are. I made my runners as short as they will be in order for the bolt to go through. Either that or use studs with lock washers. My project cost me less than what those guys are charging for aluminum sheets and furthermore, I have complete control over what specifications I want done. Long weekly conversations with the engineers that I spoke to gave me good advice according to different theories and formulas but actual testing is a different story. You can bend aluminum sheet but can mold it. Machining aluminum is so much softer and does not require going through tons of bits like stainless, mild steel, etc. The bottom piece used up 2 bits.
I am looking at making an efficient manifold. If a sheet metal manifold makes 1000hp at 10psi, I am hoping that my design makes 1000hp at 7psi on the same turbo system.
I am looking at making an efficient manifold. If a sheet metal manifold makes 1000hp at 10psi, I am hoping that my design makes 1000hp at 7psi on the same turbo system.
That's extremely unlikely. You might knock half a psi off of one, but 3 psi? You are nuts if you think you are going to improve overall system performance by 30%.
I am glad some guys out there have the means and interest to try this stuff out. Would be cool if there were a way to compare independently between your and others.
The for any application, whether turbo or n/a, the cylinders in the back normally get less air anyways. Granted that the velocity stack can be as tall as 3” plus 2” for the runners for a total of 5”. Since the stock runners are way longer than 5” I would assume that air takes a bit longer to channel to the heads than with the shorter velocity stacks. I don’t see the rear cylinders starving for more air with the stacks verses the stock longer runners. Depends on what size tb you use of course that affects turbulence or velocity/speed in a larger plenum area. There are a lot of variables on a n/a motor as far as getting the right combination to work-- the right height stacks right size tb, the temp, etc. I won’t be testing any n/a applications especially tapping for 10 egts. N/a motors are not my cup of tea. However, I plan on getting a race pack instrument panel to record all egts for my turbo application to lean out or add more fuel to each individual cylinder as needed. Those plugs should come out the same color across the board. Just curious, I haven’t been around the big boys but from the pics that I see of their cars, I don’t see any individual egts. Are there some variations on each plug after each run.
The for any application, whether turbo or n/a, the cylinders in the back normally get less air anyways. Granted that the velocity stack can be as tall as 3” plus 2” for the runners for a total of 5”. Since the stock runners are way longer than 5” I would assume that air takes a bit longer to channel to the heads than with the shorter velocity stacks. I don’t see the rear cylinders starving for more air with the stacks verses the stock longer runners. Depends on what size tb you use of course that affects turbulence or velocity/speed in a larger plenum area. There are a lot of variables on a n/a motor as far as getting the right combination to work-- the right height stacks right size tb, the temp, etc. I won’t be testing any n/a applications especially tapping for 10 egts. N/a motors are not my cup of tea. However, I plan on getting a race pack instrument panel to record all egts for my turbo application to lean out or add more fuel to each individual cylinder as needed. Those plugs should come out the same color across the board. Just curious, I haven’t been around the big boys but from the pics that I see of their cars, I don’t see any individual egts. Are there some variations on each plug after each run.
The difference between the stock manifold is that it doesn't have anything obstructing the airflow, whereas your's does. The ROE superchargers have big problems with running certain cylinders lean. The factory manifolds run the back cylinders a little rich, but it is pretty minor. Because your intake introduces a new variable, that is why I am advising you to be very careful to note EGTs or AF across the board. Perhaps running an EGT in the back runner and one in the front of a single bank would give a good indication without breaking the bank.
Last edited by The Former PFR : May 14th, 2008 at 12:07 AM.
I am looking at making an efficient manifold. If a sheet metal manifold makes 1000hp at 10psi, I am hoping that my design makes 1000hp at 7psi on the same turbo system.
You're delusional. Beyond that, a full cnc manifold has a long list of issues that you haven't given any thought to.
First being weight. You're going to be 4x the weight of a good sheetmetal setup, and cost totally out of orbit as well. It may look pretty if you did it right, but you're not exactly going that direction either.
What is your internal plenum volume? Looks pretty small which is exactly what you don't want.
When you're forcing air into the motor the velocity stack effect isn't needed, and in this case will only disrupt airflow and eat plenum volume. See the small bells on the runners of the mitech manifold... yeah.
Have you given any thought to throttle tip-in characteristics/drivability with a single 4" throttle body?
The short transition from round to oval isn't providing any flow/velocity benefit and only making it a motherfucker to get the bolts in to attach it to the head.
Who exactly is going to tap a 2" dia (estimated) hole 1/4" deep to screw these stacks on? Good luck with that.
I don't see any O-ring channels anywhere, were you planning on doing all this and running some lame gaskets?
You need to make the sealing surfaces much larger to have any chance of it holding pressure. You're vastly underestimating the total force applied inside the manifold.
How are you attaching the fuel rails? Doesn't look like you'll even have clearance for the injectors. Did you put any thought into the angle of the injector into the port?
What heads is it cut for? stock, stryker, ported, etc?
I don't see any ports for pressure/vac signals?
What series AL? Were you going to cut already heat treated material, or cut it first then heat treat?
My $$ says you'll make less average HP than a good ported stock manifold, and have major sealing issues on the back of the manifold and/or throttle body mount. IF you can even get it bolted in place.
The for any application, whether turbo or n/a, the cylinders in the back normally get less air anyways. Granted that the velocity stack can be as tall as 3” plus 2” for the runners for a total of 5”. Since the stock runners are way longer than 5” I would assume that air takes a bit longer to channel to the heads than with the shorter velocity stacks. I don’t see the rear cylinders starving for more air with the stacks verses the stock longer runners. Depends on what size tb you use of course that affects turbulence or velocity/speed in a larger plenum area. There are a lot of variables on a n/a motor as far as getting the right combination to work-- the right height stacks right size tb, the temp, etc. I won’t be testing any n/a applications especially tapping for 10 egts. N/a motors are not my cup of tea. However, I plan on getting a race pack instrument panel to record all egts for my turbo application to lean out or add more fuel to each individual cylinder as needed. Those plugs should come out the same color across the board. Just curious, I haven’t been around the big boys but from the pics that I see of their cars, I don’t see any individual egts. Are there some variations on each plug after each run.
LOOKS GREAT!!!! YOU KNOW WHAT YOU ARE DOING. IT IS ONLY MONEY!!!!!
These are not update pics. These are just random pics that I posted up that are not completed. The manifold does weigh more than the stock porus cast ones. If you look inside the stock one, the plenum volume is very small and it is mostly runner length. With 2” short runners, the floor of the plenum sits low thus allowing a bigger plenum. If you read my above post, my turbo application will actually have the stacks sitting on the floor of the plenum which is where it belongs. I have already taken into account the sealing issues, vacuum ports,etc. The manifold fits gen I-III. People have bolted on a gen III on a gen II before. It’s the same bolt pattern. This is a track car only so I am looking for the biggest tb I can get. If you read my earlier post, the bolt has already been taken into account when putting the manifold on. The cnc machine as already tapped and threaded the opening on the runner and stack for easy screw on. The machine does it all with programmed commands. If you call up any alloy company, with a thick aluminum block of 4” thick for the bottom part, the aluminum only comes in 5052 grade. The company sells treated AL and it is certified. But for my purposes, I wished they had non treated AL if it is cheaper because it does not matter. The o-ring design is actually incorporated on the top piece. The fuel rails have a screw that goes through the bottom of it and actually attaches to the top piece. I try not the put to many add ons to the bottom piece because it is expensive if you mess up on it. I rather mess up a smaller less expensive top piece of aluminum than try to put all the fancy features on the big piece and end up messing it up. The injectors stand vertical. Sometimes it is hard to tell on clearance issues on a pic but on a cnc machine, it is dead accurate on measurements. We’ll just see how it all works out and what the issues are..
