It’s been a hectic day. My guy final called me back and told me that he has the Solidworks software but doesn’t use it. The software that he uses may have a different format and may not crossover to Solidworks or if it did the image may not come out right.
I took another look at the Mitech today. It looked like the same thickness that I’m using, which is ¼”. The cast runners will save some weight. It looks like his runners are probably 3”. I have tried different length runners on my design and I choose 2” for 2 reasons:
a. It gives me a larger plenum but on the down side it makes it a little bit heavier. You will be surprise, for every ½” in runner height it reduces the plenum volume quite a bit. The bottom of the Mitech is more v shape.
b. As a general rule of thumb, the shorter the runner length, the more high end power verses longer runners for low to mid end power. My goal of course is to hit the high traps. Since the motor has a lot of low to mid end grunt, I am focusing on the top end.
I don’t know if a minimal 5% difference in the runners oval vs. transitional or a donut vs. trumpet or shorter vs. longer runners or small vs. larger plenum all washes out in the end.
Its been a long day and right now the brain is dead. I will take up discussion later this evening.
Your take?
Couple things. First off, the Mitech intake was designed to work with a very high revving engine, so I am sure the runner lengths are probably appropriate. According to Mike, the runners are 3.75 inches long + .75 for the trumpet. He said he wishes they were longer, but its all he can do while maintaining good flow (and once again this was designed for high revving engines). From a port shape, he had lots of justification for the oval. The oval is what is being used in Prostock engines and he said no circle can outflow an oval. He gave me a fairly in depth explanation as to the testing that led to this conclusion, but the point is that an oval shape is best.
As far as your CAD guys programs...most likely he can export a common file, like a Parasolid, .stl ect...
I was reading some different literatures a while back that supported both the short runner and medium size runner depending on several variables in depth. They each supported their side. It left me confused as to which concept is the best. I spoke to several people that have been around the race industry and majority of them point in the direction of the short runner based on their personal experience. Granted that these people probably don’t have Phd but they obtained their experience through testing and tuning or being involved in a race team, etc. I have been in the race scene for a long time with my personal cars. I have had friends with the same setup except for few equipment differences. It surprised the hell out of me when the piece of crapy, low budget, hand-made, modified, etc. equipment actually made good power on the dyno. It may be a cop out excuse but man, I’m going to give my design a try.
Currently, I am using ¼” thickness. It’s not that much more weight and its easy to shave off if needed. The reasons I chose ¼” are: a) it gives it rigidity especially on top piece from flexing under pressure putting stress on the bolts. b) from a track car only stand point, the pro is that a thicker material takes longer to heat soak but the con is that it takes longer to dissipate. I can make more runs with less worries about getting the manifold hot due to the thickness. Now if it gets machined down to a thinner 1/8”, how long would it take to heat up or cool down before it affects performance levels if all the variable are the same. On a street car, you would definitely want a thin material.
Currently, I am using ¼” thickness. It’s not that much more weight and its easy to shave off if needed. The reasons I chose ¼” are: a) it gives it rigidity especially on top piece from flexing under pressure putting stress on the bolts. b) from a track car only stand point, the pro is that a thicker material takes longer to heat soak but the con is that it takes longer to dissipate. I can make more runs with less worries about getting the manifold hot due to the thickness. Now if it gets machined down to a thinner 1/8”, how long would it take to heat up or cool down before it affects performance levels if all the variable are the same. On a street car, you would definitely want a thin material.
You don't understand bending moments very well do you?
Here's a little bit of info... 1/8" material with a 1/4" thick, 1/2" wide rail welded to the top is IMMENSELY stronger than a flat sheet of 1/4"... and a lot lighter too.
Have you put any thought into just how much pressure the walls and top of this thing will see under boots? The rear wall section could easily have 1000+ pounds of force trying to move it. Who really would pick 1/4" aluminum to support that kind of load, with no supporting structure?
Also, if you're trying to make the claim that using a lot more material, thus more weight, will prevent it from heat soaking then you know even less than I first suspected. There are coatings that fix this problem, making it heavier is not the correct approach.
40lbs is a considerable amount of weight to have sitting there, when the other option is closer to 10.
I'm rather appalled a physician could be so myopic, thats a scary thought at best.
Doc, good to see you forging ahead with your intake build.
Here are some runner lengths using different harmonics for a 6000 rpm peak. The 3rd harmonic is most commonly used when possible. It makes more torque, but you won't be able to use it on your design. The fourth harmonic is used on single 4 manifolds.
3rd harmonic - 13.8"
4th harmonic - 10.8"
5th harmonic - 8.7"
Sorry to see you get picked on so much. There's no reason for people to be speaking down to you. The important thing here is that you're learning how to build a billet intake. The first one might very well need some improvements after it's finished. So what? The second one will be better. I know my first set of ported heads was not the best, but we all have to start somewhere.
I would rather see you used an oval top than a flat one.
I don't mind critism at all as long as it is + vs. -. I am looking for feed back with reason behind it. I have learn through 8 yrs of running my 4 clinics with x employees that I have to be able to take critism from employees. We have monthly meeting on how to better our service and I take their suggestions. I used to be real bull headed but in the end, I go home all stressed out. I just learn through the years that it is not worth the aggravation and fight. These days I look forward to positive critism with feed back on how to make it better vs. critism with no feedback at all.
If the cast runner is 3" long, then you'd only need about a 1.5" addition to make it work with the 4th harmonic.
The intake port on the head is *about* 6.4".
Bill...back off the insults already . This manifold will be a little heavier than a sheet metal version, but not by much, and certainly within the realm of a factory cast unit. I'd personally like to see him do this. There are already top tier CNC guys doing billet manifolds for Ford GT's. Are those junk too?
If the cast runner is 3" long, then you'd only need about a 1.5" addition to make it work with the 4th harmonic.
The intake port on the head is *about* 6.4".
Bill...back off the insults already . This manifold will be a little heavier than a sheet metal version, but not by much, and certainly within the realm of a factory cast unit. I'd personally like to see him do this. There are already top tier CNC guys doing billet manifolds for Ford GT's. Are those junk too?
Agreed, anything intelligent DB has to say loses all importance when he starts cyber strutting.
If the cast runner is 3" long, then you'd only need about a 1.5" addition to make it work with the 4th harmonic.
The intake port on the head is *about* 6.4".
Bill...back off the insults already . This manifold will be a little heavier than a sheet metal version, but not by much, and certainly within the realm of a factory cast unit. I'd personally like to see him do this. There are already top tier CNC guys doing billet manifolds for Ford GT's. Are those junk too?
According to Mike, the runners are 3.75 inches long + .75 for the trumpet. That puts it right at the 4th harmonic.
Yeah... and a 5oz tack hammer has a striking resemblance to a 20lb sledge... and thats about as close of a comparison as his disaster is to a GTS-R intake.
Won't the 'trumpets' at the back of the intake manifold improve if they are directed at the front? Even if at an angle? I've seen in car mags the BMW v-10 engine with various length trumpets measured to capture a better segment of air.
Won't the 'trumpets' at the back of the intake manifold improve if they are directed at the front? Even if at an angle? I've seen in car mags the BMW v-10 engine with various length trumpets measured to capture a better segment of air.
Thoughts?
Jay K.
That's an interesting question and one that I would have a really hard time predicting without doing some CFD. There could be some gains, due to "ram air," which is effectively velocity turned into pressure at the stagnation point. However, it would be hard to keep the same runner length as the others and the change in direction could reduce flow in the runner. I know the BMW engines I have seen have the trumpets all directed in different directions, therefore making them all the same length. The BMW runners also weren't as cramped and had more room for flow, so the big trumpets weren't interfering, per se. I am sure that resulted from an analysis so that they would all have the most similar pressure to pull from.
On another note, Lee's manifold on his car looks pretty good, although it requires a big hood.
Not the pics I was envisioning, but pretty pics none-the-less.
No, not at all... if you can't see that having a manifold with 10t/b's in there and the stacks for a purpose, vs his setup are vastly different, then you're a lost cause.
Hence my hammer analogy. Sure, they kinda look the same, but are pretty much complete opposites.
Won't the 'trumpets' at the back of the intake manifold improve if they are directed at the front? Even if at an angle? I've seen in car mags the BMW v-10 engine with various length trumpets measured to capture a better segment of air.
Thoughts?
Jay K.
It can't hurt. I was at the Ferrari dealership the other day in their engine assembly room and they were disassembling a 430 engine for a rebuild that is run in the Challenge. The runners extend up into the plenum several inches and have about a ten degree cant on them towards the front of the intake. Ferrari engineers are hardly a group of guys to build a junk manifold.
One thing you have to keep in mind about manifolds is that they do not flow "steady state". The flow is not exactly starting and stopping, but the intensity of flow does increase and decrease a bit. A steady state flow test on a flow bench does not tell the whole story about a manifold. It must be run at the track. I prefer to have a longer runner that uses the 3rd harmonic because the runner will hold more air and will not have a strong need to draw a lot of air from the plenum during the intake stroke. The shorter runner manifolds that rely on the 4th harmonic are more dependant on how quickly air can flow from the plenum into the runner and need to flow at a higher rate, because there is not enough air in the runner to completely fill the cylinder on the intake stroke and air must be drawn from the plenum. Same situation as a single four barrel manifold.
That's an interesting question and one that I would have a really hard time predicting without doing some CFD. There could be some gains, due to "ram air," which is effectively velocity turned into pressure at the stagnation point.
I'm sorry but you're going to have to list some sort of credentials on this "CFD" analysis you're about to pull.
