Which Air Horn Shape would be better

[TimZ]

Hey Monzter that intake looks real good, almost like you cut up a stock intake...He, he.

 

It's much more than that - Those look to be TWM ITBs integrated into somebody's manifold design (can't tell which offhand - Canon, maybe?). Jeff - did you fab those, or did TWM make a custom casting, or what? That's really nice.

 

Those Wiggins clamps are really nice, and should make assembly/disassembly much easier, too. I looked into using those on my last buildup, but didn't have the cash to outlay at the time.

 

That's just a beautiful layout all around - can't wait to see how it runs!

 

On the original question - I was thinking packaging would be the main determining factor for square vs. round, also. Depending on what your plenum design looks like, the square horns might work out better, and if that's the case, I wouldn't be afraid to use them.

 

Actually, now that I'm thinking about it, there might be a pretty good case for using the square horns. I haven't yet seen your plenum design, but I'll make the ASSumption that it's the "normal" asymmetrical log-style with the inlet at the front. Since the air is going to have to make the transition from the shape of the inside of the plenum into the horn anyway, the square horn should at the same time give you a greater area to draw from, and will allow you to have much better control over how the transition from the (probably squarish) shape of the plenum to the round shape of the runner takes place.

[brokebolt]

Sence you mention it, the plenum being at 90 degrees from the inlet to the individual runners, would that cause some blow over (not sure if that is a technical term)? But the question is as the air flows into the plenum would you have negative things happen to the air as it flows over the first, second, thrid intake runners and so on as it travels to the sixth runner. The original SU air cleaner put little side skirts on each side of the intake horns, I am assuming to prevent this...maybe it was just to hold the air cleaner in place?

 

So with that said would their be any logical reason to experiemnt with an air horn that was round on the trailing edge and square on the leading edge? Just building off the ideas TimZ shared.

 

The intake shown looks too long to me to be a Cannon and the intakes are curved, were as the Cannon I have is straight. Origiannly it looked to me that a stocker was cut up and the runners were re-organized as 1-4-5-2-3-6...than some fancy welding to make the standard side draft mounting surface either by cutting off the flanges on a stock Cannon (or other brand) or having some mounting surfaces fabed up as blanks like the headers were and welding them on. It is an interesting quiry.

 

Either way it looks cool and original.

[Tony D]

The blowover issue assumes that the turbo blows from the pipe directly into the plenum like a stock manifold.

HKS and SK turbo plenums for Carbs used a shrouded entry with the plenum being pressurized through openings between cylinders 2&3, as well as 4&5.... in some cases they put a diffuser baffle into the plenum to further interrupt the velocity and turn it into pressure more evenly throughout the box. SK went so far as to shroud the plenum into two compartments using a baffle the entire length of the plenum, allowing air to enter only at the top and bottom of the plenum.

 

The original HKS Box (Type 1) used a similar setup, letting a prechamber diffuse the incoming air to pressure, then putting it into an upper chamber before letting it blow from the top of the plenum down between the aforementioned cylinders. The key is to diffuse the velocity of the air coming from the tubing entering the plenum into a pressure situation. Normally people 'diffuse' it by expanding the area...dumping into an open plenum. If you instead use a baffle to stop that velocity you see an increased on-boost characteristic (boost seems to come on harder) as opposed to simply letting it diffuse into an open chamber (similar to what happens in the turbo's torus ring around the compressor wheel, velocity slows, pressure builds...)

 

As for bar-and-plate it is a design that looks similar to the intercoolers sold for years. Those would be considered 'tube and fin' style normally. Bar & plate coolers offer superior heat transfer in a more compact size than conventional tube & fin or shell & tube coolers. Generally the bar and plate coolers have turbulators in the 'bar' portions to maximize air to air heat transfer. Instead of having smaller tubes (think three core radiator) the tube is across the entire thickness of the core with those turbulators in it.

These links should show some of the differences (I hope.)

 

 

http://www.airradiators.com.au/?id=87

[MONZTER]

Tim was correct, The throttles were made from pieces starting with a set of TWM 46mm bodies and intake. The flange was cut off the intake runners and then the runners were seperated and machined at 20 degrees to improve the entry of the runner into the head as well as increase the distance from the header to the bottom of the bodies (less heat). I made the flanges to be 4 bolt instead of 6 bolt for the purpose of adding a second set of injectors in the flanges pointing right at the back of the valves. The parts were all welded up and then smoother out to look like cast again. I added a bunch of material to the inside radius of the runners to smooth them out as well as giving more material to straighten out the inside of the runner. The path is much straighter than it looks from the outside. The flange mounted injector bosses are not welded in yet, they will be smoother in as well. Here are some pics of the process.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sorry if there are too many pictures.

 

Jeff

[MONZTER]

So I modeled up a quick plenum to see how the shape of the horn would interact with the shape of the plenum. The shape is no where final, just to show the ideas. I am thinking the square ones are looking smoother and more streamlined (less flat bottom) What are you guys thoughts? I just started doing research into the plenum shape and volume. Do you guys have any link suggestions for good reading on the subject? I have read all I can find on the forum here. Good stuff

 

Thanks Jeff

 

 

 

 

 

 

 

[Tony D]

One picture too many...I see Devcon! LOL

 

Jenvey made a nice ITB setup that was available in thickness from 109mm (stock Weber width, front to back) down to I believe 30mm wide...though welding those in would likely have distorted the bores on the throttle shaft.

 

Niiice!

[MONZTER]

Devcon - Not on the intakes, I'll weld before that, but to fill the port floors in with the raised intake ports yes. Its actually Manley 2 part epoxy material specifically for the job (probably made by Devcon) TWM also used to make thin CNC throttles like only 20mm wide, but I had these already and one set of injectors far back were already there.

[Tony D]

I'm a big fan of Devcon Aluminum Putty. Machines and takes threads really well. And is a heluva lot easier to slurry into places where I can never get my TIG!

 

The only problem is I have to make damned sure I have all the welding done on whatever BEFORE I put it in there. I've had a few 'DOH' moments since starting to use it. I really like it for intakes and T/B alterations.

 

Makes nice machinable plugs for casting as well (or for altering existing castings for taking molds from!)

 

Point of Historical Interest: Never use Devcon Titanium Putty on anything you think you will be taking a carbide die grinder bit to later on...the Devcon will win! You wouldn't think 'plastic' would make a carbide bit throw sparks....but it will! (Bad Day...really bad day!)

[brokebolt]

Tony D.,

Thanks for the info and the link. Great stuff.

 

TimZ,

Good call on the TB runner 'cut and paste' job that Monzter did.

 

Monzter,

Never too many pics. Great way to document your project...how many hours spend on machining/welding of the TB runners...or do you not want to add them up?

 

On the plunum idea, I look toward the Pro Drag race guys for inspiration. By simply adding a half donut shape over the port that may produce a smoother transition into the throat of the TB, or I would think. Extruda body (advertised on this site) has a video on his my space page that demonstrates the effect and the half donut shape very well. It really is odd that something so simple in shape would generate that much more flow...but really I guess it is no more than a TWM air horn without the inlet tube.

 

Post more pics as you finish more items in the project. This is definately a project I would like to closely follow. Might make a good multi-step article for Nissan Sport Z mag...