Definitely the best thread ever! Thanks for all of your hard work, effort and honesty in the outcome.

 

Wow, thanks Dave for the hard work!

Keep it up!

 

Is it possible the reason you only lost power with the intakes is because they are common to lose power on the low end and don't start actually making power until around 5,500 or higher? With the stock turbo in place, the car just wasn't making enough power to keep making more and more after 5,500? Is it just the turbo was too small and couldn't push air fast enough? I am curious because I am getting ready to buy a manifold from you guys Hopefully you can get the sheetmetal on a car with a bigger turbo and see if it starts shining then.

 

In my job I calculate flow capacity pretty much every day. The basic theory is very simple. You apply a resistance factor for every feature the fluid encounters.

features constitute a change in flow area (ie diameter) or shape (round to square), or a change in flow direction (bend or elbow. A flow direction factor can be a front inlet and left hand outlet and the factor is relative to the angle of the change.

Interestingly a drop in flow efficiency occurs for any change in the flow area (diameter) whether going from big to small or the other way around. When going from small to big, turbulence from the transition intrudes on the main flow stream acting like a restriction.

I use a very expensive software program to confirm mathcad calculations of complicated fluid problems. This software is generically labeled computational fluid dynamics and it breaks down a fluid scenario into hundreds of thousands of tiny mathematical calculations and sums them all together. The output is some really cool looking graphics that show velocity concentrations and fluid vectors (discreet fluid directions) that are a big help in iterative design of flow features. I know CFD is being used by most of the deep pocket companies as a design tool but there's a problem applying it to combustion engine related components. The fluid velocity to and from engines pulses. A lot. So time has to be added into the equation.

Fluid pulsing is why increasing the volume of your airbox or muffler, with no other change, increases horsepower. Increasing airbox volume gives the engine a large reservoir so even though the average velocity in the plenum is the same, the peaks of pressure are smoothed out. I've designed quite a few mufflers and I always make them single chamber and as big as is reasonably possible.

The tricky part now is the transition from the runners to the chamber. This is where the sheet metal intake I think falls down. Looking at the pictures there seems to be sharp transitions from the runners to the chamber which would cause pressure drop at the transition. In contrast, take a look at the old school edelbrock victor junior intake runners and plenum. This to me is one of the most refined devices for providing smooth transition from a central chamber to individual runners, with a 90 degree turn from the inlet, in a short distance. In my world this is a beautifully elegant design.

 

Great explanation.. Its probably the first post I've seen that clearly explains why bigger isn't better, but matching the application does a better job of it.

If some of you have been reading, you hear about intake manifolds having "surge tanks" you also notice the really well designed ones have compound curves and carefully blended transitions. This is also why I believe an extrudehoned intake manifold will do better in most applications than a sheet metal one. The surge tank portion of it may be smaller, but since it was honed using a "liquid" the restrictions are being knocked down.

Transitions cause turbulence, which in turn restricts flow, at lower RPM the pulsing amplifies this disruption of flow therefore it hurts the ability of the engine to get air into it. A larger surge tank means more reserve volume "waiting" for the next intake stroke, but without smooth blending and transition.. Look at it this way.. if your waiting on line to get into a building that has one large door, if everyone enters from lines, in an organized manner, 10 people at a time, all 10 should be able to run through the door when they say go.. If you have a mob scene where there are no lines, everyone piles up against the door, so no matter how many people are waiting at the door, it will be nearly impossible to get 10 running through the door at the same speed since their trying to fight their way through traffic. Make sense? The volume may be higher, but your neighbors are preventing you from getting through the door. THIS is why engineering a component is so important.

 

Okay in order to round out the equations you have to include momentum and resonance of the fluid charge. This makes it even tougher to design flow features for engine components and is the basis for many of the bolt on performance mods like 4:1 tuned headers and cold air intakes. If your resonance is out of whack an otherwise perfectly designed component will create a power loss. It's no wonder with all these interacting variables that tuning is still somewhat of a black art. What then is the recipe for success? Really simple: Developmental testing and only try stuff that works. Okay maybe that's better described as simplistic but I think it's still true. In order to improve your testing success percentage for a scenario of almost infinite variation of parameters requires feel.

When I'm confident with the cause and effect of changes to a particular product I call it having a "feel" for it. This for me is an understanding of the end effect of changing a certain variable, in conjunction with other varibles, that's impossible to convey in words.

Most of the "guru's" in a particular industry are people with good feel but it's very rare that they would have the courage to put their inventions in such a harsh light as what Dave is doing here. This is the imbodiment of the word character and worthy of a man's respect.

 

I have a basic understanding of that. I am trying to figure out how much airflow will make a sheetmetal intake a decent increase in power at high RPM. If I lose 10hp throughout the RPM band and only gain 5 up top I would be pissed. However if I lose around 5-10 until 5k and it pulls harder and harder up top giving a 10-25 HP gain up top it is worth it. I understand with a small turbo like our stock I will most likely not gain enough to make it close to worth it if any at all. But with a larger turbo like a GT30 series or bigger how much power will I gain? Thats the true question, we could thearize and profisize all night but in real life I wanna know my results

 

Let me be more direct, I don't think the sheet metal intake will ever make more power than the extrude honed and port matched intake. Unless of course your cylinder head intake ports and intake valves are increased significantly in size, and the sheet metal intake runners are then fabricated of similar cross sectional area to be port matched. I think this is the only real advantage to a fabricated intake of this type: it can be easily customized to match your cylinder head port size. Flaring the end of an intake with smaller ports doesn't cut it. But without smooth contours it will never make as much horsepower as an intake that does have smooth contours.

Any change in cross sectional area is a transition. Any transition in area has to be carefully contoured or you lose flow attachment. If you lose flow attachment you get turbulence that interferes with flow. This is not theory it's a rule and like all engineering rules it has been well documented with testing. Anyone in this business has a flow lab to test such things (we've got a huge one) and this is an old rule.
Casting patterns are pretty cheap in China/India these days.

 

Food for thought:

http://nabr.jayntguru.com/shootout/

 

good stuff, I liked the graph of the BJ's mani

 

20G test soon I hope?? Great work!!!!!!!

 

I have sheetmetal intakes here on the shelf that I would love to sell. I have posted the results knowing full well that they could hurt sales of some parts. That doesn't make me happy but such is the life of honesty.

Want a sheetmetal? I will sell them "on sale", as I realize that in the past on the 4g63's they have made a difference, when tested with larger turbos. I don't know if that is going to be the case in this instance. You want one, please call us and we'll make you a screaming deal on it. The ones I have are set of for the stock TB or ported TB. I can change the flange if you want to go to a 3" TB too.

The 20G is on the car and the car is having the injectors changed over to 680's right now. The stock injectors at 382 whp on pump gas were in the 95% range so it was time to change them. On a side note on race gas there would be injector left as I wouldn't have to run the car as rich. Right now the car is 11.3-11.4 range, on race gas I could loose some duty cycle by running them at 12.0:1 very safely.

David Buschur
www.buschurracing.com

 

Awsome, think it will be dyno'd with teh 20g today?

 

 

[QUOTE=davidbuschur]I have sheetmetal intakes here on the shelf that I would love to sell. I have posted the results knowing full well that they could hurt sales of some parts. That doesn't make me happy but such is the life of honesty.



Damn. Sorry Dave. From now on I'll keep my opinions to myself. I definitely don't want to hurt your business. I do have a new air filter I'm testing now that I'd be willing to pass on to you if your interested. Up to you if you'd want to do anything with it. I made it from readily available commercial components. I built it after seeing grit on the inside of my HKS RS intake. That yellow mushroom filter doesn't actually filter dirt worth a damn. K&N type doesn't flow quite as well as the yellow foam but does work as a filter. The one I've got on there now is inexpensive and filters down to the micron level in three layered stages. I'm getting the exact same A/F ratios as the yellow foamy filter. About plus 9% fuel over the stock air box at lower revs. Plus 5% at redline. It doesn't look as good as the bright yellow filter of course. I'm using lots of filtration surface area. The way I've got it set up (crude) it looks like one of those dogs that has too much skin but it's simple, cheap, and sure works good. It is quieter than the yellow foam but you can still hear the turbo spool faintly and the bov vent.