shearer by far

 

i heard but he wants like what 7-10 people to sign up and commit first at a 1000 a pop thats crazy but if you want to then more power to you. LOL im thinking about getting one done but i still dont see the point in a DD FF unless you going for the OH Cool Factor other then that not worth it for DD. if Drag Car then im all for it

 

I really need to update the OP of this thread...this thread has been seeing a lot of action lately...especially with all the new tubular manifolds coming out lately...

 

I agree, what's the point. The whole purpose of building a tubular stock replacement manifold is to retain the stock location so that the owner would not have to purchase a different O2 housing, downpipe, turbo, etc., just to be able to run a tubular manifold. But i guess if there's enough demand for something, some one will build it.

MrC

 

that turbo is on my list as well...however, as i keep reading in this thread you can expect about 300rpm loss in spool...I just really don't know if I want that...or can justify paying $800+ to gain 15HP over stock ported...not exactly good power to $$$ ratio...the tubular manifolds sure do look nice though...maybe once you have everything else done with the car and can't think of anything else to do thats when you get a tubular manifold...

 

Really you think so? 300rpm loss? Well isn't tubular headers suppose to increase flow more smoothly? And as I read from the thread about that new hks turbo kit (HKS GT2 7460) done by Sean Ivey that particular turbo spools faster then the factory unit and at lower rpms. (correct me if I'm wrong) And the the full race header is suppose to have an increase in hp in low-to mid HP range correct? And the shearer gives more of the peak HP range. Correct me if I am wrong maybe I wasted 20 mins yesterday.

 

There will be some loss in spool due to the volume of the manifold. The really short runner manifolds may have very minimal spool loss, but the short runners make it impossible to build an optimized collector.

 

The longer runners with higher volume smooth out and reduce the peak pulse energy at the turbine wheel, this is where the loss of spool is likely coming from. That is likely where the HP gains are too though, less peak exhaust back pressure on blow-down. Kind of a double edged sword.

I'm running a 1-1/2" (pipe) tubular manifold with ~17" runner lengths. Most of the others out there seem to be 11"-14" runners and most are using 1-1/4" pipe. My car holds HP pretty well out to 7500 even on the stock IX turbo. It is more "laggy" then a ported stocker, although, I wouldn't really call it laggy.

It seems more like it takes away a bit of the "hit" when boost comes on but I don't really find myself waiting for the turbo to spool ever. It makes power delivery more linear, which is something I would rather have then that hard hit of torque that tends to upset the chassis under corner exit.

I think if I build another manifold though, I'll be using stepped primaries in the 18"-20" length range.

 

I was just thinking about stepped runners yesterday. Somewhat interesting that it hasn't been done yet in a commercial product for the Evo.

 

Yeah, there is a Honda company that does them. 1-1/4" pipe to 1-1/2" pipe.

 

Interesting. I would go from 1.5" to 1.25".

 

Which direction reference?

head -> small -> large -> collector

That is a "traditional" stepped header. The idea being that the smaller diameter keeps exhaust velocity high out of the head to promote scavenging, then it steps out to larger tubing to reduce pressure losses as the pulse slows down.

 

stepped primaries has always been interesting to me. In my opinion ive not seen it done "properly" to the extent that it could make much difference as the effect is capable of? I know many NA applications swear by it, but everyone who fabricates these uses an abrupt transition, not a smooth conical transition. I have never seen benefit on a turbo engine from stepped runners, but am interested to know what others have found. Keep in mind an abrupt step does have an increased pressure drop associated with it - No free lunch

my understanding on the topic is courtesy of an expert aerodynamicist who writes for Racecar Engineering -- the 'Coanda Effect' sees a 'jet' with additional energy prefer to have the flow stay attached to a surface that curves or angles away from where the jet emerges and pressure reduction can result. Try this: hold a piece of paper lightly between fingers and thumbs under your bottom lip so that it is horizontal near your mouth and curves down under its own weight. Now blow tangentially across the horizontal part of the surface and see what happens. The flow 'sticks' to the surface, the pressure above the paper reduces, and the paper is pulled upwards. This effect can produce benefit way in excess of what might be expected though, and is the basis of 'flow amplifiers' in air movement applications. Google 'flow amplifiers' and you'll find references like:
http://www.process-controls.com/tech..._amplifier.htm

 

Stepped headers (and header design in general) interest me a lot. The problem I have though is like everything complicated with benefits that "get that last 5%," there are lots of different ideas out there on what works and nobody talks about it.

FWIW, I have this header off of what I was told was an 200X Lola Toyota Champ/CART car. 2" Primary, 2 3/8" secondary if I recall correctly. 0.035" wall Inconel tubing, single slip collector, V-band turbo.

The transitions on it are pretty abrupt, not hard steps as they are formed, but definitely not some 7 degree cone. Also, I've seen Inconel step rings for header fabrication where it is a hard step. I've read this is to create a pronounced wave barrier to help reduce reversion.

 

I think the reason that exhaust technology is not published is that its still being used to the advantages of higher end racing teams.

furthermore... the amount of development that goes into optimizing a header (not just one that works) would make you want to keep your lips sealed for all your hard work, trials, and errors.

In my experience with FSAE header fabrication and tuning... the WHOLE package changes the header design.

I spent too many months on the engine dyno trying to correlate what works and what doesn't...and the more I worked on the engine the more I realized that its more complex than I could comprehend.

There are obvious things that work or don't work, but extracting the best power curve takes (IMO) lots of R&D... or trial and error.

*********

Separate topic altogether... I think the best manifold would be made of inconel with a focus on being extremely lightweight and durable. The Evo has 1000 pounds on the front tires... we need to work on that. I really want to make a 16 gauge inconel header for the Evo