ninjai

I dont really know if this is pertinent, but I am in the same situation for piecing together an exhaust. I am going with a long primary. Manly after reading arroncake and rotarygod's comments.

I came to the conclusion of using the following.
True dual header
Magnaflow dual in/out pipe ( MPE-11385) at 2.25" as a rb presilencer replacement, 2.25" only because they dont make them as small as 2".

magnaflow Y-pipe collector ( MPE-10758) from dual 2.25" in to single 2.5" out right after the magnaflow muffler/presilencer.

Then a 2.5"straight pipe from the collector to a borla xr-1 ( BOR-40842S) 2.5" in and out. The borla will be the final muffler.

The car will be getting megasquirted with individual throttle bodies over the winter. and bridgeporting in about a year or 2.

All part numbers in parenthesis are from summit racing.

Black91n/a

On a race car a single system has the definite weight advantage as well, only one pipe versus 2 means it's a lot lighter, which is a good thing.

Roen

iTrader: (2)

You mean a short primary into a single muffler?

C. Ludwig

iTrader: (27)

Look under any of Mazda's race cars of the 80s and you'll find a collected header. Look under any ITS FC that's run up front at the ARRC or anywhere in SCCA and you'll find a collected system. It might be a long primary or a short primary but they're all collected. We've used long primary with RB uncollected header, Speedsource short and ISC short. The Speedsource combination made the most peak power. The ISC was best up to about 6000. We haven't tried the SDJ header but they have a good reputation. The RB headers are widely considered slightly sub-optimal because of the sharp bends directly off the flange. We have made 170+ whp with them though so they are not terrible. Truth is that all the good systems end up with power curves that pretty much fall within a couple horsepower here and there of each other. Speedsource has the RD and wins to back their product so it's hard not to go that route. You guys can debate theory all you want but at the end of the day there are a couple products out there that are all pretty similar produced by smart people that are winning all the races. If uncollected worked they'd be using them.

I really don't want to get into the arguement but... True there is no one perfect exhaust. But all ITS engines (should) have the same port configuration, intake configuration, trans gearing, etc., etc., etc. So in this particular context there can be a generalization made that what works on one car does work on another. And what has worked for multiple ARRC champs and best in our testing is the Speedsource exhaust.

For the record, best we've done was 174 whp (Mustang dyno) on a stock ECU with the Speedsource exhaust. That engine is currently leading the Mid-Div championship. Our own car reached 172 (Mustang dyno) with the long primary/RB combo with better low end. That car won the '05 Cen-Div title. With our ECU we haven't seen much in the way of peak HP gains over cars that previously had the fuel pressure regulators optimized for peak HP. You can get any one particular 500 rpm range right by tuning a fuel pressure regulator and the CAS. The gains have been below 7000 and past peak HP where compromises are made with fuel pressure tuning alone.

Also, seems I remember you saying something about your 6 port actuators working or not working in a previous post. For an ITS engine you need to ditch the sleeves and actuator rods. The point at which those sleeves pay dividends is well below the rev range of a race engine. The flow restriction of the actuator rods is real. They need to come out for an optimum build.

Roen

iTrader: (2)

Thanks for the input Chris, I know about the rods and am planning on taking them out.

I also have two FC's, one street and one for the track. The one that had stuck open actuators (since fixed) was the street one.

ericgrau

iTrader: (1)

Okay didn't want to revive this but it seems like things got pretty silly. I checked Racing Beat's website. It says their header (which eliminates the cat) + pre-silencer doesn't make a signficant difference compared to stock manifold + cat eliminating pipe + pre-silencer on a fuel injected car. It only makes a difference if you also get their carbeurator. I saw another thread where someone was wondering why their header looked just like the Racing Beat header yet claimed such a huge horsepower gain (25-30, I think).

Racing Beat is well known for their quality, and their ability to design a muffler that is both quiet and powerful. Mufflers are usually a trade-off between the two; it takes a true understanding of flow and accoustics to do what they did. So if their header doesn't make a significant difference, I question whether others will. Especially when I see dyno sheets that are obvious fakes; the new horsepower curve is just a scaled up version of the old one, static and all. The gains don't diminish at lower rpms like they should. Or there's the RB look-alike mentioned above.

Anyway while I bet it'll add a tiny bit of power, headers don't actually add much.

So until I see actual mathematical equations or a dyno sheet, I call technobabble.

C. Ludwig

iTrader: (27)

http://www.ludwigmotorsports.com/rx7/denton_dyno.jpg


There's your dyno sheet. Stock port NA, stock computer, stock intake manifold. Six port sleeves removed. Fuel tuning with fuel pressure only. CAS clocked for optimum timing. That's more rwhp than these things were rated new at the flywheel. Best guess for flywheel HP is 190-200. So we're making 30+ hp gains with exhaust and tuning. Exhaust is responsible for about 2/3 of that.

I've got a stack of these from a half dozen different cars. The exhaust is the largest bottle neck in the stock system by a long shot.

ericgrau

iTrader: (1)

I know the exhaust is the most important thing to upgrade for power. I'm mainly questioning the headers and pipe lengths. The false dyno sheet I'm talking about shows a before and after with nothing changed but the header.

About 25HP can be gained from cat replacement and catback alone. With that and Ludwig's other mods, there's not much room left for significant gains from the header.

rotarygod

iTrader: (1)

Anyone that says a header doesn't make much more power than a stock manifold has never owned one!

Roen

iTrader: (2)

I'm just wondering why there hasn't been a header made by using similar angle bends as the Speedsource into a dual-piped Speedsource-type pre-silencer into a collector and muffler? Has Speedsource ever tried to make a long primary system to get the last few ponies in the lower and midrange part of the power curve?

C. Ludwig

iTrader: (27)

Yes. At the ARRC, think it was 6 or 7 years ago, they ran 1-2 with Sylvain and David driving. One car had a long primary the other a short. They've done their homework.

Roen

iTrader: (2)

Interesting........

ericgrau

iTrader: (1)

Dyno sheet or other test? Personal guess?

rotarygod

iTrader: (1)

You don't need a dyno sheet to know a header works. We aren't talking about a slight "I think I can feel it" type of gain. We are talking about a "holy **** why didn't I do this sooner" type of gain. A header is VERY noticable assuming your car is running properly.

Roen

iTrader: (2)

please delete