grantmac

I've done a search and I can't seem to make up my mind on exhaust. The car will be a mildly modded Autocrosser/Daily driver so I'm looking for very balanced power. I've recently picked-up a RB road-race header and I am torn between a long-primary and a short primary system. I know the long primary will have more top end, but it will also cost significantly more. Here is how I see it:

Long-primary:

Pros:
Awesome top-end
Good for if I port the motor.

Cons:
Much more expensive
Less torque
Heavier (small amount)
More complex to build (I could do less of it myself)

Short-primary:

Pros:
More low end
Lighter (by a small amount)
Much cheaper
I can do most of it myself

Cons:
Less top-end
Less likely to suit porting

Now keep in mind that since I am in Canada and on a budget I cannot order the system from RB due to the cost. Also keep in mind that I am in the city and this will be a daily driver with occasional autocross and TDS rallying events so driveability and fuel mileage are near the top of the priority list.
Thanks for any input,
Grant

QuagmireMan

if you can do it yourself do it then.

coldy13

Go inbetween then. Just buy the RB header. Cut off the collector, add a few feet of pipe to each one, then weld the collector back on. There will still be enough room to put on at least 2 mufflers before the rear so it will be quiet enough.

Rx7carl

Why is it so expensive to get stuff to Canada? Is there some sort of tarrif imposed?

Coldys idea is good, but it'll be wayyyyy too loud on teh street. At this stage, just go with the short system, and see how you like it.

vipernicus42

iTrader: (4)

No, Canada just has had such a shitty exchange rate and GST kills ya.

Picture this: You get payed the same amount, for the same job, but everything you bought from the states had to go through this:

A = price of object

(A / 0.70) * 1.15

the 0.70 is the exhange rate (puts A into canadian dollars) then 15% "Goods and Services Tax" once it crosses teh boarder. So $550 Dollar exhaust system becomes

550 / .7 = 786 dollars plus GST = 903 dollars

so from 550$ to 900$ and I'm making the same pay. Yeah, I guess you get the pic now. That's why it's more expensive for canadians.

Jon

LongDuck

You may be surprised to hear this, but I get more low down torque out of the stock exhaust manifold of my SE than with the RB header, presilencer, and PP muffler configuration. This is because the exhaust velocity has an effect on where the powerband is located, another reason why just moving up to larger tubing doesn't 'fix' the problem of backpressure.

The factory assemblies were designed to give good low-end torque because they knew that the cars would be mostly driven on city streets. Once RB got a hold of the tuned exhaust design, they wanted top HP and a better curve for high RPM driving. In my view, if you're going to drive it on the street and occasional autocross (short course, parking lot size cone-racing), you're better off going with a performance muffler, and maybe upgrading to the RB header for long courses.

Reason being that you're not going to be reving that high in short courses and particularly here, your torque and powerband location is more important than peak HP.

I am amazed every year when I swap out my RB header and presilencer for the stock SE manifold and 3 cats, at how much more torque there is below 5k RPM. That stock system, while restrictive, still works very well with the engine and mild intake mods (stock porting).

As you stated before, if you plan on street porting or bridge porting this engine, then go with a longer primary system. Most people try to plan for a street- or bridge- port, but then realize later on that an engine rebuild is a lot of effort and money just to port the thing, and they never get around to it. JMTC,

81Rex6port13b

maybe you can find some one you know and realy trust in the states. send him the money to buy it. have him buy it and ship it to you? would that be cheaper?

grantmac

Yeah Canadians get the shaft for shipping from the states. What vipernicus42 didn't add was that we also have to pay customs fees to, and if you ship with someone like Fedex or UPS then they charge you even more for brokerage. Honestly it's pretty rough, on the other hand our beer is better
Now back to the Exhaust. I'm probably just going to run a straight 2.25" exhaust back through a cheap glass-pack (doesn't have to last for what I have in mind) and then into a 2.5" in dual 2" out magnaflow.
I figure the combination of a decent sized muffler (22" body I believe) and having the dual smaller tipes will help calm the sound.
Now here is my theory about the glass-pack. The packing isn't the important part, as a matter of fact it basically doesn't have to exist. What the glass-pack is for is for exhaust cooling. When the hot gasses end the expansion chamber made by the empty glass-pack they will expand. Now when they expand they should cool significantly, and the turbulence caused by the perforated core should assist the cooling and maybe muffle just a very little bit. If that fails I'll take it off and repack it with stainless steel. Or I might get a stainless packed one from Magnaflow, but that gets pricy.
Grant

P.S. does anyone see a benefit of me going with 2.5" all the way back and maybe extending the header length for sort of a middle-ground set-up?

rotarygod

iTrader: (1)

Someone has their info way messed up and backwards. Long primary systems favor the low end and the short primary systems favor the high end. The difference is impressively noticable. My current system is a short primary that I replaced a long primary with. Where'd my low end power go? It's not there. It was a bad swap. The reason that many people like the long primary better is because it tunes more along the lines of a usable average powerband rather than strictly topend as with a short primary. This isn't to say that it runs out of juice on the top end though. It doesn't. Maybe ultimate top end but this is much higher than you will ever rev the engine to. I have had a long primary, short primary, true duals, and of course the stock system. Of all of them the stock system had the least power anywhere including the low end. The problem with people having little low end is that they are collecting it to too large a pipe such as a 3". This is not a feasible size for street use. 2.5" max. You don't want ultimate top end power at the expense of low and midrange power when 99.99% of your driving isn't done there, not even in an autocross. Too many people don't understand this. You need power to come out of the corners with at lower rpms and still need to have a semblance of low end on the street. If your engine is stock ported, then either a long primary or true dual. Good luck on muffling a dual setup on a 1st gen. If you have any porting what so ever then do a long primary system. Short primary systems are seldom designed properly as most people just bolt on an aftermarket header and run with it. The problem is that every single aftermarket header is too long for proper short primary tuning and way too short for long primary tuning but they work better than the stock manifold in the power department.

NanaimoRx-7

You're pretty much bang on with the glass pack. I got a free 2 foot-ish hot dog installed at one point, it started out really deep, and slowly got louder. It is now in an FC on 2.5" straight pipe exhaust with a 3" Magnaflow...pretty darn loud. But sexy as all hell.

I think with your smaller tip size it should be a little more contained. I've got a long primary header setup that joins somewhere around the ashtray into 2.25" with 2 - 12" Stainless Steel packed resonators, haven't had any troubles from the police since...complaint free for 2 1/2 years. Good luck.

grantmac

So I just found out that my best friend is good buddies with an awesome exhaust guy (Arnold at Mill Bay muffler for those on the island). He's gonna do me a long-primary system for the cost of piping and flanges, no labour; and I get to help! So I guess I'm gonna go with dual 1.75" all the way back over the axle in 2.5" and then into the maganflow.
Grant (sooo happy)

Pedestrian X

Cool, another Island guy :]

grantmac

Yeah, Islanders all the way! Where abouts are you located Pedestrian X?
Grant

grantmac

Well I just went and ordered a 2.5" in, dual 2.25" out 18" body oval SS Magnaflow! Now my question is this, what if I turned the muffler around and ran 2" pipe all the way from the header into the dual inlets instead of making a Y-pipe? Would there be any effect or downside? Thanks for answering all my stupid questions, I'm really looking forward to taking this thing for a drive.
Grant

Rx7carl

Yes, and not a stupid question. The muffler would make a terrible collector. Dont do it. You'll lose all of your scavenging effect.

grantmac

Y-pipe it is! Hopefully this wednesday. If not I'm waiting a week.
Grant

P.S. is a 18" body muffler gonna do much?

Pedestrian X

Im over by Lansdowne school.

grantmac

I'm on Bay st. by Quadra! We should get togather once I'm on the road.
Grant