i have mac mids/ORY/magnaflow catback. all with the MS3 and heads....so im guessing it needs to breath alittle more than its allowed to right now. even with my dump open i can tell the cars faster then when its closed. if i did LTs and duels (or something better for max power) would it be a huge improvement? i wanted to get this figured out before the car gets dynoed. also will a NW/fast help out alot also??? i have the LS6 with a P&P TB now.
what would be the best race headers to get? and what exhaust to get?

 

i see some people getting 20 to 30 rwhp when adding LT's and ORY. and with duals im sure your picking up a few more. Lts are a must if looking for or adding power.

 

also i would look into some QTP's the have a high volocity merge collector that adds a few extra hp or kooks, both are stainless and are top of the line. as for the catback the magnaflow you have is a good choice for the mods you have now and when you add the headers.

 

Sadly this is a complex area and no where near as clear cut as made out by the other poster.

First things first. Although the Magnaflow catback is good, it is not a straight thru bullet style muffler. Thus it will likely be a restriction. In the dyno section last week someone posted dyno results and I think it was only a bolt on car still picked up 5rwhp/5rwtq with a cutout open with a Magnaflow catback. So it shows there is gain to be had.

As for the Mac mids, well here's the issue.

Flow rate is probably the same as any other tubular header using the same primary pipe diameter and the same collector size.

Q. Do you know the collector size of the Mac Mids? Most LT's are 3", any smaller and it will be a restriction.

Tubular manifolds make most of their HP gains on a n/a applicatoin via scavenging and NOT flow rate.

Mids DO scavenge but only most effectivly at high rpms due to the primary lpipe lenght of the headers. This should in theory suit the MS3 as it likes to rev to make its power.

Lt's scavenge in a different rpm range and will generally scavenge at lower rpms. So a simple change from mids to LT's will likely yeild better under the graph numbers while PEAK HP will likely be quite constant.

But it gets more complex again. Port runner lenght, exhaust valve size, heads and cam all have a bearing on exhaust.

There is no one magical header that makes the most HP

Each setup is different and requires a header to match the requirements.

This then follows onto the exhaust itself. David Vizard tells us we need 2.2cfm per 1 HP of flow downstream.

A single 3" pipe will generally be a restriction on a cammed LS1 although I don't believe this restriction is going to be substantial. So HP loss will only be minimal.

A 3.5" single pipe will flow sufficently for your setup. 2.5" duals will also outflow a single 3" setup so there is the possibility of a gain. But again I doubt it will be much. Or if it is it's due to other reason as opposed to just pipe diameter.

Y pipes also scavenge in a similar manor to an X pipe, so if you have a good merge collector this is unlikely to be an issue.

Remember many people have made VERY big bhp numbers while using 3" Y pipes and aftermarket catbacks.

It's also worth noting that LG, who arguably make the best Lt headers for Corvettes actually convert their X pipe into a Y pipe for their race cars. If this was detrimental to performance they simply wouldn't do it.

Lastly, a FAST 90/NW90TB should see in the region of 20-25rwhp increase over a LS6 setup.

If you have money to burn and feel you have covered every over option, then go ahead and swap the mids for LT's.

I would check the collector size on the mids first though. But swapping them over for LT's is going to be pot luck whether you see gains or not. And although rare the possibility of loosing PEAK HP is a consideration. This would be due to how well the headers match the rest of the setup.

What sort rwhp level are you at now and what other mods do you already have?

Are you A4 or M6?

As for headers well you have cheap and expensive ones. Only difference is cheap are mild steel and will rust, even if coated. Expensive ones are stainlees steel and will last the life of the car and look prettier for longer.

Cheap:
-Pacesetter
-Edlebrock

Expensive:
-QTP
-Stainless Works
-Kooks

All will make about the same bhp give or take.

LG are supposed to have some new LT's out soon with longer primaries. They will probably cost a small fortune, but it may be worth waiting for them.

 

hey i just copied this off my cardomain.....the macs are 2.5 i think
lemme know if you need any more info.....M6
98Z28

JE pistons
Eagle rods
MS3 cam
brandon nix P&P TB
brandon nix heads
patriot gold springs
hardened pushrods
ported oil pump
rollmaster timing chain
LS6 intake
UD pulley
MMT lid w/ K&N
MAC headers
ORY - cutout
Magnaflow catback
MAC subframes
BMR lower control arms
BMR panhard bar
Eibach Prokit
Grant Steering Wheel
T-56 rebuilt by TDP
McCleod adjustable master cylinder
Centerforce dual friction clutch
Pro 5.0 shifter
Lou's short stick
MAC girdle
3.73
Zexel Torsion posi

 

So the difference between LT's and an ORY with cutout vs. LT's with true duels would be minimal if anything? This is what im debating on for my car...

 

It's simple really - if you want duals then get them, they sound awsome.

Just research it first so you don't have to redo anything later on down the road. Particulary body mounted torque arms.

 

Well you already seem to have a lot of area's coverd.

I know there are some (not many but a few) that swear Mac Mids make great power and that they lost PEAK power going to LT's.

However I think as a minimum you'll see an increase below the curve even if the PEAK numbers don't alter much.

If it was me and I had the money I'd probably go for it, although I think I'd wait and get a set of stainless steel LT's. Most probably the QTP's.

 

No i dont care about the sound at all,im talking HP....

Difference in HP minimal or what?

 

Look there is no "one" answer.

Duals may yield more power, the same power or less power.

There's a link in my sig Induciton/exhaust read post 6 and 13 onwards and it will likely explain all you need to know about exhausts.

But to simplify exhaust design is about:

-Exhaust flow
-Exhaust gas velocity
-Exhaust pressure wave
-Scavenging (primarily n/a applications only)
-noise db reduciton

All I can tell you is on a like for like basis a good Y setup should perform as well as a good dual setup.

However what you will find is most people compare a bad or average Y pipe setup to a good dual setup and claim it was 100% the dual part of the exhaust that made the difference. When it may not be the case.

At the end of the day, if you are after every single last pony available that the exhaust has to be critical then you will also not have air con, stereo, and electrics beyond legal requirements, no interior, carbon fibre body panels, etc.

Most people generally accept a "good" setup.

If it must be the best it will cost you. Formula 1 cars used a special exhaust for qualifying to give the ut most in performance. Sadly the exhaust only survives about an hours worth of use though and it costs in the region of $25,000