Would a H/C/I car benefit from a full 3in catback? How would it affect my powerband/area under the curve? I was looking at LGM's Big 3.

 

On a stock 347 CID motor even with a C/H/I package(s), there is no point in running headers bigger than 1 3/4" or 2 1/2" catback. Going with larger headers and/or catback only helps when you are pushing a lot of exhaust gases from either a larger CID motor, forced induction, or nitrous.

Keith

 

I don't buy into their BS....there's no way that exhaust with full-sized mufflers can gain that much power over 2.5" bullets.

 

I too was very skeptical. Then I saw the video, and saw the graphs overlayed. The big 3 outperformed the bullets by 7 rwhp and 7 rwtq. Also took away the drone from what I can tell.

There is a thread the same as this over in gen III external if you care to look at the comments made.

 

Any gains with 3" x-pipe exhaust from the collectors to the catback, over 2.5" X-pipe?

 

Good question brother. I am sure if you have a 2 1/2 inch X pipe, some gains can be had by going to a 3 inch. If you compare the LG Pro longtubes and lg street series you'll see the pros have the 3 inch X and the street have the 2 1/2 inch X pipe. With that being said you can compare the two dynos and see the LG Pros make more rwhp and rwtq then their little brother the street series.

 

Hey bro, go to the LGMotorsports website and check the dyno results page. On a cam only c5 z no bottom end power was lost at all. In fact swapping from the Ti exhaust it made and additional 14 rwhp and 19.5 rwtq. Now if you look at the graph it appears that the biggest gains vs the Ti were had at the 2500 rpm mark. About 25 rwtq difference. Now if you already have something wild like the bullets you only gain 7 rwhp and 7 rwtq when you switch to the big 3. Now keep in mind this is on a CAM only car. Also has lg pro longtube headers and a tune obviously. Now on a H/C/I car I'd like to think at least the same could be had, if not more.

 

Not with a 347 H/C/I package. The extra volume of the pipes will decrease the exhaust velocity and that will hurt low end torque. Unless you are running a 400+ CID stroker, running a 200hp shot of nitrous, or running a S/C or tubro, there is no need to run a 3" mid section or catback. The 3" mid section and catback on a 347 CID motor will give it a deeper tone, but it will hurt low end torque.

Keith

 

You got it wrong bro. My H/C/I 346 with 11.5 or 11.6 to 1 compression loves the 3 inch X pipe. Currently have the bullets on the back. I truly believe I could gain some power by utilizing the big 3. If you look at the graphs you'll see the back to back, same car, same day, same dyno results yielded 7+ rwhp and rwtq on a g5x3, pro long tube, and tuned c5 Z 2003.

 

I dunno Doug, I'm going to have to go the other way on this one. 3inches is pretty darn huge and I hypothesize that if you go 3 inches, then you'll lose low and mid range torque substantially. I think 3 inches would really be for the larger ci engines. There is a such thing called the Law of Dimenishing Returns. The cam only Z being variable A and your car being variable 2, Variable 2 already has great exhaust flow to aid in torque/power production because of the compression and higher flowing heads so gasses are exiting at a much rapid velocity than variable 1 and i feel that 3 inches is only going to slow this momentum down, therefore, causing a loss in power/torque production. You're already operating at an efficient rate, why add more to create an overprodution resulting in loss. Variable 1 on the other hand with the stock heads/stock compression needs some help on the exhuast side compared to your car. The larger piping would slow the velocity of the gasses down, but more volume of gasses could be expensed b/c of the larger diameter piping aiding the exhaust side.

Now 408/418/427/441ci with 11:5:1 or 12.0:1, etc compression would LOVE a 3 inch exhaust because the have much much more air coming in than a 346ci.

 

Well testing takes place in May. So only time will tell.

 

Has anyone seen the video of the big 3 exhaust being tested?? Its on streetfire.net. Sorry no link, but it can be seen by doing a search over there for LGM big 3. Good stuff. I even like the sound.

 

A 3" exhaust system would sound good, but it will hurt the low and mid range torque a bit. For some people, that is a good trade off though.

Keith

 

Hey bro. The test car showed no loss of lowend or mid range torque. It actually showed improvements. Take a look for yourself.

 

Everything is BS..

All these BS dyno #'s... Mean SQUAT..
Meanwhile, cars with 40 less HP are running 2-3 tenths faster..

the only #'s that matter is at the track..

500 RWHP big deal, if it only runs mid 11's

440 RWHP cars are running 10's..

I want to see 1 of those posted dyno graph cars in the 1/4 mile..

Will never happen..

 

Well lets see how about a switch to a heavy *** 12 bolt, 410 gearing, run a set of slicks. Or how about this, switch to an a4 setup and make my car a purpose built 1/4 miler.

YO EL you are completely missing the point of this post. The point is wil the LGM big 3 actually allow a pretty much maxed out aggressive H/C etc etc car make any more power. It has nothing to do with 1/4 mile times. I readily admit I can't launch my car for ****, but with a really good driver she'd see low 11's all day and maybe scratch a 10.999 to go home with. You my friend are comparing apples to oranges and your comments don't help this thread one bit. From the beginning I wanted a car that made a ton of power, and got great gas mileage so I could still use it as my weekend trip car. I have both. Can you get almost 700 miles from a tank of gas if its all highway? That comparison doesn't apply to your car bro, you got a track monster that can be driven on the street. I have a big power, no traction car that is 99.9% driven on the street. Not much city cruising either, mostly highway. How about another ludacris comparison. Your car VS mine in a one tank of gas race, whoever makes it further wins. How about it?? Doesn't look to good for you on that one. Your car simply isn't built for that. Mine is.

Now if you have any evidence that you can share as to whether making the corvettes exhaust a TRUE 3 inch setup will help or hurt the amount of power she makes I'd love to hear it. Your past posts make you sound like you know a thing or two. Please join the discussion

 

A little more commentary. 40 less hp and running 2-3 tenths faster HMMMM>

Let me think. Could traction be an issue, could gearing have any effect at all, does the driver mod come into play.

As I said before my car with slicks would have no problem running low 11's. Maybe even a 10.9xx in a perfect world. Hell I trap nearly 124 ! That should show some of the capability. That was also into a headwind.

 

No excuses...

Spinning, etc, launching... All BS...

Great, a 600 RWHP car that can barely run mid 11's vs a 450 RWHP car that runs 10's..
Which car is faster, the one w/ more power?

Basically in your words more power does not mean faster, so why is it being touted as such?

For guys to chirp & post their tremendous dyno graphs on the internet?
I race on the track with a car, not online with BS dyno charts..

 

You are waste of time to talk to bro. Your comments don't address anything I put to you to answer and justify. You just come on here and talk ****. So your track only car runs 10's. Show me where I claimed anything that you are calling BS on. A 450 rwhp car that puts it all to the ground will always beat a 600 rwhp that spins and hops etc etc. Now if you extend that race a bit the 600 rwhp car will run by you. If you both make full use of the power you have the 600 rwhp will walk you like a dog.

Now to get back on track, the whole point of this thread is whether the LGM Big 3 will allow for more power to be made on an aggressive h/c/i/e bolt on car. Not how much faster will it go at the track, now with that being said please don't post anything else on this thread. Or if you do post, make it pertinent.

 

I don't think an aggressive setup will gain anymore. A mild lower compression such as 10.5:1 setup might gain a tad bit from needing more exhaust help and expelling the gasses quicker.