: Would Magnaflows help MPG?



fpmesiIII
06-29-05, 02:17 PM
i went to my local mufflerman, for a new mufflers. and the guy asked if i wanted to put magnaflows on for and extra $100. i said sure why not you only live once. but i was wondering aside from the 10-15 extra HP, do they help with gas mileage? oh yeah btw they sound great :D

caddydaddy
06-29-05, 03:24 PM
Well, less restriction usually always means more flow and MPGs. The problem is the exhaust sounds so good that you're on the "go" pedal all the time!
My STS with the Corsa is a perfect example of that! :)

EcSTSatic
06-29-05, 03:47 PM
I had magnaflows on my TurboCoupe. They are good quality mufflers but don't expect "10-15 extra hp" or any measurable increase in MPG.

mtflight
06-29-05, 03:48 PM
Magnaflows...10-15 extra HP... oh yeah btw they sound great :D

I've been wanting to get Magnaflows... $100 for both installed is a great deal...

I don't think 10-15 hp sounds right though. I don't even think the Corsa catback has that much improvement, and if it does they are at high RPMs if I recall.

Regarding the question: It would improve MPG if you got less restriction, ceteris paribus.

95Concours
06-29-05, 04:15 PM
i went to my local mufflerman, for a new mufflers. and the guy asked if i wanted to put magnaflows on for and extra $100. i said sure why not you only live once. but i was wondering aside from the 10-15 extra HP, do they help with gas mileage? oh yeah btw they sound great :D


I got mangaflows.. I didnt notice a HP or MPG increase.. But I like the sound. Was well worth the $220.00 I paid for parts & labor.

davesdeville
06-29-05, 04:16 PM
That would be $100 extra... Extra besides what I don't know.

It will increase power and fuel economy (as long as you resist getting on it) but not by a really noticible effect mostly. I picked up a tenth on my 0-60 time, and WoodShoe said he picked up like .3 or .4s in the 1/4, so it's worth a little bit. The sound is badass too.

mtflight
06-29-05, 05:35 PM
That would be $100 extra... Extra besides what I don't know.



Ahh you're right... re-reading the post, he says he went to get his mufflers replaced... I suppose for a base model of some sort. Then, for an extra $100 above the cost of the replacement mufflers he was getting originally, MagnaFlows were offered....

I really want some... 'been looking... hoping to find a "deal"

WoodShoe
07-03-05, 09:02 AM
OH ya, its worth it. And I noticed quite a lot of difference on mine, especially after replacing the cat. Its not really that loud with just aftermarket mufflers, but it does have a good sound to it. Very subltle at wot but gives that nice rumble at idle. I havent had a chance 2 try the cat at the track yet ..but dave remembers correctly, i went from a 15.1 to a 14.7...with just the mufflers.

danbuc
07-03-05, 01:27 PM
The mufflers on these cars are alot more restrictive then most think. They have to be, to make them as quite as they are. Just doing the mufflers though isn't gonna get you that seat of the pant's difference. You really have to get bigger piping from the cat all the way back to really make a difference. Alot of people have swapped out the stock piping, for 2 1/2" piping, especially the Y-pipe. A few other have also replace their stock cat, with a higher flowing one from Ctaco, or magnaflow I believe. I've been thinking about getting a higher flowing cat for my car, ut nevr got around to it. I have to say though, that the Corsa definitely made a difference in how the car performs.

WoodShoe
07-03-05, 02:48 PM
Went 2 a 2 1/2? Mine was already 2 1/2 I believe. Unless my 2 1/2 in-out cat fit by some miracle?? :hmm:

mycaddy94
07-03-05, 05:16 PM
I have magnaflow XL performance Stainless steel mufflers on my car and they flow 2 to 3 times more than stock, maybe 10-15 horsepower, but definately more. They do sound alot like a corvette or close to a mustang with flowmasters. Not much on mileage though. Maybe one or two miles per gallon, the stock mufflers were necked down to 1.5" inside the mufflers, talk about resrtiction. These mufflers had tips built on. about 350.00 installed.

LT5
07-03-05, 06:48 PM
Does anyone offer a nice cat. back or better yet a complete exhaust for a 95 N* ????

davesdeville
07-04-05, 05:56 AM
Regarding pipe size, I don't remember what the stock size is, but I'm thinking of welding up my own catback if I can find mandrel bent pieces with the angles I need. I'll add a flange behind the cat so I can pull it off when I want to and use a "test pipe" as I hear the import people calling them. I suppose I could look myself, but I'm not getting under my car with all the gross crap on the road, so there aren't any sensors attached to or part of the cat, right? And 2.5" for a 6500RPM 4.6L seems a bit small to me, think 3" would be better?

danbuc
07-04-05, 09:25 AM
You know, the piping in this Corsa kit does look bigger than 2 1/2". I'm gonna go and check to make sure. Now that you mention it, 2 1/2" does seem kind of small for the power this engine is making.

EcSTSatic
07-06-05, 10:02 AM
i went to my local mufflerman, for a new mufflers. and the guy asked if i wanted to put magnaflows on for and extra $100. i said sure why not you only live once. but i was wondering aside from the 10-15 extra HP, do they help with gas mileage? oh yeah btw they sound great :D

Evidently you have the magnaflows now. Maybe you can tell us if they improved your mileage. The trouble with forums is that there's too much speculation. You have an opportunity to provide 1st hand experience.
I doubt you got 10-15 extra HP but why not dyno your ride and tell us?

mtflight
07-06-05, 10:38 AM
Regarding pipe size, I don't remember what the stock size is, ...And 2.5" for a 6500RPM 4.6L seems a bit small to me, think 3" would be better?

Stock Exhaust: 2.5 inch piping back from the catalytic converter to a resonator (high flow muffler). 2.5 inch piping from the resonator to the Y-pipe which splits the flow for the dual mufflers. 2 inch piping from the Y-pipe back to each muffler. Mufflers are offset in, center out. Muffler cases are 20 inches long, 11 inches wide, 5 inches tall. 2 inch piping out from each muffler to dual tips.


In all honesty the real cork ultimately will be the production exhaust manifolds and the "cross through" pipe that goes from the front bank to the rear bank to route the front bank exhuast rearward. The production parts are packaging constrained and designed for emissions performance to light the catalytic converter quickly. That being said, they are not THAT bad....but the real hotrod Northstars like CHRFAB is putting into sand rails and such run headers.

I would go with 2.5 to 3 inch pipe from the cat rearward. It will have to be a custom bent setup as I don't know of any avialable sources for the prebent parts. Several people have tried different brand mufflers for low backpressure. Flowmaster, etc.... You'll have to do some searching in the archives for their reports on sound quality and noise. They will definitely be louder but probably tolerable.

There is really no practical way to put real exhaust headers on the transverse mounted Northstar engines due to space, packaging and routing constraints. The idea of a "free flow" exhaust sytem is not lost on the engineers that designed the production car...but....packaging, lack of space, the cross thru pipe design, emissions performance, durability of the exhaust manifolds and system, etc...all got in the way of real headers....

One thing that will help free up a few HP is to get the exhaust manifolds off and have them extrudehoned. There are a lot of sharp edges and corners in the fab'ed manifolds that can be ground , smoothed and radiused. Not a huge gain here and a lot of work to pull the manifolds and such but if you want the most power the manifold rework with the low backpressure system will provide the most. I would say that the ultimate exhaust on a transverse passenger car with extrudehoned manifolds, large pipes and flowmaster style muffler would probably provide 20-25 HP at peak power.