magnaflow cat back for the V6

[Chief]

Hi all. New here but thought I'd drop some info on the V6 cat back. Hope I can get some comments from this group to help out.

Here's a couple of post I made on another board for those who haven't seen them.

I got a message from Magnaflow tech about a month ago asking if I'd be interested in loaning them my G8 V6 to prototype, install and test their new V6 cat back system.

Well last Monday, 8 Dec, I drove down to their shop and dropped off the car. The only mod to the engine so far has been the oil change to royal Purple. Other than that, it's stock which is what they wanted. I was suppoed to pick up the car today but I talked to them yesterday and they need it for another week.

They said that the exhaust sounds great outside the car but that they have a problem with interior drone and are building a new muffler to try and fix that problem. I ha dtold them that this was my family car and so I was concerned about interior noise and they have taken that to heart.

They will also be running the car on the dyno to get some numbers but have only done the base line so far. They have to get the exhaust right first before they put it back on the dyno.

Base line numbers were 196 HP and a little over 220 Tq. I was a bit supprised at the TQ number being that high based on the HP numbers. But that's a good thing. We'll see how it all turns out when they are done.

I'm thinking they should have systems ready after the start of the new year. I'll keep everyone posted as I find out more. Can't wait to get the car back and see how it is. I'll have about 110 mile ride home when I get it to evaluate it. The guys at Magnaflow are really great people and have worked with me to meet both of our goals.

[Chief]

Here's a update I posted as well.

OK all, a little update here.

I picked up my car last Monday and have put a little over 600 miles on it since then. Gabe at M/F is a great person to work with.

I still have the prototype cat back system on the car as they tested it. Gabe will be sending me the dyno results and noise sound bites once they get their computer back up.

Here's my impressions so far and I've relayed them back to Gabe, awaiting his reply on them.

The Good:
The initial sound outside the car sounds good. Typical M/F deep low hum. I like it.
At cruising speed, 70 - 80 MPH, very little drone inside the car.
Even though I hadn't driven the car in two weeks, the butt dyno says it has more pull.

The Bad:
really bad drone at the following places;
1500 RPM in 5th gear with slight throttle applied. If you down shift or give it more gas so it down shifts, it goes away. But really loud and anoying.
2500 RPM in 4th gear. Same situation as the 1500 RPM drone.

In normal driving with engine speed staying around 2500 RPM while it goes thru the gears, it has a drone. Not as bad as the other two places but still anoying.

I also noticed a vibration when my arm was resting on the center console when I had the 5th gear 1500 RPM drone. I could make it come and go with the gas pedal so I know it was related to the drone.

Overall the system is a bit loud for me in this car. It sounds cool for the first few times of driving it hard but it gets old fast. I don't mine loud noises as I ride a Harley with loud pipes, I just think with the look of this car, loud pipes are not what it needs. A nice low rumble would better suite the car. Espically since this is my family car and the wife and kids will be taking long rides in it.

As for design, the pipe size has been increased to 2 1/2 inches, it has a X pipe in the system, then a 2 in, 2 out resonator flowing back to 18" mufflers.
The stock system is 2 1/4" pipes with a 2 in 2 out resonator, 2 smaller resonators, one on each pipe and then the big box mufflers.
I don't know if the lack of a second resonator is causing the problem or the X pipe. The X pipe I assume is to try and help with the noise cancelation as well as increase HP.

I'm going to leave the system on the car for a while longer and see how it goes. I'm also waiting for a reply from M/F and see where they want to go with the system. I'll report back what happens.

[Chief]

And some testing I've done so far.

Well alittle more update here. I've been trying to get ahold of magnaflow but I think they are busy moving into their new tech center. Gabe said they were going to be moving after the first of the year so that may be why they don't answer.

Anyways, I took a ride the other day with the wife. Was driving normal and was on a road with a 50 MPH limit. Lot's of cops around along with traffic so I was stuck doing 45 to 55 MPH. Man talk about an anoying sound. The drone is terrible at that speed. I couldn't hear the radio or hold a conversation with the wife. I finally had to drop it into 4th gear just to be able to hear anything. I'm hopeing to get ahold of magnaflow to see if they have a resolution. This may delay the release of their system but it's a problem that I think needs to be addressed.

On another note, I did get out and play a little with the G tech I picked up. I got 2 runs in for the 1/4 mile before the cops showed up and I had to quit testing. Temp was 77 and I'm near sea level, less than 100 ft above.

I didn't try anything fancy as I was just starting to learn the G tech. I put the car in sport mode and left it. Traction control was on. I did nothing more on the launch than hit the gas. Best 1/4 was 14.8 @ 101.4 MPH. 0-60 averaged 6.5 out of 4 runs.

I was just getting used to running the G tech and was setting up to do some launches from 2000 RPM's when the CHP showed up so I figured my luck was running out and I left the area. I'll try some more runs when I get a chance.

As noted, only mods are Royal purple oil and the Magnaflow prototype cat back system with GT tips. had a little over 1/2 tank of gas and was running regular gas. I weigh in at 220 lbs

[Chewy]

That's not bad!

Have you ridden in or driven a GT?

[Chief]

I test drove a '09 GT when I went to buy the car. They wouldn't deal on it. Only '08 they had that they could deal on was a white GT. Only stipulation the wife gave when going to buy a new car was no white cars. So now I have a V6. Blown Chevy from Magnuson now owns the white GT. ;)

I'm happy with the V6. Has everything inside I like. Just trying to get a little more out of the motor as well as a decent sounding exhaust. I like to tinker and as you can see in my sig, nothing I own is still factory stock. ;)

GM has this same motor in other platforms that are pushing out 275 HP and the direct injected version is pushoing 300 so it shouldn't be too hard to get some more out of it. Specs on the motor show it to be a stout motor. Forged internals, 6 bolt mains. Dual overhead cams, etc. All the good stuff.

[-Ray-]

Thanks for all the updates. All GRRRR8 information.

[Chief]

I talked with Richard, the senior tech in the tech center at magnaflow yesteday about the drone.

He basically stated that the V6 causes the drone at that freq. due to the engine design/firing order. They are not sure if they can make something that will eliminate or decrease the drone and still make power AND be profitable. A lot of it has to do with harmonics and the lack of a lot of insulation in the cabin of these cars.

He also stated that they had a similar problem with the DI V6 in the Caddy but since they are better built body wise and insulation wise, they were able to overcome it.

He also siad that the drone in the V6 is louder than the V8.

I also received a Email from Gabe at the Tech center who I have been working with and it looks like he's still trying to work on the drone. I'll update this thread when I find out more.

[Chewy]

A bit of dynomat helped quite a bit in my GT. I bit more would help even more but I quite like the sound.

[Chief]

Richard and I talked about that. He didn't think it wpould help much on the V6 because of the frequiencies that we are dealing with. They are different from the V8.

The system sounds awsome, don't get me wrong. The only problem is crusing at 45 - 55 MPH which is around 1500 RPM in 5th gear. At that RPM, the drone is so anoying and you can barley hold a conversation or hear the radio at a normal level. If you down shift to 4th, no problem.

But downshifting to 4th may be a problem for some, like the wife. She'd rather just get in and drive instead of having to down shift and then remember to either shift when stoping or moving it back into normal mode until you get back at 55 ish and down shifting to 4th again.

If you can live with that, then I'd say by all means go for the system, it sounds awsome on the outside of the car.

One other thing Richard and I talked about was if I increase the HP output of the motor with a ram air and tune, would it change the drone. It might, since it will increase the exhaust flow but only testing will tell.

He did say they may just sell it as a off road system for these reasons.

[harddrivet]

Chief are you still running this with the drone?

[kidhauler]

Someone on another board suggested that the drone may mellow as carbon builds up on the internal parts. Have you noticed any reduction in drone with time?

-Dennis-

[Zanardi1782]

I can't wait for this exhaust to come out. Please keep the updates coming, Chief, and thanks for volunteering your car.

[Chief]

Sorry I haven't posted here in a while. Here's teh latest.

The drone got to be too loud and so i have removed the system and went back to the stock system. I sold it to a guy on the east coast. he's happy with it but dosen't like teh drone. But he's dealing with it by turning the radio up louder. That just wouldn't work in my case ince this is suppose to be the family car.

After I put the stock system back on, I started getting a O2 sensor slow to respond. They went thru several things, including relearning and reprograming the computer, replacing a O2 sensor and replacing the computer. It still didn't fix the problem. It's an intermitent problem. The last thing they did, which was last wek, was to pull all of the electrical conections and check them. While they were talking to GM about the problem, they found out that the stock system had been cut and clamps were installed on it now. The system ws cut by Magan Flow so they could ship it back to me. It didn't seem like a big deal but they were trying to make it into one.

I got the car back and went and had all of the clamps removed and the pipes welded back as a single peice. Now it's juts a matter of time to see if the fault returns. If it does, I'll be turning in the car under the lemon law and trying to get another G8, maybe a GT or a GXP. Time will tell. I'll also settle for a V6 as I have no problems with this motor.