Doc Oc

Been doing some research over the last few months on ways to gain horsepower without causing a divorce and have some numbers from the first round of mods that I thought you guys might find interesting. Instead of going the usual longtube route I wanted to see what could be gained through more non-traditional methods. That led me to the PLM log manifolds. Saw some decent gains from them online and thought they looked like a quality product. I paired them with a set of cat-delete midpipes from Armytrix. Both pieces arrived very quickly and were clearly very well made. The midpipes are mandrel bent stainless steel with excellent welds and beefy flanges. Same for the PLM's. Fitment was excellent which I was worried about when mixing and matching like this. I went this route mainly for cost (total investment $1500) but also in hopes of not being too loud like a lot of longtube cars. While I am very happy with the $$ to hp ratio, the car is just as loud as any lt car so no success on that front. I've attached a before and after dyno for those interested. Blue line is v7 tune only, red line is with the addition of the plm's and mid pipes. I was very happy with the gains and would suggest that anyone looking at longtubes also consider this setup as viable alternative. It also offers a major advantage over longtubes in that you can put the oem midpipe back in easily should you have to smog. Thanks for reading!

gmore

Hey Doc,
Thanks for the review - good info.
Haven't got to exhaust yet but will probably go the same route.
Fellow budget modder(if I recall) - if you're looking to tame the exhaust some, may want to look into the Vibrant ultra-quiet resonator...
Used it on my Subi FXT turboXS exhaust and it tamed the rasp and lowered the volume a bit - obviously a different exhaust but I recall a similar high-pitch rasp on the AT MP video and would guess/hope a similar effect....thats if you still want to tame it

Doc Oc

Good to know thanks, I will check them out. I definitely need to quiet it down. Was thinking about having the muffler shop put in an h pipe or possibly changing catbacks. Been looking at some options but lots of differing opinions on the matter.

gmore

If you ever record the sound, please post.
I'm planing on doing just the Armytrix, and there's a couple of videos on how they sound with oem - curious as to what the logs might do.

Doc Oc

I will shortly. From what I've read the plm's don't change the sound at all. They do add around 12 rwhp though. Wish I'd done them separately to know for sure but too late When you get ready to buy the mid pipes shoot me a pm, I have a place bookmarked that offers shipping $50 cheaper than anywhere else I've found.

Adam Chambers

curious, did you upgrade the V7 tune to include the headers for this run? Also were both runs before you installed the new injectors or after?

Doc Oc

No those runs were with old injectors and tune for stock vehicle. l can't say for sure the tune was changed as far as afr or timing, but we did a fresh file with some changes I requested and they were aware of the new exhaust and had seen the dyno. Have an appt wed for another run and will post the results if they are any different.

Adam Chambers

cool, curious to see if those new injectors help out too!

Doc Oc

Same here! However, the results could be a little skewed unfortunately as the last runs were done on pilot a/s tires and the dyno operator was noticing some slippage. He treated the tires and the numbers fell in line but I've now got nitto drag radials which could inflate the gains if slippage was still a factor after he treated the tires previously. I doubt it based on the last numbers but just want to throw that out there.

nardobenz

Can you bolt the Armytrix midpipe to the stock header just to get rid of the cats? And then switch out for the stock midpipe if you need to pass emissions?

Doc Oc

Yes sir....bolts up perfectly. Swapping back to oem takes about an hour. From what I've seen posted, the mid pipes by themselves are worth around 20-25 rwhp. But they are LOUD.

nardobenz

Doc Oc

You'll need to get a tune for the cel. You can make defoulers for about $15 from AutoZone but I have no idea if they work.

nardobenz

Doc Oc

Nah, the cat simulator is outdated info...don't know why they still advertise that. It had nothing to do with 02's, it was just a bulge in the pipe to make it look like a cat visually, but it did nothing and they no longer use them. I'll post up video of my dyno session tomorrow for you to hear.

nardobenz

You have the PLM shorty headers though correct? So it will sound pretty similar to what mine will sound like with stock headers with the armytrix midpipe?

nardobenz

I'm just wondering if I could find flanges, I could just have an exhaust shop weld a pipe to the flanges and make my own and not spend $980 on the Armytrix ones.

Doc Oc

If you can find an exhaust shop willing, go for it. I tried everyone in town and was laughed at as it's a huge fine to tamper with emissions equip. Also, 99% of exhaust shops don't have a mandrel so you're going to get some bends that'll hurt performance a bit.

Sound on mine should be identical to oem logs. Everyone with PLM's says there is no sound difference.

nardobenz

gmore

post #13
https://mbworld.org/forums/c63-amg-w...os-photos.html

1-2 more on youtube - they call it a race downpipe

nardobenz

Doc Oc

I've never heard just a secondary delete car but mine is very loud. Deleting the primaries definitely makes good power but it's insanely loud. I'm having some flowmaster 200 cell cats installed where the secondaries would normally be next week. That should quiet it down without much power loss.

nardobenz

Doc Oc

Get those hfc's put in and you'll be fine. It's fine for DD if you never get on it, but sounds like a Harley on roids when you do.

nardobenz

Does it drone on the highway? I'd like it to be loud on acceleration, I just want it to keep the AMG bark/tone.

I can't mess with my actual catback exhaust because I still have my factory warranty and I don't want to start chopping away.