Bear with me on this, this part leads up to the reason for this post. Last week I decided to put the stock muffler and tailpipe back on, I got tired of the drone from the DI/DO Magnaflow muffler. I got a Flowmaster Y pipe and Magnaflow tip for the installation and had them all installed. I figured I would lose peformance but my ears are happy so oh well. Yesterday I decided to remove the Airaid MIT I was using and reinstall the Hemi Hat making my intake stock except for the Ram-Air mod I've had to quite a while. I wanted to see what the truck would run basically stock except for the Superchips. When I got my Superchips, I tested both the 87 and 91 tunes. I posted a thread here showing my findings, the 91 tune was only slightly better than the 87 tune on my truck. When I did the Superchips testing, I had the MIT and Magnaflow exhaust on the truck. My best 87 tune time was 0-60 in 6.70 and the 1/4 in 15.18. My best 91 tune time was 0-60 in 6.67 and the 1/4 in 15.15. These runs were all done with a G-tech Pro.
Now the reason for this post! Tonight with the stock exhaust and basically the stock intake (except for Ram-Air which I had for the previous testing too) my G-tech time was 0-60 in 6.68 and the 1/4 in 15.13.. This is with the 87 tune. I was shocked! The truck "feels" good but it's obviously quieter with the stock exhaust on so it doesn't "sound" as fast. The 0-60 time is faster than my previous best by .02 seconds and 1/4 time is faster than my previous best by .05 seconds. Where's the performance loss from taking off the Magnaflow muffler and the Airaid MIT?? Any thoughts?
Jim

 

Hey Jim, Dhunckyn saw the same thing last year when testing the Volant CAI ( he got an early model ). The stock intake "hat" provides a large area of intake volume that aids in low end response and overall better breathing. Dhunckyn dynoed his stock and with the first rev of Volant ( deletes the hat ). He lost power almost across the entire range. After talking with Volant they sent him the current/new design that keeps the hat. All the power was back plus the "gains" promised by the CAI.
On the exhaust, a DI/DO type of system is notorious for gains on the top end with losses on the bottom due to the reduced restriction. My first guess is that your 60' and 0-60 times are improved, and the losses on the top end are nullified or not being seen.
My two cents....

 

maybe weather conditons were different?

 

I heard that about the first gen Volant intakes, that's why Volant redesigned the intake and kept the Hemi Hat. I actually want to get a Volant, I like the look of the Hemi Hat but would like the engine to breath a little easier. The exhaust part makes sense, the truck is more responsive around town during normal driving, I don't really care if I lost power a 5K rpm's.
Jim

 

Weathers been the same for a while now. Clear and cool with temps in the low 60's almost every night when I get off work at 10 PM, that's when I make the runs.
Jim

 

If you go to wunderground.com you can track you weather conditions fairly closely and you can figure your Density Altitude. from that number you can tell if you make real gains or losses. those numbers are real close.... perhaps your mods were not helping you as much as you thought.....
Just another reason I have yet to do my exhaust.... I figure at least $1000 and I really want to make sure it is worth the cash. It would really suck to spend that much for nada....

TJ

 

With going back to an almost stock exhaust your back pressure is closer to being correct for the cam timing and so on and so on!!!! Thus giving you a better torque curve across the board. Just my opinion.

 

Great info, guys. I have a stock 05 HEMI RCSB 4x4 with just a True Flow drop-in filter. Did I make a mistake purchasing an Airaid MIT???

Also, I've read that our exhaust is 3" Mandrel bent from the factory...a true 3"? Is it SS or Aluminized steel?

If I chose to "open" it up some, which Magnaflow would work best installed with the rest of the stock exhaust (resonator left intact)? I love the sound of the stock system but want some more "noise" out back.

Thanks!

Derek

 

IIRC the exhaust is SS (it is a mild stainless so it will show some signs of rust over time).

RJ

 

Hey Derek! I think the MIT is a good buy if you're going to add an exhaust, if you're going with the stock exhaust, I wouldn't. If you want more noise, then get a different muffler but after havinig the stock muffler on for a while now, I'm a firm believer it flows well, it's just not loud. A good Magnaflow muffler is 12589 or 14589 (12 is alum & 14 is SS), it's 5x11x22's and it's popular when keeping the stock tailpipe. Yes, the exhaust is SS (lower grade but SS) and the tailpipe is mandrel bent. It is 2.75 where it connects to the muffler but it widens out right after to 3" all the way to the tailpipe tip. The resonator is also 3" and it's straight through in design (looks just like a Magnaflow muffler inside) so it won't hurt performance at all. Hope this helps!
Jim