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      12-06-2012, 12:14 PM   #12
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Drives: Mexico Blue F10 M5(Mika)
Join Date: Apr 2012
Location: Sunny San Diego

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Originally Posted by LAKEOM5 View Post
So with stock everything else and the RPI exhaust what do you think your chp is?
LAKEO Read this!

Originally Posted by RPiM5

BMWDave here from Sunny San Diego. As the title suggests, I have recently installed my new Full RPi GT Catless Exhaust on my F10 M5.
I got it installed last Tuesday and have been driving with it now for two days. I am a long time RPi customer but nevertheless I will offer an unbiased complete review.

First off we'll go over the data.

BMW rates the stock F10 M5 with the following ratings: 560chp & 502ctq

However independent dyno tests of the stock F10 M5 have shown these disparities of horsepower to the crank:
The lowest I've seen is about: 580chp
The highest I've seen is about: 610chp

The RPi Full GT & GTS Exhaust System: RPi states that a gain of 20-30hp is present with both their GT and GTS system as well as a 40tq gain. So we'll go ahead and assume an average gain of 25hp and about 40tq. The RPi exhaust system completely eliminates the secondary cats and the GT system has no resonators where as the GTS includes the resonators but the resonators have no effect on horsepower gain.

With that here is the projected low and high theoretical F10 M5 horsepower ratings with RPi GT/GTS Exhaust System installed:

By adding an average of 25chp to each low and high rating we get:
1. Low Range: 605chp
2. High Range: 635chp
3. Torque is probably between 520ctq - 550ctq with the exhaust system installed.

Real world experience:

The truth is that I don't have a vbox, and I have never owned one. So I'm thinking about investing in one in the near future. No matter though, after I got the exhaust installed a couple of days ago, I was told to drive the M5 hard for a little while so that the ECU can make its automatic adjustments to the increased airflow that the RPi exhaust system offers. After the first night, to be honest I couldn't tell any difference in power or performance according to my butt dyno. Then came the second night, which was last night. I went to a local car meet last night and on the way there I didn't really push it, but on the way back home, I pushed the car pretty hard. It was late at night, about after 10:30pm and the roads and freeways we're pretty devoid of traffic. It turns out that the ECU does need a couple of days in order to adjust to the new exhaust. With RPi's stated gains, one would think that an addition of about 40tq would definitely be noticable in the car. Afterall, it was highly noticable with RPi's catless GT Headers giving the E60 M5 a gain of about 31tq. So yeah, last night when I was pushing the M5 hard I felt a very noticable difference in the performance of the M5. It was one of those experiences where I was thinking that there was no way that the F10 M5 could get any faster than it is stock, but with the RPi GT exhaust system it definitely is!!! When I was at full throttle, I was like GOOD GOD, this thing is insane!

Concerning the exhaust note and drone. Yes the GT exhaust is absolutely louder than stock. And yes there is a little drone that does occur with the GT system. With the GTS system there is no drone, however with the GT the drone only occurs in a very acute rpm range. The range for drone is exactly between 1,500 and 2,000 rpm. At exactly 1,700rpm the drone is the loudest. In my own opinion though the drone sounds SO good! The little bit of extra sound at that low rpm range is just what the doctor ordered on the F10 M5. With the stock system, the car is so quiet and is the reason why they introduced the artificial engine induction sound throug the speakers. With the RPi GT system, the M5 comes more alive during everyday driving at those low rpm's. Now at higher rpm's the decibel level of the exhaust is much louder than the stock system but there is zero drone at those high rpm's. I revved the engine at a few stop lights and while at the car meet last night, and everyone said that it sounds much much better. I even had some dude tell me not to rev my car at the car meet because it was too loud. Lol! When cruising on the highway at 70mph the drone might bother some people because the rpms are right under 2,000 at 70mph in 7th gear, which is right in the drone range. However, cruising at 80mph in 7th gear there is zero drone because the rpm's are at about 2,100 - 2,200rpms. Even such a slight change in rpms makes a big difference.

So in conclusion, in my personal opinion the F10 M5 needs an aftermarket exhaust, it doesn't matter which kind, only to give it more life, especially at low rpm's. If you want an exhaust system that just sits there and looks pretty, then call Akropovic, but if you want an exhaust system that makes real power, performance and sound, then call Race Precision Inc.

I haven't gotten a chance to take any picture of my exhaust in the daytime because I've been working alot, but here are a couple of pictures and video of my M5 when it was still stock compared to another F10 M5 which has the RPi GT system installed. Mine is the one with the Euro Plates on it. I will be doing a photoshoot of my M5 in the near future when I finish all of my mods. All I have left is my Clear-Bra installation this Saturday then I'm good to go.

Hope you enjoyed the review and have a great day!

One last thing. Don't let the YouTube video fool you. The RPi Exhaust is pretty loud. Lol!