BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > E90/E92 M3 Technical Topics > Engine, Transmission, Exhaust, Drivetrain, ECU Software Modifications
 
Post Reply
 
Thread Tools Search this Thread
      06-15-2009, 02:03 PM   #1
MWorldorder
Second Lieutenant
MWorldorder's Avatar
10
Rep
296
Posts

Drives: M4
Join Date: Apr 2008
Location: L.A.

iTrader: (0)

Rasp almost entirely eliminated by using 100 octane on my RPI GT RACE exhaust!!

First off I have to say that I love my RPI GT RACE exhaust. The increase in power is amazing! I've had the system now for about 3 months and out of the blue decided to try 100 octane just to see what would happen. I added 10 gallons of 76 100 octane to my just under 1/4 tank full of 91 chevron, which made my tank about 3/4 full. I immediately hopped on the freeway and within 5 miles I noticed a dramatic decrease in rasp to the exhuast! I was like WTF? So I exited and came to a complete stop, and upon acceleration was amazed that 80-90% of my rasp was gone and the overall sound of the exhast was so much cleaner! The car also seemed faster! Almost like a boost in torque, but that may have just all been in my head. What wasn't in my head was the change in sound of the exhaust. I had a fellow m3 owner test drive my car who had previously driven my car, and he too was amazed at the change in sound and power.

What I'm going to do now is let this tank run its course and then fill up again with my usual 91 from chevron to see if my rasp comes back. If the rasp comes back like before, I'll know that the 100 octane was the key to eliminating most of my rasp and producing a much more beautiful sound! If it doesn't come back....well....I won't know what to say then. It IS very possible that the 100 octane had nothing to do with this situation at all. I'll continue to post progress on this.


Can anyone comment on the science behind this?

Last edited by MWorldorder; 06-15-2009 at 07:09 PM..
Appreciate 0
      06-15-2009, 02:09 PM   #2
NFDoms2k1
Private First Class
NFDoms2k1's Avatar
United_States
9
Rep
167
Posts

Drives: Cute Little Convertible
Join Date: Feb 2009
Location: New York

iTrader: (3)

Damn, EXTREMELY interested in the results as I too love my GT Race, but really am not a fan of its rasp!
__________________
'09 E93 M3, AW, M-DCT, Fully Loaded
Bunch of mods, why such limited signature space M3post ?
Appreciate 0
      06-15-2009, 02:19 PM   #3
MWorldorder
Second Lieutenant
MWorldorder's Avatar
10
Rep
296
Posts

Drives: M4
Join Date: Apr 2008
Location: L.A.

iTrader: (0)

Quote:
Originally Posted by NFDoms2k1 View Post
Damn, EXTREMELY interested in the results as I too love my GT Race, but really am not a fan of its rasp!

Give it a go, man! Let me know what kind of results you get! This is very interesting! I'm not a fan of rasp as well and am still anxiously waiting on the V2 the be released. If this experiment stands true, and along with the V2, holy sh**.....this will be the best exhaust out there!
Appreciate 0
      06-15-2009, 02:26 PM   #4
JCtx
Major General
256
Rep
5,012
Posts

Drives: No BMW yet
Join Date: May 2008
Location: El Paso TX

iTrader: (0)

Are you willing to use 100 octane ALL THE TIME??? If not, which is my guess, why bother?

It doesn't make any sense to me that octane changes exhaust sound characteristics, but could be wrong. And yes, I'd like to read an explanation if that's the case indeed. Good day.
Appreciate 0
      06-15-2009, 02:28 PM   #5
tightie
JOSH SHOKRI.
tightie's Avatar
United_States
522
Rep
5,881
Posts

Drives: 991 GT3RS, 964, Raptor
Join Date: Aug 2005
Location: los angeles, california.

iTrader: (7)

Garage List
2008 BMW M3  [7.90]
Post a video... or else.
__________________
Current: 16 991 GT3RS , 91 964 C2, 17 Raptor | Past: 2015 991 GT3, 2015 i3,15 YMB F80 M3, 13 E92 M3 DCT, 08 E92 M3 6MT, 07 E60 M5, 02 E46 M3
Instagram: @josh_speeddistrict #SpeedDistrict @SpeedDistrict
Appreciate 0
      06-15-2009, 02:33 PM   #6
MWorldorder
Second Lieutenant
MWorldorder's Avatar
10
Rep
296
Posts

Drives: M4
Join Date: Apr 2008
Location: L.A.

iTrader: (0)

Quote:
Originally Posted by elp_jc View Post
Are you willing to use 100 octane ALL THE TIME??? If not, which is my guess, why bother?

It doesn't make any sense to me that octane changes exhaust sound characteristics, but could be wrong. And yes, I'd like to read an explanation if that's the case indeed. Good day.

If this experiment holds up, I WILL DEFINITELY use 100 octane all the time! I would do a 50/50 with 91 chevron and 100 76.
Appreciate 0
      06-15-2009, 06:26 PM   #7
kmac1980
Major
33
Rep
1,033
Posts

Drives: '19 540xi
Join Date: Jan 2006
Location: toronto

iTrader: (1)

how much is 100 down there???? seems like a pricey solution
Appreciate 0
      06-15-2009, 07:47 PM   #8
MrHarris
yodog
MrHarris's Avatar
United_States
196
Rep
5,026
Posts

Drives: '86 Corolla
Join Date: Jun 2007
Location: Diamond Bar, Ca

iTrader: (5)

Garage List
2009 BMW  [10.00]
100 octane is around $7-8 a gallon around here (LA).
__________________

2009 E92 M3 | Alpine White | Black Extended | Advan RS | Turner Test Pipes | Dinan Axle-Back | OETuning | Eibach Springs | UUC SSK | VRS Front Lip | VRS Type I Diffuser | Matte Black | RPi Scoops | MS Filter | Yokohama AD08 | F1 Pinnacle
Special Thanks: Gintani | OETuning | eAs
Appreciate 0
      06-15-2009, 07:59 PM   #9
SoCalM3Mang
"Makin It Happen-West Coast Style"
SoCalM3Mang's Avatar
United_States
42
Rep
184
Posts

Drives: 2008 E93 Jerez Black 6SPD
Join Date: Feb 2009
Location: So Cal

iTrader: (0)

SICK SOUND!

Quote:
Originally Posted by tightie View Post
Post a video... or else.
Guys....I was "the guy" who drove it.

HOLY SHITE! I've driven your car Josh and Greg's now-- twice. It was different.

Maybe just an anomaly, but it was real. And minimal to no rasp.

I too am interested in his next tank of gas!
__________________
08 BMW E93 6MT Jerez Black|HAMANN-ed|Lots of Carbon Fiber|Eibach E-93 Sprgs|Advan RS-D's 19x9+22/19x10+20|AA-SSK-Pulley|RPI Scoops-Red|RPI Axle Back Exhaust- Blacked Out Tips|Hamann Rep CF Lip-Diffuser-Trunk Spoiler||Hamaan Badging
Appreciate 0
      06-15-2009, 08:16 PM   #10
3XTR3M3
Lieutenant Colonel
3XTR3M3's Avatar
United_States
99
Rep
1,575
Posts

Drives: E92 AW M3 6MT
Join Date: Aug 2006
Location: LA

iTrader: (1)

I <3 Rasp
__________________
Appreciate 0
      06-15-2009, 10:39 PM   #11
dogears
My master volume goes to 11
dogears's Avatar
59
Rep
467
Posts

Drives: 2021 BMW M5 Competition
Join Date: Dec 2008
Location: Cherry Hill, NJ

iTrader: (0)

In my experience, exhaust tone can change with big changes in ignition timing. So, yeah, maybe it is real. Glad we have Sunoco 93 here!
__________________
1987 Buick Grand National, 2009 BMW E90 M3, 2016 Audi S6, 2018 MB E63S AMG, currently in 2021 M5 Competition
Appreciate 0
      06-15-2009, 10:56 PM   #12
dcstep
Major General
United_States
1290
Rep
7,389
Posts

Drives: '09 Cpe Silverstone FR 6MT
Join Date: Nov 2008
Location: Colorado

iTrader: (0)

Garage List
2009 M3  [8.40]
While your at it, do some before and after dyno runs.

Things are different at 5400 ft above sea level here in Colorado, and a blend gives me the best hp (I'm working on finding the ideal blend). I think at sea level you'll find that 100-octane gives you the most hp.

As for cost, I only use the optimal mix for events, like autocross or track days, but a 10% boost in hp is well worth the small cost. As for doing it 100% of the time to eliminate a rasp, that'll be expensive. I don't have that problem with my Active Autowerke Signature exhaust.

Dave
__________________
Appreciate 0
      06-19-2009, 06:32 PM   #13
MWorldorder
Second Lieutenant
MWorldorder's Avatar
10
Rep
296
Posts

Drives: M4
Join Date: Apr 2008
Location: L.A.

iTrader: (0)

UPDATE: I filled up again without the 100 octane and the rasp came back in full form like before. Exhaust tone wasn't as nice either.

Can anyone figure out why the mix of 100 octane reduced my rasp and produced a cleaner exhaust tone? I'm baffled...
Appreciate 0
      06-19-2009, 06:34 PM   #14
King Tut
NASA SpecE30 Racer
King Tut's Avatar
United_States
82
Rep
1,307
Posts

Drives: 2006 Honda S2000 TT3
Join Date: Jul 2008
Location: Gulf Breeze, FL

iTrader: (2)

I can figure it out. It's in your head. There is no way a little more ignition timing is removing the rasp.
__________________
King Tut
2012 BMW M3 Individual: Sold lsb.ridedomain.com
1987 BMW 325is SpecE30: spece30.ridedomain.com
2009 BMW M3 Coupe: Sold e92.ridedomain.com
Appreciate 0
      06-19-2009, 06:52 PM   #15
McLuVan
Lieutenant General
McLuVan's Avatar
Vietnam
304
Rep
13,114
Posts

Drives: ///M3
Join Date: Jan 2008
Location: Socal~818~

iTrader: (1)

Quote:
Originally Posted by 3XTR3M3 View Post
I <3 Rasp
+1
the good kind
not the civic kind
__________________
Appreciate 0
      06-19-2009, 07:12 PM   #16
gthirtyfizle
Colonel
gthirtyfizle's Avatar
190
Rep
2,867
Posts

Drives: E92 M3 AW
Join Date: Jul 2008
Location: NYC

iTrader: (4)

Personally I love some rasp as well. My Remus race with cat and res delete I think is perfect. Its deep at low rpms and once u punch it u get this heavenly sound lol.
Appreciate 0
      06-19-2009, 07:18 PM   #17
MWorldorder
Second Lieutenant
MWorldorder's Avatar
10
Rep
296
Posts

Drives: M4
Join Date: Apr 2008
Location: L.A.

iTrader: (0)

Quote:
Originally Posted by King Tut View Post
I can figure it out. It's in your head. There is no way a little more ignition timing is removing the rasp.
In my head? Ummm....nope.

BTW, the rasp isn't removed completely w 100 octane. Its just reduced.

Maybe I'll post some vids if I have time...
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 01:13 AM.




m3post
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST