Welcome to the North American Subaru Impreza Owners Club Saturday August 23, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Factory 2.5L Turbo Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 06-08-2007, 10:19 AM   #1
03clipsegts
Scooby Newbie
 
Member#: 117692
Join Date: Jun 2006
Location: Butler PA
Vehicle:
2004 30R STI
Silver

Default 115 octane on cobb 93 stage 2 map

I was wondering if putting 115 octane in my stage 2 STI would increase hp and give me better times im going to the drags this weekend and just wondering if it would be worth it or not. I also have a front mount and headers.
* Registered users of the site do not see these ads.
03clipsegts is offline   Reply With Quote
Old 06-08-2007, 10:23 AM   #2
deblas66
Scooby Specialist
 
Member#: 114096
Join Date: May 2006
Chapter/Region: Tri-State
Location: NYC
Default

No, because you're not taking advantage of the octane by running higher boost.
deblas66 is offline   Reply With Quote
Old 06-08-2007, 10:27 AM   #3
03clipsegts
Scooby Newbie
 
Member#: 117692
Join Date: Jun 2006
Location: Butler PA
Vehicle:
2004 30R STI
Silver

Default

See thats what I was thinking but cobb told me it would increase hp they said the computer would read the higher octane. So i figured id ask on here see what people thought. I cant see how it would?
03clipsegts is offline   Reply With Quote
Old 06-08-2007, 10:31 AM   #4
deblas66
Scooby Specialist
 
Member#: 114096
Join Date: May 2006
Chapter/Region: Tri-State
Location: NYC
Default

Quote:
Originally Posted by 03clipsegts View Post
See thats what I was thinking but cobb told me it would increase hp they said the computer would read the higher octane. So i figured id ask on here see what people thought. I cant see how it would?
Yeah but the higher octane won't increase your power, the higher boost 115 will allow you to run will increase your power. The ECU won't increase your boost.

Now if you were tuned for the 115....
deblas66 is offline   Reply With Quote
Old 06-08-2007, 03:58 PM   #5
WRX4ME LE 482
Scooby Newbie
 
Member#: 146086
Join Date: Apr 2007
Location: Hattiesburg, MS
Vehicle:
2007 STi Limited 482
UGM

Default

It should help by allowing your ECU to run at levels it previously couldnt do to detonation. As everybody has pointed out, you will never see the true potential of 115 octane without a tune, but the 115 will allow your car to advance where it previously had to retard due to the lower octane you were running. You will have to run on it some though so your engine realizes and makes it's full advances. As far as worth it, if you can get to 95 or 96 octane cheaper, do it. Itll probably do the same thing.

Basically, 115 octane fuel will allow your computer to do as much as it can instead of retarding like usual.

BTW, isnt 115 too high for normal cars to run without heating?
WRX4ME LE 482 is offline   Reply With Quote
Old 06-08-2007, 04:02 PM   #6
volkl23
Scooby Specialist
 
Member#: 39092
Join Date: Jun 2003
Chapter/Region: MWSOC
Location: St. Louis MO
Vehicle:
2004 WRX STi
Java Black Pearl

Default

Don't do it. It's a waste of money. Get a tuned map. I had a 109 octane unleaded map and it yielded an extra 30HP and more than 100 FT/LB of extra torque over 93.
volkl23 is offline   Reply With Quote
Old 06-08-2007, 04:36 PM   #7
MotorCity
Scooby Specialist
 
Member#: 85085
Join Date: Apr 2005
Chapter/Region: MWSOC
Location: The Big Mitten
Vehicle:
'11 Fiesta
Ole'

Default

I have ran CAM2 100 Oct without a tune.. As others have mentioned, i dont know if its worth 5.25 a gal.. The car felt like it ran smoother but that was about it.

Cheers
MotorCity is offline   Reply With Quote
Old 06-08-2007, 04:59 PM   #8
Badler
Scooby Guru
 
Member#: 133597
Join Date: Nov 2006
Chapter/Region: SCIC
Location: Orange
Default

Quote:
Originally Posted by WRX4ME LE 482 View Post
It should help by allowing your ECU to run at levels it previously couldnt do to detonation. As everybody has pointed out, you will never see the true potential of 115 octane without a tune, but the 115 will allow your car to advance where it previously had to retard due to the lower octane you were running. You will have to run on it some though so your engine realizes and makes it's full advances. As far as worth it, if you can get to 95 or 96 octane cheaper, do it. Itll probably do the same thing.

Basically, 115 octane fuel will allow your computer to do as much as it can instead of retarding like usual.

BTW, isnt 115 too high for normal cars to run without heating?
This is not entirely true. Running with octane more than a few points past what you are tuned for can actually DECREASE power. You are right, the stock ECU will take advantage of up to 96 octane. This would take a while for your computer to learn though(days, weeks, etc...?). There are some threads on raising octane that have some good info on this stuff.
Badler is online now   Reply With Quote
Old 06-08-2007, 05:12 PM   #9
flycaster
Scooby Specialist
 
Member#: 60142
Join Date: Apr 2004
Location: Bend, OR
Vehicle:
2011 WRX
Grey

Default

Quote:
Originally Posted by aaronmsadler View Post
...Running with octane more than a few points past what you are tuned for can actually DECREASE power...
Bingo. At best, it's a waste of money.
flycaster is offline   Reply With Quote
Old 06-08-2007, 05:20 PM   #10
jays05
Scooby Specialist
 
Member#: 78165
Join Date: Dec 2004
Chapter/Region: South East
Location: SC
Vehicle:
05 STI 35r + e85

Default

Just add a gallon or two on top of some 93oct.
jays05 is offline   Reply With Quote
Old 06-08-2007, 05:26 PM   #11
WRX4ME LE 482
Scooby Newbie
 
Member#: 146086
Join Date: Apr 2007
Location: Hattiesburg, MS
Vehicle:
2007 STi Limited 482
UGM

Default

Quote:
Originally Posted by jays05 View Post
Just add a gallon or two on top of some 93oct.
Yep, just like with toluene. Works well.

Quote:
Originally Posted by aaronmsadler
This is not entirely true. Running with octane more than a few points past what you are tuned for can actually DECREASE power. You are right, the stock ECU will take advantage of up to 96 octane. This would take a while for your computer to learn though(days, weeks, etc...?). There are some threads on raising octane that have some good info on this stuff.
Probably right, but who knows what point you really start seeing the decrease at. Mixing in a gal would be best. I dont think it takes too long for your computer to learn all it will, assuming you drive pretty aggressive like most of us.
WRX4ME LE 482 is offline   Reply With Quote
Old 06-08-2007, 05:48 PM   #12
verc
Scooby Specialist
 
Member#: 41754
Join Date: Aug 2003
Location: san ramon
Vehicle:
03 wrx
gt35r, 2.5L, meth

Default

I dunno if it still applies but back in 2002 there was Vishnu's ECU learning trick.

After reset, get to a straight road and bring the car to 3rd gear and hold it at 3k rpms for 10-15 seconds, and all the timing tables will max out
verc is offline   Reply With Quote
Old 06-08-2007, 06:02 PM   #13
Badler
Scooby Guru
 
Member#: 133597
Join Date: Nov 2006
Chapter/Region: SCIC
Location: Orange
Default

Quote:
Originally Posted by WRX4ME LE 482 View Post
Yep, just like with toluene. Works well.



Probably right, but who knows what point you really start seeing the decrease at. Mixing in a gal would be best. I dont think it takes too long for your computer to learn all it will, assuming you drive pretty aggressive like most of us.
You have no idea what you are talking about.
Badler is online now   Reply With Quote
Old 06-08-2007, 07:13 PM   #14
k mier
Scooby Specialist
 
Member#: 98000
Join Date: Oct 2005
Location: MO
Vehicle:
05 sti e85@420hp

Default

Quote:
Originally Posted by 03clipsegts View Post
I was wondering if putting 115 octane in my stage 2 STI would increase hp and give me better times im going to the drags this weekend and just wondering if it would be worth it or not. I also have a front mount and headers.

The stock ecu can take advantage of up to ~96 octane. If it was me, I'd just mix in enough 115 to get roughly a 96 octane blend in the tank. Anything more without a tune is just wasting money. Keep in mind, if you have cats leaded fuel will quickly ruin them.

Try this...download ecuexplorer, (it's free), order a Tactrix cable, (not free, ~$80, but IIRC I used the cobb accessport cable to log, just can't flash), then data log till your heart's content both regular 93, the 96 mix, then 115. Then tell us what you find.
k mier is offline   Reply With Quote
Old 06-09-2007, 03:19 PM   #15
WRX4ME LE 482
Scooby Newbie
 
Member#: 146086
Join Date: Apr 2007
Location: Hattiesburg, MS
Vehicle:
2007 STi Limited 482
UGM

Default

Quote:
Originally Posted by aaronmsadler View Post
You have no idea what you are talking about.
Ha, you'd be surprised.
WRX4ME LE 482 is offline   Reply With Quote
Old 06-09-2007, 03:25 PM   #16
captainllama
Scooby Newbie
 
Member#: 144397
Join Date: Mar 2007
Default

Won't make a difference.
captainllama is offline   Reply With Quote
Old 06-09-2007, 03:52 PM   #17
neonglh
Scooby Newbie
 
Member#: 127886
Join Date: Oct 2006
Chapter/Region: Tri-State
Vehicle:
2006 Evolution
10.635 @ 128.70

Default

It should increase your timing. When I started spraying meth, even before I got tuned, my timing went from 27 degrees to 32.5 degrees.
neonglh is offline   Reply With Quote
Old 06-09-2007, 03:57 PM   #18
hwy61
Scooby Specialist
 
Member#: 87950
Join Date: May 2005
Location: B,ham AL
Vehicle:
2005 STI
Gone....Somewhere in MS

Default

Likely run worse. So what exactly does higher octane accomplish?..........it's harder to burn, therefore you can run higher compression/boost without the engine being destroyed by pre-ignition. And what is pre-ignition, simply the fuel/air mixture burning before the pistol reaches the appropriate position on the 360 degree cycle for your tune and RPM.

Tune for it and you can benefit but, then you have to give the beast a steady diet of it..........expensive.
hwy61 is offline   Reply With Quote
Old 06-09-2007, 08:34 PM   #19
jeebusm3
Scooby Newbie
 
Member#: 86323
Join Date: May 2005
Location: San Diego, CA
Vehicle:
2006 FXT

Default

The cobb map doesn't have enough timing left on the table to be worth it AT ALL. You are likely getting 99.9% of the Cobb map's potential on 93. That extra .1% isn't worth the trouble. And THAT much ocane will burn so slowly......
jeebusm3 is offline   Reply With Quote
Old 06-10-2007, 12:02 AM   #20
k mier
Scooby Specialist
 
Member#: 98000
Join Date: Oct 2005
Location: MO
Vehicle:
05 sti e85@420hp

Default

Quote:
Originally Posted by jeebusm3 View Post
The cobb map doesn't have enough timing left on the table to be worth it AT ALL. You are likely getting 99.9% of the Cobb map's potential on 93. That extra .1% isn't worth the trouble. And THAT much ocane will burn so slowly......

Enginuity shows three KC maps that add to the base timing. Looking at data logs with ~96 in the tank and just roughly adding the total timing, the ecu looks happy and seems to use part of the third table.
k mier is offline   Reply With Quote
Old 06-10-2007, 12:18 AM   #21
theicewall
Scooby Specialist
 
Member#: 70532
Join Date: Sep 2004
Vehicle:
2004 WRX
WRB

Default

Quote:
Originally Posted by aaronmsadler View Post
This is not entirely true. Running with octane more than a few points past what you are tuned for can actually DECREASE power. You are right, the stock ECU will take advantage of up to 96 octane. This would take a while for your computer to learn though(days, weeks, etc...?). There are some threads on raising octane that have some good info on this stuff.
+1, increasing octane makes fuel harder to burn.. simply making fuel harder to burn without doing anything else decreases power not increases it. If you advance timing and/or run higher boost with the higher octane you can see the benefits.
theicewall is offline   Reply With Quote
Old 06-10-2007, 12:53 AM   #22
pearljam11
Scooby Specialist
 
Member#: 113335
Join Date: Apr 2006
Location: Downingtown, Pa
Vehicle:
04 wrxVF39 282/266
05 STi AgileTuned 320/352

Default

I've heard that running a half and half mix of 93 and 100 can be advantageous in the idea that your revs will climb slightly faster than on 93 alone. Maybe?
pearljam11 is offline   Reply With Quote
Old 06-10-2007, 01:04 AM   #23
torqueflight
Scooby Newbie
 
Member#: 147391
Join Date: Apr 2007
Chapter/Region: SCIC
Location: SoCal
Vehicle:
2007 STI
UGM

Default

A few years ago I seen an 05 at the drag strip. He actually ran like .5sec slower by running 105. He was soo pissed, but come on, if the car isn't set up for it, its not going to run right.
torqueflight is offline   Reply With Quote
Old 06-10-2007, 01:31 AM   #24
AZScoobie
Scooby Guru
 
Member#: 8785
Join Date: Jul 2001
Chapter/Region: SWIC
Vehicle:
02 c_turner@ix.
netcom.com

Default

The problem with most high octane race fuels is they are heavy. The burn slower not faster. To take advantage of them you add more timing to start the burn sooner. You run a leaner AFR because not as much fuel is needed.

Running straight race fuel on a map tuned for pump gas will likey decrease power. The AFR will be richer and there wont be enough advance to make power. In the extreme case of running C16 on a pump gas map could cause Rich detonation and pop the motor.

What I suggest is that you add in enough race fuel to get to 95 to 98 octane. This will be enough fuel to add a detonation buffer. Reset the ECU and let it learn up. It will run the max advance it can and you will end up with the most power. You only need a gallon or two. I like to run 1 gallon of C16 to a tank of 91 on my car.

SIde note..

If you use an unleaded race fuel like 100 octane unleaded, VP 103 unleaded or Trick 101 unleaded, You can run it straight. As long as the fuel is an unleaded oxygenated fuel you wont have issues. STill... Mix it 50/50 so you dont throw money away.

Clark
AZScoobie is offline   Reply With Quote
Old 06-16-2007, 10:03 PM   #25
WRX4ME LE 482
Scooby Newbie
 
Member#: 146086
Join Date: Apr 2007
Location: Hattiesburg, MS
Vehicle:
2007 STi Limited 482
UGM

Default

Ok, Ive read wikipedia extensively over and over on this topic, and have come to some interesting conclusions.

There's 2 types of combustion possible in our chambers: detonation and deflagration. Detonation is supersonic and extremely destructive. This is what happens when a combustable mix is under too much pressure at the point of ignition, and it flat out blows the hell up (like a grenade). Deflagration is sub-sonic and is characterized by a slower burning of the combustable matter from the point of ignition outward. Optimally, our combustion would always deflagrate as it releases the same amount of energy from the fuel, but slower and in such a way as it doesnt destroy anything. The only real way octane influences speed of combustion is by changing how much detonation there is vs deflagration. High octane fuel combusts (appreciably) no slower than low octane fuel, it just has less chance of detonation, which is super-sonic.

Our ECU's pull timing in response to a detected knock event. They do this because they assume we are getting close to the threshold at that RPM and load and more det could happen at any moment. We may not actually be at the threshold, but there was percieved knock at that point and the computer pulled timing to keep any similar knock from causing damage. The idea behind retarding timing is to get detonation to occur after tdc, where it has less chance of causing damage as the piston is on its upstroke (sidestroke, whatever). Thing about this is the engine may be 99% knock free at that point, and all its good slow deflagration combustion is being made to release its energy well after tdc, which costs you power.

For these reasons, higher octane fuel will give you more power at a particular level of boost, up to the point of 0 det and full advance.

ALSO, I just remembered. I read usually higher octane fuel has a higher energy content, due to the fact that the chemicals needed to create the extra carbon bonds tend to hold a little more energy.
WRX4ME LE 482 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Cobb AP Stage 2 Map pearljam11 Car Part Reviews 1 06-06-2009 10:56 PM
Cobb OTS Stage 2 map with an APS 65mm CAI? GuammyBear AccessPort 0 05-02-2008 05:56 PM
93 stage 2 map with 91 octane omdwrx508 Commercial ECU Reflashes 7 09-12-2007 05:21 PM
'03 5mt Cobb AccessECU Stage 2-93 Octane 02subadrew Private 'For Sale' Classifieds 1 04-08-2005 07:24 PM
Cobb AccessECU Stage 2 - 93 Octane mweinst Private 'For Sale' Classifieds 9 04-18-2004 08:34 PM


All times are GMT -4. The time now is 09:31 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.