Anybody have an idea how much HP I'm loosing by using 91 octane instead of 93? In Calif, its a pain in the *ss getting higher octane gas.

 

I run 91 octane on my stock '03 and I'm gettin 207.9 whp on a Mustang Dynojet, if any one can compare...then we could probably solve this. But my guess is that you're not losing that much, when I filled up with 105 octane at a track, it felt like I had maybe 10-15 more hp is all...for the extra pain in the @$$ it is to get higher than 91 octane, including the cost, I'll save 2 bucks a gallon and stick with -10-15 hp

 

I don't think you are loosing power by using 91 Octane over 93, unless you are pushing the limits with 91 Octane, then if you could get 93 then you would see more ponies. By using a higher Octane fuel it doesn't always mean you make more power.

 

I was assuming that at WOT, the spark will not be advanced as much with 91 octane, so I'd be down on power.

 

If you are stock the EVOs map is meant to run on 91 octane. The car is made this way. YOu will see more differences in intake temperature and ambient temperature with your EVO rather than the 91 octane.

 

my guess is quite a bit. a stock car dynos at about 197whp on 91 here in AZ using Dyno-Comp's dyno. on 94 octane (midwest, east coast)the same car would pull 212whp. also the owner's manual recommends 97 RON octane gas (european equivalent to about 100 octane here) so unless you mix 100 with your 91 you will experience power losses. my car modded is at 225 whp & on 91 i am running an extremely rich a/f ratio(10.2/1-10.0/1). you will either need to get a fuel computer, ecu reflash, new ecu, and/or pick up some higher octane gas & mix it to see a real difference.

 

Joe,
Yes, I'm stock. My question was prompted because the owners manual says to use 93, and you can use 91 at reduced performance. I thought that the car had multiple maps, probably one for higher octane and one for lower stuff. Or is there only one map?

 

If you compare dyno graphs its around 15-20whp between 91 and 93/94 octane depending on tuning.

If your running a stock set up the car is "designed" to use 93 octane so its probably already pulling timing so yeah lower HP.

I know David Buschur has a post here regarding the gas, his stg 0 and 1 products and tuning. Might want to look into it ..

Using higher octane gas for what your tuned for is a waste of money and gas - plus it'll foul your plugs and add more strain to your o2 sensors ...

Just my .02 cents ... There is a reason why people tune for different maps for different octane ...

 

keep in mind that since we have "self learning ecu's" if you are to get full potential off a stock ecu w/higher octane, you would have to disconnect the battery so the ecu will change timing. in addition to that you would have to use the same mixture every time. if you change the mixture again you have to repeat the above steps unless you have a standalone ems & then it's as simple as changing maps that you have preprogrammed.

 

The stock ECU only has 1 map and pulls timing if you are using a lower octane gas other than 93 ...

 

Thank you...that was the answer I was looking for!

 

97ron is the equivalent to around 90-92pon in the USA.

the ron figure is always going to be higher than the US pon figure since they average the RON + MON ratings here.

 

Thanks for the clarification!

 

NP- Good luck in your modding/tuning ...

 

Its