last year my car (03 cp 6mt) seemed to really slow down. I had my neighbor advance the timing by 2 degrees. With this the car really felt much better. Next week I put in tank of 93 Sunoco and the car responded much better still. Now with a lot of slow driving during winter car has once again slowed down in acceleration. the following week I needed fuel but everyone was out of hi test...I filled up with 89 Octane fuel from GIANT FOODS...well who would have though but the car is now faster than it ever was...it would seem to me that with the 2 degree advance and the 89 octane is the diet it really likes...and as an aside the temp was 40 degrees with 30.3 barometric pressure. Very happy with performance now but do plan on a 5/16 plenum spacer when it warms up. If anybody has experienced something similar to this with either a change in timing or fuel I would like to hear from you

 

Well ofcourse higher octane fuel with yield more power as well as the timing advancement. If you get that spacer get hfcs/test pipes or ART pipes and you will really feel it! BTW your not from NoVa are you?

 

i dont see how you put lower octane and felt more power. you're lowering your octane rating and increasing timing....maybe the leaner mixture? hello detonation.

 

I moved from s. Virginia in 96

 

im with you, butt dynos often lie LOL

 

better yet, dyno ur car with the 93 and then with 89....with wideband. dont post back til you got charts lol

 

The only thing I can think of is that he's running on the verge of detonation because Thats where the most power is made. It makes sense since he lowered his octane. Im not sure that it would be that drastic of a change.
It might just feel more responsive.

I wouldnt recomend running 2 degree's advanced and fuel with a lower octane rating then what is called for on a bone stock vehicle.

 

Yikes.

 

Its unlikely to det even with lower octane fuel, as the ECU will pull timing and keep it there until different fuel is used.

I suspect the OP has been just cruising around previously, and has recently started driving with more aggression on a more regular basis, and as the ECU will adjust fueling and timing to the driving style, its probably that he's feeling.

I thought it was common knowledge that if you run a G35 or 350Z on a dyno, it will need five or six WOT runs before it will record it full potential power.

 

I agree. I dont know how much timng the ECU can pull, but you are right that it will probably pull enough to keep it from pinging, as running 89 vs the recommended 91 isnt that big of a deal.

 

premium is normally 93 from what im used to and only run. so in that case, thats a bigger drop than id ever feel comfy with driving with. it'd be ok to do normal driving with, but i wouldnt recommend any sort of aggressive driving with it.

 

Its not that bad being that 91 is the recommended fuel. So in actuality you are only dropping one fuel grade not two.
The computer will compensate for the lower grade fuel, and you probably never know.

My initial post I was thinking (in relation to an old vehicle of mine) that the timing advance was done via the Distributor, so in some cases the ECU couldnt pull enough timing to prevent detonation. Not the case with our cars now.

 

set timing back to stock, put 93 back in the tank, and reset the ECU and drive like mad. poof your car is now faster…. and no risk of detionation, well atleast less risk.

 

Isn't your fuel grade measured in a combination of MON/AKI rather than RON? not sure, but i think your 91 will equate to about 98/99RON, and in any case the US G35 VQ35DE will be mapped to take an average of what fuel grade is readily available, so i really cant see fuel grade being that much of a problem anyway.

 

Yes I belive R+M/2.
Octane ratings from 87 - 93 are readily available. Some as low as 85 or as high as 94 are common in certain areas. The US coupe requires 91 octane and 91 octane is "recommended" for the sedan.