Shell 91 vs Petrocan 94?
10-21-2017, 04:14 PM
#17
A lot of subjective opinions always come up when this question gets asked, on any car forum.
I datalogged Shell V-power 91 and Petro Canada Ultra94 on my 2008 turbo, to see if I could determine which fuel my car liked best. On the stock tune, my car pulls timing on Shell 91 and the knock sensors pick up a lot of activity.
My car runs much, much better on Ultra 94 - not from seat of the pants or opinion, just based on the actual data I've logged. Significantly less knock detected during datalogging.
I've done the same datalog comparison using my stage 2 tune @ 20.5psi (factory tune is 17 psi). Same results, Ultra 94 much better according to the datalogs.
I can't speak for naturally aspirated cars but modern turbos should be running the highest octane you can get!
I datalogged Shell V-power 91 and Petro Canada Ultra94 on my 2008 turbo, to see if I could determine which fuel my car liked best. On the stock tune, my car pulls timing on Shell 91 and the knock sensors pick up a lot of activity.
My car runs much, much better on Ultra 94 - not from seat of the pants or opinion, just based on the actual data I've logged. Significantly less knock detected during datalogging.
I've done the same datalog comparison using my stage 2 tune @ 20.5psi (factory tune is 17 psi). Same results, Ultra 94 much better according to the datalogs.
I can't speak for naturally aspirated cars but modern turbos should be running the highest octane you can get!
Reminds me of my old E-Type.....I put the highest octane fuel short of avgas that I could find in it and still had to add octane booster to keep it from knocking (or retard the timing and have it run like crap
)Ah, memories
Gary
10-21-2017, 04:50 PM
#18
Drifting
When i dyno'd my 944 race car with a stock 2.5 engine last Spring , we tried Shell 91 and Petro Can Ultra 94 and it was clear that my car prefered the 94 ... this was done at Lachute Performance and they know very well what to do on a dyno !
I was told my engine would be safer with the 94 octane and the dyno results showed it.
I was told my engine would be safer with the 94 octane and the dyno results showed it.
10-21-2017, 05:31 PM
#19
Race Car
Thread Starter
My car runs much, much better on Ultra 94 - not from seat of the pants or opinion, just based on the actual data I've logged. Significantly less knock detected during datalogging.
I can't speak for naturally aspirated cars but modern turbos should be running the highest octane you can get!
The tech said that on a turbo go for 94 while NA the diff between 91 and 94 is marginal.
Older cars use 91 (0 ethanol).
10-21-2017, 08:15 PM
#20
A few weeks ago I filled up the Mercedes with 91 out of necessity. On a sustained hard acceleration the engine sputtered and I had to pull over turn the car off and on, and it was fine. Had a misfire in 3 cylinders. Lesson learned.
Don't try and outrun a Ferrari with 91!
10-22-2017, 01:38 PM
#21
Race Car
Thread Starter
I will try Ultra94 and see if I can feel a meaningful difference in daily driving.
10-22-2017, 05:46 PM
#22
Nordschleife Master
996tt, I feel no difference with 91 or 94. I use 91 but the car may go months between drives and sits all winter. Got some misfires this year and changed plugs, runs great again.
10-22-2017, 08:36 PM
#23
Rennlist Member
Steve Weiner corroborated my approach a while back - at least respecting a normally-aspirated engine.
Tooling around/commuting/normal street use - avoid the ethanol with Shell 91.
Track WOT, towing (!), excessive summer heat/load - use 94 for the margin of protection. Turbos would be in this group for certain.
Steve builds a lot of engines, I trust his input. The data posted above about (tuned) turbo engines is no surprise.
For me that means 91 most of the time between track events. 94 on track, where possible.
Cheers
Matt
Tooling around/commuting/normal street use - avoid the ethanol with Shell 91.
Track WOT, towing (!), excessive summer heat/load - use 94 for the margin of protection. Turbos would be in this group for certain.
Steve builds a lot of engines, I trust his input. The data posted above about (tuned) turbo engines is no surprise.
For me that means 91 most of the time between track events. 94 on track, where possible.
Cheers
Matt
10-22-2017, 10:08 PM
#24
Steve Weiner corroborated my approach a while back - at least respecting a normally-aspirated engine.
Tooling around/commuting/normal street use - avoid the ethanol with Shell 91.
Track WOT, towing (!), excessive summer heat/load - use 94 for the margin of protection. Turbos would be in this group for certain.
Steve builds a lot of engines, I trust his input. The data posted above about (tuned) turbo engines is no surprise.
For me that means 91 most of the time between track events. 94 on track, where possible.
Cheers
Matt
Tooling around/commuting/normal street use - avoid the ethanol with Shell 91.
Track WOT, towing (!), excessive summer heat/load - use 94 for the margin of protection. Turbos would be in this group for certain.
Steve builds a lot of engines, I trust his input. The data posted above about (tuned) turbo engines is no surprise.
For me that means 91 most of the time between track events. 94 on track, where possible.
Cheers
Matt
Gary
10-23-2017, 12:02 AM
#25
best thing anyone can do is datalog their car and see if timing is being pulled.
In particular for turbo cars, tune for the octane/fuel quality you run
In particular for turbo cars, tune for the octane/fuel quality you run
10-23-2017, 12:39 AM
#27
absolutely, however there is limitation too how much timing can be pulled to prevent knock...and is far from optimal from a performance/ efficiency/longevity standpoint... you want your DME basemap to have essentially zero timing pull on the fuel you run/car usage
typically a 91oct is very similar to a 94oct tune, however is richer
factory Porsche 93oct tunes commonly show more timing pull than quality 'aftermarket' tunes as they push towards higher efficiency/lower emissions
typically a 91oct is very similar to a 94oct tune, however is richer
factory Porsche 93oct tunes commonly show more timing pull than quality 'aftermarket' tunes as they push towards higher efficiency/lower emissions
10-23-2017, 05:33 PM
#28
Instructor
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Ive data logged extensively with shell 91, Ultra 94 and Esso 93 when trying to sort my car out after installing larger turbos. Ultra 94, I was getting knock signatures of a 91 octane fuel and pulled a lot of timing on my car. Shell 91 when tuned for it ran perfect, but on a stock tune also pulled timing, like a lot of people tuning cars in Cali have also experienced. On Esso 93 I had the most solid tune and the car ran its best on this. I still add a can of booster to it just in case.
10-23-2017, 06:14 PM
#29
My P-cars and my toys only get Shell 91
Otherwise I use Esso for the aeroplan points.
Not sure if it really makes a difference but I don't have to go out of my way to get Shell vs any other brand
Otherwise I use Esso for the aeroplan points.
Not sure if it really makes a difference but I don't have to go out of my way to get Shell vs any other brand
10-24-2017, 01:57 PM
#30
Rennlist Member
A lot of subjective opinions always come up when this question gets asked, on any car forum.
I datalogged Shell V-power 91 and Petro Canada Ultra94 on my 2008 turbo, to see if I could determine which fuel my car liked best. On the stock tune, my car pulls timing on Shell 91 and the knock sensors pick up a lot of activity.
My car runs much, much better on Ultra 94 - not from seat of the pants or opinion, just based on the actual data I've logged. Significantly less knock detected during datalogging.
I've done the same datalog comparison using my stage 2 tune @ 20.5psi (factory tune is 17 psi). Same results, Ultra 94 much better according to the datalogs.
I can't speak for naturally aspirated cars but modern turbos should be running the highest octane you can get!
I datalogged Shell V-power 91 and Petro Canada Ultra94 on my 2008 turbo, to see if I could determine which fuel my car liked best. On the stock tune, my car pulls timing on Shell 91 and the knock sensors pick up a lot of activity.
My car runs much, much better on Ultra 94 - not from seat of the pants or opinion, just based on the actual data I've logged. Significantly less knock detected during datalogging.
I've done the same datalog comparison using my stage 2 tune @ 20.5psi (factory tune is 17 psi). Same results, Ultra 94 much better according to the datalogs.
I can't speak for naturally aspirated cars but modern turbos should be running the highest octane you can get!