What octane to run?
- Thread starter bmp3
- Start date
exoticracr
Banned
Yeah, and it could actually destroy your motor (worst case scenaro).
They don't recommend it because it costs more. There is a reason.
If you want to run regular, trade your ECU and get a P5 ECU.
They don't recommend it because it costs more. There is a reason.
If you want to run regular, trade your ECU and get a P5 ECU.
if you ran regular gas, your engine would do one of two things...
1) possibly detonate your motor - costing you thousands just so you can save a few bucks at the pump
2) the ECU will compensate for the cheap gas and pull timing, causing your car to run probably even worse than a standard p5, in which case the added benefit of the MP3 model's performance isnt there, and you payed more money when you could just have purchased a regular protege.
Long story short : DONT run anything other than premium. Only more harm than good will ever come of it.
1) possibly detonate your motor - costing you thousands just so you can save a few bucks at the pump
2) the ECU will compensate for the cheap gas and pull timing, causing your car to run probably even worse than a standard p5, in which case the added benefit of the MP3 model's performance isnt there, and you payed more money when you could just have purchased a regular protege.
Long story short : DONT run anything other than premium. Only more harm than good will ever come of it.
Rumour has it, you can run regular fuel on the MP3 ECU and it will retard timing, basically making it a P5 ECU. I never had the balls to do it when I had the MP3 ECU. But wow.. I really noticed the performance hit going back to the P5 ECU :'( oh well, all in the name of progress (turbo)
So yes, you might as well trade ECUs with someone and pocket the profit
So yes, you might as well trade ECUs with someone and pocket the profit
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The MP3 ECU is not running so high strung that the motor will grenade for running "regular" octane fuel. The cheap gas won't do any damage, the car will back off the timing advance IF it "hears" knock.
That is why it is "recomended" not "required"....
That is why it is "recomended" not "required"....
StuttersC said:
Understandable, Im just giving the "if you have the shittiest luck imaginable and God hates you" worst case scenario. Its possible, just HIGHLY unlikely.
With my luck I wouldnt say it, and hed be back in here a week later with a blown motor somehow.
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B1GHAM said:
I see. The only case where high octane would really be needed, IMHO, is if you are running a turbo on the MP3 ECU.
If he has that kind of luck, well, he should play lotto.
- :
- MP5T / 944
Pay Up..
sorry to bump an old thread. . .I'm curious. I've got a longer commute now (moved into a house now that's far from work) and while on my most recent gas fill up (today) I got 30 MPH!!!!!!!!!! If I were to swap in P5 ECU and run 87 octane, how much would my MPG increase? I'm just curious to see if the thought would even be worth it. . .
It will not harm the MP3.
I've ran 85.5, yes, 85.5 for over 3 years now, almost 4.
No knocks, no reduced performance. And saved around 15-20 cents per gallon doing it.
Higher octane does not increase performance, it reduces the change of pre-ignition, aka Knocking.
Over 3 years straight is enough proof for me.
I've ran 85.5, yes, 85.5 for over 3 years now, almost 4.
No knocks, no reduced performance. And saved around 15-20 cents per gallon doing it.
Higher octane does not increase performance, it reduces the change of pre-ignition, aka Knocking.
Over 3 years straight is enough proof for me.
JoeManNorth
Member
- :
- Mazda MP3 - Blue
It does increase performance.
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SilentSno said:
The increase in performance is at the top end where the advanced timing carries out power a little further. I don't think you are driving your car there, so you probably wouldn't notice.
Running lower octane fuel will cause the ECU to not advance the timing as much because of knock. I would like to see a stock MP3 get on a dyno and do some pulls with high octane gas and low octane gas and see what happens.
That would be the only true way to know if the ECU is really that involved.
I autox as well, high revs, and still no issues. Still smoke those WRXes without good drivers. 
Sometimes even the local STIs.
And i'd bet money the differences on the dyno of any car will be within the margin of error for any octane level that the car can safely run without knock.
Obviously higher compression and turbocharged engines benefit a lot from not knocking, hence higher octane.
Search the web, you'll find no proof.
My father-in-law was a top Porche mechanic, I think he'd know something too.
I hate to reference wikipedia, but its pretty accurate.
http://en.wikipedia.org/wiki/Octane_rating#Effects_of_octane_rating
Sometimes even the local STIs.And i'd bet money the differences on the dyno of any car will be within the margin of error for any octane level that the car can safely run without knock.
Obviously higher compression and turbocharged engines benefit a lot from not knocking, hence higher octane.
Search the web, you'll find no proof.
My father-in-law was a top Porche mechanic, I think he'd know something too.
I hate to reference wikipedia, but its pretty accurate.
http://en.wikipedia.org/wiki/Octane_rating#Effects_of_octane_rating
JoeManNorth
Member
- :
- Mazda MP3 - Blue
I think you would see a bigger difference then you think. Seeing higher octain burns or "blows up" more, hence creating a bigger burst of engergy that pushes your cylinder down plus lets your ECU advance the timming giving you the 10 extra hp over a stock protege.
Ask your father in law, dont assume what he thinks.
Ask your father in law, dont assume what he thinks.
JoeManNorth
Member
- :
- Mazda MP3 - Blue
StuttersC said:
and I second that.
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SilentSno said:I autox as well, high revs, and still no issues. Still smoke those WRXes without good drivers.
And i'd bet money the differences on the dyno of any car will be within the margin of error for any octane level that the car can safely run without knock.
Obviously higher compression and turbocharged engines benefit a lot from not knocking, hence higher octane.
Search the web, you'll find no proof.
My father-in-law was a top Porche mechanic, I think he'd know something too.
I hate to reference wikipedia, but its pretty accurate.
http://en.wikipedia.org/wiki/Octane_rating#Effects_of_octane_rating
On one of those Tom Hnatiw shows on Speed they put a Porsche on the dyno. Low octane gas and high octane, there was a significant difference (in the neighborhood of 5-10 horsepower difference). I forget the numbers, but not with in the margin or error for a dyno.
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