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Discussion Starter · #1 ·
So I've been running this tune for a bit and am seeing some small amounts of knock. (Here's a log for reference) Was just wondering if this is concerning at all as I've been reading multiple different opinions on what's alarming and what's not. I've seen as high as 3.8 before but typically the highest is 2.8
 

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I got an official reply from Cobb. They recommended me on a stock STI motor and Canadian gas, to NOT use Stage 1 93 octane maps. Even with 94 octane. They recommend I run ACN 91 map. Apparently, Canadian gas is that bad.

I drove approx 150 miles today on Stage 1 91 and 93 octane in the tank. No major knock events the entire trip. It never went below -1.4. I plan on doing more datalogs to confirm.

Thought I'd throw that out there for you.
 

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Discussion Starter · #3 ·
I got an official reply from Cobb. They recommended me on a stock STI motor and Canadian gas, to NOT use Stage 1 93 octane maps. Even with 94 octane. They recommend I run ACN 91 map. Apparently, Canadian gas is that bad.

I drove approx 150 miles today on Stage 1 91 and 93 octane in the tank. No major knock events the entire trip. It never went below -1.4. I plan on doing more datalogs to confirm.

Thought I'd throw that out there for you.
Thanks I'll give the stage 1 91 octane tune a go and see how that works out. Weird thing though. Even on the stage 0 tune I was getting identical readings so not sure what's up
 

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Thanks I'll give the stage 1 91 octane tune a go and see how that works out. Weird thing though. Even on the stage 0 tune I was getting identical readings so not sure what's up
I am by no means an expert, but from everything I have read, it's not unusual to get -2.8 knock on the hwy, since you are cruising at lower RPM's and higher loads if you boost it on 5th or 6th.

But as I have a stock motor, and no desire to grenade my engine, I will stick to a 91 map and just run 93 octane, and datalog much, to ensure no anomalies.
 

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Discussion Starter · #5 ·
I am by no means an expert, but from everything I have read, it's not unusual to get -2.8 knock on the hwy, since you are cruising at lower RPM's and higher loads if you boost it on 5th or 6th.

But as I have a stock motor, and no desire to grenade my engine, I will stick to a 91 map and just run 93 octane, and datalog much, to ensure no anomalies.
Yeah judging by my vehicle speed It looks like most was highway and had decent loads going when it occurred
 

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91 and 91 ACN are two different things. Use the 91ACN.

Does Canada use the (r+m)/2 method for octane?
 

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91 and 91 ACN are two different things. Use the 91ACN.

Does Canada use the (r+m)/2 method for octane?
I have no idea what formula they use here. I always assumed it was the same as whatever is used in the US, but I guess not? I'll have to look into it.

I haven't had any issues with the regular 91 map, BUT I plan on loading the ACN 91 map today and testing it with 93. I datalogged a hwy run with the regular 91 map and 93 octane, on 6th gear (mostly doing 75-85mph), and only a few times did the feedback knock go to -1.4 (around 2.6k rpm). Just monitoring the gauges, I have only seen it go to -2.8 once.

I don't think I've hit boost over 10psi yet either. I just haven't really banged on this car at all. But I guess the safe thing to do is load ACN 91 and test it for a while with datalogs.
 

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So far everything I can find suggests US and Canadian gas octanes are mostly identical.

This article has more specifics:

"In Canada, octane ratings are calculated using an average, sometimes known in shorthand as the Anti-Knock Index, or AKI.
The AKI is calculated by simply combining the Research Octane Number (RON) and the Motor Octane Number (MON). "


So I guess the answer is yes, Canada uses the (r+m)/2 method for octane rating.
 

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I loaded the ACN 91 tune and test drove it for approx 60 miles. I just drove it normally for the first 30min or so. Feedback knock only registered -1.4.

I did one 3rd gear pull for approx 3 seconds, and this is what that pull datalogged:

329696


If I am reading those stats correctly, it seems that for the first second, the knock sensor dropped -2.8 timing, possibly due to the sudden request for power (and either the ECU playing it safe, or the movement creating phantom knock?). However, as the Throttle stays open and boost increases up to 13.74, timing is actually being brought back up, possibly due to the ECU no longer detecting any knock condition.

So I believe that should be safe? But you guys know better than me. The only other thing I can do is run 94 octane instead of 93.
 

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Just went for another hwy trip, approx 100 miles, with a few hard 2nd and 3rd gear pulls. Knock did not fall below -1.14 the entire time. Motor seems to be ok. I have noticed a tad less responsiveness with ACN 91 map, but it's still a nice kick compared to stock. I'm scared of trying the 17psi Sport# mode, lol.
 

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Discussion Starter · #11 ·
Lmao yeah. Ive kept it on 93 just to see how it goes and logs look quite similar to yours so im not sure whats up. definitely nothing noticeable driving wise as far as smoothness sand responsive ness runs good just not fun seeing those numbers so idk may kick it down a notch like I said I would but every time I go out its like gotta go nowww, so i havent had the chance to try 91. Kinda eyeballing a flex fuel kit but we'll see.
 

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Lmao yeah. Ive kept it on 93 just to see how it goes and logs look quite similar to yours so im not sure whats up. definitely nothing noticeable driving wise as far as smoothness sand responsive ness runs good just not fun seeing those numbers so idk may kick it down a notch like I said I would but every time I go out its like gotta go nowww, so i havent had the chance to try 91. Kinda eyeballing a flex fuel kit but we'll see.
Dude, the information on the web is so confusing. But the gist I seem to get is that for a stock motor, the risk of damage is very low, as long as you're not blasting the car to 7k RPM, or you're not doing any WOT runs in 6th gear (or even 5th gear).

The fear I have is that Subaru probably designed this motor to be at the very edge of stock power. I fear that even with zero detonation, something like a 93 tune on 93 gas, and running the 17psi Sport# setting, is probably begging to grenade the motor. I don't care about squeezing every single drop of power out of this motor, so I'm going to stick to ACN 91 maps and monitor my engine knock and boost levels regularly, etc etc.

Then again, there's people running Stage 4 with catbacks, intakes, and aggressive custom tunes making 400hp+ and their motors seem to be ok?
 

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Discussion Starter · #13 ·
Dude, the information on the web is so confusing. But the gist I seem to get is that for a stock motor, the risk of damage is very low, as long as you're not blasting the car to 7k RPM, or you're not doing any WOT runs in 6th gear (or even 5th gear).

The fear I have is that Subaru probably designed this motor to be at the very edge of stock power. I fear that even with zero detonation, something like a 93 tune on 93 gas, and running the 17psi Sport# setting, is probably begging to grenade the motor. I don't care about squeezing every single drop of power out of this motor, so I'm going to stick to ACN 91 maps and monitor my engine knock and boost levels regularly, etc etc.

Then again, there's people running Stage 4 with catbacks, intakes, and aggressive custom tunes making 400hp+ and their motors seem to be ok?
I would assume so I mean im looking to push it to 350whp so , eh afaik low end torque is a big killer as well so Im sure we'd see more dramatic numbers if there was a real issue. If motor dies ill just buy a built one lmao. I think we're being a bit too paranoid .
 

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I would assume so I mean im looking to push it to 350whp so , eh afaik low end torque is a big killer as well so Im sure we'd see more dramatic numbers if there was a real issue. If motor dies ill just buy a built one lmao. I think we're being a bit too paranoid .
By nature I am paranoid :D but I went thru similar with my Mustang literally 15 years ago. That was a much more growing pains affair, as engine modding and tuning was way more of a wild wild west scene. And those V8's were so crappy (the stock 1995 Mustang V8's making an anemic 180rwhp on the dyno). I knew zero about cars back then and ended up blowing a couple of things. I still have that car sitting right beside my Subie, with a built 347 stroker motor, and a built T5..................................so I can take it out once in a while for a cruise or a car show. If the market wasn't so bad for these cars, I'd even be tempted to sell it. I'm finding the Impreza to be a much better overall driving experience. My Mustang with all it's stuff, is only making around 100hp more than the bone stock 2012 STI engine. That's mind blowing. Then I look at the size of the boxer engine and go "hmm that thing is like a 3rd of the size of my V8, how long until that thing blows?"
 

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91 ACN is made to run the low emissions fuel required in California. Although it's 91 octane its actual quality in performance driving terms is limited. It'll hold your car back, but tunes for it are reserved enough that if you have knock at 91 octane tunes the 91 ACN can help.

Basically it feels sluggish compared to the others because it is.
 

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91 ACN is made to run the low emissions fuel required in California. Although it's 91 octane its actual quality in performance driving terms is limited. It'll hold your car back, but tunes for it are reserved enough that if you have knock at 91 octane tunes the 91 ACN can help.

Basically it feels sluggish compared to the others because it is.
The question for me is: How crappy is Canadian fuel compared to US? It's kind of a theoretical question, because I plan on sticking with ACN91 map and running 93 Octane probably until next May or June. Ideally I would love to rebuild the motor to refresh the bearings, and cylinder crosshatching, etc etc (and replace gaskets/timing belt, etc etc). Is it possible to have basically the same engine but with forged pistons instead?

What will definitely be done asap is the following:

1. the 4-cylinder cooling mod.
2. Compression test to ensure motor is good.

And I think after that I'm calling it a day until next spring.
 

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99.9% of all fuel sold in the first world is top quality. Its all leaving the same refineries, drilled from the same wells, and using the same treatment plants before being sent to the respective brands.

Its the station quality that is the issue.

The cylinder mod is snake oil.

Don't forget a leak down test.
 

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99.9% of all fuel sold in the first world is top quality. Its all leaving the same refineries, drilled from the same wells, and using the same treatment plants before being sent to the respective brands.

Its the station quality that is the issue.

The cylinder mod is snake oil.

Don't forget a leak down test.
After maybe dozens of articles and videos, you're the first one to say the cooling mod is snake oil.

I know Ford V8's also had similar issues with certain cylinders not cooling as well in a stock config (hence Ford releasing the Boss 5.0L motor, which had its rerouted water jackets as a selling feature). So the concept is, in fact, a thing. So I would love to hear your side as to why it's snake oil?
 

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After maybe dozens of articles and videos, you're the first one to say the cooling mod is snake oil.

I know Ford V8's also had similar issues with certain cylinders not cooling as well in a stock config (hence Ford releasing the Boss 5.0L motor, which had its rerouted water jackets as a selling feature). So the concept is, in fact, a thing. So I would love to hear your side as to why it's snake oil?
Thousands of people install intakes without tunes too. Doesn't mean it won't blow the car up. If you are worried about uneven cylinder temps install equal length headers. There is actual proof they help. I have not seen anything from Dom's cyl4 mod that proves anything.
 

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Car is going in for Snake Oil mod, New plugs, compression and leakdown. We'll see what's up after that.
 
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