91 vs 87, real difference?

turbosix

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I've run a few tanks of 93 and IMHO there is no real difference in performance, MPG, or "smoothness" (whatever that is) that would justify the $0.40/gal cost difference.
I've seen a lot of rediculous claims on every one of these threads, but have never seen any dyno data to back anything up.
Run good quality fuel and drop a 20oz bottle of Techtron every 5k and you'll be good.
Holy shit lmfaooooo... A bottle of snake oil every 5k?
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turbosix

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The important question hasn't been asked.

What's the upper limit in regards to the timing adjustment of the ECU? Can it advance enough to take advantage of 95 octane? 98? 104?

E85 does wonders in turbo applications, if its tuned for it. I don't believe that the 2.0L is an e85 vehicle, but 3 parts 93 1 part e85 would put ethanol around 30% and octane rating at what, 98? MPG would be kaka but can the injectors push enough fuel and can the ECU advance enough to make use of the extra octane?
It's not even about throwing these on a dyno and measuring HP/TQ numbers. You would want extensive data logging, especially under load, to monitor knock, air fuel ratio, if timing is being pulled, etc.

I have been in the tuning scene and turbo engines for many, many years and I have found that higher octane fuel is always best when it comes to performance, knock, AFR, etc. I data log my ND Miata (tuned) and only run 93 octane gas, it's rather silly to spend this much on a JL Jeep and cheap out on gas.
I didn't get into it because most people on this forum don't even seem to understand they should run 91/93 in their turbo car. I did already make the point about a $50k car and spending like a few dollars more per fill-up. Like it's less difference a tank than one Starbucks coffee but whatever.
 

turbosix

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Just hooked up my obdlink MX.

24psi on a WOT run.. damn. I didn't expect that.
 

DesertFox

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Just hooked up my obdlink MX. 24psi on a WOT run.. damn. I didn't expect that.
Because that is not the boost pressure. The OBD2 reads MAP, not boost. You have to subtract atmospheric pressure, which is ~14.7 psi depending on DA. Your actual boost is about 10 psi. The gauge doesn’t depict fractions of a psi.



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MJM

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So far we have been running premium in ours. Around here, that's 91 octane. According to the dash, it's gotten about 22 mpg over the 800 miles we've gone so far. At that mpg the cost difference isn't worth even trying "regular".
 

YYCSahara

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So far we have been running premium in ours. Around here, that's 91 octane. According to the dash, it's gotten about 22 mpg over the 800 miles we've gone so far. At that mpg the cost difference isn't worth even trying "regular".
Must be regional. I'm the other way around. At my mpg it isn't worth me trying premium gas strictly looking at $. Around here it's close to $20 more per tank to fill it with premium.
 

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Must be regional. I'm the other way around. At my mpg it isn't worth me trying premium gas strictly looking at $. Around here it's close to $20 more per tank to fill it with premium.
$1+ more per gallon seems kind of crazy. It is usually $0.40 - $0.60 more per gallon in most places that I have paid attention.
 

YYCSahara

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$1+ more per gallon seems kind of crazy. It is usually $0.40 - $0.60 more per gallon in most places that I have paid attention.
Yeah, it sucks up here. The spread between regular and premium has grown wider and wider over last couple of years.
 

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Premium cost a bit more here as well. But the JLR only has a 17.5 gallon tank and with the mpg we're getting a few bucks a tank is worth keeping full performance. My wife loves to romp on it. Damn thing scoots when you do.
 

turbosix

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Because that is not the boost pressure. The OBD2 reads MAP, not boost. You have to subtract atmospheric pressure, which is ~14.7 psi depending on DA. Your actual boost is about 10 psi. The gauge doesn’t depict fractions of a psi.



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So you're saying engine off it should read 1bar....

Screenshot_20190826-213035.png
 
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DesertFox

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Believe whatever you want, but what does it read at idle? If it doesn't measure atmospheric, then you should see a negative value...vacuum. But you don’t, instead you see ~8 psi. Subtract atmospheric pressure and you are at 6 psi of vacuum...normal for idle.
 

turbosix

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Believe whatever you want, but what does it read at idle? If it doesn't measure atmospheric, then you should see a negative value...vacuum. But you don’t, instead you see ~8 psi. Subtract atmospheric pressure and you are at 6 psi of vacuum...normal for idle.
Lol

Screenshot_20190826-212953.png
 

DesertFox

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LOL. I don’t know what to tell you, mine shows a positive 8 psi at idle, when I advance the throttle the value increases, it does not drop to zero then increase. This instrument is reading the MAP sensor, the PCM needs to know that value to control the engine at different altitudes and temperatures, not the boost value. Like I said - believe what you want.
 
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