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Just bought a 2015 3.8 R-spec from a local dealer and I think it may already have a flashed ecu in there. I tested the rev limiter in 2nd gear and it hit about 7500rpm. The only thing I see on the ecu is a number written on the ecu bracket near the bolt, it's "Z90". Unless that's upside down and it's actually "0b2" or "062".

My concern is what octane gas I should be running with this car. I don't want to fill up on 87 and cause any damage to the engine. Do BTR and SFR keep records of customers that I could cross reference with my VIN #?

The car had a Borla cat back and a AF Dynamic intake already installed, and possible other mods that I haven't found yet. Thanks for any advice you guys can give me, just trying to keep it safe.
 

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I talked with BTR today and they said I need the previous owners name for them to look it up in their system, since they don't keep VIN records. He did say they don't write anything on their ecu's, so I'm guessing it's not them. Going to call SFR tomorrow and see if they have any info.

I may have to sweet talk the dealership into giving me info on the person who traded it in, or at least have them call and ask details for me. The search continues I guess.
 

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I called the dealership and asked them to contact the previous owner, since legally they can't give me any information. The guy said it's the stock ecu, never been flashed so I feel a little better now. Looks like I might have got a car that didn't get modded out and ragged on.
 

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I called the dealership and asked them to contact the previous owner, since legally they can't give me any information. The guy said it's the stock ecu, never been flashed so I feel a little better now. Looks like I might have got a car that didn't get modded out and ragged on.
And you will belive dealer knows what he is talking about?

Over 6.8k revlimiter = flashed.
Flashed or not, does not tell you if car was beat on alot. I would run premium, 1 - because it performs better and has better mpg (even unturned), 2 - safe if its tuned.

If you have 3.8, run premium and don't look back. Just make shure you run oil at full or a bit over to prevent oil starvation at 7.5k rpms. 6 qts is what you need (as Hyundai recommends) which is a bit over full.

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Discussion Starter #6
And you will belive dealer knows what he is talking about?

Over 6.8k revlimiter = flashed.
Flashed or not, does not tell you if car was beat on alot. I would run premium, 1 - because it performs better and has better mpg (even unturned), 2 - safe if its tuned.

If you have 3.8, run premium and don't look back. Just make shure you run oil at full or a bit over to prevent oil starvation at 7.5k rpms. 6 qts is what you need (as Hyundai recommends) which is a bit over full.

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Oh no I don't trust the dealership, I only used them to contact the previous owner for me for legal reasons.

I went through a tank of 87 with no issues or detonation so I'm sure it's not tuned. I did notice that 93 seems to pull a little harder under heavy acceleration, but normal driving I can't tell the difference.

The oil level looks good, but I'll keep that in mind for the upcoming oil change. Thanks.
 

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Do these cars just run smoother on higher octane? 87,89,or 94 octane mpg are so close it's barely measurable let alone noticeable.. The difference is in the more octane will give less pre ignition detonation.

I'm new to these cars so that's why I am asking, do these cars get better mpg on super? The only mpg difference I ever noticed with gas was brand. Sunoco in my Camaro I would see about 1mpg diff. Highway. Using Flying J I would go down to normal average. Im getting 27.7 highway now, trip was on I95 from Columbia,MD to Northeast, MD. It was about an hour and 20 minute drive.

Again, new to these cars so just wondering if it's in the programming instead of the gas itself.
 

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Do these cars just run smoother on higher octane? 87,89,or 94 octane mpg are so close it's barely measurable let alone noticeable.. The difference is in the more octane will give less pre ignition detonation.

I'm new to these cars so that's why I am asking, do these cars get better mpg on super? The only mpg difference I ever noticed with gas was brand. Sunoco in my Camaro I would see about 1mpg diff. Highway. Using Flying J I would go down to normal average. Im getting 27.7 highway now, trip was on I95 from Columbia,MD to Northeast, MD. It was about an hour and 20 minute drive.

Again, new to these cars so just wondering if it's in the programming instead of the gas itself.
 

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Octane has mostly affect on power on the top end for 3.8 or under boost with turbo, mpg might pick up small amount.
It is more beneficial for 2.0, might see 20hp difference in hot temps.

What do you have 2.0or 3 8?
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After using 87 for 2 weeks (as long as I had the car!) I filled up with 94 today. I was surprised in the engine running smoother.
So I do see a difference there, it started raining on the way home so I really couldn't check acceleration.
I will see on the mpg in about a week.
 

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After using 87 for 2 weeks (as long as I had the car!) I filled up with 94 today. I was surprised in the engine running smoother.
So I do see a difference there, it started raining on the way home so I really couldn't check acceleration.
I will see on the mpg in about a week.
It will take a bit of time to fully readjust, so full power gain is not felt right away.

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Sorry, I missed your question...I have 3.8

This is my second tank of super 94. The engine runs way way smoother. I was getting hesitation with 87. I had AC on and it's been mid 90s here. Hesitation is gone, car runs completely different enough for me to stick with super.
265 for regular, and 299 with super. I use gas buddy and get 5 cents off each gallon so 2.94 for 94 octane.
 

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Discussion Starter #13
Sounds about right, the difference seems more noticeable in higher temps. I'll use 87 for a long highway trips, but I stick with 93 for daily driving. Costco sells gas pretty cheap around here, usually 20-30 cents cheaper than anyone else. Saves me $5 a tank so it pretty much pays for the costco membership.
 

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If your tuned, always 93, and get a step colder on your plugs. Any reputable tuner will advise that.

Your pump 93 is at minimum E10 ,....its all Craaap.
Interesting. I was reading through the "Build Your 3.8" thread and Titan says colder plugs are not needed.

Spark Plugs
OEM plugs are NGK and they are great plugs. Change them every 30k or so or before you get tuned. No need to run a colder plug, there is absolutely no benefit of doing so and would only be required with a nitrous or turbo build. Gap the plugs to 0.036 (this can be hard since you'll need specific feeler gauge with that size). There is no benefit to running them at 0.040 (please do not run more than 0.040!!).
 

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When I checked the plugs on mine (thank you btw) they are NGK and are already one step colder plug. I'm not 100% sure on how to check and be sure if this car was already tuned. I read if it shifts at 7200 then yes, then I searched that and found others saying that's not true.

Is there a concrete way of knowing? My car does shift at 7200ish and had 1 step colder plugs. I don't see anything on the actual ECM (and I don't think there would have been) saying it is flashed.

Any advice would be appreciated.
Thanks again for the previous information
 

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If you look at the plugs, the correct temp will have the color change from dark to light at the bend of the ground electrode. If the electrode is all dark (tan to black) it is too cold, if it is all light colored (gray to white) it is too hot. Should be tan at the bend.

I run stock OE plugs in my tuned 2L with a BR stage 3 tune and stock turbo.
 

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Any tuner will tell you to get one step colder, BTR/Alpha/SFR, all of them. NA or not. But you go ahead and take solace in doing the minimum.



Enjoy.
1 step closer plugs are never needed on NA 3.8 even with e85 tune and full boltons.
Only if adding turbo or nitrous.
2.0 - depends on who tunes it. SfR tends to put in too much timing so he recommends colder sparks for 2.0. If tuned correctly 2.0 does not need colder plugs with boost staying within turbo efficiency, and plugs regapped.

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