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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain.

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Old 01-06-2013, 02:40 PM   #1
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Naturally aspirated and 87 octane...

So, after reading on the Forced Induction forum about how much boost is safe to run on pump gas, I have a question. If you can run around 5lbs. of boost(roughly) on a stock motor with 93 octane, why couldn't the factory engineers have tuned the stock motor to run on 87 octane? If aftermarket tuners can deal with the increased cylinder pressure using pump gas, it seems that a N/A motor could run on 87 octane, even with 12.5 to 1 compression. I realize that there would be a loss in power, but technically it should be able to be done, right? And yes, I realize its a sports car, and yes, I like all the power I can get, and I don't mind paying for Premium, I was just wondering if its possible, and how much power it would give up. Any tuners ever try this?
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Old 01-06-2013, 02:56 PM   #2
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Why would you even spend the time and money to tune for 87? Its less than 5$ difference to fill up. Since its on average 250$ for a tune. It would be a complete waste of money to detune the car to save a few dollars.

Personally I wish they would just change to 93 octane only everywhere and get rid of this 3 tier bs.

If you want to do a tune to have cheaper fill ups then go with e85, then you get more power and a lower fillup. Actual MPG tho I have seen everywhere from better to worse on the car.

Also people are running 7-8.5 psi on pump gas, maybe more I havent really looked that far.


But Im gonna go with yes.... if you really wanted to spend the money on a tune Im sure someone like Visconti could make a map.
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Old 01-06-2013, 07:36 PM   #3
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between 87 octane and 93 octane you only save $3 per gas tank, if you are that CHEAP go buy another car.
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Old 01-06-2013, 07:46 PM   #4
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Quote:
Originally Posted by zooki View Post
So, after reading on the Forced Induction forum about how much boost is safe to run on pump gas, I have a question. If you can run around 5lbs. of boost(roughly) on a stock motor with 93 octane, why couldn't the factory engineers have tuned the stock motor to run on 87 octane? If aftermarket tuners can deal with the increased cylinder pressure using pump gas, it seems that a N/A motor could run on 87 octane, even with 12.5 to 1 compression. I realize that there would be a loss in power, but technically it should be able to be done, right? And yes, I realize its a sports car, and yes, I like all the power I can get, and I don't mind paying for Premium, I was just wondering if its possible, and how much power it would give up. Any tuners ever try this?
Would you design a motor with fairly nice technology to handicap it to 87 octane? I know I wouldn't. Also, if I can advertise a motor to do 200 crank HP, why would I say no, I want it to be tuned to the cheapest gas, I'm gonna tune it to 87 octane even though then I can only advertise it making 185 crank HP. It just doesn't make any kind of sense.
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Old 01-06-2013, 09:14 PM   #5
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Ok, what part of this:
" I like all the power I can get, and I don't mind paying for Premium, I was just wondering if its possible, and how much power it would give up. Any tuners ever try this?"
did you not understand? I'm not saying I want this, I'm wondering how much power you would actually lose. I'm also not cheap, I stated very clearly that I did not have a problem putting 93 octane gas in my car. It was more of a technical question.

Last edited by zooki; 01-06-2013 at 09:38 PM.
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Old 01-06-2013, 10:18 PM   #6
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Is it really a question worth answering though? I think that is a better question.

If you (factory and tuners) are going to spend the time and money to do it, spend that time to improve it to its best.
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Old 01-06-2013, 10:23 PM   #7
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I'm going to drive backwards to work tomorrow. I wonder what my MPG will be like?
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Old 01-06-2013, 11:01 PM   #8
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Well, here's my train of thought...if the aftermarket can get the electronics to cope with increased cylinder pressures of FI through tuning while still using 93 octane gasoline, why can't the engine be tuned to use 87 octane at the decreased cylinder pressures that a N/A motor has. It's not like 93 octane has any more power potential than 87, in fact it may have less power potential do do its slower burn rate. I think direct injection motors have a lot more leeway in the compression/octane relationship due to the way fuel is introduced into the cylinders. If you can get the same amount of power with lower octane gas, why wouldn't you? I'm talking about from the factory. I wouldn't spend the money on an aftermarket tune to get the motor to produce 200 HP on 87 octane. But I think the factory could do it. So, just to be clear. I am not looking for an aftermarket tune for 87 octane, I am fine with the car the way it is, I have no problem buying 93 octane either. This is just a thought experiment on what I've seen boosted motors doing with 12.5 to 1 compression and pump gas.
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Old 01-06-2013, 11:11 PM   #9
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this motors CR is not for 87
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Old 01-06-2013, 11:20 PM   #10
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Just...nevermind.
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Old 01-06-2013, 11:30 PM   #11
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ha, that was entertaining.
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Old 01-06-2013, 11:35 PM   #12
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i think its a good question
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Old 01-07-2013, 01:04 AM   #13
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When you bought your FR-S/BRZ, the dealer probably put 87 in it and your car didn't blow up. The Mustang 5.0 pulls timing and runs on 87 fine; just less HP. Until we have the software available for logging, we just don't know. The logic might be there now.

I'm not sure if ECUTEK found the memory location where timing is stored. If they did, we can look at the difference between the exptected timing and actual. See if the timing is pulled with 87 octane once pinging is detected. The Turbo Subaru's have a software tool called Learning View that does this.
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Old 01-07-2013, 01:40 AM   #14
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If you really stay off the throttle you might even be able to burn a whole tank of 87 and not have the car misbehave...

It might be possible to save gas money by blending in 1 gallon of E85 into each tank, especially since the motor is direct injected you can raise the knock resistance quite a bit. For best results use a new ignition map of course, but it shouldn't be off by too much.
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Old 01-07-2013, 06:47 AM   #15
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so why the question? that was rediculous. If you can/want to put 93 in your car, then why not just do it? This motor was made to use 93 and thats why its rated at 200 crank. That was a foolish question... Just put what it asks for and your all set. No need to wonder about something you don't/won't do.
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Old 01-07-2013, 09:33 AM   #16
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Quote:
Originally Posted by joop1987 View Post
When you bought your FR-S/BRZ, the dealer probably put 87 in it and your car didn't blow up. The Mustang 5.0 pulls timing and runs on 87 fine; just less HP. Until we have the software available for logging, we just don't know. The logic might be there now.

I'm not sure if ECUTEK found the memory location where timing is stored. If they did, we can look at the difference between the exptected timing and actual. See if the timing is pulled with 87 octane once pinging is detected. The Turbo Subaru's have a software tool called Learning View that does this.

You must have some really shady dealers around you.... The Mustang also isnt running the same compression ratio nor the same type of fuel injection set up.
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Old 01-07-2013, 09:47 AM   #17
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You must have some really shady dealers around you.... The Mustang also isnt running the same compression ratio nor the same type of fuel injection set up.
If the Mustang can do it without direct injection, the FA20 should have no problem with 87.

All car dealerships says the put in premium, but they always put in the cheapest gas they can get.
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Old 01-07-2013, 09:57 AM   #18
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Why 93 octane?

Because race car.
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Old 01-07-2013, 10:23 AM   #19
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Short answer: Yes it will work, and you will lose power.

I know a guy who had his WRX tuned for 87. Thing is, he didn't tell the tuner before the session, just filled it up. Tuner was disappointed with the power he got, and probably spent longer than normal tuning. He was noticeably upset once the guy told him why it was so low. It was a good 87 map, but I recommend informing the tuner of your fuel choice before attempting.
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Old 01-07-2013, 10:27 AM   #20
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Quote:
Originally Posted by joop1987 View Post
If the Mustang can do it without direct injection, the FA20 should have no problem with 87.

All car dealerships says the put in premium, but they always put in the cheapest gas they can get.

If thats what you want to believe thats fine. Most dealers arent like that tho. I saw mine filled up with prem, as have others. I was out walking around looking at used cars and one of the techs were over filling it up.

Also, if they are caught going against correct servicing specs it should be brought up to their supervisors.
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Old 01-07-2013, 11:18 AM   #21
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Never mind guys, sorry for having a curious mind. Please go back to arguing over which air filter makes 1 more HP than another. I appreciate all the thoughtful replies.
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Old 01-07-2013, 11:41 AM   #22
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@zooki.. Not too long ago, I was being absent minded and told the gas station attendant to fill up with $15 regular (87 octane and here in Oregon you cannot pump your own gas). I didn't realize what I said until he gave me the receipt. Guess what happened to the motor? Nothing. It was fine. I just didn't go WOT until it all burned away. I'm nearly certain that Toyota/Subaru have already accounted for the fact that people might do this occasionally. I'm sure the motor can be tuned to run on a lower octane of gas, but (as you prob already know) you will make less power. The motor is high compression. If we were talking about a 8.5:1 motor, different story of course. I have also researched differences in behavior in this regard with iron vs aluminum heads.

Good thought experiment. Just not sure that any tuners would be willing to put much effort into an 87 tune on 12.5:1.
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