WRX STI: running lower octane?

[DonM]

Buddy STI is coming in soon and he was wondering what would happen if he ran lower then 91 octane? The car should run 91 or higher which is understandable.

This is just a curious question.

My responce was it may cause the engine to to knock or ping but is unlikely!?? Being that it's such a high performance car and I was under the impression that most newer cars that run on 91 or higher have extremly good CPU that prevent things like this even when running lower octane? So would running lower octane harm the engine???

Can some one please fill me in on this?

Thanks

 

[Hartman]

The engine probably won't run as smooth, it might idle rougher, and it will still probably knock and ping.

Why is he going cheap on the gas? Is it because he needs money for the radio and the floormats that the WRX STi doesn't come with?

 

[DonM]

No, it was somthing he was just wondering. He's going to run 91 or higher, it was just a curious question.

Either way, will it harm the engine any?

 

[Hartman]

If the manual says to use 91 octane, I would run 91 octane. I'm sure you could do some damage to the engine if you used 89 octane for a long period of time. I don't see why anyone would want to take a risk like that, especially on a limited production vehicle such as the WRX STi.

 

[terdrocket]

Usually if you run lower octane on a turbo like that, the computer adjusts to eliminate pinging. This causes reduced horsepower.

At least thats the way it was in my A4.

 

[DocVijay]

Originally posted by terdrocket
Usually if you run lower octane on a turbo like that, the computer adjusts to eliminate pinging. This causes reduced horsepower.

At least thats the way it was in my A4.

Yep, most modern turbo cars have a program to compensate for lower octane gas. What I want to know is why? If you're going to buy an STi, use the right gas. Don't get cheap now!

It shouldn't hurt the engine at all, but the anti-knock system isn't foolproof. Tell him not to risk it.

 

[gumarcel]

Tell your friend he should cancel his STI order and get a WRX. The after market parts are going to have more for a WRX then an STi. The WRX is much easier to mod then the STi. I have driven both, the STi being a jap version that was right hand drive and it was not all that much quicker then the regular WRX.

 

[DocVijay]

I don't know about that. 300hp vs 227hp. Upgraded suspension that is as good as most aftermarket kits, other than the $5000 Rally DMS systems. It's a fine car, and is much quicker than the regular WRX. Also, the aftermarket parts are already out there. They have them all over in Japan, and it's only a matter of time before someone brings them here.

Keep the STi.

 

[gumarcel]

Well I did drive one that had 280, but the thing is that the STi is much more $$$ and you could get after market stuff for less then it would cost you to buy the STi. For example, my friend bought a 02 WRX used for about 23k. A new STi will run about 32. So right there you could get a new turbo and everything for less than the STi. Just my $00000.02

 

[DonM]

What? I just saw both cars race at the track a couple weekends ago. The STI smoked the WRX.

Both were stock.

Well worth the extra cash for an STI.

 

[gumarcel]

But do you know how well either were modified? That makes a huge difference!

 

[DonM]

stock

 

[Magicfan25]

I would NOT run anything less than 91 on a boosted car.
I personally would NOT depend on a knock sensor. Over time even with the sensor you're asking for a blown motor. A little detonation here and there is gonna weaken things over time. If you dont want a rod through the block, I wouldnt run cheap gas.

 

[DocVijay]

Originally posted by gumarcel
Well I did drive one that had 280, but the thing is that the STi is much more $$$ and you could get after market stuff for less then it would cost you to buy the STi. For example, my friend bought a 02 WRX used for about 23k. A new STi will run about 32. So right there you could get a new turbo and everything for less than the STi. Just my $00000.02

Yes, you are certainly correct in that respect, but I'll counter with two words:

Factory Warranty


There are mods that you could do to either, but a larger turbo would immediately void your warranty.

 

[B94Sport]

Originally posted by gumarcel
Well I did drive one that had 280, but the thing is that the STi is much more $$$ and you could get after market stuff for less then it would cost you to buy the STi. For example, my friend bought a 02 WRX used for about 23k. A new STi will run about 32. So right there you could get a new turbo and everything for less than the STi. Just my $00000.02

The one that you drove with 280 HP was a JDM STi... This STi that is being released in North America is almost completely different... The biggest difference is the fact that the North American version has a 2.5 liter engine, whereas the JDM version has a 2.0 liter engine.

Now, because of my interest in buying a new WRX, I have been spending probably the past 6 months learning about them... Here's why the STi is worth every penny:

MSRP is $31,545 for an STi, and $25,045 for the WRX...
For the $6.5K difference in price, the STi gets:

1. An extra .5 liters of displacement. A heavily modded WRX that is still reliable will usually get about 400 HP out of the engine... 200 hp/liter... This gives the STi a 500 HP potential, but waaaay more torque. Add to that the fact that it has AVCS, which the WRX does not.

2. A 6 speed transmission. The 5 speed Subaru transmission used for the WRX is known to be somewhat fragile, as it was designed during a time when Subaru's vehicles had about 100 HP. The 6 speed, on the other hand, is heavily reinforced and practically bulletproof.

3. A DCCD that lets the driver adjust the amount of power going to the front and rear wheels.

4. An intercooler water sprayer that can be either automatic or manual.

5. A mechanical limited slip rear differential.

6. A viscous limited slip front differential.

7. A more advanced ABS system, the ability to vary braking at each wheel, and Brembo brakes.

8. HID headlights.

9. An IHI VF-30 turbocharger. This is the turbocharger that the stock WRXs usually upgrade to to run higher (greater than 16 PSI) boost.

And some other little things...

NO WAY Could you get all of that into a regular WRX for $6,500, and I am willing to bet you couldn't do it for the difference in price between a used WRX and a new STi. The 6 speed transmission alone costs $5,000 from a dealer.

Basically, I would buy the STi over the WRX in a hearbeat if I could afford it and the insurance. I'm just going to take a WRX now, mod it, and buy an STi a few years down the road.

 

[gumarcel]

I would say get an Evo not an STi, I just opened the newest motor trend and they have the stats for the STi vs the Evo. the STi 0-60 in 4.87, Evo 4.59. Quarter mile time STi 13.23@104.6, Evo 13.08@105.1. 60-0 braking STi 111ft, Evo 106ft. 600-ft slalom STi 69.1, Evo 71.4. I would vote the for Evo!!!!

 

[B94Sport]

Eh... I think the Evo is already pretty much maxed out. The differences between them out of the box performance wise are very small, and I think the STi has more tuning potential than the Evo. Plus I hate altezza taillights.

 

[DonM]

Originally posted by gumarcel
I would say get an Evo not an STi, I just opened the newest motor trend and they have the stats for the STi vs the Evo. the STi 0-60 in 4.87, Evo 4.59. Quarter mile time STi 13.23@104.6, Evo 13.08@105.1. 60-0 braking STi 111ft, Evo 106ft. 600-ft slalom STi 69.1, Evo 71.4. I would vote the for Evo!!!!

Is that the European/Japanese version? Or US?

 

[gumarcel]

US

 

[DonM]

Thanks