2019 Subaru Ascent Mid-sized SUV - True 3-row vehicle

[SBT]

And, that's where it's needed "umpf-wise" and > than the Toyota 3.5L V6's at significantly lower RPM.

[covertrussian]

The HP/TQ ratings are listed as 87 AKI. Not sure if that equivalent to 87 RON US, but it might be. If so, or either way, with Subaru's ECU learning and the availability of 91 or 93 both should enable more HP/TQ on tap running those octane levels.

 

In this case, would it be that the engineers are tuning to the lowest common denominator and anything above that is bonus? I presume that 91/93 will be recommended for highest performance, similar to the FA2.0 DIT.

 

I wouldn't get your hopes up on it being 87 tuned and sticker power rated. Based on my past experience with Subaru, those are 93 numbers

 

For example, My 2012 2.5i is ratted at 170bhp, with 23% drivetrain loss, that's 131whp. With 87 octane (what car calls for), I made around 115whp, which is 150bhp. With 93 octane (and stock tune), I was able to squeeze out right around 130whp.

 

Now I know this is only one car, with 100k miles, but my engine seems to be in really good shape, compression was 182-190psi (more then what manual calls for).

 

AFWIW - the Toyota's NA 3.5L V6 makes 295 hp @ 6660 rpm, 263 lb.-ft. @ 4700 rpm. Those are stratospheric RPMs v-a-v HP numbers. Believe I read somewhere that the Ascent's 2.4 DIT will make it's power and torque between 2,000 and 4,000 RPM.

 

Right the Ascent is gonna be a torque monster, which is good for towing too. Guess we'll see as we get closer to them releasing.

 

I'm still paying for my Outback, so Ascent is out of question for a while. Perhaps by that point they'll release a 6MT 350BHP model?

[ehsnils]

The HP/TQ ratings are listed as 87 AKI. Not sure if that equivalent to 87 RON US, but it might be. If so, or either way, with Subaru's ECU learning and the availability of 91 or 93 both should enable more HP/TQ on tap running those octane levels.

 

How about this post for reference?:

http://legacygt.com/forums/showpost.php?p=1757501&postcount=50

[FLlegacy]

How about this post for reference?:

http://legacygt.com/forums/showpost.php?p=1757501&postcount=50

 

AKI ratings aren't listed how does that help?

[SubieDriver]

I haven't looked lately, but in the past, all pumps in the US would have "R + M / 2" = Research Octane + Motor Octane Divided by 2 to give Pump Octane.

[ehsnils]

AKI ratings aren't listed how does that help?

AKI = PON (Pump Octane Number)

 

I updated the post. Different names for same thing.

 

Here we only use RON, and usually we "only" have 95 or 98 RON to select between.

[SubieDriver]

So your 95 & 98 would be 91 & 94 for us.

I'm sure a lot of people here would be happy to have 94. Usually 93 is the best, with some locations only getting 91.

[ehsnils]

In the 70's we had 100 RON as well, but due to the attempt to lower the amount of lead it was removed then and it hasn't come back in the lead free gasoline.

[eagleeye]

for now the Ascent is a USA/ Canada thing only. to be made in Lafayette Indiana

 

_______.

 

here is a wikipedia page discussing ..the #s that appear on pumps worldwide. (don't know how great the data is, but nice some people worked so hard on it....vs. the subaru pages all screwed up with each of the world's domestic markets piled together like a large shit sandwich )

 

https://en.wikipedia.org/wiki/Octane_rating

 

in the US:

91 is typically the high # on the pump at high altitude places like Denver Colorado, and SanteFe, New Mexico. and it acts like 93 in lower places.

 

___

 

I have been in places in europe where there is only one gas (petrol) choice, and its formulated like US 91.....so I guess if you want more zip then that a jug of octane booster gets dropped in with a fill up.

Edited December 12, 2017 by eagleeye

[SBT]

Yes - NA Market only at this time. Though demand may spread to Europe.

[Brady]

91 is typically the high # on the pump at high altitude places like Denver Colorado, and SanteFe, New Mexico. and it acts like 93 in lower places.

 

It's not that it acts like 93, it's that we don't have enough air density to take advantage of it. If it acted like 93, we'd be able to burn more fuel and have higher power output, but that's not the case.

[SBT]

It's not that it acts like 93, it's that we don't have enough air density to take advantage of it. If it acted like 93, we'd be able to burn more fuel and have higher power output, but that's not the case.

 

I wondered about that coming across country. Was surprised to see only 91 available through the mountain and continental divide/plateau states. Never considered air density as the leading factor.

[ehsnils]

I wondered about that coming across country. Was surprised to see only 91 available through the mountain and continental divide/plateau states. Never considered air density as the leading factor.

But even at higher altitudes it would improve things to have a higher octane if you have a turbocharged engine. More octane - more boost - more fun!

[Brady]

But even at higher altitudes it would improve things to have a higher octane if you have a turbocharged engine. More octane - more boost - more fun!

 

Not really. Very few cars can run enough boost take advantage of higher octane at higher altitudes. Not unless it's pretty well modified. One quirk of altitude is some guys even run E-85 without upgrading injectors. There just isn't enough air density to mix with the fuel.

 

And another way to look at it is the compressor (be it a turbo or supercharger) can only compress as much air as is available to it, and the wastegate operates relative to ambient air pressure, so in Denver, the mean air pressure is about .82 atmospheres or about 12.1 psi vs 1 atm. or 14.7 at sea level.

 

So you'd have to run about 2.5 psi higher in a turbo to get the same power output, but it's also going to be running less efficiently.

 

This was an interesting discussion when I had a compression test about 3 years ago. The guys at the shop were telling me the motor was in rough shape because the cylinders tested 95, 95, 95, 92 but said they should be at least 110 or something per manufacturer. But even they didn't understand that the local air pressure would have an impact on that. I did a little research, said don't machine the heads (or whatever it was they were going to do), had them swap injectors and replace o-rings, and here I am about 3 years later and it's never tripped another CEL for misfire.

 

Think of it this way, if you were compression testing your motor in a vacuum, what would the gauge read after turning it over a few times?

Edited December 14, 2017 by Brady

[ehsnils]

Not really. Very few cars can run enough boost take advantage of higher octane at higher altitudes. Not unless it's pretty well modified.

 

Well, I was just trying to hint that it could make some more room for mods getting more boost.

 

And at a lower air pressure you get lower drag so you could go faster!

[Brady]

And at a lower air pressure you get lower drag so you could go faster!

 

You have no idea how much time I've spent debating this theory in my head. I suspect that the net effect is no change to top speed, but it might take longer to get there.

[SBT]

Air resistance is the square of speed, so at .82 Atmos, it's going to have some affect but likely negligible. As you mentioned, how long it takes you to reach top end, that's going to have an effect.

[SaltySnow]

I have waited for this SUV since 2015. If I ever need a second car and they offer a 6 cylinder, this is it.

[FLlegacy]

I have waited for this SUV since 2015. If I ever need a second car and they offer a 6 cylinder, this is it.

 

Sounds like your wait continues...

[SubieDriver]

I have waited for this SUV since 2015. If I ever need a second car and they offer a 6 cylinder, this is it.

 

The 6-cylinder is dead, replaced by this new 2.4 DIT 4-cylinder.

This could have been my new family vehicle, if it came out two years ago. My wife wrecked our Tribeca so we got a Kia Sedona. It's been great, but maybe someday I'll replace it with the Ascent.

[Brady]

I don't understand why some people are stuck on a cylinder count instead of actual performance.

 

Personally, I don't want anything other than a carbureted cast iron push rod V8. And if it has more than 4 gears, I don't want it! Oh, and Bias Ply tires are just fine!

[covertrussian]

I don't understand why some people are stuck on a cylinder count instead of actual performance.

 

Personally, I don't want anything other than a carbureted cast iron push rod V8. And if it has more than 4 gears, I don't want it! Oh, and Bias Ply tires are just fine!

 

Exactly, I actually prefer less cylinders because it's that many less things to break or needing to be replaced. Plus the back 2 spark plugs on H6's are a pita

[SBT]

No replacement for displacement... and less HP per cylinder = less engine stress + engine longevity.

 

H6 - 256 HP = 42.7 HP/per cylinder NA

H4 - 277 HP = 69.25 HP/per cylinder DIT

 

And transferring torque longitudinally through a longer crank, under heavy loads, puts less stress on the engine block and internal bearing surfaces.

 

That's conventional wisdom.

 

Subaru in their over-engineered approach, with the new 2.4H4 (which is exactly 2/3 of a 3.6H6 - SVX 3.3H6 from the 2.2H4 anyone) have likely overbuilt the 2.4DIT.

 

Either way, my dealership called me today to let me know that they'd be calling me back as soon as they have hard dates/numbers on the Ascent. Told them I'd be ordering it exactly the way I want it, so no need to wait for a dealer one.

[Pilot1226]

I'm curious about the injection type on the new 2.4... I really don't want to have to walnut blast the DI every 60k... it would be great if they borrowed some of the Toyota tech to do Port + Direct Injection to avoid that whole drama. And if it runs off 87 or not. The Turbo 4 costs more to run in fuel costs than the 3.6 does if it requires 91+...

 

I agree they've probably overbuilt it - and that's a good thing.

[Brady]

I'm curious about the injection type on the new 2.4... I really don't want to have to walnut blast the DI every 60k... it would be great if they borrowed some of the Toyota tech to do Port + Direct Injection to avoid that whole drama. And if it runs off 87 or not. The Turbo 4 costs more to run in fuel costs than the 3.6 does if it requires 91+...

 

I agree they've probably overbuilt it - and that's a good thing.

 

Everything I've seen indicates it will run 87 octane pump. Somewhere in this thread there was a translated Subaru of Japan page that specifically called out 87 AKI fuel, which is US 87 pump octane.