Car and Driver tests high octane on 1.5T

[arsh88]

it wouldn't make any sense that there's no difference when the sport and sport touring have 6hp more but really component wise the only difference is running premium and the exhaust they have on them, which would suggest most of that 6hp gain is due to running premium over 87.

Sponsored

 

[charleswrivers]

I would regularly agree, but my knock sensor failing on my nissan caused some problems and they go out pretty quickly if you run less than the recommended octane. It's not easy or cheap to fix on most cars so I'm gonna go ahead and say that people should just use what their car calls for.

(shrug) Running 93 all the time certainly doesn’t hurt anything. If you operate under the assumption that your knock sensor could fail anytime and provide a zero signal... then the idea of running 93 all the time has some merit. My old Nissan specifically says, "Required" though. It doesn't really give you leeway. It's 8-bit potato of an ECU cannot dynamically adjust to perform well on 87. If it detects knock... and it will on 87 on a hot day... it's wastegates fail open on safety boost to prevent engine damage... effectively going into limp mode. If our cars operate as designed... it should just pull timing... a little power, but it'd likely be so little, it wouldn't drastically affect performance. If it works. (shrug) It's always up to the owner what they want to do, and we should all do what we feel is best for our cars for our own peace of mind as much as the cars themselves.

The engine, by design, does not need anything higher than 87. Even if the ECU detects it, it won't advance timing or add boost to compensate. It's likely due to the engine's lower compression ratio- that's what I believe dictates what trim of fuel you need. If your engine is a high compression one and you put in low octane gas, it will pre-detonate and cause engine knock. The computer can adjust for this generally, but results in pulled timing and reduced power output. However, a low compression engine gains nothing from getting better fuel. You won't get early detonation if you use 87. The car won't pull timing. Nothing changes if you go up in octane.

I don't think it's so much that a high compression engine creates more power on higher fuel trims, but rather, it creates it's intended power output for 93, and then scales downwards from there (if that makes sense). In the case of the 1.5T, it's making it's intended power on 87. You could have less power from lower octane fuel (assuming you could find it), but not more.

I feel like I'm not explaining this very well, lol. At least I tried, hahaha.

You did decently.

The CRV does have the exact same engine (internally) from anything I've ever read and turbo that the Si has... and is slightly different than the other Civic trims that have the L15B7. It's engine is the lower CR, just like the Si at 10.3:1 vs 10.6:1. It's slightly lower compression than the other trims... and gives up a smidge of thermal efficiency by having a lower CR, but allows for greater power that can be provided by running higher advances/boost levels (which the Si has). Funny enough, the timing advance also raises thermal efficiency back.. allowing the piston to be under force for effectively a longer period of time and while the volume in the combustion chamber is at it's minimum. I want to say the improvement only amount to something like 3-4% at those CR levels per-point... so the efficiency improvements are pretty low. I've seen some charts and my numbers might be a little off... but I'm pretty sure it was only a percent difference... if that. The higher your CR... the less effect each additional point of CR matters.

I've often wondered why the CRV got the Si engine/turbo combo. The engine makes a little sense in some ways... a heavier vehicle with a 1500 lb towing capacity got the engine with slightly stronger internals. Piston choice for lower compression? The lower peak values of the boost targets all point to making the mass market vehicle not having the premium recommendation. I'd of figured, especially w/the CVT as the only option, they'd of gone with the 11-vane turbo for a quicker spool and peak torque a little earlier. Oh well. I guess it allows all CRV turbos be direct swaps for Sis if you need to do a junkyard pull... other wise the HP turbos would stay pretty rare. Barring a more restrictive intake and exhaust, I'd assume you could effectively reflash the Si's tune on a CRV and it'd make the same power. (shrug)

Back on topic: The difference in why the CRV doesn't recommend premium is in the tune... a slightly lower peak boost and less timing advance. That tune is based around 87, as you said... and you're not going to gain much with going with 93. K.cont will further reduce timing advance, based on it's inputs as needed. Even with the higher octane fuel, the potential is lower, so long as it sticks with that tune. So in the CRV and the Si... you are comparing apples to apples in this case, with the sole difference really being the tune. Sustained hard driving is what really moves k.cont though. If they kept doing pull after pull on that CRV with 87 vs 93... I'd bet the difference would be noticeably larger. A throttle stab on the dyno? I'm impressed there was a 7 whp difference.

'By design', you could argue the Si doesn't need 93 octane fuel... and you'd be right. That's why it's a recommendation and not a requirement. There's more than enough margin of timing retard to protect the engine to let you run 87 octane until the clearcoat peels and the car rusts out around the engine. The Si will be down on power somewhat more though, compared to it's potential peak... and would have k.cont spike quicker and higher to prevent knock.

I'd expect the TSP Stage 1 adds so much additional boost and timing advance there simply isn't enough margin left for k.cont to retard timing that the makers feel comfortable with the ECU being able to prevent knock under ALL circumstances (i.e. sustained high load on a stupid hot day with poor-quality 87 octane fuel). That is why on their website, 91/93 octane is specified as a requirement to use their tune.

 

[Axatax]

The knock sensor doesn't come into contact with any internal part of the engine or any fluids. It's just fitted into a bolt-hole in the block that goes nowhere...

 

[Jeezer]

(shrug) Running 93 all the time certainly doesn’t hurt anything. If you operate under the assumption that your knock sensor could fail anytime and provide a zero signal... then the idea of running 93 all the time has some merit. My old Nissan specifically says, "Required" though. It doesn't really give you leeway. It's 8-bit potato of an ECU cannot dynamically adjust to perform well on 87. If it detects knock... and it will on 87 on a hot day... it's wastegates fail open on safety boost to prevent engine damage... effectively going into limp mode. If our cars operate as designed... it should just pull timing... a little power, but it'd likely be so little, it wouldn't drastically affect performance. If it works. (shrug) It's always up to the owner what they want to do, and we should all do what we feel is best for our cars for our own peace of mind as much as the cars themselves.

Yeah you're 100% correct. My (1995) ecu is OBD 2 but it really freaks out when the knock sensor starts to go. If your engine isn't in tip-top shape then it'll fail in 10 or 15,000 miles anyways.It really only affected my mpg in the long run.

The knock sensor doesn't come into contact with any internal part of the engine or any fluids. It's just fitted into a bolt-hole in the block that goes nowhere...

It detects knocks through vibrations in the block. Put a 2x4 piece of wood against the block of your engine and then butt your ear against it. You can very easily hear if your engine is running poorly by doing that.

 

[Axatax]

It detects knocks through vibrations in the block. Put a 2x4 piece of wood against the block of your engine and then butt your ear against it. You can very easily hear if your engine is running poorly by doing that.

Thank you for the education.

I'm not saying it doesn't do anything... It's obviously a critical mechanism required for dynamic timing adjustment. I'm saying there's not any conceivable way low octane gas is going to "break it".

In the bad old days of boosting D-series engines, we'd strap a Radio Shack piezeo-electric buzzer onto the fuel rail and feed it into the knock-sensor input of a D16Y8 ECU. I'm well aquainted to the theory and operation of knock sensors, esp. on theses vehicles.

 

[Jeezer]

Thank you for the education.

I'm not saying it doesn't do anything... It's obviously a critical mechanism required for dynamic timing adjustment. I'm saying there's not any conceivable way low octane gas is going to "break it".

In the bad old days of boosting D-series engines, we'd strap a Radio Shack piezeo-electric buzzer onto the fuel rail and feed it into the knock-sensor input of a D16Y8 ECU. I'm well aquainted to the theory and operation of knock sensors, esp. on theses vehicles.

I might be wrong, but in my experience it seemed like a knocking engine has made my knock sensor literally crack and fall apart into pieces. I used OEM and aftermarket ones (new-in-box OEM sensors for a 1995 were REALLY hard to find) and they all did the same thing, but the OEM ones lasted about twice as long.. which leads me to believe that it's just the nature of the beast. They break to keep other things from breaking.

My engine had well over 300,000 miles so there were certainly some "knocks" that it was accounting for lol.

 

[Axatax]

I might be wrong, but in my experience it seemed like a knocking engine has made my knock sensor literally crack and fall apart into pieces.

I suppose that's possible, *theoretically*, but it stands to reason that other sensors attached to the block like the knock sensor (oil pressure sensor, etc.) and rotating assemblies would be equally impacted if this were so?

I think at 300K it was just the time for that sensor to meet the deuce.

Sensors break in cars because they're somewhat sensitive instruments, and I don't find the claim that knock killed a knock-sensor to be either evidence-based or convincing, but I'm willing to examine the data.

 

[Jeezer]

I suppose that's possible, *theoretically*, but it stands to reason that other sensors attached to the block like the knock sensor (oil pressure sensor, etc.) and rotating assemblies would be equally impacted if this were so?

I think at 300K it was just the time for that sensor to meet the deuce.

Sensors break in cars because they're somewhat sensitive instruments, and I don't find the claim that knock killed a knock-sensor to be either evidence-based or convincing, but I'm willing to examine the data.

I mean yeah, but I was replacing it about every 15,000 miles. It's made out of a softer plastic (almost like poly or rubber) than most sensors and very sensitive to knocks and vibrations. It is designed to turn these knocks into a signal so the thing is going to fail faster if the engine knocks more. If I can find something other than my own experience then I'll link it here, but I'm at work at them moment and a lot of my resources are blocked from here lol. I know that me saying "trust me, I'm an expert" isn't grounds to change your opinion on this but I have replaced over a dozen knock sensors on half a dozen cars and the things they had in common were running 87 octane when it called for at least 91 and a lot of them had a slight knock either just in cold weather or all the time. The knock sensors were always cracked in 5 or 6 places or completely shattered apart.

 

[cjackgo]

This article is badly written to make a point. Their actual numbers show that each of these cars, including the CR-V (8 hp not 7?) gained about the same roughly 5% of power by going from 87 to 93. The BMW gained about half of that going from 91 to 93. No surprise. That's exactly what a modern car with a turbo or reasonably high compression and well-working ignition regulation should get.

This will never be economical if compared to oil companies pricing of premium fuel. But if someone wants badly these additional horses, he doesn't care about 30% more for gasoline or whatever it is. There is really no expectation of the fuel economy increase on premium. Why would it need to increase with more octane?

As for 0-60 times.... it's a complex issue and C&D doesn't seem to fully comprehend it, although they test cars for a living. It simply does not need to necessarily increase linearly with maximum power, or maximum power-to-weight ratio. The whole power and torque curves count, along with many other factors. It's not so easy or quick to test.

Nicely said, I was about to write a similar theme. I have the Civic EXT and about 4th or 5th tankful I buy premium and add a container of Chevron Techron to keep the system, especially the injectors, clean. When i do I notice an increase in response and acceleration. You can tell me I'm full of it, that I don't know what I'm talking about [and I know someone will] but that is my perspective. While the car is designed to run on 87 octane, to me it does no harm to run a tank of 91 every once in while to keep things running cleaner. I have 52Kon the odometer, and no problems, knock wood. This is my forever car [I retire in June], it will be paid off and I will keep it as long as I can.

 

[charleswrivers]

I retire in June

Congratulations!

 

[EJLLee]

[I retire in June], it will be paid off and I will keep it as long as I can.[/QUOTE]

Congratulations on your upcoming retirement. Your car looks awesome.

I’ve noticed over the years that my cars run a tad smoother with the higher octane.

We just got the '20 Civic HB Sport Touring which requires the higher octane . We had a '17 HB (base model). The '20 is an order of magnitude better in almost all aspects. Like you, this is my retirement car.

 

[Slickone]

I read that article when it came out. Here's a link to it.
https://www.caranddriver.com/features/a28565486/honda-cr-v-vs-bmw-m5-ford-f-150-dodge-charger/

It's a puzzlement why its 0-60 and quarter mile times were slower even though the car had 7 HP more. I'm guessing the tests were run on different days under different weather conditions.

Sorry and thanks. I meant to includ the link. Maybe I did. Been having trouble with the forum since they keep making chances.

 

[Iam_zls]

I just got an Ex-T model should I just pump 91 all the time or just from time to time and run 87 mostly? I’m looking to modify it a little bit too so I’m just looking for what will get me the best performance.

Sponsored