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Discussion Starter #1
As promised, I have just completed my second dyno test to determine whether the V-6 engine in my 2005 Frontier really makes more power on 93-octane gas than it does on regular. A few weeks ago I ran a dyno test on 87-octane gas for a baseline; next I ran a couple of tanks of premium to allow the ecm to adjust, then I did another dyno test for comparison. For the results and graphs look here:
premium vs. regular dyno test
 

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Reverendbiker said:
As promised, I have just completed my second dyno test to determine whether the V-6 engine in my 2005 Frontier really makes more power on 93-octane gas than it does on regular. A few weeks ago I ran a dyno test on 87-octane gas for a baseline; next I ran a couple of tanks of premium to allow the ecm to adjust, then I did another dyno test for comparison. For the results and graphs look here:
premium vs. regular dyno test
Nice work! Stick with 87.
 

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Reverendbiker said:
As promised, I have just completed my second dyno test to determine whether the V-6 engine in my 2005 Frontier really makes more power on 93-octane gas than it does on regular. A few weeks ago I ran a dyno test on 87-octane gas for a baseline; next I ran a couple of tanks of premium to allow the ecm to adjust, then I did another dyno test for comparison. For the results and graphs look here:
premium vs. regular dyno test
Actual Real Numbers! Ya gotta love it.

Thanks.
 

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Discussion Starter #6
Dirk Diggler said:
That makes no sense... perhaps the ECU didn't advance timing for the premium fuel?? I have no idea...

Joe.
To tell you the truth, it doesn't surprise me all that much. I've had considerable experience with ecm-controlled vehicles that would back off the timing when a lower-octane fuel was used, but I've never seen the reverse. It appears that Nissan has tuned this engine to achieve at least 265 crank HP (and that looks to be conservative) on 87-octane fuel, and the use of premium won't make a big increase in performance.
I've run many dyno tests on cars and bikes, and I know that there is a margin of error. Correction factors help, but no test is exact. Even assuming that the first test was high and the second test was low, the difference between the two would be very small. My truck runs great, with no sign of knock, on 87-octane gas. If I could pick up 10 RWHP by using premium I might consider shelling out an additional $4 per tank, but for results this close I'll be buying the regular stuff and snickering at the 2005 Tacoma owners.
 

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Good work.
I disagree with your conclusions, though.
To me it looks like there are significant horsepower gains down at the low end--10 whp at 3500 and even more between there and 3750. I have an automatic and that's where I do most of my driving. To me that's definitely worth it. I mean a $100 intake can get you maybe 5 whp and an exhaust costing several hundred maybe another 5 hp?
To each his own, I guess.
 

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Discussion Starter #8
Conner said:
Good work.
I disagree with your conclusions, though.
To me it looks like there are significant horsepower gains down at the low end--10 whp at 3500 and even more between there and 3750. I have an automatic and that's where I do most of my driving. To me that's definitely worth it. I mean a $100 intake can get you maybe 5 whp and an exhaust costing several hundred maybe another 5 hp?
To each his own, I guess.
I probably didn't do a very good job of explaining the testing process. You might notice on the graphs that there are no readings below 3300 RPM, and the readings weren't very accurate before 3700 RPM. Auto trans vehicles are just more difficult to test, and since we tested in third gear we had to roll-on really slowly and easily below 3700 to keep it from downshifting and ruining the reading. Above 3700 we could pretty well let the hammer down all the way to 5750, where it shut down. By the way, at that point the rev limiter didn't shut us down but the speed limiter was at 107-108 MPH and that was what kicked in. Believe me, there were no real advantages for the 93-octane tank in the 3500-3750 RPM range. Even if there were, I can't see that a performance enthusiast would pay premium prices to get even 10 HP in such a narrow power range.
 

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Discussion Starter #10
Conner said:
I'm with you now. I always wondered if it was possible to dyno an automatic.
Possible, but more difficult. My last truck was a 5-speed--just work it up to 4th, then stand on the throttle. You get a much cleaner graph and more accurate readings on the low end. We tried a run in 2nd gear but it compacted the graph too much. To tell the truth, I'd like to see how much low-end torque these VQ engines have. By the way, you're a neighbor--I'm up in Georgetown.
 

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Discussion Starter #12
Conner said:
No kidding? I work in Austin but I actually live right up here in Cedar Park. Where do you go to get on the dyno?
I have my dyno work done at Colvin Automotive in Austin. They are nationally known, and were recently featured on an edition of "Overhaulin" when they helped build and dyno-tuned a 1970 GTO for Lance Armstrong. Their dyno operator, Daniel is an ace and has done many tests for me. It's worth going to their shop just to drool over the exotic and performance cars in the garage.
 

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I think the advantages with premium fuel will be more evident in the real world though. Most dyno tests are done with the hood open and lots of cool air flowing into the engine bay. In the real world the hood is closed, and summer temperatures can really get the under hood temperatures up there. When you have high ambinet temperatures you're more likely to get detonation (spark knock) - causing the ECU to redard the timing advance to eliminate it when it detects it via the knock sensors. Of course, that will reduce HP.

In other words, the advantage of premium fuel may not show up until it's 75F+ outside and the engine is subjected to stop and go traffic.

Heath
 

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Discussion Starter #14
1997XETruck said:
I think the advantages with premium fuel will be more evident in the real world though. Most dyno tests are done with the hood open and lots of cool air flowing into the engine bay. In the real world the hood is closed, and summer temperatures can really get the under hood temperatures up there. When you have high ambinet temperatures you're more likely to get detonation (spark knock) - causing the ECU to redard the timing advance to eliminate it when it detects it via the knock sensors. Of course, that will reduce HP.

In other words, the advantage of premium fuel may not show up until it's 75F+ outside and the engine is subjected to stop and go traffic.

Heath
Actually, just the opposite occurs. One of the problems with dyno testing is that successive runs tend to show less power because the engine gets hotter and the cooling fan in an enclosed area just doesn't cool as well as does real-world driving. Underhood temperatures have little or nothing to do with the ecm--it gets 80% of its information from the MAF, which draws air from the outside of the engine compartment. I realize that many people desperately want to believe that using higher octane fuel will add performance to an engine designed to operate on regular, but the fact is that there is absolutely not a shred of evidence that shows it to be true.
 

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First off... nice web site... great work, but

dyno conditions could also make the small difference...

did you run a couple tank fulls before testing?

I have to question the results...weather that's due to methods, dyno procedure, or the vehicle. not sure.. But it's been shown time and time again higher octanes like 92/93 octane will produce higher numbers than rock bottom 87 octane and even higher returns on race octanes like 100+.

Now of course these differences are highlighted in high performance platforms...

Even if you throw all that out and call it a draw for conversation... Then the premium grade is still better due the refinement process... a lot less particular matter like gums etc... over the long run it makes a big difference.

Also you can't measure MPG on the Dyno
 

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Plus I think you're throwing out the lower RPM gains and not really sheding the proper amount of test material showing those areas. You do mention gains in the lower areas, however it's never explained.

99.9% of people drive in those lower rpm ranges, not the peak area. Rarely do average drivers even come close to hitting the rpm cut off area.
 

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Discussion Starter #17
myoung said:
First off... nice web site... great work, but

dyno conditions could also make the small difference...

did you run a couple tank fulls before testing?

I have to question the results...weather that's due to methods, dyno procedure, or the vehicle. not sure.. But it's been shown time and time again higher octanes like 92/93 octane will produce higher numbers than rock bottom 87 octane and even higher returns on race octanes like 100+.

Now of course these differences are highlighted in high performance platforms...

Even if you throw all that out and call it a draw for conversation... Then the premium grade is still better due the refinement process... a lot less particular matter like gums etc... over the long run it makes a big difference.

Also you can't measure MPG on the Dyno
Gee, did you even read the info I posted on my site? Let me address your concerns one at a time:
1. As I stated on the web site, dyno tests do have a margin of error. I use one of the best operators in the country, but any machine can have variances (all runs were SAE corrected for humidity, ambient air temp, and atmospheric pressure). Even allowing for a high reading on the baseline run and a low reading on the 93-octane run the variance would be very small, no more than 3-5%--an amount the average owner couldn't even feel.
2. As stated on the web site, I ran the test with 87-octane then ran several tanks of 93-octane (over 1200 miles, actually) to allow the ecm to adjust.
3. Where has it been shown time and again that premium fuel produces higher horsepower IN AN ENGINE DESIGNED TO RUN ON REGULAR? If you have that info, produce it. I can give you many quality references that show quite the opposite--that using fuel that is higher octane than recommended for an ecm-controlled engine is essentially a waste of money. Sure, 100+ octane is used in performance cars, but the compression and timing demand it. Very few vehicles have an ecm that can actually advance timing to take advantage of fuel higher than recommended; my objective was to see if the VQ40 was one of them.
4. "the premium grade is better due to the refinement process". Where did you get that idea? Oil company ads might have you believe it, but there is nothing inherently superior in premium fuel . SOME premium gasolines contain higher levels of additives, but the government requires that all gasoline sold in the US contains detergent additives. If an owner is concerned about clogged injectors it's much cheaper to add a can of injector cleaner every 6 month or so than to pay an extra $4 per tank for premium gas.
5. "you can't measure MPG on the dyno". Apparently you missed my fuel economy test (see the web site). I carefully compared tanks 93-octane and 87-octane gas in a tightly-controlled test loop for over 2,000 miles. The results? Premium fuel yielded 1.4% better mileage but costs about 10% more--hardly a good trade-off.
I'm not looking to start a quarrel here. I'm an ASE-certified mechanic with over 40 years experience wrenching on performance cars and motorcycles. I hear a load of opinions on the boards but precious little factual evidence; my aim was to provide the best information possible and share it with the other members. If one chooses not to believe it, then that's his prerogative.
 

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Discussion Starter #18
myoung said:
Plus I think you're throwing out the lower RPM gains and not really sheding the proper amount of test material showing those areas. You do mention gains in the lower areas, however it's never explained.

99.9% of people drive in those lower rpm ranges, not the peak area. Rarely do average drivers even come close to hitting the rpm cut off area.
Have you read this entire thread? If not, please refer back to response #8. Because the truck is an automatic transmission it is very difficult to get accurate readings in the lower RPMs; comparable runs were available only above 3700 RPM or so. Granted, most street driving is done in lower RPM ranges, but we had no reason to believe that the 93-octane fuel would provide any gains there since it provided no gains anywhere else on the power band.
 

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Reverendbiker said:
4. "the premium grade is better due to the refinement process". Where did you get that idea? Oil company ads might have you believe it, but there is nothing inherently superior in premium fuel . SOME premium gasolines contain higher levels of additives, but the government requires that all gasoline sold in the US contains detergent additives.
no reason to get rude simply because someone disagrees with you.

To answer, Where do I get this idea from? I get that idea from seeing lab spec sheets almost every day on gasoline blends throught the US.

Yes some brands do contain higher precentages of additives and some brands are less quality. Like every product on the consumer market, some are better than others.

Yes, The federal government does have standards, But some states have higher standards than the Fed standards. Some additives are used regionally not nationally.

I wasn't refering to additives per say..
Even so, higher grade gasolines have higher gravities, better Reid vapor pressure readings, less sulpher ppm..etc.etc..... the list goes on as to why at the chemical level the premium gasoline is better. If you've ever seen a break down side by side then you wouldn't argue this point...it's obvious.

I was referring to particulate matter..ie crap in the gasoline.. You don't think that one gasoline brand can sell for 10 cents cheaper because they don't want to make as much profit do you?? of course not..they can sell it cheaper because it's cheaper to produce the lower quality fuel...

I'm not arguing the fact that you obtained these numbers... that's fine.. but there is no way you can show any data to prove the statment "Cheap 87 octane is just as good as high priced premium"
 

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Reverendbiker said:
Granted, most street driving is done in lower RPM ranges, but we had no reason to believe that the 93-octane fuel would provide any gains there since it provided no gains anywhere else on the power band.
In a scientific result you can't just throw that out..

I understand it's an automatic and it's difficult to test in that range.. But you have to agree the data is flawed if frequently used areas of the power band are absent.

I actually applauded your website and appreciate the work, but you have to understand this is one test on one vehicle, to make broad statement on all is a bit over reaching.
 
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