| 22350VCPILOT |
I've noticed recently that sometimes while climbing a steep grade, my pilot will harshly downshift into third gear. The best way I can describe the harsh shift is a 'clunk' or 'thud' into gear instead of the normal smooth barely-noticeable shift. My '04 pilot has 103k miles and I've been changing the tranny fluid with Honda ATF Z-1 every 30k since it was brand new.
All of the other gears shift buttery smooth and it only has this hard downshift into third sometimes. Is this something I should have checked out or worry about? |
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| belundy |
Mine '03 did that and thought it was a transmission issue. Fixed a torn front and side motor mount for other reasons (idle roughness, clanging), but noticed on a recent 1000 mile road trip with lots of hills that on the upshift to third, not once did it do the harsh bang.
Note that prior to the mount fixes, I had noticed that the harsh upshift was much worse when the car was on cruise--I assume because the accelerator movement is more rapid than when using your foot.
Also noticed the bang much worse when running 91 octane gas--the engine has higher torque output, but which helps the '03/'04 Pilots from coming out of 5th/4th so often on hills. |
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| N_Jay |
quote:
Originally posted by belundy . . . . . Also noticed the bang much worse when running 91 octane gas--the engine has higher torque output, but which helps the '03/'04 Pilots from coming out of 5th/4th so often on hills. [/B]
No, No!!!!
Not another discussion of the "magic" properties of octane! |
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| belundy |
| A problem with octane? |
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| belundy |
OK, I did a search on "octane" and also N_Jay for your comments on the topic. All interesting.
Here's my experience on the topic.
I would encourage folks to read some engineering white papers on the subject; Motor, MotorAge and maybe some SAE articles still floating out there.
Wiki has a very decent article on OCTANE.
If you have access to a logging scan tool, the measured parameters for an engine that was designed (compression ratio, timing strategy and knock sensor feedback) to leverage higher octane fuel can be quite enlightening. The Pilot 3.5L appears to be such a beast, as the owner's manual hints.
For the Pilot using non-ethanol 92 octane gas, there is a palpable difference in lower RPM torque, which is directly noticed in transmission behavior because less throttle angle change is required to maintain speed on hills.
As for gas mileage improvement, it is apparently highly gas formulation driven with apparently wide variations in energy content with same self-ignition (octane) rating. I didn't find the 1.5 mpg (Texas summer formulation fuel) improvement worth the price difference. |
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| 75blazer |
quote:
Originally posted by belundy
OK, I did a search on "octane" and also N_Jay for your comments on the topic. All interesting.
Here's my experience on the topic.
I would encourage folks to read some engineering white papers on the subject; Motor, MotorAge and maybe some SAE articles still floating out there.
Wiki has a very decent article on OCTANE.
If you have access to a logging scan tool, the measured parameters for an engine that was designed (compression ratio, timing strategy and knock sensor feedback) to leverage higher octane fuel can be quite enlightening. The Pilot 3.5L appears to be such a beast, as the owner's manual hints.
For the Pilot using non-ethanol 92 octane gas, there is a palpable difference in lower RPM torque, which is directly noticed in transmission behavior because less throttle angle change is required to maintain speed on hills.
As for gas mileage improvement, it is apparently highly gas formulation driven with apparently wide variations in energy content with same self-ignition (octane) rating. I didn't find the 1.5 mpg (Texas summer formulation fuel) improvement worth the price difference.
So I read the wiki page pertaining to octane, and my take on it was that it had more to do with engine tuning rather than the octane. In other words a high performance engine with high compression needs a higher octane to prevent detonation, but the higher octane fuel doesn't have a higher energy content. Here's an example from the wiki page.
"Using a fuel with a higher octane lets an engine run at a higher compression ratio without having problems with knock. Actual compression in the combustion chamber is determined by the compression ratio as well as the amount of air restriction in the intake manifold (manifold vacuum) as well as the barometric pressure, which is a function of elevation and weather conditions.
Compression is directly related to power (see engine tuning), so engines that require higher octane usually deliver more power."
Another tid bit from wiki...
"A common understanding that may apply in only limited circumstances amongst petrol consumers is that adding a higher octane fuel to a vehicle's engine will increase its performance and/or lessen its fuel consumption; this may be false under most conditions — while engines perform best when using fuel with the octane rating for which they were designed and any increase in performance by using a fuel with a different octane rating is minimal or even imaginary..."
Also, if the octane rating of a fuel really did make a difference, don't you think the oil companies would be promoting the heck out of it rather than saying it won't?
From Exxon, see link below.
"Ordinarily, your vehicle will not benefit from using a higher octane than is recommended in the owner's manual. But if your engine knocks or pings at the recommended octane level, you may need a higher octane gasoline to prevent the knock."
http://www.exxon.com/USA-English/GF...asoline_FAQ.asp |
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| belundy |
all true. Don't want this to start a re-hash of several threads that deal with this. My original point was the Pilot is designed to take advantage (measurable timing remap) of the higher octane fuel to improve especially low RPM torque.
It *runs* just fine on cheap 87, which is what I put in for around town. But when loaded to the gills and on interstate, I'll prefer non-ethanol 91/92. Gets a tick better gas mileage and stays in 5th/4th more.
One side note: Honda quietly changed the Pilot gear ratios in 2005 for shorter overall ratios (notably in 4th and 5th) maybe from complaints of tranny gear hunting on hilly freeways. |
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| 75blazer |
quote:
Originally posted by belundy
all true. Don't want this to start a re-hash of several threads that deal with this. My original point was the Pilot is designed to take advantage (measurable timing remap) of the higher octane fuel to improve especially low RPM torque.
It *runs* just fine on cheap 87, which is what I put in for around town. But when loaded to the gills and on interstate, I'll prefer non-ethanol 91/92. Gets a tick better gas mileage and stays in 5th/4th more.
One side note: Honda quietly changed the Pilot gear ratios in 2005 for shorter overall ratios (notably in 4th and 5th) maybe from complaints of tranny gear hunting on hilly freeways.
I wish we could get non-ethanol gas here in Chicago.... |
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