| Timing Retard with lower octane fuel (?)
- Click HERE for Original Thread
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| mdxforever |
Theoritically yes but has anyone really gone out and checked with something like an obd-ii scanner (I am sure a few of you probably have it), if timing really retards when using lower octane fuel ?
If you have an obd-ii scanner chances are it has an inbuilt dyno too, which when done right, can give hp and torque measurements as well. |
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| SuperTech |
quote:
Originally posted by mdxforever
If you have an obd-ii scanner chances are it has an inbuilt dyno too, which when done right, can give hp and torque measurements as well.
Not for Honda. Some other brands such as GM that utilize torque management will show power output (in ft. lbs) in the live data stream. |
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| mdxforever |
I have never used one (although am researching which one to get). For vehicles like Honda where the enhanced pid's are not available to a 3rd party scanner, I believe it "computes" the hp and torque based on the weight of the vehicle, acceleration, distance traveled and time.
Much like these little dashboard dynos that have popped up in the market recently -
http://www.escortradar.com/gtimer.htm
http://www.scangauge.com/
Ofcourse a lot of room for error and inconsistency there but for comparison on the same vehicle I'd imagine it might be ok. |
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| Pro Stock John |
You'd have to log timing and baseline it with the spec fuel first.
With some cars the pcms will learn reduced timing, and some will just simply drop into what they call the "low octane table" like the GM cars. |
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| mdxforever |
Hi, bringing back this old thread since I have some new info to share with you.
**this is for '01 so might not apply to '03+ **
I got my new obd-2 reader last week and since then I have been logging quite a lot, especially the timing advance. I have LOTS of numbers scattered all over the place so the data is not in “presentable” form but I have scanned through it and here’s the deal –
Yes it retards the timing with low octane(87) fuel. The surprising find was that even with high octane(92) fuel it does detect knocking sometimes and retards the timing especially in the high rpm range (3k+) and/or when its loaded. Maybe its just the 65000 miles of carbon buildup increasing the compression ratio :8:.
Typical timing numbers with high octane fuel are in the range of 30° to 35° @ 2k-3k rpm. When it senses knock it drops immediately drops it down to 16°-17° then raises it gradually. The good thing is it tries to bring it right back up. So if you'd draw a chart of the timing against "time" you would see a lot more oscillations of the timing retard and advance for a low octane fuel but very less for high octane fuel. y'know what i mean ?
BUT using cruise control on a highway there is little or no difference between low octane or high octane! It holds up pretty good – probably because there is little power demand.
Sit tight, I will post charts and data shortly.
Useless ramble follows -
The only thing I found odd was that at idle the timing on a cold start in the morning was negative(!). Doesn’t that mean its holding off the spark until after TDC ?! After warmup it settles down at about 10°. Not sure at this point if it’s a problem or normal :hmmm:. |
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| G. COLTON |
quote:
Originally posted by mdxforever
Theoritically yes but has anyone really gone out and checked with something like an obd-ii scanner (I am sure a few of you probably have it), if timing really retards when using lower octane fuel ?
If you have an obd-ii scanner chances are it has an inbuilt dyno too, which when done right, can give hp and torque measurements as well.
It cannot give you actual dynamometer data. This can only be accomplished by an external system measuring the real output at the wheels, or where ever you want to measure.
All the dyno information that it can give you is that which is calculated based upon a built in formula.
G |
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| 04mdx4sq |
| I would be interested to see how much less knock / retard you would get after using a top end cleaner (seafoam). On the turbo truck we used it on, (~85k mi) difference was huge. |
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| mdxforever |
well I just seafoam'd it a couple of weeks ago before I got the obd reader, so I dont really have a comparison at this point. But I have some other info for you that you might like - (that reminds me I should update that thread too) - the compression dropped from 235 to 210 so it did make some difference. I also got a 10-15psi drop in compression on the accord.
Having said that, I am not quite satisfied by the cleaning. I used a spare vacuum port on the back of the intake manifold and was cautious with the amount of seafoam I used since I was doing it for the first time, but the position of that port (or for the matter of fact any vaccum port on the mdx) is not well suited for sucking in the seafoam evenly in all cylinders.
I will probably use the 'other' method to do it in about 3k miles or so where you just pour it into the cylinders from the spark plug holes, let it sit for a while, and then drive off. |
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