How much is everyone paying for petrol?, page 3
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reply posted on 3-5-2006 @ 05:42 PM by bigx01
Originally posted by Desert Dawg





I would argue the point that a modern, computer controlled stick shift can be made to ping moreso than the same car/engine with an automatic would.
In either case, the knock sensor hears what's going on and backs the timing off to compensate.
The knock sensor is much more sensitive than the human ear.


I've had no problems with winter gas when we experience a sudden heat wave.
Higher gas mileage in such a situation hasn't happened either.



your right the knock sensor can pick it up before you hear it, but then it's also knocking below the threshold of your hearing all the time. they run the car lean and advance the timing to reduce emmisions and increase milage. you can confuse the computer in a manual easier that an auto. ever drive the early computer controlled FI's. ever have them do a little lurching in second? stop some where and play with the clutch and throttle, starting from a stopped condition. you'll get it to do an audiable knock. usually it's only one before the computer catches it. sometimes one and a softer one.

i can get any fi manual to knock when its at idle. it's all practice and easy to confuse the computer with the load change. practice a little and everyone can do it in any car.

do you know how to get abs to lock up? i can get abs confused enough to lock up. it's rather fun to do. just find one of those rail road crossings with the seel plates between the track. when its wet hit the brakes. abs will try and keep the wheel's from locking and as soon as you hit pavement they will suddenly grab and lock then release and grab and lock. it's an interesting thing to try when there's no one in front of you.

i happen to know a thing or two about distillation of hydrocarbons and what boils at what temp and pressure. lets just say i have operational experience with the distilation of hydrocarbons

vapor lock can and does happen with an electric fuel pump, if it has to pull gas from the tank and the rvp is to high then you'll only be pulling vapors. remember the lower the pressure, the lower the temp things boil at, give off more vapor, when your suction is lowering the pressure . if the pump is in the tank then it wont. although. with the summer rvp at only 11.5 psi (as low as 9psi in some places) then you probably wont have it happen. winter rvp can be as high as 15psi and as low as 13.5 psi.






[edit on 3-5-2006 by bigx01]


reply posted on 4-5-2006 @ 08:55 AM by Desert Dawg
Originally posted by bigx01

i can get any fi manual to knock when its at idle. it's all practice and easy to confuse the computer with the load change. practice a little and everyone can do it in any car.

i happen to know a thing or two about distillation of hydrocarbons and what boils at what temp and pressure. lets just say i have operational experience with the distilation of hydrocarbons

vapor lock can and does happen with an electric fuel pump, if it has to pull gas from the tank and the rvp is to high then you'll only be pulling vapors. remember the lower the pressure, the lower the temp things boil at, give off more vapor, when your suction is lowering the pressure . if the pump is in the tank then it wont. although. with the summer rvp at only 11.5 psi (as low as 9psi in some places) then you probably wont have it happen. winter rvp can be as high as 15psi and as low as 13.5 psi.

[edit on 3-5-2006 by bigx01]



Being able to trick the computer and get the car to ping strikes me as interesting, but not particularly useful.

I agree that you can get vapor lock with an electric fuel pump.
Especially so when the pump is mounted forward and perhaps up on the firewall.
All of the electric fuel pumps I've dealt with - and that's most of them - recommend the pump be installed to the rear so it's pushing fuel instead of pulling it.
If the pump is gravity (as in a drag race car with it's tank outlets at the bottom of the fuel cell) fed or siphon fed (top outlet tank or fuel cell) the pump has fuel at the inlet and has only to push it up to carb or injectors.

I've never had vapor lock with a rear mounted electric pump.


Anyway, it looks like you're a part of the refining process.
I believe California is still using MTBE in their gasoline.
After what, four years or so of being outlawed by then governor Gray Davis?
With the proviso that the refineries could use up remaining stocks of MTBE.
They must have had a lot of it on hand.

I note that MTBE gasoline gets just about 10% less mileage than does straight gasoline.
That was true in both of my vehicles.
It was easy to track because I use gas mileage as an indicator of how well the engine's running.

Since MTBE didn't clean up the exhaust 10% and things only improved a couple of percent - if that - from what I understand, the only reason for MTBE was as a profit boost for the oil companies.

Not to mention that MTBE is such a fierce polluter of the water table.
It enters the water supply and doesn't go away in any reasonable length of time.

As a small aside and taking note of the recently retired Exxon CEO's 400 million dollar retirement package I see that one of the retirement perks was that Exxon continue to pay his country club fees.

What a frickin cheapskate.
400 mill and he can't cough up his own country club fees?
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