Fw: [Diy_efi] The Hunt effect

Mike niche
Mon Oct 10 03:42:47 UTC 2005


At 08:44 AM 10/10/05, you wrote:
>Hi Geoff
>
>Does this apply when Premium ULP (98 octane) in Perth is between 8 to 10 cents per litre dearer than standard ULP (93 octane). I have 5 lt V8 VN that is giving a freeway mileage (kilometerage???) of 12.7 l/100 km on standard ULP driven hard. Do you think I would see at that rate any cost benefit in moving to Premium ULP.

I'd give it a whirl Don but not the BP 98 octane, just the Shell 95-96 Optimax first
 - oh *and* give that lead foot to Jenny Craig's sister ;-)

btw: Ive upped my tire pressures to 32psi on all 4 front tyres, 36 psi for
rear two inside tyres and 32 psi for rear outside tyres, that felt better,
used to have it 5psi or so lower :)

Mike




>Don
>
>Geoff Harrison wrote:
>
>>On  Tuesday, October 04, 2005 9:12 AM
>>DH wrote
>>
>>
>>>Took a trip to Washington a couple of weekends back.  Told my Prius driving
>>>Texas friend (From Austin) that he should start purchasing 89 instead of 87
>>>octane.  That's 'cause it would cost him less.  Well, partner, he said he
>>>would try it if I paid the bill, which I did.  We shared driving duties and
>>>sure 'nuff the car got 51 mpg instead of the previous 48 mpg.  We did this
>>>averaging over 80 mph (while moving) and with two drivers.
>>>How does 3mpg save money?  Well that is 3mpg divided by 48mpg which is a
>>>whopping 6.25% improvement.  Big deal? Well yes!  You see that gas cost 10
>>>cents more per gallon which is 3.22% more.  Since I'm an accountant I
>>>noticed that the 3% increase in cost (because gas is quite expensive now)
>>>was giving a 6% increase in mileage.  That, folks, is a 3% reduction in gas
>>>price per mile.
>>>
>>>Don't mean squat in a non-computer controlled car, but in engines that have
>>>high compression (over 8.5:1) and 'bouncing' engine management (where the
>>>ignition is repeatedly advanced until the engine pings and retarded
>>>slightly) you can expect the same gains.
>>>
>>>Please, try this for yourself and report the results.  Especially those of
>>>you that have a consistent route to work and don't run into a lot of traffic
>>>in-route (both of you).  Report your results here, in public.
>>>
>>>In reality, it should also work for even older engines with lower
>>>compression.  I first noticed the effect with an 83 Olds with computer
>>>controlled carburetor and that was NOT a sophisticated engine control
>>>system.  With that car the engine got about 6% better fuel mileage making it
>>>breakeven even at $1.50 per gallon.  With the wonderful side effect of being
>>>able to pull the hills of North Alabama without pinging.
>>>
>>>I call this phenomenon the Hunt Effect.
>>>
>>>dh
>>
>>
>>I became aware of this about 3 years ago. The company I worked for paid for
>>my fuel. They whinged because I was using Caltex Vortex (95 RON). Their discount scheme with Caltex was only applicable to UL (91 RON). The car is a common garden variety Holden / Buick 3800. 91 Model, on 8.5:1 CR. So it shouldn't need the extra octane. At the end of the day I won the argument. It was costing me less to run the vehicle on the more expensive fuel, as it went further on a dollar. That's the bottom line.
>>The fact it was costing the company more was their problem, and they should talk to their supplier.
>>
>>The Vortex also has a cleaning agent, which may have more to do with the better economy. As far as I know the ECM doesn't use the "bouncing" effect. But I'm still leaning about that.
>>
>>Can't provide current data. I would have to go back to std fuel.
>>
>>Geoff
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