[DML] Re: Failed emmissions AGAIN
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[DML] Re: Failed emmissions AGAIN

--- In dmcnews@xxxxxxxxxxxxxxx, "Tom Niemczewski" <tomciodmc@xxxx> wrote:
> ...the answer to that would be that whoever 
> wrote the Owner's Handbook must have made a mistake or just forgot to 
> mention that in YOUR book. I say "your" book because mine clearly
> that in the USA 87 should be used and that 91 was for Europe. Maybe
I have a 
> later version of the book that was updated.
> Anyway, in the Owner's Book that I have there is a mention of that
on page 
> 40. Right on top, on the right side of the page. Here's an EXACT
copy of 
> that:
> Fuel Requirements
> Your De Lorean is designed to operate at factory specifications at
> GASOLINE only of at least 87 anti-knock index (R+M/2) (91 research
> number)

I have a 1983 Owner's Handbook. Probably the last edition printed. You
are correct. It does state that on page 40. I however was referring to
page 39 where is says:

"Fuel Tank          51.6 litres          13.2 gallons
(91 octane unleaded only)"

When I see "91 octane unleaded only" in the handbook of an American
car, I naturally assume they mean U.S. 91. That is a fair and
reasonable assumption. Also consider that your average U.S. car buyer,
like myself, does not know the difference between (R+M/2) & RON, so
what is says on page 40 is over most people's heads. So take what it
says on page 39, not understand what it says on page 40, throw in the
"premium 91 is better than regular 87" marketing influenced
misconception along with the common uninformed thinking that "I'm
driving an expensive sports car, and expensive sports and luxury cars
need to run on 'better' fuel" and you can see why your average
DeLorean consumer would choose U.S. 91 octane to fuel their D.

I now understand the difference between (R+M/2) & RON because I looked
it up on Wikipedia. I also now see that the Owner's Handbook was
poorly written.

> Is this a bulletproof enough source? :)

Yes, but looking back on what I wrote I was apparently not clear
because I was referencing the desire for bulletproof sources on your
claim of deposits building up due to using higher octane fuel than
required that leads to emission issues when I said: "I don't believe
using slightly higher octane than needed based on the engine's
compression ratio will hurt anything..."

> The higher the octane number the less chance for detonation but
> at the same time combustion temperatures are higher.

Okay, so wouldn't higher combustion temps burn off these deposits?
Again, I'm not arguing as much as approaching this from the point of
view of someone with limited knowledge attempting to apply common
sense based on what they know. Also, my previous question still
remains. If you have an engine that has been run for a long time on
higher octane fuels than required, and it now has these deposits built
up that have raised it's compression as a result. Wouldn't suddenly
running it on lower octane cause, or run a higher risk of detonation
since you're now running fuel lower in octane than appropriate for the
engine's "new" raised compression ratio? I mean, if the deposits
raised the engine's compression, wouldn't running a fuel that is not
adequate for the current compression cause knock rather than clean out
the deposits?

> Use 87! Your car will be much better with it in the long run.

Ambient air temp is another factor in detonation. I know this through
experience, not through a text book. Again, I live in Phoenix,
Arizona. One mile above hell, lol. I have a '97 T-bird with a 3.8
liter V6. It's a low compression engine too, and Ford suggests running
it on 87 (R+M/2) in the handbook, but if I do on days between 80 & 115
degrees fahrenheit, or when climbing steep grades at any air temp, the
engine detonates like crazy. I've had four Ford V6s that all did this,
but when you ran them on 89 or 91 (R+M/2), there was no audible knock.
Will the PRV V6 do the same? I don't know, but I also do not want to
find out.

> And the most important thing - 93 IS NOT BETTER than 87.

It is if it prevents detonation in your particular engine regardless
of what a handbook says. I'll take emission fouling deposits over
detonation any day!

By the way, just an FYI. Premium fuel in Colorado is 91 (R+M/2), not
93 (R+M/2).

Dan W.
VIN 16192

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