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Discussion Starter #1
Zetec is 9.6:1


How much can you raise the compression ratio and still be able to use regular gas without the knock sensor kicking in and retarding timing?

then 89?

then 91? (don't have 93 in CA)
 

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You need to get a tune either way, im guessing 10.5 on lower octane and 12 to 1 CR on premium. every car will run a little differently depending on engine wear, factory timing, spark plugs,ect.

but you have an automatic station wagon.....so.. you probably shouldn't waste your money if you want to go faster. If you want to go fast for cheap, find a used turbo car for 5 grand. 240sx 300HP rear wheel drive monstor,
 

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Discussion Starter #3
When you rebuild an engine, you deck the block and head which will increase the compression ratio.


I looking at how much you can safely take off without a retune.

Then if you'll possibly need more octane depending on how much is taken off.
 

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Pretty much your going to have to tune it regardless...

There are lot's of threads on this general topic. Most go something like this:

shave 0.040 off of the head to 10.5:1 and a tune to 93 octane.
 

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The very presence of the knock sensor says it is already used, you will just make it used more with no tune to get around that. You'll hit it more and it will just detune more.
 

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Discussion Starter #7
What other mods are you going to be adding with the higher compression ?

Tom
VERY minor porting. At the level of removing flaws and imperfections.

Backcut the valves if necessary.

Minor details that are easy to do when things are apart.
 

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Discussion Starter #8
Pretty much your going to have to tune it regardless...

There are lot's of threads on this general topic. Most go something like this:

shave 0.040 off of the head to 10.5:1 and a tune to 93 octane.



Only have 91 in CA


What kind of squish/quench does a Zetec have anyway?
 

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Discussion Starter #11
As noted in a reply, this car has an automatic.


So HP increases at high rpm are pretty much worthless.


Bumping up the TQ curve (efficiency) and mileage (cost per mile) is the goal.

Higher octane fuel is ok if the mileage increases enough to offset the cost........
 
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