Downside Of High Compression Ratio

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Chewy 0w0

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Nov 16, 2017

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Nov 30, 2017

#1

• Nov 30, 2017

• #1

Hello everyone.
I came today with something odd. I own a 2003 v6 mustang (manual) and as i work on it something that shows constantly is the idea of tuning the car too a higher compression ratio to use high octane gas. This would give the car a little bit more of punch; however, there is always a down side. I don't know what this may do to the fuel economy of the car. But i just hear that this may damage the piston rings because of the higher pressure. My car has 200k miles on it so it may actually be something big. I just wanted to confirm and hear the experience of folks that may have done the tune on this cars before.
Thank you for reading this post.

 

wmburns

SN Certified Technician

Aug 14, 2009

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Houston Texas

Nov 30, 2017

#2

• Nov 30, 2017

• #2

Do you mind letting us know just HOW you are planning to tune in a higher compression ratio?

Are you sure that advancing the timing is what is really on your mind?

 

Last edited: Dec 3, 2017

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C

Chewy 0w0

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Dec 1, 2017

#3

• Dec 1, 2017

• #3

I have to fix an exhaust leak and i plan to change the cat-back. After that i had plan to take it to a dyno and let the pros tune the car to use 93 octame gas. Just wanted to get the most of the poor 3.8 engine

 

Mattstang04

15 Year Member

Sep 15, 2006

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Dec 2, 2017

#4

• Dec 2, 2017

• #4

You might want to look into what it takes to actually increase compression. A performance tune will adjust timing making 93 octane necessary. Probably squeeze a few more ponies out of it.

That's not the same as changing combustion chamber size or piston shape to increase compression. That's very involved and expensive.

 

Reactions: Hoytster and General karthief

Neuron

5 Year Member

Nov 6, 2016

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Dec 3, 2017

#5

• Dec 3, 2017

• #5

Premium gas runs 18-20 cents more a gallon and for a small increase in HP that you probably won't even feel why do it? It you have emissions testing you may need two tunes. 200K on it I would just keep up the maintenance and save for a V8. A K&N Filter might do as much.

 

rancorkeeper

Founding Member

Mar 19, 2001

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Dec 4, 2017

#6

• Dec 4, 2017

• #6

What the others are trying to say without being quite this explicit: what you described in your post is to change the timing (advance to provide more power with 93 octane gas). This is not the same as changing the combustion ratio.

To do that, you would need to either change the size of your cylinder or the volume of the combustion chamber. This would require physically removing the engine & making internal changes. In doing so, if you created a higher compression ratio, you would need to increase the octane of your fuel to resist detonation, also known as engine knock. Not doing so would very likely damage the engine, as you mention. But changing the timing has no effect on combustion ratio.

 

Reactions: General karthief

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Chewy 0w0

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Nov 16, 2017

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Dec 10, 2017

#7

• Dec 10, 2017

• #7

Thank you for your explanation.
I'm relatively new into the car community so I'm eager to learn.
I have decided not to tune the car for the time been. Like you guys said, while it while increase the power, it will not be an incredible gain. I'm sure i would notice it; however, for daily driving, it will not make a big difference.
I may do the tune one day when a have more monetary power, yet, for the time been, just keeping up with the maintenance will have to do.

Thanks again for sharing your experience with me.
PD: i'm already aiming for my next car and unfortunately, is not a mustang. But i will always carry the mighty essex v6 3.8 in my heart.