Does Compression Ratio Affect Engine Note - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

DarkPira7e · 10-07-2020, 04:16 PM

I've watched a few cars (Subarus exclusively) change from higher compression ratio to a lower one, but all were accompanied by so many different mods it was tough to tell -

Can anyone say for sure that changing the compression ratio will change how the engine sounds? Just curious as this doesn't seem to be discussed often and I thought it was a neat topic.

I would imagine that lowering it would also make the engine tone a little deeper and less zingy.

Joveen · 10-07-2020, 05:55 PM

Good topic discussion! Sub'd for info.

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Turdinator · 10-07-2020, 07:09 PM

I can't say for sure as I have not seen the same engine go from high to low or vice versa but my feeling from different engines is higher comp motors are louder

DarkPira7e · 10-07-2020, 07:28 PM

Quote:

Originally Posted by Turdinator

I can't say for sure as I have not seen the same engine go from high to low or vice versa but my feeling from different engines is higher comp motors are louder

It only makes sense, right? My car is having a 10:1 engine put in, but I'm changing literally everything, I had stock exhaust before. I'm hoping that it's a more subdued tone

Spuds · 10-07-2020, 09:26 PM

I think it does make a difference, but how you increase compression is likely important. Increasing stroke would change the sound in a different way than decreasing combustion chambers size.

As for what it actually does to the tone, I need to think more on that...

bfrank1972 · 10-08-2020, 01:53 PM

Quote:

Originally Posted by Spuds

I think it does make a difference, but how you increase compression is likely important. Increasing stroke would change the sound in a different way than decreasing combustion chambers size.

As for what it actually does to the tone, I need to think more on that...

I imagine it affects how you manage dynamic compression with things like valve timing/overlap, that would likely make a significant difference in how things sound.

ls1ac · 10-08-2020, 03:44 PM

In general, changing the compression ratio is done along with other changes. When lowered it is usually with some sort of forced induction. when raised it usually is for higher octane. Both almost always include a change in the cam. The cam, other than exhaust modification, has the greatest ability to change the engine sound.

pallen · 10-08-2020, 05:07 PM

Yeah, I don't know. Higher compression sounds like a "louder" thing, but lower compression is usually done to make for a bigger explosion safely, which should also be louder.
Maybe there's a slight difference in sound, but my guess is the sound is more impacted by the shape and size of the exhaust tubing the explosions dump into - like how the same buzzing lips can sound like a trumpet or a tuba depending on which tube is put to those buzzing lips.

DarkPira7e · 10-08-2020, 07:14 PM

Quote:

Originally Posted by pallen

Yeah, I don't know. Higher compression sounds like a "louder" thing, but lower compression is usually done to make for a bigger explosion safely, which should also be louder.
Maybe there's a slight difference in sound, but my guess is the sound is more impacted by the shape and size of the exhaust tubing the explosions dump into - like how the same buzzing lips can sound like a trumpet or a tuba depending on which tube is put to those buzzing lips.

Not really talking about volume, but pitch. I would like to think that lower compression is duller sounding.

NoHaveMSG · 10-08-2020, 07:21 PM

As far as I can remember the tone is a bit sharper. It has been a while since I have bumped compression on an engine and stood there to hear the difference so take that with a grain of salt.

Tokay444 · 10-08-2020, 08:13 PM

Yes.

Irace86.2.0 · 10-09-2020, 02:22 AM

bfrank1972 · 10-09-2020, 06:08 AM

Quote:

Originally Posted by Irace86.2.0

Interesting, although off the bat the higher compression segment sounds like it is idling higher. Would have been nice to have some revs or rolling shots. That is also a huge bump in static compression

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x808drifter · 10-09-2020, 08:41 AM

Friend went from stock pistons to high comp ones in his D16 build recently.
That was the only change at this point.

I noticed only a slight tone change at idle.
Slightly more high pitched. VERY slightly.

10-07-2020, 04:16 PM	#1
DarkPira7e Rust bucket enthusiast Join Date: Feb 2017 Drives: 2013 Turbo Firestorm FRS Location: Vermont Posts: 3,950 Thanks: 3,210 Thanked 4,104 Times in 2,051 Posts Mentioned: 31 Post(s) Tagged: 0 Thread(s)	Does Compression Ratio Affect Engine Note I've watched a few cars (Subarus exclusively) change from higher compression ratio to a lower one, but all were accompanied by so many different mods it was tough to tell - Can anyone say for sure that changing the compression ratio will change how the engine sounds? Just curious as this doesn't seem to be discussed often and I thought it was a neat topic. I would imagine that lowering it would also make the engine tone a little deeper and less zingy.

10-09-2020, 02:22 AM	#12
Irace86.2.0 Senior Member Join Date: Mar 2017 Drives: Q5 + BRZ + M796 Location: Santa Rosa, CA Posts: 7,884 Thanks: 5,668 Thanked 5,806 Times in 3,300 Posts Mentioned: 70 Post(s) Tagged: 0 Thread(s)	__________________ My Build \| K24 Turbo Swap \| K24T BRZ SOLD

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10-07-2020, 05:55 PM	#2
Joveen Senior Member Join Date: Mar 2018 Drives: Bone stock Location: Windsor, CT Posts: 767 Thanks: 535 Thanked 232 Times in 162 Posts Mentioned: 8 Post(s) Tagged: 0 Thread(s)	Good topic discussion! Sub'd for info. Sent from my SM-N960U using Tapatalk

10-07-2020, 09:26 PM	#5
Spuds The Dictater Join Date: Apr 2017 Drives: '13 Red Scion FRS Location: MD, USA Posts: 9,469 Thanks: 26,233 Thanked 12,486 Times in 6,179 Posts Mentioned: 86 Post(s) Tagged: 0 Thread(s)	I think it does make a difference, but how you increase compression is likely important. Increasing stroke would change the sound in a different way than decreasing combustion chambers size. As for what it actually does to the tone, I need to think more on that...

10-08-2020, 05:07 PM	#8
pallen Senior Member Join Date: Jun 2020 Drives: 2017 Toyota 86 Location: Fort Worth, TX Posts: 261 Thanks: 200 Thanked 184 Times in 110 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Yeah, I don't know. Higher compression sounds like a "louder" thing, but lower compression is usually done to make for a bigger explosion safely, which should also be louder. Maybe there's a slight difference in sound, but my guess is the sound is more impacted by the shape and size of the exhaust tubing the explosions dump into - like how the same buzzing lips can sound like a trumpet or a tuba depending on which tube is put to those buzzing lips.

10-08-2020, 08:13 PM	#11
Tokay444 Anti stance. Join Date: Feb 2016 Drives: 17 White 860. RCE Tarmac 2. RE-71RS Location: Not Canada Posts: 1,640 Thanks: 903 Thanked 962 Times in 550 Posts Mentioned: 10 Post(s) Tagged: 0 Thread(s)	Yes.

10-09-2020, 08:41 AM	#14
x808drifter LMGTFY Join Date: Mar 2016 Drives: 13 FRS, 91 Miata Location: Lava Town, HI Posts: 2,776 Thanks: 5,561 Thanked 3,646 Times in 1,625 Posts Mentioned: 15 Post(s) Tagged: 0 Thread(s)	Friend went from stock pistons to high comp ones in his D16 build recently. That was the only change at this point. I noticed only a slight tone change at idle. Slightly more high pitched. VERY slightly.

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