compression ratio [Archive] - Team Camaro Tech

: compression ratio


zack 68
Dec 28th, 03, 06:26 AM
graemlins/clonk.gif hey guys i'm still learning so this might sound kinda weird,but does the compression ratio affect how loud the car sounds. for example if you have a 2.5" exhaust with headers and nothing else changes except the engine compression will this affect how loud the car sounds.
thanks,
zack68

jims73z
Dec 28th, 03, 08:11 AM
Yes, especially at idle. Not a huge amount but
my flowmasters went from loud to unbearable so I added mufflers in front of them. I also changed cam.

zack 68
Dec 28th, 03, 09:20 AM
how much increase did you have on your engine? would 9.5comp have a nice rumble?
zack68

pdq67
Dec 28th, 03, 10:32 AM
A high compression ration motor with a strong cam will have a "bark" to it that only compression can make!!

It's not that the low and medium compression motors don't sound strong, it's just that to me they don't have that bark!!

I think it has to do with opening the exhaust valve while there is still a lot of pressure on the cylinder due to the increase in compression since the charge is being squeezed harder then ignited but really don't know for sure??

There have been guy's comment about UDHarold's cam's creating that UD-Cam sound and I think that is what Harold said caused it?????

pdq67

zack 68
Dec 28th, 03, 11:58 AM
what in your opinion is the lowest compression ratio that will give you a slight "bark" on your engine?
zack68

pdq67
Dec 28th, 03, 06:21 PM
Imho, 11 to 1!! And a good 290 advertised duration solid lifter cam will help it out!! pdq67

camaroman7d
Dec 28th, 03, 08:19 PM
Zack,
Before you run out anb buy or build an 11:1 engine, maybe you should ask a few more questions.

11:1 is not going to be pump gas friendly (it can be if you know a few tricks).

WHat are your goals? Is it a street car or a race car? What size engine are you talking about? Engine size has a lot to do with the exhaust note/sound. Is there a certain sound you like or have in mind? A cam will change the tune at idle, certain mufflers are louder than others, etc...

Don't make the mistake of building a certain engine just so it sounds "mean" there are a lot of "mean" sounding engines that can't get out of their own way. You wouldn't want that.

zack 68
Dec 29th, 03, 04:11 AM
Camaroman,
thanks for the advise. i've allready had my engine rebuilt and it is for street use. the reason i'm asking is because i haven't yet started up my engine and i really hope it doesn't sound weak. i have a 383 stroker with a 450 lift, 280/280 adv.duration hydraulic cam. i'm running 1 3/4" super comp headers with flowmaster exhaust and x pipe. the compression ratio is 9.5 to 1.
hope it sounds good,
zack68

pdq67
Dec 29th, 03, 08:26 AM
zack 68,

camaroman7d hit the nail on the head!

You can't feed a high compression motor anymore so please don't go by the high compression sound that is sooo neat!!

My 11.5 to 1CR., .060" over 409 with the NASCAR solid cam sounded fantastic but would be an absolute nightmare nowadays to feed!! I had two 2.5" glasspacks end to end and one smaller glasspack on the tailend like a resonator down each side so you don't think it didn't cackle AND bark!!!

pdq67

camaroman7d
Dec 29th, 03, 08:42 AM
Zack,
Your 383 will have a nice healthy sound. With the headers, nice size cam, and Flowmasters, it will rumble. You will probably be very pleased.

zack 68
Dec 29th, 03, 10:01 AM
graemlins/beers.gif Camaroman,thats good to hear.it makes me a bit more optimistic. the reason i was worried was because i talked to a guy with a 71 olds that had a simular cam to mine and i heard his car and it sounded weak. he wasn't running headers or performance exhaust. i don't know what compression he was running,the cam did have a little lope in it ,but overall it sounded weak. i just want that nice noticable rumble at idle but a good growl when i get on it.
zack68