Stop Saying Car Exhausts Need Back Pressure

[FastDriver]

Wow, this thread took me on a wild ride through bernoulli, venturi, and magnus effects. This is a pretty cool video:
View: https://www.youtube.com/watch?v=QtP_bh2lMXc


Anyway, as an enthusiastic amateur physicist, I have some issues with the way people interpret the bernoulli effect. I'll keep it concise: the venturi effect works in closed systems. The bernoulli effect works in regards to a specific fluid stream, not comparing one stream to another. The magnus effect is just a super cool non-intuitive application that I just learned the name of. They have "sail" boats that use spinning cylinders instead of sails! Cool!

Oh yeah, and here's an article that is more relevant on this subject: https://nasaspeed.news/tech/engine/...ods-of-getting-burned-gases-out-of-an-engine/

 

[grumpy150]

Anyone that doesn't know Grumpys Toy needs return their man card.
Legend.
So, Grumpy... are you family of the famed and legendary Grumpy?

No like I said we took grumpys money. But i had mad respect for the guy. He did drop the ball on the street race.

 

[killer5.0]

Is this to optimize engine longevity or a means to pull out every available HP out of the system?

Is it to say you couldnt make 800rwhp with a full 2.5" setup?

 

[grumpy150]

Is this to optimize engine longevity or a means to pull out every available

No like I said we took grumpys money. But i had mad respect for the guy. He did drop the ball on the street race.

Lol him and his stogies. He was really a nice guy if you got past the grump. That same 302 Chevy motor ran 10000 rpms for a good twenty years I knew of. And all he ever did was head work. That was his story anyway

 

[grumpy150]

You made my day I had no idea he had videos. I met grumpy in about 87-88 seen his car around Ogden utah. For years after that. What a legend I didn' know he had one the 67 nationals his grumpy toy was a 69 camaro running a 302 Chevy motor he said he got a NASCAR teams specs and copied it then later made changes.

 

[Noobz347]

Sorry, I really misstated that, I must not have eaten my Wheaties that morning. Basically what I was trying to describe what Noobz said, the venturi effect. Smaller diameter piping will increase velocity at lower RPM's which will help improve low end torque. That smaller diameter piping becomes a restriction at higher RPM (higher flow rates) and therefore has a negative effect on power.

And thank's for clarifying that @FastDriver. I really did a bad job at trying to explain it. I think we are all on the same page now.

Correct. It's like what @FastDriver stated about sizing your primaries for a specific rev range. OEM exhaust is matched to the intake and cam in the range that they are expected to "work".

I really dislike a lot of intake and exhaust comparisons you see on TV and in magazines. If you change an intake and move the power band up or down, the exhaust should change with that.

It's something to keep in mind when shopping for and intake and looking at a lot of these "back-to-back" comparisons. Where does each intake make power? What needs to change on the exhaust to get to the rest of it?

Oh yeah, under-drive pulleys.

 

[grumpy150]

You made my day I had no idea he had videos. I met grumpy in about 87-88 seen his car around Ogden utah. For years after that. What a legend I didn' know he had one the 67 nationals his grumpy toy was a 69 camaro running a 302 Chevy motor he said he got a NASCAR teams specs and copied it then later made changes.

Now I'm confused the guy in the link you dent me looks like it could be the guy I knew when he was young. But this guy eas around ogden utah. So all this stuff says he's from Pennsylvania. And died there. Now I guess I could have just seen him when he came to town for a race in salt lake. But I'm wondering was the guy I knew just a fan or his kid? He drove a dark gray 69 camaro. Said grumpy toy on the back. 10000rpm on the windsheild sun viser part. Like I said three exhaust pipes. Smoked a cigar and always had a four speed. Pretty weird. Wish someone could straighten that up for me

 

[General karthief]

About what year was this?

 

[grumpy150]

I said earlier but I've been thinking and it would have been 85-86. And I'm pretty darn sure it' the same guy just a lot older. But wth was he doing crushing the Blvd in Ogden? It was and from what I hear still is cool place to cruise it' like being in the movie American grafitti in the 80's and 90's it was almost all 60's cars. Just don' get why he always there. I guess it could have been a look a like copy cat or his son but it sure looks like him the guy always raced with a cigar and could bang that four speed like no one I ever seen besides the original wheel man my dad. The street race story is really cool.

 

[grumpy150]

I said earlier but I've been thinking and it would have been 85-86. And I'm pretty darn sure it' the same guy just a lot older. But wth was he doing crushing the Blvd in Ogden? It was and from what I hear still is cool place to cruise it' like being in the movie American grafitti in the 80's and 90's it was almost all 60's cars. Just don' get why he always there. I guess it could have been a look a like copy cat or his son but it sure looks like him the guy always raced with a cigar and could bang that four speed like no one I ever seen besides the original wheel man my dad. The street race story is really cool.

The track in salt lake is 5000 feet above sea level this guy ran low tens hard was hell to do with a small block not many and maybe the only guy that beat him on the street was my friend. Grumpy showed without slicks. Bad mistake we drove around on them