Header Question

Moderator: DLRA

Cpt.Stew
Posts: 1
Joined: Sun Mar 27, 2011 6:26 pm

Re: Header Question

Post by Cpt.Stew » Mon Jun 18, 2012 8:26 pm

Within reading the previous comments and not knowing any of the engine specs re: the "BBC",,why doesnt the owner just build a basic set of 2 / quart" tri- y headers.!!, using nice merge collecter 2 / 1 sections, exit the system with a neat 15" long oval style 4" collector pipe...straight out under the vehicle floor pan...Forget fender exit pipes for now..

User avatar
PLUCKA
Posts: 157
Joined: Fri Jan 25, 2008 9:50 pm
Location: Wudinna really close to Lake G

Re: Header Question

Post by PLUCKA » Mon Jun 18, 2012 9:10 pm

Agreed Cookie and thats what I went to I mine or a similar home made creation. lol
Having them exit underneath the floor stopping at the collector may assist in lifting or unsettleing the vehicle in my opinion, albeit unprofessional

Plucka

momec3
Posts: 720
Joined: Tue Mar 01, 2011 10:36 pm
Location: Cedar Grove Qld

Re: Header Question

Post by momec3 » Thu Jun 21, 2012 7:23 pm

Plucka,
I'd love to see simple chassis dyno graph difference between full exhaust on yours and straight off headers. If your exhaust is big and unrestricted the difference should be minimal. All engine dynos use some form of exhaust. Our style would have a minimum 4" tube.

Other way is do a with or without test on the Big White Dyno with no other changes. This would be much more definitive. You can't drive a dyno :wink:

Chris
Chris

User avatar
BONES
Posts: 354
Joined: Wed Mar 15, 2006 4:28 pm
Location: Killara Sydney

Re: Header Question

Post by BONES » Thu Jun 21, 2012 7:47 pm

Chris
How much did the HP increase fron a good set of headers ( as designed) to when you had finished messing about with them?
and how long did it take?

cheers Bones

User avatar
Dr Goggles
Posts: 1303
Joined: Tue Jul 05, 2005 11:23 pm
Location: Right behind you Chief !

Re: Header Question

Post by Dr Goggles » Thu Jun 21, 2012 8:12 pm

Yeah I know I sh1t you door car guys off but the exhaust thing out the back of the car?????? Next you'll be tellin me that there are things that you can use instead of carburettors???

You guys can't use ducting......( relieving high pressure areas and ducting it to low) so I've been wondering for a long time when creative exhaust was going to take off. There are more and more cars popping up in the States with it.

It sounds weird but sending the exhaust out the side of the car does two things

1./ The emerging gases produce a "shadow", you might as well have your arm stuck out the side of the car, it is that big.

2./ The more obvious problem is it upsets the "boundary layer".

Sending the exhaust out the rear of the car has some big positives.

1./ The exhaust gases are cooling rapidly, that means they are shrinking, that is an excellent way to "de-energize" the wake , it works kind of like a dampener. Remember: it is the mess you leave that slows you down more than the air you are trying to push through.

2./ You get thrust. Maybe not even enough to part your hair but some.

twenty pages here : and excuse me being in it but there are some really interesting ideas from Superford 317. Some heavy duty theoretical ideas that will never be seen on cars but plenty of thrashing out of the ideas, importance and potential of creative exhaust......plenty of the contributors have records and one has a 300+lakester record.

http://www.landracing.com/forum/index.p ... 912.0.html

Image
...few understand what I'm trying to do , but they vastly outnumber those who understand why..

momec3
Posts: 720
Joined: Tue Mar 01, 2011 10:36 pm
Location: Cedar Grove Qld

Re: Header Question

Post by momec3 » Thu Jun 21, 2012 8:53 pm

Bones,
Your question does not have a real answer that means Jack Shit.

A "right" exhaust will always make more power than a "wrong" exhaust. How you get to the perfect "right " exhaust starts with applying age old theory on cam design hand in hand with header design. Add compression, fuel, revs, desired result (do you value torque more than a peak HP number)
My view on what we do has changed over the last few years.
I used to think high torque was preferred over peak horsepower numbers. The lack of racing has given me way to much thinking time hence my view has changed and been influenced by others.
I now tend to follow the view that we need to sacrifice mid range torque and even discourage this trait totally for the benifit of a peak HP number at peak revs.
This style of motor requires more time to build speed and is less likely to suffer huge wheel spin building up to this.
A lot of experienced US racers will say derr, we have know this for years. We are still learning this game.
Being Aussies/Kiwis even with the information revolution we still work in a bit of a vacuum.
This helps and hinders.
Need more track time and a bigger budget.
Goggles, you are right but I will never admit it. :P

Chris
Chris

hawkwind
Posts: 284
Joined: Fri Dec 17, 2010 3:50 pm

Re: Header Question

Post by hawkwind » Thu Jun 21, 2012 9:34 pm

Doc ...I think your exhaust exit theory holds true for streamlined vehicles and maybe to some extent for sedan type cars and possibly partially streamlined bikes .... but in my class ...naked bike ( and you car guys think roadsters are bricks) where the exhaust exits makes very little difference as the boundry layer has long since seperated before it even reaches the headers ......Chris top speed needs peak HP at peak RPM and gear ratios close enough to allow changes not to fall out of the power band along the way , its all about a 5 mile drag race.....back to the rear exiting exhaust ... is there really enough exhaust mass or volume to make any difference at all .... considering the overall amount of air being displaced ??? I personally believe it will only have an effect on streamliners and then only a small net gain ... but I could be wrong.
gary
Vehicle......................A new creation.
Designed by................Troglodyte.
Engineered/ built by......Rustic.
Financed by.................Nickles & Dimes.
Rider......................... Tardus Vetus Inflatio

User avatar
Dr Goggles
Posts: 1303
Joined: Tue Jul 05, 2005 11:23 pm
Location: Right behind you Chief !

Re: Header Question

Post by Dr Goggles » Thu Jun 21, 2012 10:14 pm

There are still plenty of people who will dispute the top power/top revs thing....but it's really a bit of a no-brainer, especially for door cars . We are trying to go fast, the faster you go the more drag a shape will produce . A given shape will "hit the wall" at a calculable point , if you have an arched power curve then that will happen sooner than if it is a steady gradient, increasing rev by rev......

Unless of course you run out of traction,

Minimising drag will help then..........and I won't disagree with you here Chris, spoilers aren't necessarily the way to go. A proper "wing" yes, with a proper foil shape that can add the downforce you need at the speed you need it at...will cost you drag but is the best of a bunch of bad ideas. Ballast is where it's at.... but then Force/mass =acceleration.....so you'll accelerate slower...hmm, this is more complicated than I thought. :roll: :roll: :roll:

hey Gary how much to you have to beat a record by to set a new one...... 0.1%....less???, but you're right about naked bikes...

I'm gone.
...few understand what I'm trying to do , but they vastly outnumber those who understand why..

ben james
Posts: 279
Joined: Mon Dec 12, 2005 6:45 pm
Location: melbourne

Re: Header Question

Post by ben james » Thu Jun 21, 2012 11:55 pm

1./ The exhaust gases are cooling rapidly, that means they are shrinking, that is an excellent way to "de-energize" the wake , it works kind of like a dampener. DAMPER :roll:

.....back to the rear exiting exhaust ... is there really enough exhaust mass or volume to make any difference at all .... considering the overall amount of air being displaced ??? I personally believe it will only have an effect on streamliners and then only a small net gain ... but I could be wrong.
I think some 4 cylinder top fuel motorcycle teams have some data about exhaust effect.
Ben
ben james dlra#389
moriwaki monster.

User avatar
Greg Watters
Posts: 758
Joined: Mon Sep 27, 2004 8:57 pm

Re: Header Question

Post by Greg Watters » Fri Jun 22, 2012 1:23 am

rear exhaust is a simple numbers game
very roughly say 100mph , 1.66mile/ min or 8764 ft.min x the air your displacing ,is 15sq ft reasonable for a car =131472 cubic foot of air
now the exhaust, 300hp for the 100mph ??? roughly 300cfm for 300hp air in , then what sort of volume out the exhaust, x6??x10 ?? , which ever way you look at it there is a huge shortfall
advantages may be more when you get to 300mph as the hp required has risen a lot more than the air displaced has

hawkwind
Posts: 284
Joined: Fri Dec 17, 2010 3:50 pm

Re: Header Question

Post by hawkwind » Fri Jun 22, 2012 7:24 am

Ben :) good to see you posting.......I believe the top fuellers run the headers skyward for some extra down force....not to try and fill in the partial vacuum behind them.....because they run large percentages of nitro they are using the thrust produced by the expelled MASS X VELOCITY ( like how a rocket works) .....would be interesting to see what thrust is produced by the bikes and how much downforce it produces against the drag penalty for doing that ....seeing as bikes are poorly served in the traction stakes.
Yes Googles 0.1mph :)
Gary #282
Vehicle......................A new creation.
Designed by................Troglodyte.
Engineered/ built by......Rustic.
Financed by.................Nickles & Dimes.
Rider......................... Tardus Vetus Inflatio

User avatar
JonB
Posts: 268
Joined: Wed Oct 06, 2010 6:35 pm
Location: Brisbane

Re: Header Question

Post by JonB » Fri Jun 22, 2012 7:42 am

Chris
As your chasing top end power do you still use Tri Y headers or recommend 4-1?

I'm planning on using Bell's formula's as a bassis for for my headers, are they still considered ok or have things moved on?

Also agree with Goggles on sending the exhaust out the back, going to have trouble trying to get past my engine though.


Thanks
Jon
DLRA#1115
Underhouse Engineering

User avatar
Dr Goggles
Posts: 1303
Joined: Tue Jul 05, 2005 11:23 pm
Location: Right behind you Chief !

Re: Header Question

Post by Dr Goggles » Fri Jun 22, 2012 9:58 am

Greg Watters wrote:rear exhaust is a simple numbers game
very roughly say 100mph , 1.66mile/ min or 8764 ft.min x the air your displacing ,is 15sq ft reasonable for a car =131472 cubic foot of air
now the exhaust, 300hp for the 100mph ??? roughly 300cfm for 300hp air in , then what sort of volume out the exhaust, x6??x10 ?? , which ever way you look at it there is a huge shortfall
advantages may be more when you get to 300mph as the hp required has risen a lot more than the air displaced has

Lets not get confused about what we're talking about. Counter to what someone contended on landracing the other day you will never fill your wake with exhaust. That's ridiculous. Exhaust is mostly Nitrogen,CO2 and water, the water is super-heated steam, when that hits 30degrees C air it rapidly cools and the volume is reduced massively.That's an energy change. When you drive through any fluid substance you dissipate energy and some of this is expressed as eddys. Just like when you stir a big pot it takes energy to create those eddys.Just adding the rapidly cooling gases to the lower pressure behind the car will reduce the effect, that's less total drag.
...few understand what I'm trying to do , but they vastly outnumber those who understand why..

User avatar
Dr Goggles
Posts: 1303
Joined: Tue Jul 05, 2005 11:23 pm
Location: Right behind you Chief !

Re: Header Question

Post by Dr Goggles » Fri Jun 22, 2012 10:57 am

ben james wrote:1./ The exhaust gases are cooling rapidly, that means they are shrinking, that is an excellent way to "de-energize" the wake , it works kind of like a dampener. DAMPER :roll:

.....back to the rear exiting exhaust ... is there really enough exhaust mass or volume to make any difference at all .... considering the overall amount of air being displaced ??? I personally believe it will only have an effect on streamliners and then only a small net gain ... but I could be wrong.
I think some 4 cylinder top fuel motorcycle teams have some data about exhaust effect.
Ben
I think you're trying to have your unleavened bread and eat it too Benny,.......get a Webster's up ya. :wink: :wink:
...few understand what I'm trying to do , but they vastly outnumber those who understand why..

momec3
Posts: 720
Joined: Tue Mar 01, 2011 10:36 pm
Location: Cedar Grove Qld

Re: Header Question

Post by momec3 » Fri Jun 22, 2012 2:57 pm

Jon,

Top end only 4 into 1.
Tri Y has huge benifits in mid range and shifting the torque curb (tuning the curb)
Unless you can build and dyno 30 sets of pipes build 4 to 1's and follow Bell's formulas.
You will get close to right with little pain first time.
Remember that from close to right the gains to be made get smaller and smaller the more you polish it.

Chris

My opinions only, results may vary. :wink:
Chris

Post Reply