small exhaust diameter up front and big out back?? - Page 4 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #46 (permalink)  
Old 12-10-2003, 03:21 PM
bullheimer's Avatar
NEVER use credit cards!
 

Last journal entry: car with tt2's, (stockers going back on)
Last photo:
Join Date: Jan 2002
Location: North of Seattle
Posts: 2,529
Wiki Edits: 0

Thanks: 0
Thanked 5 Times in 4 Posts
this is page 4 of this thread.

well, consider it tried, if you read my first post my truck goes from 2" manifold to 2 1/4 to 2 1/2. my truck runs like a raped ape from about @2000rpm to max @5500. which isnt to say i couldn't run better if it was backwards.

i did look under my 72 camaro and it has small exhaust with i swear 1 1/2 " pipes exiting the mufflers. but i still cant imagine starting with 2 1/2 and going to 2 1/4, but apparently, at least for a low end motor it's gotta be best simply cause the factory does everything it can for that like was said. my friend who's a gm wrench says, however, with a stock cam, it just doesnt matter what the hell you do to it, it will barely make any difference. my other friend just put thorley headers and a performer on his pontiac and says he's surprised at how little difference it made.

as was also stated previous, when you make your motor suck more air then you will start to open up the exhaust. but if you have a very restrictive stock exhaust, yes, restriction is bad. but i still swear to buddah i read somewhere about back pressure being good for something with a torque motor, i just can't remember the where or the what, and i'm not about to go look thru the last one or two years of phr or hrm to look like i know what i'm talking about. i did find the oct. prh art. with the sultan of stainless (exhaust), he didnt mention anything about back pressure but he did mention: reverse megaphones are being expermented with to improve power; collector diameter is the most important part besides primary size and "one of the largest errors street enthusiasts make is in runing too large of a primary pipe and too large of a collector:. he also runs on about how great Tri-y's are, but says they have to be tuned right (by him of course) i think you could find it at www.popularhotrodding.com, and it;s Oct. 2003, "The Sultan of Stainless" he also did NOT mention anything about finding the x-over point with spray paint, i musta read that somewhere else.

so basically, you guys are saying that buying 2"rams horns are a waste of time when i can get the 2 1/2" ones? i likewise wish i had better performance below 2000rpm, so seems i should have run 2" after my muff. too bad dyno's dont measure anything below 2K

    Advertisement

Last edited by bullheimer; 12-12-2003 at 12:54 PM.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #47 (permalink)  
Old 12-10-2003, 10:53 PM
Member
 
Join Date: Nov 2003
Posts: 135
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
yeah it just seems like if the theory of hot exhaust gasses wanting to move to a place of lower pressure and temperature is true then bigger tailpipes than up-front pipes could actually improve performance, with my way of thinking anyways. the bigger tailpipes would have lower pressure and a lower temp than those of smaller size and therefore the exhaust would want to rush to that area that little bit faster, almost "sucking" it out of the motor. now i dont know if this would make a little more power on the top end of the rpm range or more torque down low or just overall (im kinda thinking top end power would benefit for some reason), but doesnt it make sense to you guys??
Reply With Quote Quick reply to this message
  #48 (permalink)  
Old 12-11-2003, 01:21 AM
79transam's Avatar
Life's 2 short 2 keep it stock
 
Join Date: Nov 2003
Location: Ohio
Age: 28
Posts: 90
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
From my experience the less backpressure the better. Which is why a wide open exhaust gives you the greatest performance. As for losing low end torque, my dyno program sais that large tube headers produce more power and torque. But, lose A LITTLE in the lower rpm's. I'm talking 5lbs or or less at 2000 rpm but then regains it at 2500 and builds more as rpm's increase. But as with any component changed on an engine, expecially airflow, some tuning is required to makeup for the change. Either way, a more efficient engine is a better running engine.
Reply With Quote Quick reply to this message
  #49 (permalink)  
Old 12-11-2003, 05:44 AM
TurboS10's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Auto Terms and Definitions Used in Modern Engine T... Last photo:
Join Date: Sep 2002
Location: Texas
Age: 36
Posts: 3,463
Wiki Edits: 2

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally posted by smlblcks10
yeah it just seems like if the theory of hot exhaust gasses wanting to move to a place of lower pressure and temperature is true then bigger tailpipes than up-front pipes could actually improve performance, with my way of thinking anyways. the bigger tailpipes would have lower pressure and a lower temp than those of smaller size and therefore the exhaust would want to rush to that area that little bit faster, almost "sucking" it out of the motor. now i dont know if this would make a little more power on the top end of the rpm range or more torque down low or just overall (im kinda thinking top end power would benefit for some reason), but doesnt it make sense to you guys??
What you need to understand is that EGT is significantly lower as it leaves the muffler than when it left the cylinder head. This fact alone will cause the same effect since as temperature decreases, so does volume. That is why you can get away with smaller pipes, although I have always used the same size and usually just dump it after the muffler.

Chris
Reply With Quote Quick reply to this message
  #50 (permalink)  
Old 12-11-2003, 08:32 AM
willys36@aol.com's Avatar
Hotrodders.com Moderator
 
Last wiki edit: How to rebuild a Rochester Quadrajet 4MV carbureto...
Last journal entry: How to change auto shift timing on 200R4
Last photo:
Join Date: May 2002
Location: Bakersfield
Posts: 8,384
Wiki Edits: 21

Thanks: 1
Thanked 4 Times in 4 Posts
This guy gives a HUGE amount of info on his website. also seems to know his stuff. At least what he says is in line with what they teach in physics and fluid flow classes in engineering school;

Headers by Ed

Here is an informative article that cuts through the fog and gives some facts;


Reveng of the Nurds on header design

Here is a related site that talks about intake manifold design. Try their calculator and see that optimal intake runners are much different from those supplied in 'high performance' street/ strip manifolds;

Intake runners and torque

They have a bunch of other useful calculators on their site too.

More informative ramblings that seems to be technically correct;

Ramblings

These guys provide a scientific calculator for all of the important dimensions in 4 to 1 headers that appears to be right on;

Header calculator
Reply With Quote Quick reply to this message
  #51 (permalink)  
Old 12-12-2003, 01:00 PM
bullheimer's Avatar
NEVER use credit cards!
 

Last journal entry: car with tt2's, (stockers going back on)
Last photo:
Join Date: Jan 2002
Location: North of Seattle
Posts: 2,529
Wiki Edits: 0

Thanks: 0
Thanked 5 Times in 4 Posts
that bottom link, you shouldda mentioned, 38, is on designing the tailpipe! onna sbc no less. cool find! hey, you just had to mention physics classes, huh guys! when the night of the living dead comes they will be lookiung for you guys first! BRAINS! I NEED BRAINS!!
Reply With Quote Quick reply to this message
  #52 (permalink)  
Old 12-12-2003, 01:16 PM
New Member
 
Join Date: Dec 2003
Location: Michigan
Age: 51
Posts: 21
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally posted by adryan16
...couldn't you just use one of those laser-pointer style digital temp gauges to check tube temps to determine what the best place was for the crossover tube to most benefit from the scavenging effects that the crossover proposes? (also assuming that there was little to no temp difference between the tube and the exhaust temp)

The temp of the tube is significantly different than that of the exhaust gas in most cases. And you have the issue of measuring the temps on a stationary vehicle vs one that's moving - they'll be different.

Not to mention it isn't much fun standing under a vehicle that's running on a chassis dyno. Been there, done that, no thanks!

In thinknig about it I really dont get this method of finding the crossover location with temps. If you want to exploit the flow dynamics than you're going to be basing some dimensions on the speed of sound in the exhaust. That depends on temp, sure, but that doesn't mean as soon as you found a certain temp you're in the right spot...
Reply With Quote Quick reply to this message
  #53 (permalink)  
Old 12-12-2003, 02:17 PM
New Member
 
Join Date: Dec 2003
Location: Michigan
Age: 51
Posts: 21
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Re: Re: HEADER DESIGN VS. EXHAUST PIPE SIZE

Quote:
Originally posted by 4 Jaw Chuck
Best practice for low overlap engines to broaden the torque curve under the HP limit is to run larger exhaust tubing close to the engine and go down a size after the muffler to maintain gas speed after the cooling effect of the muffler.

As a matter of fact that is exactly how stock exhaust systems are made. Amazing huh?!
In twelve years of designing exhaust systems for OEMs, I've never once had to worry about any of that.

The OEs usually run pipes as small as possible, for numerous reasons. Space, cost, weight, etc. No one gives whit about gas speed after the muffler, in fact I'd venture a guess that 90% of the OE engineers involved in exhaust system "design" wouldn't even know what you're talking about. They are, by and large, release engineers who care about cost, timing, durability, and meeting sound quality and restriction targets. (I'm not trying to be cynical here, it's true.)

I can point out examples of tailpipes being bigger, smaller, or the same size as the muffler inlet, and even single 2.50" inlet, dual 2.50" outlet mufflers.

The calibration engineers request a certain restriction. As long as we (the supplier who does the actual development) stay below that level, no further work is needed. I've seen tail pipe diameters change for NVH reasons, sound quality reasons, cost reasons, or packaging, but I have never heard of an OEM requesting a certain tailpipe to improve the torque curve.

The majority of the work in exhaust development is for emissions, durability, and sound quality. It's extremely rare that I'd ever even see a torque curve.
Reply With Quote Quick reply to this message
  #54 (permalink)  
Old 12-12-2003, 03:55 PM
4 Jaw Chuck's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Mar 2002
Location: Manitoba, Canada
Age: 46
Posts: 4,900
Wiki Edits: 0

Thanks: 0
Thanked 72 Times in 60 Posts
Can't speak for the big three but this is exactly what the Japanese are doing, maybe thats one reason why they produce engines of higher specific output per litre of displacement.

No doubt the effect is minor, but if your sweating the details and getting paid for it wouldn't you at least consider the effects and design it in?

What type of engineering work do you do for the auto manufacturers Desmo?
__________________
Outlawed tunes from outlawed pipes
Reply With Quote Quick reply to this message
  #55 (permalink)  
Old 12-12-2003, 05:40 PM
NAIRB's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Sep 2002
Location: cimarron, ks
Posts: 1,658
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
A friend of mine used to work at Arvins in Columbus, IN. His job was to fit up prototype exhaust systems for new cars. I worked myself for Arvins for a few months on the line and I will say that I think their concern was if it fit or if it didn't fit. Now, that's been a few years ago, but I would have to say that the big three wants them to fit and probably don't really care if they lose a few horsepower over the deal, however I'm sure that if we are talking about a real performance car, like a Corvette, a little more thought may go into it.
I think 4-jaw is right about what's on the cutting edge of the drawing boards with the auto manufacturers.
Reply With Quote Quick reply to this message
  #56 (permalink)  
Old 12-12-2003, 08:02 PM
badknuckles's Avatar
you talkin to me?
 
Join Date: Nov 2003
Location: fort lewis, wa
Age: 33
Posts: 1,090
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
the less power you have the smaller the tubes you want hot exhaust gasses flow faster than cold exhaust so the bigger the pipes the colder the exhaust the slower the flow the less power you have big pipes for big power small pipes for small power
Reply With Quote Quick reply to this message
  #57 (permalink)  
Old 12-12-2003, 08:10 PM
troy-curt's Avatar
Shop Owner And Troll Hunter
 

Last journal entry: Detailing Eng. Compartment
Last photo:
Join Date: Apr 2003
Location: Prairie Grove Ar.
Age: 75
Posts: 2,646
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Hummmmmm, I wonder how many people understand what has been said in this thread. And how many can apply it.

Just a thought
Troy
Reply With Quote Quick reply to this message
  #58 (permalink)  
Old 12-12-2003, 08:23 PM
badknuckles's Avatar
you talkin to me?
 
Join Date: Nov 2003
Location: fort lewis, wa
Age: 33
Posts: 1,090
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
i think this thread has seen its day i think its past.
next?
Reply With Quote Quick reply to this message
  #59 (permalink)  
Old 12-12-2003, 10:34 PM
New Member
 
Join Date: Dec 2003
Location: Michigan
Age: 51
Posts: 21
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally posted by 4 Jaw Chuck
Can't speak for the big three but this is exactly what the Japanese are doing, maybe thats one reason why they produce engines of higher specific output per litre of displacement.

No doubt the effect is minor, but if your sweating the details and getting paid for it wouldn't you at least consider the effects and design it in?

What type of engineering work do you do for the auto manufacturers Desmo?
What's your source on the Japanese doing this? Maybe on the S2000 and stuff like that, but it's certainly not across the board. And we DON'T get paid to sweat that detail... that's my point. (It would be nice to think that in every company there is some group doing R&D work on stuff like this, but guess what area gets hit first when the budget cuts begin?) I've probably requested a couple thousand dyno runs to be done over the past decade or so. Aside from one 8-month project I worked on, those dyno runs were never meant to measure power output, they were all about acoustics.

(That said, engineers on other platforms DO run more powerloss tests, but the targets on those are virtually always tied in to restriction levels.)

My business card says "Engineering Supervisor - Ford and Japanese O.E. System Development" which is a bit long winded and somewhat misleading as much of the Japanese development is done in Japan... Basically I used to design systems for various manufacturers, now I supervise people who design systems but still do some development on certain projects.

I've done the exhaust on the T-bird, the infamous Blackwood, Lincoln LS, a couple versions of the Harley truck, and a few others. I was asked to do the Ford GT but the boneheads at our company turned the project down! Grrrr! In a previous life I did mostly Jeep stuff, but don't blame me if you own a Grand Cherokee that sounds like crap. That happened after I left. (and my wife owns one too, I feel your pain)


NAIRB - who did you know at Arvin? I worked there for about six years in the early '90s, so if he was there then, I know him too. Did you work over at Happy Rock, or Franklin?

Regarding design parameters, the Corvette wasn't any different - the targets were/are all based on restriction. The GTO isn't any different, the Viper isn't any different, the Viper truck isn't any different, the Lighting isn't any different, etc... Other than the absolute top gun performers, there isn't a bunch of work put into exhaust development from the power side of things. The main part of an exhaust development engineer's job is developing the sound of the vehicle.

Last edited by DesmoDog; 12-12-2003 at 10:40 PM.
Reply With Quote Quick reply to this message
  #60 (permalink)  
Old 12-13-2003, 07:18 AM
4 Jaw Chuck's Avatar
Hotrodders.com Moderator
 
Last photo:
Join Date: Mar 2002
Location: Manitoba, Canada
Age: 46
Posts: 4,900
Wiki Edits: 0

Thanks: 0
Thanked 72 Times in 60 Posts
Thanks for the insight Desmo, sounds like a truly sorry state the industry is in when only the engine designers are allowed to run dyno tests. I guess it keeps the aftermarket companies in business?
__________________
Outlawed tunes from outlawed pipes
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 03:19 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.