Go Back   EcoModder Forum > EcoModding > Off-Topic Tech
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 11-25-2008, 11:05 PM   #1 (permalink)
leftlaneleadfoot
 
Join Date: Aug 2008
Location: Illinois
Posts: 4

Slow Ride - '03 Pontiac Sunfire SE
90 day: 29.91 mpg (US)

Malibu - '14 Chevrolet Malibu 1LT
90 day: 26.61 mpg (US)
Thanks: 0
Thanked 0 Times in 0 Posts
Cold air bends valves?

Hello all

I drive an '03 Pontiac Sunfire. I got this car very cheap as a repo and it is great. My only concern is the ridiculously large tuner car type replacement muffler that came on the car. I've been told that this causes low backpressure and that cold air can work its way all the way up the exhaust to the valvetrain and cause damage such as bending valves, breaking springs, etc. As far as I can tell the rest of the exhaust is stock and the cat converter is present. Does the full length tube and cat create enough backpressure to protect my valvetrain? I realize every car is different but I'm wondering if anyone has encountered a similar situation or heard about one.

__________________
I make your Grandma's Buick look fast.

Last edited by bclark89; 11-25-2008 at 11:20 PM..
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 11-25-2008, 11:57 PM   #2 (permalink)
Master EcoModder
 
Ryland's Avatar
 
Join Date: Jan 2008
Location: Western Wisconsin
Posts: 3,903

honda cb125 - '74 Honda CB 125 S1
90 day: 79.71 mpg (US)

green wedge - '81 Commuter Vehicles Inc. Commuti-Car

Blue VX - '93 Honda Civic VX
Thanks: 867
Thanked 433 Times in 353 Posts
back pressure in exhaust is a bad way to put it, exhaust systems fallow the same rules as wind interments, the cold air could come back up the tail pipe because the exhaust is a pulse and to large of a tail pipe is making go out of tune and creating weird waves echoing back.
I have no heard of modern cars having the problems you speak of due to over sized exhaust, but over sized exhaust tends to do more harm then good performance wise unless the engine is running at higher revs then it was designed to run at under normal use leaving it to run poorly at normal speeds, it is however a problem if you have a cracked exhaust manifold that is letting a cold draft hit the valves, cold air will bend them.
  Reply With Quote
Old 11-26-2008, 12:37 AM   #3 (permalink)
Master EcoModder
 
Join Date: Mar 2008
Location: Edmonton, AB, Canada
Posts: 531
Thanks: 11
Thanked 12 Times in 11 Posts
The rule that I have seen is you dont run an engine without the exhaust manifold(s) or it will warp the valves. Just running a bigger pipe post manifold is not going to do it.
  Reply With Quote
Old 11-26-2008, 12:42 AM   #4 (permalink)
Moderate your Moderation.
 
Join Date: Nov 2008
Location: Troy, Pa.
Posts: 8,919

Pasta - '96 Volkswagen Passat TDi
90 day: 45.22 mpg (US)
Thanks: 1,369
Thanked 430 Times in 353 Posts
engine less header == garbage engine.

Two things happen here... the pulses of air allow the air to be pushed out at pressure, then lower pressure occurs when the valve closes, so air rushes back in around it, cooler than the valve is.

The other thing is that when exhaust is vented into freeair, it can still be on fire, since there is no method of arresting flame (another job that the manifold does.) This basically intensifies the effect of the first problem, according to the tech at BOCES.

If you think that having a wider open pipe will actually cause a problem with your car, watch a drag race on TV one day... see the top fuel dragsters? They don't technically even have a header. THey just have individual pipes that vent the exhaust (and fire).

If this were a problem, this could be a prime example of how to not do it.
__________________
"ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"

  Reply With Quote
Old 11-26-2008, 01:14 AM   #5 (permalink)
Master EcoModder
 
Join Date: Jan 2008
Location: Victoria , Australia.
Posts: 499
Thanks: 20
Thanked 46 Times in 33 Posts
bclark89 , Welcome to the place and enjoy your stay.

To answer your question...simply put NO. Cold air entering the exhaust tailpipe and working it's way up to the engine and bending valves , damaging springs etc is total rubbish.

To start if it IS cold air it is going to sink not rise. The warmer air in the exhaust system will tend to stay there until it cools , then drops. Any other air will be warmed as it progresses along the exhaust system in any case.

Back pressure is the result of exhaust systems built to a cost factor not a design. Most car makers fit whatever is cheapest to achieve their goals of weight , noise reduction and packaging dimensions. Performance is a low consideration. Even warranty claims rate higher for them !

Whatever GM fitted as standard would have been well tested before it was bolted in there.

Cheers , Pete.
  Reply With Quote
Old 11-26-2008, 08:45 AM   #6 (permalink)
EcoModding Apprentice
 
Join Date: Nov 2008
Location: Nashotah, WI
Posts: 206

Fokus - '12 Ford Focus SE
90 day: 31.53 mpg (US)

Lecksus - '03 Lexus RX300
90 day: 17.61 mpg (US)

Benzzzzz - '11 Mercedes Benz ML-350 4-Matic
90 day: 19.48 mpg (US)
Thanks: 0
Thanked 8 Times in 6 Posts
The theory of the valves being damaged comes from the test that was made after an engine was run without any exhaust, then allowed to cool and taken apart. It was found that as cold air hit the hot valve it warpped the valve haveing cold air hitting it from one side. Top Feulers have individual runners because of the great mass of gasses that have to be expelled as well as the tuning is for a specific RPM. They can't have a collector system, theres too much heat that would back up into the engine. The fire you see coming out of the exhaust is actually hydrogen igniting as it hits the atmosphere. I Learned this when I worked on The Past Blue Ribbon Charger NHRA Top Fuel Funny Car in the seventies, not a bad part time job for an 18 year old kid.
__________________
"The Stone Age did not come to an end because we had a lack of stones, and the oil age will not come to an end because we have a lack of oil" ; His Excellency Sheikh Ahmed Zaki Yamani (Saudi Arabia Oil Minister from 1962 to 1986)


https://ecomodder.com/forum/em-fuel-...ehicleid=10608
  Reply With Quote
Old 11-26-2008, 11:18 AM   #7 (permalink)
EcoModding Apprentice
 
dichotomous's Avatar
 
Join Date: Nov 2008
Location: vermont
Posts: 142

CivySi - '03 honda civic SI
90 day: 31.99 mpg (US)
Thanks: 0
Thanked 1 Time in 1 Post
with the stock headers, midpipe and cat, your oversized exhaust will ONLY sound bad, it wont do a thing to performance at all.
__________________
  Reply With Quote
Old 11-26-2008, 12:23 PM   #8 (permalink)
EcoModding Apprentice
 
Join Date: Nov 2008
Location: Nashotah, WI
Posts: 206

Fokus - '12 Ford Focus SE
90 day: 31.53 mpg (US)

Lecksus - '03 Lexus RX300
90 day: 17.61 mpg (US)

Benzzzzz - '11 Mercedes Benz ML-350 4-Matic
90 day: 19.48 mpg (US)
Thanks: 0
Thanked 8 Times in 6 Posts
thats right, and it most likely will hurt your preformance, ask any Harley engine builder about all those loud staggered pipes, They sound cool but time and time again they've prove this on a dyno the horsepower went down.
__________________
"The Stone Age did not come to an end because we had a lack of stones, and the oil age will not come to an end because we have a lack of oil" ; His Excellency Sheikh Ahmed Zaki Yamani (Saudi Arabia Oil Minister from 1962 to 1986)


https://ecomodder.com/forum/em-fuel-...ehicleid=10608
  Reply With Quote
Old 11-26-2008, 12:49 PM   #9 (permalink)
Moderate your Moderation.
 
Join Date: Nov 2008
Location: Troy, Pa.
Posts: 8,919

Pasta - '96 Volkswagen Passat TDi
90 day: 45.22 mpg (US)
Thanks: 1,369
Thanked 430 Times in 353 Posts
Quote:
Originally Posted by guudasitgets View Post
thats right, and it most likely will hurt your preformance, ask any Harley engine builder about all those loud staggered pipes, They sound cool but time and time again they've prove this on a dyno the horsepower went down.
Quote:
Originally Posted by dichotomous View Post
with the stock headers, midpipe and cat, your oversized exhaust will ONLY sound bad, it wont do a thing to performance at all.
If that's true, how are cat-back manufacturers and tuners alike showing off dyno runs where a cat-back exhaust system outflows stock and nets 5-15 HP gains?
__________________
"ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"

  Reply With Quote
Old 11-26-2008, 01:18 PM   #10 (permalink)
EcoModding Apprentice
 
Join Date: Nov 2008
Location: Nashotah, WI
Posts: 206

Fokus - '12 Ford Focus SE
90 day: 31.53 mpg (US)

Lecksus - '03 Lexus RX300
90 day: 17.61 mpg (US)

Benzzzzz - '11 Mercedes Benz ML-350 4-Matic
90 day: 19.48 mpg (US)
Thanks: 0
Thanked 8 Times in 6 Posts
Quote:
how are cat-back manufacturers and tuners alike showing off dyno runs
I cut and pasted the reason. Selling these to people that beleive them. They are in the business to sell things remmember. I'm sure Honda would love to up the MPG on the base civic, I don't see any test the factory did on there road cars with a big pipe on it. They could still make it quite with a larger diameter exhaust. For road use for the average driver the gains are minimal. Christ I know your only 23 and a lot of younger car guys fall victim to marketing and can get caught up in advertizing, ending up with spending all your money on something that "sounds" really cool but in the long run little or no real gain. Sure it will produce more power, at top RPM, with a muffler in the system and it would show up on a track too. But in a daily commute a larger exhaust it won't make that much diffrence. Get some pics of that prodject and lets see what you have, maybe theres something we can help you with on it.

__________________
"The Stone Age did not come to an end because we had a lack of stones, and the oil age will not come to an end because we have a lack of oil" ; His Excellency Sheikh Ahmed Zaki Yamani (Saudi Arabia Oil Minister from 1962 to 1986)


https://ecomodder.com/forum/em-fuel-...ehicleid=10608
  Reply With Quote
Reply  Post New Thread


Tags
exhaust

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Comparing Warm Air Intakes (WAI) & Cold Air Intakes (CAI) toomuch EcoModding Central 23 05-26-2019 06:41 AM
Honda IACV explained TomO Off-Topic Tech 16 12-21-2015 02:49 AM
Hot Air intake vs. Cold Air... why or why not? Blister General Efficiency Discussion 3 10-09-2008 11:01 AM
Grill block affected milleage mar5ka Aerodynamics 24 08-31-2008 11:17 AM
Moving air intake into the engine compartment? pasadena_commut Aerodynamics 5 07-25-2008 04:24 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com