Slant *        6        Forum
Home Home Home
The Place to Go for Slant Six Info!
Click here to help support the Slant Six Forum!
It is currently Thu Mar 28, 2024 11:58 pm

All times are UTC-07:00




Post new topic  Reply to topic  [ 28 posts ]  Go to page Previous 1 2
Author Message
PostPosted: Tue May 04, 2021 8:54 pm 
Offline
Board Sponsor & Contributor

Joined: Thu Oct 31, 2002 5:39 pm
Posts: 24233
Location: North America
Car Model:
Thank you, Greg, for reminding me why I retired from regular participation here—I needed that! :lol:

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Image


Top
   
PostPosted: Wed May 05, 2021 6:35 am 
Offline
Supercharged
User avatar

Joined: Mon Sep 26, 2005 5:09 pm
Posts: 2946
Location: Gilbert, Arizona
Car Model: 1962 Plymouth Valiant Signet
Yeah, catalytic converters do restrict flow, some more than others, but to those of us with tired, wheezy, asthmatic lungs it's probably worth the price ( no, I don't smoke and haven't in well over 50 years. There are viable high flow alternatives to the stock parts and I would urge anyone contemplating a change to look into that. If the engine is worn out and burning oil, removing the cat isn't the answer, fixing the engine is. As for the legal implications, that's your call according to your conscience... the Sherriff can't be everywhere. In many places such as the populated areas of Arizona, removing the cat isn't an option because you won't be able to legally tag the vehicle.

_________________
David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.


Top
   
PostPosted: Wed May 05, 2021 9:36 am 
Offline
TBI Slant 6
User avatar

Joined: Thu Jan 24, 2013 3:39 pm
Posts: 210
Location: Houston, TX
Car Model:
Ok I'll try posting more useful things:

3 Youtube videos:

Flowmaster: no cat vs high flow cat in a 318 with aftermarket EFI engine:
https://www.youtube.com/watch?v=OSMcHg_7eo4
Same power. These cats are high flow, and (of course) Flowmaster sell the product, so they might have looked to the better combination (whichever it is) for testing.

Youtuber: Miata turbo - factory cat vs no cat:
https://www.youtube.com/watch?v=jUS3AKgwWtc
Increase 4.9HP (1.94% increase) and 7.1 lbsft (+3.34% increase), for same turbo boost levels. You could move a larger turbo with no cat.

Heavily modified Supra, high flow cats vs no cat:
https://www.youtube.com/watch?v=Ulw0UX3iPm4
Very small difference. They do not test with factory cats, but state in the video that high flow cats are better than factory cats.

So 2 examples were high flow cats do not cause a considerable loss, and one example that shows a little gain between a factory cat and a straight pipe.

Of course a high flow cat is probably more expensive than a straight pipe. On the other side removing a cat can give you trouble with the law, with some bypasses depending on the state.

Our slant 6 are, in most cases, a low air flow engine, so a modern cat replacements of an old cat will probably not affect much the output, I believe. I also believe is a good idea avoiding contamination and I hate see and breathe clouds from coal rollers (diesel pickups with removed emission systems). I also understand it can be expensive to replace, and depending on the case there might be some gain.

I would like to see videos of people gaining more than 5% power and torque by removing a cat, specially in a low rev engine. If somebody wants to share their experience is more than welcome. I also understand that different operating conditions can provide different results (low flow vs high flow engine, turbo vs no turbo, altitude, EFI vs carburated, etc).

Now, about sound... that's is a complete different field I don't have preferences (besides not liking too much noise or droning when cruising).

My apologies if previous comments offended somebody, I hope this brings more support to the discussion. Have a great day, and keep slanting!

Disclaimer: My slant six car, being a 1969, does not have a cat, nor any of the ancillaries that were needed for the cat to work correctly (lean carb, smog pump, etc), so it easier to maintain. I use it as a show and weekend cruiser, not as a daily driver.

_________________
/6 Dodge Charger 69
Image...there's nothing like using the "Search" link above to solve most of your problems...


Top
   
PostPosted: Thu May 06, 2021 9:48 am 
Offline
3 Deuce Weber
User avatar

Joined: Sun Mar 27, 2005 6:55 am
Posts: 84
Location: Cayce, SC
Car Model:
There are plenty of trucks around here that at certain RPMs have a very raspy blat blat tone that almost sounds like cavitation. Is this from standing waves in the exhaust? Most of these have outragously large pipes that would look more at home on a locomotive. Is there a point where an oversized pipe causes a loss in power? On older cars and trucks I seem to remember the pipes after the muffler were always smaller than the head pipes. An older mechanic once told me this was to compensate for the smaller volume of the cooler gasses past the muffler. Any truth to that? I don't know.

Scott.


Top
   
PostPosted: Thu May 06, 2021 9:06 pm 
Offline
TBI Slant 6

Joined: Tue Nov 25, 2014 9:14 pm
Posts: 127
Location: Alberta, Canada
Car Model: 62 Valiant
Jase wrote:
Doctor Dodge wrote:
A lot of today's exhaust system's R&D work (and dollars) are spent to get the "right" sound out the tailpipe.

You now see a lot of "funny things" in a new vehicle's exhaust system and some of those things are there to get the sound that the manufacturer wants to hear.
DD
Killer6 wrote:
Compact manifolding & small head-piping absoluely affect emissions, it reduces cold catalyst warm-up time, one of the few really incomplete systems left on modern ICEs. Plans are slowly, or finally coming around to heat-assist the cat electrically,..ie all O2 sensors, but cold weather/start is one "dirty" condition that persists.
Russet 'tater? BS. Only if failed or damaged. We're not discussing race aps.


OK, I can easily understand there is R&D work going on to get a certain sound.. And emissions is also a topic for $$ spent.. Can someone explain why a 3.7 Jeep has 2 3/8" head pipes? That flies in the face of good emissions... so it must be there for some other reason. The muffler is also huge, so I am imagining they want to keep it fairly quiet, and not obnoxious.. I want to believe that the huge head pipe is for something to do with the power curve. . . . BUT I've got no science to back up my imagination..


an easy to get insane gas mileage and 300 HP from a 3.7L motor is to reduce losses. think about the exhaust on a 300 hp 318. somewhere in that same range of pipe? figure the new v6 isnt making as much power internally or it would burn more fuel so its making sure more of it gets to the drivetrain by not wasting it pushing harder on the exhaust gasses, burning the fuel as completely as possible, etc


Top
   
PostPosted: Tue May 11, 2021 9:55 pm 
Offline
EFI Slant 6

Joined: Sat Mar 19, 2016 7:25 pm
Posts: 359
Location: SW PA
Car Model:
Lol, where to start...
Size of headpipes etc., simply a matter of mfr.'s priority, ouput/sound/warm-up time, as I'm not aware of a "time to active" std. mandated for emissions yet. Trucks have more leeway than cars/light SUV's & that gives more options to the mfr.
With the now-common high voltage systems in EV/HEV's, heated catalysts will probably become the same 'til the ICE is forced into an un-natural retirement. Heated cats were a preliminary parameter for OBDII at it's inception, but only recently poised to become available 25yrs later.
Uhh, the 3.7/4.7l OHC engines have a modern "Poly" chamber with better ports, ahead of it's time, now semi-copied by "twisted-wedge" heads. Add engine management &You have superior efficiency, which equals
1)More power-same fuel consumption
2)Same power-less fuel consumption
Most pumping losses are not in the exh., it's the heads, look at how contorted the pipes are on a Northstar Caddy are vs. hp/ci.


Top
   
PostPosted: Thu May 13, 2021 2:27 pm 
Offline
Turbo EFI
User avatar

Joined: Wed Nov 23, 2011 11:07 am
Posts: 2125
Location: SF Bay Area
Car Model: 67 dart 2 door hardtop
Re: droning.

I built my exhaust. It starts with Dutra Duals, 2" pipes into Y pipe 2.5" collector. Probably didn't need 2" down pipes, regardless the 2.5 goes back to the muffler, then 2.25 out of the muffler and then to a small resonator (glass pack) at the tail pipe, outlet is 1.75". All worked well, but I had a horrible drone under my seat, so due to the straight 2.5" section back to the muffler. I installed a perforated SS tube 2" in diameter about 3' long (using spacers so it was centered concentrically within the larger pipe). That not only completely stopped the drone (likely broke up a standing wave as you suggested) but the sound during acceleration is awesome. It sounds like a small V8, throaty but quiet low tones. I checked for any back pressure under load, and there was none to speak of, so it's free flowing.

FYI,

Brian

_________________
https://tinyurl.com/yynpj4v2


Top
   
PostPosted: Thu May 13, 2021 5:30 pm 
Offline
Supercharged
User avatar

Joined: Sat Nov 27, 2004 8:03 pm
Posts: 8977
Location: IRWIN PA
Car Model:
'67 Dart 270 wrote:
I checked for any back pressure under load, and there was none to speak of, so it's free flowing.

FYI,

Brian


How do you test/ check for that in the exhaust?

Greg

_________________
http://www.youtube.com/hyperpack
Image


Top
   
PostPosted: Thu May 13, 2021 8:28 pm 
Offline
EFI Slant 6

Joined: Sat Mar 19, 2016 7:25 pm
Posts: 359
Location: SW PA
Car Model:
With a backpressure gauge, silly! No, really, just a low pressure gauge kit with an adapter that screws into an O2 bung. Generally anything 1.5psi & down is considered good testing a cat-converter. More is worse, less is bettah!


Top
   
PostPosted: Thu May 13, 2021 9:38 pm 
Offline
Board Sponsor & Contributor

Joined: Thu Oct 31, 2002 5:39 pm
Posts: 24233
Location: North America
Car Model:
Attachment:
447.jpg
447.jpg [ 248.11 KiB | Viewed 2755 times ]

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Image


Top
   
PostPosted: Fri May 14, 2021 6:31 pm 
Offline
EFI Slant 6

Joined: Sat Mar 19, 2016 7:25 pm
Posts: 359
Location: SW PA
Car Model:
Ja, that's how We used to do it, thankfully no longer. Still works, though for moving obstructions that don't rattle, the real-time direct pressure rocks.


Top
   
PostPosted: Mon May 17, 2021 4:20 pm 
Offline
Turbo EFI
User avatar

Joined: Wed Nov 23, 2011 11:07 am
Posts: 2125
Location: SF Bay Area
Car Model: 67 dart 2 door hardtop
Yep, exactly, used the O2 bungs in each downpipe. Note: I tested it under real load, not just revving in the garage, but driving it. Ran the pressure line through the firewall, and duct taped the pressure gauge to the dash by the radio.

_________________
https://tinyurl.com/yynpj4v2


Top
   
PostPosted: Sat May 22, 2021 4:14 pm 
Offline
Supercharged
User avatar

Joined: Sat Nov 27, 2004 8:03 pm
Posts: 8977
Location: IRWIN PA
Car Model:
'67 Dart 270 wrote:
Yep, exactly, used the O2 bungs in each downpipe. Note: I tested it under real load, not just revving in the garage, but driving it. Ran the pressure line through the firewall, and duct taped the pressure gauge to the dash by the radio.



So basically just a vacuum / pressure gauge line into the O2 Bung?

Sounds easy enough!


Thanks for the gauge reference tuning chart Dan!

Greg

_________________
http://www.youtube.com/hyperpack
Image


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 28 posts ]  Go to page Previous 1 2

All times are UTC-07:00


Who is online

Users browsing this forum: No registered users and 92 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited