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i am thinking about eliminating all 3 resonators on my 97 and leaving the stock mufflers at the back so it looks stock.
looking under my car, the center resonator is not a straight flow. i know this is not a cat, but why this design? the 98-00 i believe are straight through as mentioned in this thread.
My pipes are all stock except from the first Y to the back right exit is a single crush bent 3" for a matter of months now.
I want to shift the torque band down and retain/gain low-mid end for hill climbs during the weeks for my hiking/trial running routines + regular driving. As of currently with the crushed 3", I find that I'd have to be in 2nd and blast away unecessarily or lump around steadily slow in 3rd. It does see high rpms very often on the freeway or if roads are long and open.
Talked to a bender/exhaust manuf. They said that the crushed 3" is too disruptive and has slow exhaust velocity and suggested I should be going with a mandrel 2.5 as that'll retain tq curve low-mid better than a crushed 3" and still will gain a little bit up top with that type of driving I do. It does seem disruptive as the OEM Y to a single 3 is a **** merge but if I recall the single 3 is a bit smaller overall than dual 2 1/4
They do not have any jigs/molds of LS400 piping so the rest of it will be as follows
- From the cats 2.25 > OEM Y > single 2.5 for the massive low-mid torque
- OEM everything and just 2.5 single from the Y
- Leave it as is
- 2.25 > better transition cone to the current 3" single
- 2.25 > better transition cone to mandrel 3"
- Someone can add other viable proper idea here
(OEM Y because has been stated to be good? I also have a 3" magnaflow Y from another vehicle if applicable )
The header and collector sizes are more crucial to not losing bottom end torque. After the collector the exhaust expects to see atmosphere or a tapering exhaust pipe.
The length of the '97 LS400 exhaust system is right according to the exhaust design program I have, PipeMax.
The OE header is so miserable I can't think about it for very long without getting angry and feeling betrayed by Toyota. Also the 45 degree "bend" after the catalytic converters.
Starting with 2" after the catalytic converters and stepping up to 2.5" where the left and right merge into the "Y" is what PipeMax suggests considering the OE header and cats are still used. It would be similar if the whole exhaust was replaced.
Originally Posted by timmy0tool
i am thinking about eliminating all 3 resonators on my 97 and leaving the stock mufflers at the back so it looks stock.
looking under my car, the center resonator is not a straight flow. i know this is not a cat, but why this design? the 98-00 i believe are straight through as mentioned in this thread.
pic from tommyUCF20 for reference:
The first thing I was gonna do is make an electrically actuated exhaust cut out between the 1st resonator and 2nd "Y" split so I could hear my exhaust when I wanted to. If the 1st resonator didn't sound very good then I would replace it with something that does and also flows well.
You might wanna try to remove the exhaust after the first resonator and see just how well it flows and sounds before replacing it. It might work real well even though not a straight thru design.
The attached image depicts the post-catalytic convertee exhaust transition and downstream oxygen sensor. No questioning room for improvement here. This post posits whether removing the post-cat sensor from the exhaust stream will realize performance benefits, while maintaining emissions and efficiency. So looking at the percentage of obstruction (5-10%?) and turbulence created by the sensor probe suggests a cost effective way for improvement. On the 1999 LS400, according to the shop manual suggests the post cat sensor takes random samplings to determine if the cats are functioning, but do not actially influence ECU with air/fuel mixture. (Unlike newer cars..2006+) so removing from the exhaust stream but not actually eliminating can be achieved with a tunable oxygen sensor extender. At times these devices are used to facilitate passing emissions, but that is not the goal here. Appreciate comments here.
The Oxygen sensor probe is a major restriction...and its turbulence exacerbates this. While ordinarily the sensor should reside in the middle of the exhaust stream, this sensor does not influnce ECU air/fuel mixture but monitors randomly whether cats are performing.
This engineered extender is a bolt in for 1999 LS400 through earlier 1995-2000 LS400. I would not use inserts and would consider shortening housing to bring tip of post -cat oxygen sensor closer to perimeter of exhaust pipe - the goal is not to defeat it's purpos but relocate it from exhaust st ream
have you done a pressure test before and after the sensor to know its costing power?
cause usually with a slight restriction it just means faster exhaust flow in that area. and would be minimal really..
just dont see why you would throw money at a presumed restriction without hard evidence..
and if it was a problem it would have been fixed by factory..
The Thanksgiving Holiday explains my reason for not responding to you sooner....
First, thank you for considering whether I was the beneficiary of a dynomometer, airflow meter, gas temperature analyzer, and gas analyzer.
In an effort to generate some thought and be helpful..consider the following;
Your concerns would be more capably answered, resolved expediently and on a practical interim basis mathematically obviating the necessity for physical testing.
We know the fixed dimension of the exhaust pipe where the post-catalytic converter oxygen sensor resides.
We know that the physical presence of the oxgen sensor probe not only creates primary disruption to exhaust flow, but resulting secondary turbulence, which further disrupts exhaust flow velocity, and trust there is agreement it cannot increase engine power because if it did then the OEM's would be inserting probes wherever possible.
Attached is an image of a Denso oxygen sensor depicting the size of the probe typical of one extending into the LS400 exhaust, post-catalytic converter area, which, due to arguably poor design, consists of extremely sharp angular transitions and significant pipe diameter reduction, all within 6".
This spells unnecessary resistance to exhaust flow, if not for the transitions alone, then for the increased turbulence.
What is required to analyze benefits of relocating the post-catalytic converter oxygen outboard of the exhaust stream are dimensions of the relevant component areas to derive and compile data providing mathematical primary and secondary exhaust flow disruption.
My very conservative estimate simply based on the area ratio or probe to pipe, not factoring in turbulence, is 5-8% restriction.
As to Toyota not taking care on the efficiency of the LS400 exhaust design, we observe LS430 exhaust system evolution as evidence the LS400 exhaust system offered significant room for improvement and have attached Lexus images of both generations for comparison.
As reported in the Lexus shop manual, the downstream oxygen sensors primarily serve the more limited purpose of reporting catalytic converter fitness to the ECU.
On information, newer makes of automobiles, circa 2006 forward,(?) the downstream oxygen sensors more actively addresses the ECU, thus limiting this modification to older models, such as an LS400 or even LS430.
Finally, if you still harbor concerns regarding my discernment, have a look at my posts on the more efficient LS430 water inlet housing(eliminates two 90 degree transitions...) succesfully transplanted onto my LS400, another posting containing evolution of Denso injectors and how improvements to power, efficiency and emissions could benefit LS400 owners, and so forth.
The purpose of this post was to solicit input on possible gains this unintrusive and inexpensive modification can reasonably expect.
Anyone care to contribute?
Thank you
A Denso oxygen sensor
LS430 Exhaust Diagram.fewer harsh transitions
LS400 Exhaust System exhibiting design issues resolved in the LS430
Personal exhaust update: decided to throw some cash into the pipes, went from oem Y > 3" aeroturbine > 3" single crush bend to removing the entire 3" section after the aeroturbine to a small 2.5 resonator > 2.5 single crush bend.
I probably wasted money as mentioned anything after headers are negligible but my main concern was removing a chunk of drone and having more "usable" torque through the range. That it did make quite a noticeable difference on both variables. Noise from intake side can be heard more audibly since overall exhaust noise went down; did the housing cut out with the headlight gasket removal.
Anyone got a free dyno to throw it on? bay area resident.
Getting some PPE headers into the 98ls400 seems extremely hard to do and maybe requires some hammering/denting.
3" single? Interesting choice. I did the complete cat-back, 2.25 to x-pipe back to 2.25, to a pair of magnaflow mufflers.
PPE makes '98-00 LS400 headers, only a little bit of grinding for a bit of casting flash is needed (on the block). Otherwise the bolt-in on both ends just fine, to OEM cats and all. Not cheap though.
3" single? Interesting choice. I did the complete cat-back, 2.25 to x-pipe back to 2.25, to a pair of magnaflow mufflers.
PPE makes '98-00 LS400 headers, only a little bit of grinding for a bit of casting flash is needed (on the block). Otherwise the bolt-in on both ends just fine, to OEM cats and all. Not cheap though.
I'm nearing 2 years on my PPE headers. Love them.
I am currently thinking of 3 options for my next decision if I do decide anything on the exhaust at this point.
- What you have; mandrel 2.25" to x-pipe
- Mandrel 16 or 18ga single 3" (inner diameter should be around 2.7x" ?? )
- 2.5" single mandrel. Inner diameter of 2.3x on a 16ga might be too small.
If this is all futile without the headers or cat delete I'll leave it as is. What do you think?
Was the PPE an easy direct bolt in for you? It was a long time ago since I inquired them for a quote but I think they mentioned about possibly having to hoist the block out or something along those lines.
How do you like your exhaust set up? It seems as if torque delivery can be possibly more even running a dual with X than a Y to single.
OEM Y to single
+ less weight
+ cost less
- perhaps distortion in exhaust pulses
- perhaps more sensitive to piping size
dual with X
+ linear flow characteristics across the range (will this be the deciding factor if extremely true)
- cost
- weight
sure the headers have will lead in determining power but the cat back piping is also a factor. most of what i read in the past involve post cat 2.25" piping to an x-pipe then dual out for better scavenging of gasses for a smoother flow. as the exhaust from one bank is flowing through the x-pipe, it pulls or scavenges the air in the other bank aiding in better flow, as it is in the ls430 exhaust. the single exit design, in my opinion anyways, is not ideal as it restricts more of that overall flow as it exits. lexus designed a dual exhaust for a reason.
if you want more "usable" low end torque, consider an h-pipe to dual, though you won't get the sound if you utilized an x-pipe. x-pipes are for torque in the upper RPM band.
lastly, do NOT delete the cats. they are already high flowing and will get considerably louder if eliminated unless that's your goal. there is minimal gain with their removal so why bother?
After doing some reading I did also find that the cats also flow well. As for the x-pipe, I was thinking that perhaps a longer x-pipe maybe a good course of action. Now I'm wondering if some of these mufflers in example; Magna tru-X, Dynomax X are they true X's inside and if it is that case can be a beneficial to get a longer X. These muffler casings usually can get over 20 inch in just the body where the X is entire length of it.
Does Yodaone suggest moving the o2 sensor downstream?
Anyone have success with a hemholtz resonator to get rid of the low rpm throttling interior resonance? I find that this car / 1uz motor has minimal drone aside from the "low rpm throttling". I believe someone in the SC or GS forums may have done it. Been a long time since I found the post, just came to memory.
I believe in the end I will also go with x-pipe 2.25 dual like others have and suggested. Was thinking about going 16ga, the inner diameter would actually be .xx smaller than the OD" and that'll be good to maintain velocity. The thicker gauge would cut down significant interior resonance as I have noticed on my e23 7 series. It had 2.5 crush bent aluminium (not sure OD/ID but just regular thin pipe from exhaust shops) to a borla pro xs muffler; Same 2.5 Stainless steel (type of metal plays a roll in acoustics) in 16ga was put on and interior noise/droning decreased significantly. I feel that the e23 should have gone 3" due to being a 3.8 stroker but the power it makes doesn't call for it. hmm well that's a different matter unless anyone can chime in on that
How much does piping expand when at operating temperatures I wonder.
Don't worry about resonance until after you've got the rest of your exhaust layout installed. The resonance can change when you change the layout and even components.
I would advise against a muffler/x-pipe combo, they just don't flow as well as normal x-pipes. If you want something a little better flowing look into "siamese" style x-pipes, or a fancy dual merge collector x-pipe.
aluminum exhaust piping isn't done in the normal market, you may be thinking of aluminized steel, which is. Crush bent vs. mandrel bent flow rates are different, but the final power output will be within 3-5% in a near-stock application.
After doing some reading I did also find that the cats also flow well. As for the x-pipe, I was thinking that perhaps a longer x-pipe maybe a good course of action. Now I'm wondering if some of these mufflers in example; Magna tru-X, Dynomax X are they true X's inside and if it is that case can be a beneficial to get a longer X. These muffler casings usually can get over 20 inch in just the body where the X is entire length of it.
Does Yodaone suggest moving the o2 sensor downstream?
Anyone have success with a hemholtz resonator to get rid of the low rpm throttling interior resonance? I find that this car / 1uz motor has minimal drone aside from the "low rpm throttling". I believe someone in the SC or GS forums may have done it. Been a long time since I found the post, just came to memory.
I believe in the end I will also go with x-pipe 2.25 dual like others have and suggested. Was thinking about going 16ga, the inner diameter would actually be .xx smaller than the OD" and that'll be good to maintain velocity. The thicker gauge would cut down significant interior resonance as I have noticed on my e23 7 series. It had 2.5 crush bent aluminium (not sure OD/ID but just regular thin pipe from exhaust shops) to a borla pro xs muffler; Same 2.5 Stainless steel (type of metal plays a roll in acoustics) in 16ga was put on and interior noise/droning decreased significantly. I feel that the e23 should have gone 3" due to being a 3.8 stroker but the power it makes doesn't call for it. hmm well that's a different matter unless anyone can chime in on that
How much does piping expand when at operating temperatures I wonder.
No, not recommending relocating pre-catalytic converter Oxygen sensors to post-catalytic converter Oxygen sensors positions. Suggested only using depicted spacers between post-catalytic converter Oxygen sensors in their current position. As for resonance....Lexus employs these exhaust dampers on later LS 460/600H mufflers. Fabricate a bracket and weld to muffler and, or , resonators with proper threaded insert for mounting hardware. Also located images taken from what appears to be Lexus SUV...dampers are mounted to exhaust pipe
About $50 each from Lexus...beats having to remove the carpet to slather 100 pounds+ of expensive sound deadening materials to floorpan.
Hi guys, just wanted to drop in my two cents worth. I have been doing custom fabrication all my life and built a completely custom cat back set up for my own personal 1990 LS400.
This is what I did and it has worked great all round.
The whole system is mandrel bent S/S tubing from Woolf Air Craft Products.
From the cats I run 2.25"I.D based on the cars HP which is not a lot, at the point where the single cat would be at the rear of the trans I removed that cat and have a custom x pipe in that space, I always run an x pipe as over the years Ive found (As have many others) that this system of scavenging works well (Marginal on cars with cats) in performance applications below 650hp which my car does not make, where the x pipe truly helps in lower hp applications is in keeping the drone of an after market or custom exhaust to a minimum, again it does have to be correctly built!!.
At the point where the differential is I expanded the pipe to 2.5" I.D, reason is at this point the exhaust gas is just hot air getting cooler so the exhaust tubing just ends up being ducting, all aspects of any scavenging is out the window after the x pipe, and hanging out the back is just a set of magnaflows which are soon to be replaced with some Borla Pro XS Mufflers as the Magnaflows have approx 150,000 miles on them (As does the whole system) and they are getting loud.
I can not give you any performance increase numbers though I do now that it did improve both milage and hp slightly.
Their is no point going any larger than 2.25" I.D as their is a major restriction point at the flange of the cat were it mounts to the main exhaust system that runs under the car, If your going to remove the cats, run a tube header I still would not consider going any larger than 2.25" I.D purely based on the engines HP and TQ numbers. Anything larger will actually hinder the engines ability to perform at lower rpm.
BTW, Ive ran the Borla XS Mufflers before on other applications and they are for some reason much quieter than other mufflers Ive used over the years!!
Flow Masters are pure junk!!
Hope this may have helped, if anyone needs pictures I will be happy to post.
Sorry if im reviving a dead thread here guys but this has been the most helpful info/brains ive found so far.
Ive roughly finished making a full catback exhaust system for my 98 celsior.
I went with 2.5" piping for the whole thing (hindsight tells me i should have gone with 2.25" but a lenght of 316 stainless 2.5" pipe was freely available from my workplace)
Ive pretty much followed the exact layout of the factory exhaust and the only mufflers it has is two at the exit of the exhaust.
I bolted it in yesterday for a test drive and it has a massive drone when under load, idle is fine and volume is fine when cruising but as soon as im goin up a hill its not nice.
Im after some advice on what i can do to reduce the drone, im wanting to put a louvred/baffled resonator in after the first Y join where the pipe goes into 1 before splitting off into 2 again.
Should i go with a 2.5" resonator or if i go down to a 2.25" resonator then back up to the 2.5" pipe will that reduce noise/drone even more?
I have an old 3" straight through resonator spare from an old exhaust system that i thought of using but from what im reading it will just make the drone worse.
Any ideas?
I can upload some pics if need be.
Cheers Guys,
Ben.
10-01-14, 11:29 AM
bay area resident.
