Finally made the damn install appointment!
02-12-09, 10:01 AM
#61
Lexus Champion
I am VERY surprised the stock cat cracked. If you can take a picture that would be great.
Cats generate a LOT of heat as they catalyze the exhaust chemicals. Their cases are built with this in mind and are tough. Most common is a problem with the core material which can melt and or clog and or crack.
You could substitute an aftermarket core by cutting and welding the stock flanges to the new cat. This would require building a jig off the stock cat, cutting the flanges off, cutting the new cat case, aligning and welding the old flanges to the new cat. This then becomes a bolt in. If a future replacement is needed you will have the jig. I am not certain if there is a left and right cat or if each is the same.
Regardless, your exhaust noise was present right after the header install. This would NOT be caused by the headers. Most likely the part had a hairline crack already and was stressed by removing and re-installing.
Keep us posted.
Stock cat Y pipe end:
Cats generate a LOT of heat as they catalyze the exhaust chemicals. Their cases are built with this in mind and are tough. Most common is a problem with the core material which can melt and or clog and or crack.
You could substitute an aftermarket core by cutting and welding the stock flanges to the new cat. This would require building a jig off the stock cat, cutting the flanges off, cutting the new cat case, aligning and welding the old flanges to the new cat. This then becomes a bolt in. If a future replacement is needed you will have the jig. I am not certain if there is a left and right cat or if each is the same.
Regardless, your exhaust noise was present right after the header install. This would NOT be caused by the headers. Most likely the part had a hairline crack already and was stressed by removing and re-installing.
Keep us posted.
Stock cat Y pipe end:
02-12-09, 12:34 PM
#63
Thanks J for the assistance. I will keep you advised on this issue. As a little side note. I was running a PO430 code for a while (but no odd noise) BEFORE I replaced all O2 sensors...now I have no codes (for the last 2 mos) but have this exhaust leak noise. I want to get this fixed ASAP.
Could it be that my cats were getting overheated by bad readings from bad O2 sensors resulting in the computer throwing the PO430 code at that time? If so, I could have permanently damaged one of the cats and others may be on their way out as well for all I know.
Could it be that my cats were getting overheated by bad readings from bad O2 sensors resulting in the computer throwing the PO430 code at that time? If so, I could have permanently damaged one of the cats and others may be on their way out as well for all I know.
02-20-09, 08:03 PM
#66
Lexus Test Driver
I could be wrong here... but aftermarket hi-flow cats tend to be a waste of time if you find your stock cats too restrictive... just delete the cat and get an 02 simulator instead of spending money on a hi-flow cat which may still perform inefficiently...
like i said.. i could be wrong.. just my .02
like i said.. i could be wrong.. just my .02
02-20-09, 08:09 PM
#67
I could be wrong here... but aftermarket hi-flow cats tend to be a waste of time if you find your stock cats too restrictive... just delete the cat and get an 02 simulator instead of spending money on a hi-flow cat which may still perform inefficiently...
like i said.. i could be wrong.. just my .02
like i said.. i could be wrong.. just my .02
02-21-09, 08:17 AM
#68
Lexus Champion
Rock is right... stock cats probably outflow most aftermarket "high flow" cats.
Back to back testing of a GS430 Y pipe, which has a center single cat, was the SAME power as with a GS400 Y pipe which has a center resonator (straight through open pipe design).
Cats also act as a one way check valve which tends to help low speed response and power. Peak power at high RPMs is probably under 10rwhp going catless and less at lower RPMs. No need to pollute needlessly and of course risk the consequences of a citation.
Back to back testing of a GS430 Y pipe, which has a center single cat, was the SAME power as with a GS400 Y pipe which has a center resonator (straight through open pipe design).
Cats also act as a one way check valve which tends to help low speed response and power. Peak power at high RPMs is probably under 10rwhp going catless and less at lower RPMs. No need to pollute needlessly and of course risk the consequences of a citation.
04-11-09, 01:33 PM
#69
Well, I just got back from getting my car dyno'd...finally.
I am a little embarassed and a little sad and have a sense of defeat.. $250 dollars later (cost of re-tune and dyno pulls). I am NOT dropping anmore money into this car to make it faster; the only way to make a REAL difference is FI hands down or throw one of those HP Lextreme longblock engines in there.lol
The results:
45 degrees and rainy
281.8whp
306wtq
13.2 a/f correction (the tuner mentioned that since I have cats on my car I am really probably running 12.9 but he mentioned that it wasn't making anymore power by leaning it out anymore so he left it at those numbers.
I screwed up in a boatload of posts I had previously written and I apologize to my CL friends...I thought my car previously made 269.4whp (so I rounded to 270whp) and 295wtq. When in reality the tuner pulled up my last year's results and it was 267.1whp and 291wtq. So my TRUE net gains from the headers and a re-tune with the Apexi Neo are: +14.7whp and +15wtq.
Just to show the importance of a correct tune - before he started the re-tune he conected the Neo and changed a setting (that I messed up on accident right after I got the headers installed; it was the MAF sensor setting) in order to start the car.
If you all recall I was upset right after the header install because I said it felt like my car LOST power...well in my case IT DID! Today, when he reconnected it with the old tune he was getting 263whp max (today's baseline) whereas pre-header with correct tune I got 267.1whp (last year). So the overall gain from what I was running with since I got my headers is probably close to 20whp and 20-25wtq (because the Neo had been disconnected this entire time).
So, in order for a GS400 to achieve 265-270whp and 290-295wtq you will have to have the following mods:
Intake
Exhaust
A/F controller
With the above list and addition of headers you will see 280-285whp and 305-310wtq.
So overall gains (from bone stock) with I/H/E and A/F controller is roughly 40-45whp and 55-60wtq. "Assuming" that there is in fact a 20% loss in power due to the drivetrain my car is now at ~353hp and ~383tq (the torque numbers may be inflated a bit due to my torque converter though).
So there you have it guys. The car feels GREAT though and VERY quick I noticed a lot more ooomph especially of the line but I really couldn't "test" too much today because as mentioned earlier in this post it is raining today.
Thanks for following my modding threads and results.
I am a little embarassed and a little sad and have a sense of defeat.
. $250 dollars later (cost of re-tune and dyno pulls). I am NOT dropping anmore money into this car to make it faster; the only way to make a REAL difference is FI hands down or throw one of those HP Lextreme longblock engines in there.lolThe results:
45 degrees and rainy
281.8whp
306wtq
13.2 a/f correction (the tuner mentioned that since I have cats on my car I am really probably running 12.9 but he mentioned that it wasn't making anymore power by leaning it out anymore so he left it at those numbers.
I screwed up in a boatload of posts I had previously written and I apologize to my CL friends...I thought my car previously made 269.4whp (so I rounded to 270whp) and 295wtq. When in reality the tuner pulled up my last year's results and it was 267.1whp and 291wtq. So my TRUE net gains from the headers and a re-tune with the Apexi Neo are: +14.7whp and +15wtq.
Just to show the importance of a correct tune - before he started the re-tune he conected the Neo and changed a setting (that I messed up on accident right after I got the headers installed; it was the MAF sensor setting) in order to start the car.
If you all recall I was upset right after the header install because I said it felt like my car LOST power...well in my case IT DID! Today, when he reconnected it with the old tune he was getting 263whp max (today's baseline) whereas pre-header with correct tune I got 267.1whp (last year). So the overall gain from what I was running with since I got my headers is probably close to 20whp and 20-25wtq (because the Neo had been disconnected this entire time).
So, in order for a GS400 to achieve 265-270whp and 290-295wtq you will have to have the following mods:
Intake
Exhaust
A/F controller
With the above list and addition of headers you will see 280-285whp and 305-310wtq.
So overall gains (from bone stock) with I/H/E and A/F controller is roughly 40-45whp and 55-60wtq. "Assuming" that there is in fact a 20% loss in power due to the drivetrain my car is now at ~353hp and ~383tq (the torque numbers may be inflated a bit due to my torque converter though).
So there you have it guys. The car feels GREAT though and VERY quick I noticed a lot more ooomph especially of the line but I really couldn't "test" too much today because as mentioned earlier in this post it is raining today.
Thanks for following my modding threads and results.
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cazzola (02-18-21)
04-11-09, 06:35 PM
#72
http://www.youtube.com/watch?v=K_ND_OlmCLc
Warm-up and tuning
http://www.youtube.com/watch?v=o3zg5Vdg8fA
One of the last runs of the day...
I will upload both last year's and today's dyno sheets on Monday when I get to work; I don't have a scanner at home.
Warm-up and tuning
http://www.youtube.com/watch?v=o3zg5Vdg8fA
One of the last runs of the day...
I will upload both last year's and today's dyno sheets on Monday when I get to work; I don't have a scanner at home.
The following users liked this post:
cazzola (02-16-21)
04-11-09, 06:39 PM
#73
I thought the headers would have gained me 17-18 as what others have said and I figured with a synergistic effect that a re-tune of the Neo would squeeze out another 3-4whp. I was wrong on both counts. Only managed to gain around 14-15whp with both the headers and the re-tune. Oh well, I'll live. There's always hope for an ISF in the next year or so perhaps. I wish our cars weren't so damn heavy because they DO make decent power and they are well built.
04-11-09, 07:22 PM
#75
Nice numbers, did you ever test a 0-60 time or 1/4 mile time before the headers? also how much did all this modification cost you? was it worth it and do you recommend it to others? Can't remember are you running a full catback or just rear exhaust?