Anyone have opinions regarding performance ships or performance exhaust systems, Thank tou
Performance chips and performance exhaust systems inquiry
- Thread starter Fred West
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I don’t think the chips do anything great. There were/are some Doug Thorley headers out there. I don’t of any actual dyno gains or any other brands available.
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Thank you for taking the time to share your knowledge Brake Weight
Those who have installed the Doug Thorley headers have had great things to say about them.
Dan Kuntz posted a Dyno with a 40 hp increase if I'm not mistaken. He did an entire header and back custom exhaust though with free flowing cats.
Regarding software, I read a while back that Lexus didn't leave much on the table for performance increases. I don't recall the source so it could just be internet/forum lore.
I plan to install the headers/cats in the future. Not as much for the HP gain but for clearance, weight and increased MPG. Any HP and torque increases will certainly be welcome though.
Dan Kuntz posted a Dyno with a 40 hp increase if I'm not mistaken. He did an entire header and back custom exhaust though with free flowing cats.
Regarding software, I read a while back that Lexus didn't leave much on the table for performance increases. I don't recall the source so it could just be internet/forum lore.
I plan to install the headers/cats in the future. Not as much for the HP gain but for clearance, weight and increased MPG. Any HP and torque increases will certainly be welcome though.
I did indeed! The long tubes and custom exhaust REALLY opens up the OEM exhaust. It is almost criminal how restricted it is.
I read on a URD review that the crushed section of pipe in the OEM Y-Pipe is actually double walled and is even more restrictive than it appears.
I don't doubt for one second there's huge gains to be had with a V8 and the factory exhaust.
I don't doubt for one second there's huge gains to be had with a V8 and the factory exhaust.
I changed out my OEM muffler with a the longest high quality Magna Flow high performance 2.5" muffler they make; and my butt dyno didn't notice any real gains...just more noise (though a V8 does sound nice). I have modified exhaust on countless motorcycles, cars and trucks over the past 45 years and usually I can feel some gains somewhere in the low end, mid range or top end with a freer flow. Again, I didn't noticed gains on the GX so the stock muffler flows fairly well IMO.
If you look at the front of the exhaust you can see where the stock pipe of the driver's bank is really crimped down when it goes into the passenger side bank and then into one pipe. This must really effect the exhaust flow on the GX and I agree it is criminal how they crimped it down. There is a company that makes nice true radius bends cross over pipe to replace the stock but you also lose the front cats which could be a problem depending on where you live.
There is no real room to run a true dual exhaust over the rear axle at least with a stock or 2" lift. (Anyone with a 3" plus lift know if two pipes will go over the axle?) True dual's would probably open it up some especially with the Doug Thorley headers and high flow cats but you would need to run the exhaust exit before the rear axle and you would probably have a lot of drone. Also, the 4.7 is a low end grunt engine so it may like a little back pressure anyway. So, my point is, unless you can go fully headers back custom you might not gain much.
If you look at the front of the exhaust you can see where the stock pipe of the driver's bank is really crimped down when it goes into the passenger side bank and then into one pipe. This must really effect the exhaust flow on the GX and I agree it is criminal how they crimped it down. There is a company that makes nice true radius bends cross over pipe to replace the stock but you also lose the front cats which could be a problem depending on where you live.
There is no real room to run a true dual exhaust over the rear axle at least with a stock or 2" lift. (Anyone with a 3" plus lift know if two pipes will go over the axle?) True dual's would probably open it up some especially with the Doug Thorley headers and high flow cats but you would need to run the exhaust exit before the rear axle and you would probably have a lot of drone. Also, the 4.7 is a low end grunt engine so it may like a little back pressure anyway. So, my point is, unless you can go fully headers back custom you might not gain much.
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I did long tube headers, 2.5 to 3" HO GESi cats from vibrant performance, a 3" SS pie cut cat back, and a HO vibrant performance muffler with a 1/4 wave tube for highway drone. It really woke up the 4.7 in my non-vvti 03
How much does it cost (ballpark) to purchase and install the Thorley headers? And is a high-flow cat required to achieve the aforementioned HP and fuel efficiency gains?
Thanks!
Thanks!
I’d say that high flow cats would be necessary.
Don't forget that the '05+ have 2 cats per bank although only the first cat on each bank is monitored by the O2 sensors. '03-04 have one on each bank and one after the Y-pipe. Long tube headers and 1 cat per bank will reduce back pressure considerably.
So glad there’s a thread on this topic, and, in particular, the DT headers. This mod is one I’ve had my eye on since before I snagged my GX.
is there a good resource y’all know of about these headers and emissions compliance in different states? Hesitant to reach out to DT directly after the whole debacle with their info about CA emissions compliance.
is there a good resource y’all know of about these headers and emissions compliance in different states? Hesitant to reach out to DT directly after the whole debacle with their info about CA emissions compliance.
There's also a lot of good info here Toyota-4Runner.org Not exactly the same, but pretty similar.
Does GA have a sniffer test? If not, I would imagine that as long as you had a CAT on both sides, you would be fine. Especially if you used the Vibrant GESI CAT's like Dan did. They flow well and do a good job for emissions.
GA is weird with emissions testing. Something like only 13 counties have testing. No sniffer test. They do OBD test, gas cap test, and “a visual inspection of the catalytic converter to check for tampering or removal.”
I haven’t had to get emissions tested on my GX yet. So no idea how strict the visual inspection is.
will be moving to CO or the PNW this August. Really confused by aftermarket exhaust parts and emissions law.
would aftermarket parts not be emissions-legal even if you still had cats and fully function O2 sensors? Would these parts somehow pollute more than OEM ones?
I haven’t had to get emissions tested on my GX yet. So no idea how strict the visual inspection is.
will be moving to CO or the PNW this August. Really confused by aftermarket exhaust parts and emissions law.
would aftermarket parts not be emissions-legal even if you still had cats and fully function O2 sensors? Would these parts somehow pollute more than OEM ones?
