RX Twin Exhaust
05-10-07, 05:45 AM
#17
Lexus Test Driver
Having 2 mufflers such as on the MDX will have a little less exhaust restriction, but you will not notice it in everyday driving. 1 muffler, 2 muffler, most dual exhaust these days are for show only.
05-10-07, 06:26 AM
#19
Super Moderator
I am still of the opinion that most SUVs have engine power determined in large part by their weight, with some exceptions for certain packages or needs.
05-10-07, 07:20 AM
#20
It is not crazy, it is a little naive for one to assume 270 HP is avaliable at any time.
270HP is a the peak power at ONE RPM. Just watch your technometer, does one ever drive at one RPM? You take a significant hair cut from that peak HP at low RPM. With RX300, one would never exceed 3000 RPM if RX300 is left to shift on its own. Take a look at RX350 spec, what RPM is the peak HP achieved at, does one EVER get to that RPM during normal driving?
270HP is also at the crank, there is >20% powertrain loss when power is delivered to the wheels. Power are used to turn axle, pulley, accessories, wheels, tires, gears. That is another hair cut on top of the low RPM one.
Exhaust usually gives benefits at the high RPM range. Stock exhausts main goal is to muffle sound using by restricting the flow, which is the cheapest method that requires least amount of engineering. Unfortunately, restriction kills more power than other expensive and challenging methods such as absorption and reflection.
270HP is a the peak power at ONE RPM. Just watch your technometer, does one ever drive at one RPM? You take a significant hair cut from that peak HP at low RPM. With RX300, one would never exceed 3000 RPM if RX300 is left to shift on its own. Take a look at RX350 spec, what RPM is the peak HP achieved at, does one EVER get to that RPM during normal driving?
270HP is also at the crank, there is >20% powertrain loss when power is delivered to the wheels. Power are used to turn axle, pulley, accessories, wheels, tires, gears. That is another hair cut on top of the low RPM one.
Exhaust usually gives benefits at the high RPM range. Stock exhausts main goal is to muffle sound using by restricting the flow, which is the cheapest method that requires least amount of engineering. Unfortunately, restriction kills more power than other expensive and challenging methods such as absorption and reflection.
Last edited by TunedRX300; 05-10-07 at 11:14 PM.
05-10-07, 10:22 AM
#21
not everyone has a rx350, a lot of us have the rx330. anyways i think the 350 is underpowered also, not as bad as the 330 but still. how could you say that most dual mufler exhuast systems are for show? there will be some gain going with an upgraded exhuast system as long as it is properly tuned. the gain wont be as big compared to a car thats turbo or supercharged, but a gain nontheless. if you want something for show just replace the stock exhaust tips.
05-10-07, 11:21 AM
#22
Acura has upgraded MDX's exhaust over the year. Early years of 1G MDX has a single exhaust just like the RX. Then the dual exhaust came even though the 3.5L V6 has not changed.
The 2007 MDX is the 2G from Acura, exhaust designs are complex and advanced. The manifold exhaust headers are casted into the engine to reduce weight. But the most significant design improvement is actually a variable flow dual exhaust, implemented at the mufflers. Here is a description of it.
http://www.hondanews.com/categories/712/releases/3758
CLOSE-COUPLED CATALYSTS AND VARIABLE FLOW EXHAUST SYSTEM
As in the Acura RL™, the exhaust manifolds of the MDX are cast directly into the aluminum alloy cylinder heads to reduce weight and put the engine's two primary catalytic converters as close as possible to the combustion chambers. The 600-cell per-square-inch, high-efficiency converters mount directly to the exhaust port of each cylinder head for extremely rapid converter light-off after the engine starts. A significant weight savings and reduction in parts count is realized by eliminating traditional exhaust manifolds.
Downstream of the close-coupled catalyst, a hydroformed 2-into-1 collector pipe carries exhaust gases to a single secondary converter under the passenger cabin. This high-flow unit has a revised shape and a large 62mm outlet (up from 55mm). Downstream of the underfloor catalyst, the system splits flow into a pair of underfloor chambers (the previous MDX used a single chamber) to give the exhaust note a more refined sound. Dual silencers near the rear fascia incorporate an exhaust pressure-activated valve to balance the engine's need for proper exhaust back pressure at low speed and free flow at high speed. With the valve in each silencer closed, the exhaust sound level is muted for quiet cruising. When exhaust flow increases sufficiently due to high rpm and a large throttle opening, the silencer valves open and provide a secondary exit path inside the silencer chamber. In total, the MDX's exhaust system refinements improve flow potential by 18%.
As in the Acura RL™, the exhaust manifolds of the MDX are cast directly into the aluminum alloy cylinder heads to reduce weight and put the engine's two primary catalytic converters as close as possible to the combustion chambers. The 600-cell per-square-inch, high-efficiency converters mount directly to the exhaust port of each cylinder head for extremely rapid converter light-off after the engine starts. A significant weight savings and reduction in parts count is realized by eliminating traditional exhaust manifolds.
Downstream of the close-coupled catalyst, a hydroformed 2-into-1 collector pipe carries exhaust gases to a single secondary converter under the passenger cabin. This high-flow unit has a revised shape and a large 62mm outlet (up from 55mm). Downstream of the underfloor catalyst, the system splits flow into a pair of underfloor chambers (the previous MDX used a single chamber) to give the exhaust note a more refined sound. Dual silencers near the rear fascia incorporate an exhaust pressure-activated valve to balance the engine's need for proper exhaust back pressure at low speed and free flow at high speed. With the valve in each silencer closed, the exhaust sound level is muted for quiet cruising. When exhaust flow increases sufficiently due to high rpm and a large throttle opening, the silencer valves open and provide a secondary exit path inside the silencer chamber. In total, the MDX's exhaust system refinements improve flow potential by 18%.
05-10-07, 11:44 AM
#24
The quote is from a official Honda link.
I agree Lexus never intend to design RX as a performance SUV, but then again, major luxury brand such as Infiniti, MB, BMW, Acura never separate luxury from performance. Even Porsche has position itself as a luxury and even industry leading reliable brand.
05-10-07, 12:11 PM
#25
Lexus Test Driver
You are right, almost every luxury brand aim higher as far as performance. Lexus is the only luxury brand right now that seems to head toward a diff. direction. Lexus is more focus designing a quiet and comfortable SUVs. They try to built a customer base with good customer service. I think the bottom line is that Lexus is trying to sell to a difference audience. I think Lexus has done their marketing research. Most people who buy Luxury SUV care more about comfort than performance, that is why Lexus is selling so well.
05-10-07, 12:31 PM
#26
G Man, this then begs the question, why can't you have both luxury and performance? Our IS250 seems to have attributes of both, it can really scoot when asked (although the IS350 is significantly quicker and more sporting) and yet it provides a cabin that is quiet, sumptious and far and away nicer than what BMW, and Mercedes provide. I'm sure the Lexus has the capability to do the same with the RX.
05-10-07, 12:48 PM
#27
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G Man, this then begs the question, why can't you have both luxury and performance? Our IS250 seems to have attributes of both, it can really scoot when asked (although the IS350 is significantly quicker and more sporting) and yet it provides a cabin that is quiet, sumptious and far and away nicer than what BMW, and Mercedes provide. I'm sure the Lexus has the capability to do the same with the RX.
it is much more difficult to have the best of both worlds when we are talking about an SUV that adds over 1000 extra pounds in a day and age where MPG is of high concern
05-10-07, 12:51 PM
#28
Lexus Test Driver
G Man, this then begs the question, why can't you have both luxury and performance? Our IS250 seems to have attributes of both, it can really scoot when asked (although the IS350 is significantly quicker and more sporting) and yet it provides a cabin that is quiet, sumptious and far and away nicer than what BMW, and Mercedes provide. I'm sure the Lexus has the capability to do the same with the RX.
The IS is aim toward the young male drivers and the RX is aim toward middle age female owners who really dont care about speed.
05-10-07, 01:00 PM
#29
My wife will start collecting Social Security soon, and I’m eligible in a year or two. 
She drives the IS most of the time (and bags the largest quantity of speeding tickets) and when I am deemed to be on my proper behavior, she graciously allows me to drive it. 
We both drive the RX. I should mention that we are both ‘spirited’ drivers and I managed to wear out the tires on my RX before I hit 18k miles. Both vehicles get superb mileage for what they are. We average about 23 in the RX on the open road and about 17 in town (its an AWD). With the IS (also an AWD), driving close to triple digits on the open road, we are seeing a consistent 29 MPG. So, if we can have the best of all worlds in the IS, why can’t we have both Luxury and performance in the RX?
05-10-07, 01:04 PM
#30
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THe major reason i bought my Lexus was b/c of the use of regular gas. Some of the guys here behave as if lexus is God like. Anything Lexus does is A OK. So if someone says that the Lexus should have a double exhaust, they say all the manufactures that do have are just for show. IF all the other manufacturers had 300hp and lexus had 200hp, they would say that lexus knows its customer base. I love the lexus ride. I love its looks. However, there some gripes that i have that irk me. I WISH THE RX HAD A MANUAL OPTION. I which that you could tailor your RX, without having to stick to packaged options. I would love to see the atatistics on repeat RX Owners. I am not talking about the ones who lease. How many people who own an RX that actually buy another RX? My Next Suv is an X5 as long as there is still a manual option