Acceleration problems 192
05-31-2012, 10:59 AM
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Acceleration problems 192
Hi,
I am looking for a little bit of advice. My Mazda rx8 is very sluggish on acceleration and will not rev past 7000 rpm when in gear. The car was running fine yesterday. I have uploaded a video of the problem. Any advice would be greatly appreciated.
Dan Evans
I am looking for a little bit of advice. My Mazda rx8 is very sluggish on acceleration and will not rev past 7000 rpm when in gear. The car was running fine yesterday. I have uploaded a video of the problem. Any advice would be greatly appreciated.
Dan Evans
05-31-2012, 11:06 AM
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That looks like you cat is clogging up. Next time you drive, and have trouble like that, pull over, hop out of the car, take a look under at the cat, specifically around the O2 sensor. It is almost certainly glowing from the internal heat.
It basically acts as a restrictor to the exhaust flow, not allowing the engine to breath more than a certain amount of air. Most cat failures are shortly after ignition failures or flooding, and when they start, it degrades rapidly. "fine" yesterday and trouble accelerating past 7k today means that tomorrow it's probably going to drop to 5 or 6k. Within the next 2-3 days of normal driving, you can expect to have your gas mileage drop to around 9mpg, and struggle to reach 50mph. At that point, you are doing damage to your engine and O2 sensors by trying to continue, plus risking a fire from the glowing cat.
It is highly recommended that you cease driving until you can either remove the cat (and replace with a midpipe) or replace the cat. Engine damage and fires HAVE happened.
I'm not just trying to scare you, but it's important you understand the severity of the problem if your cat is clogged.
It basically acts as a restrictor to the exhaust flow, not allowing the engine to breath more than a certain amount of air. Most cat failures are shortly after ignition failures or flooding, and when they start, it degrades rapidly. "fine" yesterday and trouble accelerating past 7k today means that tomorrow it's probably going to drop to 5 or 6k. Within the next 2-3 days of normal driving, you can expect to have your gas mileage drop to around 9mpg, and struggle to reach 50mph. At that point, you are doing damage to your engine and O2 sensors by trying to continue, plus risking a fire from the glowing cat.
It is highly recommended that you cease driving until you can either remove the cat (and replace with a midpipe) or replace the cat. Engine damage and fires HAVE happened.
I'm not just trying to scare you, but it's important you understand the severity of the problem if your cat is clogged.
06-01-2012, 06:50 AM
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OK Kwik fit have taken a look and said its defiantly the CAT that's at fault. They want to charge me £574.65 for a replacement is this a good price? I have managed to get another quote for £350. Do you think the cheaper one will be just as good?
Thanks
Thanks
06-01-2012, 07:14 AM
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I am not sure of the exchange rate, and how it might shift due to origination shipping charges, but here in the US, the OEM cat is $1,300 USD if you have the failed one to hand back, $2,600 USD if not.
The only catalytic converters that can hold up under the rotary's heat are nearly as expensive. Anything cheaper simply means that it can't survive. Many other cats can blow out in as little as a couple visits to red-line under full throttle. Some survive a few thousand miles. HJS looks like it's European based, and one of the "known good" options, so that might be a good route for you to consider.
This is obviously for the US, but bits that you can use.
The only catalytic converters that can hold up under the rotary's heat are nearly as expensive. Anything cheaper simply means that it can't survive. Many other cats can blow out in as little as a couple visits to red-line under full throttle. Some survive a few thousand miles. HJS looks like it's European based, and one of the "known good" options, so that might be a good route for you to consider.
This is obviously for the US, but bits that you can use.
Catalytic Converter
The OEM cat is $1,300 USD (it's actually $2,600, but the dealer gets a $1,300 rebate from turning in the old one, so it shows up as a $1,300 charge). Unfortunately, our engines are hell for cats. Too much heat and the cats burn out. Too much fuel/oil and the cat clogs up. Guess what? We run really hot with lots of excess unburnt fuel and oil. The average lifespan of an OEM cat is about 50,000 to 60,000 miles. It gets shortened considerably through deflooding, and coil/wire/plug failure. A failure of a single coil can destroy the cat in very short order.
If the cat fails, you don't have many options. Either A) get it replaced by the dealer under the federally mandated 8yr 80,000 mile warranty (US only), B) find a used cat for sale on the forums, C) replace it with a cat of another brand, D) replace it with a catless midpipe.
Getting it replaced under warranty will become increasingly harder to do as our cars age in years and miles. Replacing it with a used cat will also become much harder as we burn through them. The aftermarket cat selection is pretty dismal as well, unfortunately. They simply aren't designed to deal with what we put through our exhaust pipes. Yes, there are a few cats out there that CAN hold up as well as an OEM cat. But they cost nearly as much or more than OEM. If you are putting an aftermarket cat on your RX-8 that cost you less than ~$1,000 USD brand new, then understand that it's entirely possible that your cat will fail again, much much sooner than your OEM cat, even without ignition failure or flooding.
There is only 1 cat that is cheaper than OEM that is "known good": HJS motorsports cats. They are designed for high heat racing applications, and are typically just the cat itself, that you will need to get welded into an existing pipe. (Need reference information on which ones physically fit and can also take the flow, as they have many different specs and grades)
Keep in mind that cat clogging in our car is seriously destructive. Excess pressure in the engine, gas mileage drop to less than 10mpg, O2 sensors get burned out, and on the severe end of things, your car can catch fire. Yes, it's happened.
The OEM cat is $1,300 USD (it's actually $2,600, but the dealer gets a $1,300 rebate from turning in the old one, so it shows up as a $1,300 charge). Unfortunately, our engines are hell for cats. Too much heat and the cats burn out. Too much fuel/oil and the cat clogs up. Guess what? We run really hot with lots of excess unburnt fuel and oil. The average lifespan of an OEM cat is about 50,000 to 60,000 miles. It gets shortened considerably through deflooding, and coil/wire/plug failure. A failure of a single coil can destroy the cat in very short order.
If the cat fails, you don't have many options. Either A) get it replaced by the dealer under the federally mandated 8yr 80,000 mile warranty (US only), B) find a used cat for sale on the forums, C) replace it with a cat of another brand, D) replace it with a catless midpipe.
Getting it replaced under warranty will become increasingly harder to do as our cars age in years and miles. Replacing it with a used cat will also become much harder as we burn through them. The aftermarket cat selection is pretty dismal as well, unfortunately. They simply aren't designed to deal with what we put through our exhaust pipes. Yes, there are a few cats out there that CAN hold up as well as an OEM cat. But they cost nearly as much or more than OEM. If you are putting an aftermarket cat on your RX-8 that cost you less than ~$1,000 USD brand new, then understand that it's entirely possible that your cat will fail again, much much sooner than your OEM cat, even without ignition failure or flooding.
There is only 1 cat that is cheaper than OEM that is "known good": HJS motorsports cats. They are designed for high heat racing applications, and are typically just the cat itself, that you will need to get welded into an existing pipe. (Need reference information on which ones physically fit and can also take the flow, as they have many different specs and grades)
Keep in mind that cat clogging in our car is seriously destructive. Excess pressure in the engine, gas mileage drop to less than 10mpg, O2 sensors get burned out, and on the severe end of things, your car can catch fire. Yes, it's happened.
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