Last post on Jan 30, 2011 at 8:49 AM
You are in the Mazda CX-7
What is this discussion about?
Mazda CX-7, SUV
#39 of 57 Re: Fix for the CX7 Clanging Noise in Engine with the Black smoke out the back [slw5]
Apr 12, 2009 (4:41 pm)
Good to see you are still around. I am the other owner you were referring to.
It seems this issue only affects the 2007 model year using California's lower 91 octane fuel. The service bulletin has the dealer replace the Variable Valve Timing actuator and install a new ECU form a 2008 model. In 2008 Mazda changed the ECU to enable the engine to use lower octane fuel. I had always used premium
but here in Cali it was only 91 octane. Our car no longer has this issue and is running great. The problem is getting the dealer to acknowledge the issue.
#40 of 57 Re: Fix for the CX7 Clanging Noise in Engine with the Black smoke out the back [zoom49]
Apr 12, 2009 (6:55 pm)
Good to see you as well!
I am so thankful they were able to verify my issue and yours. I would have sat there till hell froze over before they actually would have done anything with my name at the top of the list for the specialist. McGee did a great job on my behalf and my car is like a completely different car. I love it now!!!
Our tech guy at work is a Mazda enthusiast & he drove it probably the way it was meant to be driven using the gears and all and came back smiling!!! Of course, he told me the reason I don't get good gas mileage is because I'm a lead foot, but how could I be anything other than that driving a CX-7?!?!?!
#41 of 57 Re: Temper [slw5]
Apr 21, 2009 (8:03 pm)
I have had a weird white smoke when idling the vehicle cold, has only happened about 3 times in the 2 years I have owned the vehicle....
Never had black smoke and dont notice turbo lag....
#42 of 57 Re: Temper [sdbobo619]
Mar 21, 2010 (2:36 pm)
Mazda CX7 Smoke After Idle Like this? Been having the same smoke problem for about a year now, and they're finally approved for a turbo replacement next week.">link title
#45 of 57 CX-7 Turbo Lag......NOT....!!
Aug 24, 2010 (11:02 am)
1-2 second re-acceleration downshift delay...YES!!
abolition hesitation wwest -dfg
#46 of 57 CX-7 HORRID FE.....
Aug 24, 2010 (11:22 am)
Turbocharged engines MUST be designed to run in detuned/derated mode, "off-boost", 99% of the time. Intercooled turbo boost on a DFI engine must NOT cause the effective compression ratio to rise to the point of detonation. There are two reasons why a turbocharged engine is handicapped for use during idle or constant speed cruising, resulting in HORRID FE in comparison to a N/A engine.
1) You cannot take advantage of intercooled boost pressure if the base/native compression ratio is already near the point of the onset of detonation, knock/ping due to dieseling. A normally aspirated DFI engine can easily accommodate a base/native CR or ~12:1. Throw in a turbo and you'll consider yourself lucky to have a base/native CR of 8:1, maybe even as high as 9.8:1 if you're really lucky.
2) In order to reduce turbo lag the CR is lowered even moreso in order to put more of the energy of A/F mixture combustion into the exhaust manifold where it can be, is used, to spin the turbine up most quickly.
An Atkinson cycle DFI engine can have a base/native CR as high as 15:1, but can NEVER be turboed due to the unusually high efficiency compared to the standard "Otto" mode engine. With an Atkinson cycle engine virtually ALL of the energy of the A/F mixture combustion is used to push the piston downward. Typically only enough energy left in the exhaust to keep the catalyst heated to operational temperature, >800F.
#47 of 57 Re: CX-7 HORRID FE..... [wwest]
Aug 28, 2010 (11:07 am)
Does this mean that 4 cylinder DISI direct injection spark ignition engines with single turbos like the cx-7 are inherently weaker engines with noticeably less of a service life than naturally aspirated engines even with regular oil changes?
Driving the turbo 4 cx-7 com pared to a naturally aspirated 4 cylinder competitor is amazing. Manually shifting through the 6 speeds really blows the others away, but of course the mpg is probably less. Achieving about 21.5 mpg in town using premium fuel.
#48 of 57 Re: CX-7 HORRID FE..... [fonefixer]
Aug 28, 2010 (9:51 pm)
"..inherently weaker engines.."
In the sense that it needs the turbo to produce a reasonable level of HP/torque, then yes. But in the sense of reliability the turbo engine is likely to be a bit more robust mechanically. Remove the turbo or wire the wastegate fully open, and this engine's reliability would probably be extended substantially over an equal displacement engine that wasn't turbo "prepped".