Z hesitates when I give it gas
Z hesitates when I give it gas
Just purchased 2005 350z and my friend purchased a 2003 Z. We switched and drove each others cars and I was amazed how much more punch his had when you gave it gas. Both of our cars are stock touring editions, except mine is the 35th anniversary. Mine also has an aftermarket air filter (stock airbox is removed). I'm wondering if the problem is the aftermarket air filter and I would like to find a stock air box and change it back. Do you think this is the problem or should I look elsewhere? Help, my friend is giving me hell for having a new Z with less miles and ...less git up and go!
Understanding "HEAT SOAK"
by: Chris Bloom, CJB Fire Consultants
Copyright 1995
by: Chris Bloom, CJB Fire Consultants
Copyright 1995
...The phenomenon known as "heat soak" occurs when the engine is turned off. At this
time, the combustion process is terminated. This terminates the momentum of the
crankshaft, which in turn stops the turning of the water pump. As the coolant is no longer
being circulated, the engine block and cylinder temperature increase for a period of
approximately 3 to 10 minutes, depending on the engine design and additional
components.
During this time, the engine block radiates heat to the air surrounding the engine, which
slowly cools the engine. However, the cooling process occurs slowly, and as a result, the
temperature of the engine block transfers the heat to the coolant. The coolant
temperature then increases, which in turn increases the pressure inside the coolant
system. This is why the vehicle's coolant temperature gauge increases over a period of
time after the engine has been turned off.
Ethylene or Propylene Glycol has a flash point of approximately 210°F,3 and an ignition
temperature of approximately 500°F to 700°F.4 If there is a break, rupture, or leak in any
of the connections of the coolant, the coolant will be forced out at a high pressure, spraying
an atomized mixture of fluid inside the engine compartment. If the coolant contacts the
exhaust manifold, which is typically operating at a temperature of 900°F to
1100°F5, the coolant will reach temperatures greater than its ignition temperature and
probably result in a fire
temperature of approximately 500°F to 700°F.4 If there is a break, rupture, or leak in any
of the connections of the coolant, the coolant will be forced out at a high pressure, spraying
an atomized mixture of fluid inside the engine compartment. If the coolant contacts the
exhaust manifold, which is typically operating at a temperature of 900°F to
1100°F5, the coolant will reach temperatures greater than its ignition temperature and
probably result in a fire
3
Source: NFPA 325M, Fire Hazard Properties of Flammable Liquids,Gases,and
Volatile Solids, National Fire Protection Association, 1991 Edition.
4
Source: Kirk's Fire Investigation, Third Edition, pg. 174
5
Source: Kirk's Fire Investigation, Third Edition, pg. 174
Source: NFPA 325M, Fire Hazard Properties of Flammable Liquids,Gases,and
Volatile Solids, National Fire Protection Association, 1991 Edition.
4
Source: Kirk's Fire Investigation, Third Edition, pg. 174
5
Source: Kirk's Fire Investigation, Third Edition, pg. 174
BTW... That rattling sound coming from the transmission after installing a lightweight flywheel isn't clutch chatter either, but I've given up on trying to explain that one.
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David, I think the chance of a glycol fire is remote at best, so I wouldn't be offering that as the reason why heat soak is bad. LOL. The more obvious and practical detrimental effect is decreased performance from lowered mass air, which is what you were responding to anyway. 
For the OP, if the car is hesitating, then something may be off with the tune. You can try an ECU reset (battery disconnect overnight) to see if the computer can readjust trims appropriately. You may also want to check for vacuum leaks in the intake system or exhaust leaks (which can lead to erroneous AFR feedback).
For the OP, if the car is hesitating, then something may be off with the tune. You can try an ECU reset (battery disconnect overnight) to see if the computer can readjust trims appropriately. You may also want to check for vacuum leaks in the intake system or exhaust leaks (which can lead to erroneous AFR feedback).
Last edited by rcdash; Jul 21, 2009 at 02:30 PM.
David, I think the chance of a glycol fire is remote at best, so I wouldn't be offering that as the reason why heat soak is bad. LOL. The more obvious and practical detrimental effect is decreased performance from lowered mass air, which is what you were responding to anyway.
That's the point I was making.
...and you're right, the chance of a glycol fire is extremely remote.
Thanks folks! I plan to switch back to the stock airbox just as soon as I can find one for sale. Nissan wants your first born to buy one new so I need to find a used one. If that doesn't cure it I will start looking for leaks and reset the ECU. I'll let ya know what happens.
It's a miracle! Bought a stock airbox from a forum member and installed it last night. The old girl has got some pep in her step now! The difference is like night and day. Thanks for everyone's assistance. Just wait til I see my friend and his 03. I'm gonna blow his doors off!
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