Gas Pedal Delay

juld0zer · 05-17-2014, 08:05 PM

aside from the obvious causes (intake air temp, coolant temp and oil temps), what else could be causing this throttle lag???

I've pretty much eliminated IAT as the cause.

I'm now leaning towards the EGR system which involves the CVTC system. EGR is intended to reduce emissions by reducing combustion temperatures....by filling part of the cylinders with exhaust gas to effectively reduce the available volume for oxygen to enter/fill the cylinder.

This is no easy fit-a-blank experiment and will need someone with tuning experience to chime in... i've got an Uprev tuner license so if someone can guide me, i am happy to guinea pig my car for the benefit of everyone as we try to solve this mystery once and for all.

SouthArk370Z · 05-18-2014, 02:25 AM

Quote:

Originally Posted by juld0zer

aside from the obvious causes (intake air temp, coolant temp and oil temps), what else could be causing this throttle lag???
...

Knock sensor could be causing the problem. Going by what I've read on this site, vibration from the drivetrain or exhaust can also bang the sensor.

juld0zer · 05-18-2014, 10:43 AM

i've pondered that possibility but eliminated it because it seems a bit bizarre for an engine to develop a vibration or harmonic issue at certain operating temperatures. It's not impossible because i know the engine does vibrate a lot. I have the plastic engine covers removed and to avoid losing the nuts/bolts, i just nipped them up on the intake collector. I pop the hood once a week and 70% of them have become loose by several turns.

Cant be a bad batch of knock sensors either because of the widespread awareness of the problem.

The other issue is it seems that most people are complaining about the lag in 1st gear only. Assuming that most folks are running stock intakes, i'm willing to bet that they are experiencing heatsoak of the IAT sensor - ie, ecu sees the air entering the engine as being hotter than it actually is; due to radiant heat influences from the headers, radiator airflow etc.

There is, without a doubt a difference in throttle response between oil at 90*c or less with coolant at 87*c or less versus oil and coolant temps above these approximate figures. The simple stab-the-pedal test shows this in a no load scenario. Someone on here datalogged the lag and it clearly shows a delay of several seconds between pedal activity and throttle body activity with VDC off during a 1st gear takeoff - this was done with IAT at 104f/40c which is definitely in the high territory. This is the lag that keeps you at the lights while the wanker in the bone stock Civic takes off.

I have experienced severe 'heatsoak' by intentionally using a different IAT sensor (one which reads higher, ie different resistance curve for those familiar) and it will affect you even when you're moving. Overtaking is scary. Gaining speed takes an eternity. Not fun.

I'm wondering, for those of you with remapped throttle tables - do you still experience the acceleration lag both on take off and in-gear acceleration?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
7AT rev delay?	Vegitto-kun	Engine & Drivetrain	16	05-04-2010 05:17 PM
2 things delay in a shift and a sound 7at	jtown82	Engine & Drivetrain	19	04-03-2010 01:30 AM
Headlight delay	Jack370Z	Nissan 370Z General Discussions	7	10-30-2009 03:02 PM
A7 Upshift Delay?	hey32g	Nissan 370Z General Discussions	15	10-12-2009 11:20 AM
Automatic Downshift Delay	drdre8424	Nissan 370Z General Discussions	2	07-25-2009 10:56 PM

05-17-2014, 08:05 PM	#1 (permalink)
juld0zer Enthusiast Member Join Date: Nov 2012 Location: Sydney Posts: 428 Drives: 11 Nissan 370Z MB M6 Rep Power: 139	aside from the obvious causes (intake air temp, coolant temp and oil temps), what else could be causing this throttle lag??? I've pretty much eliminated IAT as the cause. I'm now leaning towards the EGR system which involves the CVTC system. EGR is intended to reduce emissions by reducing combustion temperatures....by filling part of the cylinders with exhaust gas to effectively reduce the available volume for oxygen to enter/fill the cylinder. This is no easy fit-a-blank experiment and will need someone with tuning experience to chime in... i've got an Uprev tuner license so if someone can guide me, i am happy to guinea pig my car for the benefit of everyone as we try to solve this mystery once and for all.

05-18-2014, 10:43 AM	#3 (permalink)
juld0zer Enthusiast Member Join Date: Nov 2012 Location: Sydney Posts: 428 Drives: 11 Nissan 370Z MB M6 Rep Power: 139	i've pondered that possibility but eliminated it because it seems a bit bizarre for an engine to develop a vibration or harmonic issue at certain operating temperatures. It's not impossible because i know the engine does vibrate a lot. I have the plastic engine covers removed and to avoid losing the nuts/bolts, i just nipped them up on the intake collector. I pop the hood once a week and 70% of them have become loose by several turns. Cant be a bad batch of knock sensors either because of the widespread awareness of the problem. The other issue is it seems that most people are complaining about the lag in 1st gear only. Assuming that most folks are running stock intakes, i'm willing to bet that they are experiencing heatsoak of the IAT sensor - ie, ecu sees the air entering the engine as being hotter than it actually is; due to radiant heat influences from the headers, radiator airflow etc. There is, without a doubt a difference in throttle response between oil at 90c or less with coolant at 87c or less versus oil and coolant temps above these approximate figures. The simple stab-the-pedal test shows this in a no load scenario. Someone on here datalogged the lag and it clearly shows a delay of several seconds between pedal activity and throttle body activity with VDC off during a 1st gear takeoff - this was done with IAT at 104f/40c which is definitely in the high territory. This is the lag that keeps you at the lights while the wanker in the bone stock Civic takes off. I have experienced severe 'heatsoak' by intentionally using a different IAT sensor (one which reads higher, ie different resistance curve for those familiar) and it will affect you even when you're moving. Overtaking is scary. Gaining speed takes an eternity. Not fun. I'm wondering, for those of you with remapped throttle tables - do you still experience the acceleration lag both on take off and in-gear acceleration?