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Correcting for EFI mixture lag


TomoHawk

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It seems to me that when you stomp on the gas pedal, it takes a few seconds for the EFI to catch up to throttle opening wide or the RPMs.  Is that about right?  I think modern cars can react faster so you don't notice it, but when you are on the highway or a country two-lane road and you want to pass,  having to wait 10 seconds (forever) can be scary, especially if you see a truck coming your way.

Is there anything you can so with the Bosch L-Jet to help with that condition? 

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The system is supposed to add 27% more fuel than the base pulse when the full throttle switch in the TVS is actuated.  The other consideration is cam profile, which is designed to really kick in at about 3000 RPM, I believe.  If you hit the gas at 2000 RPM, it might be that 1000 RPM climb that you're really waiting on.  You might just need to drop down a gear.

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Maybe a test drive with the camera rolling will give a better idea of what you are describing. agree with others should be smooth pickup anything over 2k but will not happen quickly until you get over 3k for the power band to get lively. If its back firing or mis firing you have an issue.

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Unfortunately, the car is put away for the winter, but I will be making a script to carry out, as this stuff like ZedHead suggests sounds reasonable.

But usually, I keep light pressure on the gas, so the revs are probably about 2000 - 2300, for 45 or 55MPH (for country roads.)

Too bad you can hook up the BT OBD recorder, like the other car has.  Recording the engine tach would not be easy, unless you can hang a smartphone around your neck, but I will see if I can fab up a bracket or something.

Edited by TomoHawk
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On 12/2/2016 at 11:19 PM, Zed Head said:

The system is supposed to add 27% more fuel than the base pulse when the full throttle switch in the TVS is actuated.

How can you verify that, unless you have an air-fuel meter?  AFAIK,  the TPS and coolant sensors, etc., are working, and I checked all the input lines to the ECU connector within the last few years.

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I think that an oscilloscope would tell you more.  Look at injector open duration.

You could go to Megasquirt or a later model Nissan EFI system with Nistune if you want to try something better.  Most of us don't have a lag when we hit the gas though so it's hard to say if you have a problem with your system or if it's how you drive it.  Your original question was essentially "is it right to wait a few seconds for engine pickup after pressing the throttle wide open", and the answer seems to be "no".

Small engines need to be in the right RPM range to be responsive.  I could drive my old Pontiac 400 engine around in 2nd or 3rd gear for most situations and it would still go when I hit the gas.  And it was only a 3 speed.  400 cubic inches versus 168.

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  • 2 weeks later...

If this is happening with an automatic and it isn't down shifting at 50- then you have a transmission issue. Make sure there are no vacuum leaks at the trans. Your right- in third gear it's not going to do much when you floor it at 45mph.
By the way - there is a manual override on that year and model.


Sent from my iPhone using Classic Zcar Club mobile

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