Thread: Low speed drivability issues

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2012-11-16 21:51:23

#21

OnTheChip

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Originally Posted by Evlnxr

Was going to upload some tcl files but they are not allowed by the forum.

Car started to do a really nasty bucking on light/zero load at low speed tonight, gets a real resonance going.

Was going down a hill quite slowly in 2nd, and it seems to be as soon as it hits 1500rpm while decelerating it starts to buck, like 1 second intervals on off on off. Fuel cut and tps closed tags are not changing, i was starting to wonder if my throttle cable was causing the throttle to open and close, but im fairly certain its not that at this stage. I am running a N1 throttle body and had considered making a new cable attachment with a cam action to reduce throttle response at small movements.

Timing was moving between 15deg and 25deg as it was doing this, i had changed the idle ignition from 1000rpm to 1500rpm to try fix the problem, changed them all back to 15 deg and the problem got ever so slightly better but maybe 10% better. Did another test and FIV is constant but the bucking is still there.

Have you tried using the stock values in the TP Min table?

Dave

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2012-11-17 04:06:59

#22

lynchfourtwenty Online/offline status of lynchfourtwenty is unknown

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well what did you "tune" to fix it?

also i dont have an o2 sensor, its turned off and im using non feedback values as well as turned off long term fuel trim (LTFT)

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2012-11-17 04:13:35

#23

gio94sr20ve Online/offline status of gio94sr20ve is unknown

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Sounds like your going lean on those tables. I have dealt with the bucking and sensitive throttle in the low Rpms. I would reverse most of your changes, map trace where it's bucking and add fuel in those cells.

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2012-11-17 07:47:11

#24

Evlnxr

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Originally Posted by dfddfd2

Originally Posted by Evlnxr
Was going to upload some tcl files but they are not allowed by the forum.

Car started to do a really nasty bucking on light/zero load at low speed tonight, gets a real resonance going.

Was going down a hill quite slowly in 2nd, and it seems to be as soon as it hits 1500rpm while decelerating it starts to buck, like 1 second intervals on off on off. Fuel cut and tps closed tags are not changing, i was starting to wonder if my throttle cable was causing the throttle to open and close, but im fairly certain its not that at this stage. I am running a N1 throttle body and had considered making a new cable attachment with a cam action to reduce throttle response at small movements.

Timing was moving between 15deg and 25deg as it was doing this, i had changed the idle ignition from 1000rpm to 1500rpm to try fix the problem, changed them all back to 15 deg and the problem got ever so slightly better but maybe 10% better. Did another test and FIV is constant but the bucking is still there.

Have you tried using the stock values in the TP Min table?

Dave

Ive never changed the TP min values from the stock Nemu file, but will look at them and see.

I suspect its something to do with fueling, but im kinda happy with how it idles and cruises. I might get a mate to drive for me so i can datalog and make changes. Its very easy to make it do the problem, so hopefully it will be easy to tell when the issue is solved.

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2012-11-17 08:14:46

#25

Evlnxr

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Originally Posted by lynchfourtwenty

well what did you "tune" to fix it?

also i dont have an o2 sensor, its turned off and im using non feedback values as well as turned off long term fuel trim (LTFT)

I dont have narrowband o2 either, had thought about connecting the Innovate narrowband wire up, but im not running a cat converter, and i prefer leaner cruise than 14.8 . Might be worth wiring it up anyway to have a play, easy enough to flag it on and off.

I havent managed to fix this issue at all yet. I adjusted the idle ignition timing, values under 1000rpm were 15deg, and 1000 to 1500 were 25, so when the car had the fault the FIV was rocking between 15 to 25 deg, changed values to 15deg, and the problem was pretty much the same.

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2012-11-17 13:10:45

#26

OnTheChip

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Originally Posted by Evlnxr

Ive never changed the TP min values from the stock Nemu file, but will look at them and see.

You're right, my bad. Was looking at the wrong values.

Dave

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2012-11-17 20:57:46

#27

Boostlee

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Originally Posted by lynchfourtwenty

well what did you "tune" to fix it?

also i dont have an o2 sensor, its turned off and im using non feedback values as well as turned off long term fuel trim (LTFT)

As mentioned, I figure it is running "lean" in those tables so I "tuned" it out by adding fuel. Quiet simple

When doing my tuning, I disabled my stock O2, did the tuning, changed my target A/F ratio and then re-enabled stock O2 feedback.

However, I tackled the low speed driveability with the O2 disabled.

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2012-11-17 21:42:59

#28

Evlnxr

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Does the A/F target map in Tunercode/Nismotronic affect narrow band o2?

Will try some more fuel in there and see what happens, im picking this is going to be the final answer.

Cheers

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2012-11-18 20:27:22

#29

JKTUNING

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Originally Posted by Evlnxr

Does the A/F target map in Tunercode/Nismotronic affect narrow band o2?

Will try some more fuel in there and see what happens, im picking this is going to be the final answer.

Cheers

No.. at this time the target AFR is simply for log comparison ONLY.

In the new version you will have a target AFR table that will be used for closed loop wideband feedback.. this table WILL adjust fueling to try to maintain your target AFR.

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