Thread: Low speed drivability issues

Going to fix this right now.. but I do notice in the code that if you have the graphing window open while downloading the logs it WILL enable the save log button so you can save the log.

New update available which should take care of the save log function after loading from NEMU memory.

I've always had this issue in the cars i've street tuned and my own cars.

I'm pretty sure its due to the difference in timing from the "idle timing table and the main "Ignition Timing Table"

Now most sr20's should have the idle timing table at 15deg. Whats happening is when you get off/very low pedal position its going back and forth from 15deg to whats ever is in your main ignition map like 20-30 deg. Its too much of a jump in timing causing the surge.

Try lowering the values at low rpm/low load and report back

Cool thanks John, got that update.

Will try and download the nemu again and see if i can save a log. Is it possible to save to complete rom from the nemu rather than just choosing one log?

Hitting save log in graphing or the dropdown still does nothing, ive got the auto save turned off, doesnt create a file anywhere.

If i have autosave turned on, what does it use as a file name? And when does it do the autosave?

Ok, i was keeping the onboard logging window open, closed that and now when i hit save log in the dropdown menu it is coming up with a dialog box to put a file name in.

Prob not a good log to demonstrate the low speed issue, will try and get my damaged back into the car later and go for a drive and record some low speed logs.

I can understand how going from idle timing of 15deg to map timing would cause this issue, but why is it only tunercode? Stock rom file doesnt have a big drop off in timing at low load zones and doesnt have this issue. Im happy to chop more timing out of this zone if it helps and doesnt cause any other issues.

Attatched is a screenshot of my ignition table, numbers on left 2 columns used to be same as 3rd, ramping them down seemed to help a little, maybe the 1st should be 15deg and be done with it?

The stock rom has lowering timing values, thus doesnt have this issue.

Your lower rpm/low load values range from 18-32 deg. try paying attention to the first 3 colums and first 3 rows.. try this out Evlnxr

values up and above the first few colums and rows can be whatever..

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.

Ive uploaded a RAR file of my tune, plus 2 data logs of the issue. Cant load a rar file, so renamed it .tct, need to rename to .rar after downloading.

I have a feeling the car is going super lean at low load points (I JUST tuned this issue out last night on the way home). Basically the transition point from cruise/idle/vacuum conditions to load are on the lean side.

Just do a quick log of your part throttle runs. Also, just do a quick glance at your A/F ratios as you dip slightly into the throttle.

From what I have experienced (and if someone could back me up):
Lean for part throttle tip in: Get a horrible stumble/stutter before it richens up
Rich for part throttle tip in: Just seems sluggish to get up in the rev range

Let me know!

keep in mind at 1500rpm the ecu's turning the injectors back on weather your foots on the pedal or not.




i had some of these issues, but goin back to recirc'd bov helped alot.

^^^ My BOV IS currently recirculated and the issue was prevalent before I "tuned" it out.

The issue was very obvious to me as I just looked down on the gauge to verify. The stock ecu "bin" or tune does (or should) not have this issue and I do not see a reason why it can't be rectified by proper tuning with the proper tools at hand .