Typical causes of Cam Surge?

[Rawr256]

Have everything on my wife's TA dialed in except for in the low 1200 and high 1600 range or rpms the car will tend to surge if enough throttle isn't given. Scouring old posts the most typical cause is too much air from what I understand. The sum total airflow and the desired air flow both are right on top of each other with the exception of every now and than the sum total is a little less than desired, not at the points when it surges though.

Is there some point that I am missing? I have less cracker commanded than stock because stock values were putting it over the top. I have considered dropping the cells for those ranges even lower because when I first was getting it all dialed in dropping them all to 0 nearly eliminated all cam surge that was present, just had an issue of the car dieing every time the clutch was pushed in or the car was rolling to a stop. I also have thought about 0ing out the entire multiplier table for airflow but wasn't too sure how much air is really required from it.

On the wrong computer to throw up a hpt file but will possibly later today if my laptop gets a nice wifi signal with a log. Just wondering really if there are other tables I am possibly over looking besides the RAF, cracker, and follower that could be giving me problems.

[mecanicman]

What is the timing set at in this area? To much/little will cause surge. Also fueling needs to be dialed in, what does wideband say?

[Rawr256]

Timing is set in the low to mid 30s. A/f is hanging right around 14.7 - 15.3 with the wideband. Think more timing is needed? Did notice that with the timing commanded cell range if it were in the middle the was a variation of 1* that it could bounce between but didnt think it would have much impact. I made them all consistant just incase but didnt notice any difference on my drive today.

[S2H]

take it back down in the 22-28* range
if you dont have enough in the Over and underspark tables it will surge... this is your engines main way of taking care of idle with a cam.. the IAC or TB(ETC) cant move fast enough and will over compensate causing idle hunt and surge..

also may need to revisit RAF if car just dies when clutch is pressed in...

[Rawr256]

With the cracker table previously 0'd out in the 1k and 1.6k columns the car would die. Have used russ k's config Nd gistos and have it dialed im with slightly less than stock tables so its all good now.

Will try dropping the timing down around stock values and see what it does.

[jimmyblue]

In my experience the surging is due to an over-rich
idle mixture, that makes the IAC response too "soggy"
and destabilizes the idle RPM loop.

I have also seen something that (to me) looks like a
MAP-axis airflow error, which makes for a pure fuel
surge even with the IAC locked.

First thing I would do is try and dial down IAC with
the real time controls, to well below your target idle
RPM. Do it right at 800RPM first, and get that VE
column to its proper place going by the narrowbands.
If you have a high overlap cam, you will probably
want it leaner than indicated-stoich, but that would
need a wideband that's believable.

Then try and dial it down to 600RPM, and true up the
mixture there by working the 400RPM column (600 is
interpolated, so expect 2X the change to give the same
movement at 600).

A mixture that's near ideal, will respond more crisply to
"air step" fromthe IAC.

You should do all your idle tuning with the adaptive spark
disabled. This will show you the true nature of things.

Last off, at idle, locked IAC, find the spark setting that
gives you maximum MAP reading (keep bringing the RPM
back to where you want, as spark moves it up). This is
your most efficient idle.

Now take about 5 degrees out and use that for the base,
and give that 5 to the adaptive spark, making sure that
the underspeed table is linear and monotonic. I have seen
some tables where underspeed spark goes up for a bit
(trying to help) but then at large underspeed goes back
to zero added. Putting a bistable profile into the loop
makes the whole thing unstable if you step into it.

[Rawr256]

That was the cause for my dipping when I would come to a stop. Finally got around to plugging a wideband into the car and discovered it was idling at 11.8 or so A/F even though a 14.7 was commanded. Got that all buttoned up and comes down to idle like stock.

Only thing I am still trying to figure out is when driving down the road the car does the surging/lugging/bucking thing at certain rpms and throttle position points. Going into the throttle a bit more clears it up but if I fall into the same rpm and speed it just goes right back to it.

Attached is my current tune that I am using with the RAF dialed in with Russ K's config. Will see if I can't get a cruising scan sometime later today that isn't an hour long with the air tables up.

[Frost]

That was the cause for my dipping when I would come to a stop. Finally got around to plugging a wideband into the car and discovered it was idling at 11.8 or so A/F even though a 14.7 was commanded. Got that all buttoned up and comes down to idle like stock.

Only thing I am still trying to figure out is when driving down the road the car does the surging/lugging/bucking thing at certain rpms and throttle position points. Going into the throttle a bit more clears it up but if I fall into the same rpm and speed it just goes right back to it.

Attached is my current tune that I am using with the RAF dialed in with Russ K's config. Will see if I can't get a cruising scan sometime later today that isn't an hour long with the air tables up.

That's some serious throttle cracker!

I pulled it down some. Try this.

[S2H]

holy fucking mountain range VE batman...

need to get that fixed asap...
dont know how the hell you got to that point... but you need to put in a stock ve table and start over

same thing goes for the MAF... it shouldnt be jagged... it should be a smooth line..

I also dont know how your car makes its way back down to idle with the spark tables you have...that alone could cause issues...

[Rawr256]

holy fucking mountain range VE batman...

need to get that fixed asap...
dont know how the hell you got to that point... but you need to put in a stock ve table and start over

same thing goes for the MAF... it shouldnt be jagged... it should be a smooth line..

I also dont know how your car makes its way back down to idle with the spark tables you have...that alone could cause issues...

lol, Probably should be smoothing it out a bit after logging. Have been calculating the error based off of the wideband and running pretty much just SD. Thought that running like that you shouldn't bother with the MAF since everything references the VE table? Maybe I read how it works incorrectly?

Frost - Will give that cracker table a try and see how it works.

After the last post I did also think back looking at my RAF table thinking it was lower than stock and it was. I imagine this has to do with doing the throttle set screw adjustment to get the IAC low enough? Will see if I can't get a good scan in today.

[vortec]

Work on your spark,VE and MAF tables.That alone will make a huge difference alone,possibly even make it idle better and settle like it should.