Ok when I first start up my car when its somewhat cool (doesn't have to be cold) the car runs fine under any condition, then after it warms up to about 70-80+ degrees, it starts to surge a lot, at first I though I was misfiring & was chasing wires/opti/plugs around for ages, now I have a new opti/ new plugs/ new wires & the LTCC, so my wires are about 3-4 inches long, my coils are on the valve covers & I know there is no burnt wires since I see them right there like an LS1, & have 1 coil per each cylinder.

Now, I ruled out misfiring because at WOT its awesome, no knock, no misfires, nothing, seems very strong.

Now, crusing on the HWY or just driving around town, the car will surge after it warms up, say I start off, I start going & right at 2000 or so it it just goes "bu bu" & keeps going, its like it has to just surge there for a bit & keep going, if I want to launch or apply 40%+ throttle it won't do it, just under moderate throttle, & on the highway around 2k it'll just keep going "bu bu, bu bu, bu bu" or if I'm crusing around 2200 rpm, & want to accelerate lightly it'll again go "bu bu" & go, its like it misses a beat.

So I came to the conclusion its cam surge, & major cam surge, now bear in mind I have 4.10 gears which helped a lot, with 3.42's, everytime it did that the car would shake aswell, but still, I would really like to get rid of it, in the morning the car runs soooo well, I've tried decresing timing as much as 7 degrees around that RPM/MAP range & it seems to get even worse.

Help, should I be adding timing to get rid of it? Cuz taking timing away seemed to of made the "bu bu" even worse & slower.

What could it be? too big of a cam for 02 readings? Should I go open loop? then the car would eat a lot of gas so screw that.


Also, I saw a tune out there that had that area in the RPM/MAP range with a lot of timing, like 55*, so I was thinking of implementing that table into my car, but his table from 1600-2400 & 40-80 map seems 15* above mine which is is like 45-55* in that area, that seems kinda dangerous, or does timing fix this?

ANYONE? I'm going crazy, help me!

 

You do not need that much timing. That's kind of ridiculous.
What rpm/map are we talking here? You're not lugging the hell out of this thing in 5th/6th gear are you?
Post some datamaster logs of when the car is doing it.
Also, make your bin file available so that we can check it out.
No reason to not be able to supply datamaster files either, the first 20 logs are free!

 

The amount of timing at 55* seems pretty high, my highest timing is only 43-44. You need to lower that, all your doing is having the knock retard taking the timing down to where it needs to be. Also, is your car still a 350, or did you do a stroker motor? I just got done tuning a buddies 383 that had some bad cam surge with a CC306. Between 1400 and 2200 RPM, I had to pull some of the timing to get it to run smooth, but at 1000-1200 I actually had to add some timing. Also, the reason why it runs fine while cold is because it is still in open loop, and not reading the O2s to adjust the air/fuel ratio. Just pull or add 1 degree at a time in the RPM range where you are getting the cam surge, then run a logging program to see what happens. It took about 10 times to get my buddies car running right, so don't expect to get it in the first or second try. Just curious, but who did your orginal programming? They seemed to have put way to much timing in if they have 55 in.

 

ok I'll try posting that stuff, but no that programming is what I wanted to try since I have bad surge, my programming doesn't have that much timing, but I tried pulling timing as much as 7* even 10* in some areas & it got worse, I still have the 350, it seems to be doing in anywhere from 45-80 map & 1600-2400rpm. I'll go on a highway cruise today & tell you guys what happens.

 

I have experienced the same in m car recently. i fixed this by adding timing in the 400-2400 RPMS talbes from 60KPA to 100 KPA
even at idle my timing is at 32 degrees.

 

yeah I've added some on the way to work & it seems a lot better, I'll work on it some more, I"m really hoping this is going the right direction now

 

There should never be any "cam" surge.. we don't have a variable cam timing or nothign...

It should feel soft down low and a easy seamless transition to more power.

You got tune surge

 

Ok...so what's tune surge?

 

MAybe with small cams like the cc306, but my cam specs are much more aggressive.

260/260 duration, 113 LSA, .610 lift

ITs not so easy to " tune out surge" with this beast.

 

dude we do have variable timing, called variable ignition timing what the heck is tune surge?

 

Bunker, check for exhaust leaks, especially at the Y-pipe flange, vacume leaks and fouled plugs. All these will give you similar symptoms. I know I have had all three.
Also if the surge seems to clear up after a new flash but then comes back later on then most likely its an exhaust leak.

 

Like alot of other people I've read all this before and am still tweaking here and there for driveability and performance. While working on cam surge one thing I noticed is that cam surge does not seem directly or at least only related to ignition timing. I've tried flattening out the smaller changes in MAP and rpm so fluctiations don't affect timing so much but with only partial success. I'm currently working on changing the blm ranges so that the cells are larger where the cam surg occurs. The PCM is going to try for 14.7:1 AFR so hopefully this will slow the PCM's reaction to variations in O2 readings. Adding gas and pulling gas would make the engine "surge" as well. That and I've never driven a car with regular distributor that surged, points, HEI, dual-points, mechanical advance only, vacuum advance, they never did it.