how do you tune larger cams? startup and idle

[gruff511]

The engine is a 420a 2.0L 4cyl. low compression with crower 64462-2 cams, running on MS3X. I just installed the cams and am going to try and start it soon.
Now before changing anything in my tune does anyone have experience with tuning for larger cams?

Im asking because i heard from some local guys that their cars wouldnt even start after dropping in larger cams.
I searched and all i could find for tuning cams was "larger cams require less fuel at idle and cruising" could anyone give me some advice on what you need to adjust after installing larger cams?

[gruff511]

So i tried starting the car and like i figured it wouldnt start. i had to take out a lot of fuel and open my idle valve up. So after having to change almost every table in my tune i got it to start and run. But it only seems to want to idle at 1100-1200rpm, any lower and idle will start to surge and stall out. I got hot restarts working decent but still has trouble on cold starts.
i ended up lowering my required fuel and still had to lower my values in all my other start/idle tables..does anyone have any advice on if im going in the right direction with this? Thank you!
i added my msq. and datalog im trying to load but its too large.

[nathaninwa]

Tuning new cams is just like tuning the stock cams. I went from jdm cams in my 2j to S1's. That was a huge jump but don't get ancie. See what the motor needs. It's not that the motor wants less fuel, it really needs more, the deal is large cams idle in a different kpa zone, say from 45 to 65kpa. And the old cams needed more fuel at that load and now it's rich.

I found rescaling the ve table, timing table and more importantly the afr table to restablish correct idle zone and cruise stuff

[kaeman]

try turning off idle air control and try to adjust the throttle blades to find the target idle rpm (set the blades and add or subtract fuel until you get smooth idle), when it has nice smooth idle use that rpm as your new target., then set up your idle control for that target idle rpm and turn idle air control back on. you should see a nice smooth idle like you had before but maybe just a few rpm higher or lower than you might have been at with the other cams. Good luck.

A friend of mine was fighting idle surges after changing to new cams and did this to see where his engine wanted to idle and then just made the adjustment to the target idle rpm... he said it took less time to do that it takes to write the little description of what to do....

[gruff511]

Thanks for the reply guys. Havent had much time to tune the car but i will be working on it this weekend. I adjusted my VE table values so i have a steady AirFuel mixture.
It seems like it likes to idle at around 1100rpm. But i still get the idle surge at times. I cant adjust my throttle set screw as my throttle body doesnt have one. The only thing that controls air at idle is my stepper motor. Now that brings me to my idle settings. I think my problem is in those settings because when the idle is surging up and down the stepper motor is constantly moving open to close.
ill be working on it today and get a log.

[gruff511]

So I can get a steady idle at around 1100-1200rpm now. The only problem is if i try and get it lower then it starts surging a little and hunts for the idle. Its seems to start doing it because the idle stepper motor starts opening and closing. Could my idle settings be the problem? Or is there something else that could cause the surging?
I

[Rick Finsta]

If you can't adjust a throttle stop then go into the test mode and adjust your IAC in test mode. Disable any idle control when tuning your initial idle; adjust fuel and spark to get best vacuum and only then worry about getting the IAC working. Ensure your steps are correct and that your homing settings are working. Make sure the valve moves as you'd expect.

Once you've got it working in steady-state, then go back and start tuning the closed loop stuff.

[gruff511]

The idle valve is working properly and it idles..but on startup and warmup the idle valve keeps closing and opening.im thinking the PID settings may be wrong at this point..when it fully warms up the idle steps stay around 60..only on warmup the fluctuate between open and close
if i have closed loop off it will idle at the given steps but as it warms up the rpm's increase too much

[gruff511]

Okay so i ended up adding an idle set screw/throttle stop to my throttle body and now it works how it should. It starts up and warms up and idles steady now.
It idles good at about 1100-1150rpms just cant seem to get it to idle lower then 1000rpm without it starting to fluctuate, but someone said the cams are probably meant to idle high so im not too worried about it.

[suberimakuri]

It may like a little more ignition advance at idle.
I've never used IAC's and let motors idle a little higher when warm. Clean lopey idle sounds great.

[gruff511]

It may like a little more ignition advance at idle.
I've never used IAC's and let motors idle a little higher when warm. Clean lopey idle sounds great.

ive tried changing the idle advance up and it just idles higher, i cant get it to idle below 1100-1200rpms because if i set my IAC steps lower then the closed loop idle control cant keep it steady, it starts surging because it starts opening and closing the stepper motor.

Also isnt the motor supposed to have a lower idle when warmed up? i thought it only has a higher idle when cold and during warmup?

ive been changing alot of things in the tune and now it seems to run okay for now, i included my msq. in case anyone would like to take a look at it.
Thanks for all the help everyone

[suberimakuri]

Good that you've made progress and are happy

I was meaning if IAC problematic then....
What about using combination of throttle stop screw and idle advance.
There's a target idle advance option..
Higher idle when cold is just an OEM thing to help get the heater going, etc.
I've never had a problem even when daily driving fill race car. Maybe not that cold here 0C?

[gruff511]

The only reason i dont mind it idling high is because even with stock cams the lowest idle rpm i was able to get that was strong and steady and wouldnt fluctuate was at 950-1000rpm even though my stock ecu would idle at 750rpm.

[Yves]

Idling large cams is always juggling fuel, timing and air vs the rpm at which you want it to idle.

[gruff511]

Theyre not an aggressive cam, just slightly larger then stock cams. But since it idles good between 1100-1200 ill just leave it at that.
Thanks for all the help everyone

[DeadStiff]

Posted in wrong topic.