High MAP after heads and cam at IDLE

[maudyZ28]

hi guys, just been an observer for a while. Appologies if it has been asked before but I have a few quick questions.

Just fitted 253 LS2 heads (stock) and TSP 228R cam to my A4 camaro. (has ls6 intake, LT headers and true duals - so all supporting mods).

Anyway the questions are:

1: My map at Idle is about 55-60 Kpa is this normal on a H/C setup? Before It was about 35-40 Kpa at Idle
2: The car wouldn't start and Desired airflow was set at 6 g/s on a stock tune (starting from scratch again) so I added about 3 g/s as a guess and comparing with Idle guide desired airflows, so the car runs but Idle not perfect. and also tends to push a little while driving, ie little engine braking untill above ~1700 rpm I assume I am best doing full VE and MAF tunes then working on Idle when all airflows and fueling tables are correct
3: The stock timing is 28-29 deg at WOT 5500 rpm+. Is this much too high for the higher compression the LS2 heads provide over stock LS1 853 heads?. I know weatherman Shawn said the Z06 high octane spark table is a good start, can I just merge the high rpm bit? (ie lower my stock timing table by ~5 degress as the low rpm spark in the stock table seems ok in initial logs as there is no knock)

Sorry for all questions but figure one thread is better than 3 ?? thanks all

[macca33]

1. It will read higher, as you have less manifold vacuum now, with the larger camshaft bleeding off cylinder pressure, due to it being less efficient than the oem camshaft at low rpm.

2. Getting the idle correct first - using Auto VE for idle cells and RAFIG would work - it is a chicken before the egg type of thing, depends what you wish to do.

3. I reckon 28-29 deg at WOT will be too much for your increased static compression, maybe lower them by 4-5 degrees as you've suggested and see how it goes, through a bit of experimentation.

E & OE.

cheers

[redhardsupra]

1. MAP at idle will be higher, 228 cams tend to 'clean up' nicely after you start to raise idle rpm to 900rpm or above. 55-60kpa doesn't sound wrong, depends on many variables, idle rpm, how warm the car is, spark settings, etc... i've done some 228-duration cams that ended up in 45-48kpa range, but that took a lot of work (mostly convincing the owner that 650rpm idle might sound cool but isn't healthy)
2. how the desired airflow table works is a bit of a mystery still. bigger cams tend to need higher values in that table. I'm guessing values in this table get converted to how much should IAC open (or TB in electronic throttle cars). the thing to realize here it's a pure lookup, no measurements are taken. thus don't expect the ecu to correct anything if you change out the hardware. the lookup table isn't aware that you went from 60% VE, 35kPa MAP, 600rpm, to 30% VE, 60kPa, 900rpm idle, which changes the airflow drastically (do the math, you'll see). so unless you change the calibration, it's still going to be using the values correct for the stock cam, which is just plain wrong, sometimes by a large amount.
3. what is the correct spark at idle is another mystery. what's even worse, old computers (LS1b), have a very different strategy for idle spark from the newer computers (E40 and newer). so on old ecu's, higher spark tends to do the trick, while with the newer ones lower one works better. why? i wish i knew.

my approach is to use live controls to command one particular spark (no modifiers in effect), and change the value of spark (small increments, let it run for a moment to stabilize) while watching the MAP value (you want the lowest), while listening for smoothness (not something that's easily quantifiable, but you'll know what i mean the moment you change the spark value to something that the car really doesn't like), and while smelling the fumes. i'm not kidding about the fumes, if you do it enough times, you can differentiate between different conditions based on how the fumes affect you (itchy eyes, burning sensation in your nose, headache...). remember to do it under steady conditions; cold car is no good because this method takes some time, so as you are trying different spark settings car warms up, atomization of fuel changes, amount of fuel dumped in changes, and now you're dealing with a lot more variables than you'd want to make a proper attribution of 'spark of X generates MAP of Y'. fans kicking in when it's too hot is another frequent problem. you usually get few mins before you have to let it cool off a bit, and try again. this is not a fast process, but it yields very nice idle. the problem is that if you change any settings afterwards (idle rpm is the frequent object of tweaking when playing with idle) you gotta go back and do the whole process again. So i try to do a 'rough' tune first, see if let's say 900rpm is enough that after some quick playing with spark you can get it to a nice spot. if not, you adjust idle rpm and find spark again. once you find a decent setting, stick to it, and just do the spark in more detail.

[maudyZ28]

thanks for the reply guys.

So got a idle, don't know if it is decent but it works - set at 800 rpm, base spark table ~21 deg in N/P MAP ~ 55Kpa (spark keeps altering though due to modifiers?) What modifiers do i need to Zero out, the spark correction tables to find my own spark in bidi mode?
It also runs ok at this idle in OLSD and I dialed VE in here, BUT have no idle setting for car in gear as it keeps stalling out (its an A4) Oh Idle is at 750 rpm in Gear, and yes I only have a stock stall at present.

With MAF plugges in normal CL running it doesn't stall when I put it into gear after 3 or 4 attempts when it does stall.
In OLSD after dialing in VE out of gear idle and while driving it is more accurate with the WB but i still cannot come to a stop or go from N -> D without car cutting out I believe there is some table for extra spark when changing to D, but is there one for adding air when it comes under the initial load? Is this what I need if using SD?

[maudyZ28]

ok, so wonder if anyone can chime in on this?

Calibrated my VE and my MAF so via auto VE and auto MAF, so fuel commanded matches my WB as it should. Only problems are with idle. The car always stalls when I change into gear when I've got the P/N idle setup correct.
I wanted to dial in Desired air flow, so at idle in P/N I in auto MAF I calculate the BEN factor here, but everytime I start and retune the car seems rich again and keep producing a BEN of ~0.9?. I managed to get car in gear by using a little gas so she didn't stall, did the full Auto MAF (which after another drive is spot on) and Idle in gear is smooth as silk with 28-29 deg of timing an fueling at bang on 14.7. However when I return to P/N the car hunts between 500-1100 rpm ( idle set at 900) and I can see spark fluctuate then it stalls out. Is this because desired airflow in gear is too high (it is large number than MAF reads currently?) and the ECU learns to trim down, and when I go back to P/N which is dialed in does it pull the same amount back out?

Does this sound right.
1. Try dial in MAF at idle P/N again with auto MAF and then re check and put air flow at idle as desired airflow
2. Still auto MAF, check the desired airflow with car in Gear as check it is in a different MAF freq cell. How can I stop car stalling if it does so when this is ok? Are there any airflow adders
3. Do 1 and 2 again but this time using VE table.

thanks all for the help on this

[Taz]

A consistent idle under all conditions can be a difficult process. Follow the steps in the thread(s) linked below ...

http://forum.efilive.com/showthread....ips-amp-Tricks

This idle thread is by WeathermanShawn, and also links to an idle thread by SSpdDmon.


Regards,
Taz

[redhardsupra]

maudy, spark is NOT the dominant factor in P->D transitions, Desired Idle Airflow is. What are the values there? Have you ever scanned Short and Long Idle Trims?

As for the 'tutorial' that Taz linked to... let's just say approach with caution, or at least a grain of salt

[ls327]

i have a similar setup as yours > 10:5CR with ls2 heads on a 224R , my map KPA is around the same as yours.. running 27* at WOT on E85 and no problems at all with KR...

[The Alchemist]

welcome to cam tuning its lots of fun you'll find most if not all the answers right here on this forum

[Sid447]

........However when I return to P/N the car hunts between 500-1100 rpm ( idle set at 900) and I can see spark fluctuate then it stalls out.

Sounds like you need more air....(desired airflow) ....You'll be surprised how much you'll need.


As a suggestion you could have a look at the stock 2003 HSV GTS-A4 tune file in tunefiledepot.com and look at the parameters there for reference as this used modified heads and a cam from the factory.