00Vette04GTO

Hey guys,

I am finally understanding and making progress on tuning my C5 A4 using HP tuners. All is going well. I have my timing(main/idle), idle air, and VE tables pretty much set where they should be. The car is running 100% better than it was, but I still have one issue. The A/C. It will sometimes kill the car in gear.

Now I have made major steps in improving this as well (which was achieved in the tables I mentioned earlier). My tuner had loaded very generic spark and VE tables and had WAAAY too much air. I used LS1.cfg to tune all these things in, but the A/C will still make the car stumble and occasionally die.

More info:
-LTFTs are off.
-Car used to not start with A/C on - which it now does with no problem.
-Idle is 850rpm and very steady. Can lower down to 650 and still have a pretty stable idle.
-6.0 with Trickflow 220 Fast as Cast heads, 10.8:1 compression and 281LR HR-113 Camshaft (comp part #: 54-459-11)
-Original tune I started with was for a different camshaft - but after getting into it I was very surprised that my other motor ran good with these tables. No peaks or valleys just even flat curve. Veery generic curve like he loaded a template to start with then never tuned it in.
-STFT now within -5 to +5. Was at -20 when I started.


Any pointers would be appreciated greatly. I am assume I need to make changes to my A/C modifiers under idle, but I am still learning this. Was hoping someone could point me in the correct direction.


Thanks,
Mike.

SladeX

Check the A/C Torque retard table under torque management. Zero it out.

00Vette04GTO

Ahhhhh ok....

You are talking about the torque management section, correct?
Are you referring to the AC TQ vs AC pressure or AC TQ vs IAT or both?

Also I noticed my AC bump TQ spark is set to enabled under Spark-Advance. Looking at some other people's tunes they have it off. Any recommendations?

SladeX

Latest version of HP tuners is now filtering out some auto data from me since I've got a m6 car. Check out some modded tunes for similar cars to yours for reference. The idea is GM retards spark with AC on which is detrimental to cammed cars.

Also play with the EOIT (Engine->Fuel->General->Injection timing) Normal and Makeup. Basically you want to increase it a bit (0.1 = 11 degrees delay). The idea is to time the spray of the injector when the exhaust is near or actually closed while the intake valve is opening. Default for 97-00 cars has the timing basically spraying on a closed valve, but most aftermarket cams open/close later thus necessitating delaying the "end of intake target" spray.

My reasoning is this, the AC turns on and puts more load which "slows" the engine cam timing events. When tuning, we sometimes bump up fuel/spark advance to get a smoother idle/part throttle to mask the fact that the overlap in our cam is pulling fuel straight out (your nose is a good indicator that our exhaust tends to run on the rich side after serious mods) Further slow down due to a/c load may be enough to "pull" almost all the fuel out through the exhaust causing a stall condition.

By fixing the timing events to match the new cam better, you end up not wasting fuel. Try increasing it by 0.1 across the board and you may notice that your trims get richer indicating lower oxygen due to a better more efficient burn. This will really only affect idle/part throttle conditions.

I've been doing a lot of reading on this on the hptuners forum, most modded values hover in the 6.2-6.55 range at max for most cams, but an xls spreadsheet is available there which if you have your cam card will let you know just how much you need to mod it by.

00Vette04GTO

Thanks for that information! Very useful. I was just reading on EOIT a few minutes a go and knew I would need to get into there. Now you have given me a starting point.

Much appreciated,
-Mike

00Vette04GTO

Mine are currently set at 5.55 - I notice that is way off the range you mention if 0.1 is 11 degrees.

I am looking at other tunes with similar setups now, but keep finding different years that use the actual degree (ex: 520) instead of the reference point.

Any recommendations?

00Vette04GTO

Increased by .1 and I can already tell you the idle is smoother. Seems I was still at stock values even though I've already had this tuned (two shops) with a (smaller) aftermarket cam. Smh.

I will keep tweaking with it. Though I am sure I need to sit down, figure out these values and what they mean, and do some math to set it right.

Thanks again...

Not sure if we solved the AC issue yet. Waiting for it to get to temp before doing some testing.

SladeX

97-00 had no overlap in cam, 01+ had overlap.

Quick of it is:

So if you are looking at a non overlap cam, you are basically adding more delay. If looking at 01+, it has overlap already so just need a small amount more delay to match up to aftermarket.

Billiumss

iTrader: (11)

In HP Tuners, go to this path: Engine - Torque Management - Engine.

Under AC Torque, go to MAX Retard, half the values in that table.

If your VE and MAF really are tuned within 1-2% then your Idle air table should be at least 10-15% more in gear and your Idle speed for the AC should be 25 rpms higher than the P/N.

Also you might have to "loosen up" your over and under spark tables, pull 1-2 degrees of timing out of those tables.

Done this on probably over 100 LS1 heads and cam cars and it always works well, even with big 240+ cams.

00Vette04GTO

Thanks Billiumss!

Got into EOIT yesterday (lots of time just reading one 20+ page posting on it) which improved a lot of idling and throttle response... But it moved my VE tables a little so I need to get out here soon and make a few more changes then I will go back to the AC. And I believe the info you have given me sounds very reasonable.

EOIT is definitely very interesting and I believe it's needed with overlap cams. Been working with the worksheets... Just reading all the information trying to find the optimal setting. But I do now understand what the 1-8 numbers represent (rotation and location of camshaft) and what the EOIT table is doing. I am surprised more tuners don't change these settings and more people don't know about them. I mean people adjust their pulsewidth and not the timing of injection?

I currently have the AC running for the most part with a minimal stalling. (mainly when going to 2000RPM fast in gear and letting off the pedal. - meaning a quick "blip" applied to the pedal)

I am still admittedly a newer user to HP tuners.... But understand cars, and am a computer programmer, so I seem to be picking this up pretty fast once it finally "clicked".

Thanks for the pointers, Billiumss. (and SladeX)

I will post results here soon. If I still have issues I can post some logs (and my tune) if you guys wouldn't mind giving any more advice.

00Vette04GTO

Also FYI: One thing that I think is causing me an issue is my IAT during the day is running insanely hot... This is probably due to my air intake (twin intake over the radiator is pulling enginebay air) and all the heat in my engine bay with this motor. I didn't start having these ac problems until it warmed up. The car ran (not perfect, but ran) off of the old tune (with a few slight tweaks like base running airflow after I did the cam) until recently.

So I know I need to make some mods to get the intake temp down.... Also probably need a riser hood to get heat out any maybe wrap my headers.

00Vette04GTO

It seems I have solved the AC issues with you guys help.... Thanks!

(I will know for sure after a much longer ride than 10 mins)

Billiumss

iTrader: (11)

You "might" need to bias your airflow more towards ECT then IAT.

00Vette04GTO

Thanks for all the info. You guys have helped me get a lot further down the road with my tune. The car is running pretty good right now with AC on and off.

As far as the ECT vs IAT bias.... Any negative effects of doing this?

Thanks,
Mike

00Vette04GTO

Ok... I tried moving the bias more towards the ECT...

And it is now to the heat of the day... When I get the majority of my issues. It is about 96 degrees outside

When car idles it especially with AC on, it gets up to 230 ECT

Didn't notice the temp on the IAT because I was tracking idle air and didnt have that bit on, but lets assume from past research over 190F

I notice that all my desired idle base airflow values (using scanner) are much higher in the 212 range than they normally are when starting from cold and then reaching 212. I assume this is because the intake air is hotter and it needs to pull more in.

Is the only solution to get my ICT down? (which I will do ASAP)... Or can I tune for this right now, somehow? And I will correct back when I get the IAT down.

As soon as I get rolling the IAT comes down some. It just gets real high when idling.

Thanks,
Mike.

SladeX

The only issue I've ever had with A/C on was on a hot start with ac/defroster on. It would take 2 tries to get it started. Mind you this was on my 5.3 heads, no EOIT adjustment and no cylinder bias added. My solution was what bill had suggested earlier along with a 950 no ac/1000rpm ac idle.


I've since moved to LS3 top end. As it stands, I have not relocated and still get hot IAT temps. The car doesn't stall at all (m6) nor does it struggle to get going from a hot start so I think for me the EOIT adjustment was the last little bit I needed to smooth everything out.