I just got my new motor finished and need some help. Here are some of the big items.
TEA S2 5.3 truck heads
232/238 111lsa comp XER
all the bolt ons

I am trying to get the car to idle good and eliminate the surging or bucking at low RPM/MPH <2k. What do I need to do with LS1edit?
Phillip

 

Phillip - Hey! Have you scanned it ? What's it idling at ? How does it behave first couple of minutes after cold startup (open loop) versus warm - closed loop? Have you made any changes to the stock PCM? Congrats on the new motor-VERY :cool: :D
joel (Bink)
:cheers: :steering:

 

At first the car didnt want to stay running without patting the gas. Now it will start right up and stay running, the idle hunts some and it has a slight cruise control effect. Any hints?
Phillip

 

Phil, look at my post down the page a little. A lot of good hints. We have found that messing around with the IACPark has a big effect on improving the cruise control effect. Also, get the idle set down to 900 or so. You may have the base idle too high. I am stiil playing around with the tuning but I am getting closer.
http://forums.corvetteforum.com/zerothread?id=571549

 

Lets start simple....what do you do to make a big cam idle? Just idle not surging.
Phillip

 

I had wild shaking, stalling after a high rpm run and then stopping at a light, stalling while idling, hunting after a rev, and delayed decay. Now at 150 miles since the cam went in I'm pissed that the idle is so smooth that it feels almost stock. My vote....simple= higher idle than you think is nec....1100 at first. Let it learn for 100 miles and lower to desired shake. No other adjustments are nec....I went through this twice. You need to choose the idle speed and don't change it. With a hole drilled in the TB you must drive the car to allow the computer to form tables for different situations. If you disconnect the battery before the tables form you loose some of the learned info. After it stabilizes you will notice the cruise cont effect diminish on its own since the car is delaying it due to the low portion of the hunting in which the low rpms cause the vacuum to be too low so the computer compensates for it by adding delay to the idle decay to preserve ability to brake...ect. This wont be an issue if you start really high with the idle. You can do 20 other adjustments as guys will suggest and they will all work because the computer will learn to idle with any set of adjustments....or you can just do the one....too high an idle--- that provides all the vacuum and air the cam requires to avoid changing the engine speed which is the cause of every one of the symptoms.
Hope it works out...let us know


[Modified by SpinMonster, 10:56 AM 6/6/2003]


[Modified by SpinMonster, 11:02 AM 6/6/2003]

 

One observation- if you put the stock cam in and set the idle to 400-450 it will have all of the same syptoms of a big cam at a higher idle ....the power band is simply lower and the stock cam's lope characteristics are noticed lower.

 

Spin, what is your idle set at now. Mine is at 925 or so and seems about right. Anything over 1000 is just to high for me, I will wear out my brakes in no time at the stop lights! :D

 

here is a weird thing I just noticed. When I am cruising at 1400-1500 some times the car feels like it has a light miss. The car wants to surge very fast but just enough to notice. It feels like the car is missing and after driving for 20 seconds the CE light pops up P0101 MAF system performance. You speed up, the car smooths out and the light turns off. Can someone clarify the tables and what they effect?

Idle Air
IAC PARK
IAC Gear
Ect...


[Modified by Phil97SVT, 9:37 AM 6/6/2003]

 

I was at 1000 and pulled it back to 950 when it learned the changes.....114 ls is learned fastest, I have a 112 lsa. I never even thought of it causing problems for guys with automatics, is imagine thats what you have.


[Modified by SpinMonster, 6:32 PM 6/6/2003]

 

auto tap probably will show a very rich condition at those rpm's (I suspect your power band is even higher than this rpm) The car is surging the idle to pull in more air. Adjust the MAF table to the opposit condition to get the LTFT's in line at those rpm's so it stops gasping for more air.

idle air:guys set thses to 160% over defaults to smooth out the idle as a band aid but it prolonged the cruise control effect for me. I eventually reduced them back to stock as the car learned the changes.
IAC Tables: The motor in the TB will default to the setting you put here until the car reaches temp (in park and in gear) the one in gear allows for the air to be higher so it garrantees more air to operate things like the brakes until the car warms up....hence it causes the idle to hang even higher at first (cruise control effect).

IAC Follower: hangs the idle up after warm up for the same function

I know it seems like my above answer was 'beginnerish' but if you raise the idle in all tables, the IAC tables wont be starting off with the wrong value and prolonging the ability for the car to learn the proper settings. The raised idle in gear I suggested will negate the need for any adjustment in IAC gear since the car will have the vacuum it needs that you lost by moving your power band up so far as you did with this choice of cam. For an experiment with someone's stock car, lower the idle to 400 where you see it lope. You will see that the computer adds idle on deceleration to creat more air intake for the overly rich condition and alters this IAC function creating the cruise control effect. The conditions you experience happen with all cams but at different rpms due to the power band.....u cant use a near stock idle for a cam with a 2000+ to 6800+ power band for this reason.


[Modified by SpinMonster, 7:09 PM 6/6/2003]

 

Thanks for all the info guys. I have learned more from this and the few other posts in this forum than I have since I started tuning driveability on this cam.

 

I autotapped the car and sure enough the LTFT were +10 - 15 on both sides while cruising. Should I lean out the MAF tables?
Phillip

 

what rpm? the ltft's is what the car thinks you are running not that you are lean or rich. Raise the idle first, then see if the range lessens if the swing is down low. A high rpm idle with the throttle position at zero will probably lessen that wide range of the ltft's. Also what are the HO2's at the rpm you are taking the getting the + and - ltft's. If down low you are - and at 2000 you are positive you simply need more air in at idle. Your ideal would then be to multiply the entire MAF table by a percentage to get all the ltft's to be just under 0 ( all negative )

 

Update: The new motor has roughly 150 miles on it. I reduced the IAC tables by .10(orginally increased .45) and the Idle air by 1.00(orginally ncreased by 5.50 gear and park). The idle seemed to catch quicker and stick at 875.
Phillip

 

carputing (ls1-edit designers) recommend raising IAC tables as a last resort....the opposite worked for you.

You have a very low idle for a cam of that size.(or any over 224/224)

 

I drove around alittle last night after I finished on the internet and seemed to drive well. My LTFT are alittle high but I am still working on those. Here is a run down of where I am at....

Timing: 27 Low 29 High Base +2
A/F: 12.75:1 per last dyno which I know is off
Compression: ~11.6:1 <== thinking about getting the heads milled again :)
Idle: starts @ 1050 and goes to 875
IAC: +.35
Idle Air: +4.5
Cam: 232/238 111lsa

 

for the timing did you go + 2 across the board or 2%? A recommendation to maximize the timing at all rpms...
1-get all ltft's to be neg.(by mult the entire MAF table by a percentage: if you have =8's on ftft's then mult the entire table by .92%
2-do power enrichment till you get all HO2's to be about .89-.91...below .89 is lean
3-advance the entire base timing curve and WOT curve by 5% (multiply table by 105%) then check for KR....if there is KR then pull it back at the rpm and load where it was pulling timing and then add 5% more timing to both curves. Eventually you will be at the max for all rpm's and loads. After you do this a few times start to advance by only 2%. After 5-6 times with this proceedure you will have a totally custom timing curve.

You will also notice this smooths out you idle too and your revs will be more effortless.


[Modified by SpinMonster, 9:56 PM 6/7/2003]


[Modified by SpinMonster, 9:58 PM 6/7/2003]

 

by the way about the ltft's.....don't count the ltft's that result reaaly lean on deceleration.....only go by the acceleration numbers. The computer leans out the mixture big time on deceleration. Look at the engine rpms to verify that you were accelerating during the numbers you go by. If you see +10 ltft's then multiply the Maf table by .90

 

Why would you change fuel amount with the MAF instead of IFR :confused: