Ronny

iTrader: (1)

just added MAP to my inputs. have about 1.5 years with this LM1. first year was A/F only. i could log A/F vs TPS vs RPM and saw the correlation in logs. now first day with MAP and i see in log:
rpm steady 880 rpms
tps steady .63 V
A/F steady 16.8 to 16

this is idle with heat soaked engine(large cam 224/230 @ .05); TBI; GM 7747.

now what is wierd is the MAP for no apparent reason rises from .8V to 3.37V then settles back down to .75 V? 4 secs later does same? now i just realized the RPMs dropped in a pulsating idle 880-500. so i will assume the IAC opens(stal saver) and that raises the MAP considerably. 4 secs later repeats. and again. my idle is generally smooth at 850 rpms yet at times acts wierd. OPEN LOOP. CL is disabled. at first i assumed the MAP is acting up but now i see the LM1 is repoerrting accurately the event.

any comment is appreciated.

Dominic Sorresso

Ron,

How long have the heads been on and what gasket did you use?
If you hold the throttle open a bit with no load, will motor hold a steady raised idle? Does the WB report a swing between lean and rich mixture?

Ronny

iTrader: (1)

edelbrock rpm 64 cc non emmishions. gasket was a recomendation by edelbrock in install directions, a felpro.

manual trans if i hold open and alow it to return to throttle stop it will come down. idle commanded(700) below actual idle speed (900) since stop screw holds 850. tps is like .61V and IAC is 0 steps per log. if in OL idle stable if CL not so. seems the chase tail senario. rpms fluctuate, iac opens closes, stall invokes and recovers, A/F varies. round and round. i will suggest cam is fooling the NB(CL) as the WB shows A/F changing as well it too reading the overlap as lean. exhaust is clean to eye but i suspect
rich.

now OL is sooo much better. idle much better. no tail chase. occasionall will hang high but will come down eventually. if i blip throttle ever so slightly(not to scare party in car next to me(hooker aerochambers) it comes down immediately. it still pulses a bit but toerable. i think the pulse is unrelated to iac as no move but the cells are moving with diff fueling values. timing is 21A in all idle cells 400-1200 20map to 40 map. so timing not affecting it. as i stated OL is tuned to 124 BLM or so.

also running rick to help AE. a crutch. on tip in.

i still need more TPS AE. i backed off a lot early this summer and that allowed me to sneak up on AE 61 usec at a time. i also loaded up 0-3-6-9 same as 12. then 15 increases 61 and so forth.

yes i han hold raised idle. no problem.

Dominic Sorresso

Ron,

THe reason I bring it up is because it sounded like the symptoms I was experiencing oveer the last year. I installed my TFS heads with their recommended Felpro gasket which was a 1010. As RBob and some of the others on this forum and the Corvette Forum have found out, the 1010 had a defect. The fire ring would de-couple from the gasket material. I was forced to run O/L in order for it to idle. But when I blipped the gas, the idle would jump, then drop and almost stall, then it would catch again and seem to cycle like a "lean surge". Once I R&Rd the head gasket, I could use C/L idle. Now it idles at 850 and AFR ranges between 13.4 to 14.2 at idle. I'm assuming part of that is the cam because of the 108d LSA. Without trying to jump to conclusions, I would do a compression check if that was the gasket you used.

http://forums.corvetteforum.com/show....php?t=1154764

Ronny

iTrader: (1)

thanks for the tip. do you recall the pressures in each cylinder?.

Dominic Sorresso

Ron,

The last time I did a static pressure test on my motor, they were all in the 200psi range. This was several years ago when I determined I could probably use a bit more overlap in the cam.
My previous cam has 43d overlap at .006, my new cam has 53d.
If you've read the post I linked to, they suggested a "leak down" test, not a compression check as I did. I also had a suspicion of a blown head gasket when I was trying to "burp" the cooling system and the coolant would surge out of the radiator. It had never done that before. Finally, I uncapped the oil filler and the cap had a light milky looking substance on it. But the bottom end was clean as a whistle. Its been several months now since I R&Rd the gaskets and Oil Pressure is fine. Oil is clean. And I ran a 13.3 last weekend with about 7-8 runs at the track.

Ronny

iTrader: (1)

did not read the link. will do leak down in spring. oil is clean. changed 06/05 and had cam in 10/2004. explain the function of head gasket, can it retain the coolant yet allow only a compression loss? also my coolant level is consistent. had i kept 210/216 .05 it would habve been a breeze to tune. now i need to fuel it beyond 5000(5800) and work on idle and deal with overlap. all in all i drive every day not raining 50 miles a day. car never ran better. seems remarkably better with holley projection vs xram when tenmps 40F in morn.

Dominic Sorresso

Ron,

First of all, I want to reiterate that this may not be your problem at all. I went through a year of "tuning" trying to get the lean surge out playing with just about every param in the bin. I guess the "silver lining" is that I got educated on PID controls, O2 settings etc. As you can see in the pics I have posted, it was possible for the motor to pressurize the coolant without any outward signs of a coolant leak. When I pulled the head off, the #7 cylinder clearly showed signs of having been "washed" and the plug was white.
BTW, what Fuel Pressure are you using?

Ronny

iTrader: (1)

understood. was planning to do leakdown anyway as will dyno in a week (new cam and intake10/04) and if result is not pretty will do leakdown to determine engine condition. car has 103K on original short block. prior dyno was 222 HP(5000rpms) and 267 TQ on old cam 210/216 .05 with xram.

Ronny

iTrader: (1)

forgot 17.5 lbs. not enough nFP. i could not inc with CL as idle was funky. OL i think i can and will. every other week car in shop(paint-would not start-lead to dist fell off-wb02 i fried) so have done insufficient tuning. need to locate a spot to do WOT. 100+ mph is dangerous on XWAY. meant to get to UNion Grove but never did. weekends we head to northwoods.

Dominic Sorresso

Interestingly enough, this started when I bumped up the FP. I started with 16psi. I am now at 20psi using 80# injectors. This puts my WOT DC% at something like 85%. I may still look to upgrade to 90#. Based on what I saw from plug cuts after racing at Byron, I think I could actually "lean" out the WOT fuel a tad more. My WOT tuning consists of WB O2 + merging from an on ramp in 3rd at about 2000rpm and then punching it till about 5600rpm. I am also going to suggest you get the UTBI code and Embedded Lockers from RBob. I have been using his extended VE tables. Does wonders for controlling the idle and tuning WOT. You really can't tune a semi-hot cam well with the resolution found in the normal 7747 code.

Ronny

iTrader: (1)

Quote: suggest you get the UTBI code and Embedded Lockers from RBob.

not yet available right?

duty cycle % i cannot find in myTunerPro RT 4.0? how is it labled? i fiqured it would show in sensor data. where do i look?

i ran TPRT about 5 times now. still need to learn how to use it. it does connect OK.

Dominic Sorresso

Ron,

To get the Duty Cycle % you first mod the ALDL datastream to output the SynchPW. Then its a calculation
to get the DC%. If you want I can help you with the ALDL stream and the calc.

Ronny

iTrader: (1)

i was of opinion tunerpro RT 4.0 has that function built in program? yes i surely will need help. thank you!

Dominic Sorresso

Not that I know of. I use TP 4.0. Basically you assign the address for one of the ALDL outputs to output SynchPW instead. I have mine output under the PROM ID. Jprevost is the one that provided the modded ALDL stream bin for the 8746 and 7747 sometime ago. Here check this out. It should help quite a bit.
https://www.thirdgen.org/techbb2/sho...light=7747+RAM