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dthompson
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Posts: 20
Joined: Tue Jan 21, 2014 9:02 pm

Dashpot issue: rpm dip prior to hanging idle

Post by dthompson » Sat Aug 23, 2014 5:48 pm

edited title and tried to provide a better description.

I am having a problem with an occasional stall. I am trying to fix the problem, so I went through idle 101 and the decipha's dashpot webpages and set mine up as described. its not bad... but now the idle hangs for a while and prior to it hanging, the rpms dip lower than desrpm (the rpms seem to fall to far, catches and elevates back up to a hanging idle, then as dashpot expires, it drops back down to desrpm). I think the dip prior to the idle hanging is a problem, which will cause the car to stall occasionally. I would like to decrease the hang time, but as I do, the dip in the rpm gets worse before it catches.

notice in the log that the rpms dip below desrpm even though the dashpot has not expired. they come back up and the idle hangs. I would like to reduce the preposition some or the decay rate so it doesn't hang so long, but when I do the rpms dip worse. I believe the problem may be related to an over rich condition that follows the lean spike after the throttle blade closes. Its like the ecu commands it really rich to compensate for the lean spike when the throttle closes, then it takes a while to correct again for the rich swing. It seems like because it is rich, the idle dips down even though the dashpot has not expired (which should be keeping the rpms up). Not sure if this can be remedied or not, or if the dashpot has to be tuned better to compensate for it?

Thanks,
Derek
Attachments
045 DD TUNE 80s start of Lasota 2014_Aug_23_17-18-40.csv
(709.91 KiB) Downloaded 691 times
89 Thunderbird SC
427 SBF Twin PTE 6266s, T56 Magnum XL
9.5:1, AFR 205cc, 222/227cam, TFS R intake, FID 1600cc, 93 Pump Gas
EEC=L1C (92 5.0 Tbird), BE/QH, GSALC

dthompson
Gear Head
Posts: 20
Joined: Tue Jan 21, 2014 9:02 pm

Re: Dashpot issue: rpm dip prior to hanging idle

Post by dthompson » Fri Sep 05, 2014 7:30 pm

2 weeks and 40+ views, Nobody has any suggestions?
89 Thunderbird SC
427 SBF Twin PTE 6266s, T56 Magnum XL
9.5:1, AFR 205cc, 222/227cam, TFS R intake, FID 1600cc, 93 Pump Gas
EEC=L1C (92 5.0 Tbird), BE/QH, GSALC

rebelranger
Regular
Posts: 72
Joined: Tue Aug 19, 2014 3:34 pm

Re: Dashpot issue: rpm dip prior to hanging idle

Post by rebelranger » Sun Sep 07, 2014 9:40 am

Are you using open or closed loop?
1993 Ford Lightning 351w (5.8l), factory heads, cam, block, pistons, Kenne Bell 2.1L, Siemens 60lb injectors, 8#boost pulley, Walbro 255lph inline via 2psi hobbs with factory 155lph intanks, AEM wideband, AutoMeter Fuel, volt, transmission, boost/vacuum gauges, E4OD tranny, Crane Ignition.

ICY1 ECM, LHBL0 def, tuning via Quarterhorse and BE12 using Sailorbob strategy.

decipha

Re: Dashpot issue: rpm dip prior to hanging idle

Post by decipha » Sun Sep 07, 2014 10:28 am

it sounds like you need to decrease the decay up top and increase the decay down low

dthompson
Gear Head
Posts: 20
Joined: Tue Jan 21, 2014 9:02 pm

Re: Dashpot issue: rpm dip prior to hanging idle

Post by dthompson » Tue Sep 16, 2014 8:00 pm

I have worked over the dashpot functions pretty hard. I went through all the write ups and I keep seeing this patter as shown in the image. after declutch dashpot decrements and hegos still switch like normal. part way through decrementing to the dashpot min clip it goes rich, like 12.0. This seems like some weird fueling issue to me that I don't understand. Can anyone help?
DECLUTCH STALL2.jpg
DECLUTCH STALL2.jpg (97.58 KiB) Viewed 18038 times
89 Thunderbird SC
427 SBF Twin PTE 6266s, T56 Magnum XL
9.5:1, AFR 205cc, 222/227cam, TFS R intake, FID 1600cc, 93 Pump Gas
EEC=L1C (92 5.0 Tbird), BE/QH, GSALC

decipha

Re: Dashpot issue: rpm dip prior to hanging idle

Post by decipha » Tue Sep 16, 2014 10:43 pm

i see you have a supercoupe in your sig

is this the supercoupe? are you using my sc base tune?


if transient fuel is too far off it will do exactly what your experiencing

if it decels rich then remove some decel fuel, you can reduce the decel transient multiplier scalar probably 0 it out

if its still that rich on decel then you probably need to dial in the bottom portion of the maf, if your fuel is dialed in then you either need to reduce the lower portions of the maf curve below idle mafv and/or reduce the injector offset, or increase the breakpoint and/or low slope

dthompson
Gear Head
Posts: 20
Joined: Tue Jan 21, 2014 9:02 pm

Re: Dashpot issue: rpm dip prior to hanging idle

Post by dthompson » Sun Sep 21, 2014 7:25 am

Yes this is about the supercoupe in my sig. I started out getting it tuned a dyno shop with an SCT chip, but they did not do a good job. I ended switching to QH and BE and I got my base tune from Dalke.

Whats interesting about the first image I posted that you don't see is that load is going up when it gets rich. I guess the same airflow with lower rpms causes the load to increase, with that being the case, the PW on the injectors increases (directly related to load) and makes the rich even richer.

I checked and the transient decal fuel multiplier is set to zero. My fuel is dialed in pretty well down to the idle point, below that may need some work. (It seems to be pretty close once everything is good and warm. I do notice on cooler morning the car tends to pull more fuel even once it gets warm (like in the 5-10% range), but later on my way home from work when its a good bit warmer it straightens back out to (0-5%). I realize that's the point of the KAMs is to correct for all kinds of variations.) here is my maf curve.

16.00 69.4670
5.00 69.4670
4.75 61.4672
4.50 54.7569
4.25 46.7452
4.00 41.8020
3.80 36.8111
3.60 31.7366
3.40 28.1904
3.20 24.3935
3.00 20.8353
2.80 17.6354
2.60 14.6743
2.40 12.0236
2.20 9.7908
2.00 7.9759
1.80 6.1969
1.60 4.7402
1.40 3.6417
1.20 2.7820
1.00 2.1611
0.90 2.0059
0.80 1.5403
0.60 1.2895
0.53 1.1582
0.30 1.0030
0.00 0.0000
0.00 0.0000
0.00 0.0000
0.00 0.0000

The injectors are Siemens 80lbs and I got their info from Dalke. I did an internet search and came up with the same information on those injectors that he provided. Im pretty confident that they are set up correctly.

It idles at around the .5 to .6 depending on the day. .53 is a point I added to help dial things in, it typically idles there when the fan is off. Below the curve needs some work, I will try and use the thing in BE to try and come up with good numbers down there.

I did notice something weird about fuel recently. It seems like on declutch, the kamrf's get far apart in their correction. kamrf2 drops down to 0.82ish on declutch and kamrf1 only goes to 0.93. I only really notice this in situations like a declutch or when the throttle blade is closed. when the car has a load on it, they generally match less than 5%. im trying to rationalize this observation and the only conclusion that i can come to is that there is an exhaust leak or a bank 1 vacuum leak somewhere. not being an expert, i would lean towards exhaust leak because under load the kamrfs match well. I dont know, maybe it doesnt even mater :/ My wideband is on bank 1 and so the maf is really tuned to using bank one. I uploaded a log of this observation.
Attachments
kamrf differ on declutch.zip
(101.5 KiB) Downloaded 658 times
89 Thunderbird SC
427 SBF Twin PTE 6266s, T56 Magnum XL
9.5:1, AFR 205cc, 222/227cam, TFS R intake, FID 1600cc, 93 Pump Gas
EEC=L1C (92 5.0 Tbird), BE/QH, GSALC

decipha

Re: Dashpot issue: rpm dip prior to hanging idle

Post by decipha » Sun Sep 21, 2014 10:24 am

its more likely a vac leak

every single supercoupe ive ever touched ive always found vac leaks, that includes all 9 of mine, every single one had at least a small vac leak when i got them

your idle airmass is HUGE, what kind of cam do you have in it?

a stock supercoupe should only suck down 16 kg/hr at idle or .58 lbs

dthompson
Gear Head
Posts: 20
Joined: Tue Jan 21, 2014 9:02 pm

Re: Dashpot issue: rpm dip prior to hanging idle

Post by dthompson » Sun Sep 21, 2014 1:03 pm

Its a cam from SuperSix Motorsports. Duration 218/224 Lift .545/.545 Rockers 1.7 LSA 112 I also have their stage 3 heads.

If there is a vacuum leak, I cannot find it. Ive tried blowing smoke through it, propane, carb cleaner. I have a front mount IC on it so I got rid of those problematic factory tubes. it draws about 13-14 inches of vac at idle if im not mistaken. here a copy and paste of my build sheet....

Original miles were 135,000
Motor rebuilt by H&F Performance, Wilson, NC.
Stock Manual Transmission and Rear End
Computer Code: A9U2

Modifications:
Long Rod 4.3 Stroker: New 4.2 crank, SCAT forged stroker Hbeam rods, ARP rod bolts, 9:1 compression Wiseco forged pistons, rings, pins, and lox: (Super Six Motorsports)

88-95 Stage 3 SuperHeads: Stage 2+ plus additional intake porting, high polished chambers, 1.88/1.57 stainless steel valves, .54 lift CompCams springs/retainers: 228 CFM intake/189 CFM exhaust. .83 exhaust/intake flow ratio: (Super Six Motorsports)

SUPER SIX MOTORSPORTS billet hydraulic roller cams: Duration 218/224 Lift .545/.545 Rockers 1.7 LSA 112: (Super Six Motorsports) Made by Comp Cams. Part # 44-000-9, Serial # Z 9032-12 Grind # FV638 3611 /3612 HR112.0 See attached image at bottom of document.

Stud Mount Adjustable Roller Rocker Arm Kit: Custom CompCams 1.7 ratio rocker arms, studs, locknuts, guide plates, and shims. with hardened pushrods: (Super Six Motorsports)

New Lifters, Pushrods, Bearings, Timing Set, Timing Tensioner, Oil Pump, Water Pump, 180 Degree Thermostat, Oil Pressure Unit, Coolant Temp Unit, Pilot Bearing, and Head Bolt Kit. Rotating Assembly was balanced, Bore and Honed Block, Decked Block, Pin Fit Connecting Rods, Port Matched intake manifold, and Surfaced Flywheel.

Centerforce Dual Friction Clutch and new clutch release bearing

MPX90 Supercharger upgrade and matching plenum with coated rotors. This is essentially a better version of the Eaton M90 blower found on Super Coupes. Improvements are made by increasing the size of the intake plenum and a better exit port. The snout and rotors come from a M90 and have the abradive coating applied to create a better seal. (Magnum Powers) This setup is currently making 15 psi

85mm Throttle Body: Magnum Powers

Raised classic supercharger top: Magnum Powers

3.5 inch CAI…filter is still located in the engine bay, but there is a divider/heat shield: Magnum Powers

10 Rib 15% Supercharger and Jackshaft Pulley Kit with Heavy Duty Tensioner Springs and Belt: Magnum Powers

Pro M Racing M80 MAF calibrated for 60lb injectors.

80# Siemens Deka Injectors

NGK TR6 Spark Plugs gapped at 0.030

255lph Walbro High Pressure Fuel Pump GSS340 with new hanger assembly

Kooks Mid Length Headers 1 3/4" Primaries to a 2.5" Collector. Made from mandrel bent 304 STAINLESS steel material with thick flange and a ball/socket type down tube connection and new O2 sensors(Super Coupe Performance)

Custom Exhaust: New Magnaflow Cats 2.5” dual from headers to Magnaflow Resonator. 3 inch single out of resonator around gas tank and splits back out into 2.5” dual with two Cherry Bomb Vortex mufflers. All mandrel bent.

Stock Transmission: M5R2 5 speed manual transmission and stock limited slip differential with 2.73 gears. Trans gear ratios: 1st 3.75, 2nd 2.32, 3rd 1.43, 4th 1.0, 5th 0.75.

New Griffin radiator, reman power steering pump, reman alternator, reman rack and pinion, and reman ABS system

Custom Front Mount Intercooler: 24” x 12” x 4” Cxracing IC core with 2.75”
89 Thunderbird SC
427 SBF Twin PTE 6266s, T56 Magnum XL
9.5:1, AFR 205cc, 222/227cam, TFS R intake, FID 1600cc, 93 Pump Gas
EEC=L1C (92 5.0 Tbird), BE/QH, GSALC

decipha

Re: Dashpot issue: rpm dip prior to hanging idle

Post by decipha » Sun Sep 21, 2014 4:23 pm

so in other word its pretty much stock lol

It shouldnt suck down anymore than 28 kg/hr at 800, 32 isnt too far off

dthompson
Gear Head
Posts: 20
Joined: Tue Jan 21, 2014 9:02 pm

Re: Dashpot issue: rpm dip prior to hanging idle

Post by dthompson » Sun Sep 21, 2014 4:47 pm

idle speed is set at 900
89 Thunderbird SC
427 SBF Twin PTE 6266s, T56 Magnum XL
9.5:1, AFR 205cc, 222/227cam, TFS R intake, FID 1600cc, 93 Pump Gas
EEC=L1C (92 5.0 Tbird), BE/QH, GSALC

decipha

Re: Dashpot issue: rpm dip prior to hanging idle

Post by decipha » Sun Sep 21, 2014 6:13 pm

oh well thats about right then

go ahead and dial in dashpot

dthompson
Gear Head
Posts: 20
Joined: Tue Jan 21, 2014 9:02 pm

Re: Dashpot issue: rpm dip prior to hanging idle

Post by dthompson » Sun Sep 21, 2014 7:38 pm

So ive been through your dashpot article several times. here is what ive last tested...(I started with an exact following of your article.)

dashpot preposition (I actually think this might be a little high in the mid range. Sometimes the rpms jump up on declutch around 2000rpm if I don't coast for a few seconds first)
16384 1.8999
2000 1.8999
1500 1.4248
500 0.3999
0 0.0000

dashpot decay
16.00 0.0300
0.75 0.0300
0.50 0.0149
0.25 0.0020
0.00 0.0010
0.00 0.0010
0.00 0.0010

Dashpot Min Clip
16383.75 0.10
2200.00 0.10
1200.00 0.10
0.00 0.10
0.00 0.10

idle neutral air
4080 1.92
2000 1.92
1408 1.80
896 1.20
0 0.00

spark mult vs dashpot
1.99 0.750
0.10 0.852
0.00 0.953
0.00 0.953

ITHBMA is 1.0
I see that during idle the isckam2 ranges somewhere between 0 and 0.06. the isc duty cycle is in the low to mid 30s


generally what I see is a little dip as the rpms fall and hit the min clip and then they comes back up as shown in the image. I can live with this although I don't like it. What is problematic is when it doesn't catch the rpms. This seems to happen when im at a stop light and need to move up one car length (really irritating). its hard to be in the middle of a busy intersection and to use brake clutch and gas when it starts to stall out.
89 Thunderbird SC
427 SBF Twin PTE 6266s, T56 Magnum XL
9.5:1, AFR 205cc, 222/227cam, TFS R intake, FID 1600cc, 93 Pump Gas
EEC=L1C (92 5.0 Tbird), BE/QH, GSALC

decipha

Re: Dashpot issue: rpm dip prior to hanging idle

Post by decipha » Sun Sep 21, 2014 8:03 pm

that shit is jacked, if it were me id completely revamp the whole idle routine

change the preposition to

xxx 2.2
3500 2.2
0 0
0 0

then work the decay to get it how u want it
set 0=0 in the decay always

dthompson
Gear Head
Posts: 20
Joined: Tue Jan 21, 2014 9:02 pm

Re: Dashpot issue: rpm dip prior to hanging idle

Post by dthompson » Sun Sep 21, 2014 8:50 pm

ill give the suggested changes a try hopefully tomorrow night.

when you say revamp the whole idle routine, is there something that doesn't look right other than the dashpot changes you specifically mentioned? That concerns me because I must have missed something when I tried to do the idle 101 setup recently. I was able to get the throttle body adjusted so it would run with the IAC unplugged, and the IAC duty cycle around 30-35% at idle, ithbma is 1 with my idle airmass around 1.2 (this seemed to be a pretty close to what you recommended of (.1 to .18 less than idle airmass). desmaf and maf match up pretty close in my logs. spark at idle usually averages around 20. I thought I had the idle set pretty good, but Im still pretty new to all this stuff.
89 Thunderbird SC
427 SBF Twin PTE 6266s, T56 Magnum XL
9.5:1, AFR 205cc, 222/227cam, TFS R intake, FID 1600cc, 93 Pump Gas
EEC=L1C (92 5.0 Tbird), BE/QH, GSALC

decipha

Re: Dashpot issue: rpm dip prior to hanging idle

Post by decipha » Mon Sep 22, 2014 6:58 pm

I just like it simple is all

as long as it idles fine all is well

dthompson
Gear Head
Posts: 20
Joined: Tue Jan 21, 2014 9:02 pm

Re: Dashpot issue: rpm dip prior to hanging idle

Post by dthompson » Mon Sep 22, 2014 9:13 pm

ok did some work on it today...

I did not have good luck with setting the 0=0 in the decay. The dashpot got stuck at .02 and the rpms where yo-yoing around for 40 seconds until I set 0=0.0007

I like the cleaned up preposition, but it would max out my duty cycle... I remember reading that was a bad thing so i think i will lower it to 3500=1.9

I logged all day today as i drove to work and back paying close attention to the KAMRFs in the lower maf points. I felt that the bottom of the maf curve could have been reduced 5%. I made that change when i got home and cleared the KAMs and it seemed better tonight. With this change i went back and edited the neutral idle air and ithbma stuff to reflect the updated MAF curve. (MAF Airmass - ISC airmass at 35%dc = Ithbma) I know where the MAFV point was at idle, so i used that, and the IAC is at 35% at idle, pretty straightforward. I used the MAF airmass for the idle neutral air at the idle rpm.

Overall the changes are positive so far. I need to do some more driving and see how it does. It still dips moderately on declutch when dashpot has already decayed to the min clip (prior to me pushing the clutch in). This may be a normal sort of thing? I cant slow it down, because dashpot has already decayed to the clip and spark is being held constant by dashpot multiplier. Really i don't see how you can control this dip other than let it happen unless im missing something. I am curious how it will do around the stop lights.
89 Thunderbird SC
427 SBF Twin PTE 6266s, T56 Magnum XL
9.5:1, AFR 205cc, 222/227cam, TFS R intake, FID 1600cc, 93 Pump Gas
EEC=L1C (92 5.0 Tbird), BE/QH, GSALC

decipha

Re: Dashpot issue: rpm dip prior to hanging idle

Post by decipha » Mon Sep 22, 2014 9:46 pm

if u have a long declutch coast and dashpot has expired then u need to have enough in the dasmin clip to prevent a declutch stall

usually this is about .18 or so, you also dont want it too high to hang rpns during normal putting around

i usually make dashpot decay to 1000 fairly quickly then very slowly decay to a stable idle, ive never had any complaints about it

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