View Full Version : TDC offset and static desired timing? and IP Durability
What is the difference between TDC offset degrees and Desired timing degrees? Can they be set seperatly?
While having my TDC offset done 2 days ago my TDC read -1.80 and my desired read 4.0 (static), GMCTD's read 8.0 and -1.5. Was my timed incorrectly?
When installing a new IP what is the official GM timing procedure?
[ 05-20-2004, 05:43 AM: Message edited by: AndyL ]
To kick this off -
Factory '94 manual states TDC Offset requires (re)setting if replacing
A. new PCM, which would be blank
B. Inj Pump - drive gear to shaft, shaft to rotor
C. timimg cover - cover to dowels, CKP bore offset
D. Crank Position Sensor - magnetic pickup alignment in plastic casting.
B, C, D would seem to indicate an adjustment due to mechanical\machining tolerance, to properly align optical resolution sensors in IP to reluctor wheel pressed onto the crankshaft.
Correction - IP wheel index has 8 per 360deg, and 128 per 90deg, 512 per 360deg
[ 05-19-2004, 12:54 PM: Message edited by: gmctd ]
Should probably post this data here also!
GMCTD,
Here is some data from my drive while catching a lunch break:
Engine Run Duration=6:49 minutes
Waste Gate Solonoid=69
Fuel Rate=129C8569 (still haven't figured out how to convert that to mm^3)
Desired IP Timing=10.3
Actual IP Timing=10.4
Tranny Fluid Temp=154
Fuel Temp=117
Engine Temp=187
Engine RPM=603
Air Intake Temp=127
I am working on the TDC Offset, Fuel rate, IP Solonoid Open duration parameters. Hopefully I will have that data soon.
Those figures appear correct for idle and stated -1.8deg TDC Offset. Not sure what the Fuel Rate means, but your Desired and Actual Inj timing are ~10.3deg.
Fuel rate should be 8-9mm3, and as you can see temp is only 117deg with coolant temp of 187 deg.
Stanadyne insisted on FSD mounted to inj pump for a reason. Heat soak has to be major cause of failures.
Intake temp is 127 at idle, indicating necessity for charge air cooling - temps will increase as engine rpm and loading increase Boost pressure.
Wastegate - 69% solenoid duty cycle at idle - is closed for quick spool-up.
At hiway speeds 67-69% will allow 7psi boost, will drop with accel input to maintain ~7psi.
Ask the programmer what that Fuel Rate formula represents, and how it is derived.
Must be Closure time, fuel temp, APP position, IP delta velocity off optical sensor, vs PCM program.
Good stuff - keep posting
Originally posted by gmctd:
Fuel rate should be 8-9mm3, and as you can see temp is only 117deg with coolant temp of 187 deg.
Stanadyne insisted on FSD mounted to inj pump for a reason. Heat soak has to be major cause of failures.
Are you saying a fuel temp of 117 is considered low? Does Stanadyne give a desired/perfered runnning fuel temp?
Inj pump 'acquires' it's heat from hot engine oil in timing cover, block temperature, and hydraulic pumping function.
As you can see, with coolant temp at 187deg, internal fuel temp is at 117deg, indicating pump temp is lower than block temp with engine running.
That temp is taken below the Optical Sensor, that black plastic module on top rear of inj pump.
Fuel inlet is top front of inj pump, to driver's- side of Fuel Shutoff Solenoid.
Fuel system is flow thru, returning excess to tank. Return outlet is top front inj pump.
Pump fuel is combined with excess from injectors, via those lines at each injector, in that steel tubing 'manifold' running across front of engine.
When fuel tank temps are at ambient, pump will run cool, indicating advantage to installing fuel cooler in return line to tank.
Pump will run hotter when fuel level in tank is low.
FSD\PMD temperature measurements taken by member 'tbogemirep' indicate the module runs below 140deg off pump, on external heatsink.
Other members have indicated temps between that and 100deg.
So - yes, 117deg is low fuel temperature, considering the environment in which it is flowing.
I have not seen any Stanadyne, or GM, temperature specs, but many FSD\PMD modules are still in service mounted to inj pump.
In my quest for increased IP durability I wonder if this cooler temp is desirable?
I also wonder if the decreased temp increases the viscosity of the fuel further causing abnormal wear?
It would seem to me that with the FSD removed from the pump "heat soak" would not be a problem. If indeed the IP was heat soaked after long running does it matter since it isn't functioning at that time?
As already stated maybe the key is simply super clean fuel? That is probably the easiest prevention method to install.
The elevated temps of 'heat-soak' have effect at startup, but does not appear to be problematical with pump.
Any mechanical device will wear out - the inj pumps more so since low sulphur fuels provide little or no lubricity to the bearings, and close tolerance rotor and pumping plungers
Electronic FSD\PMD module is effected by heatsoak temps.
What is your specific concern with pump durability?
This should probably all be cut\pasted over to your inj pump reliablility post, if you're agreeable?
Yes I would agree.
IMO, and from what I read, the 6.5 IP is still less reliable (even with the FSD relocated) than it should be. An average functional duration should be at least 100K miles, again IMO. I don't have numbers (I know how you hate those :D ) but I bet on average they last much less.
I suppose the concern to me is a basic pride issue. It is a stab in the back when your truck, your dependable friend, lets you down. I would wrench on my truck all night if just to make the slightest improvement.
As a fellow "tinkerer" I am always looking for the smallest ways to improve the design and make sure I am not the broke down guy on the side of the road. Besides that, it is in my blood as an engineer.
I updated the Title of this thread to include IP Durability.
I looked back through the scan data from yesterday specifically looking for "heat soak" information.
With an engine that ran for 10 minutes, engine temperature of 190 degrees = 117 degree fuel temp at 75 degree spring day.
After 1 hour of sitting during lunch fuel temps at startup where 147 degrees. It very quickly diminished as the cold fuel was pumped in.
Maybe this weekend after a longer run I will leave the ignition on and attempt to chart the rising fuel temp to the point at which it starts to cool again. It may have actually gotten much hotter than 147.
By posting this I'm probably condeming myself to immediate catastrophic pump failure, but for the good of the group, here goes.
I have a 1996 vintage pump, the first production model to meet the "blue label-green tag" specs. It was installed in the summer of 1996. I ran it about 30K miles as installed, then I added a beta FSD cooler in the standard location and different FSD. That FSD/cooler combination had about 25K on it from another install. Everything was fine until 2 weeks ago, when the FSD on the cooler suddenly started failing with great regularity anytime the outside temps were above about 60*. Plan A was to revert back to the Pump Mounted Pump Mounted Driver, but either I was not able to get the cable plugged in correctly or it had failed in the interim. Anyhow, I now have over 100K on the mechanical part of the pump, a new FAS, an FSD that lasted about 100K, and one that is in undetermined condition mounted on the pump.
So, what does it all mean? Got me... I think the mechanics of the pump are as reliable as the DB2, maybe more so (50K on a (ford) before it quit.) The FSD is definitely the weak point, but I'm unclear as to whether any of these "cooler" ideas help, although they sure do make it easier to change!
JohnC,
Try tightening the nuts under the black plastic caps on back of the FSD(s), reconnect & see what you get. A good snug tightness but no need for 100# torque. That may re-contact a bad connection on the transistors & cure the FSD bug for a time; worst case is some wrenching time to no avail.
IMO, the FSD cooler in the on-manifold position is a minor improvement over the IP mount; the FSD isn't heating up the IP & its contents, but is still susceptible to heat soak during hot days & hot shutdown, thereby cycling its electronics thru expansion/contraction swings that can't be a good thing. At the end of the day, its a gizmo of substantially variable QC from Stanadyne, so YMWV and it does not appear to be sufficiently uniform in failure to become a predictable device. Remote mount is way-mo-bettah when you can get the FSD to ambient air conditions; it'll reduce the large expansion swings to 140 degree max or less (vs 165 or more, maybe 200 during a good hot shutdown).
Originally posted by ucdavis:
Try tightening the nuts under the black plastic caps on back of the FSD(s)
Been there. It worked until the warm weather returned, then back to regular, predictable failure.
IMO, the FSD cooler in the on-manifold position is a minor improvement over the IP mount; the FSD isn't heating up the IP & its contents, but is still susceptible to heat soak during hot days & hot shutdown, thereby cycling its electronics thru expansion/contraction swings that can't be a good thing.
Like I said, it makes i easy to change.
[Q]Remote mount is way-mo-bettah when you can get the FSD to ambient air conditions; it'll reduce the large expansion swings to 140 degree max or less (vs 165 or more, maybe 200 during a good hot shutdown). [/QB]
It's certainly a good story, but I'm not convinced it really matters. I haven't heard a single person say they had an FSD that lasted 100K regardless of where it is mounted. Sounds like we need a poll to find out...
I have the same inj pump JohnC has, mileage unknown but not failing. Casting code '95, date code 09-15-95.
I believe the engine is a Goodwrench unit from sometime after that build-date.
Earlier this month I pulled the FSD\PMD off the pump for 2.5-year checkup, to find the four driver nuts were still at 1/4-turn tight, where I had 'set' them.
The white silicon thermal compound I had filled the cavities with was still jelled and in paste form.
While not intended to conduct heat thru that quantity of paste, it serves as an excellent non-flowing anti-oxidant in high heat areas.
The four Torx mounting screws were loose, again, indicating probability of future problem.
So, I'm considering remote-mounting, possibly in the air intake path or air-box where positive air-flow is available when engine is running.
Also allows for easier inj pump adjustment for some R&D I'm involved in.
Originally posted by gmctd:
Also allows for easier inj pump adjustment for some R&D I'm involved in. Any chance you could elaborate? :D
Nothing spectacular - just some TDC\Desired vs chips, and other stuff.
Originally posted by gmctd:
Fuel rate should be 8-9mm3, and as you can see temp is only 117deg with coolant temp of 187 deg.
Is that mm3 per individual stroke?
So:
8mm3* 8 Cylinders * 600 RPM = 38400mm3 / 2 because it's a 4 stroke = 19200mm3 per minute or 0.3 gal per hour.
With a 30 gallon tank I could idle for 100 hours :D
Originally posted by AndyL:
19200mm3 per minute or 0.3 gal per hour.
Math error! 19200 mm3 (cc) per minute is roughly 5 gallons/ minute!
However, the fuel rate is expressed in mm3 per 100 (or is it 1000?) strokes...
Originally posted by JohnC:
</font><blockquote>quote:</font><hr />Originally posted by AndyL:
19200mm3 per minute or 0.3 gal per hour.
Math error! 19200 mm3 (cc) per minute is roughly 5 gallons/ minute!
</font>[/QUOTE]mm3 Cubic milimeters is not the same as CC or cubic centemeters. There are 1000 mm3 in 1 CC.
Now you see why I avoid numbers like plague - them fickle li'l devils are vicious!
;)
Originally posted by AndyL:
mm3 Cubic milimeters is not the same as CC or cubic centemeters. There are 1000 mm3 in 1 CC. Duh! Of course, you are correct. However, the fuel rate still represents 100 (or maybe 1000) strokes. (I think...)
Memory, the second thing to go....
marktara
05-21-2004, 14:26
AndyL,off topic but where did you get transmission temp from? Just figured if computer is already measuring it,just have to find a way to display it and avoid installing temp sender in tranny
4l80E, and probably 4L60E, has internal temp probe so PCM can modulate trans functions if in over-heat mode.
Data is there, but part of OBD-II protocol - serial data out for interpretation by scan tool.
Would be nice, tho.......
Originally posted by gmctd:
Data is there, but part of OBD-II protocol - serial data out for interpretation by scan tool.
Would be nice, tho....... I am currently working on an OBD2 data display device. It will be a couple more months, I am still waiting for a few of the Enhanced parameter codes.
One way only, I don't have access to a Tech2 for data stream analysis.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.