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7/07/2019 1:59 PM  #1


EFI VSS TIMING OCTANE-Resolved

Noticed that engine would lightly ping during heavy acceleration on hot days.  I did have timing at 12-13 degrees initially, therefore backed it off to factory 10 degrees.  Light pinging still occured, it did lighten up.  My understanding, ecm uses VSS to pull timing back as per charts in program (remanufactured A9L from NAPA 7 years ago).  Temporarily connected VSS to ecm yesterday. Verified VSS has variable voltage output prior to and while connected to ecm.  Light pinging still occurs,.although yesterday wasn’t hot...greater than 75 around here.

Other than shorty headers at this moment, what is next?
BTW, tank is still pretty full and I have been running only 87 octane.
Plan to step up to next level octane to see if it stops.
I usually try, you know how that goes, to make one change at a time. 🤷🏻‍♂️

I don’t recall it doing this prior to swap into ‘65... yet again it was truly factory stock before swap too.

This is combination on engine:

Stock ‘92 5.0 long block
Stock E7 heads (TE bumps knocked down and gasket matched...first attempt at porting...
                            didn’t go hog wild)
Hooker long tube headers ( O2 sensors midway on 3” collector section)
2.5” dual exhaust (mufflers and tailpipes)
Stock ‘92 T5 transmission
3.25 r/p on Currie limited slip
235/40/18 tires

Last edited by Nos681 (7/14/2019 7:29 PM)

 

7/07/2019 2:37 PM  #2


Re: EFI VSS TIMING OCTANE-Resolved

I envy those that can hear an engine ping. For me those days are long gone. I also have no idea what to do except run better fuel.


Gary Zilik - Pine Junction, Colorado - 67 Coupe, 289-4V, T5
 

7/07/2019 2:42 PM  #3


Re: EFI VSS TIMING OCTANE-Resolved

That generation computer didn't use VSS for a whole lot, maybe decel. I do not remember there ever being any sort of VSS related timing tables or scalers to be honest.

You are setting the timing with the spout out right? With 87 I wouldn't run more than 10 deg. Also what was the engine temp? You're using the stock MAF? Might also want to check base fuel pressure and see what the plugs look like. Do you have the EGR?

 

7/07/2019 3:34 PM  #4


Re: EFI VSS TIMING OCTANE-Resolved

Base at 10 with spout out. Erg valve and evp solenoid connected and working. No coolant on egr spacer, left it dry. Plan to change to 2000 explorer intake next stage.  Plug/cap coolant lines to and from at intake and heater tubing. TAB and TAD removed, purge solenoid connected (no canister and not connected to intake). Running 190-195 degree thermostat (same used in ‘92 before swap... ‘65 pony gauges...1/4 on gauge...never overheated in +2100 miles this year,  289 two row (1” tubes, 17” wide) aluminum radiator with electric fan (on with ignition via relay...KISS), stock ‘92 MAF, stock 19# injectors (cleaned and rebuilt during swap), don’t have fuel rail pressure gauge to be able to know...using stock non adjustable regulator.  Edelbrock/BBK 70mm throttle body and EGR spacer.  Donor had less than 74k miles, all original motor/transmission to donor as well. VIN numbers on all matched.

     Thread Starter
 

7/07/2019 3:39 PM  #5


Re: EFI VSS TIMING OCTANE-Resolved

Agree with backing up the timing or buying 91 to 94 octane fuel. 


John  -- 67 Mustang Coupe 390 5 speed
 

7/07/2019 3:39 PM  #6


Re: EFI VSS TIMING OCTANE-Resolved

Sounds solid, I'd prob stick with 10 deg and go up a grade or two in fuel. I do think it would be a good idea to at least pop a fuel pressure tester on the rail (you can try to rent one) and see what your base fuel pressure  with vacuum line off at idle for reference.

 

7/07/2019 5:28 PM  #7


Re: EFI VSS TIMING OCTANE-Resolved

I'm with Raymond, VSS only used for dashpot delay on decceleration with a manual ECM.
Fuel pressure is also worth checking as well as cleaning the MAF.
Can you pull codes? Not every code shows as a lit CEL.


"Those telephone poles were like a picket fence"
 

7/07/2019 6:18 PM  #8


Re: EFI VSS TIMING OCTANE-Resolved

Dan and I spoke about this and I suggested that having the HEGO's way back in the collector and far from the rear exh port may have an effect. 

What does anyone else think?

BB


"you get what you pay for, good work isn't cheap, and there are NO free lunches...PERIOD!"
 

7/07/2019 6:35 PM  #9


Re: EFI VSS TIMING OCTANE-Resolved

Great advice. Appreciate the information. I will start with simple and see if I can borrow/buy a gauge to see if pressure is dropping off too during acceleration.  I know I had 1 or 2 soft” codes that didn’t trigger CEL before swap, which pertained to emissions... I don’t remember the numbers..thirty something....they should make a show like that!🤪.
VSS was used for cruise control as well.

Thought I had read about EEC IV having fuel maps, could have applied to speed density.

Are there issues with long tubes and O2 placement?  (I did verify O2 heaters have power).

Are there settings in ECM for sampling time of exhaust quality?   Thought I read that about “inner workings of EEC IV ECM” as well. 

I don’t know, that’s why I ask.
First time digging into this field of engine management.

Thanks again for your help.

     Thread Starter
 

7/07/2019 6:51 PM  #10


Re: EFI VSS TIMING OCTANE-Resolved

To add to BB question.

Does HEGO have to sample all exhaust ports?
Such as pulse sample of each port exhaust quality and then make a/f ratio corrections.

Thought it did, the reason it was placed in header collector. Factory exhaust as well as aftermarket have HEGO sampling all exhaust ports per bank.

I will start with octane first and go from there.
Thanks guys!

     Thread Starter
 

7/07/2019 7:47 PM  #11


Re: EFI VSS TIMING OCTANE-Resolved

Bullet Bob wrote:

Dan and I spoke about this and I suggested that having the HEGO's way back in the collector and far from the rear exh port may have an effect. 

What does anyone else think?

BB

It's possible, but I think you'd get codes for this. Being too far downstream let's them cool down and get "lazy" for lack of a better word. They stop switching back and forth around stoich or do so slowly. I can't remember the code off the top of my head.

I'm not inclined to think it's the O2's because Nos681 mentioned pinging under heavy acceleration which means he's almost assuredly dropped out of any closed loop control. The old computers only went closed loop at idle and light-part throttle. You know, there's actually a WOT breakpoint vs TPS voltage. Might be a good idea to check TPS voltage, but I honestly think that's a longshot. Never hurts to check TPS at closed throttle though.

If anything I still think it's a bit lean or just too much timing for the low octane fuel.

 

7/08/2019 5:09 AM  #12


Re: EFI VSS TIMING OCTANE-Resolved

The VSS had nothing to do with timing in the stock setup.

The stock O2s are heated, which should negate any issue with placement.  I've run longtubes on plenty of Fox cars and never had an issue with pinging related to O2 sensor placement.  Though tuning is best done with an A/F ratio gauge with data logging so you can verify lean/rich conditions.  The stock O2s are not wideband, so they only read a very narrow range and call it "rich" or "lean".  What they don't know is how rich or lean.

On good fuel we ran more than 10 degrees, and we never had any pinging.  We'd bump it up until the car slowed down then knock it back 2 degrees.  We were typically running 12-15 degrees without issue on 93 octane fuel.  If you have the ability to actually change the timing tables though its much better, and then you set it at zero and add timing directly in the computer. 

My question would be, are you sure its actually pinging?  We often had problems with spark scatter on these cars once we got them breathing better.  To the untrained ear this can sound like detonation, but its not.  The factory TFI module simply doesn't have enough dwell to produce a strong enough spark, and the factory coil doesn't throw enough voltage.  If you are still running a stock coil I would get a Screamin' Demon and get a better module.  An alternative is to use the work around of running an MSD to bolster the spark.  I'd bet dollars to doughnuts this is your actual problem.  It was always an issue when we put headers on a car, and you've improved head flow as well. 
 

Last edited by TKOPerformance (7/08/2019 3:39 PM)

 

7/08/2019 10:50 AM  #13


Re: EFI VSS TIMING OCTANE-Resolved

The stock O2s might be heated, but yes, yes you can run them too far downstream. Anyway since this is an open loop issue it doesn't matter.

 

7/08/2019 3:49 PM  #14


Re: EFI VSS TIMING OCTANE-Resolved

Sure, if they are so far that the exhaust gas has cooled to the point that its no longer accurately reflecting the A/F ratio based on what the O2s are "seeing" in terms of temperature.  But in practice over the years we ran long tubes from MAC, Bassani, BBK, and probably a couple others and we never saw an issue with where they had placed the O2s.  Where we ran into issues was when the MAF scaling was wrong, which it always was without tuning.  The idea that MAFs were "calibrated" turned out to be smoke and mirrors.  The only way to calibrate the MAF function was to directly adjust the slope in the computer, but this took over a decade to figure out.  Without doing that you would get all manner of poor running once you swapped injectors and the MAF, because the computer was no longer able to truly "read" the incoming air mass.  The result was a phenomenon I used to call "hunting and pecking", which resulted in the A/F ratios being all over the place and the O2s being unable to help correct it even in closed loop operation due to their narrow band nature. 

 

7/08/2019 3:55 PM  #15


Re: EFI VSS TIMING OCTANE-Resolved

When the ECM  switches from open to closed loop is based on time, ECT and the amount of switching the hegos have done.
Generally, a tuner would add more time to the equation to allow for placement further down stream.
But, as Raymond has said, when under WOT conditions, the ECM reverts to open loop, which has no hego input.


"Those telephone poles were like a picket fence"
 

7/14/2019 6:31 PM  #16


Re: EFI VSS TIMING OCTANE-Resolved

Finally an update.
Takes a little while to burn through a 22 gallon tank with a small block/T5 combo and interference from work. 😜

Settings as found: 13 degrees, 690 rpm, .979 volts tps
Settings as left: 10 degrees, 700rpm, .987 volts tps

Still had pinging.
Burn through 16 gallons of suspected bad fuel.
Refilled with 91 octane (no ethanol added)...best around here unless ya go to airport 😁

Took a 700 mile round trip to Wisconsin for a concert and pinging gone.
(Yes I filled up before returning...to get 700 miles)


Perhaps I got cruddy gas on last filling at Walmart.
I usually don’t fill the ‘65 there just for this reason.
Momentary lapse of reason I guess.

Will check fuel pressure when resources and time permit.
May try increasing timing again too.

I finally realized the other day ECM uses PIP for RPM’s not VSS.
I felt like a dunce when nothing changed with VSS connected...at least now I KNOW.

Thanks for help!  Appreciate it.

Last edited by Nos681 (7/14/2019 6:59 PM)

     Thread Starter
 

7/14/2019 7:46 PM  #17


Re: EFI VSS TIMING OCTANE-Resolved

91 octane corn juice free gasoline at Holiday gas station....glad they carry that...

 

7/14/2019 8:44 PM  #18


Re: EFI VSS TIMING OCTANE-Resolved

Man you guys are lucky.  Nowhere in DE sells ethanol free. @#$%ing sucks. 

 

7/14/2019 9:45 PM  #19


Re: EFI VSS TIMING OCTANE-Resolved

Check marinas. Most rec fuel sold there has no corn juice

 

7/15/2019 5:20 AM  #20


Re: EFI VSS TIMING OCTANE-Resolved

Hmn, never thought of that.  A bit of a hike, but might be worth it.

 

Board footera


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