Ok an un-named person and I are arguing over a "trick" as he claims

this person "claims" that flipping your vss switch makes your car run richer, personlly out of at least 30 dyno runs on my car with cams, without cams, and with boost I have never seen a change in a/f's nor have a few J's I have dynod with that had this done.


My Question


Would flipping a VSS Switch make the car run richer?



LE61T PTE6262 Powered

flipping the vss off actually @!#$ up alot of @!#$ on the pcm, you want to run richer tune for it dont be a cheap typical cavalier dumbass



1989 Turbo Trans Am #82, 2007 Cobalt SS G85

No my questions states will it make the car run richer?

as far as I have seen between 4 different J bodies in my area it has had NO effect.



LE61T PTE6262 Powered

its no more effective than disconecting the primary 02 sensor



1989 Turbo Trans Am #82, 2007 Cobalt SS G85

run richer .... the only thing that happens with my car when I go to hit the vss swtich is if I leave it flicked for too long I get a CEL ....... thats about it ....

Richer ???? uhhh no .....

Lee


JDM Civic Hatch
Status: Parting Out Turbo Kit....
14.224 @ 102.01MPH @ 5.5psi.... 2.3 60'
Next: Civic JDM B16a2 w/GSR LSD Turbo - Goal 300whp 1400lbs...

this has been centralized to all 04+ cars that dont run open lopp



LE61T PTE6262 Powered

It depends on the car... in your case, Phil, probably not. In the case of newer cars, like 2004+, probably so.

The EPA is constantly breathing down the neck of manufacturers to reign in emissions under a laundry list of conditions. Idling, accelerating under load, accelerating with light load, decelerating, revving in neutral....etc....you name it, they've got a requirement for it.

Add to that the fact that more and more states have added "treadmills" to their emissions testing and you've got a complicated situation. Now you've got a mandate that says the computer has to keep an increasingly tight leash on emissions while the car is moving at various speeds under wildly varying load conditions. Responding to this, GM revised the coding in the ECM to make the VSS part of the emissions sensor block, with all the associated pass/fail results. If you remove/cut/disable any emissions related sensor you throw the computer into "limp" mode...open loop, lower fuel ratios, retarded timing, etc. Gone are the days when WOT meant fuel dumps and 11.5:1 A/F rations. Now in closed loop, even at WOT under full load, the ECM sits there and regulates it like Scrooge counting pennies.

Cutting the VSS is a simple way to force the computer into open loop without sacrificing the input of other sensors. Remaiing sensors are still read, unlike some older ECMs that went into COMPLETELY open loop operation.

So, to answer the question...YES, on newer vehicles utilizing GM's new code removing the VSS will allow the computer into open loop mode. 2004+ is a near definite that you've got this code. 2003 is iffy. 2002 and older, negative.

On a side note, just for my own curiosity....can't we all just get along? I seem to recall everyone is here for the same reason, but lately it's been all about "oh, I found out first" or "oh I'm MORE stock" or "so-and-so is keeping secrets". Give me a @!#$ break people. Grow up, tune your engines, and have fun while you're doing it. Check your attitudes at the door, and don't assume anything. ANYONE can teach you something new at any given time...especially when you don't expect it, so keep your eyes and ears open.






09:f9:11:02:9d:74:e3:5b:d8:41:56:c5:63

I have my turbo kit tuned by simply unplugging my vss....

sorry im a smart @ss

I wonder if the recall for the stalling problems of the 03 ECO's affects the ECU's open loop operation...........................That would explain why SOME 03's have this "problem." Hmmmmmm I should hook up my wideband soon!

Looking at my service manuals... the VSS seems to have no bad effects on a manual transmission car. There aren't even codes associated with it.

I haven't needed to disable the VSS on my manual trans yet... does it throw a code if you leave it off? If so, which code(s)?

I can understand an auto having issues. There's a code listed for that. P0502. Long list of stuff that goes wrong with that one, all sorts of conditions to set the CEL... yadda yadda yadda.

(Please, let's keep this civil and not get into "how do I disable the VSS" because no one is going to tell you... n00bs )

...j

JimmyZ wrote:

On a side note, just for my own curiosity....can't we all just get along? I seem to recall everyone is here for the same reason, but lately it's been all about "oh, I found out first" or "oh I'm MORE stock" or "so-and-so is keeping secrets". Give me a @!#$ break people. Grow up, tune your engines, and have fun while you're doing it. Check your attitudes at the door, and don't assume anything. ANYONE can teach you something new at any given time...especially when you don't expect it, so keep your eyes and ears open.

We were getting along me and this unnamed person were having a discussion where I disagreed and posted about it, after it was explained to me about the varying years being only 04+ I understood why this could happen



LE61T PTE6262 Powered

QBE (73H 800573D 0N3) wrote:

JimmyZ wrote:On a side note, just for my own curiosity....can't we all just get along? I seem to recall everyone is here for the same reason, but lately it's been all about "oh, I found out first" or "oh I'm MORE stock" or "so-and-so is keeping secrets". Give me a @!#$ break people. Grow up, tune your engines, and have fun while you're doing it. Check your attitudes at the door, and don't assume anything. ANYONE can teach you something new at any given time...especially when you don't expect it, so keep your eyes and ears open.

We were getting along me and this unnamed person were having a discussion where I disagreed and posted about it, after it was explained to me about the varying years being only 04+ I understood why this could happen

That wasn't intended as a jab at you Phil, or a knock on you asking this question. It was a good question that deserved a good answer.

I was referring more to the general state of affairs in this forum lately. I can understand being competitive, but it seem slike everyone has been at everyone else's throats lately...I was just wondering why.






09:f9:11:02:9d:74:e3:5b:d8:41:56:c5:63

as I have yet to mess with any J newer then 02, I cant say......... but Jimmy's theory seems logical..........

I also only have service manuals up to 02......

Lenko..... I cant remember what code pops for the VSS...... its been so long since I've gotten it.

I can see how a certian *company* wouldn't want people disabling the VSS to achieve better a/f ratios.....




SPD RCR Z - '02 Z24 420whp
SLO GOAT - '04 GTO 305whp
W41 BOI - '78 Buick Opel Isuzu W41 Swap

who in the Jersey J's has the VSS mod? certainly no one who was at dyno day... Rich has megasquirt, meaning the fuel based speed limiter is still there, but since the ecu has no control over the injectors, it can't do anything about it. PJ doesn't have it, and I didn't need it because VW ecu's don't suck.... Nitro did it i think but thats a 2.4 so thats completely different. Thats the only Jersey J's that were at dyno day.




Arrival Blue 04 LS Sport
Eco
Turbo
Megasquirt
'Nuff said

I'll be testing this method on an '04 this weekend hopefully. I'll definatley post the results.

Scarab (Jersey Jay 1.8T) wrote:who in the Jersey J's has the VSS mod? certainly no one who was at dyno day... Rich has megasquirt, meaning the fuel based speed limiter is still there, but since the ecu has no control over the injectors, it can't do anything about it. PJ doesn't have it, and I didn't need it because VW ecu's don't suck.... Nitro did it i think but thats a 2.4 so thats completely different. Thats the only Jersey J's that were at dyno day.

and I've only ever been at 1 dyno day in my life?



LE61T PTE6262 Powered

QBE (73H 800573D 0N3) wrote:

Scarab (Jersey Jay 1.8T) wrote:who in the Jersey J's has the VSS mod? certainly no one who was at dyno day... Rich has megasquirt, meaning the fuel based speed limiter is still there, but since the ecu has no control over the injectors, it can't do anything about it. PJ doesn't have it, and I didn't need it because VW ecu's don't suck.... Nitro did it i think but thats a 2.4 so thats completely different. Thats the only Jersey J's that were at dyno day.

and I've only ever been at 1 dyno day in my life?

or for that seeing matter any jbody dynoing by itself?




LE61T PTE6262 Powered

Lenko, John Lenko wrote:Looking at my service manuals... the VSS seems to have no bad effects on a manual transmission car. There aren't even codes associated with it.

I haven't needed to disable the VSS on my manual trans yet... does it throw a code if you leave it off? If so, which code(s)?

I can understand an auto having issues. There's a code listed for that. P0502. Long list of stuff that goes wrong with that one, all sorts of conditions to set the CEL... yadda yadda yadda.

(Please, let's keep this civil and not get into "how do I disable the VSS" because no one is going to tell you... n00bs )

...j

Yes on a manual it will throw a code. I got one once, but never checked to see what it was because I did not have a way. It seems to be a hit and miss thing if it will. The longer you leave the switch on the better chance of getting it.
For the auto's if you use it only after you change into over drive it will not throw a code (at least from my testing).

Quote:

I'll be testing this method on an '04 this weekend hopefully. I'll definatley post the results.

Are you going to be on a dyno????? If not how are you testing this? Do you have a wideband?

Jimmy very interesting info. I did not know that.



FU Tuning

i never knew that, but i dont plan to ever us the VSS mod. . .

and Jimmyz you can thank yourself for the gereral attitude alot of people have here. You turned this whole forum in your little war against street racing. There have been more flame threads caused by you in the last 3 months than ive ever seen on any forum.


2006 Black Cobalt SS Supercharged G85
13.91@102.77

I'm at work now, but later when I'm home I'll post the stuff associated with that code. There's a lot of different conditions based on other sensors, as to how it affects the open/closed loop operation. Maybe some insight, and an actual answer to the original question

I don't have the 'vert on the road at the moment, otherwise I'd try and set that code. I have no problem setting the lean code (p0171) right now tho.

i read once on here that once you turn on your a/c you car runs richer.

lol

How do you do the VSS mod? lol just kidding

I dont have it done (04 cav) but i would think that it would only throw a no signal code for the VSS being cut out. Maybe if it dumped even more fuel into the engine (I dont know if it does) then it would run a bit richer.


~Riki

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Car Domain Site

The newer Ecotec PCM wants to keep a 14.7:1 air/fuel ratio no matter what, even at wide open throttle. I watched Aaron52788 dyno his 04 Eco with the Hahn kit, even with the FMU raising the fuel pressure through the roof the PCM compensated for it to make a 14.7:1 air/fuel ratio. Its actually pretty impressive that it can instantly correct it's a/f ratio even when the fuel pressure is doubled.

The rumor has it that forcing the PCM into open loop by cutting the VSS signal will allow you to raise fuel pressure to add additional fuel without the PCM seeing it and bringing it the a/f ratio back to 14.7:1. I have no proof of this working but it sounds logical and people claim it works. What i am unsure of is if there are any negitive effects of this solution, such as how it may affect ignition timing or other things.



- 93 mph in the 1/8 mile
Member of J-Body Of Michigan.

Quote:


The newer Ecotec PCM wants to keep a 14.7:1 air/fuel ratio no matter what, even at wide open throttle. I watched Aaron52788 dyno his 04 Eco with the Hahn kit, even with the FMU raising the fuel pressure through the roof the PCM compensated for it to make a 14.7:1 air/fuel ratio. Its actually pretty impressive that it can instantly correct it's a/f ratio even when the fuel pressure is doubled.

The rumor has it that forcing the PCM into open loop by cutting the VSS signal will allow you to raise fuel pressure to add additional fuel without the PCM seeing it and bringing it the a/f ratio back to 14.7:1. I have no proof of this working but it sounds logical and people claim it works. What i am unsure of is if there are any negitive effects of this solution, such as how it may affect ignition timing or other things

would be nice if hp tunes or some program could make it stay at a nice 12:1

thats interesting to know.. i hope bill and adam hahn see this. wonder what happens with adams sunfire when he races. i know they just unplug the vss. wonder how this affects the portfueler and it adding fuel when the ecu is trying to compinsate.

Ok, I'm home. There's two codes, P0502 VSS circuit low input and P0503 VSS circuit intermittent. We're looking at P0503. It's a long one...

So, I'll summarize.

When the PCM detects a loss of vehicle speed while the vehicle is in motion, then DTP P0503 sets. DTC P0503 is a type B DTC.

Type B DTC is an emissions-related failure. The first failure does NOT turn on the MIL. It stores the DTC in memory as a Failed Last Test (pending code, basically). The second consecutive failure WILL turn on the MIL, but a second non-consecutive failure will not.

Anyway... P0503 has conditions...

- No TFP manual valve position switch DTP P1810 (transmission fluid pressure valve position switch circuit).
- The engine is running
- The time since the gear select leave change is greater than 6 seconds, and
- An increase in output speed of 500RPM or greater has no occurred for greater than 5 seconds.
Also
- Output speed drops greater than 1,200 rpm for 3 seconds

When P0503 sets...

- The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in whch the conditions (above) are met
- The PCM commands maximum line pressure
- The PCM freezes shift adapts from being updated
- The PCM calculates output speed from input speed, engine speed, and commanded gear
- The PCM records the operating conditions when the Conditions above are met, and stores this information as Freeze Frame and Failure records.

Yadda yadda yadda...

Nothing about Open Loop Mode. Nothing. And that's on an auto. I find it hard to believe that the manual would set it to Open Loop mode if the auto isn't.

Mind you... this is on a 2000 service manual. Someone check the 2004 for me