I have the F40 (G6) speed and the VSS is going through a Dakota Digital SGI-5, and it's close, but no cigar. If I knew the F40 VSS frequency I could dial it in better, but my web and forum search has come up empty.

Does anyone know for sure?? And I have seen a couple of different numbers for the 4T60e, does anyone know the VSS frequency of that tranmission?(24,000??).

All replies will be appreciated, thanks!

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88 GT T-Top, 88 Fastback Chop-top (Archie #14), 1984 Indy, 88 Chop Top T-top**SOLD**
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I'm pretty sure you're right with the frequency of the 4t60e being 24000ppmi. The F40 6 speed is 60,000 ppmi (with a 24.2" OD tire anyway). The sensor picks up the differential teeth and i hunted back for a PM from Joseph Upson and he said the diff has 72 teeth.

Okay Zac you are the man!! I even lurked on a G6 board but could not find this information anywhere. I'm searching for a better idle and I think this will help. Thanks!!!

quote Originally posted by Zac88GT: I'm pretty sure you're right with the frequency of the 4t60e being 24000ppmi. The F40 6 speed is 60,000 ppmi (with a 24.2" OD tire anyway). The sensor picks up the differential teeth and i hunted back for a PM from Joseph Upson and he said the diff has 72 teeth.

Heh, no kidding! I just took a peak for myself. I was a little suprised to see that It actually uses the ring gears teeth as a VSS pickup. Ingenious. I hope I can re program my ECM to understand THAT many teeth.

the PPM will not help your idle unless you are moving. If your speedo is accurate in the pcm, you will gain some "idle while moving" benefits.

In the 3800's if the car gets rolling fast enough, the idle will jump up to 1100 rpms, but the speed sensor does not seem to register at all under 8mph, so it works well.

[This message has been edited by darkhorizon (edited 07-11-2008).]

quote Originally posted by darkhorizon: the PPM will not help your idle unless you are moving. If your speedo is accurate in the pcm, you will gain some "idle while moving" benefits.

Yes! It's the "idle while moving" where I'm having a problem. At rest it's purring like a kitten at about 1000 rpm. But when I'm slowing to a stop and push in the clutch, the engine roars to 2,000 rpm and won't settle down until the vehicle comes to a complete stop.

Depending on ecm used, you can run the VSS directly to the ECM (vs. through the speedo first) and then change the VSS PPM value in the ecm. I am running the 7730 ecm and a 93 getrag with the late model magnetic VSS. With 26500 for the PPM value the ecm reads the correct vehicle speed. It will take some trial and error to find the right value, but this method can work on atleast the 7730 ECM. Once the ecm reads the speed correct, then you can wire up the ECM to control the fiero speedo as well with the simple speedo interface circuit.

I use the dakota digital just to run the speedo and it will bounce around some when the car is stopped. If the Dakota Digital is sending the signal to the ecm, then these false speed spikes could make the ecm think the car is moving (when it is not) and raise the idle back up.

[This message has been edited by fieroguru (edited 07-11-2008).]

The PCM is a Stock 92 Seville. Is that a 7730? I hear Rockcrawal might be able to reprogram the chip to read 60,000 but he hasn't done it yet.

I am worried that a noisy SGI-5 might create more problems than it solves.

quote Originally posted by jscott1: The PCM is a Stock 92 Seville. Is that a 7730? .

Nope.

quote Originally posted by fieroguru: Nope.

I didn't think so.

Okay I have confirmed through test with my frequency generator that the F40 VSS is 60,000 ppm and I have also confirmed that my ECM (stock 16132240) is still expecting a 24,000 ppm signal, despite the fact that my chip was reprogrammed for a manual transmission.

So I have two options...

1) try to have my chip reprogrammed to 60,000 ppm, (is this even possible?) or

2) Put the SGI in-line between the VSS and the ECM and hope that it's not so noisy that it creates a jumpy idle.

For what it is worth, I confirmed that 60,000 can be saved as the VSS PPM (or road constant) value on the 7730 in both Tuner Pro RT and RT Tuner. I haven't check it yet to see if it will work in the car yet, but the 7730 originally had 4000 as the value and I run 25600 on mine and it works just fine.

You might want to call whoever did your chip and ask about having them send you one with the 60,000 value.

I can save 7,372,800 pulses per mile max on mine. Doesn't mean it can read that high.

quote Originally posted by fieroguru: You might want to call whoever did your chip and ask about having them send you one with the 60,000 value.

I'm not sure who burned it...

I just finished rewiring and recalibrating the SGI and it's working well enough. I went on a cruise with the GPS and dialed it in in real time. My speedo is off a bit, but using the scanner I got the speed in the ECM perfect.

Now the problem is that it didn't fix my sail-on problem. I replaced the ISC and followed Rockcrawl's adjustment procedure and it seems to be operating...

But when I let off the throttle the idle goes up to about 1600 rpm and won't go to idle until the car is going less than 5 mph. It's very frustrating. I'm tempted to rip out the ISC and throw it away, but I know that would cause other problems. I'm going to play with it some more maybe I can make it better.

On the positive side, the throttle body cleaning I did in step 1 seems to have solved my stumble problem.

For grins I entered the 60,000 in the VSS PPM value this morning before driving to work and it lowered the speed about 1/3 and worked up past actual interstate speeds. I suspect for the 7730 owners, they can just enter the 60,000 value and be done when converting to the F40 6 speed.

quote Originally posted by jscott1: But when I let off the throttle the idle goes up to about 1600 rpm and won't go to idle until the car is going less than 5 mph. It's very frustrating. I'm tempted to rip out the ISC and throw it away, but I know that would cause other problems. I'm going to play with it some more maybe I can make it better.

...it nevers really goes away (the sail on condition) - the idle learn procedure just allows you to lower the target rpm. Mine sits at 1400 rpm till the car drops below the target speed. I for one, do not see a reason why GM decided to tie the idle to road speed vs the TPS sensor.

Your prom would still be set for the 26000 (the auto setting) unless Archie set the ship out to be reprogrammed when he installed the 6 speed - and there are really only 2 people that can burn the 4.9 chip (Rockcrawl and StickyPony) - not sure who or what Ed Park's does when he does the conversions.

Thanks Fieroguru, but that won't help me unless I dump the caddy ecm and go with a 7730 which isn't likely to happen any time soon. Although it would be worth is to dump the caddy throttlebody and troublesome ISC.

quote Originally posted by jscott1: My chip did get reburned but evidently the PPM did not change. I can't believe the sail on condition could be so bad in a production vehicle. There has to be a way to make it better. I'm tempted to put a toggle switch to manually control the ISC.

It has to have something to do with a auto tranny - I have thought about a switch thingy as well, but my method was to turn off the VSS when out of gear (I coast a lot) - it should go to idle when it see's no VSS (haven't tried it yet). Currently I have stopped thinking about it as it is not extremely annoying at the moment (and I'm tired of fiddling with the car).

quote Originally posted by Mickey_Moose: It has to have something to do with a auto tranny - I have thought about a switch thingy as well, but my method was to turn off the VSS when out of gear (I coast a lot) - it should go to idle when it see's no VSS (haven't tried it yet). Currently I have stopped thinking about it as it is not extremely annoying at the moment (and I'm tired of fiddling with the car).

It seems pretty annoying to me, I'm trying to figure out a solution. The great minds on this forum certainly should have a solution? Turning off the VSS should work, but it would have the side affect of turning off the speedometer, unless you rigged up a second VSS on an axle just for the speedometer.

Maybe you could rig the VSS switch to the clutch so that as soon as you press the clutch the ISC would return to idle?

quote Originally posted by jscott1: I can't believe the sail on condition could be so bad in a production vehicle. There has to be a way to make it better. I'm tempted to put a toggle switch to manually control the ISC.

The 4.9/2240 is the worst I've ever experienced. If you put the car in nuetral at idle and coast down a hill, the engine speed will increase considerably as the car goes faster. It really is annoying. You can try hooking up a clutch switch to the range switch inputs to make it think it's in park when the clutch is down. I'm not sure it will make a difference, but it may be worth a try. Or just hardwire it to Park and see if it makes a difference. It's been a while since I've worked on a 4.9.

Jon

quote Originally posted by FieroAddiction: You can try hooking up a clutch switch to the range switch inputs to make it think it's in park when the clutch is down. I'm not sure it will make a difference, but it may be worth a try. Or just hardwire it to Park and see if it makes a difference. It's been a while since I've worked on a 4.9. Jon

Thanks Jon...it's good to hear from one of the great minds.

I was thinking about trying both your suggestions to see if that works. I'm going to see about an axle based VSS to run the speedometer/cruise and that will give me more lattitude to play with the signal going to the ECM.

The other option is to dump the 2240 and convert to a 7730 but that's above my paygrade.

quote Originally posted by jscott1: Thanks Jon...it's good to hear from one of the great minds. I was thinking about trying both your suggestions to see if that works. I'm going to see about an axle based VSS to run the speedometer/cruise and that will give me more lattitude to play with the signal going to the ECM. The other option is to dump the 2240 and convert to a 7730 but that's above my paygrade.

...just to save you some work on installing and additional sensor, just run your speedo off the VSS sender directly and t off the feeds for the ECM. You can then install a switch inline with the yellow wire to the ECM to shut off the input to the ECM (which should drop the idle down). Of couse, this method becomes an issue with your 6 speed and you will need to install a converter box in between.

Jon >> welcome back

I got my sail-on down a bit by adjusting the TPS and ISC a bit more then factory spec. Idle stays around 1250 until basically stopped. Then drops to 800. I tried to adjust it lower since the car would idle lower and doesn't have AC to put any extra load on the engine. The result was the ISC could barely keep the engine from stalling when the clutch was pushed in. RPM's just drop too fast on the 4.9 for it to work like I wanted it to. Might be worth trying out though.

quote Originally posted by Mickey_Moose: ...just to save you some work on installing and additional sensor, just run your speedo off the VSS sender directly and t off the feeds for the ECM. You can then install a switch inline with the yellow wire to the ECM to shut off the input to the ECM (which should drop the idle down). Of couse, this method becomes an issue with your 6 speed and you will need to install a converter box in between. Jon >> welcome back

I thought about that, it would save me about $40 for the sensor, but I'm still going to need an additional SGI-5 to knock down the 60,000 ppm to 4,000 ppm for the speedometer as you say. Any savings is good, so I will try that first.

I think a switch on the clutch would definitely help, but I'm not too crazy about the low speed performance when I'm lugging along at 6+ mph and the engine is fighting me wanting to go faster. I think I will do as Fieroseverywhere suggests and try some off nominal tuning. I tried Jon's (Rockcrawl's) procedure to the letter and it didn't work for me.

I was going to create a new thread, but while searching and reading this, I think it would be best to bring this thread back to life.

I'm installing a G6 six speed with my 3800SC now. I haven't got to the VSS yet. I don't have tuning software myself, but maybe when I get it tuned I can have the pcm reprogrammed.

My questions- Does anyone know if the F40 vss will work with a PCM from a 98 GTP?

Has anyone found out another way to convert 60,000ppm to 4000 to drive the speedometer or PCM or both? I was thinking a TTL circuit and relay, should cost under $20 including shipping, but would be off by 6.25% and I don't know what the VSS output voltage is or the input voltage the speedometer is expecting. Lastly, I don't know if the relay I'm looking at can switch at 125hz. Is there a better way to do this?

(I estimated 125hz switching frequency by dividing 60,000ppm by 16 with a 4 bit TTL counter. This gives 3750ppm, which at 120mph I found to be 125hz. Correct me if I made a mistake.)

jscott1- hows your 6 speed doing today? What did you end up doing with the VSS?

[This message has been edited by zi_gravedigger (edited 02-09-2009).]

The PCM can be programmed to accept any PPM you want... And it will output it at the same type of signal that the automatic swap guys use.. I thought you PM'd me about this?

quote Originally posted by darkhorizon: The PCM can be programmed to accept any PPM you want... And it will output it at the same type of signal that the automatic swap guys use.. I thought you PM'd me about this?

Yes I did... I'm not sure how soon I'm going to be able to get together for a proper tune though. If I could throw a $15 circuit to keep the speedo within 5-10% for a month or two it'd be great. That's the main reason I'm still asking questions. Thanks for the answer though.

quote Originally posted by darkhorizon: The PCM can be programmed to accept any PPM you want... And it will output it at the same type of signal that the automatic swap guys use.. I thought you PM'd me about this?

With the 7730 ecm i'm using for my northstar i wasn't able to program a large enough value in to get the spedo working properly. I could program the value in but then the ecm wouldn't read the speed at all and wouldn't output anything.

quote Originally posted by zi_gravedigger: jscott1- hows your 6 speed doing today? What did you end up doing with the VSS?

I haven't messed with it lately...

the Caddy system is hard to adjust under nominal conditions, and even harder when all the correct inputs to the ECM are not present. I need to put a switch on the clutch and brake to simulate a park and neutral switch and put those inputs to the ECM which I believe will help it to learn the idle better. Now it's hardwired to be in drive all the time and I don't think that will set the idle properly.

The 3800 ECM is better supported in terms of tuning. My recommendation is to handle the VSS conversion in the software.

I will look at my software and see what the maximum value is that I can input... But if I cant go all the way up to 60k, then possibly we could just make a circuit to drop the PPM to 1/3 or 1/2.

Oh well, heres the answer....

http://www.grandprixforums....grand-prix-7111.html

The gtp guy did use the PCM to program 60k into it. I wouldnt do anything but set it up to drive via the PCM then.

Ahh yes, and remember to put a park switch in so we can put it in park to do a few tuning related things.

[This message has been edited by darkhorizon (edited 02-10-2009).]

For those having trouble with the SGI unit make sure your wires from the sensor are twisted together to reduce the possibility of electrical interference. I discovered this was a problem with my CPS sensor after glimpsing a wiring diagram for the 3.4L V6. I then realized that the wires for the fuel injectors are also twisted together, an important observation for those having made harnesses and ignored those technical modifications such as myself.

quote Originally posted by jscott1: Okay I have confirmed through test with my frequency generator that the F40 VSS is 60,000 ppm and I have also confirmed that my ECM (stock 16132240) is still expecting a 24,000 ppm signal, despite the fact that my chip was reprogrammed for a manual transmission. So I have two options... 1) try to have my chip reprogrammed to 60,000 ppm, (is this even possible?) or 2) Put the SGI in-line between the VSS and the ECM and hope that it's not so noisy that it creates a jumpy idle.

Actually I found a third option to improve idle quality... I unplugged the ISC. Not very elegant but so far I don't miss it. Maybe in a cold climate you need it, but in Houston, not so much.

Holy resurected thread Batman! Did you ever get the speedo to work properly?

For the VSS programming in the 2240 PCM... It doesn't seem to care which signal it gets up to the 24000. There really is no need to change anything there. I can't say for certain anything above 24000 but below doesn't matter.

quote Originally posted by jscott1: Just to clarify I wasn't able to follow the procedure exactly as at one point it states to put the car in "Park" and presently I have no way to do that.

In a fiero its not super important to follow to the letter. Having a manual transmission, idling in park doesn't matter. Thats just for auto and so the PCM can compensate for park and drive loads. As long as the min idle screw is set as low as possible with the engine still running, TPS is set to .55 volts while resting on min idle screw, and ISC screw is adjusted to be within the 1.15-1.2 TPS voltage range sail on will be reduced to as low as the coasting idle speed set in the PCM will let it. Without changing this coast idle speed in the PCM you can't go any lower. This speed shows as "desired idle" on my scanner (should be not desired ). The 4.9 has some unique querks doesn't it.

I'm considering trying out Jon's idea of wiring it into the clutch saftey switch and see if I can elminiate the coast idle while the clutch is in. Might work, might fail miserably. Who knows. I'm not entirely sure how at this point or even if tricking the PCM into thinking it in park will eliminate the coast idle at all. For the clutch switch one wire has +12v at all times, the other has nothing til the switch completes the circuit. I'm not sure that I can find a way for it to add a ground without some real creative wiring. You need a ground signal at two PCM pins to activate park. Since I don't have cruise I as considering adding and using a cruise clutch switch to do this. Wouldn't be a solution for those with cruise though.

Did you ever get an idea of your gas mileage with the F40?

[This message has been edited by Fieroseverywhere (edited 03-18-2010).]

quote Originally posted by Fieroseverywhere: Holy resurected thread Batman! Did you ever get the speedo to work properly? I'm considering trying out Jon's idea of wiring it into the clutch saftey switch and see if I can elminiate the coast idle while the clutch is in. Might work, might fail miserably. Who knows. I'm not entirely sure how at this point or even if tricking the PCM into thinking it in park will eliminate the coast idle at all. For the clutch switch one wire has +12v at all times, the other has nothing til the switch completes the circuit. I'm not sure that I can find a way for it to add a ground without some real creative wiring. You need a ground signal at two PCM pins to activate park. Since I don't have cruise I as considering adding and using a cruise clutch switch to do this. Wouldn't be a solution for those with cruise though. Did you ever get an idea of your gas mileage with the F40?

Yeah I resurrected my own thread as I had some PMs asking me about the VSS and I never did get my idle and VSS to work to my satisfaction.

I did add the park/drive switch and it seems to help a couple of times, but it seemed to lose it's effectiveness over time. The ISC just defeated every attempt to be controlled and I gave up and unplugged it.

The 60,000 ppm on the VSS is also a major headache. If I could get a chip that would read the signal that high it would help considerably. Because my speedo/odo are so flakey I can't get a good reading on fuel economy.

I think most of you have seen the electric circuit I have on my web page. I use the Dakota Digital and my chip is programed for 4000 pulses. I have worked with a programer to try and set the pulses to 60,000 (a couple times) but for some reason the program says it is there but the PCM does not like it. Up to now I have had no problems (I probably just cursed myself going to Daytona). I will keep working on it.

Jack

quote Originally posted by J Gunsett: I think most of you have seen the electric circuit I have on my web page. I use the Dakota Digital and my chip is programed for 4000 pulses. Jack

I probably have seen it, but could you please repost a link here? Thanks.

jscott1, here is the link.

http://www.frontiernet.net/~jgunsett/6speed.html

Jack

quote Originally posted by J Gunsett: jscott1, here is the link. Jack

Thanks.. Your install is what made me go ahead and have Archie do mine. But my car was an auto, so it was the first 4.9 Archie ever converted to a 6 speed from an auto and I haven't all the bugs worked out yet. I'm convinced it has something to do with the burn on the chip but I don't have the ability to tune it.