Ken Roberts
Supporter
I'm sure you gained a few horses too.
Vss-ecm-stalling
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Hey folks - bringing this one back up. I'm planning to use an aftermarket gauge that will pull speed from the GM ecu's speed output signal (CAN). I'll be running a ls376/525 with their controller kit.
From earlier in the thread it looks like Pete was able to get a VSS signal into the ECU using a Dakota digital GPS unit. However, actual speed was either too low (32 mph) or too high (70mph) when the DD unit was outputting a 60mph signal. Does anyone know what I have to do to get the DD and GM ECU to talk to each other so they agree on speed?
From earlier in the thread it looks like Pete was able to get a VSS signal into the ECU using a Dakota digital GPS unit. However, actual speed was either too low (32 mph) or too high (70mph) when the DD unit was outputting a 60mph signal. Does anyone know what I have to do to get the DD and GM ECU to talk to each other so they agree on speed?
John
If you haven’t read the blog on ABS Reluctor rings, it’s a kissing cousin to this stalling blog. Related.
If you haven’t read the blog on ABS Reluctor rings, it’s a kissing cousin to this stalling blog. Related.
Went for my first spin yesterday... stalling/bucking like crazy. All of you fellas have the newer engines, I've got the LS1 from a Vette and a 2000 Camaro ECU. I've gotta get some rest and re-read this entire thread tmw. Planning on going with the AIM MXD Stradda along with all of its sensors, but due to funds (or the lack there of I should say, lol) that's a few months down the road. I don't guess there's a rig/work around strictly for terrorizing my neighborhood purposes? I guess I'll play around with the Koso stuff later today and see if I can get it smoothed out before that bucking breaks something or my starter gives out 
Kenny - hit me up before you get too in love with the Aim unit. I’m running the MXS. There are some things you should know before you buy. The “full suite of sensors”’for the Aim system adds up very quickly and can get expensive - the Strada is a fairly basic unit to begin with. Unless you plan to make some dash mods the MXD may be too large to integrate well. You can print out a 1:1 drawing of the unit and check it for size.
Congrats on the first drive!!
Congrats on the first drive!!
Dito on Cam's comments on the AIM costs. I was used to using AIM karting so put one in a Corvette project car. AIM does not play well with other sensors so the price goes throught the roof real quick
I have a Racepack IQ3 in the SLC and am content with it and it fits the dash well. No logging in mine, but my ECU does that.
I have a Racepack IQ3 in the SLC and am content with it and it fits the dash well. No logging in mine, but my ECU does that.
I meant to get back to this thread to update with my experience. I’m taking a multi-front battle against this stalling issue. I finally have the car driving and idling more like an oem car, feels great not having to watch and listen to engine rpm on the chance I might have to hit the gas to coach the engine from dying.
I have the Dakota digital GPS signal feeding my VSS. I drove the car around with just the VSS signal being fed for a short period during go-kart and pre-tune. The car would want to die from time to time but it wasn’t obnoxious.
I had the car tuned and idle quality improved noticeably. It would still die from time to time but it definitely improved. The car was tuned a bit before the weather turned cold. Once the weather got cooler the idle quality seemed to fall back to where it was before. I got back into the routine of watching and listening for surge whenever I would come to a stop, stabbing the throttle and keeping rpm up whenever the lope seemed to get bad.
I then relocated my MAF sensor so it’s now about 6” from the throttle body. It had previously been at 10”. This seemed to make a night and day improvement. Since making this change my car hasn’t once gone back into the lopey idle/near stall condition. Feels oem.
Of all the photos I’ve taken of this project it turns out the engine bay is my least photographed area of the car! Here’s what I could find:
Original position - the MAF is about 1/3 to halfway between the 2 rear cross bars.
Relocated - it’s now almost in line with the forward cross bar.
Was it the MAF move, the Dakota digital, or the tuning? Or some combination of the above? I can’t say for sure. I did have an issue with my Dakota digital not too long ago and was too lazy to reset it so I did drive for a short period with no VSS signal but with the tune and MAF relocation in place; idle quality was very good. Of the 3 things I did I suspect the tune and MAF relocation had the biggest impact.
I have the Dakota digital GPS signal feeding my VSS. I drove the car around with just the VSS signal being fed for a short period during go-kart and pre-tune. The car would want to die from time to time but it wasn’t obnoxious.
I had the car tuned and idle quality improved noticeably. It would still die from time to time but it definitely improved. The car was tuned a bit before the weather turned cold. Once the weather got cooler the idle quality seemed to fall back to where it was before. I got back into the routine of watching and listening for surge whenever I would come to a stop, stabbing the throttle and keeping rpm up whenever the lope seemed to get bad.
I then relocated my MAF sensor so it’s now about 6” from the throttle body. It had previously been at 10”. This seemed to make a night and day improvement. Since making this change my car hasn’t once gone back into the lopey idle/near stall condition. Feels oem.
Of all the photos I’ve taken of this project it turns out the engine bay is my least photographed area of the car! Here’s what I could find:
Original position - the MAF is about 1/3 to halfway between the 2 rear cross bars.
Relocated - it’s now almost in line with the forward cross bar.
Was it the MAF move, the Dakota digital, or the tuning? Or some combination of the above? I can’t say for sure. I did have an issue with my Dakota digital not too long ago and was too lazy to reset it so I did drive for a short period with no VSS signal but with the tune and MAF relocation in place; idle quality was very good. Of the 3 things I did I suspect the tune and MAF relocation had the biggest impact.
Ian Anderson
Lifetime Supporter
I have had an EFI engine in the GT40 for as long as it has been on the road.
Always had bucking in the 1400 - 1900 rpm range on light throttle - like pottering through town
And always had stalling when coming to a stop.
System I use is a Range Rover "hotwire" system
Pretty robust and it has similar things like speed sensor is optional - basically it is not - it will run without one but it will stall.
The downside of this system is that if I fit the speed sensor it becomes a speed limiter too!
So coming up to lights - I blip the throttle an dip the clutch - immediately idles at the preset 800rpm and it does not stall.
And the bucking - the ECU in my case is the problem it refreshes around every 1.5 - 2 seconds. so light throttle - says too much fuel and turns the fuel off, then 1.5 seconds later says too little fuel and turns it back on - almost lifting front wheels off the ground.
So simple fix do not drive in the problem rev range and no bucking
So my answer is find the fault and learn to drive around them!
Ian
Always had bucking in the 1400 - 1900 rpm range on light throttle - like pottering through town
And always had stalling when coming to a stop.
System I use is a Range Rover "hotwire" system
Pretty robust and it has similar things like speed sensor is optional - basically it is not - it will run without one but it will stall.
The downside of this system is that if I fit the speed sensor it becomes a speed limiter too!
So coming up to lights - I blip the throttle an dip the clutch - immediately idles at the preset 800rpm and it does not stall.
And the bucking - the ECU in my case is the problem it refreshes around every 1.5 - 2 seconds. so light throttle - says too much fuel and turns the fuel off, then 1.5 seconds later says too little fuel and turns it back on - almost lifting front wheels off the ground.
So simple fix do not drive in the problem rev range and no bucking
So my answer is find the fault and learn to drive around them!
Ian
Good info Cam, thanks! From the reading I've been doing, I plan to go from cheap to expensive and will report back on this thread for each step. Even if the MAF relocation fixes my issue, I still will add the VSS/DD and of course a dyno tune is a necessity regardless. From what I've read, adding the VSS/DD will make it easier to tune.
This may help or not but here goes:
I'm running the LS3/480 with the GM hot cam. I also changed out my drop gear to the .903 set. In lieu of a dyno tune (which failed me three times with three tuners), I opted to use Allan's tuner Ed Gomez of Pro Edge Tuning (Wallingford, CT) and we street tuned it. I can go about 1400 RPM before I feel any cam surge. Street driving is actually not too bad at normal legal limits.
As for the VSS signal, I disconnected my DD system. I'm now using a Porsche reluctor wheel (see picture) and a sensor from a freight liner. I modified the heat shield as shown to mount the reluctor. The GPS speed signal (I used Speed Hut gauges....I like needles) to my speedometer and the ECU speed are within 1 mile an hour of each other. I connected the senor to the two VSS wires. As I recall it didn't matter on the hook up, but I cant find my notes to confirm.
The first pic is the data needed for the GM ECU. The second is the Porsche reluctor wheel mounted. I cut it in half then simply used the mounting bolts for the axle to secure it. The last is the final mount for the sensor. It all works.
I'm running the LS3/480 with the GM hot cam. I also changed out my drop gear to the .903 set. In lieu of a dyno tune (which failed me three times with three tuners), I opted to use Allan's tuner Ed Gomez of Pro Edge Tuning (Wallingford, CT) and we street tuned it. I can go about 1400 RPM before I feel any cam surge. Street driving is actually not too bad at normal legal limits.
As for the VSS signal, I disconnected my DD system. I'm now using a Porsche reluctor wheel (see picture) and a sensor from a freight liner. I modified the heat shield as shown to mount the reluctor. The GPS speed signal (I used Speed Hut gauges....I like needles) to my speedometer and the ECU speed are within 1 mile an hour of each other. I connected the senor to the two VSS wires. As I recall it didn't matter on the hook up, but I cant find my notes to confirm.
The first pic is the data needed for the GM ECU. The second is the Porsche reluctor wheel mounted. I cut it in half then simply used the mounting bolts for the axle to secure it. The last is the final mount for the sensor. It all works.
Before I order anything more, if I'm understanding this correctly there's 2 options...
A. Use the DD with GPS and let it feed the VSS directly
or
B. Use the DD without GPS, plus reluctor ring and a sensor to let it feed the VSS
I plan to do option B since I already ordered the reluctor ring from DSS. This will keep the VSS hardwired, plus don't have to have a 4th GPS antenna. What sensor is preferred?
A. Use the DD with GPS and let it feed the VSS directly
or
B. Use the DD without GPS, plus reluctor ring and a sensor to let it feed the VSS
I plan to do option B since I already ordered the reluctor ring from DSS. This will keep the VSS hardwired, plus don't have to have a 4th GPS antenna. What sensor is preferred?
Joel K
Supporter
Del, I am not 100% sure about this but based on my understanding if you go with a reluctor ring I believe you have to account for the right amount of pulses. To do that there are two solutions, DD makes a box to convert the number of input pulses to output pulses to match what the ECU expects. Or there is a field/variable in the ECU that a tuner can change to match up with whatever is coming off of the reluctor wheel.
I don’t have the ECU field or DD part number handy but can provide this info for you.
You're right, I left out the ECU field as well to fix it. While I have a buddy that is nice enough to stop by just to compare my tune versus a couple other 525 tunes. If they for some reason do differ, we'll buy credits and flash mine. I don't want to waste his time if I can work it out myself though, but definitely a possibility if I need to.
DD has 2 different parts, with and without GPS. Looks like both versions were used, but the non-GPS version which is $100 cheaper and since I am attempting to use the reluctor and sensor.
DD has 2 different parts, with and without GPS. Looks like both versions were used, but the non-GPS version which is $100 cheaper and since I am attempting to use the reluctor and sensor.
Del - did you get the GPS antenna for your AIM, or are you planning to use the VSS/reluctor combo for your speed output on your display?
If you have the AIM gps sensor then all you need to do for the VSS is feed it a signal whenever you’re moving, it doesn’t care about actual speed (I believe). Note that if you feed your AIM dash both a VSS AND have the Aim GPS module, it’s default is to display the higher of either reading. You would want to disable the CAN vehicle speed stream from entering the dash unit or ensure it’s lower than actual speed if you have their GPS sensor.
If you have the AIM gps sensor then all you need to do for the VSS is feed it a signal whenever you’re moving, it doesn’t care about actual speed (I believe). Note that if you feed your AIM dash both a VSS AND have the Aim GPS module, it’s default is to display the higher of either reading. You would want to disable the CAN vehicle speed stream from entering the dash unit or ensure it’s lower than actual speed if you have their GPS sensor.
I do have the GPS for the AIM. I am planning on the reluctor/sensor being a stand alone solely to feed the VSS so accuracy won't matter. I didn't consider about not needing the DD at all since it's only needed for accuracy.
I initially had the DD hooked to the VSS and ECU. The ECU wants to know the car is moving. We discovered the DD was not fast enough feeding the ECU at slow speeds. So we disconnected it to the ECU and went mechanical via a ring to feed the ECU. It’s a very simple process of data entry to the ECU if you have access to that specific data entry window. Since feeding the ECU reluctor data, we have not had any throttle or stall issues. I no longer use the DD.
Dan - really interesting observations. Subjectively my recollection is that the DD lagged behind the Aim GPS slightly in both acceleration from stop and deceleration to zero. My display, the proprietary gps sensor, and the DD all refresh at 10Hz but the DD seemed to be laggy or suffered from some filtering issues.
It’s great to hear your idle issues have been decked!
It’s great to hear your idle issues have been decked!
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