87 951 VEMS Install
01-07-2022, 11:23 AM
#691
Race Director
Mine runs great, no issues, had it running for a few years now...I did have to have it tuned to really dial it in which is pretty obvious but still worth repeating.
01-07-2022, 05:33 PM
#692
Hi HFB,
I had started looking into tdle settings but as this fault is intermittent i have disconnected & plugged the IAC to rule it out as a problem.
The base maps are tweaked also in the idle areas for t/s this prob also - timing at 12, ve´s 63 iirc.
It will idle great at 750 and warms up ok without the iac. Obviously gotta wind the tb idle screw out but it reaally is quite good when it starts well.
Ill keep your tips n mind when i reconnect it and tune it.
Thanks !
I had started looking into tdle settings but as this fault is intermittent i have disconnected & plugged the IAC to rule it out as a problem.
The base maps are tweaked also in the idle areas for t/s this prob also - timing at 12, ve´s 63 iirc.
It will idle great at 750 and warms up ok without the iac. Obviously gotta wind the tb idle screw out but it reaally is quite good when it starts well.
Ill keep your tips n mind when i reconnect it and tune it.
Thanks !
01-07-2022, 05:40 PM
#693
Hi KVDR,
Wasted Spark is really quite easy to do, see earlier posts, the coil can be had for the price of a dizzy cap, then its 2 wires to vems ec18-4 &10 for triggering, take the power from the stock coil and put a ground to the cyl head- You´ll also need new leads with correct coil connectors, i think Audi 200 5cyl or S5000 leads will work also.
Wasted Spark is really quite easy to do, see earlier posts, the coil can be had for the price of a dizzy cap, then its 2 wires to vems ec18-4 &10 for triggering, take the power from the stock coil and put a ground to the cyl head- You´ll also need new leads with correct coil connectors, i think Audi 200 5cyl or S5000 leads will work also.
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KVDR (01-07-2022)
01-09-2022, 03:38 AM
#694
Rennlist Member
Hello,
Happy New Year to everyone,
I´m hoping someone can help me with some inside knowledge of vems.
I have a V3.3 (bought from Peep as a pnp as i really didn´t want to be going into the nittygritty diy of ecu´s at the mo) installed on a Porsche 944 turbo. It starts, idles and runs great on a good start BUT on about 50% of starts it is BAD and has a light misfire (like a vac leak or weak spark), almost dies on accel (like a carb accel pump not working) and has `hard´ backfires on rapid decels (like a bad vac leak).
Once started in this state it will not recover unless restarted (ecu reset ?) and is immediately obvious by the popping sounds at idle in the exhaust.
At idle (800rpm) The 02 is approx .05 higher than a good start (i presume unburnt fuel?) and very unstable as are the rpms & 02 with tps held at 4%.
Turn it off & on again and it will run perfect - 02 @ 99 or wherever it is set, no misfire, backfire etc.
I´ve tried all external troubleshooting i can find & think of, and am now wondering if its possible for Vems to initialise and latch in a state that can cause these issues until the power is cycled.
I was running WS with new leads (from Peep), but for t/s have put the orig stock coil n cap/leads back in, tried 3 new ws coils, deactivated and plugged the IAC, 2 new sets of plugs (resistor & non), checked for vac leaks, swapped inj, ign Channels & pins, jiggled harness´s conned out connectors, checked tps sweep, disabled inj cha´s during idle but cant find anything wrong.
Trigger logs look good, timing strobe looks good steady n solid also.
Cylinder head recon & turbo were replaced at the same time as installing vems.
Next thing i´m going to try is reinstalling the Motronic ecu but i was hoping for some ideas before doing that.
Logs & Trigger files attached. (Maps are untested at this time & idle is setup for t/s this problem - Idle EGO/Timing control deactivated)
Any advice appreciated,
Thanks !
Happy New Year to everyone,
I´m hoping someone can help me with some inside knowledge of vems.
I have a V3.3 (bought from Peep as a pnp as i really didn´t want to be going into the nittygritty diy of ecu´s at the mo) installed on a Porsche 944 turbo. It starts, idles and runs great on a good start BUT on about 50% of starts it is BAD and has a light misfire (like a vac leak or weak spark), almost dies on accel (like a carb accel pump not working) and has `hard´ backfires on rapid decels (like a bad vac leak).
Once started in this state it will not recover unless restarted (ecu reset ?) and is immediately obvious by the popping sounds at idle in the exhaust.
At idle (800rpm) The 02 is approx .05 higher than a good start (i presume unburnt fuel?) and very unstable as are the rpms & 02 with tps held at 4%.
Turn it off & on again and it will run perfect - 02 @ 99 or wherever it is set, no misfire, backfire etc.
I´ve tried all external troubleshooting i can find & think of, and am now wondering if its possible for Vems to initialise and latch in a state that can cause these issues until the power is cycled.
I was running WS with new leads (from Peep), but for t/s have put the orig stock coil n cap/leads back in, tried 3 new ws coils, deactivated and plugged the IAC, 2 new sets of plugs (resistor & non), checked for vac leaks, swapped inj, ign Channels & pins, jiggled harness´s conned out connectors, checked tps sweep, disabled inj cha´s during idle but cant find anything wrong.
Trigger logs look good, timing strobe looks good steady n solid also.
Cylinder head recon & turbo were replaced at the same time as installing vems.
Next thing i´m going to try is reinstalling the Motronic ecu but i was hoping for some ideas before doing that.
Logs & Trigger files attached. (Maps are untested at this time & idle is setup for t/s this problem - Idle EGO/Timing control deactivated)
Any advice appreciated,
Thanks !
If you read this thread, shortyboy has the same issue. May want to pick his brain to combine your folks data and knowledge. I took his ecu and ran my pigtail and config, I could not replicate the issue on my car. I think we are the only two in Hawaii that have the PNP kit.
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Superfx (01-09-2022)
01-09-2022, 05:15 AM
#695
I've had mine for about 4-5 years, I fried my timing chip once, but after repairing it, it's been solid. As for tuning, I don't have an IAC, AC or winter cold starts so not much fiddling with starts in Hawaii. 
@shortyboy , that ECU Masters looks slick. Their site presents well, and they do pack in the features for a decent price. I'm doing some minor changes to the PNP pigtail to divorce myself from the old DME wiring, one thing at a time. At some point I might be able to swap out the oem speed and reference to a 32-1 and finally get wheel speed from a cv pulse generator I just ordered. I tried the early dash speedo hall that the mpg gauge used, too sketchy.
Maybe at some point I can consider cutting in a new ECU as well, I will give ECU Masters a good look. The frame still has your name on it, I'm slacking over here!
@shortyboy , that ECU Masters looks slick. Their site presents well, and they do pack in the features for a decent price. I'm doing some minor changes to the PNP pigtail to divorce myself from the old DME wiring, one thing at a time. At some point I might be able to swap out the oem speed and reference to a 32-1 and finally get wheel speed from a cv pulse generator I just ordered. I tried the early dash speedo hall that the mpg gauge used, too sketchy.
Maybe at some point I can consider cutting in a new ECU as well, I will give ECU Masters a good look. The frame still has your name on it, I'm slacking over here!
01-09-2022, 07:07 AM
#696
Hi Shorty,
Thanks for your input.
I thought the issues had been reolved...
Ive read the forum & vems support countless times now and have tried many different theories to isolate this problem....
I work away from home so have more time to read than trouble shoot but have got a bit done this week..
Yesterday i put the DME/KLR/AFM & Dizzy back in. I didnt plumb in the AFM but t was good enough to idle.
It idled high (due to large injectors) & hunted a bit (as it did on the DME) but not misfiring. Once adjusted it started and idled pretty well on just the idle screw.
On a Bad start the lambda hunts up about .05so i set it up on VEMS & WS, got a Good start and introduced a vac leak (thumb on the IAC port) to simulate a .05 lambda rise. When a true vac leak is occurring the idle rpm rises to about 1200 rpm - as you would expect, it´s also quite a large leak thats needed to do this so i´m sure there´s no intermittent vac leak causing this.
If its not lean due to air leak it could be inj not flowing enough, but i doubt that because my fuel pres & pw is consistent between starts, also (imo) not alot of fuel is reqd at idle and fuel timing is not critical at idle with batch fire - ive idled carb engines by pouring fuel into them with a cup without misfiring. so its most prob unburnt fuel causing the lambda oscillation...so its either real rich, which i doubt because allowing more air doesn´t stop the misfire (also (ime) idle between 98 & 1.05 doesnt usually result in misfiring).
So if its not lean or rich then its unburnt fuel pushing the lambda up - provided my lambda signal is reliable as thats also through vems..., prob due to spark - either weak or mistimed although the timing appears ok with a strobe light ie - not wandering or irregular.
I suspect it is missing the occasional timing pulse here and there from the VEMS chip Mega128A for some reason - .
(also ime idle timing between 8 -18 deg usually doesnt cause misfiring so even if it wanders a bit it still shouldn´t misfire)
I´m thinking it could be caused by the VEMS Chip reset power regulation network or some other some other control circuit for it but i don´t know enough about electronics or testing this type of circuit.
There´s a few threads about timing faults with these chips due to programming but i think if the external network component values drift far enough the internal chip timing will wander. I´m hoping to contact someone on the vems support forum who knows more about this.
See the Vems schem & Chip data sheet, highlighted where i´m referring to, attached.
Thanks for your input.
I thought the issues had been reolved...
Ive read the forum & vems support countless times now and have tried many different theories to isolate this problem....
I work away from home so have more time to read than trouble shoot but have got a bit done this week..
Yesterday i put the DME/KLR/AFM & Dizzy back in. I didnt plumb in the AFM but t was good enough to idle.
It idled high (due to large injectors) & hunted a bit (as it did on the DME) but not misfiring. Once adjusted it started and idled pretty well on just the idle screw.
On a Bad start the lambda hunts up about .05so i set it up on VEMS & WS, got a Good start and introduced a vac leak (thumb on the IAC port) to simulate a .05 lambda rise. When a true vac leak is occurring the idle rpm rises to about 1200 rpm - as you would expect, it´s also quite a large leak thats needed to do this so i´m sure there´s no intermittent vac leak causing this.
If its not lean due to air leak it could be inj not flowing enough, but i doubt that because my fuel pres & pw is consistent between starts, also (imo) not alot of fuel is reqd at idle and fuel timing is not critical at idle with batch fire - ive idled carb engines by pouring fuel into them with a cup without misfiring. so its most prob unburnt fuel causing the lambda oscillation...so its either real rich, which i doubt because allowing more air doesn´t stop the misfire (also (ime) idle between 98 & 1.05 doesnt usually result in misfiring).
So if its not lean or rich then its unburnt fuel pushing the lambda up - provided my lambda signal is reliable as thats also through vems..., prob due to spark - either weak or mistimed although the timing appears ok with a strobe light ie - not wandering or irregular.
I suspect it is missing the occasional timing pulse here and there from the VEMS chip Mega128A for some reason - .
(also ime idle timing between 8 -18 deg usually doesnt cause misfiring so even if it wanders a bit it still shouldn´t misfire)
I´m thinking it could be caused by the VEMS Chip reset power regulation network or some other some other control circuit for it but i don´t know enough about electronics or testing this type of circuit.
There´s a few threads about timing faults with these chips due to programming but i think if the external network component values drift far enough the internal chip timing will wander. I´m hoping to contact someone on the vems support forum who knows more about this.
See the Vems schem & Chip data sheet, highlighted where i´m referring to, attached.
01-09-2022, 08:16 AM
#697
Hi Shortboy,
Did you try MD´s config or vems on your car ? Its weird your unit ran ok on his car.
Do you have an immobiliser ? I have a factory immobiliser but i dont think that has anything to do with this fault.
The rest of my car is stock 1990 turbo.
Did you try MD´s config or vems on your car ? Its weird your unit ran ok on his car.
Do you have an immobiliser ? I have a factory immobiliser but i dont think that has anything to do with this fault.
The rest of my car is stock 1990 turbo.
01-09-2022, 03:16 PM
#698
01-09-2022, 03:21 PM
#699
Rennlist Member
I've had mine for about 4-5 years, I fried my timing chip once, but after repairing it, it's been solid. As for tuning, I don't have an IAC, AC or winter cold starts so not much fiddling with starts in Hawaii.
@shortyboy , that ECU Masters looks slick. Their site presents well, and they do pack in the features for a decent price. I'm doing some minor changes to the PNP pigtail to divorce myself from the old DME wiring, one thing at a time. At some point I might be able to swap out the oem speed and reference to a 32-1 and finally get wheel speed from a cv pulse generator I just ordered. I tried the early dash speedo hall that the mpg gauge used, too sketchy.
Maybe at some point I can consider cutting in a new ECU as well, I will give ECU Masters a good look. The frame still has your name on it, I'm slacking over here!
@shortyboy , that ECU Masters looks slick. Their site presents well, and they do pack in the features for a decent price. I'm doing some minor changes to the PNP pigtail to divorce myself from the old DME wiring, one thing at a time. At some point I might be able to swap out the oem speed and reference to a 32-1 and finally get wheel speed from a cv pulse generator I just ordered. I tried the early dash speedo hall that the mpg gauge used, too sketchy.
Maybe at some point I can consider cutting in a new ECU as well, I will give ECU Masters a good look. The frame still has your name on it, I'm slacking over here!
Hi Shorty,
Thanks for your input.
I thought the issues had been reolved...
Ive read the forum & vems support countless times now and have tried many different theories to isolate this problem....
I work away from home so have more time to read than trouble shoot but have got a bit done this week..
Yesterday i put the DME/KLR/AFM & Dizzy back in. I didnt plumb in the AFM but t was good enough to idle.
It idled high (due to large injectors) & hunted a bit (as it did on the DME) but not misfiring. Once adjusted it started and idled pretty well on just the idle screw.
On a Bad start the lambda hunts up about .05so i set it up on VEMS & WS, got a Good start and introduced a vac leak (thumb on the IAC port) to simulate a .05 lambda rise. When a true vac leak is occurring the idle rpm rises to about 1200 rpm - as you would expect, it´s also quite a large leak thats needed to do this so i´m sure there´s no intermittent vac leak causing this.
If its not lean due to air leak it could be inj not flowing enough, but i doubt that because my fuel pres & pw is consistent between starts, also (imo) not alot of fuel is reqd at idle and fuel timing is not critical at idle with batch fire - ive idled carb engines by pouring fuel into them with a cup without misfiring. so its most prob unburnt fuel causing the lambda oscillation...so its either real rich, which i doubt because allowing more air doesn´t stop the misfire (also (ime) idle between 98 & 1.05 doesnt usually result in misfiring).
So if its not lean or rich then its unburnt fuel pushing the lambda up - provided my lambda signal is reliable as thats also through vems..., prob due to spark - either weak or mistimed although the timing appears ok with a strobe light ie - not wandering or irregular.
I suspect it is missing the occasional timing pulse here and there from the VEMS chip Mega128A for some reason - .
(also ime idle timing between 8 -18 deg usually doesnt cause misfiring so even if it wanders a bit it still shouldn´t misfire)
I´m thinking it could be caused by the VEMS Chip reset power regulation network or some other some other control circuit for it but i don´t know enough about electronics or testing this type of circuit.
There´s a few threads about timing faults with these chips due to programming but i think if the external network component values drift far enough the internal chip timing will wander. I´m hoping to contact someone on the vems support forum who knows more about this.
See the Vems schem & Chip data sheet, highlighted where i´m referring to, attached.
Thanks for your input.
I thought the issues had been reolved...
Ive read the forum & vems support countless times now and have tried many different theories to isolate this problem....
I work away from home so have more time to read than trouble shoot but have got a bit done this week..
Yesterday i put the DME/KLR/AFM & Dizzy back in. I didnt plumb in the AFM but t was good enough to idle.
It idled high (due to large injectors) & hunted a bit (as it did on the DME) but not misfiring. Once adjusted it started and idled pretty well on just the idle screw.
On a Bad start the lambda hunts up about .05so i set it up on VEMS & WS, got a Good start and introduced a vac leak (thumb on the IAC port) to simulate a .05 lambda rise. When a true vac leak is occurring the idle rpm rises to about 1200 rpm - as you would expect, it´s also quite a large leak thats needed to do this so i´m sure there´s no intermittent vac leak causing this.
If its not lean due to air leak it could be inj not flowing enough, but i doubt that because my fuel pres & pw is consistent between starts, also (imo) not alot of fuel is reqd at idle and fuel timing is not critical at idle with batch fire - ive idled carb engines by pouring fuel into them with a cup without misfiring. so its most prob unburnt fuel causing the lambda oscillation...so its either real rich, which i doubt because allowing more air doesn´t stop the misfire (also (ime) idle between 98 & 1.05 doesnt usually result in misfiring).
So if its not lean or rich then its unburnt fuel pushing the lambda up - provided my lambda signal is reliable as thats also through vems..., prob due to spark - either weak or mistimed although the timing appears ok with a strobe light ie - not wandering or irregular.
I suspect it is missing the occasional timing pulse here and there from the VEMS chip Mega128A for some reason - .
(also ime idle timing between 8 -18 deg usually doesnt cause misfiring so even if it wanders a bit it still shouldn´t misfire)
I´m thinking it could be caused by the VEMS Chip reset power regulation network or some other some other control circuit for it but i don´t know enough about electronics or testing this type of circuit.
There´s a few threads about timing faults with these chips due to programming but i think if the external network component values drift far enough the internal chip timing will wander. I´m hoping to contact someone on the vems support forum who knows more about this.
See the Vems schem & Chip data sheet, highlighted where i´m referring to, attached.
when he tested my ecu he used his config as he has a supercharged 944. I dont have factory immobiliser.
01-09-2022, 10:31 PM
#701
[QUOTE=shortyboy;17894346]have you tried getting wheel speed from trans sensor?
heh my early trans does not have a sensor I'm aware of, but the turbo one "on the side does", although I want a solution that will work for both transaxles. The Type 2 cv joint pulse generator is from Moore Parts, 20+9 shipping. HAWAII I tell you.
heh my early trans does not have a sensor I'm aware of, but the turbo one "on the side does", although I want a solution that will work for both transaxles. The Type 2 cv joint pulse generator is from Moore Parts, 20+9 shipping. HAWAII I tell you.
01-10-2022, 01:49 AM
#702
Hi mdnt,
I missed your reply earlier...i was wondering if i could get the config that you used to test Shorty´s ECU as i don´t have a known config that has worked on my car.
I think yours should at least idle on mine without much issue. What supercharger did you use ? i thought i´d be putting vems on my mgb that i´ve supercharged witha m45 in blowthrough config by now...bu thats another story..
I missed your reply earlier...i was wondering if i could get the config that you used to test Shorty´s ECU as i don´t have a known config that has worked on my car.
I think yours should at least idle on mine without much issue. What supercharger did you use ? i thought i´d be putting vems on my mgb that i´ve supercharged witha m45 in blowthrough config by now...bu thats another story..
01-10-2022, 03:06 AM
#703
Look through the thread, there will be 2 others, so 4 of us total with this issue. Ive basically replaced every possible component to solve this and unfortunately, til this day still experiencing it. In the process of wiring the brand new 044 replacement to see if itll fix it as I believe I had a fake 044 in there previously. But after throwing thousands of $$$, just gonna swicth ECUs at this point ( picked up a Ecumasters EMU Black ). Also in the process of transfering all parts from my car to a rust free shell that Im prepping to get from @mdnt08 . Just trying to find time to do so during this pandemic. My guess on whats happening is the voltage is dropping below optimal, ive measured at VEMS ECU it drops to 10.8v and its either resetting the ecu or causing settings not to stick and timing is off, causing rough stars etc. Lots of great info on VEMS from some great individuals in this thread.
The ECU Master is a great product, i have the old ECU master classic in my 951.
01-10-2022, 08:47 PM
#704
Rennlist Member
01-16-2022, 03:38 AM
#705
Rennlist Member
So after installing the new replacement 044 fuel pump, same problem. Ive read online that some are having issues with VEMS processor chip, ATmega128. For those wondering, I've installed the VEMS ecu in 2018 and been trying to get it running properly ever since.Gonna start working on a jumper harness for my new ECU. Will start a new thread when the time comes.
Last edited by shortyboy; 01-16-2022 at 03:41 AM.