Superfx

The EC18-4 & 10 is recommended by Peep but i found it has been tried here

https://www.msextra.com/forums/viewt...art=20#p441411

and the info regarding the test fire igniting left over fuel is from vems support.

Is your vems flyback the standard circuit for lo & hi z injectors or is it modified for hi z only ?

I´m sure it is not ignition that has been causing my issues as i had the same fault when i ran it on the stock coil and also other ignition/ stepper triggering.

Troubleshooting with an oscilloscope (imo) shows the injector closing is not being controlled consistently, resulting in rich/lean mixtures being delivered.

I´m hoping to get my vems back in next week, pending Peep posting it, Hopefully my issues will be resolved with the Hi z flyback circuit mod.

I´ll let you know either way.

shortyboy

Yes please update the thread, could possibly solve many of us with similar issues. From what I gather I have standard fly back circuit from low and high z injectors. Much Appreciated.

Superfx

I´m not sure but i think this is the relevant page, although i haven´t got any confirmation of what config my vems or indedd what the standard vems actually is...
For a PnP i didn´t want to be knowing about this stuff !
http://www.vems.hu/wiki/index.php?pa...al%2FDDFlyback

Superfx

Package has arrived but i havent so suspense.for a few days...

Superfx

I´ve tried my modded Vems (Flyback circuit changed to control Hi Z injectors only) but still have the intermittent misfire issue....Injector waveforms look better but i´m still not happy with the pintle closing area...it doesn´t seem consistent. Anyone got experience with injector scope waveforms & Picoscope viewer ? For info:

http://www.volvotips.com/index.php/8...tern-tutorial/

It´s as if there´s intermittent resistance in the flyback circuit slowing up the voltage decay...but it all checks out ok...
I just received the Secondary ignition probe for my Oscilloscope (Spark plug lead or HT Wire) so had a look at that also...didn´t look great either so i´ve got a new set of leads on the way but i´m not convinced it´s leads as they were new also but i´ve had new bits fail often enough sooo......
Ign primary & triggering looks good, coil tests good & so do the other 2 new ones i´v tried...
I´m going to try to get some better traces as it´s not as easy as it seems to get good clean traces.
I want to compare injector pairs also which i havent done yet. A 2 Cha scope is a bit limiting but still a great thing !
Also, with a straight through 3in exhaust system testing is ltd to when the mrs is out !! No neighbour complaints yet....
If leads dont rectify it i´ll take the injectors out n have look for any contamination that might be messing with them closing.
The installed injectors are (& were) new Deka 850´s, supposedly original´s from FP in the UK. I will be very surprised if it´s injectors. It had new larger pump n new filter when it all went back together & has had this issue ever since..
Next thing i´m thinking is to separate the Vems power, ignition & Injector power circuits to try and reduce interreference.
I´ll scope the speed sensors also but they look good in trig logs so...
Any good ideas on how to access the underside of the central electric fuse box...mine lifts about 6in before its held by wiring, i dont really want to start messing with 30yr old wiring & plastic connectors in such a confined space.
Shortyboy, i cant remember if you said you replaced injectors...i seem to recall you did but cant check just now.
I´ll report further when i play more...

shortyboy

https://rennlist.com/forums/944-turb...l#post15952833
check this post for whats been replaced trying to fix my issues.

Dave W.

"Any good ideas on how to access the underside of the central electric fuse box...mine lifts about 6in before its held by wiring, i dont really want to start messing with 30yr old wiring & plastic connectors in such a confined space."

You can reach the underside of the fusebox through the interior of the car. Just look for a plastic cover above and to the left of the clutch pedal. Once you remove the cover you can reach the wires leading to the fuses and relays. It's not quite that easy tho.

Superfx

Hi Dave,
My rewire idea looked great on paper...and i have a 952 (RH Drive so no pedals there !)
I think it could make more trouble than its worth for the moment.
Shortyboy have you tried setting injector deadtimes ? I´m on the defaults and they look about 8x longer than the Deka 80 data that i have...

shortyboy

Ive changed it a few times but did not notice a difference.

T&T Racing

@shortboy that ECU Masters looks slick. Their site presents well, and they do pack in the features for a decent price
FWIW, I have been investigating standalone ECU's for a 944 race car with a 2.8L stroker engine
Option 1 is Microsquirt, I discovered an engine tuner in England who says all MegaSquirt variants are nice learning tools but he no longer tunes them.

Option 2 is DTA Fast T2 applicable for NA and Turbo. The engine tuner said to me, ""For a basic one to just run the engine and nothing more I'd use a DTA, because they are reliable, easy to configure, have good diagnostic functions and are super quick to map if you use a mapping box"
The mapping box let's you or the tuner do real-time tuning at any load/rpm with going into the VE and Timing Tables to change the bin valve with PC interface. Saves mucho time.
The link to understand the T2 ECU is
You can download the software here:
https://www.dtafast.co.uk/download_f...8139.20730.exe
The manual is part of the software, so press F1 on any page to open the manual.

The DTA T2 with the dyno tuning box is 3X the cost of the MicroSquirt equivalent. For my application, time is money. The engine tuner I would be using said to me that his best experience is with Holley but it is not applicable to Porsche 944/951 and he said MegaSquirt/MicroSquirt was more challenging for dyno tuning.

Superfx

Sorry for being so long with an update...I received my VEMS ECU back from Peep a few weeks ago but the Hi Z mod hasn´t fixed the popping issue.
The injector control looks to be much improved though.
I think my Oscilloscope HT probe isnt working well as i get some pretty strange waveforms...
I used Deadtimes from a motec Deka 80 table, gotta fine tune it later but it seems to like it better. Also found that min recommended pw for Deka 80´s is 1.7 but will got to 1.4.
I don´t think min pw is our prob yet though.
I´ve been having a good look at some vems logs and am thinking it maybe related to the MAP sensor somehow as my MAP readings seem to vary substantially between Good & Bad starts. (5 Kpa)
I was reading that the MAP sensor samples a baseline before engine start and uses it to calc the PW....
http://www.vems.hu/wiki/index.php?pa...dthCalculation
I´m gonna try using blended Alpha N at idle to take the MAP out of the calc and see what happens.
Gotta play some more next week. So frustrating as it runs great on a Good start.& ive got other projects that need time !

Superfx

Has anyone connected a 3 wire pressure sensor to Peeps Vems ?
I need a 0v Channel apparently but can´t find one and was wondering if anyone else has done this ?
I can´t believe its so complicated to connect a fuel pressure gauge.

four0four

Just doing some reading on VEMS (have my own sitting and waiting for the engine to be whole again...) and caught up with this thread. A few thoughts:

About the popping/starting issue (this is still present yes?): Have you captured a nice, long waveform of the AVR's reset and/or VCC lines on startup? Looking at the schematics the best way to do this is via the programming port on the pcb (jp3 / "jp spi"). This would pretty quickly answer that question...

About the pressure sensor: It's just ground, but it's probably specified that way so as to have you run a dedicated wire back to the ECU. Not uncommon for high impedance or noise sensitive sensors. Basically, just have its ground accompany the signal back to the measurement point. Does this help?

paganrj

Hi Guys!
Looks like this chat has been inactive for a few months so let's get it fired up!
I just installed my new VEMS last week and need some help with some issues that I have not been able to find from others here. I contacted Peep but apparently he is very busy and I will like to keep troubleshooting my issues. Car =1988 951 with minor modifications.
1-I get a warning "Safe Mode Active. Injector and ignition outputs disabled"
2-I get a lot of warnings and errors in the screen that follows the first warning
3-I can't calibrate the TPS. Initially, no matter how I changed the minimum or maximum the dial stayed at 255 when I press the accelerator pedal, didn't change. Yesterday, I was able to make it move but it goes backwards when I press the accelerator (80% to 0%)
4-I can't calibrate the WBO2, regardless the number I put on the calibration textbox it keeps jumping from 0 to 21.1% even with the calibration wizard.
Thanks for any input.

Droops83

I wish I had an exact answer for you, but I do remember reading something about a safe/security mode a while back. Perhaps you could Google search some of the VEMS forums? It is probably a setting in the tuner software.

EDIT: check these links to start, not 100% sure how to use the info, but here you go:

http://vems.hu/vt/help/v3/v3_ecu_calibration.html
http://www.vems.hu/wiki/index.php?page=SafetyMode

You need to solve this first, probably why none of the calibrations work.