VEMS Community Forum
Technical => Fuel Injection => Topic started by: multiplex on January 29, 2008, 10:28:28 pm
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wanted to see if anyone has had any experience with race logic traction control systems.
for those not familiar, it cuts engine power by dropping out fuel injectors until traction is regained.
i'm going to contact racelogic directly about this, but was wondering how VEMS hardware / configs could effect this (if at all)
I'm not exactly sure of the circuitry used in the racelogic box, but during install you cut the wires going to your injectors, and then splice the box inbetween. It then interrupts the signal
I have connectors to bypass the unit.
With the unit connected, my idle AFR goes up to around 1.25, where it is normal just under 1.
the car doesnt want to idle!
i can't see retuning as the solution, so was looking for other ideas
thanks.
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Can you measure a voltage drop across the control's connection?
What sort of flyback do you have?
Rob
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i have the daughter board for flyback.
i'll measure across the junction - good thought.
was gonna maybe hook my scope up too.
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Jorgen was thinking that the flyback voltage may be effected by the race logic, it may be that you can adjust the injector characteristics or replace the daughter board with the 30V TS Diode (and adjust the injector characteristics) to overcome this issue.
Rob
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i was able to scope an injector today
first plot is at idle, with racelogic jumpered out
(http://voytilla.com/gallery/albums/userpics/10003/normal_idle_no_traction.jpg)
This plot is reving the engine (since it won't idle), with the racelogic spliced in
(http://voytilla.com/gallery/albums/userpics/10003/normal_reving_traction.jpg)
definitely changing the flyback characteristics
any ideas here?
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You're getting a much better flyback voltage in the second instance. This means that your injectors are closing faster and consequently getting less fuel. The flyback difference is similar to that of fitting a 30V transient suppression diode, so in the first instance use the injector settings suggested for the TS diode:
Inj open time should be 0
Inj rampup_battfac must be 4080
Then its a case of tuning your Inj effective rampup value. Try steps of 250 to find the point where the engine starts to idle crisply, then steps of 50 to 25 until you find the cleanest point.
It will definately be worth getting a 30V TS diode in your flyback line.
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wow you guys are awesome. I would never have interpreted the graphs that way. So you are saying the flyback looks better with the traction control plugged in?
I have a diode here, that i've never installed. Will do that.
I plan to go to P&H here pretty shortly with low imp injectors. I wonder how that will effect everything.
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The flyback looks better with the traction control, no doubt they have a flyback system built-in so that the injectors can be cut without back EMF issues.
Try the settings changes first, then see if the diode makes any difference for you.
How are you going to use P&H? There is no need, one 6R8 resistor per channel and the TS diode is all that you need, I have several systems running like this faultlessly.
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thanks rob. i hope to get to try the settings tomorrow
i bought the resistors (at the same time as the diode), but then have been looking at the MS add on P&H board. Same one that sprocket (i think thats his name) installed.
resistors will work for sure, i just prefer the high tech solution (which usually gets me in trouble)
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It is pretty clear that our drive stages is not used when the Racelogic unit is connected, the Racelogic unit has internal drive stages that takes over all flyback and driving of the injectors.
You only notice a difference as you use an old flyback version that was only used for a fairly short time (but that was sold as an option for a long time in the webshop). Dealers has only used this type of flyback for odd applications as we know that it cause poor injector control.
You don't need to modify your flyback, it's not used for the injectors when the racelogic unit is connected. You can probably forget about the P&H board as well, the racelogic unit only monitor the ECU injector channels and then drive it's own injector outputs with the same PW.
However, if you want to be able to remove the Racelogic unit from the car it would be good to have the high voltage flyback as it will make the injector behavior similar to what you see with the Racelogic unit.
Jörgen Karlsson
Gothenburg, Sweden.
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made the recommended changes, and the car runs great. thanks guys!
traction control is pretty fun too ;D
yeah i think i will just run the low imp injectors with the resistors and diode. any idea on what devices are inside the racelogic box?
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I've no idea what Racelogic have in their traction control system, it does show that their flyback is nicely sorted.
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Just to follow up on some info left hanging here...
I talked to the maker of the Peak and Hold board, and he confirmed your thoughts on the traction box getting in the way.
I then contacted race logic, and they provided me this information - might be useful to someone down the road
Hi Jason,
What ohmage of injectors are you intending to use? Anything less than 4ohm and our box can't handle it I'm afraid.
The advice you've been given is correct - the peak and hold setup won't work with our unit either. And if you were to use resistors in line, you may well get the TC unit to work OK but you'd be negating the advantage of using low impedance injectors in the first place.
Essentially, if you want to use RLTC then you need to be using medium to high impedance injectors, with a standard saturation type signal. Traction isn't compatible with pulse-width modulation control-limiting the injector current, or peak and hold. However, if you've got ringback issues this can be dealt with by fitting a coil module.
Mike.
So it sounds like larger, high impedance injectors are in my future
Thanks everyone for their help on this.
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Does the racelogic box work by "simply" skipping injection events at the right time?
If so then what's to stop you using the racelogic box to trigger the launch control input of VEMS with the launch soft limiter set at 1500 RPM or so?
When traction control intervention is required, VEMS will cut the fuel for you - leaving you free to have whatever injector solution you want.
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This could probably work, but at that point it would be nice just to do everything in VEMS (hopefully one day, monitor wheel speed,etc)
The traction box has 3 or 4 levels of fuel cut that it moves through sequentially until it regains the amount of traction you have selected (in percentage, 20%, 15%, 10%, 5%, and 'wet' on my box - they offer a continuous option also). I've found 5% to work pretty nicely.
The first level might cut every 4th injector fire on one cyclinder. each level is definable, but from the factory it is set to increase the number of cuts each level. second level every 3rd, etc. They also rotate which cylinder is cut so you don't get cold spots.
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very interested in this as im fitting rltc to my Nissan S14a running vems, how does the vems handle the mixture leaning out when the rltc cuts injector pulse
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I wonder how hard would it be to implement this kind of traction control to VEMS? We have the capability of monitoring wheel speed (ok, just one but it's enough for 2wd cars.
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Doesn't VEMS support external TC with controll on boost?
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Just FYI for anyone trying to do this too, I have a 3.6 box and it looks like it has the same issue. With it plugged in, it barely idles, lambda swinging 1-1.25+. Bypassed it's fine.
I'm using the deadtime strategy and I'm using ID1000 injectors. I noticed my tuner must have messed with the deadtimes to make it work better. I put in the ones from the site and it's buttery smooth now. The 3.6 might be better but it's clear as day, the car idles much leaner with the racelogic box plugged in vs bypassed.
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Hello BigD,
Could please explain this (same) issue somewhat? What is plugged in and bypassed. Is it the RaceLogic Box? (I suppose so)
I have understood that the RL box when plugged in takes control of the injectors using the genboard opening value as a set up (and that its control circuit is different from genboard
Then the effective opening time of the injectors is probably changed compared to the one given by Genboard.
If, when RL box is plugged in, idle is leaner, this should mean that the effective opening time is shorter than with Genboard. So I am led to say that the Geanboard control is better done by Genboard and that the RL injector opening and closing are slower (sorry Rob ;) )
But nevermind, in any case I believe the injector dead times values have to be changed when using the RL box
Philippe
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Sorry if I was vague, was posting in a rush.
Yeah the RL box splices in series with the VEMS injector outputs. It doesn't actually open or close the injectors, it simply breaks the given circuit when it wants to misfire a cylinder during a loss of traction situation. So when idling, the RL box isn't doing anything actively.
The way these boxes are wired into the injectors is that you add a male and female connector inline, and the RL harness has a matching set for each end. So it's easy to eliminate the RL box from the circuit to see the effect. With the RL box plugged in but not doing anything, the car idles much leaner.
I think I follow your logic about this meaning that the injectors open/close slower but then I don't understand how the calculation works then, why would it go leaner if the injectors are slower, and then richen with a higher deadtime? As I understand it, the deadtime is basically like an extra area under the pulsewidth curve, sloped sides instead of a square pulse. To get the amount of fuel right, the shallower the slope, the more the ecu will reduce the pulsewidth, to keep the area as desired. So if the slope becomes shallower than what the ecu thinks, wouldn't that result in too much fuel?
Purely symptom wise, it seems to indicate that the injectors open and close faster - leaner = less fuel going in. So with the pulsewidth being the same in both cases, the only factor is the deadtime being lower. But instead, INCREASING the deadtime made the engine run right.
Maybe the lean values were actually incomplete/failed combustions from too much fuel
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Thanks for your explanation
When you say that with RL box plugged in, the box is not doing anything, I would refer to the plots given by Multiplex here above. So I understood that even when there is no traction control done but the RL box plugged in, at least the flyback circuit of the injectors is changed
(I do not know if the RL box directly command the injectors from its own gate when there is no traction control (doing nothing?), but I guess it does, this would be much easier then to control the opening when traction control is ordered)
The deadtime given to the genboard is be compensated by the algorithm. So, if I am not wrong, the greater this deadtime value, the greater the genboard pw is.
This is open loop, There is no adjustment done by the genboard to get the amount of fuel right, that is the shallower the effective slope, the ecu will not reduce the pulse width to keep the area as desired.
Hence if the flyback circuit allow a faster effective closing time of the injector (effective deadtime) then the mixture is richer, slower, leaner.
Philippe
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Interesting, I guess I just assumed that the deadtime is used to subtract from the PW. If it doesn't then this behavior makes complete sense.