Kangaroo Griff
Discussion
red griff 500 said:
3.-The Kangaroo oscillates at about half a second frequency (i.e. each power surge occurs about every half a second).
(the lambda wiring does go over the top of the engine I think),
The oscillating signal was a possible cause Raw-sewedge considered but after he built the lambda measuring gauge, that we have both tested in both of our cars, it was ruled out, as the gauge didn't fluctuate with the frequency of the kangaroo-ing. Further investigations are planned though.
The lambda wiring on my car runs down the inside of the inner body under the air intake trunking on the passenger side and I.I.R.C. it does run across the engine for the drivers side. Electrical noise/interference, is something I have considered as being a possible cause.
What I find frustrating about the whole 'Kangaroo' issue, is that the cause could be something easy, simple and cheap to fix, as I am very reluctant at the moment, to throw money at an expensive dyno and re-map session that may not totally eliminate the symptoms. I am convinced though, that the cause is down to the closed loop part of the system, as I have swapped the tune resistors from cat to non-cat and this has cured the problem. The problem here is, which aspect cured it ?? The richer mixture due to the lambda's being ignored, or the fact that the lambda's being ignored, there was no oscillating/noise/interference effecting their input to the ECU.
At very low rpm and low throttle openings there is a very significant amount of exhaust gas recirculation during the overlap period. If one cylinder fires properly then the exhaust manifold fills with combustion gases which then get drawn back into the plenum during the overlap period of subsequent cylinders, so the next few cylinders get a combination of nice fresh charge plus varying amounts of exhaust gas. It's an inherently unstable situation, if the contamination gets bad enough to affect the following cylinders they will produce less combustion gases in the exhaust so less contamination for subsequent cylinders. You may notice sometimes that your engine hunts slightly at idle (even if the stepper is behaving perfectly, or you have no active idle control at all), and this is probably why. The amount will depend on the cam, it will generally be worse if you have a hairy cam.
Griffter, I think you may have mis-understood what I was saying, I was not referring to any oscillation due to the drive train, I was referring to an oscillation in a closed loop control system.
Wixer, what does I.I.R.C. mean?
It sounds as though we agree that it's most likely to be something to do with the closed loop system, and the logic you apply to your experiment where the pre-cat chip resolves the problem seems to support this theory. I wonder if it's possible to run your car with the cat chip, but somehow "fix" the feedback signal to the ECU with some electrical wizardry to make it constant? If the problem is still apparent, then you have ruled out the closed loop feedback and the problem must be down to the different fuelling. (perhaps it's what Green V8S says, although I don't understand how exhaust gases can get back into the Plenum?).If however the problem goes away, then you have eliminated the fuelling, and it must be something in the feedback loop that's causing the problem.
Wixer, what does I.I.R.C. mean?
It sounds as though we agree that it's most likely to be something to do with the closed loop system, and the logic you apply to your experiment where the pre-cat chip resolves the problem seems to support this theory. I wonder if it's possible to run your car with the cat chip, but somehow "fix" the feedback signal to the ECU with some electrical wizardry to make it constant? If the problem is still apparent, then you have ruled out the closed loop feedback and the problem must be down to the different fuelling. (perhaps it's what Green V8S says, although I don't understand how exhaust gases can get back into the Plenum?).If however the problem goes away, then you have eliminated the fuelling, and it must be something in the feedback loop that's causing the problem.
red griff 500 said:
Griffter, I think you may have mis-understood what I was saying, I was not referring to any oscillation due to the drive train, I was referring to an oscillation in a closed loop control system.
Wixer, what does I.I.R.C. mean?
It sounds as though we agree that it's most likely to be something to do with the closed loop system, and the logic you apply to your experiment where the pre-cat chip resolves the problem seems to support this theory. I wonder if it's possible to run your car with the cat chip, but somehow "fix" the feedback signal to the ECU with some electrical wizardry to make it constant? If the problem is still apparent, then you have ruled out the closed loop feedback and the problem must be down to the different fuelling. (perhaps it's what Green V8S says, although I don't understand how exhaust gases can get back into the Plenum?).If however the problem goes away, then you have eliminated the fuelling, and it must be something in the feedback loop that's causing the problem.
Red griff, I.I.R.C.= If I remember correctly.
Yes, I totally agree but I'm not that clever with electronics. I think V8S's is refering to the engine running cycle, i.e. cam timing, where gases in the exhaust manifold can be drawn back into the engine due to valve timing overlap.
red griff 500 said:
I don't understand how exhaust gases can get back into the Plenum?
At the end of the exhaust stroke, the inlet valve opens as the exhaust valve closes. There is a significant time (30 - 60 degrees) when both valves are open, effectively connecting the intake and exhaust systems together via the cylinder. Since the exhaust is at roughly atmospheric pressure, and the intake manifold is under a substantial depression at part throttle, there's a strong tendancy to suck exhaust gases back into the intake manifold. If you want to see evidence of this, take the intake pipe off the plenum, open the throttle and have a look at the back of the throttle plate. The upstream side should be nice and clean, the downstream side will probably be filthy black. Part of this dirt comes from the breather, but a substantial part also comes from exhaust gas recirculation.
Just to add my two pence, my Griff exhibits kangarooing symptoms through a very small rev range. A very minor increase in throttle (as small as you can make it) cures it instantly and then it will cruise happily on that increased throttle. For example, exactly 30mph in 4th will cause some kangarooing, 32mph in 4th is fine and 28mph in 4th is fine.
I suspect in my case, it is either the throttle position sensor or a small issue in the fuel-map that is causing the symptoms. HOWEVER, people appear to be trying to find a common solution. Given that this problem is likely caused by fuelling issues, I think we have to allow that there could be a number of different reasons for those fuelling issues.
I am saving for another session on the rolling road with Mark Adams, not because my car needs remapping but because it's the most effective way I've found to diagnose minor niggles such as this. Mark's posts on this thread are excellent but personally, I suspect it's easier for a brain surgeon to perform brain surgery than to explain the science to a layperson.
Ian A.
I suspect in my case, it is either the throttle position sensor or a small issue in the fuel-map that is causing the symptoms. HOWEVER, people appear to be trying to find a common solution. Given that this problem is likely caused by fuelling issues, I think we have to allow that there could be a number of different reasons for those fuelling issues.
I am saving for another session on the rolling road with Mark Adams, not because my car needs remapping but because it's the most effective way I've found to diagnose minor niggles such as this. Mark's posts on this thread are excellent but personally, I suspect it's easier for a brain surgeon to perform brain surgery than to explain the science to a layperson.
Ian A.
red griff 500 said:
I see now what you're saying V8S!
Wixer, what about removing your sensors from the exhaust and plugging the hole with an appropriate bolt, and strapping the sensors securely to the chassis or something to get a constant signal from the sensor?
Not sure what reading the lambdas would be getting in this situation, I would imagine they would see too much oxygen and then, either over richen the fueling or just throw up an error within the ECU. Someone else may provide a better answer.
An easier option would be to replace the Y piece with one without a cat and run the non-cat tune resistor.
Secondly, Raw-sewedge is looking into the MegaSquirt injection system. This is a DIY system that you can tune from a laptop and isn't very expensive. We are planning to build an engine rig and test it over the winter. If it's successful, then we may fit it to our cars.
wixer said:
Secondly, Raw-sewedge is looking into the MegaSquirt injection system. This is a DIY system that you can tune from a laptop and isn't very expensive. We are planning to build an engine rig and test it over the winter. If it's successful, then we may fit it to our cars.
Crikey, you blokes are live-wires. An engine rig eh! Sounds like a very interesting experiment - I'm sure that there are a few people who would be interested in the results! Good luck!
red griff 500 said:
Secondly, Raw-sewedge is looking into the MegaSquirt injection system. This is a DIY system that you can tune from a laptop and isn't very expensive. We are planning to build an engine rig and test it over the winter. If it's successful, then we may fit it to our cars.
Crikey, you blokes are live-wires. An engine rig eh! Sounds like a very interesting experiment - I'm sure that there are a few people who would be interested in the results! Good luck!
Thanks, we'll keep a record of everything that goes on incl photos. Dave has managed to bully someone into lending us a RV8 with 14CUX and we have access to a written off Griff chassis which will have it's front end cut off, for use as the rig. Between us we can probably source most of the stuff we need to get it all up and running but any donations of 14CUX parts would be welcome.
Phil,
Not fitted the regulator yet.
Both myself and wixer have had an engine build including new cam so the cam is out the question. It didn't do this this prior to the rebuild so it must be something. I am the test bed so I'll keep you informed.
New "non cat" resistor cured 85% of the problem so no idea. Not technical but thanks for all the responses.
On hols for a week now so post when back.
FFG
Not fitted the regulator yet.
Both myself and wixer have had an engine build including new cam so the cam is out the question. It didn't do this this prior to the rebuild so it must be something. I am the test bed so I'll keep you informed.
New "non cat" resistor cured 85% of the problem so no idea. Not technical but thanks for all the responses.
On hols for a week now so post when back.
FFG
I've just dug some info out that I got ages ago - it may help:
ECU connector pin 23 - OS (left bank) Oxygen sensor signal specification;(n.b. pin 24 is for right bank)
ignition key on (multiplug disconnected)= 0.4 to 0.5V
engine running, hot = 200 to 1000mV (switching)
throttle fully open = 0.5 to 1.0V
deceleration (fuel cut-off) = 0 to 0.5V
switching frequency = 1 sec intervals (approx)
I find the "switching" intriguing - some bright spark said earlier in the thread that the signal "should oscillate when it's working properly". I assume that the switching is controlled by the ECU and not the sensor? The fact that it's switching at approx 1 second intervals when the engine is hot means that the ECU has to deal with a switching feedback signal when it goes into closed loop mode.
Maybe some other parameter in the ECU is on it's limit of specification which then makes it difficult to cope with the switching signal - if this was true, then changing over to another ECU is likely to solve the problem - anyone done that yet?
Or maybe there's some electrical interference causing a spike on the lambda signal which is screwing up the switching timing in the ECU - it is easily possible to get 200mV, or even 1000mV coupled into a wire, especially when you've got massive voltages from the ignition in the immediate vicinity - I don't suppose that the ECU needs very much current so this is a feasible possible cause. Has anyone tried re-routing signal wires away from HT leads?
It's frustrating that we haven't yet got a solution or solutions to this problem - I guess I'm lucky that mine's only done it on one occasion, but I suppose it could happen again. It sounds like some of you boys have to live with this all the time?
ECU connector pin 23 - OS (left bank) Oxygen sensor signal specification;(n.b. pin 24 is for right bank)
ignition key on (multiplug disconnected)= 0.4 to 0.5V
engine running, hot = 200 to 1000mV (switching)
throttle fully open = 0.5 to 1.0V
deceleration (fuel cut-off) = 0 to 0.5V
switching frequency = 1 sec intervals (approx)
I find the "switching" intriguing - some bright spark said earlier in the thread that the signal "should oscillate when it's working properly". I assume that the switching is controlled by the ECU and not the sensor? The fact that it's switching at approx 1 second intervals when the engine is hot means that the ECU has to deal with a switching feedback signal when it goes into closed loop mode.
Maybe some other parameter in the ECU is on it's limit of specification which then makes it difficult to cope with the switching signal - if this was true, then changing over to another ECU is likely to solve the problem - anyone done that yet?
Or maybe there's some electrical interference causing a spike on the lambda signal which is screwing up the switching timing in the ECU - it is easily possible to get 200mV, or even 1000mV coupled into a wire, especially when you've got massive voltages from the ignition in the immediate vicinity - I don't suppose that the ECU needs very much current so this is a feasible possible cause. Has anyone tried re-routing signal wires away from HT leads?
It's frustrating that we haven't yet got a solution or solutions to this problem - I guess I'm lucky that mine's only done it on one occasion, but I suppose it could happen again. It sounds like some of you boys have to live with this all the time?
I have given this some thought and I'm currently driving with the ECU wedged down the side of my passenger seat. It seems to make no difference, the hunting is still there. This isn't to say that there is some interference being picked up elsewhere. It has been mentioned to me that using non standard plug leads can make a car hunt more but only in certain cases. Maybe a change of leads is enough to do it to some cars due, to differing leads giving differing interference ???....
The near side lambda cable runs very close to the plug leads along that bank, maybe it's worth a try at re-routing or shielding.
I will try an ECU out of a 4.3 Chim.
The near side lambda cable runs very close to the plug leads along that bank, maybe it's worth a try at re-routing or shielding.
I will try an ECU out of a 4.3 Chim.
red griff 500 said:
Secondly, Raw-sewedge is looking into the MegaSquirt injection system. This is a DIY system that you can tune from a laptop and isn't very expensive. We are planning to build an engine rig and test it over the winter. If it's successful, then we may fit it to our cars.
Crikey, you blokes are live-wires. An engine rig eh! Sounds like a very interesting experiment - I'm sure that there are a few people who would be interested in the results! Good luck!
I hope to have a MS system built into my v8s within the next three to four weeks. if it works out then i hope be in a position to offer MS systems fitted and mapped for about 500 pounds plus vat (target price assuming no unforeseen complications).
Seeing as this gets you mapped ignition also i think it could be a great way for owners to get power increases with mapped ignition at vastly reduced costs compared to accepted existing options.
I'll let you know how i get on.
Hi, first post here. Had same shunting on my 500 in jan then lambda sensor failed, fuel smoke (white) everywhere thought head gasket had gone it was that bad £30 of petrol in 25 miles.
The problem is that as far as i can tell the ecu will look at only one sensor and see a fault causing a reversion to get home mode for both banks so if one is out the ecu will richen up all injectors. Put 2 new lambdas on (old one had no resistance hence fail )cured fault.
However had smoke last week again and no power, one ignition lead went down causing unburnt fuel in zorst. lambda sensed this and went into get home mode again. For the price of 2 lambda sensors £65 each its less than petrol also got 3 mpg more round town.
The problem is that as far as i can tell the ecu will look at only one sensor and see a fault causing a reversion to get home mode for both banks so if one is out the ecu will richen up all injectors. Put 2 new lambdas on (old one had no resistance hence fail )cured fault.
However had smoke last week again and no power, one ignition lead went down causing unburnt fuel in zorst. lambda sensed this and went into get home mode again. For the price of 2 lambda sensors £65 each its less than petrol also got 3 mpg more round town.
I have been having exactly the same problems, shunting/kangarooing badly on light throttle at any speed, very frustratingly over the past month or so. having changed the ECU the problem has now completely gone. I knew it was the ECU because after putting the new one in, I went back to the old one and once it had reset itself the problems came back.
laz11 said:
I have been having exactly the same problems, shunting/kangarooing badly on light throttle at any speed, very frustratingly over the past month or so. having changed the ECU the problem has now completely gone. I knew it was the ECU because after putting the new one in, I went back to the old one and once it had reset itself the problems came back.
What chip's do you have in your ECU's ?? And did you try just swapping them over, rather than the ECU's ??
It's be interesting to find out whether it was the ECU causing the problem, or just the chip.
Since my latest "upgrades", i tried the ECU in non-cat tune again this morning. I loose all the pops and crackles but its smooth, very smooth ! Ever wish you had not started something ? If i could go back 3 months i would have £7k in my wallet. Iam sure it will all be put right in the end.
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