Kangaroo Griff

[griffter]

wixer said:

As your car only plays up when wet, have you checked all the lambda connectors ?? It wouldn't be the first time I've found a nice, green, furred up electrical connector on my car.

Or is the speed sensor getting wet?

[red griff 500]

Thanks guys, yes I have checked the connectors to the Lamba sensors and they're as clean as a clean thing. And the road speed sensor seems to be OK, I fitted a new one in January which solved some problems I was getting, and those symptoms are different to this.

The odd thing is, the car plays up after it's got wet whilst stationary i.e. after I've washed it or it's rained whilst on the drive. I don't seem to get the problems when I'm driving through rain.

Does anyone else's do this?

[wizardofoz]

Just a heads up to all of you guys with the Kangaroos, I was having the same problem with mine (500HC) it turned out to be the ECU rattling around on top of the battery, after moving it around a bit so it was wedged in sort of..... problem solved, it now drives like a Mundano diesel at light throttle .......another factory bodge to be sorted in the winter
Hope this helps!!!

OZ

[david beer]

I asked my engine builder if running the "non cat tune resistor" was dangerous, answer ? "nope,might give a few more BHP, but will fail the emmisions test" So i have a super smooth RV8 that may fail the MOT in 12 months time,if i dont flick the switch to "cat". 1000 rpm in any gear with no kangaroo.

[Mark Adams]

Hi David

Believe me I have seen vehicles catch fire because of fuel superheating the cats. What would your insurance company think if this happened?

From your past posts, it looks like you have a Griff 500. The TVR chip has a 3.9 Litre tune on the non-cat position, so this is what you are running on. Therefore you are making the car run severely weak on full throttle, as well as superheating the cats on cruise.

I would strongly urge everyone NEVER to do this - the consequences could be horrific. If there is a marked difference in behaviour between the two tunes, it means that the original tune does not suit the engine, or there is a fault which is simply being disguised.

[david beer]

Good to see a follow up, many times threads disappear without a conclusion. I will go back to "lumpy running". Hopefully i can get back to smooth without this "simple fix", its such a pain not being able to go below 2000 rpm. Having just spent so much dosh on the engine, i really want to enjoy it.

>> Edited by david beer on Sunday 11th September 19:42

[raw-sewedge]

Using a home made Lambda gauge which I got working today I notice when the shunting/stumbling occurs the mixture did tend to be lean.

All other areas of the fuel mapping did not really indicate any problems. I tested this on both Lambda sensors and neither showed significant difference.

This would seem to suggest that the problems are related to a lean mixture at neutral throttle and low revs.

Can anyone else confirm these findings?

I’m guessing that if this is the case on my car which is standard, then it will be more pronounced on a car that has been modified and has better volumetric efficiency?

[wixer]

I'm not sure I fully understand what you're saying here,

Mark Adams said:

fuel superheating the cats.

Wouldn't the cats just be at their normal operating temperature ?? and the fire risk would be due to more fuel actually getting through the engine onto them ?? But if more fuel did get through the engine, wouldn't it help cool the gases, therefore the cats ??

Mark Adams said:

The TVR chip has a 3.9 Litre tune on the non-cat position

Does this mean TVR only re-programmed one tune on the chip, the cat tune ?? and every other tune on the chip is standard LandRover ??

I'd be interested in knowing what your recommendations would be to get rid of the hunting symptoms, as you've only told people on here what NOT to do, as far as tune resistors go. Especially as the problem does seem to be quite wide spread.

[red griff 500]

I understood Marks reply to be that unburnt fuel enters the exhaust and then ignites within the exhaust/cat, thus overheating the cats. Is that correct Mark?

I second Wixers comment - Mark, do you have any suggestions as to the possible causes of the kangaroo behaviour?

[trackcar]

I suspect it probably needs the injectors cleaning or changing for bosch versions and a remap. Mark can do both these things for you, so might be worth contacting him to discuss the possible solutions? Whilst you're at it you might like to consider some sensible preventative measures like the ACT silicone intake pipes and some good HT leads. Again Mark will I'm sure be happy to advise on these points.

HTH.

[mongoose]

trackcar said:

I suspect it probably needs the injectors cleaning or changing for bosch versions and a remap. Mark can do both these things for you, so might be worth contacting him to discuss the possible solutions? Whilst you're at it you might like to consider some sensible preventative measures like the ACT silicone intake pipes and some good HT leads. Again Mark will I'm sure be happy to advise on these points. HTH.

[FlipFlopGriff]

I've got the problem and the injectors have been cleaned (month ago). Tune resistor changed and about 85% of the problem is cured. I'm getting a fuel pressure regulator fitted so will update when this is done. Suspect that it is running lean at low revs (correct Dave).
Jools - not sure if this problem requires the expenditure you suggest bit well done for pushing Mark's work.
FFG

[wixer]

I've just wired up a gauge (made by Raw-sewedge) to measure the lambda sensor output. The gauge tells whether it's lean, optimum or rich, with varying degrees in between. I drove the car with a white cat tune resistor and a green resistor. With the white resistor, the car seems to be very lean with the odd pulse to richer every couple of seconds during normal driving conditions and when the hunting is occuring. It's so lean, most of the time it doesn't register on the gauge.

With the green resistor, there is a definate richening, with the gauge reading from optimum to rich virtually all the time. Also, with the green resistor, the hunting is almost eliminated.

So my conclusions are from this little test, that the hunting seems to be caused by a too lean a mixture. Also, it would appear that it probably isn't a good idea to run a non-cat chip on a cat car.

The question now, is what to do about it.

[seasider]

wixer said:

Lots

I knew you would make more use than me

[trackcar]

It really surprises me that these RV8 cars have so many running problems. Mines got 101k miles on it and runs like a dream.

The Lucas ECU is so advanced it's taken the likes of Motec and Omex etc 20 years to make anything remotely as good. Plus the airflow meter is very clever in that it can actually compensate for engine wear (though how it does it i have no idea, i really ought to ask that question one day).

Assuming the pump/ regulator/ injectors are all flowing the same and the lambda sensors are in good newish condition and the ignition system is fine there shouldn't really be anything else to touch. ever.

So why so difficult to sort out? Surely if the car was OK once, the complex ecu ubersystem should be sorting it all out ...?

There are experts in this field, best let one of them take a look at it.

[GreenV8S]

Must confess I've never understood why an AFM based system ever has to be remapped; the AFM measures the mass of air coming in, the ECU adds the corresponding amount of fuel (plus transient enrichment and 'choke' when it is cold) et voila roughly the right air fuel ratio. Throw in closed loop feedback for fine tuning, and it should work on any angine you chuck at it. The only time I can see that you would need a remap is if you change the injectors or fuel pressure. Clearly it isn't this simple because different engines apparently need different maps, but can anyone explain why?

[wixer]

Quinny said:

So maybe this shunting issue is more to do with the cam than the ecu

Thought about this but eliminated the cam as the culprit, by swapping the tune resistor for a non-cat green one. This virtually eliminated the shunting, certainly to an everyday acceptable level. Doing this also cured FFG's shunting. So, definately not the cam.

[griffter]

wixer said:

Quinny said: So maybe this shunting issue is more to do with the cam than the ecu Thought about this but eliminated the cam as the culprit, by swapping the tune resistor for a non-cat green one. This virtually eliminated the shunting, certainly to an everyday acceptable level. Doing this also cured FFG's shunting. So, definately not the cam.

Unless the cam is worn and the tappet clearances compensate to a degree, effectively giving more valve open duration (as the cam profle is 'flatter'), and a leaner mixture? I'm only guessing, but it seems possible.

[griffter]

GreenV8S said:

Must confess I've never understood why an AFM based system ever has to be remapped; the AFM measures the mass of air coming in, the ECU adds the corresponding amount of fuel (plus transient enrichment and 'choke' when it is cold) et voila roughly the right air fuel ratio. Throw in closed loop feedback for fine tuning, and it should work on any angine you chuck at it. The only time I can see that you would need a remap is if you change the injectors or fuel pressure. Clearly it isn't this simple because different engines apparently need different maps, but can anyone explain why?

I think it's because the map is just that - a map, or a complicated look-up table. Instead of the ecu calculating the required fuelling, it looks it up. If the ecu calculated fuelling, presumably (in an ideal world of perfectly functioning componentry) it would always be calculated correctly assuming correctly sensed engine parameters - BUT it's not calculated, it's looked up. So the fuelling is only as good as the map, which in itself is a best guess for a finite range of parameter values and combinations. By altering engine chracteristics through e.g. induction work, the best guess might not be quite so good, as certain assumptions (e.g. inlet air flow speed/turbulence, fuel atomisation etc) might be less reliable, hence a different map is required based on new assumptions (or more likely a better guess).

Feedback e.g. from lamba sensors goes someway to addressing this, but presumably it just looks up a slightly different value in the map, or adds an extra signal to the looked-up fuelling, and so although more sophisticated, is still susceptible to the approximate 'best guess' syndrome.

Now carburettors - where the air flow inherently draws in the 'right' amount of fuel (assuming the carbs are correctly set) look kind of neat, don't they?...

[wixer]

griffter said:

wixer said: Quinny said: So maybe this shunting issue is more to do with the cam than the ecu Thought about this but eliminated the cam as the culprit, by swapping the tune resistor for a non-cat green one. This virtually eliminated the shunting, certainly to an everyday acceptable level. Doing this also cured FFG's shunting. So, definately not the cam. Unless the cam is worn and the tappet clearances compensate to a degree, effectively giving more valve open duration (as the cam profle is 'flatter'), and a leaner mixture? I'm only guessing, but it seems possible.

The engine's only done 1800 miles, so the cam's fine.

I think your next post explains it all. It's a basic system and isn't infinately variable. Therefore, the fueling needs adjusting.