Cats, adaptive maps, lambdas and confusion!

[TT Tim]

Okey, today's installement...

... as anyone who's read my previous postings will know I've been having some problems with overheating cats as of late.

Wel, I plugged in the laptop and found that one lambda sensor didn't seem to be working, however there was no lambda fault showing on the fault log. So, today I've changed the offending lambda and also removed the cats, thanks to Tim @ ACT, I now have some very nice inline silencers to replace the cats, and very nice the car sounds too. But, back to the story...

I reset the adaptive maps after changing the lambda, and fired up the car and laptop, and blow me but 1357 lambda 1 is showing very low values, whilst 2468 lambda 2 is bouncing right up to 1.1v (approx). So I let the car idle for a while while I watched the adaptive map creep up on 1357 to the point that it's returned an AFR fault. I have tried changing the lambda over but still get the same reading. The odd thing is that the documentation with the Diag' software says that the MIL like should be lit if AFR = Bad, and mine wasn't. I know it's not a blown bulb as it illuminates on start up. I've taken this from the Help docs: When running correctly, the lambda voltages should switch between 0 & 1V (approx.). When under light load these voltages will stay predominantly lean (0V), with rich spikes (1V). So. Lambda 2 is doing what it should, whereas lambda 1 is reading low (lean).

So, what's happening?

A while ago i had cause to take the fuel rail off and clean the injectors, and noticed that they had different sized Venturi, at the time I wondered if there were a mixed set, and now I'm thinking that again, and wondering if they could be causing some confusion if they are different cc's.

I'm at a bit of a loss, so if anyone out there could offer up some suggestions or point me in the right direction I'd be very grateful.

As an aside, if it is injectors shouldn't it have shown up when it was last serviced, as that wasn't a lot more than 1000 miles ago?

BTW Here are the worst Adaptive figures for 1357:

Throttle: 1, Speed 750 = 37.5
Throttle: 2, Speed 1000 = 30.8
Throttle: 3, Speed 1750 = 36.4

and for comparrision Adaptives for 2468

Throttle: 1, Speed 750 = 17.8
Throttle: 2, Speed 1000 = 7.9
Throttle: 3, Speed 1750 = -2.6

Many thanks in advance

Tim

PS: Here's the link to my thread about injectors: www.pistonheads.com/gassing/topic.asp?h=0&f=6&t=218297

Here's a link to a log file to show what's happening: www.tjgraphics.co.uk/TVR/TEMP.RTL

>> Edited by TT Tim on Saturday 4th March 16:58

[GreenV8S]

You say you 'changed the lambda over', have you tried crossing the wires over? Because if the lambdas had been crossed over, one bank would go to full rich trim and the other would go to full lean trim. In that case, swapping them back would be the right answer.

[TT Tim]

No, I've physically moved the lambda from bank 1 to bank 2.

Tim

[trackcar]

Assuming the throttle pots are roughly the same around 16.9/17.3 ish then those figures just show a classic airflow inbalance across the two banks. decrease the airflow of the bank that's showing the higher positive corrections and then up the total airflow on the idle stop. job done (hopefully) then go back to your service agent and slap them across the head with a damp copy of the radio times (if it sorted it)

[TT Tim]

Thanks Jules,

I'm beginning to have a degree of 'sore head' over all this, can you please confirm that I need to adjust the air flow between L & R bank, using the link rod, as described in the service manual. i.e 'Measure the air flow... if one bank is different to the other, adjust the link rod by slackening the two locknuts from the ball socket and rotating the link rod. Then I need to reset the idle.

Now, this may seem like a very stupid question, but 1357 is on the LHS sitting in the driver's seat isn't it?

As for the service agent... hmmm, better not go into that on here.

Tim

[simonsparrow]

Glad I'm not the only one having similar problems.

My car has been playing up too. It first started a few weeks ago, when driving in town, suddenly the idle speed dropped to about 400 RPM and the car just felt sluggish on a steady throttle. Being keen I installed new coil packs, but that didn't fix it.

Then the bank 2 lambda packed up, so I installed a new one and all was well again......for a few days.

Then going into town again one night, same symptoms, low idle speed, running on a low number of cylinders at a steady speed etc. Acceleration seems ok, just steady speed.

So, out with the trusty laptop and I noticed that a low battery fault was reported. The battery seemed to have about 13.5 volts when the engine was running, so I think the altenator is ok. By connecting a booster battery across the original one, the car seemed much happier and idled normally.

So, new battery time. Installed and all was well.....for about 50-60 miles.

Driving into London today, the same symptoms returned (low idle, not running on all cylinders on a light throttle) just as I reached my destination.

They were still there when I left a few hours later, but after trundling along the A40 at about 2.5-3K revs for a few miles, all was well again. Car idling at a stead 1000rpm, running nicely under light throttle.

Then, as I pulled into a petrol station to fill up, back to low idle, missing cylinders etc.

Managed to get back home ok, but the car is still not running right.

A quick look with the laptop shows a battery fault logged (again) and the adaptives for bank 2 are as low as -30 at some points and as high as 33 at others. The odd bank has much lower values.

I've re-set the adaptives each time, and its worth noting that doing this does not fix the problem in itself, i.e. even with zero adaptive mapping, the idle is still low and eventually stalls.

Any ideas?

[darreni]

As jools said, it's the imbalance of airflow thats causing it.
you need to equalise the airflow on both banks (using the link rod), adjust the idle screw, set the pots & the reset the adaptive maps.

If you have any cerb mates that know how to do this, get them to show you.
There are so many variables on the set up it can be a real mindf**k.
Jools says he prefers to set the airflow by using the on screen maps, i could not get my head around this & found it easier to use a syncrometer (about £60 from demon tweeks).

Note that the link rod adjustments need to be tiny, quarter turns at the most.

I've found my syncrometer while clearing out the garage this afternoon, £30 posted if anyone wants one.

I found that quite a few of the dealers have no idea how to set up the AJP8 correctly as well!!

>> Edited by darreni on Saturday 4th March 18:38

[simonsparrow]

I think for Tim this is probably correct.

From what I've gleaned, the adaptive maps alter the base map by percentages to get the fuel that the engine thinks it needs (based on the lambda sensors output).

I would guess that the injector time shown is base map+adaptive adjustment.I'm guessing that setting the car up without an airflow meter involves getting the injector time in milli-seconds the same on both banks. As the amount of fuel injected is proportional to airflow, then equal injector time should mean equal airflow.

I think my problem is something different as its intermittant. Any idea how power is supplied to the ECU? I'm wondering is there is a connection to clean or something (as its reporting low battery when the battery is brand new and the alternator is putting out 13.4v)

[darreni]

Simon, mine always used to show a battery fault even when all was fine.
things that can affect the adaptives:

Airflow imbalance
pots
throttle spindle play
throttle linkage play
lambada's
coolant temp sensor
earths (lots of em)
Cats
coil
leads
plugs
water in wiring loom (early cars have a main loom joint under the coolant tank)

& probably loads of others

[trackcar]

on the ow battery front, it's important to know that the ecu doesn't register battery voltage, just the voltage supplied to the ecu .. so the battery could be perfectly ok but you might have a high resistance to the ecu . particularly at start up this can cause problems as below about 9.5 volts the ecu refuses to fire the injectors .. I've had to do quite a few cerbs with 30A relays to power the ecu up, ie use the existing 12v feed to power a relay which takes it's supply direct from the battery .. no more probs .. also saves chasing the real cause of the high resistance .. as long as you have enough to fire a relay you're ok!

[simonsparrow]

trackcar said:

on the ow battery front, it's important to know that the ecu doesn't register battery voltage, just the voltage supplied to the ecu .. so the battery could be perfectly ok but you might have a high resistance to the ecu . particularly at start up this can cause problems as below about 9.5 volts the ecu refuses to fire the injectors .. I've had to do quite a few cerbs with 30A relays to power the ecu up, ie use the existing 12v feed to power a relay which takes it's supply direct from the battery .. no more probs .. also saves chasing the real cause of the high resistance .. as long as you have enough to fire a relay you're ok!

Thats what I thought, as the ECU is reporting a lower value that 'seen' at the battery. Hence my question - how is power supplied to the ECU? Is it one of the pins on the big plug for the engine harness?

[TT Tim]

Which is the Purge Line, on teh fuel system, I'm looking at the service manual and the illustration is unreadable.

Many thanks

Tim

PS: Really fed up now, the bloody thing won't even start now I've taken the air boxes off. and the wife has started muttering 'bloody car' which isn't like here are all as she's as much of a Petrolhead as I am, it's looking like the Cerbera's days are numbered.

[darreni]

Tim, if it wont start, up the idle screw till it does (it will sound very rough) then adjust the link rod & pots.
I take it you have already been adjusting the throttle linkage & idle screw hence the no start?

As i said, the airflow balance is the key, with this set adjust the pots to 16.9/17.3/18.4 - normally anywhere between these will be ok to get you going. If anyone is near you with a syncrometer (some bikes use them to balance carbs) this will be quicker.

If you have been looking at the coils etc, make sure you have reconnected them correctly & all leads are on right.

[350matt]

You can also use some feeler gauges to set the throttle gap the same on both sides, not as good as a synhrometer but better than nothing

In order of attack I'd do the following:
Reset adaptives
Set throttle gap / airflow
adjust throttle pots

If you're still having trouble try disconnecting the lambda probes altogether, the car should start and run without them (albeit not very well) then ensure the even plug ( it should be labelled on the wire ) goes to the even bank ( again labelled on throttle pot wire) and re plug one at a time as Its not unknown for lambda sensors to fail in such a way the ECU doesn't reconise them as failed and tries to use the spurious output


Matt.

[TT Tim]

Thank you all for your help and words of wisdom.

Fingers crossed it all seems to be okay now, the air balance was wayyy off, I have a sync-meter. I was trying to remember the last time I used it and came to the conclusion it was setting up a pair of twin 40 Dell'Ortos on my Spitfire and that must have been 10 yrs ago!

The adaptives are now within tollerance, I think the worst is one blip to +23%, but within tollerance as I said. I no longer have an AFR fault, and the car seems to be running well, slight hesitancy lower revs but pulls like a train once it gets going.

It's popping and banging like mad on overrun, but that's due to the decat, the inline silencers make it a deeper exhaust note, sounds VERY purposeful

So, I'm sending off my form to North Weald and hop to make my sprinting debut later this month.

Thanks again.

Tim

[Mr Freefall]

TT Tim said:

Okey, today's installement... today I've changed the offending lambda and also removed the cats, thanks to Tim @ ACT, I now have some very nice inline silencers to replace the cats, and very nice the car sounds too. But, back to the story...

Tim, how much were the inline silencers to replace the catts? do they change the back pressure at all etc

Cheers

Mr F

[gazzab]

You can pay between £50 and £150 for decatt by-pass depending whether new, depending on supplier and depending if linked. They dont impact back pressure.

[TT Tim]

Mr Freefall said:

TT Tim said: Okey, today's installement... today I've changed the offending lambda and also removed the cats, thanks to Tim @ ACT, I now have some very nice inline silencers to replace the cats, and very nice the car sounds too. But, back to the story... Tim, how much were the inline silencers to replace the catts? do they change the back pressure at all etc Cheers Mr F

They were a bit more than normal decat pipes as there's obviously more work and materials involved, Tim said that he'd only had a few sets made up and in fact hadn't even started to market them, so best bet is to give him a ring: 0870 7070110

They do seem to have changed the exhaust note, and dropped the volume slightly, but they still 'come alive' on WOT! Over all I'm very pleased.

Tim