The V8 Owners Forum -

My mate just had he westfield seight IVA'd today and it failed on hydrocarbons - which were about 4000. Fitted new plugs and it came down to 3000 - but still way over the 1200 limit. CO was down at .3 % (very low). Lambda was 1.6 iirc.

I assume that cam should work in that engine and shouldn't cause such high HC? Going to fit a megaquirt and wideband - but just wanted to make sure there's nothing fundamental i'm missing or overlooked.

Engine is 1990 3.9 v8, fully rebuilt by me, ported heads & manifold, RPI piper 285 cam. Standard Lucas hotwire ECU - which is from a range rover.

Do you want to try another ECU? - You would have to have a tame MOT tester or sniffer yourself

I have a 1990 unit in the GT40 and it gets me through emissions. On regular unleaded it is tight but on high octane stuff it sails through

Ian

Its for the IVA, so its got to be right.

Really just looking for confirmation that the Cam is OK for the emissions. I can start picking through the other items.

Basically, it's running weak at idle. A lambda of 1.6 translates into an A/F ratio of 23.5:1 - I'm surprised it runs at all. My RV8 factory setting is approx 14.1 :1 which would be 0.95 lambda.

I dunno the hotwire, but on the flapper changing to a non standard cam results in poor running somewhere in the range.

Mine also ran very week at idle at SVA
Changed tune resistor and also ECU (Original had been modified by John Eales)

It now works well and meets requirements

Last year it only passed at "fast idle" this year on high octane much better

Ian

Hi

I also believe the 285 cam is a lot milder and less duration then the radical JE102 cam that is in my engine

Ian

DaveEFI wrote:Basically, it's running weak at idle. A lambda of 1.6 translates into an A/F ratio of 23.5:1 - I'm surprised it runs at all. My RV8 factory setting is approx 14.1 :1 which would be 0.95 lambda.

I dunno the hotwire, but on the flapper changing to a non standard cam results in poor running somewhere in the range.

I agree that 1.6 is very lean, but the plugs are black and it smells very rich - which is the complete opposite.
I'm going to weld a lambda boss into the collector and take it from there.

Sounds a bit like charge robbing causing some kind of intermittent misfire condition to me.

The Piper cam is milder than the cam I have in mine that passes the catalyst test (just about without cats)

Eliot wrote:

DaveEFI wrote:Basically, it's running weak at idle. A lambda of 1.6 translates into an A/F ratio of 23.5:1 - I'm surprised it runs at all. My RV8 factory setting is approx 14.1 :1 which would be 0.95 lambda.

I dunno the hotwire, but on the flapper changing to a non standard cam results in poor running somewhere in the range.

I agree that 1.6 is very lean, but the plugs are black and it smells very rich - which is the complete opposite.
I'm going to weld a lambda boss into the collector and take it from there.

Not only does lambda 1.6 say it's lean, but low CO/high hydrocarbons confirms this. The CO should be approx 1-2%.

The condition of the plugs suggest more than one fault.

The high lambda could simply be an air leak in the exhaust. Or perhaps the engine is off a cylinder ? Similar effect.
Air getting pumped through along with unburnt fuel.

High lambda, high hydrocarbons. A wideband only tells part of the story. Pull all the plugs and check they are all getting a good solid spark.

And black plugs can mean a fuelling problem. But also an inadequate spark problem.

A cheapy Gunsons spark jumper style tool will let you check for a good spark.

I realise that a wideband only does part of the job - But if i find out why its lean or rich on the lambda, i'm hoping it may identify or lead me to the root problem.
All the plugs were equally sooty when i replaced them during the test. I do want to check the spark strength though.

Reset the ECU (Power off for 30 seconds)
Restart and immediatly run like you are running in a cam 2000 rpm till it is hot

It worked on mine and seems to clear the readings from the sensors etc

Are you running Lambda sensors? in 1990 there was not a requirement to do so (year of change). likewise there were engines - no sensors, sensors and sensors with cats. it all depends what yoyr ecu is looking at and what the tune resistor colour is

Ian

Only problem with a wideband. Is it only looks at one thing. And that can either mean lean, missfires, air leak etc etc.
But doesnt actually identify which one. So it could read very lean, yet is actually very rich. Although in this instance obviously CO doesnt indicate rich.
But could indicate missfires or just poor combustion.

And of course if the wideband is up the tailpipe, it's only measuring an average of all 8.

If you could split the exhausts to each bank, it might help pinpoint a problem on one bank at least.

Does this version of hotwire do any 'learning'? It would help to know the age.

stevieturbo wrote:If you could split the exhausts to each bank, it might help pinpoint a problem on one bank at least.

Its got side pipes - so during the IVA we tested both sides and got the same readings.
Will double check the tune resistor, as it was missing and I made a new one up. Original vehicle was never fitted with lambdas.