Cold Air Science

[Mortster]

Ive had by KN Typhoon on now for about 1 month with no problems, untill the other day.

The engine light came on after a little heavy foot action on a slip road onto the M25. CJ very kindly sorted it with his reader, running lean.

Reset it for me and all was fine. This morning, on the way to work, and the Hill up to Sevenoaks on the A21, under load, not even doing 80, it came on again.

Now the science bit...

It was fine when the weather was warm/hot. But now the temp has come down about 10o, Air is more dense when cold etc etc, so would that screw the MAF up?

I left the OEM ducting on, that feeds cold air from the bonnet, should I take this off? or Just go back to the factory set up?

[Scott.T]

check all your pipe to boost control and intercooler.
When you gunned it at first, maybe a hose has come loose.

Also check that the pipe to the fuel pressure regulator is connected and not split.
Quite common for these to go hard and crack.

We chased this fault for along time on Dukeboys car and it ended up being the pipe to the fuel pressure reg.

I should imagine the ECU is compensating and adjusting the fuelling to it's limits.
It could be a faulty lambda.

The ECU will auto compensate the AFR Learning.
When it hits the limit of adjustment it will throw the 'too lean' cell.
This AFR compensation uses the lambda and is only done at idle, cruise and light load, not when on boost.
The compensation required at idle/cruise/light load is then applied accross the map.

[Mortster]

Sorted, finally.

After having the engine light pop on constantly, checked all the Jube clips on the pipework etc etc, and after reading CJ and Worzles post about air leaks etc etc. Decided to have a real long check. Changed some of the vacuum pipes, then found this...




Ops...

Pipe was hard like toffee, and would just snap when touched. Replaced it with some red pipe ( of course ) took her for a quick blip, and slap me silly with a wet haddock!!! Problem gone.

I only really noticed the full extent of the issue at 2.30am zipping down the A21, gave it some beans ( normally spend my journey to and from work in light/heavy traffic so cant ) and it boosted to 15 psi, spluttered, juddered, then felt like it was braking.

I guess the heat from the Turbo has cooked the pipe over time?

Spot on