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Cosworth L8 & P8 Closed Loop Lambda Control Software for Weber L8 ECU's.

What exactly is “Cosworth closed loop lambda control software?”

Many of you will know that the Marelli system is Map sensor based and the map sensor’s role is to tell the ECU how much air the engine is using so that the ECU knows where to look for its fuel injector “on times” in the fuel map. If the map then says "open injectors for 2ms" that’s precisely what the ECU will do, even if that means lean running or bore wash the map based system cannot and does not change, because it quite simply is not intelligent enough to know any better, it just does as its told. The lambda control adds a 4th dimension to the existing system and helps to control the delivery of fuel dynamically.

The lambda sensors input to the ECU tells the ECU how much fuel is being used via exhaust gas monitoring. It’s a bit like having an MOT station CO machine built into your ECU and the ECU constantly reading from it and tweaking your mixture. If it’s rich it will reduce the injector duration itself, if it is lean it will increase the injector duration itself, and it will do this constantly, making many adjustments every second to keep the air fuel ratio maintained at our specified levels regardless of engine load and throttle input. Its job is simply ensuring the fuelling stays at the chemically correct ideal ratio of 14.7 parts air to 1 part fuel. This ratio is known as Lambda 1. This constant monitoring and adjustment cycle is called "Closed loop lambda control" and it is a very basic form of “Electronic intelligence” for the engine management system.

This type of closed loop system came into operation worldwide in early 1992 (Many countries had utilised it for over 10yrs at this point) with the introduction of catalysts to mainstream production cars. The catalyst requires the fuel mixture to be chemically correct at 14.7:1 AFR so it doesn't’t get poisoned and this is why the lambda sensor and closed loop operation was devised for domestic motoring applications. We have now refined this system for use with far larger injectors than originally intended by Ford or Marelli and then retrofitted the system into cars with management systems that were never originally equipped with it.

When will my Cosworth ECU run under Closed loop Lambda control?
These are the key conditions we decided upon for closed loop operation:
If the following parameters are met or exceeded, the ECU will revert to conventional mapping at all times.
1) Rapid throttle movements.
2) Throttle angle above 60%
3) Overrun conditions.
4) Boost pressure above 4psi.
5) Engine speed above 3800rpm.
6) Coolant temperature below 70deg C.

At all other times the fuelling will be under complete lambda control for best emissions and fuel economy.
So as you can see above, although our new lambda control feedback system will keep everything running fine and as economic as possible for you, regardless of engine wear or fuel used, once you are running hard, your ECU will revert back to 100% conventional mapping techniques and control methods just as they always did in days of old.

Is it worth having if I don't care about fuel economy?
This is a common question and I always advise the same. Yes.
Closed loop operation means you only burn the petrol required to make combustion perfect. This means less wastage which is good for the wallet, and less oil dilution with fuel which is good for your engine. It also lowers carbon deposits inside the engine dramatically. Why anyone would want to throw more fuel in their engine than it needs is beyond me.

What cars can be done?
Anything at all with a Level 8 or P8 Ecu. (Most our Cosworth P8 chips are closed loop as standard though)

High Quality Bosch Lambda Sensor = £60*
Installation of Lambda Boss into downpipe. £40
Wiring of Lambda, heaters & signal into Ecu. £50**
Hardware Encryption Key for ECU software. £100.

All that is then required is either an off the shelf closed loop Map for £150 (Up to 803s) or £250 inc Vat (400s, 403s or large Siemens) Or a Live mapping session at £500inc vat. (Advisable from 83lb Siemens upwards to 1600cc)

Independent Customer Feedback:
Here are some links to independent customers discussing our new closed loop mapping.

*   = Some cars from 1991 will already have the lambda sensor installed in the rear of the Turbocharger.
** = Some cars from 1990 will already have the wiring installed in the harness as standard.

Copyright © 2004 Stewart Sanderson