engine idling at a high RPM

[Phil Lamovie]

Hi John et al,

> An engine idling at a high RPM because it was tuned at sea level 
> but tested at 5000' ASL would be sent to the shop where the 
> engine would be adjusted to pass the tests at that altitude.

An engine that was idling at more than 1% above the factory
specification has one of the following problems.

1. Air leak inlet manifold
2. Stuck idle speed control device.
3. Dead ECU output to ISC
4. Idle air bleed open so far ISC closed fully can't compensate
5. ECU confused about idle set point or rpm reading error
6. Faulty water temp reading high (ECU mode overtemp)

It's very hard to achieve closed loop fuel control at idle if you
don't pre light the cat.

> The tests are done at idle while the O2 sensor is in closed 
> loop mode. A rich mixture at Full Torque RPM is never tested 
> for and most...


The certification test are conducted using chassis dynos with
inertia correction and continuos gas sampling with "bagging"
and post test analysis on a second by second and total mass
pollutants per vehicle mass per distance driven.

The car is first "soaked" at 24 deg C for 24 hours and then
positioned on the dyno. A techie drives the vehicle trying to 
keep a dot on a monitor between two snaky lines which are
a speed demand. An error of 1.5% in speed is an abort test 
and resoak. (big career no-no)

Total driving time for both city and highway test are 54
minutes for the "New York" test. This simulates 27 minutes of
really ugly stop start traffic with brief burst up to 92 km/hr.
Some of the braking requires two feet on the pedal ! Full throttle is
used for about 1/3 of lower powered vehicles and at some stages the
autos kick down a gear or two.

As it is speed dependent big engine light cars do quite well until
the weight is factored in for grams/kg/km results.

The Highway cycle is not a pollution issue it is for economy
comparisons.

The 92 km/hr is the break point for "lean cruise". Most OEM's
choose 1.5 min above 95 km/hr and then drop out of closed loop
and head for Lambda 1.1 or 16.17:1 A/F ratio.

This gives best fuel economy and of course max. NOX production.
The cat goes out completely and won't be relit until you get off
the freeway. So your inter city trip could easily be 5% closed 
loop and the rest lean and dirty.

Puts the "Magic" of Closed Loop and the CAT into some real world
perspective.

Regards

Phil

Injec Racing