3.6 Varioram emissions test.

[Tony Cocks]

Can anyone assist please ? Recently had my 1996 993 fitted with a 3.6 Varioram MOT tested. As usual, when carrying out the emissions test the tester found it almost impossible to achieve engine RPM of 1500-2000 to measure CO etc. . Instead , as soon as pressure is applied to the accelerator pedal, RPM increases from 900 to 2200.
Would anyone with the same engine care to try to achieve 1500-2000 RPM by light pressure on the accelerator and let me know the result please ?

 

[zwhitea]

Are you sure the MOT centre was using the correct Engine settings... We have just had ours done, and on the new computerised system it gave us loads of different options for both the car and even when we narrowed it down to a 1996 993 Carrera 4 Cab, we still had about 9 different engines to choose from... great system..?

For the emmissions our test station does a natural idle of between 450 and 1500 rpm for CO and a fast idle between 2500 and 3000 rpm...measuring CO, HC and Lambda... Our problem was the Lambda was only just in at 1.024 when the max allowed is 1.030... as for the CO our was 0.007 with the max allowed 0.2 and a HC of 3 with a max allowed of 200.

So I would say that a fast idle test of 1500 to 2000 is too low..

Hope this helps...

 

[dparslow]

ORIGINAL: Tony Cocks

Can anyone assist please ? Recently had my 1996 993 fitted with a 3.6 Varioram MOT tested. As usual, when carrying out the emissions test the tester found it almost impossible to achieve engine RPM of 1500-2000 to measure CO etc. . Instead , as soon as pressure is applied to the accelerator pedal, RPM increases from 900 to 2200.
Would anyone with the same engine care to try to achieve 1500-2000 RPM by light pressure on the accelerator and let me know the result please ?

Depending on engine code, fast idle speeds are 2500 - 2800rpm for the emission test. The 993 is difficult to keep the revs stable below 2000rpm, mine is the same.

 

[Tony Cocks]

Maurice, Took the ISV off after a struggle. Very dirty inside with what appeared to be soot. Cleaned the apertures out with brake cleaner and cotton buds. Used minute amount of washing up liquid to ease the hoses back on. Jubilee clips reversed by 180 degrees to assist access next time valve is removed.
Has made no difference to attaining 1500-2000 RPM, but see entry above from dparslow.
TC

 

[Shane Hodges]

Tony, my car is non varioram, but I have the same issue of holding revs - just can't do 1800 rpm.

The best reason I've been given is sensitivity of throttle pedal v engine power v flywheel v electronics. There is a lot of power going to a lightweight flywheel, so balancing all of this can be tricky. Seems plausible to me, but I thought the electronics could have sorted it out..