Da Booga

Hi,

I am having trouble understanding how the Apexi controls boost, my car is a Rover coupe turbo but no-one on the rover boards has been able to give me an answer so I thought I would try here. It should control boost the same no matter what car so...

I recently read the Apexi AVC-R instruction manual and am a little confused by one of the settings.

In the settings>>boost/duty section you can adjust the "duty cycle" of the solenoid (wastegate?).

I read this as saying that the solenoid is never fully open but opens for a set time every cycle (1 cycle = 40ms) i.e. a 50% duty cycle would mean that the solenoid would open for 20ms every 40ms.

If this is correct could anyone explain (in layman terms) how this method works and why this has to be set seperately from the boost levels? I would have thought the solenoid would open when the set boost level was reached to bleed off any excess boost and then close again when the boost dropped below the set amount.

Thanks,

Gareth.

UkLegacyT

i use this along with the s-afc on my car.

i will try to explain it in basic terms. basically, the boost solenoid lets a certain amount of air from the compressor to the actuator, with the amount of air depending on the boost level required.
if the solenoid opened for say 1 sec periods, the boost would be all over the place, so the solenoid 'flickers' if you like, at very short intervals (ms) to cope with fast feedback speeds and produce stable boost.

the duty is the time (ms) that the solenoid opens for during each 'flicker'.

you may find that the boost will be higher than the preset level at certain rpm, and therefore the duty can be altered to try and eliminate the problem.

example, you set boost at 1 bar. you drive the car and the boost is at 1bar, except that you have a boost spike to 1.2bar at say 4000rpm.
you go to the duty setting, and reduce the duty percentage at 4000rpm, say from 30% down to 25%.
drive car, boost is 1bar across rev range.

one thing you will find is that in the higher gears, due to the extra loading on the engine, the boost will naturally try to go higher than wanted. therefore, switch on the learn gear mode for all 5 gears, and the apexi will sort it out, although the duty may need adjustment too.

i found that apart from the wiring diagrams, its best to bin the instructions, as you would think you were programming a space shuttle.
just faff about with it yourself and it is easy when you get the hang of it.

hope this helps
ian

p.s. it does state in the book that it will not work with any other car than those listed, and the rover isnt, so you may encounter problems due to different voltage signals (i.e. from throttle position) and also when inputting vehicle settings etc.

BoxerFlat4

Just as an aside, these units can be fitted to non-listed cars, IF your prepared to install the correct sensors, or modify existing ones. Customer of mine has one on a Escort RS Turbo, and he's certainly happy with it !

Paul Houbart

UkLegacyT

oops, sorry, its the s-afc fuel controller that cant be fitted to the rover, not sure about the avc-r, but then again as mentioned above, nothing is impossible (within reason)

ian

Da Booga

Thanks, that helps.

Just to add their are many rover turbos about with the AVC-R installed and all sensors are available. I have the sensor required to allow the AVC-R to adjust the in gear boost but I have not fitted this yet.

UkLegacyT

cool, have fun mate.

ian