marsie

I recently had my cossie on the rolling road to try and sort a intermittant top end misfire. The fault was traced to the wastegate actuator. The previous owner had obviously fiddled as it was adjusted so it was holding the wastegate open slightly causing a rattle on over run as well as very slow pressure build up and then no top end boost control (had it well off the 1.5 bar boost gauge!). So i ordered a brand new replacement from Motorsport Developments (was told i needed a -31 actuator)

Finally fitted it today and was told to put half a hole of preload on the adjuster rod to start with. Took it for a test drive and was as flat as a fart and only getting 0.2-0.4 bar of boost. So i shortened the rod pretty much as far as i could and went for another run, this time a bit better but still only getting a max of about 0.6-0.7 bar. Just for a quick test i disconnected the hose from the actuator and was back to square one- off the clock boost, crazy power but misfire at top end so i think we are looking in the right place

Anyone any idea what i am doing wrong as there is no more adjustment left and its still way of the pace it was with the shagged wastegate. Want to get it something like before i go back to the rollers for a final setup

My cars spec is
1990 4x4
stage 3 remap
Turbotechnics t34
green injectors
pro alloy RS500 intercooler


Thanks in advance
Paul

Paul_RS

iTrader: (4)

What boost control are you using?

marsie

As far as i am aware its a standard amal valve?

Paul_RS

iTrader: (4)

Remove the amal valve from the boost circuit and connect the actuator directly to the compressor housing (with half a hole preload!) and you should have around 1 bar of boost.

If that works you know the fault is with the amal valve.

Guinnless

Half a hole (3-4mm of preload) should be fine. Don't leave the actuator wound up all the way as this will prevent the wastegate from opening properly leading to boost creep. Particularly if you forget all about it later on.

Might be worth checking the wastegate (not the actuator) is sealing properly. You'll need to remove the downpipe and check the wastegate 'penny' is undamaged.

Have you checked the Amal valve is working properly and has at least the standard 2.5mm jets in the C-Port and the R-port. The W-port should have no restrictor in it
When it's powered as it should be on tickover air should be able to flow from the C-port to the R-port.

Are all the signal pipes connected to the correct ports on the Amal valve? Compressor housing to the C-port, W-port to the wastegate and R-port to the airbox.

Is there a dump valve? Ensure that this isn't leaking boost away.

Whose chip is it? How have they advised that you set the boost up.

The misfire may be down to tired plugs/dizzy cap/rotor. Are all of these new and correctly set up? What spark plugs are they?

marsie

I know very little about the history of the car (hence my other posts) but will try the direct pipe bypassing the amal valve and half a hole preload as you suggest. The paperwork with the car suggests that most of the work was done by a company called Frankenstein Motorsport in Leighton Buzzard but that was back in 2005 and i cannot find any mention of them now??

Guinnless

OK I've seen your other posts now

Somebody else has already mentioned about checking the voltage at the fuel pump. Did you do this?
Unless its got a nice shiny fuel filter I replace that too while you're checking the fuel pump voltage.

Check the chip and see if it's from a current and reputable tuner (post pic on here if needed), if not get a replacement that's a known quantity so that you can use the correct fuel pressure, CO setting and boost pressure. Otherwise any setting up will be guess work.

Chips for Stage 3 and 803 injectors are pretty inexpensive.

marsie

Thanks for the advice guys. The problem was the dump valve. Replaced that and now everything is spot on . I can now put it up for sale
Thanks everyone
Paul