Turbo/dump valve fluctuating noise :/
Turbo Mini Forums

Hi all,

iv recently rebuilt a metro turbo engine for my mini and run it for about 200 miles so far, so still running in.
it been bored out slightly with omega +20 pistons, balanced flywheel/cranshaft, centre main strap, central oil pick up etc. i have the plenum modified to run intercooler and dump valve. i believe the turbo is standard, the guy i bought the engine of (4/5 years ago now) said he had it refurbished.

so far it seems to be running ok and il hopefully be taking it to a rolling road session when i get some time.

when it come of boost it makes a chattering noise which i thought was the turbo spooling down but im not 100% sure so was wondering if anyone new if this is normal or not? please see the link bellow for a video of the noise. Thanks for looking.
http://vid1085.photobucket.com/albums/j430...zpsiorydp2u.mp4

Thanks

Yastra

That sounds very much like compressor stall, meaning your dump valve is not dumping when it needs to. Is there a signal line fitted to the dump valve? If it's an adjustable one, has it been adjusted so that it can open up at all?

hi thanks for the reply. i did wonder if that was the issue as have read about that before.

yeah its got a single line to it, its a bailseys dump valve and i dont think its adjustable. i did get it second hand so maby its faulty?



you can just see it in the pic.

Thanks

Your dump valve isn't plumbed in correctly or the spring is too strong.

Where are you taking the vacuum feed from?

In the 13's at last!.. Just

All of the above plus Looking at the type of valve you may have gotten fuel onto the O-rings, they swell and the valve sticks

Yes i moved to the darkside

Instagram @jdm_brett

Yeah could be springs too hard or the ring/diaphrams split, should be able to see or test

hi all, the vacume is taken from between the carb and the manifold i think i took it from an outlet that was allready there.

il check the spring/seals. is there a recommened spring that i should be using? i could buy a brand new valve that way i know that it wont be an issue?

Thanks

I reckon you've taken it off the old dizzy advance take off. This is a fairly common mistake. You need to take it from either a spacer plate between carb and inlet or from the inlet itself.

In the 13's at last!.. Just

I have done this with my boost gauge and it shows boost but only shows vac with a bit of throttle, When throttle closed shows zero.

That fluttery noise is ace, if only it wasn't bad for the turbo :(

mine: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=570945

ok il check as im not 100% sure were i have taken it from if i have taken it from the dizzy advance would it cause this issue? by boost gauge fluctuates aswell when i let off the throttle as if the boost pressures going up and down

1275grimsby i like the noise aswell :)

This is mine. Bottom left is my boost gauge and top right is vac advance for dizzy.

mine: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=570945

Also yes, my boost gauge raises when throttle closed. I think its due to the takeoffs being the wrong side of the butterfly?

mine: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=570945

thanks for the pics, yeah i think mine is the same and iv taken my dump valve of the same pipe as the boost gauge with a t piece

Also make sure the hole is actually big enough and that the pipes are not weak or collapsing in on themselves shutting off the pipe... ive had that before! Also becareful when buying a new dump valve, get one that can come apart cos i brought a new one and it was way too strong and would part dump part flutter... ended up just buying loads of spare diaghrams and springs n used my old one

bottom left should be part throttle lean off (assume you have blocked the other end off) top right is indeed dizzy vacuum.

Best off taking DV, Boost Gauge from the manifold.

If something is worth doing, it's worth doing half of.

Thanks or the replys, the vac pipe i have are relativly small bore so i may try larger pipes to rule that out aswell thanks and il phone up forge etc see if they have a recomended valve.

John, i dont realy have much knowledge on carbs so i doubt its been blocked off were is the other end that needs to be blocked? so would it be best to have some outlets welded on the manifold?

Thanks

this is the take of i used for my valve and boost guage, i have silicone pipe for the vac now and thats before i had the plenum modded for the intercooler

That's the part throttle lean off connection.

Get them hooked up to your manifold instead.

If something is worth doing, it's worth doing half of.

Think thats your problem... that pipes just closing up under vacuum... thats what my old one did.. have a look at it when revving n i bet u see it suck itself shut

Edited by D4VE on 18th Nov, 2014.

Thanks for all the advice guys im probs not goin to have a chance to work on the mini for another week or so but when i do il update on what i find then hopefully this will help others in the future.

I am eventually going to fit one of these as its easier that drilling manifold etc
http://minispares.com/product/Classic/Fuel...ch/classic/carb spacer.aspx|Back to search

mine: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=570945

That prob still won't work. looks a bit puny. just drill and tap the manifold. the turbo one even has a nice convenient flat spot on top of it.

If something is worth doing, it's worth doing half of.

On my old one i had the spacer but went down to my local hydraulics place and he gave me a suitable replacement larger nipple

Shaunas has a spacer adapter for the DV, boost gauge and the megajolt all off the one takeoff and works perfectly.

somthing that can work well is to whip the bolt out that goes through the sevo take off and drill it and either solder/braze/weld a take off in or tap it and screww a take off in.

I would always use a dedicated take off for a dump valve,

also, the Bailey ones can stick if they get fuel/ oil in them as they are a piston with O rings, the o rings can get contaminated and expand.