Boost issue on stock twins !!!

[shaunwil]

Tried to have a good read up and have had a quick look for any hard pipes or anything dislodged without much success.

The car boosts fine at 1bar in any gear then if i change up the boost only hits 0.2bar. Step off the throttle and give it a small time and then it boosts back to full pressure.

Does this mean i have a dodgy solenoid, sticky wastegate

Any advice would be greatly appreciated..

Shaun

[gmogle]

Yeah mate, dodgy solenoid. I had the same issue with mine, tested them all with a mityvac and found a couple to be dodgy !

Could also be a hose collapsing in the rats nest.

[shaunwil]

All the hose is pretty new, it was swapped about 11k ago and all looks in very good condition. Only iffy one was the one leading to the boost sensor :eek

Cheers, how do i test them ?? is the mityvac the hand held jobby for vac testing ??

Shaun

[arrouk]

does it drive correctly again after seeing vacum?. also if you keep accelerating up the revs does it spool eventially? and at what revs does it all happen.

matt

[gmogle]

Yeah mate thats right, bloody good piece of kit and worth the money !!

[Hayward North]

Yeah mate thats right, bloody good piece of kit and worth the money !!

ill second that, was the 1st thing i perchased when i decided to do the rats nest.
Been a godsend ever since, used it on bleeding brakes, clutch, testing valves and just about anything else i can think of

[m4drx]

the pressure chamber under the the strut brace (black box) holds a small amount of pressure so that it can activate solenoids and actuators quicker when you arent on boost so that you can boost more instantaneously this is probably your problem.

under it is a check valve (green and whitr plastic thing with an arrow on it) air should only go one way through so take it out and blow through it to check. this may be leaking or in two bits. there are also 3 more next to it on the right and one under the rear of the plenum check these also.

 there is also a vaccum chamber (another black box) which relates.

hth

[shaunwil]

Cheers, I had a look at the pressure chamber and couldn\'t see any leaks, might take it off and test if its holding a vacuum.

I\'ve re cable tied the check valve, but was struggling to get it off the pipe that disappears into the engine.

Will have another good look when it drys up.

Cheers Guys

Shaun

[shaunwil]

oops sorry the boost does slowly build back up and then kicks in.

Are the one-way valves easy to get hold of ?? Are they a mazda only part ?

Shaun

[m4drx]

i might have some valves about, they are £34 i think from mazda each, you can get some from the states but will take a little while. they can be checked by blowing through them onto salt etc. i advise checking them definately.

i do think under the plenum is not your problem as boost does kick in.

try looking above the turbo area. the y pipe in particular. The holse from the pressure chamber goes to the y pipe and the other hose goes next to the chamber below it.

i think your problem is either with the hoses that attach to your y pipe, Lower inlet manifold or the area at the front of the turbos ie below the airbox/filters - the hoses here go from the actuators on the turbos - from under the car you will see two rods attached they have a joint which has a circlip these also fall off as they are very fine and usually rusty.

i have fixed all my boost issues and (i had alot of them) and now done a few for friends. - my advice is start with the easiest of things, check everything thoroughly ie take hoses off if need be and check for cracks etc - i bought ebay rubber hose with a huge wall thickness but the heat made them close up inside but they still looked fine outside.

hope this helps,

give me a call if you need to.

[shaunwil]

Tested 2 of the valves with the blow test and they seem ok, need to dig a bit more to get to the others.

I\'ve ordered a mityvac off ebay and will try and do a proper check

Read an interesting post on rx7club about the higher boost setups screw up the contol solinoids and some people are now putting a pressure regulator into the system to reduce the pressure back to 9-10psi at the control bits.

Shaun

[probedb]

You can get viton check valves either from a guy on rx7club or on ebay...about $15 for 4 and far better quality than the OEM ones.

[shaunwil]

Yep, I did some digging online, when i had a connection ! and found this last night

http://www.coleparmer.co.uk/catalog/product_view.asp?sku=9855322

will probably order 4 and see if they are the cause.

Shaun

[adib]

hi shaun
what was the name off the place you got the mityvac from and how much was it thanks

[arrouk]

the ones from rx7 club work fine, and it sounds like the check valve to one of the chambers is fduked or the chamber leaks, ie not holding preasure/vacume.

sorry i cannot remember which would cause this. whats happening is after the change over the turbos arnt going none seq again.

matt