No Positive Boost...

[Sponge Bob]

Managed to fabricate an exhaust using a rev 3 system, and it's all running now - however, it doesn't seem massively quick and I don't seem to be getting any positive boost at all. I also seem to get far too much turbo vacuum on idle...

On start-up the boost guage reads right to the bottom of the scale (30 vacuum) which rises to about 10 vac as I rev... on driving it reaches 0 psi but never more... i've not booted it hard and have only tried up to third gear - but expect it to reach a few psi?

I don't hear any blow-off valve sounds - I know that it's a recirc bov but shouldn't you at least hear something slightly...

Why am I not getting any positive boost at all? What tests can I do?

edit - also, how do I check that the timing is correct on the dizzy - as I just put in in the middle and tightened the bolts up on the rebuild...

Thanks people :)

[Goldy]

Check all pipes are on I guess, tho sounds like a turbo problem as you've no boost. Not sure what you should check :hmm:

[Sponge Bob]

Don't say that mate!!! :cry:

[nickwebb]

try restting the ecu, you could be running in safe mode

[superchargedsam]

safe mode should allow at least 5psi boost !

[Paul Woods]

7psi... :)

right spongey! tests! im your peter pan.

first thing id do is check that boost gauge of yours is plumbed in correctly,just to establish its not telling porkies,it should be T'd in before the check valve on the MAP sensor vac feed.

When you know thats right the next thing is strobe up the ignition timing,no other way will do,so beg borrow steal one.Then bridge out TE1 and E1 in the diagnostic doo-da and check the timing is 10*

After that (presuming cam belt timing is correct etc) ,have you got a boost controller of any sort fitted? if you have then blank the pipe that comes from the turbo housing onto the actuatorand the pipe that comes from the actuator rearwards to the t-vsv,blank that off too.....this will test if the turbo is working (provided theres no boost leaks on the bov or IC piping/IC) .Take her up the road and you should be able to boost until fuel cut hits at 12psi...if it still doesnt make boost get back to us,theres tests for the IC system and BOV but get this lot out of the way first...that'll be a tenner :)

[Sponge Bob]

Right - first off, with the boost gauge T-piece does that mean it goes inbetween the VTV shaped thing and the manifold, or inbetween the VTV shaped thing and little black box... it's currently the former.

I don't have a timing light, so will have to get on the scrounge - I saw one for ?40 but that was an "advanced" one which I thought sounded like a con...

I'm not running any extra gubbins at the moment - it's all stock, so using ECU fuel cut, and the mechanical controllers... will add aftermarket parts once it's running ok stock.

Will tighten things up and see what happens...

Cheers :)

[Paul Woods]

if its the former your gauge is plumbed right...do the above tests matey and report back.

[Marksman]

Good luck Ash.

If you need a loan of any parts give me a shout as I might be able to help, depending on what it is... ...just happen to have a ct26 on the lounge floor for example...

O.S.

[Sponge Bob]

Cheers Owen - i'm going to get a timing light set up if I can get one today, but somehow I don't think that's the problem... will fault find as much as possible this week.

What I want to know is why the boost gauge reads 30 odd vacuum... if everything is less pressure does that mean that I must have a severe air-leak or something?

[Jiff Lemon]

Think I've still got my timing light here bob if you need it - Goldy will vouch for it being a good un ;)

[Sponge Bob]

Definitely mate... this eve good for ya? PM me

[nickwebb]

if youve hit fuel cut by hitting to much boost they the ecu wont let you go above 0psi

[Paul Woods]

ah yes nick thats true but it resets when you switch the ignition off and back on again

[podge]

mine doesnt ive gotta reset the ecu but doesnt this vary from rev to rev

[Sponge Bob]

well I've got a timing light thanks to Jeff, so will give that a buzz tonight and see hwat happens...

[MegatronUK]

Vacuum will read anywhere from -30 to -15 at idle.. so that bit is normal.

I had similar problems when my wastegate was staying open due to the actuator mount being in the wrong position = naff all boost.

[Sponge Bob]

Put new turbo on, and have fired up - seems to be excessive vacuum reading on idle - but will take for a run up the road later and see if getting boost...

One question - would a leaking Intercooler prevent any positive boost??

[wangan_x]

sounds to me like a line is on backwards mate... friend did that when installing a MBC and never could make boost.

[Sponge Bob]

I'm not running any boost controllers or fuel cuts at the mo - just getting it to run stock perfectly first...

Could you elaborate on a backwards line dude... I don't think there's much that could be reversed pipe wise.

[Jiff Lemon]

Put new turbo on, and have fired up - seems to be excessive vacuum reading on idle - but will take for a run up the road later and see if getting boost...

One question - would a leaking Intercooler prevent any positive boost??

Can you bypass the intercooler?

[nik]

you should still get some boost even with a leak..(to a certain extend..obviously if youve got a gaping hole (ooer matron) then you may lose all you pressure but itd have to be fairly substantial imho..
bypassing would work as a test but dont boost for long time..(love you long time..sorry..)

[wangan_x]

i meant a hose is probably hooked up incorrectly... even if you aren't running a MBC you may have accidentally hooked em up wrong

[Sponge Bob]

7psi... :)
After that (presuming cam belt timing is correct etc) ,have you got a boost controller of any sort fitted? if you have then blank the pipe that comes from the turbo housing onto the actuatorand the pipe that comes from the actuator rearwards to the t-vsv,blank that off too.....this will test if the turbo is working (provided theres no boost leaks on the bov or IC piping/IC) .Take her up the road and you should be able to boost until fuel cut hits at 12psi...if it still doesnt make boost get back to us,theres tests for the IC system and BOV but get this lot out of the way first...that'll be a tenner :)

I did this test at the weekend, and I'm still only getting a maximum of about 5-6 psi?? Does this mean that there is a turbo/BOV leak and if so how do I go about further tests / fixing?

Thanks matey - want to see that boost needle far higher up the scale!!

[MegatronUK]

This sounds scarily like the problems I had with my CT26A with the wastegate being held open... boost would take ages (comparatively) to build, and would max out at about 6psi. Check your actuator and mountings.

[Sponge Bob]

I've checked the actuator and it seems to be closed ok? It's not scraping the down-pipe, and it looks shut tight. The arm seems to work fine as well.

I've blanked off the pipes to the actuator, so in theory the VSV shouldn't get a signal - I've had the engine at standard operating temperature and still I don't seem to get anything above 6psi - is the ECU somehow preventing the boost going above 6?

[adamh]

the small u-shaped piece of pipe that connects from turbo to actuator.. this should be blocked from turbo. if its not it'l feed boost into the actuator.. and at 11psi the actuator will give way and bleed off the exhaust gas past the turbine wheel.

if the t-vsv is also connected, it opens to regulate manifold pressure? to 9/11psi, and the WG diaphragm spring to regulate the rest.

since the tvsv isn't connected and plugged, and both sides of the actuator are blocked, and the turbo housing is blocked off. I can only think actuator spring is weak and just holding open for some reason.

i m getting the feeling this small u-shaped pipe is still connected?

[adamh]

that's my understanding of it, confuzzling it is...

[adamh]

I'd guess in safe mode the tvsv just bleeds 4psi off constant. perhaps the tvsv is fooked ash and constantly open.
does that sound right or am I barking?

[Sponge Bob]

Well Ad there's nothing going onto the actuator at all - the pipes are blanked... so I guess that must mean there's a boost leak somewhere then - or the wastegate is slightly open (but I'm sure it isn't)

How do I test the BOV/IC/piping etc etc for leaks?

[Paul Woods]

ash run a pipe straight from your turbo outlet into the throttle body,no IC no BOV,nothing,just a straight pipe from turbo to TB,that will eliminate BOV and or IC or piping as the cause.

I personally think the wastegate must be open slightly....

[randomfactor]

Is the boost rising quickly to 6psi and holding steady at this value? That would seem like a system problem. Ash, have you got an MR2 cd for the correct sensor values?

Wouldn't a leak in the system cause the engine to overfuel? Any black smoke coming out? A friend's 850T5 had a slight split i a hose and the smoke was thick and black.

[Sponge Bob]

No smoke - I get a little white after not driving it for a while / startup but that's it. I'm getting a relatively clean 6psi when I accelerate - doesn't jerk or anything - what's an MR2 cd?

Paul, I'll recheck the wastegate - where do I get this elusive hose from - I tried fabbing something up at the weekend which would go straight from turbo to intake (I recall you mentioning this test previously) but nothing would work? What shall I use?

[adamh]

ash I have 51mm I.d silicon hose, about 2 feet of it in a straight, also solid 51 o.d stainless tube same again about 2 feet. I've also got a straight coupler about 75mm long with 63.5 I.d let me know if you can use any.

[Sponge Bob]

Adam, I've tried getting some solid pipe between the two, but the angles are too harsh to allow it to join at each end properly - if the silcon hose has enough flex or is the right distance to join the two then that would be quite useful to borrow - I would pay the P&P here and back naturally...

[adamh]

i'll check tonight if I get the time, if not it'l have to be tommorow as today is V day can't be too late mate or bobbit style will be me...

[randomfactor]

Ash - I have one of the Toyota workshop manuals on CD, it might help with testing and fault finding should you need to check the sensors. I have put it on my server if you want to download it:
http://guynet.homeip.net/openarea/

The password for the pdf is harvey

[Sponge Bob]

Thanks mate, I will have a look through those and see if anything crops up.