Hi guys,

 

I've lived with this 'problem' since putting the engine back in complete with new hybrid turbos. I removed all the extra boost control lines and solenoids to run boost control purely off the AVC-r. Problem is that even setting the AVC-r on max duty cycle I can only get to approx 1 bar before the wastegates open.

 

It has been suggested to me that the wastegate springs in the new turbos must be too weak to contain any more boost than this. I don't fully agree with this, I would expect the pressure in the exhaust system to keep the gates shut to some extent. Any observations on this? I've never heard of anyone else suffering from weak springs in this way.

 

 

My second thought is that the stock solenoids apparently bleed off some of the actuator line pressure, effectively causing a lower pressure at the actuator and further delaying opening. Even so, you would expect the EBC to be able to accommodate this within it's normal operating range with some adjustment.

 

I have gone as far as completely disconnecting the AVC-r solenoid and leaving the actuator control lines open to atmosphere - just to see if this allowed more pressure to build in the system, it only increased boost by approx 0.1 bar and seems to prove the theory of weak springs, also I guess it proves that a boost leak is not the issue as max boost would have remained the same.

 

I know that the actuators can only take positive pressure and negative can damage them but I'm wondering if there is some way to apply a little negative pressure, prehaps from the turbo inlet, to delay the wategate opening (?)

 

Sorry it's a long one. Hope someone can throw me a pearl or two of wisdom.

 

Cheers

 

H

its well known that the wastegates on oem turbos are fairly weak hence why most people tend uo upgrade them to hks items on uprated turbos, could be a sticky wastegate which is also common but i would imagine its as you have been told and weak springs

 

Mike

Assuming you have checked and defo do not have any boost leaks then you could have the common issue with the recirc valves leaking, this will not show on a conventional boost leak test as the air pressure stays within the system but just short cuts the front and back of the turbo, the fact you have tried it with the actuator lines disconnected does tend to confirm this, check out the link below should explain it a little more.

 

http://www.300zx.co.uk/forums/showthread.php?t=127063&highlight=recirc

 

Jeff TT

Thanks for the replies gentlemen.

 

The recircs went in the bin a long time ago Jeff, I've been running with Blitz BOVs since before swapping the tubs and didn't have this problem then, although I have completely removed the recircs now whereas they were previously blanked off...

 

With my setup as it is I've been unable to check for boost leaks by listening, still not sure where the pressure dissappears to. I've had to break the intake system down into sections and pressurize each one seperately, using inflation of a surgical glove as an indicator of pressure. Maybe there is a leak somewhere but I'm darned if I can find it.

 

Cheers

 

H

try reading up on here bud

http://thumper300zx.com/z32/tech.htm

stuff on boost leaks boost jets and EBC fitment

 

cheers and good luck

Yeah, thanks, that is a good link I'd actually found it earlier whilst doing some digging.

 

I'm convinced that the wastegate springs are the issue, problem is, can I change 'em without pulling the engine again!? Even if I could slide an extra spring over the actuator arm to add a little more tension it would do the trick. Dunno where to get a suitable spring though (any ideas?) nor whether this is a really dumb idea...

 

BTW, the old beast got through its MOT yesterday with just two rear tyre advisorys :D

 

Cheers

 

H

Yeah, thanks, that is a good link I'd actually found it earlier whilst doing some digging.

 

I'm convinced that the wastegate springs are the issue, problem is, can I change 'em without pulling the engine again!? Even if I could slide an extra spring over the actuator arm to add a little more tension it would do the trick. Dunno where to get a suitable spring though (any ideas?) nor whether this is a really dumb idea...

 

BTW, the old beast got through its MOT yesterday with just two rear tyre advisorys :D

 

Cheers

 

H

 

its been done before...fitting harder springs that is...bit fiddly but do-able...not sure the exact spring spec or pull you need....ideally an assorted box of springs would be best then cut and shape the size needed

Just a thought, I have no cat and basically straight through pipes, I'm wondering if the total lack of back pressure is making the wgates open early?

 

Cheers

 

H

did you solve this problem mate? Ive had my car on the rolling road recently and the boost tails off and i was told it was the actuator springs. Now i thought i could just get stiffer springs but then i was told that i neede uprated actuators aswell. I have the garrett gt2871 r/s turbos so thought they would have springs strong enough to hold the 18-20 psi they are rated at. But aparrently they just have 8psi springs in.

So can i just get uprated springs, or do i need the actuators, and where do i get these parts from.

cheers

danny

I wouldn't be too sure about it being the actuators, 8psi is the operating pressure but if you have a controller of some kind then the actuators won't be seeing anything like this - that's the whole point of a boost controller. My bet would be one or more boost leaks, even if you've checked, check again! I've found leaks I wouldn't even have thought possible since borrowing a compressor off a friend. The springs are integral to the actuators so you'd have to split them open to uprate them - more reliable and less messy to fit new actuators.

 

Cheers

H

i have a greedy profec eo1 boost controller fitted. And yes they are 8psi springs. Ive had 3 boost leak tests at three different places, myself and a compressor, phill nixon at blackmore service station, and jeff at Z world. And there are no leaks. But still the boost controller wont hold the boost. It will spike at 18 or so psi and then tail off as the revs climb.

Tried all kinds of settings with the gain etc and it makes no difference at all to the boost curve. So where can i get these uprated actuators, which ones do i need etc.

Or can it be something else. I have it on good authority that its the actuator springs though.

Cheers

danny

http://splparts.com/main4/parts/Z32/Turbo/Kits/default.htm

you can also go for the hks ones :)

 

http://www.hksusa.com/products/?id=665

 

Mike

Ah wonderfull. Now we're talking. Cheers guys, now just need to find a UK dealer.

many thanks

danny

Does seem a bit odd that your tubs didn't come with suitable actuators.

 

Good luck and do keep us informed how you get on. I still have lots of leaks to remedy before I can blame the actuators - but it may yet come to that... good luck replacing the drivers side!

 

Cheers

H