Well, this is pretty much what\'s happening.
On accelleration, boost seems to try to jump past 1 bar before I even reach 2000 rpm. If I accellerate a little more steady, it will reach just over 0.8 but at 4500 rpm, it will drop to between 0.4 and 0.5 bar and won\'t go above that. I\'m guessing this could mean my second turbo isn\'t coming online???
Also, usually after a gear change, boost will stick at 0.3 until I let off the accelerator, then I am getting the "sonar/cow/siren/woooo" sound. I\'ve heard that this is the butterfly valve between the turbos sticking?
Basically, I\'m just looking for any suggestions on what I need to do to sort these problems out. So any help would be really appreciated. Especially considering my mate was (almost) keeping up with me in his Saxo VTR last night!!!:eek :2eek :mad:
Thanks! :Thumbs-up
Have a lookhere (http://www.autosportracetech.com/RX-7/rx7stuff.htm) this gives you a very good starting point.
When the turbo\'s drop to 0.4 bar if you let off the throttle for a couple of seconds then re try does the power come back?
A
Thanks. That looks pretty handy!
Yeah, in most cases power will come back, but occasionally I\'ll have to clutch it so the revs drop right down before power will come back. But even then, it will not hold full boost all through the revs.
Ok, it sounds like your not holding vacuum somwhere, behind the powersteering pump is a vacuum chamber that needs to hold vacuum for the turbo\'s to work properly, this is achived with a 1 way check valve and under boost your losing vacuum, letting off the throttle allows it to re gain its vacuum thats been lost so when you got to WOT the boost is back.
I am in the middle of trying to sort exactly the same problem as this at the moment, if your not a confident mechanic dont\'s even think about getting into the rats nest properly.
The first thing I would do would check all the hoses you can easily see, just infront of the plenum is the pressure chamber look at all the hoses there and check valves you should also be able to see the hose going down to the pressure chamber have a look there too, see if you can see and bent/kink\'d/split hoses first.
Al
I don\'t think I have a pressure chamber on mine (I believe this is usually a sort of black box in front of the plenum, pretty much at the same height?). Not sure what difference this would make, or if anything has been altered.
The one infront of the plenum is the pressure chamber there is a vacuum chamber too it is tucked behind the power steering pump.
If you don\'t have a pressure chamber then you are probably running non-sequential turbo\'s
When they were working did have a nice liner power delivery or did you have a slight drop in boost at 4500 then a stronget power delivery through to the redline?
Alan
Hmmm. Hadn\'t thought of that. Could explain the quick rise in boost early on, too. And I\'ve never had the boost dip at 4500rpm that is associated with the sequential set up.
The boost would probably rocket to something way too high, but I have the warn level set on my boost controller (Blitz dual sbc) I\'m not sure if it is maybe overboosting & the controller is cutting the boost down? I\'m not 100% sure what to have everything set to on there, though. I downloaded a set of instructions for it, so perhaps I should be looking into working out some settings on that & see what happens.
If someone had done the easier non sequential conversion which doesn\'t involve enlarging the wasgate then there is a good chance of it overboosting are infact if you have a downpipe and decat then its almost definately going to overboost.
All seems to make a bit more sense now. Although If I\'m getting that effect of the valve between the turbos sticking, isn\'t that only a symptom when running sequential. I\'d have thought the valve would be permanently open if it is running non-sequential.
If only FD turbo systems were simple. :xconfused I\'ll be looking to go single turbo, but not for a while yet. So I\'m hoping to completely get to the bottom of this.
In order to do the easier non sequential turbo conversion I belive you disconect the flap and wire it open so it could have just come lose.
Ah! Will check that out. Is it easy to get at?
EDIT: I\'m guessing that the 2 vac pipes that I\'ve circled in this pic would be the ones that would normally be connected to the pressure chamber?
(http://img.photobucket.com/albums/v435/dj_dee99/49e86a98.jpg)
I\'m pretty sure they would be.
Would you know if I should have both of them blocked at the ends, both unblocked, or should I leave them as they are? Not sure if it would affect anything or not.
you only need one blocked, as one is the in tube and one is the out. The in needs blocking and thats it.
Definitely sounds like you are running non sequential, I remember you saying before that you were running to 1bar straight away and wondering how that was happening. Non sequential would make total sense.
Sounds like you have three problems to me. One is that your wastegate isn\'t big enough and generating massive boost straight away. Two you haven\'t got your boost controller set up very well -- Remember with the SBC on a twin turbo you have to set the percentage values and not set it on automatic with a set boost value. It will have real trouble controlling the boost on auto, also if you\'re having problems with the wastegate don\'t set the gain too low. Three, you have a boost leak somewhere, the mooing sound can just be from a loose hose or clip, if you are not holding pressure I guess thats highly likely.
Yeah, I don\'t think I have very good settings on the SBC at the moment. It\'s currently on:
Warn = 0.8
Gain = 2
Ratio = 40
Scramble = off
Are there any better settings worth trying out?
I\'m not sure of where you can just set the boost value, on these.
I kept the gain quite low in the hope of it not hitting high boost so fast. Also in the set of instructions I have, it says that smaller & twin turbos spool up faster & therefore should have a lower gain setting than larger or single turbos.
the ratio is where the actual boost control is set. I suggest bringing that down to around 25 and see what that does for you. I ran mine at 35 on stock twins and that seemed to bring it to around.9
Thanks!:Thumbs-up Will give that a go. Is the gain best left at 2, or should I have that a little higher?
to be honest I never played around with the gain too much I had it at 25 and it was fine for me, spooled ok and didn\'t overboost on the whole so I left it at that. I would say that as wellas setting the warn you can set it to open the wastegate fully if it goes over a certain level but I don\'t remember what the setting was.
Yeah, is that the ratio reduction that\'s available in the warn settings, where you can get it to reduce boost by a chosen percentage if it hits the warn level.
I think I\'m gonna have a few test runs in a bit. Will set ratio at 25 and gain at 0 to begin with, then I\'ll see what effects I get from moving the gain setting up.
Well, a bit of an update.
I\'ve pretty much got the Boost controller settings spot on, now. Pulls nicely & peaks at 0.85.
BUT.....................
once it gets to 4500 rpm, the boost drops to between 0.55 and 0.6 bar. and stays around there.
So, does this mean I\'m am running sequential after all, and the 2nd turbo isn\'t doing anything? Or is it running non-sequential (as there\'s no pressure chamber, etc) and something else is going on?
:confused: :confused:
interesting /informative comments here cheers,get a bit of mooing on mine,on way back from RS3 gave mine a kicking revs upto 7000 and didnt feel 2nd turbo come on - need to get this looked at after holidays (dont have a boost controller)
Pete