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The mkiv Supra Owners Club

Making more boost on first turbo then second


robin

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As the title says with my boost controller off I can reach 0.9 bar on the first turbo. This is for example when i use manual mode and floor it from a low speed to keep the revs low. When it reaches the second turbo boost is only a meager 0.76 bar.

 

If I set the controller to 13% duty which is barely doing anything I can get boost cut on the first turbo and still only about 0.82 bar on the second turbo. To get it anywhere near 1 bar on the 2nd turbo I have to put it to 25-30% duty. Its almost as if I need two different duty settings. Any ideas? The hoses and connections all look ok. The hoses for the soleniod are fairly long at about 18".

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If you are getting over 1bar on your first turbo then I'd say two things:

 

1) your sequential system plumbing is all to cock

2) you are going to blow up your first turbo and possibly your engine too.

 

A boost controller shouldn't control turbo #1 due to the nature of the sequential system Fix that problem before trying to raise boost on #2.

 

-Ian

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I can only assume it is reading right as it hits boost cut on turbo 1 if i hold it at 1 bar :(

 

I honestly wouldnt know where to start with the plumbing and I wouldnt trust any of the garages round here as they know less than I do. Some tell me outright lies. "The supra runs 1.1 bar as standard" :rolleyes:

 

does anyone have any diagrams or photos of how a UK spec should be plumbed? I assume its different to a Jap spec one. Maybe a knowledgeable member could visit me or I visit them? I wouldnt mind paying for the trouble if its going to stop turbo one popping on me.

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I have taken some photos and labelled where the hoses go. If anyone spots any errors or knows how it should be done please let me know. If you need any more photos or clarification on where a hose is plumbed please ask.

hose.jpg

hose2.jpg

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I have adjusted the plumbing and I am now getting 0.7-0.75 bar on turbo one.

 

Turbo 2 is similar about 0.75-0.8 Setting the boost controller to about 30% duty lets me see about 0.9 bar+ on turbo 2 with turbo 1 remaining unchanged. Before even 13% would hit boost cut on turbo 1.

 

Thats the last time I let a garage do anything other then brake pads or exhaust work. Ended up spending all afternoon fixing thier faults.

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I'd remove the BC all together mate and see what you get. The plumbing looks wierd to me. Put all hoses back to standard and start from there.

 

I also think the BC is plumbed in wrongly, as I think it should 'T' off from the vacuum line between Turbo 1 and the wastegate actuator, not off the top of the manifold.

 

Can you explain which hose is blocked, as I can't see from the picture?

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The bottom part of the cam cover has always been missing. Well all the time I have owned the car.

 

With the controller set to OFF I get 0.7 on turbo 1 and 0.75 on turbo 2. If i set it to about 30% duty I am getting 0.9 Bar on turbo 2 but turbo 1 stays at 0.75.

 

As far as I know both cats are still in. the rest of the car is completely standard.

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The hose that is blocked looks to be comming from turbo 1. There is also a hose which comes from the back of the engine. I "Think" its a valve for turbo 2. This hose goes to the top of the brass thing by the alternator. I have no idea what the stock plumbing was and there were loose hoses before.

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Id definately look at some photos of stock boost plumbing and get it back to stock.

 

Also, your boost controller is plumbed into the FPR pipe. If this comes loose its bye bye engine as seen in recent threads. So id remove that pipe from the FPR too...

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The hose was going to the pressure tank. I have put it back to the stock position which is the hard pipe at the top on the engine. I have also removed the blocked hose on turbo 1 and plumbed it into the top of the brass waste gate actuator. I think everything is stock at the moment. The boost controller was bleeding off pressure between the pressure tank and the waste gate actuator??

 

I am guessing it should be bleeding off pressure between turbo 1 and the waste gate actuator which is only a very short hose as standard. (2nd photo)

hose3.jpg

hose4.jpg

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Thanks for that pic.

 

So far I have plumbed in the solenoid as per the diagram but I have not capped any of the hoses on the VSV.

 

So I cap the hose coming down from the wastegate actuator and the hose that comes from the VSV to the actuator. What about the left most hose in the pic? Leave it as it is?

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The hose was going to the pressure tank. I have put it back to the stock position which is the hard pipe at the top on the engine. I have also removed the blocked hose on turbo 1 and plumbed it into the top of the brass waste gate actuator. I think everything is stock at the moment. The boost controller was bleeding off pressure between the pressure tank and the waste gate actuator??

 

I am guessing it should be bleeding off pressure between turbo 1 and the waste gate actuator which is only a very short hose as standard. (2nd photo)

 

Good. That looks better. The BC should be fitted between T1 and the actuator and then the pipe from the bottom of the actuator to the VSV cut in half (or replaced) and each half blocked up with a bolt etc

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Thanks for the offer Mark but I think its all sorted. :)

 

I have the solenoid between turbo 1 and the wastegate with the two hoses at the bottom blocked. At 60% duty it hits 1 bar pretty quickly. The is a hell of a kick now when turbo 2 comes online. I was planning to increase the gain until it spiked but I dont think I will need to.

 

The way the garage had done it was to put the solenoid between the pressure tank and the wastegate. The hose on turbo 1 was blocked too.

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