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Wastegates and boost control...


Dramier

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So I'm carefully piecing togethor which manifold, turbo and wastegate selection I'm applying to my RB25 in the very near future, and I suddenly realized I have no idea about external wastegates.

 

After a little bit of shopping, I've come to realize the vast majority of wastegates are non-adjustable.. which is strange considering I've been told in the past several times that the proper way to control boost levels is with the remote wastegate...

 

So... my question is... Do I just slap an external wastegate and ignore it considering the PowerFC will control the boost, or do I have to make sure I get a wastegate that matches or exceeds the boost level I plan to run?

 

I'm planning on running 7PSI daily and 25+PSI on the dyno/track... (70MM turbo)...

 

Hopefully what I'm asking here makes sense... sorry if it's a "newbie" question but I didn't realize I knew so little about wastegates until I started upgrading from an internal to an external... heh...

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As a newb i'll try and explain it as accurate and simple as possible :P

 

Internal are attached to the turbo and are often non-adjustable without actually modifiying it.

2041214.006.6L.jpg

 

 

 

External ones run off a pipe that comes out of *i think* your exhaust manifold and are often adjustable. A common practise is using an external wastegate hooked up to your electronic boost controller, and is what i would do if i wanted to switch between 7 and 25 psi.

DCP04008.jpg

 

Anyway hope this helps, dont let sales dudes take you for a ride and make you waste money on stuff you dont need.

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Yeah, I was mostly aware of the theory behind the two.. heh.. (Great explanation though!)

 

What I was not aware of was whether or not an EBC could be used in conjuction with an external wastegate, which I thought was also a mechanical style gate.. (Spring loaded piston basically...?) From what I understand, external's control boost via a pre-determined load spring which opens a valve, rather than a diaphram/actuator like the internals..

 

If that's correct, then how does the EBC control an external? Or is it a "fool the wastegate" style thing exactly like you do with an internal?

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Your external W/G will come with a certin spring rate for a certin range of desired boost range (you can buy different spring rates), then the EBC will use that spring rate to adjust your boost settings to what you set it at.

 

Most EBC's will adjust the boost aprox 5 to 8 lbs below and above what the spring rate is in the external W/G....

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HaHa... where on earth did you come up with that cute little turd of a turbo pic??:lmao:

 

I'm not making fun of you in any way, just the pic.... its so dam cute!!

 

 

As a newb i'll try and explain it as accurate and simple as possible :P

 

Internal are attached to the turbo and are often non-adjustable without actually modifiying it.

2041214.006.6L.jpg

 

 

 

External ones run off a pipe that comes out of *i think* your exhaust manifold and are often adjustable. A common practise is using an external wastegate hooked up to your electronic boost controller' date=' and is what i would do if i wanted to switch between 7 and 25 psi.

[img']http://pktrkt.iwarp.com/images/DCP04008.jpg[/img]

 

Anyway hope this helps, dont let sales dudes take you for a ride and make you waste money on stuff you dont need.

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I honestly dont know how they work inside, but i know a properly hooked up external wastegate and boost controler is much more accurate than most internal wastegate setups - we installed one on my mothers Lexus Soarer TT and it worked a treat because she could drop the boost, and she stopped losing control in the wet, mind you it was running 18 psi previously :)

 

Edit : Also another family friend removed his Power FC and got something else and bought that same boost controller from us, he said it wasnt good enough for 300rwkw *with HIS setup*, Soarer TT again.

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A electronic boost controller controls the waste gate via a solenoid that gets its signal from the control box that gets it signal from a electronic boost sensor.

 

 

If you set it at 25 psi you get 0 PSI to the WG until the controller senses 25 PSI.

 

With a manual boost controller all its doing is restricting the boost pressure to the actuator causing it to open later.

 

I may be wrong on this but with an electronic boost controller spring pressure isn’t as important as it is in a manual setup.

 

From what i have seen and experienced the EBC is allot more accurate and dependable. With manuals you will tend to see boost build slower and have some spiking problems to them.

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After a little bit of shopping' date=' I've come to realize the vast majority of wastegates are non-adjustable.. which is strange considering I've been told in the past several times that the proper way to control boost levels is with the remote wastegate...

 

So... my question is... Do I just slap an external wastegate and ignore it considering the PowerFC will control the boost, or do I have to make sure I get a wastegate that matches or exceeds the boost level I plan to run?

 

Hi all. I'm a bit of a newby to this whole Turbo thing myself. A friend of mine stuck the idea of putting a RB into my 260Z a few months ago, and since then I've been bouncing around trying to get as much info as I could get.

 

From what I know about a waste gate; is that it controls the amount of exhaust entering the turbo, which controls the amount of boost that it will produce. The factory sets this well below what the turbo could actually make. A boost controller intercepts the vacuum signal from the intake manifold, and "tricks" the waste gate into making more boost before diverting the exhaust into the bypass. It does not matter whether it's an internal or external waste gate. An external waste gate does allow for much more adjust ability, and is a must have for high boost situations.

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A electronic boost controller controls the waste gate via a solenoid that gets its signal from the control box that gets it signal from a electronic boost sensor.

 

 

If you set it at 25 psi you get 0 PSI to the WG until the controller senses 25 PSI.

 

With a manual boost controller all its doing is restricting the boost pressure to the actuator causing it to open later.

 

Ok, so there is actually an electromechanical setup there with the EBC's. Good to know. I've only actually seen MBC's, so I've been wondering for a while.

 

Thanks Stony.

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Anyone know how much "useable" "safe" boost you can get out of the stock RB26DETT turbo's?

I think the the factory sets it at 12lbs combined, which seems low for a twin turbo set up. (@ only 6lbs per)

For the start of this project I'm only looking to do some mild mods to the engine to get the power around 350-400 Hp. As I get the rest of the car tweaked out I'll gradually up that. But for now I'm just looking to re-flash the ECU and get a boost controller.

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Anyone know how much "useable" "safe" boost you can get out of the stock RB26DETT turbo's?

I think the the factory sets it at 12lbs combined' date=' which seems low for a twin turbo set up. (@ only 6lbs per)

For the start of this project I'm only looking to do some mild mods to the engine to get the power around 350-400 Hp. As I get the rest of the car tweaked out I'll gradually up that. But for now I'm just looking to re-flash the ECU and get a boost controller.[/quote']

 

There is alot of good information on this subject over at http://www.skylinesaustralia.com , http://www.gtr.co.uk , and http://www.skylinesdownunder.com

 

The stock turbo's are limited, boost wise, because of thier ceramic wheels (designed to spool quickly). They tend to grenade when boosted past a certain point and the resultant debris can potentially trash a motor. I'm no expert on this subject (Matt, Stony, or others are probably more knowledgeable...), but the general concensus seems to be that they are good up to 1.0 to 1.2 bar.

 

...which seems low for a twin turbo set up. (@ only 6lbs per)

 

This is incorrect... the turbo outlets merge into one intake tract. 2 turbo's generating 6psi of boost = 6psi of boost through the intake (assuming no pressure losses/drops).

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There is alot of good information on this subject over at www.skylinesaustralia.com ' date=' www.gtr.co.uk , and www.skylinesdownunder.com

 

This is incorrect... the turbo outlets merge into one intake tract. 2 turbo's generating 6psi of boost = 6psi of boost through the intake (assuming no pressure losses/drops).

 

OK, so a twin turbo only increases the volume of air, not the pressure?

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...I'll guess that 1.0bar is around 10lbs of bost, and 1.2bar is about 15lbs. Is that right?

Sorry 'bout that. 240hoke is on the money.

 

There are multiple ways to measure boost and, even though the scales are different, they mean the same thing.

 

3 (of the many) ways Boost can be measured:

 

Bar

PSI (pounds per square inch - absolute)

mmHG vacuum (millimeters of Mercury)

1 Bar = 14.7 Psi = -.39 mmHG

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Sorry 'bout that. 240hoke is on the money.

 

There are multiple ways to measure boost and' date=' even though the scales are different, they mean the same thing.

 

3 (of the many) ways Boost can be measured:

 

Bar

PSI (pounds per square inch - absolute)

mmHG vacuum (millimeters of Mercury)

[b']

1 Bar[/b] = 14.7 Psi = -.39 mmHG

 

Mostly you will find American cars to have PSI gauges. I have seen Bar gauges I think in factory Toyota's but haven't seen any other than that (factory.) Subaru's like the WRX and STi use the mercury measurement in factory form.

 

I've also seemed to find an average on the SDU forums of 1 bar being the maximum boost any nylon/ceramic turbo will take.. But I also read a very interesting thread that several people stated they made maximum horsepower actually on 10PSI to 12PSI rather than maxed out at 15PSI.. But again, that's merely people's experiences and really isn't representative of any kind of general rule...

 

I'm currently running my stock RB25 turbo at 10PSI with a Greddy S14 FMIC cooling it, and I feel pretty "safe" about turning it up to 1 bar if I wanted to.. however, I'm just going to swap a T3 from a Z31 and be done with it.. I've already busted one ceramic wheel and have no desire to do a second. By the way, if you bust the compressor wheel you can damage the engine, but I don't think you can hurt it with the exhaust wheel, which is what I broke.

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