Controlling the stock boost solenoid on an R33 - More free HP?

[sewid]

Hey guys,

Seems like a lot of people go for a bleed valve or some other cheap soloution to run just a bit more boost when it seems perfectly achievable to me without any extra parts.

So if the ECU sends a signal to the stock boost solenoid once we reach 5000rpm which causes the solenoid to open and boost to increase to ~7psi why not just send this voltage to the solenoid all the time, or via a switch in-cabin?

While its not as controllable as a bleed valve. It does cost next to $0 + fiddling time.

So my next question is, does anyone know at what voltage the solenoid activates (12v?) and is it damaging to leave a solenoid permanantly in the open position?

Thanks

[Vovan]

if the solenoid is open all the time you will get uncontrolable boost.. - damage to engine..

[DAMQIK GTS-T]

Not only that, if you leave the solenoid connected to the ecu and feed it 12v it will damage that circuit in the ecu. as it is switched on by a transister inside the ecu not a relay.

[predator]

Disconnect it.. and just run a hose straight from your intake side to the wastegate.. the wastegate will control the boost and give you a couple more PSI than with the solenoid in place.

[sewid]

Originally posted by DAMQIK GTS-T

Not only that, if you leave the solenoid connected to the ecu and feed it 12v it will damage that circuit in the ecu. as it is switched on by a transister inside the ecu not a relay.

A simple diode would prevent this.

[sewid]

Originally posted by Vovan

if the solenoid is open all the time you will get uncontrolable boost.. - damage to engine..

Why do you say that? The solenoid opens at 5000rpm. Providing 7psi not :unlimitedpsi:

Say it opened at 2000rpm the situation would be the same rightl? Except that it would boost at 7psi from 2000rpm instead of 5000rpm?

[Jay95R33]

I looked into this a while ago.

The boost solinoid isn't modulated to give the extra 2psi. It simply opens. It runs on 12v.

All you need to do is disconnect the plug to the solinoid, connect one wire of the solinoid to earth and the other to 12v which is turned on with the ignition.

The ECU won't give any error codes when the solinoid is disconnected.

I tested the solinoid out of the car, so if your going to do it just be VERY carefull that it doesn't over boost.

J

[sewid]

Originally posted by Jay95R33

I looked into this a while ago.

The boost solinoid isn't modulated to give the extra 2psi.  It simply opens.  It runs on 12v.

All you need to do is disconnect the plug to the solinoid, connect one wire of the solinoid to earth and the other to 12v which is turned on with the ignition.

Thanks Jay. I knew the solenoid wouldnt be variable since by definition a solenoid is an on/off magnetically actuated device. A variable device would be more expenisve and require something like a servo. If Nissan did none of us would need to spend the money on EBCs

The ECU won't give any error codes when the solinoid is  

disconnected.

Thanks again that was something i was worried about since most bleed valve install guides/howtos recommend keeping the solenoid attached for "fooling" the ECU...

I tested the solinoid out of the car, so if your going to do it just be VERY carefull that it doesn't over boost.

J

I will test the thing at 12v outside of the car to see if solenoid damage seems likely. The coil in the device may overheat and damage itself. I may be able to get it to actuate at a lower voltage.

[Jay95R33]

In my tests the solinoid clicked open at about 11v and stayed open until the voltage dropped to 9.5v.

Current drain while open was only about 200mA, so it should be fine to hold open indef. I had it open for about an hour and heat wasn't a problem.

I figured that if the sloinoid failed it couldn't do any damage. It would simply stay open or stay closed. It wouln't bleed more air etc..

Let us know how you go.

J

[sewid]

Originally posted by Jay95R33

In my tests the solinoid clicked open at about 11v and stayed open until the voltage dropped to 9.5v.

Current drain while open was only about 200mA, so it should be fine to hold open indef.  I had it open for about an hour and heat wasn't a problem.

I figured that if the sloinoid failed it couldn't do any damage.  It would simply stay open or stay closed.  It wouln't bleed more air etc..

Let us know how you go.

J

Thanks jay, you're taking all the fun out of this and doing my work for me hehe

Im guessing if the solenoid failed it would fail closed since it would be a coil failure and subsequent loss of ability to stay open. So thats fairly safe.

I will write up a report after some test runs.

[ix9]

I completely removed my hose from the wastegate line to the solenoid, and it didnt do a scrap for raising boost.

I even let it bleed out completely, no spike, nothing. just a solid 6psi stock...

then i got the bleeder valve and I had to open it quite a long way just to get 10psi...

.wonder what that was all about...

but now I gots an EBC, so it's even better still..

[b2barker]

The ECU switches the 0V side on terminal 25 on the ECU.

I wouldn't have it on all the time, partly because it may burn out in hot weather, but mainly because it will bleed all the time leading to longer spoolup and possibly too rich an idle. It would be better to manually switch, or switch on boost (cheap ones from Autospeed), or lower RPM or load (AFM) or TPS. There is also a "Thottle Valve Switch" shown between 30 and 57 (ECU terminals) on the schematic I have. I am not sure what this does but it may be usable via a diode and relay to control the solnd.

I read on Autospeed that Audi's with a similar solnd valve responded well to a slight drilling of the bleed hole to bleed off a bit more.

[gtstii]

I'm interested to know how this goes!!

thanks

[Airzone]

I've had mine open for ages... Did the wiring one day I pulled a sickie.

I compared it to a mate who doesn't have this mod, and the benefit was only marginal... Not even half a car length difference... By the time you put your foot down, you're pulling over 4,700rpm and you lose the advantage you get. It's really not worth the extra fuel you use.

[DanS15]

Hey I am just thinkin here, if you wire the solonoid to stay open, isn't this just the same as getting rid of the solenoid completey and running vacuum line in its place..?? Isnt this easier than stuffing around with the solenoid? Then you can just put different size restrictors in the line to give different amounts of boost.

All sounds like a waste of time to me. No diff to the ole t-peice bleed valve scenario. But I suppose $0 compared to $2 worth of vacuum hose and restrictor...

[Airzone]

C'mon - $0.30 by the time you factor in wire and crimps

The solenoid acts like a T piece when it's open, venting to the BOV return line. So you'd need some hose and a T piece. When it's closed, it's just a straight line to the wastegate for the princely 5psi of boost

[b2barker]

Originally posted by DanS15

Hey I am just thinkin here, if you wire the solonoid to stay open, isn't this just the same as getting rid of the solenoid completey and running vacuum line in its place..??

No. If you pull the plug on the solenoid so it never opens it would be the same as removing it.

[sewid]

I took the plug off the solenoid today and attached clips to the Accessory +12v and ground today. This opens the solenoid whenever the ignition is switched on.

The car pulls harder now and achieves full boost (~7psi or just over the +3.5 mark on the stock boost guage) from about 2500 - 2600 rpm.

This makes the ride feel smoother and faster basically because when you're accelerating hard in a stock Skyline you know you're waiting for that 5000rpm boost increase. Now there is no wait.

Anyway, the mod took 10 minutes of my time. Involved less than 1 meter of wire, and assorted little clips all of which were lying around. I think i'll just leave it there for a while.

[Airzone]

You'll have to tell me what you think of the fuel economy... I thought it was pretty poor for city driving after I did this mod... Maybe because when you put your foot down you're getting more boost...