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Thumper

Solution to boost drop at high rpms? Spring the wastegate actuator?

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I just thinking about my problem of boost drop at high rpms. I know its not caused by my turbo running out of steam because I can turn up the boost and it goes up the same amount even at redline. My friend has a srt-4 that is known for having this problem and what most of them do is put a new wastegate on with a higher boost actuator and then the boost is much more stable.

 

This makes sense to me since the stock wastegate on a z is set at 6-7psi and I'm trying to more than double that at 15psi. My question is there any way I can upgrade my wastegate actuator or can I put a spring on the original one to tighten it? Thanks

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I ran a spring on mine for years. You'll have to experiment with the tension, but I had to use a pretty stiff one to get the desired results. I ran up to 20psi on theis setup on my stock t-3 and had no fade at all at 6000 when I shifted. I used the same method when installing my hybrid running 25psi. i eventually bought a used profec so I could have easy adjustability

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Guest bastaad525

Yep SRT-4's do this pretty badly, from 15 down to like 10psi by redline in stock trim.

 

My Z used to do it REALLY bad as well, from 14psi to 10-11psi by 6000rpm, that was when the MBC was getting it's signal from the compressor housing.

 

I now have the MBC getting it's signal from the intake manifold, and I only drop 1 psi or so by 6000rpm.

 

 

But yeah, this is all attributed to a weak WGA spring.

 

However, one trick that the SRT guys do that seems to make it hold WAY better, is to just put some preload on the stock WGA, by ever so slightly bending the arm to make it shorter. You could probably get much the same effect by doing the trick guys do here of threading the WGA rod, or cutting it and welding in a turnbuckle to make it adjustable (differents roads to the same result).

 

In the meantime, get your signal from the manifold if you aren't already.

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You need to add a spring to you wastegate to increase tension. As the back pressure increases as revs go up it forces it open. Same with external gates. It doesn't matter were you get the signal from, if the spring isn't stiff enough it will open at higher boost / rpms. I went from an 8 psi WG spring that would only hold 22 psi and it still dropped a little to an 18 psi WG spring that has held 28 psi so far.

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Guest bastaad525

what I want to know is why, for an SRT-4, there are quite a few options for upgrading your WGA, yet, for the turbo Z there are none (that I know of, at least?). The Z would benefit from it just as much.

 

I know there are external wastegates but I'm talking about just an actuator that you can bolt on to the stock turbo.

 

This is the first or one of the first upgrades everyone does on their SRT. It's not like they don't have the same options as Z's do, as far as, say, manual boost controllers or electronic ones. Someone should start a small side business of modifying stock WGA's :P

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what I want to know is why' date=' for an SRT-4, there are quite a few options for upgrading your WGA, yet, for the turbo Z there are none (that I know of, at least?). The Z would benefit from it just as much.

 

I know there are external wastegates but I'm talking about just an actuator that you can bolt on to the stock turbo.

 

This is the first or one of the first upgrades everyone does on their SRT. It's not like they don't have the same options as Z's do, as far as, say, manual boost controllers or electronic ones. Someone should start a small side business of modifying stock WGA's :P[/quote']

 

I'm thinking the same thing. Although someone mentioned that top-end sells actuators and you can probably by a universal one and just weld it on the stock t3. But it would be nice to have a 12psi or 15psi wastegate.

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No big money in Z/ZX aftermarket. Z/ZX's are cheap sports car owned by money pinchers. That is one on the main reasons we own Z's (cheap). Lets face it, if we had the money we would all own a new Porsche turbo.

Thats true! I call my Z the poor mans Porsche, I have always wanted one but I built my Z and Love it, it will dew for now.

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Z/ZX's are cheap sports car owned by money pinchers. That is one on the main reasons we own Z's (cheap). Lets face it, if we had the money we would all own a new Porsche turbo.

 

Sorry I don't agree. Anybody with 80k can go and buy a porsche. But not everyone can have 2k-20k buy a Z and build it up to be unique. Sure other z's will have something similar to your car but I bet any one of us could tell our car from anybody elses car.

 

Well i'm going to put a spring on my wastegate to increase its holding ability at high rpms. I'll post when I have some conclusive results. 1-2 weeks.

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Any chance of using the boost pressure to assist the spring on the gate? I did some BMW turbo stuff years ago and we had special tops made for the wastegate that used air pressure from the manifold fed through a small pressure regulator to assist the spring side of the gate. You could dial a boost from the driver's seat. I haven't messed with a BOV but it worked for what we wanted to do. It's 20 something years old so pardon me if it's behind the times.

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Any chance of using the boost pressure to assist the spring on the gate? I did some BMW turbo stuff years ago and we had special tops made for the wastegate that used air pressure from the manifold fed through a small pressure regulator to assist the spring side of the gate.

 

 

 

That's what I did and alot of other people do with external gates. They already have the extra port on top. You will still run into boost dropping if trying to run substantially more boost than the spring is set for.

 

Thumper, read post 7

 

http://forums.hybridz.org/showthread.php?t=104816

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I'm going to give this actuator a try. The sweet thing about this unit is I can change the springs out like an external unit. Since I ported my wastegate hole I can't seem to keep stable boost above 13 psi.

 

Actuator:

http://www.forgemotorsport.com/content.asp?inc=product&cat=0001&product=FMAC048

 

Springs:

http://www.forgemotorsport.com/content.asp?inc=product&cat=0019&product=FMAS048

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Guest bastaad525

hasn't someone changed the internal springs on the WGA? Adding a spring externally on the arm is going to give the same characteristics I would think... a high boost peak at mid rpm falling off by redline.

 

Same thing happens with my SRT-4. Stock, it boosts 15psi than falls to like 10psi by redline. I added a spring onto the WGA arm, and now it spikes like 18psi and falls to like 13psi to redline.

 

The stock spring in the SRT's WGA though is REALLY weak, it will only hold about 4psi by itself, the boost is actually controlled by a computer controlled solenoid that bleeds off pressure to get the right boost.

 

On the Z... maybe the combination of a spring on the WGA and a manual boost controller would do the trick?

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hasn't someone changed the internal springs on the WGA? Adding a spring externally on the arm is going to give the same characteristics I would think... a high boost peak at mid rpm falling off by redline.

 

Same thing happens with my SRT-4. Stock' date=' it boosts 15psi than falls to like 10psi by redline. I added a spring onto the WGA arm, and now it spikes like 18psi and falls to like 13psi to redline.

 

The stock spring in the SRT's WGA though is REALLY weak, it will only hold about 4psi by itself, the boost is actually controlled by a computer controlled solenoid that bleeds off pressure to get the right boost.

 

On the Z... maybe the combination of a spring on the WGA and a manual boost controller would do the trick?[/quote']

 

 

Did you read post 7 on the link above?

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Bastaad525, Yes adding a spring to the wastegate arm will help the boost bleed down. It is similir if not ghetto way of putting on a different wastegate with a stiffer spring. The boost will go up and when the car is at higher boost the wastegate springs (both internally and externally now) will be strong enough to hold the wastegate flapper closed. The wastegate flapper is being pushed in by positive pressure built up in the turbo manifold.

 

My guess on the srt-4 is that you didn't add enough of a spring. It is spiking to 18psi because the ecu isn't fastenough to open the wastegate. Then drops off like normal. When you upgrade the wastegate it is so strong that the ecu is trying to make it go down but the spring is too strong. So stock srt-4 wastegate is 4psi you put a spring on it to make is 8-10psi. What you need to do is get a strong enough spring to have 17psi. Then the ecu will send as much air to the actuator as possible but the wastegate will still boost at 17psi all the time.

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Sorry I don't agree. Anybody with 80k can go and buy a porsche. But not everyone can have 2k-20k buy a Z and build it up to be unique. Sure other z's will have something similar to your car but I bet any one of us could tell our car from anybody elses car.

 

I didn't say that Z's weren't unique. I just said that most Z guys are going to stretch the hell out of every dollar they put in theirs Z's. And most do the work themselves and even do most of the fabrication work. So, there is not a lot of money for the suppliers of aftermarket stuff for old Z's.

 

The aftermarket would rather sell a complete turbo kit for a 350Z for 8K. They know only a very small number of Old Z owners would put a $8K turbo kit on a $2k car. But adding a $8K turbo kit to a $35K car is a different story.

 

And 95% of Z current owners would not own a Z if money was not an issue. The Z is cheap sportcar, so people that buy them most likely aren't super rich. That is the whole point of the car. Sure we have grow to love them but initially the cheap price gets your foot in the door.

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Guest bastaad525

My guess on the srt-4 is that you didn't add enough of a spring. It is spiking to 18psi because the ecu isn't fastenough to open the wastegate. Then drops off like normal. When you upgrade the wastegate it is so strong that the ecu is trying to make it go down but the spring is too strong. So stock srt-4 wastegate is 4psi you put a spring on it to make is 8-10psi. What you need to do is get a strong enough spring to have 17psi. Then the ecu will send as much air to the actuator as possible but the wastegate will still boost at 17psi all the time.

 

 

Actually I just got lazy and ordered a whole 'nuther WGA unit. It was $100 shipped with 2nd day air shipping. I've talked to a few guys who have it and they say they can easily get the thing to hold 14-15psi all the way to redline (as opposed to 10-11psi on the stock WGA). Though this car doesn't seem to make as much power per psi of boost as my Z did (Z made like 15hp + per psi, this car seems to make 5 or 10hp if lucky), BUT an extra 4-5psi at redline really helps the topend power out... should be nice. The spring was okay but yeah the computer was doing all kinds of funky things with the extra spring on there. I actually pulled it back out and am just on the Mopar stage 1 setup now.

 

However with the aftermarket WGA installed you run it on different vacuum/boost source and take the computer control completely out of the equation. Amazingly, the computer does NOT freak out when you do this, no check engine lights or anything of the sort. It seems about 75% of the SRT owners on the forums run an aftermarket WGA set up like this with no problems. That's really a trip... my Sentra SE-R would throw check engine lights if ANYTHING was disconnected. The only time the SRT will throw a code is if the boost is turned up way high no the stock computer, which is the main reason I upgraded to stage 1... it wont throw any codes, if boost gets too high it will just cut fuel like a rev limiter, but no limp mode or anything... it will only do it when that excessive boost is present. Pull over, turn the boost back down w/o even turning off the car and it will drive fine from that moment on... pretty sweet for an OBD II car.

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What wga are you ordering. I personally like the agp one and have only found it for $160.00 I think I remember seeing a $100.00 but it was a no name and didn't want my friend to take the chance. You got the website for the one you ordered?

 

Here is a fun question ok we put a mbc on his srt-4. It is 18-19psi spike down to 13psi by redline. Every few days or so the check engine light comes on and the code is "over boosted". With the check engine light on it still runs perfectly. Not even less gas mileage. The car is suppose to have a stage 1 ecu not sure though. The fuel injector cover has the stage 1 logo but I do not know how to check the ecu it self. Its an 04' model. This car was bought used modified. From what you wrote he should not receive this light if he has a stage 1 ecu he should only have the timing being pulled? Is this correct or am I reading wrong? I guess i'll get a membership to srt-4 forums and ask but i'm too lazy and he doesn't have the knowledge to ask questions. Thanks

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Guest bastaad525

first off stage 1 ECU should NOT be throwing codes, that's the main reason I upgraded to stage 1. If he's getting check engine lights he is most likely stage 0. If a stage 1 ECU sees too much boost it will either pull timing or if it gets really high it will cut fuel/ignition in the same manner it does if you bump the rev limiter.

 

I have spiked 18psi for quite some time since installing my stage 1 and even hit 20psi a couple times, never got a check engine light, but when it hit 20 I felt the car cut back hard, like it lunged forward and then suddenly threw out the anchor... was very disorienting. But never a check engine light. The only way to check the ECU is to either a) take it to the dealer and have them check or B) pull out the air filter box and look for the label on the ECU. It should say "Mopar performance stage 1 turbo". However, I imagine the label wouldn't be too hard to counterfeit so if it does say stage 1 and you're getting check engine lights I say take it to a dealer.

 

About the WGA, I orderd the one made by Kinetic, from a place called PT Performance. I don't have a website address for him, he contacted me directly thru PM a while back to offer me some stuff and we've kept in contact that way ever since. He sells the Kinetic WGA for $99 shipped. It's not as pretty as the AGP which is made of billet aluminum, but it's just as functional.

 

I've actually talked to a few guys who've tried both and like the Kinetic better, saying it holds boost better to redline. Otherwise it is very similiar to the AGP in everything but looks. I'm not trying to win carshows so would rather save the $50+. If you want I can pass you or your friends email and I"ll pass it on to this guy to get you guys in contact. He's given me really good deals on stuff so far including a stage 1 for $350 shipped, the WGA for $99, some motor mount inserts for $25 shipped (usually like $30-40)... he gives good prices and is really quick about shipping so far I've gotten everything from him within two-four days. He's also very communcative and helpful. In other words... BUY STUFF FROM HIM ALREADY!

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Guest bastaad525

Installed the WGA on my SRT-4 today. Works just as advertised. After adjusting the length of the arm, I now get no spiking, boost runs straight up to 17psi and holds right there, then slowly falls off as RPM goes up, down to about 14-15psi by redline. Much better than stock spiking 16, settling immediately to about 14, then falling down to 10-11 by redline. Top end pull is MUCH better.

 

I bet this thing could be used on a Z if you custom made a bracket for it. At the loosest setting the spring in this WGA holds about 13psi, can be adjusted up to well over 20. But I guess welding a turnbuckle inline with the stock WGA arm would achieve much the same result.

 

Anyways Thumper yeah for your friends SRT I recommend this WGA, $99 shipped, works just as well as everyone with the AGP one, just not as pretty, but looks no worse than stock. Anyone who sees it and doesn't know an SRT will just think it's stock.

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