Want to run 21 psi on Big 16g/pump but external wastegate cannot be set for 21 psi

[4gfun]

Well I have thought this out for a while and feel that I have the supporting mods to meet my goal.

The issue is this. The Tial 40mm wastegate springs only allow for either 20.305 psi or 21.765 psi.

My car is a 91 GVR4 and I have done ALOT of research as to running a Big 16g on pump and I concluded that 21 psi was where I wanted to be to have a high 12 second car.

What would you do?

Thanks!

 

[toofast82]

I'g go with the 21.765psi spring if I had to choose. You can still run a mbc if needed to dial boost in. I had a 14psi spring when I ran a b16g/external and it held 24psi with the mbc

 

[NOSLO2PT0]

You can run LOWER springs if you want lower minimum boost levels. The MBC is to RAISE boost above whatever the spring is rated at.

 

[4gfun]

Thanks for the ideas. If I go with the lower springs, wouldn't the MBC not allow me to raise boost any higher than the psi the wastegate opened at?

If I go with higher springs, would it be possible that the wastegate would never open if I tuned it to say 21 psi?

I have a wastegate dump and I don't want to miss hearing it.

Any ideas, maybe I am confused.

Thanks!

 

[kidtsi]

Thanks for the ideas. If I go with the lower springs, wouldn't the MBC not allow me to raise boost any higher than the psi the wastegate opened at?

If I go with higher springs, would it be possible that the wastegate would never open if I tuned it to say 21 psi?

I have a wastegate dump and I don't want to miss hearing it.

Any ideas, maybe I am confused.

Thanks!

never buy a wastegate with a higher pressure spring than your goal psi.

let say if u buy a spring for 25psi, u cant lower that not even with an manual boost controller. so if u want to run 21 psi get a springs for 21 psi or less so u can turn up the boost or leave it at the spring pressure psi.

 

[4gfun]

never buy a wastegate with a higher pressure spring than your goal psi.

let say if u buy a spring for 25psi, u cant lower that not even with an manual boost controller. so if u want to run 21 psi get a springs for 21 psi or less so u can turn up the boost or leave it at the spring pressure psi.

Makes sense but part of what I am saying is this. How can I get higher pressure than what the wastegate will open at?

So if I get a spring for 18 psi and I set it to 21 psi with the MBC wouldn't the wastegate stop it from ever reaching 21 psi? Isn't the wastegate the final authority?

 

[kidtsi]

Makes sense but part of what I am saying is this. How can I get higher pressure than what the wastegate will open at?

So if I get a spring for 18 psi and I set it to 21 psi with the MBC wouldn't the wastegate stop it from ever reaching 21 psi? Isn't the wastegate the final authority?

lets say the mbc is the final authority, but cannot lower what the wastegate spring is at.

 

[4gfun]

lets say the mbc is the final authority, but cannot lower what the wastegate spring is at.

That part I understand. I just don't get how the MBC can increase boost over what the wastegate is set at in psi. Not doubting you, it is me who has a LONG way to go.

Not sure if you saw this thread, but this is what is throwing me off:

http://www.dsmtuners.com/forums/newbie-forum/377516-wont-build-more-than-18-psi-my-big-16g.html

 

[kidtsi]

That part I understand. I just don't get how the MBC can increase boost over what the wastegate is set at in psi. Not doubting you, it is me who has a LONG way to go.

Not sure if you saw this thread, but this is what is throwing me off:

http://www.dsmtuners.com/forums/newbie-forum/377516-wont-build-more-than-18-psi-my-big-16g.html

he might have like a 9 psi spring or something because u can raise the boost with a boost controller but u can just double it and then u cant raise it anymore. u know what i mean?

also air goes to the digraph inside the wastegate not letting in it open till the force of the boost if higher than what inside the wastegate is.

 

[4gfun]

he might have like a 9 psi spring or something because u can raise the boost with a boost controller but u can just double it and then u cant raise it anymore. u know what i mean?

also air goes to the digraph inside the wastegate not letting in it open till the force of the boost if higher than what inside the wastegate is.

Yes I am starting to catch on. Thank you!

Well I opened it up and the spring is 14.53 psi. I can only get to 20 psi and then it falls to 18 psi when I rev it. This is with the boost controller fully open.

 

[kidtsi]

Yes I am starting to catch on. Thank you!

Well I opened it up and the spring is 14.53 psi. I can only get to 20 psi and then it falls to 18 psi when I rev it. This is with the boost controller fully open.

im not sure of the percent of much u can raise the boost from that 14.7 psi spring. have u checked for boost leaks?

 

[4gfun]

im not sure of the percent of much u can raise the boost from that 14.7 psi spring. have u checked for boost leaks?

No I haven't checked for boost leaks. I need to get on that bandwagon and research how to do it. (I have been resistant to it for years ). I don't have a compressor either.

Vacuum is beautiful on the car, but I know that doesn't mean anything.

Yes that is the unknown variable on the spring. (Didn't you mention that you could double it with a MBC automatically). If that is the case then something else is up. Not sure if you notice on the other thread, but my stock BOV is uncrushed as well.

Since I already have it apart, I will get the 20.305 spring and then maybe crush the BOV?

If that fails, then I guess I will check for boost leaks.

 

[kidtsi]

No I haven't checked for boost leaks. I need to get on that bandwagon and research how to do it. (I have been resistant to it for years ). I don't have a compressor either.

Vacuum is beautiful on the car, but I know that doesn't mean anything.

Yes that is the unknown variable on the spring. (Didn't you mention that you could double it with a MBC automatically). If that is the case then something else is up. Not sure if you notice on the other thread, but my stock BOV is uncrushed as well.

Since I already have it apart, I will get the 20.305 spring and then maybe crush the BOV?

If that fails, then I guess I will check for boost leaks.

if u first check for boost leaks, ull save money, i dont think the wastegate is dropping the boost seriously.

 

[4gfun]

if u first check for boost leaks, ull save money, i dont think the wastegate is dropping the boost seriously.

Hard to argue that one on the boost leaks. I think that I can build up something without a compressor to get it done if I remember correctly. I went back to the original thread to see what the wastegate theory posters thought about whether or not the spring is enough to allow it to boost to 21 psi. Anyways the spring is already out so I might as well just get the best price I can on it and just wait for it to get here.

Still, the BOV being uncrushed has to be a factor from what I can see right?

 

[kidtsi]

Hard to argue that one on the boost leaks. I think that I can build up something without a compressor to get it done if I remember correctly. I went back to the original thread to see what the wastegate theory posters thought about whether or not the spring is enough to allow it to boost to 21 psi. Anyways the spring is already out so I might as well just get the best price I can on it and just wait for it to get here.

Still, the BOV being uncrushed has to be a factor from what I can see right?

yup, but doing a boost leak will show you. you should get an air compressor from a friend or family member.

but yeah that bov cant handle that kind of psi. if i remember correctly they leak after 15 psi.

 

[4gfun]

yup, but doing a boost leak will show you. you should get an air compressor from a friend or family member.

but yeah that bov cant handle that kind of psi. if i remember correctly they leak after 15 psi.

Will it actually show the BOV leaking? No pals or family out here in the wilderness besides my 4g63.

 

[Bluefire16]

^^ Like i already told you, yes your BOV can be a factor. If you want to run more than 18psi you should crush it.

Secondly, i mentioned the boost leaks already. Just search in the forum for "How to preform a boost leak" You will find 100s of answers. I also already mentioned how over the years your couplers are getting to be old and maybe cracking and ripping.

Good luck

 

[4gfun]

^^ Like i already told you, yes your BOV can be a factor. If you want to run more than 18psi you should crush it.

Secondly, i mentioned the boost leaks already. Just search in the forum for "How to preform a boost leak" You will find 100s of answers. I also already mentioned how over the years your couplers are getting to be old and maybe cracking and ripping.

Good luck

Thanks

 

[NOSLO2PT0]

Here is how it works. Lets say you have a 14psi spring in your wastegate. It's going to require 14psi of pressure to open it. So...as soon as the wastegate sees that 14psi, it opens. The MBC basically prevents that signal from reaching the wastegate until the desired amt of boost is reached. Most MBC's are simple ball/spring designs. Look at this diagram.

http://johnmonnin.netfirms.com/images/BoostBallValve3.jpg

Once the air pressure (i.e. boost) is great enough to overcome the pressure exerted on the ball, the ball unseats and the air rushes past and goes to the wastegate. Obviously the air signal is greater than 14psi so the wastegate naturally opens. If the mbc is set for something less than 14psi, the air will still get past the ball, but the gate won't open because there isn't enough pressure to make it open.

Get it now?

 

[4gfun]

Here is how it works. Lets say you have a 14psi spring in your wastegate. It's going to require 14psi of pressure to open it. So...as soon as the wastegate sees that 14psi, it opens. The MBC basically prevents that signal from reaching the wastegate until the desired amt of boost is reached. Most MBC's are simple ball/spring designs. Look at this diagram.

http://johnmonnin.netfirms.com/images/BoostBallValve3.jpg

Once the air pressure (i.e. boost) is great enough to overcome the pressure exerted on the ball, the ball unseats and the air rushes past and goes to the wastegate. Obviously the air signal is greater than 14psi so the wastegate naturally opens. If the mbc is set for something less than 14psi, the air will still get past the ball, but the gate won't open because there isn't enough pressure to make it open.

Get it now?

I get it and thanks...(I was starting to figure this out on my own but wasn't sure)

What I don't get is this...

Is the boost controller going to be enough to get up to 21 psi with the 14 psi spring in the wastegate if there are no boost leaks or do I need to get a stiffer spring?

Thanks!

 

[GRAVEDIGGER]

You should have no problem reaching 21psi with it.

 

[4gfun]

You should have no problem reaching 21psi with it.

Thanks, very clear!

 

[NOSLO2PT0]

It all depends on the spring inside the MBC. I've seen an MBC not be able to go over 15psi. Also saw one that wouldn't go over 22psi. The springs inside them DO wear out over time.

 

[kidtsi]

get a turbo xs bleeder type mbc, for me is awesome.

 

[4gfun]

get a turbo xs bleeder type mbc, for me is awesome.

Thank you...I will give it a shot if I still have issues. I have a doughnut compressor now and whether or not it will work for boost leaks remains to be seen.

It all depends on the spring inside the MBC. I've seen an MBC not be able to go over 15psi. Also saw one that wouldn't go over 22psi. The springs inside them DO wear out over time.

The spring in the wastegate or MBC?