Boost drops

[Reinhoud]

Hi all,

 

I had a TD04 on my bike (GS1000), put a VF23 on it, have the same boost regulator with a ball and a spring.

When I give it to her now, the boost gauge goes to 15 psi, and after about a second it drops to about 11/12 psi.

It never did that with the TD04. I know I can solve it by raising the boost a bit, but might there be something wrong?

 

I also think the VF23 spools up a bit slow, the TD04 was more fun. I had a TD05 on it when I did put a turbo on it, it was a bit laggy, but on boost it went very well!!

The VF23 comes in very gradually, doesn't really kick in, the more revs the harder it goes, but never really exciting, the TD05 did get exciting and that's supposed to be a bigger turbo.

For some reason I think there's something wrong. I disconnected the wastegate, it still spools up the same way, makes a fair amount of boost, gave me a bit of a fright

 

I thought I ask before I start disassembling parts of the bike..

Something wrong, or is it a property of this turbo?

 

Thanks

 

 

 

[Arttu]

I think your boost drop is actually boost spike It's probably caused by the wastegate actuator in combination with your boost regulator. Maybe the actuator has more volume so when the gate starts to open it needs more air through the regulator before the gate is properly open and that causes delay. And if the actuator has softer spring you need to turn the regulator more close which slows down the reaction too. You can test it without the regulator and see how it works then.

Gradual boost building might be just a feature of the turbo but that's hard to say without detailed data. One explanation could be that the VF23 has bigger A/R turbine side. I think my VF34 behaves more or less same way. It starts to build little boost pretty early, slightly above 3000rpm. But it needs quite much more rpms to reach full boost, over 5000rpm for 1 bar. So there isn't any violent kick at any point, it just pushes harder and harder as the revs rise.

[Reinhoud]

3 hours ago, Arttu said:

I think your boost drop is actually boost spike It's probably caused by the wastegate actuator in combination with your boost regulator. Maybe the actuator has more volume so when the gate starts to open it needs more air through the regulator before the gate is properly open and that causes delay. And if the actuator has softer spring you need to turn the regulator more close which slows down the reaction too. You can test it without the regulator and see how it works then.

Gradual boost building might be just a feature of the turbo but that's hard to say without detailed data. One explanation could be that the VF23 has bigger A/R turbine side. I think my VF34 behaves more or less same way. It starts to build little boost pretty early, slightly above 3000rpm. But it needs quite much more rpms to reach full boost, over 5000rpm for 1 bar. So there isn't any violent kick at any point, it just pushes harder and harder as the revs rise.

Aha, I didn't look at it like that.. It does look like that with this turbo the last 3 psi do way more as with the TD04

With no boost regulator it's the same. So it's the nature of the beast then, mine does the same as what you discribe.

I thought I might have a little leak somewhere in the exhaust or the valve of the wastegate.

 

Problem solved then

 

I thought that because TD05 is bigger the VF should spool up quicker as the TD.

What I did notice, with the VF I don't have detonation anymore.

 

Thanks

Edited March 22 by Reinhoud

[badger]

Same turbo and does similar.  Mine starts boost about 3500rpm, stays at about 10psi for ages but doesn't hit 1 bar until 8-9k. (14psi spring and I do get boost creep sometimes). I'm sure it used to build boost a lot quicker but I'm questioning that. 

To those that know, would a softer, say 6psi spring and a digital boost controller alter that characteristic letting the controller cap the limit higher, i.e 15psi etc? 

Edited March 27 by badger

[Reinhoud]

14 hours ago, badger said:

Same turbo and does similar.  Mine starts boost about 3500rpm, stays at about 10psi for ages but doesn't hit 1 bar until 8-9k. (14psi spring and I do get boost creep sometimes). I'm sure it used to build boost a lot quicker but I'm questioning that. 

To those that know, would a softer, say 6psi spring and a digital boost controller alter that characteristic letting the controller cap the limit higher, i.e 15psi etc? 

Interesting... The more revs, the more power, but it never gets really exciting.. With the TD04 it starting to lift the front wheel in 4th gear at 110km/h, now it needs to do 160km/h before it does lift the front wheel, just to give an idea.

It looks like there's a boost leak, but there isn't, I think..

[Reinhoud]

15 hours ago, badger said:

Same turbo and does similar.  Mine starts boost about 3500rpm, stays at about 10psi for ages but doesn't hit 1 bar until 8-9k. (14psi spring and I do get boost creep sometimes). I'm sure it used to build boost a lot quicker but I'm questioning that. 

To those that know, would a softer, say 6psi spring and a digital boost controller alter that characteristic letting the controller cap the limit higher, i.e 15psi etc? 

If you ever use a boost controler, use one with a ball and spring. These build up boost way faster. Bleed valves just bleed/leak, this takes longer to actuate the waste gate.

Ball spring controllers you recognise on nipples on the bottom, and one 90 degrees on the side

[Arttu]

17 hours ago, badger said:

Same turbo and does similar.  Mine starts boost about 3500rpm, stays at about 10psi for ages but doesn't hit 1 bar until 8-9k. (14psi spring and I do get boost creep sometimes). I'm sure it used to build boost a lot quicker but I'm questioning that. 

To those that know, would a softer, say 6psi spring and a digital boost controller alter that characteristic letting the controller cap the limit higher, i.e 15psi etc? 

Sounds like the wastegate is opening already at 10psi and then there is boost creep at higher rpm.

A boost controller should help building boost faster. It will help to keep the gate closed until you hit the target. But it can't help with the creep, if the gate can't flow enough to keep the boost down then the controller can't do anything to lower the boost.

Any way, if you feel that the turbo is spooling up slower than it should it's good to check carefully all possible exhaust and boost leaks. Especially exhaust leaks will affect a lot on spool-up.

[badger]

On 3/28/2024 at 3:29 PM, Arttu said:

Sounds like the wastegate is opening already at 10psi and then there is boost creep at higher rpm.

A boost controller should help building boost faster. It will help to keep the gate closed until you hit the target. But it can't help with the creep, if the gate can't flow enough to keep the boost down then the controller can't do anything to lower the boost.

Any way, if you feel that the turbo is spooling up slower than it should it's good to check carefully all possible exhaust and boost leaks. Especially exhaust leaks will affect a lot on spool-up.

That's makes a fuck load of sense! I hadn't considered the waste gate at all! I'll wind that in and see if it improves! Thank you

 

On 3/28/2024 at 1:19 PM, Reinhoud said:

If you ever use a boost controler, use one with a ball and spring. These build up boost way faster. Bleed valves just bleed/leak, this takes longer to actuate the waste gate.

Ball spring controllers you recognise on nipples on the bottom, and one 90 degrees on the side

That makes sense. I'll have a fuck about with the wastegate and see what happens. What arttu said about boost creep is a good point. I've had a look at the opening of the waste gate and there's fuck all material left to take out so I don't know what else I can really do to help that. 

Thanks again for the replies!! 

 

[peter1127]

If there is boost creap, be careful. Boost could get higher then intended. I assume you have an inernal wastegate with actuator. If you tighten that wastegate to get higher boost, it also cant open much resulting in boost creap. For higher boost, better use an actuator with stronger spring, or a boost controller.

[badger]

2 hours ago, peter1127 said:

If there is boost creap, be careful. Boost could get higher then intended. I assume you have an inernal wastegate with actuator. If you tighten that wastegate to get higher boost, it also cant open much resulting in boost creap. For higher boost, better use an actuator with stronger spring, or a boost controller.

I do yes. I did replace the actuator for a better one which didn't help. It's got a 1 bar spring. I do keep an eye on it but it's not ideal, prefer to be keeping an eye on what's Infront of me 

[badger]

As an update to this, new spring in the bov and all is well