Clio 172 Turbo - boost spikes & peak boost issues

[Fishfire]

So, I've been trying to set the boost on my 172 turbo, but I can't get it to stop spiking.

I've tried two types of manual boost controller (ball & spring Dawes and Atomic bleed type but each resulted in the same spike and inability to make and hold peak boost.

If I increase the boost through either controller, all that happens is it spikes higher but still settles down to around 6psi give or take.

I need to hit and hold 7-8psi

The turbo is a maxspeedingrods replica 2871. These are known to have much smaller wastegate ports than the Garrett's they're based on so I ported mine out prior to fitting to avoid spikes.

The only thing I can think of is the wastegate actuator itself.
It's an adjustable type with a '5psi' spring but in reality is more like a 2 or 3psi spring.

I'm wondering if a heavier spring in the actuator would resolve this issue?

It's got me scratching my head tbh 🤔

 

[Fishfire]

Forgot to say it's currently spiking to 9 - 10psi before dropping to 6psi (ish)

Here's pics of the wastegate port before and after porting:

Here's the wastegate actuator I bought with the quoted (white) spring pressures:

 

[Yarp]

What happens just on actuator pressure?

Is the pre-load set correctly on the actuator too? The arm isn’t under any twisting or odd forces or anything that could be affecting its ability to move?

 

[Fishfire]

What happens just on actuator pressure?

Is the pre-load set correctly on the actuator too? The arm isn’t under any twisting or odd forces or anything that could be affecting its ability to move?

Actuator pressure is maybe 3 psi on a spring that should be closer to 5psi.

I started at actuator only pressure and increased boost via the MBC which did raise the boost but no matter what I do with the MBC, it always settles on about 6psi with the only thing raising is the spike. After fitting a Dawes device today, it's almost the same as the outgoing bleed device which makes me thing the actuator is the issue.

Preload was half a hole, as is usual. Though I have increase the preload to its max which has had little effect.

Im thinking the spring is just too light to work effectively, so I've ordered a 0.5bar spring which is about 7.5psi, but with these springs seemingly lighter than advertised in hoping it should be bang on what I need and should run mostly actuator pressure with a tiny bit of an increase from the boost controller......I hope!

 

[Fishfire]

The arm is the bent type rather than straight which gives much more room when fitting the actuator.
I operated the actuator with a pump prior to fitting and all seems ok to be fair 🤔

 

[Brigsy]

Pressure up the boost circuit and check for leaks. If none, actuator is most likely the issue, change it for a turbosmart or similar quality item

 

[Fishfire]

Pressure up the boost circuit and check for leaks. If none, actuator is most likely the issue, change it for a turbosmart or similar quality item

There's no leaks.... Been through the system several times now.

It's a Kinugawa adjustable actuator which I've used before on my previous Focus RS, and worked really well.
The more I look at the system, the more I'm thinking the spring in the actuator is just too soft. I've ordered a 7.5psi actuator spring which will likely be a bit below that, so the boost controller will add the extra few psi with luck.

 

[leeds2592]

Let me know how you get on mate as I'll have this problem, I'd assume, with my maxpeeding churbo!

 

[Fishfire]

Let me know how you get on mate as I'll have this problem, I'd assume, with my maxpeeding churbo!

How are you controlling your boost and did you use the actuator that came with the turbo, out of curiousity?

The actuator provided on mine needed superman levels of strength to move and I'd have guessed it set was around 20psi at least, hence why I went to an adjustable one.

Porting the wastegate port is always a good idea on these too. Watched quite a few YouTube vids with people having spike issues due to the wastegate itself not being big enough.

I have ordered a heavier spring for the actuator but I'm off to Cyprus for for months as of Friday and I'm not expecting it before then tbh 😔

That said @SteveC_1879 has the same churbo, without porting and has no spikes 🧐 so I'm going to say it's very likely down to the actuator

 

[Yarp]

How are you controlling your boost and did you use the actuator that came with the turbo, out of curiousity?

The actuator provided on mine needed superman levels of strength to move and I'd have guessed it set was around 20psi at least, hence why I went to an adjustable one.

Porting the wastegate port is always a good idea on these too. Watched quite a few YouTube vids with people having spike issues due to the wastegate itself not being big enough.

I have ordered a heavier spring for the actuator but I'm off to Cyprus for for months as of Friday and I'm not expecting it before then tbh 😔

That said @SteveC_1879 has the same churbo, without porting and has no spikes 🧐 so I'm going to say it's very likely down to the actuator

Yep, this is true. The actuator that came with mine would settle at about 10psi. I binned it and used one from a z20let that I had kicking about that should open at 6/7 but was still holding 9. I gave up and “solved” it with a very small boost leak created by unblocking a 5mm T in the boost pipes and it now holds 8psi from just under 3k to the redline with no fluctuation at all.

 

[Hxrry]

I've just dropped my maxspeeding gt28 to a local turbo specialist, who's going to port the wastegate and check everything over for me. I'm glad I've had this done now seeing this post! Keep us updated with your progress!

 

[Fishfire]

Yep, this is true. The actuator that came with mine would settle at about 10psi. I binned it and used one from a z20let that I had kicking about that should open at 6/7 but was still holding 9. I gave up and “solved” it with a very small boost leak created by unblocking a 5mm T in the boost pipes and it now holds 8psi from just under 3k to the redline with no fluctuation at all.

If I remember correctly you have the 2860 rep? Mine has the larger 71 exducer so is a little later spinning up.
Starts making boost about 2800rpm and hitting full boost by 3800rpm ish.......comes in hard too

 

[Fishfire]

I've just dropped my maxspeeding gt28 to a local turbo specialist, who's going to port the wastegate and check everything over for me. I'm glad I've had this done now seeing this post! Keep us updated with your progress!

Porting is easy to do yourself tbh. I used a Dremel carbide tool.

Took a little while but almost doubled the size of the port, so I'm confident the boost spike isn't down to that.

Definitely a good call getting it done prior to fitting though. It's properly tight in there once it's installed and I'd not want to remove my turbo now unless I absolutely had to.

I built the engine up out the car too. How anyone does this with the engine in situe is beyond me!

And current wastegate actuator set up

 

[leeds2592]

How are you controlling your boost and did you use the actuator that came with the turbo, out of curiousity?

I'm not that far yet as the turbos still in the box whilst I get some other parts 😂.

Gotta be the actuator though as you've said. Hopefully the spring solves the issue.

 

[Adey.]

Spiking will be the actuator but its pretty inherent in all smaller turbos, you will struggle to eliminate it completely running manual control. Old school lag slag turbos have less of an issue as they spin up slower and things react faster. Modern ecu's have lots of strategies in place to pre-empt the over shoot and dial it back out using electronics. You could try a decent electronic boost controller along with a really good actuator.

Over shooting massively on spool up (boost spiking) is usually an actuator issue
Boost creeping, increasing massively with higher revs is usually the wastegate port itself being too small.

 

[Fishfire]

Spiking will be the actuator but its pretty inherent in all smaller turbos, you will struggle to eliminate it completely running manual control. Old school lag slag turbos have less of an issue as they spin up slower and things react faster. Modern ecu's have lots of strategies in place to pre-empt the over shoot and dial it back out using electronics. You could try a decent electronic boost controller along with a really good actuator.

Over shooting massively on spool up (boost spiking) is usually an actuator issue
Boost creeping, increasing massively with higher revs is usually the wastegate port itself being too small.

Pretty much what I thought 👍

Although I'm running a 2871 churbo which is bigger than the recommended 2560, So its a little slower to spool up.

I'll see how the heaver actuator spring responds in the actuator with one of my MBCs. I may well go to a Gizmo EBC in the near future.
I've had Apexi AVCRs and Blitz IBC controllers before, and you seem to need degrees in physics and mathematics to set the duty cycle correctly lol.....the Gizmo's are a simpler set up it seems.