COMPRESSOR SURGE IN MY MTNTK AXYS TURBO KIT... AND WHAT TO DO?

[mountainhorse]

From the :30 second through :55 second mark in the video... the surge seems significant to me.

One thing I'd like to know is the differnece in sound with the EFR's between true 'surge/flutter' and normal noise for the CRV venting back into the inducer??

Another elemental difference is that the Ex Valves are pressure driven on the ProRide Chassis and servo driven on the Axys.... HMMM.

<iframe width="1000" height="563" src="https://www.youtube.com/embed/JNP7EqT3t68?rel=0" frameborder="0" allowfullscreen></iframe>




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[tangerine_sky]

One thing I'd like to know is the differnece in sound with the EFR's between true 'surge/flutter' and normal noise for the CRV venting back into the inducer??

That's a good question and also a point they brought up on the EVO forum when I asked about the EFR compressor surge.

But it comes back to the fact that it doesn't sound that way on the ProRide...

Another elemental difference is that the Ex Valves are pressure driven on the ProRide Chassis and servo driven on the Axys.... HMMM.

I don't know enough to determine in what way that would effect the amount of vacuum behind the throttle bodies, but that's a good point.

 

[mountainhorse]

I emailed the surge-sound/CRV-sound question to my contact at Borg with your video... We'll see if he replies.



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[tangerine_sky]

I just got a reply regarding the compressor surge from MTNTK. They said, "As for the compressor surge, it is not surging under load, only when you chop the throttle and the turbine does not have power to turn the compressor. The compressed air in the charge system exits BOTH through the re circulation valve on the compressor housing AND the compressor wheel. The Pro Kits did not have much chirp from the compressor wheel because the volume in the charge box is so small. On the Axys kit the charge box has 5 or 6 times the volume of the Pro and so the compressed air does not all exit the re circulation valve so the excess comes through the compressor wheel. If it was surging under load it would be a problem, but when it happens under zero throttle there will be no damage. In fact all turbo systems do it, but you can just hear it on a snowmobile with such an open intake."

If this is the case it sounds like the turbosmart 50/50 bov would work (assuming it blows off more air than the stock valve).

 

[mountainhorse]

I'm eager to hear about your results.


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[Shadydiesel]

BTW... Are you running the same boost levels on the two MTNTK kits you posted videos of?


First video is actually my sled, nothing special just waiting for some of the other guys in our group to catch up. I was running 7lbs at the time FWIW.

 

[tangerine_sky]

It didn't work. It sounds exactly the same.

The spring in the turbosmart BOV is about 3x heavier than the stock BOV spring. The fact that the sound didn't change even when the TS BOV is 50/50 vent to atmosphere leads me to believe that neither valve is ever opening.

It seems to function like the BD kits with no BOV. I am going to put a vacuum gauge on it tomorrow when I swap back to the stock BOV.

I was also seeing only 8 psi with the new BOV installed whereas when I initially set the wastegate spring I was seeing 8.5 psi, and I haven't changed it since. Not sure if it's related, but I'll find out tomorrow.

 

[mountainhorse]

And you had it adjusted all the way out and all the shims removed?




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[tangerine_sky]

there aren't any shims that I saw inside it. But I had it as soft as it would go.

 

[mountainhorse]

Info says it comes with 6 shims for the spring...was wondering if those were pre-installed.

Since you have it.... worth experimenting with it... trim the spring... have another go at it IMO.


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[mountainhorse]

The vacuum gauge is a good idea... see what vacuum you have with the throttle closed... and then... if you have a mightyvac... replicate that vacuum with both CRV's and see if you get any valve lift at the same vacuum you read ?

 

[TreeThrasher]

From my experience with setting up turbo sleds proper bov function is a must to get max performance out of a kit. Yes, it's less important when running small turbos that re light easily. But if a bov is working proper to allow the turbo to remain lit, it lets you run a size or sometimes two sizes larger turbo and have it light the same as a small turbo when tree riding.

You have a classic case of one of two things
1) your valve is not large enough to dump the charged pressure volume in the tube and box (which is unlikely btw) pressure equalizes through a small leak fast or
2) your valve is never opening. Typically I like to lighten the spring till the valve just lightly floats back and forth between closed and open at idle. The second you touch the throttle the valve should seat shut. Too light of spring and you build a transient issue when the throttle opens and valve remains open. Too heavy and it won't open. You don't have piles of vacuum to work with so spring tension is critical. You get a small vacuum spike when on boost and the throttle plate slaps shut. If sprung right that small spike in vacuum pulls the valve open, the turbo remains lit and when you crack the throttle plate back open, valve shuts and the party is right back on

Play with your spring tension imo

 

[mountainhorse]

Also wondering what is the ID of the vacuum reference and is it possible that the fitting on the reed side of the TB's is somehow restricted...or maybe has a undersized thru-hole in the fitting (not letting enough volume of air to move through the CRV reference hose??)





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[tangerine_sky]

Solved

I solved the compressor surge issue.

I put a vacuum gauge on the vacuum reference line in the reed cage. It was only pulling -1 to -2 InHg at idle and -3 to -3.5 InHg when chopping the throttle in the garage (track lifted, no load). I tested the stock bov and it started opening at -6.5 InHg. So I kept cutting coils and retesting to verify when the valve would start to open. Once I got it to open at -3 InHg I threw it on the sled and tested it. No compressor surge just straight pssh sound.

I'm going to take some video tomorrow for proof. It's running awesome.

 

[JJ_0909]

I solved the compressor surge issue.

I put a vacuum gauge on the vacuum reference line in the reed cage. It was only pulling -1 to -2 InHg at idle and -3 to -3.5 InHg when chopping the throttle in the garage (track lifted, no load). I tested the stock bov and it started opening at -6.5 InHg. So I kept cutting coils and retesting to verify when the valve would start to open. Once I got it to open at -3 InHg I threw it on the sled and tested it. No compressor surge just straight pssh sound.

I'm going to take some video tomorrow for proof. It's running awesome.

Which BOV is that from? Wouldn't mind trying this myself...

 

[tangerine_sky]

It's the stock EFR bov

 

[JJ_0909]

Sounds like we should be using supercharger BOV springs..ha

 

[mountainhorse]

If you still have it... it would be cool to get the TS valve to the same point... and have that adjustability to fine tune it in the field.



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[tangerine_sky]

If you still have it... it would be cool to get the TS valve to the same point... and have that adjustability to fine tune it in the field.
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I do still have it and I have the soft spring on order.

In the mean time it's functioning correctly with the stock CRV now. Here is a short video comparing before and after the spring mod on the stock CRV.
<iframe width="1000" height="563" src="https://www.youtube.com/embed/PRF6WLbwFd0?rel=0" frameborder="0" allowfullscreen></iframe>
https://www.youtube.com/watch?v=PRF6WLbwFd0

 

[mountainhorse]

NIGHT AND DAY!!!

Nice work my friend !!!

Confirming that the CRV is staying closed when it is supposed to... is the task at hand now!






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