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

tangerine_sky · Jan 1, 2017

Why do the axys kits seem to get so much compressor surge?

I get as much compressor surge on my MTNTK kit as the boondocker kits. And they don't even have BOVs.

I've watched youtube videos of the 11-15 pro kits and there is no compressor surge at all on those, where as, on every MTNTK axys kit you can hear it.

Was wondering what people have tried to eliminate it?

Moderator Note: I separated this conversation from the other thread to keep that one on topic and explore this one more in depth with its own thread.

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mountainhorse · Jan 1, 2017

Lots on your topic in the other thread.

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fastgas · Jan 1, 2017

My take on this is that for a 2 stroke, you don't have as much intake vacuum (due to crankcase being pressurized each cycle) as on a 4 stroke so BOVs aren't as effective. You can use a very light spring, but it will sometimes be partially open at idle, or overly sensitive so you lose responsiveness (since it will be open or still trying to close when on/off throttle and trying to build boost). Therefore I don't thinks BOVs are as effective on 2 strokes - unless you use something more intelligent like a fast acting electronically controlled BOV, but I think the complexity/cost would outweigh the benefits (would be a fun project to try someday...) - turbos made for automotive use are built to last a very long time, so I don't think surge will significantly shorten their life, and responsiveness doesn't seem to suffer much on 2 strokes.

I haven't noticed any difference between the Axys and earlier models except maybe in the way the turbo kit works or placement of the intake.

gmustangt · Jan 2, 2017

BOV's / CRV's operate more on pressure differential than vacuum.

fastgas said:
My take on this is that for a 2 stroke, you don't have as much intake vacuum (due to crankcase being pressurized each cycle) as on a 4 stroke so BOVs aren't as effective. You can use a very light spring, but it will sometimes be partially open at idle, or overly sensitive so you lose responsiveness (since it will be open or still trying to close when on/off throttle and trying to build boost). Therefore I don't thinks BOVs are as effective on 2 strokes - unless you use something more intelligent like a fast acting electronically controlled BOV, but I think the complexity/cost would outweigh the benefits (would be a fun project to try someday...) - turbos made for automotive use are built to last a very long time, so I don't think surge will significantly shorten their life, and responsiveness doesn't seem to suffer much on 2 strokes.

I haven't noticed any difference between the Axys and earlier models except maybe in the way the turbo kit works or placement of the intake.

tangerine_sky · Jan 2, 2017

MTNTK 11-15 pro rmk kit

MTNTK axys kit

You can see the difference. It seems like the EFR dv is not functioning correctly on the axys.

I'm not sure if it's not seeing enough vacuum from the port in the reed cage or if the standard spring in the EFR dv is too stiff.

Ideally I'd want to block the stock EFR dv port and install a synapse dv between the compressor and the charge box, but I'd need a custom made silicone elbow with a 1-1.25" port built into it.

mountainhorse · Jan 4, 2017

tangerine_sky said:
MTNTK 11-15 pro rmk kit

You can see the difference. It seems like the EFR dv is not functioning correctly on the axys.

I'm not sure if it's not seeing enough vacuum from the port in the reed cage or if the standard spring in the EFR dv is too stiff.

Ideally I'd want to block the stock EFR dv port and install a synapse dv between the compressor and the charge box, but I'd need a custom made silicone elbow with a 1-1.25" port built into it.

Maybe try the TurboSmart adjustable recirc/BOV valve that bolts on?
That would be the easy cheap way to find out IMO.

From a previous post:

mountainhorse said:
Yea, BW made it super simple to add a turbo speed sensor with the EFR line of turbos.

You would have to also have a data logger to interpret speed info within the window of BOV/CRV operation and the relationship in a graphical manner. Would the BD controller that comes with the MTNTK unit be able to output logs or would another module be needed?

It would be cool if Turbosmart also offered their adjustable dual-port CRV for the EFR's in a non vented design to return all BOV flow back into the inducer.

The 'dual port' references that besides venting back to the inducer, it also vents to atmosphere to give the woosh sound, not that the sound is a big deal to me... I wonder if this external vent would affect recovery time with such a low inertia rotating assembly of the EFR's. We don't have to worry about venting affecting the fuel system as sleds don't have MAF sensors.

Would be cool to fit this little sukker on the MTNTK kit as it would be easy to dial up or down the CRV spring pre-load.... with just a twist to fine tune.

Also... with a low boost system... and the relatively low lb/min demand of a CFi2 800 running at say 3-lbs at sea level (17.7PSI MAP). I'd really like to see MTNTK make a super simple NON intercooled system with the EFR that can keep the complexity and cost down. No intercooler, no extra tunnel cooler etc...

At that level of boost... we've seen systems that can provide ample power, in the 190hp range, at '3 lbs' on pump fuel and no fuss. That is adding about 50% more HP at elevation than other NA sleds. Pretty darn great IMO.... Keeping in mind that a stock naturally aspirated engine is making maybe 110-120 hp at 10k feet.

Pretty amazing what a properly sized, properly clutched, well controlled '3 lb' kit can do on the mountain.

Now that is a kit I'd like to see.!!

Sure, being able to add more boost is nice, but that also adds complexity with more components needed, and most likely will change throttle response....

If MTNTK can supply a kit with intercooler and additional tunnel cooler... for about $4000 USd ... what kind of price could they offer on a simpler '3 lb' complete system??

BTW: For those wondering EFR stands for "Engineered For Racing"(thx Tory) ... A marketing term that BW (Borg Warner) came up with... they wanted to combine features, technology and aesthetics into a nice aftermarket package. The EFR's come standard with Stainless steel turbine housings and have available, as an option, aluminum center sections to keep weight down.

Looks like Ford is incorporating many of these EFR features into their BW turbos in EcoBoost engines... I believe that the Focus-RS uses a BW EFR type of turbo in the factory offering... that Lightweight turbine really is THAT big of a deal !

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mountainhorse · Jan 4, 2017

For others reading this.

Everytime you hear the surge/chatter... you are slowing, to a degree the, the turbos rotating assembly.

Now... This is NOT a bash to the MTNTK kit which, according to the reports is awesome...but just in the method that people are playing with their clutching to get the most they can out of the kit.... minimizing surge is a method as well IMO.

Heres a basic video description that I posted on another thread
<iframe width="400" height="225" src="https://www.youtube.com/embed/FwzUffAuQyc?rel=0" frameborder="0" allowfullscreen></iframe>

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tangerine_sky · Jan 4, 2017

I was originally going to try the dual port turbosmart CRV until I read that it wasn't so great.

When I asked about the Turbosmart CRV on an evo forum where a lot of people are running EFR turbos (boostedforums.net) here's the response I got, "I tried both the internal and 50/50 TurboSmart valves for the EFRs and they both fluttered more then the stock EFR valve. I've have good success with the EFR heavy spring."

Now they are running a lot more boost than we are which is why the heavier spring might have worked for him, but it generally sounds like the EVO guys don't like the turbosmart valves.

mountainhorse · Jan 4, 2017

A lot of the flutter on the automotive stuff is from large turbos coupled to high volume intake tracts...
And I doubt that any automotive application has anywhere near as much transient throttle action as a sled rider sees all the time.

Also if it surged MORE than the stock with the TS valves... he's running too stiff of spring and/or preload on his setup IMO.

For the price...The TS valve is worth a try IMO.

Being able to dial it back on your MTNTK setup may help with all of that surge in your video.

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

Lots of chudder on that side hill !!
<iframe width="1000" height="563" src="https://www.youtube.com/embed/JNP7EqT3t68?rel=0" frameborder="0" allowfullscreen></iframe>

Saw some new R&D stuff from Warner in the works for turbos in general.... cool stuff from the control side of things... and not long before we start to see it in our sled stuff.

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Davajn · Jan 4, 2017

Does that TS blow-off valve bolton the compressourhousing without modifications? If so then i might give it a try.

tangerine_sky · Jan 4, 2017

Davajn said:
Does that TS blow-off valve bolton the compressourhousing without modifications? If so then i might give it a try.

Yes it does.
The only problem I see is: we only have 2.5" of space from the CRV mounting flange to the intake tract. So the dual port TS BOV might not fit, without the banjo fitting factored into height it's 2.32".

Davajn · Jan 4, 2017

Yeah but that is from the bottom of the blowoff valve that goes into the housing. If you measure from the flange it might be less then 2.5"

mountainhorse · Jan 4, 2017

I agree... worth an email to turbosmart for a measurement.

Scaled from the drawing... I come up with 2.1" from the flange to the top of the banjo bolt.

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Spaarky · Jan 4, 2017

Why are you guys SO worried about a little surge. BD has no BOV and surges all the time... They work awesome. Couple of the other kits have BOVs but don't work adequately .... They have surge. Doesn't seem to be a issue over there.

I have been around or running turbos since late 90s. We have spent 100's upon hundreds of hours trying to make them absolutely perfect. I have spent way too much money on making sleds run perfect.

I have came to one conclusion. If I would have spent all that time and money riding......or put more effort into riding, I would have been way further ahead.

Pick a kit.... Put it on. Ride the crap out of it.

tangerine_sky · Jan 4, 2017

mountainhorse said:
I agree... worth an email to turbosmart for a measurement.

Scaled from the drawing... I come up with 2.1" from the flange to the top of the banjo bolt.

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Awesome, I will probably order that and give it a shot then.

Spaarky said:
Why are you guys SO worried about a little surge. BD has no BOV and surges all the time... They work awesome. Couple of the other kits have BOVs but don't work adequately .... They have surge. Doesn't seem to be a issue over there.

I have been around or running turbos since late 90s. We have spent 100's upon hundreds of hours trying to make them absolutely perfect. I have spent way too much money on making sleds run perfect.

I have came to one conclusion. If I would have spent all that time and money riding......or put more effort into riding, I would have been way further ahead.

Pick a kit.... Put it on. Ride the crap out of it.

Now I agree with you on not stressing the small stuff and just ride, but being an engineer and an efficiency stickler it's hard when you see other kits running with zero surge.

Check out the Impulse turbo kit with Tial QRJ BOV, absolutely no compressor surge.

Now if there is a simple way to eliminate it on the MTNTK kit I will try it. Otherwise, I'll leave it for a summer project.

Spaarky · Jan 4, 2017

There is a simple way to have less surge. KEEP THE FOCKER PINNED!!!!

Seriously though. I love the Impulse stuff and am a huge performance guy. If I had 7-8 grand to put into a kit, it would be a Impulse. Most guys don't!!! Here is the kicker.....

Most guys do not have the seat of the pants feel to notice the compressor surge or no surge. Especially not a $4,000 difference.

mountainhorse · Jan 4, 2017

I hear ya Justin...and in the same breath you/we are always looking for that last 'smidge' of performance from clutching, or spark plugs, or ... that many would also argue is splitting hairs too.

With the ultra low mass/inertia of the EFR's (less than half the turbine weight of the best inconel turbine).... surge will affect this turbo more than others... And I do believe that there is something to be gained from minimizing surge in these sleds...

My 2¢... IMO

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mountainhorse · Jan 4, 2017

For me Tangerine... the kicker is the stark contrast of surge levels in the two kits (ProRide vs. AXYS) with the same turbo spec.

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Spaarky · Jan 4, 2017

Spark plugs and clutching are easy.... Especially when Tony is on your side...... When I can follow Travis or Tory in their tracks for a day, I will move onto compressor surge.

tangerine_sky · Jan 4, 2017

mountainhorse said:
For me Tangerine... the kicker is the stark contrast of surge levels in the two kits (ProRide vs. AXYS) with the same turbo spec.

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This is what I'm having a hard time wrapping my head around. Not really sure why that is.

That's why I was hypothesizing that maybe the CRV is seeing less vacuum on the Axys. Maybe with the addition of the charge box/intercooler has increased charge side air volume enough that it's harder to relieve quickly enough for the stock CRV.

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

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