M35 Stutter When Comming Off Boost (Bov?)

[Beregron]

Gday folks,

I rarely get the chance to boost my M35 due to where i live and the roads i drive frequently but on the weekend i had a chance to give it a bit and noticed that after coming off high / full boost at say... 120kmph+ the car stutters as i assume the bov attempts to vent excess pressure.

Would i be right to assume this may be due to the spring rate in my Turbosmart Kompact bov? I'm not 100% sure as i can come off high/full boost at lower speeds (say 80-90kmph which is all the roads around me generally allow) and it has no such problem. I can hear a slight stutter of air but it's fairly smooth. It appears as speeds get higher the stutter gets worse. Oh and i better mention that the car still runs stock boost.

I'm doing searches now to try see if anyone has reported something similar in the past (i asume they have). I probably would have picked this up sooner but i don't drive the stagea much on a day to day basis due to how far away from work i live and i rely on public transport.

Mods to my car are listed in my sig.

I'll have the car on the dyno in not the too distant future as i've sent a turbo off to Hypergear to be highflowed. Just thought i'd get opinions.

Cheers Beau

Edited May 6, 2014 by Beregron

[scotty nm35]

Yes, the Kompact could cause this, it's the very reason the stock BOV has the 4mm bleed bypass hole.

[skyguy3804]

Yeh as Scott said.. mine does exact same thing with Turbosmart Kompact BOV installed. I find it behaves better in tiptronic mode when on freeways, etc. when doing 100+ km/h. If you feather off the throttle it does stutter somewhat, but if you pull yr foot off quick it's alright. Hope those tips help!!

[Beregron]

Thanks Scotty. I'll give Turbosmart a call and see what they can suggest.

I did end up reading a bit about this in the M35 BoV thread so i'll read a bit more.

Cheers

[Daleo]

Is there room in the body of the BOV to drill a bypass port? You could start small (say 2mm) and go up from there?

[Beregron]

I'm in tiptronic mode 90% of the time i push the Stagea hard (it just makes sense) so perhaps i'm letting off too slow. I'll have a play around when i get the chance.

As for room for a bypass i'm not sure. I'll have a look. I wondered if the spring rate was a bit firm or not firm enough as i assumed the air being vented was causing the Bov to shut or stutter instead of just cleanly venting... perhaps i'll leave it in the hands of the bloke that ends up tuning it once i get it on the dyno.

[Beregron]

Turbosmart suggest trying a softer spring which is similar to what i have read in another thread...

Not sure thats gonna do much to fix or eliminate or if this is gonna compromise the ability to hold steady boost...

At least it's a cheap thing to test.

I'm more worried that it's doing some kind of long term damage

Cheers folks

Edited May 6, 2014 by Beregron

[WAGON_BOY]

mine does it all the time its the aftermarket BOV as it does not have bypass hole..... try turning the spring rate up a bit it might help, I noticed when mine was at its softest setting it was really bad.

[Beregron]

I'll give that a shot.

Cheers

[scotty nm35]

A softer spring should help, as will tuning the car.

[Lakes101]

Is the car running a stock ecu? How is able to be tuned if so?

[Beregron]

The car is running stock ECU at present but when i fit the turbo in the coming weeks i have a Greddy Emanage Ultimate and Greddy Profec B being fitted at the same time. I will also be picking up a fuel pump and injectors before having the car tuned.

cheers

[Lakes101]

Noice

[Beregron]

After tuning i'll see where the car is at and if i'm happy i'll start with cosmetics.

Mainly the front bumper as mine came with the factory parking aid which is terrible. I'll perhaps check Import Monster for a replacement stockish one.

I'm also still thinking about replacing the drivers seat but thats my last priority at this stage...

[scotty nm35]

I have a blue stock front bar here, I can't remember if it was undamaged though. I will have a look if you like.

Which tuner have you talked into tuning the EMU? I have heard the Adelaide tuners are scared of them...

[Beregron]

If you could please Scotty i'd appreciate it. I was going to sourse one of those nismo bars (i think they are nismo) that most people seem to go for but it's not a high priority.

I've talked to a whole heap of workshop south of Adelaide and only found 2 that will tune an EMU. Heinrich Performance in Lonsdale and another mob near Castle Plaza (i think they are called Turbotune). I've not had one of my cars on a dyno for the best part of 7 years but back in the day i use to use Boostworks but the bloke has moved up north which would be an hour and a half trip just for me to get there now.

I'm going to have a proper chat to the lads at Heinrich first and hopefully get an idea of thier work plus quotes once Stao has finished rebuilding the turbo.

[Brick]

If you could please Scotty i'd appreciate it. I was going to sourse one of those nismo bars (i think they are nismo) that most people seem to go for but it's not a high priority.

I've talked to a whole heap of workshop south of Adelaide and only found 2 that will tune an EMU. Heinrich Performance in Lonsdale and another mob near Castle Plaza (i think they are called Turbotune). I've not had one of my cars on a dyno for the best part of 7 years but back in the day i use to use Boostworks but the bloke has moved up north which would be an hour and a half trip just for me to get there now.

I'm going to have a proper chat to the lads at Heinrich first and hopefully get an idea of thier work plus quotes once Stao has finished rebuilding the turbo.

If htey haven't tuned an M35 before it may be worth a trip down to Melbourne to scotty's tuner. They are a special kind of special our M35s are

[Beregron]

I'm not totally against a nice drive to Melboure with the missus for a holiday.

Perhaps when i have all the bits ready in the coming weeks i might look at this as an options. I have almost 3 months leave accumulated at work that i'm looking for a reason to dip into.

Cheers

[DaveM35]

My GFB Bov has same issues, but it was barely noticeable on the highway with a tighter spring setting, I backed it off the other day (softer) and it was so much shitter. Just reinstalled my stock one after about 1yr with the GFB and it's SO much nicer to drive even if it boosts a tiny bit slower. I'll probably put the aftermarket one back on after f-con tune.

[Equilibrise]

I also have a Turbosmart bov, and previously had a Greddy one and both of them made the flutter noise quite often, although I believe the Turbosmart is a better unit. Some of you may already know about this; my recent discovery on this issue is that the stock pressure line to the bov has a restrictor in it and my logic was that restricting the pressure to the bov meant that it would be harder to open the firmer aftermarket spring resulting in the pressure backing up to the turbo which ultimately chops the air up making the flutter noise (not good for turbo's). I replaced this restricted line with fuel injection line yesterday and the result is soooo soooo so much better. The bov seems to be fully opening now when it is meant to...although, being an auto I still get the flutter in particular circumstances.