[Nezil]

I've not seen many people post about fitting a DV+ with the stock N55 M2 turbo, but based on a suggestion from SeanWRT, I decided to give it a go with the Main Spring installed because my car is 6MT, and the boost drop off between shifts frustrates me.

Fitting was not difficult, but annoying. I was hoping to avoid removing the stiffening plate because the bolts are torque to yield and should be replaced EVERY time and not re-used, and this obviously adds to the cost if you're replacing these. Unfortunately you really do need to remove the stiffening plate, and the FMIC and boost pipe to get access to the bolts holding the diverter valve onto the Turbo.

I tried not buying any new tools because I have quite a lot as it is, but that top bolt really is in an awkward place because there is an oil line going into the block that stops you being able to get a hex into it straight. I ended up mangling the head a little trying to use a Torx bit rather than the correct tool (a ball end hex), before heading out to pick up a selection of 1/4" drive parts and ball end hexs. In the end, a 3/8" drive long reach 5mm ball end was what got it out (and back in again), but it wasn't easy.

The DV+ assembles easily, and holds together as you fit it in place. As with removal, the bottom two bolts are easy to fit in place; the top one, you cannot even see! I must have dropped the top bolt on my face about 20 times before I finally got it in the hole, but now that I had a 5mm ball head hex it actually screwed in without to much difficulty.

All of this work was done on a QuickJack by the way.

[Nezil]

And so... what do I think of the DV+ now that it's installed?

I was hoping it would eliminate turbo lag between shifts under hard acceleration... and it doesn't.

What it appears to do though, is to hold some level of boost in the FMIC / Induction piping, which results in much better throttle response at part throttle, and some reduction in turbo lag under hard acceleration.

I believe the way it works is to prevent high pressure spikes when you come off throttle, but maintain some amount of pressure in the system to reduce the amount of spool up required for requested boost again.

My observations would make sense if my understanding is correct because at part throttle, and shifting below 4k RPM, boost is low anyway, and if that pressure is maintained, you'll feel much better response when you get back on (part) throttle.

Overall, for $150, it's a nice addition. It does improve throttle response quite a lot, but it's at the low boost / rev range that it really makes a difference, rather than the top, which is what I was hoping for.

[M-Supra]

Originally Posted by Nezil

I've not seen many people post about fitting a DV+ with the stock N55 M2 turbo, but based on a suggestion from SeanWRT, I decided to give it a go with the Main Spring installed because my car is 6MT, and the boost drop off between shifts frustrates me.

Fitting was not difficult, but annoying. I was hoping to avoid removing the stiffening plate because the bolts are torque to yield and should be replaced EVERY time and not re-used, and this obviously adds to the cost if you're replacing these. Unfortunately you really do need to remove the stiffening plate, and the FMIC and boost pipe to get access to the bolts holding the diverter valve onto the Turbo.

I tried not buying any new tools because I have quite a lot as it is, but that top bolt really is in an awkward place because there is an oil line going into the block that stops you being able to get a hex into it straight. I ended up mangling the head a little trying to use a Torx bit rather than the correct tool (a ball end hex), before heading out to pick up a selection of 1/4" drive parts and ball end hexs. In the end, a 3/8" drive long reach 5mm ball end was what got it out (and back in again), but it wasn't easy.

The DV+ assembles easily, and holds together as you fit it in place. As with removal, the bottom two bolts are easy to fit in place; the top one, you cannot even see! I must have dropped the top bolt on my face about 20 times before I finally got it in the hole, but now that I had a 5mm ball head hex it actually screwed in without to much difficulty.

All of this work was done on a QuickJack by the way.

I've removed my stiffening plate a minimum of 50+ times, used same bolts and simply run back in till tight with cordless driver, I think your concerns are unfounded

2018 M2 with over 48K hard miles

[Nezil]

Originally Posted by M-Supra

I've removed my stiffening plate a minimum of 50+ times, used same bolts and simply run back in till tight with cordless driver, I think your concerns are unfounded

2018 M2 with over 48K hard miles

I don't disagree that this might be overkill, but here is where I found the info:

And given that these are torque to yield, as evidenced by the torque + angle requirement, there is a good reason for replacing them, which is discussed better than I could, here: https://user.xmission.com/~kd7olf/torque.html

I'd hate for someone to damage their subframe by either repeatedly running previously stretched bolts into the captive nuts damaging the threads, or snapping off a stretch fatigued bolt in the subframe.

One thing I would say, is that if you do re-use the bolts, and try to torque them as ISTA+ states, you'll only be able to get the 90 degrees of angle specified a couple of times before the bolts are all stretched out, and have no stretch to give... The only thing you might be able to do is fit them to a much lower torque without the stretch, and this you could probably do many many times.

By the sounds of it, you're not torquing your bolts as much as the ISTA+ document states, and just "running back in 'til tight" with a cordless driver. I'm sure this is fine in practice, and even driving without the stiffening plate probably wouldn't cause a problem, but it's not what ISTA+ says, and that's why I posted my comment.

[M-Supra]

Originally Posted by Nezil

I don't disagree that this might be overkill, but here is where I found the info:

And given that these are torque to yield, as evidenced by the torque + angle requirement, there is a good reason for replacing them, which is discussed better than I could, here: https://user.xmission.com/~kd7olf/torque.html

I'd hate for someone to damage their subframe by either repeatedly running previously stretched bolts into the captive nuts damaging the threads, or snapping off a stretch fatigued bolt in the subframe.

One thing I would say, is that if you do re-use the bolts, and try to torque them as ISTA+ states, you'll only be able to get the 90 degrees of angle specified a couple of times before the bolts are all stretched out, and have no stretch to give... The only thing you might be able to do is fit them to a much lower torque without the stretch, and this you could probably do many many times.

By the sounds of it, you're not torquing your bolts as much as the ISTA+ document states, and just "running back in 'til tight" with a cordless driver. I'm sure this is fine in practice, and even driving without the stiffening plate probably wouldn't cause a problem, but it's not what ISTA+ says, and that's why I posted my comment.

I'm not saying your wrong, I'm just implying that these aren't head bolts or rod bolts, they are just mounting bolts for a plate and the number of them gives plenty of leeway for any erroneous tightening

Crawling under her now to pull plate and inspect turbonium and do a quick oil change, my girl is a test mule

[SeanWRT]

You can log and compare with old logs on boost on shifting.

Manual car normally loses a lot of boost with shift, but DV+ can help hold some or at least so it should. ZF 8 speed auto benefits a lot from it shown from log.

BTW, do you hear extra noise from the partially open valve on throttle lift?

[Nezil]

Originally Posted by SeanWRT

You can log and compare with old logs on boost on shifting.

Manual car normally loses a lot of boost with shift, but DV+ can help hold some or at least so it should. ZF 8 speed auto benefits a lot from it shown from log.

BTW, do you hear extra noise from the partially open valve on throttle lift?

Yeah, I will try and get some logs in the next few days. The car definately feels more responsive on and off throttle, particularly part throttle, as I said. I noticed today when I was getting ready to pass someone, in third gear went for it then back out and came off the gas for about a second, when I went for it a second time, there was no lag at all... much better than before.

No change in noise that I can hear obviously. It's still winter here though, and California this year is unusually cold and wet, so I've not had the windows down like I do in the warmer months. I'll comment again if it gets warmer and I notice any different induction sound. I am running the stock intake and filter though, so it's probably muffled a bit anyway.

I realise the DV+ is a small change, but it's also cheap. I'm surprised more people aren't installing it as a low cost bolt on option, particularly for 6MT and 8AT as you said. Most people only think of it as an upgraded DV for extra boost, but with the main spring... it's so much more than that. I'd actually think it's worthwhile installing the main spring with DCT because it's not only gear shifts that have you on and off throttle.

[Nezil]

What I mean is... I often hear about the DV+ being installed when a Turbo upgrade is being done. I'm finding, and you suggested it beforehand SeanWRT, that there are significant benefits with a stock turbo; it's not simply an upgraded (i.e. stronger) unit.

[SeanWRT]

Originally Posted by Nezil

What I mean is... I often hear about the DV+ being installed when a Turbo upgrade is being done. I'm finding, and you suggested it beforehand SeanWRT, that there are significant benefits with a stock turbo; it's not simply an upgraded (i.e. stronger) unit.

Thanks for letting me know that DV+ isn't that noisy with stock intake. Many reported extra noise indeed are fitted with aftermarket intake.

M2 has the N20 DV from factory (20~22psi rated) and thus is in less need for the DV+ upgrade in terms of valve failure. But the true reason why not more people are using it is the difficulty of install. It's even not an easy job (to the average mechanic) with turbo taken off. I've really admired those that's DIY capable, because I am not

Throttle response alone with MT justify the cost of 125USD to me.

[ORG]

I would upgrade if I didn't have to take off the intercooler. The weight of the CSF was hard to manage when installing, and I needed an extra hand.

[David.m]

I find if I hold WOT passed 6K rpm there is no noticeable lag on upshifts, change under 6K and it's like the engine needs a second to think when the accelerator peddle is back on the floor. This is the 1st computer controlled (& turbocharged) sports car I've had, was very frustrating as I thought it was turbo lag and/or traction control causing the delay.

[Nezil]

Originally Posted by ORG

I would upgrade if I didn't have to take off the intercooler. The weight of the CSF was hard to manage when installing, and I needed an extra hand.

I didn't write it above, but I hear you... Fitting the CSF is a bitch because of the weight. I did it on my own, but there was some bad language coming from my mouth while I did it, and aching arms after!

[Nezil]

Originally Posted by David.m

I find if I hold WOT passed 6K rpm there is no noticeable lag on upshifts, change under 6K and it's like the engine needs a second to think when the accelerator peddle is back on the floor. This is the 1st computer controlled (& turbocharged) sports car I've had, was very frustrating as I thought it was turbo lag and/or traction control causing the delay.

Yes, you're right, and it is turbo lag. There is no pressure in the induction piping any more, and it has to be built up again before you get boost pressure.

The DV+ basically eliminates this under ~3.5k rpm, and reduces it above that. It's not just between shifts either, it's every time you take your for off the gas. Because of this, I believe it's a big improvement for DCT cars as well. They have no problem between shifts, but they do if you're on and off the gas in gear.

Frankly I'm really impressed with the difference the DV+ makes. It might be different from what I was expecting, but it's a good improvement all the same, and a bargain at $150!

I agree there is basically no lag if you shift that late, but this only contributes to the Jekyll and Hyde / Bipolar nature of the M2, a characteristic that I've always been unhappy with. I want a fast car all the time, not only when I'm hard on it. I found the stock M2 annoyingly slow in Comfort mode part throttle, but pretty fast when you revved it out. Coming from a NA 5.0 V8, this frustrated me.

My mods so far have changed all that. The only thing missing now is top end power, and I know I'm fuel / octane limited currently. I think upgrading the hpfp (so I could run more E85), Pure stage 2 (to reduce temps and stress) and a custom map would fix that, but it's out of my budget for the short term at least.

[BruceM]

Well, based on this thread I'm going to give this a shot. I have one, I just haven't tried to install it. And based on this description, I think this is a job for my local wrench. I have the Dinan turbo, too, so maybe I'll get what Nezil did, but a little more so. Which would be fine with me. It is interesting to track Nezil's impressions over two days. The first one was pretty guarded and a bit meh. But after a couple of days it seems to have grown on him--enough for me to call my wrench and try to book some time for an install.

[Bee Pee]

Originally Posted by David.m

I find if I hold WOT passed 6K rpm there is no noticeable lag on upshifts, change under 6K and it's like the engine needs a second to think when the accelerator peddle is back on the floor. This is the 1st computer controlled (& turbocharged) sports car I've had, was very frustrating as I thought it was turbo lag and/or traction control causing the delay.

Originally Posted by Nezil

Yes, you're right, and it is turbo lag. There is no pressure in the induction piping any more, and it has to be built up again before you get boost pressure.

The DV+ basically eliminates this under ~3.5k rpm, and reduces it above that. It's not just between shifts either, it's every time you take your for off the gas. Because of this, I believe it's a big improvement for DCT cars as well. They have no problem between shifts, but they do if you're on and off the gas in gear.

Frankly I'm really impressed with the difference the DV+ makes. It might be different from what I was expecting, but it's a good improvement all the same, and a bargain at $150!

Guys,

Your feedback makes sense and validates what I've heard/read about OEM DV and why adding main spring to GFB DV+ is the way to go.

My understanding is that oem DV can start to "flutter" at higher boost pressures - ie above 17-18psi - typically what can be seen in the N55 low/mid range. Moderate fluttering can cause the part- or full-throttle hesitancy you both refer to.

If flutter increases then this can trigger DME to reduce boost etc.

GFB DV+ c/w main spring removes the flutter completely which should mean sharper throttle response and more consistent building/holding of boost at part or WOT. I have one to install on my M2 DCT.

BP

[M-Supra]

Originally Posted by SeanWRT

Thanks for letting me know that DV+ isn't that noisy with stock intake. Many reported extra noise indeed are fitted with aftermarket intake.

M2 has the N20 DV from factory (20~22psi rated) and thus is in less need for the DV+ upgrade in terms of valve failure. But the true reason why not more people are using it is the difficulty of install. It's even not an easy job (to the average mechanic) with turbo taken off. I've really admired those that's DIY capable, because I am not

Throttle response alone with MT justify the cost of 125USD to me.

Sean, you can do it, you just have to dive in, its the best way to "KNOW" your car and how it all functions. I love doing mechanical work and the joy it brings knowing I saved moolah and the pride of fixing/modifying myself, lots of peeps here to help each other through tasks they may not understand yet. I'm trying to learn tuning, that's an entirely different game and you are helping me.

[chris719]

Originally Posted by Nezil

Yes, you're right, and it is turbo lag. There is no pressure in the induction piping any more, and it has to be built up again before you get boost pressure.

The DV+ basically eliminates this under ~3.5k rpm, and reduces it above that. It's not just between shifts either, it's every time you take your for off the gas. Because of this, I believe it's a big improvement for DCT cars as well. They have no problem between shifts, but they do if you're on and off the gas in gear.

Frankly I'm really impressed with the difference the DV+ makes. It might be different from what I was expecting, but it's a good improvement all the same, and a bargain at $150!

I agree there is basically no lag if you shift that late, but this only contributes to the Jekyll and Hyde / Bipolar nature of the M2, a characteristic that I've always been unhappy with. I want a fast car all the time, not only when I'm hard on it. I found the stock M2 annoyingly slow in Comfort mode part throttle, but pretty fast when you revved it out. Coming from a NA 5.0 V8, this frustrated me.

My mods so far have changed all that. The only thing missing now is top end power, and I know I'm fuel / octane limited currently. I think upgrading the hpfp (so I could run more E85), Pure stage 2 (to reduce temps and stress) and a custom map would fix that, but it's out of my budget for the short term at least.

Are you sure this isn't some kind of DME thing or torque management?

[Beyond Help]

Ill be installing a PS2 once my hpfp arrives & weather gets better. Looking to do the DV+ upgrade but I saw a post that having it installed with the main spring @ higher boost levels it throws a silent code related to the DV and there is minimal power loss. Does anyone have any info on that?

https://f10.5post.com/forums/showthread.php?t=1266033

[BruceM]

Originally Posted by Beyond Help

Ill be installing a PS2 once my hpfp arrives & weather gets better. Looking to do the DV+ upgrade but I saw a post that having it installed with the main spring @ higher boost levels it throws a silent code related to the DV and there is minimal power loss. Does anyone have any info on that?

https://f10.5post.com/forums/showthread.php?t=1266033

Well, that would be disturbing. But its seems the OP here clearly hasn't noticed this phenomenon on this application.

[widetyres]

@Nezil - cheers for this post. I'm interested in doing this too when I replace my intercooler and piping, so it's nice to hear about what to expect.

Bit worried about the silent CEL's though - please can you check you car?

[M Fifty]

The reinforcement plate appears to be structural, so rather like the dire warnings on the E46 about not even moving the car with the plate removed, probably best not to drive the car without it being fitted.

I would note that the E46 felt much better over the granite sets in the roads around where I live with new bolts done up to the correct setting (59Nm +90 +30) compared to used bolts set to 59Nm.

[Nezil]

Originally Posted by widetyres

@Nezil - cheers for this post. I'm interested in doing this too when I replace my intercooler and piping, so it's nice to hear about what to expect.

Bit worried about the silent CEL's though - please can you check you car?

Yes, will do. I have ISTA+ and E-Sys. I guess ISTA+ is the one to use to check this.

I can say that it doesn't feel down on power at all, but I agree... Best to check.