Old FMII new BPV and intake side redesign. (stock MAF)
 

Allright, I thoroughly enjoy driving my 99 NB, but I've always wondered if the intake side at the turbo could be done better.

Here's a picture of the setup: (note: slightly old pic when we were building the car, but the intake side is the same.)

https://www.miataturbo.net/attachmen...ine=1319386774

As you can see the intake side is long, heavy (steel/iron?) and it has two 90 degree bends...
Now I don't want to switch to a new ECU just yet, I'm now using the Link Piggyback at 9psi. (this gives me around 235 engine HP with 93 octane)

Because of a slight problem/discomfort I had with the car 'juddering' when releasing the throttle rapidly at high rpm's (in boost) I started a thread some time ago:
https://www.miataturbo.net/general-miata-chat-9/1-8nb-old-fmii-judder-shudder-when-releasing-gaspedal-58956/

Now one of the possible solutions involved getting a new BPV. (i'm now using this: http://www.bellengineering.net/produ...roducts_id=126)

And why not change the intake side together with the BPV?

So basically this thread is about some questions I had:

- the BPV I was looking at was the TurboXS RBV-H34. This has the same 34mm inlets as my current BOV. (I think) So installation should be easy. I was looking at this one because I heard good things about the brand. It's also inexpensive at $130 and HOPEFULLY it's a bit louder than my current BPV, that would be awesome. :D Can you guys comment on this?

- For the intake side I'm still using the stock MAF sensor and housing, I'm looking at changing the whole bends and stuff. My miata is currently at the garage so I'm being a real noob here: What is the size of tubes I'm looking at to make it work? 2.5" 3"? (GT2554r turbo) Anyway, I was thinking along the lines of a 45 degree silicon bend, an aluminium T-piece for the BPV and then another silicon piece that goes on the MAF. (the maf has to be relocated for this of course) Any comments or info about sizes?

Oh and do you think this makes sense? Or isn't it going to make a difference in one of the three categories? (Less 'judder', more noise :D , power/spool) The BPV isn't that much work, but changing the intake layout is, kinda... If it doesn't really giving me anything in return, I'll leave it like this because the setup is pretty solid right now.

And, I'm being a noob again, do I need a new tune when I change the BPV and/or the intake piping length? (I guess so?)

Sorry guys, I tried to search but not being native American I'm always having a difficult time inserting a correct sentence/words into the search box,

Thanks!

Nobody here to point me into a direction? I'm not going to fight it! :ky:

wasted effort.

I clicked your link and watched the video, I dont hear your BOV at all...coupled with the shitty piggyback, that could be an issue. The intake pipes themselves look nice.

So you're probably feeling the compressor surge when you lift, as the blades sudden have to chop through the boost going back through the intake, then start to compress again.

Fix the BOV and report back.

Thanks, that saves me some trouble and money at the same time...
new BPV also wasted effort? (since I had that judder problem and stuff)

no, the BPV is most likely the issue.

Is it even hooked up?

Jep, fully hooked up. (at least to my knowledge) It is working perfectly fine when shifting, I can hear it blow too, in the video this isn't as pronounced as I hear it... Since it's a freaking small BPV, you can only hear it inside the car and on the passenger seat the sound is already more quiet... On the outside you can't really here anything. Just feels like it's not releasing it's air fast enough or something when I release my throttle.

Since a new BPV is relatively cheap and easy to install, I might give it a try. (CR fag alert) Is it possible that the TurboXS BPV gives me a louder sound?

I can't even hear the turbo spooling on that video, so it's poosible i just dont hear it.

I'm still not quite clear what the issue is, is the problem when releasing the throttle or when reapplying the throttle?

On Wednesday I'll try to make a new video and record sound better. That video was taken when it wasn't properly tuned yet.

Example of the issue (might be able to make myself more clear this way)
I'm going WOT and suddenly a kid runs across the street, I'm immediately taking my foot of the throttle. When I do this, it really feels like the car isn't liking this one bit... It 'judders' or something, hard to describe.

Example #2:
I'm going WOT and a corner comes up. I'm not going to shift into a higher gear right in front of a corner, I'm releasing my throttle. If I do this kinda fast, the car judders, like the car is telling me it doesn't like it when I release my throttle too fast.

It doesn't happen when I shift into higher gear, so that got me thinking it might be a transmission/driveline thing?

It's possibly just a setting on the LINK pulling too much fuel with a throttle lift.

Does it almost feel like you are getting thrown into your steering wheel?

Hmmm, not really, if I need to describe the feeling, for me it feels a bit like when you release the clutch way fast. You get a certain 'bounce/judder'

Since I only have the piggyback, my settings are quite limited.
In this manual: http://www.flyinmiata.com/support/in..._piggyback.pdf
In section 12 (starting page 24) I can't really see anything that could help me overcome my problem.