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Daddys little soldier!
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Discussion Starter · #1 ·
Right I have a 1999 Mk2 1.6 Intercooled turbo setup running at 8psi, managed by an EMB.

However on gearchange I get a chatter type noise from the induction side of the setup. From doing a bit of reading up I have sussed that this is probably backpressure at the turbo which is not a good thing, and I need a Blow Off Valve to realease the excess pressure. Anyone correct me on this?

I'm looking at putting the BOV before the inlet manifold in the silicone coupler between the IC pipe and the inlet manifold.

So what type of BOV do I need. Adjustable, recirculating, fixed? Whats best? Why would the previous owner not have fitted one. I'm a little confused. I've done some reading and I'm mechanically minded so don't be afraid of confuzzing me with jargon.

A search on here brought up very little on turbo setups just DTB's and SC's.

So whats best? Replies greatly appreciated.

Thanks,
Kirsty.
 

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at 8psi you certainly want one. At the 5psi many kits aim for, you don't.

your sticking it in the right place.

I went for a recirc myself. They work with airflow meters and offer the best performance. Other's have chose vent to atmosphere ones, which means using a twin piston type i believe. This is the best option if you want as much noise as possible.
Im not keen on sounding like a bus, or looseing any measureable performance from doing so. The recirc is a bit more plumbing though. You need to pipe the air from the valve back to between the flowmeter and turbo
 

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Randomer
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at 8psi a BOV is a good idea, helps prevent copressor stall/surge.
You're using EMB, so a recirculating bov would be ideal (just feed it back in post-airflow meter), otherwise you'll find the AFR's go very rich in between gear changes as the metered air is vented to atmosphere, however I have a similar setup and have found no ill effects from this.
if you want a VTA (vent to atmosphere) bov you may want to look at a sequential Bov like the HKS SSQV which should not leak any air at idle, other types of bov can (not always) leak a bit of air at idle, which may cause a lean idle (maybe the small issue I have...)
I've been using a Sard R2D2 twin piston style bov which seems to work quite well.

but mainly it's the noize! I found I picked the bov according to the noise it makes more than anything else:lol:
 

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fwiw I have the knockoff eBay SSQV on mine and it works fantastic. Took it apart before I fitted it to check the quality and it looks very well made inside. I am on M/S so I have it VTA, dont think it would work recirc as it has no flange on the output side. That said I dont know how much it is really an issue to go a little lean on the shifts with the afm system still in place anyway.

I will be at the meet next weekend so you can have a look at its placement and hear how it sounds. Totally a guilty pleasure really, its pretty loud, but I haven't got tired of it yet....

And yes at 8 psi you need one, and after the I/C, before the T-body seems to be the best spot. There is debate on the placement but this is what I see most people do.
 

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Daddys little soldier!
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Discussion Starter · #6 ·
Cheers peeps. Looks like all the helpful people were online last night.

Looks like I'll go for a recirculating type so I don't get idle problems.

I was discussing my car to one of my workmates today and he is adamant that it would be better to put the BOV on the turbo side of the intercooler as it is better to dump hot air that hasn't been put through the IC. However if the BOV was the recirculating type would I not just be putting the vented ar back into the same pipe it was vented from from?

I can't see what the difference is really. Perhaps I've not read up well enough on the subject. But as far as I'm concerned as long as it stops compressor surge/stall and any subsequential damage I'll be happy.

Now to find a not too chavvy noise. Not too bothered about sounding like a Imprezza but I would like a nice sound when I lift off the loud pedal.
 

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I've just got a Forge FMCL 007P/A re-circ dump valve - they tend to go for around ?120, but I got mine for almost half that price as ex-demo from ebay. It's a really nicely made bit of kit.
 

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think i run that one too. Only mine dont say forge, and came with the set of springs that forge call an optional extra. It was also about ?40 from ebay. seller called nicenewcar iirc.
sort of a pooosh noise, Not PSHh.
There are recordings of it and many others somewhere. Ive posted the link before.

ive seen them fitted both before and after. I feel as you do, that taking the uncooled air and sending it round n round the turbo is not good. i dont have a knock sensor though so im avoiding any chance of an over heated air charge. I also expect issues with responce times if its not right at the point where the pressure matters. And the intercooler acts as a bladder for ironing out boost spikes that might lead to problems if there acting upon the valve.
Its really not conclusive though. People will fight either corner. I tend to look to respectable cars though, and they almost all use recircs placed post cooler.
 

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dinky, basically the recirc or a VTA will behave the same in terms of idle stability - there will be no issues. the only difference between them is that the re-circ puts the compressed air back into the air inlet pipe (pre-turbo i think) and the VTA just dumps it, which is why you get the psst noise. im not really sure how much impact it will make if you don't recirc but instead dump the metered air, as when you lift off the throttle then you stop putting fuel in anyway, so it's not gonna have a massive rich spike, and even if it does, it's not going to matter.

all you need to make sure is that if you get VTA, it's a twin piston design which stops the car from stalling at idle. i'm not sure if you need a twin piston if you go for recirc, i guess as long as it re-circs to a point before the turbo but after the MAF meter it should be fine.

i've used baileys in teh past (DV 26 / 36 - these are VTA twin pistons), but am now using an ebay special SSQV copy. you have to be careful that the SSQV has the right adapter for the T piece (i've got my t-piece between I/C and manifold)
 

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Daddys little soldier!
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Discussion Starter · #10 ·
Cool thanks for everyone's advice. I'm going to have a search around and see what I can find for a reasonable price, although I'm not bothered about it being mega cheap if I can't find anything up to the job.

I'm sorting my manifold at the moment as it seems to be blowing at the flange between the manifold and the turbo.
 
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