I really don't like the BOV sound, even routed to the J pipe on. I was toying with the idea of putting the stock airbox back in and making a J pipe to plumb to it. Of course, I would have to put the stock IC pipes on as well, but I have heard that aftermarket pipes don't really do much for power anyway.

So, I can see that I may loose a little spool up respsonse and maybe a few HP, but if it makes the inlet noises quieter then I am not bothered. I know Guru sell a sleeper MAP kit that uses the stock air box. Does anyone know how much spool up / power I would be sacrificing with putting my stock airbox and IC pipes back on??

 

The stock airbox and filter is bigger and better than most of the "high performance" after market ones.
The weak link in the othervise stock system is the airflow meter, but I'm sure you have thrown that away a long time ago...

I had a K&N filter in my stock airbox until I noticed it's poor ability to do it's job, that's to filter some air... I put back the stock filter and didn't notice any difference in the cars performance. Well OK I don't have that much power either...
Maybe it makes a difference in a more powerful engine?

 

If you go this route, I would be willing to make a trade with you. I have the guru stealth look pipes and I'm looking to move towards something like what you have now. I would obviously have to give you some money along with the parts you would need in exchange for the pipes you are pulling out.

Let me know,

Justin

 

The airflow meter is not a weak link. You can flow a ton of HP through them.

 

I don't think they mean the AFM is restrictive as much as they mean weak link by being highly inaccurate (in many cases). The AFM itself is not the smalles effective flow area on the stock intake of a 951 IIRC.

 

Even if it is the smallest effective flow area. You can flow enough air for 100's of HP through it.

 

Agreed.
But tuning with an inaccurate measuring device can be difficult and harder to obtain even higher power numbers.

 

Agreed. Anyone ever have one fail or measure inaccurately? I have not had one for a while.

 

My AFM failed this past summer. It leaned out the car at part throttle. I knew something was wrong because the car failed emissions with very high NOx levels (and would ping at moderate boost). Danno pointed me at the AFM and I replaced it.

 

The stock AFM is ok, just not as effecient as MAF or MAP.

 

If you could ever make a VAF hit the maximum output voltage, it would be measuring near 700CFM. Due to the mechanical nature of the device it actually peaks around 500CFM. The VAF true cross section is equivalent to a 60mm MAF.

As far as choking performance, in first gear with the VAF I would see a max of around 11psi boost, with the MAF and cone filter it increased to 13psi (stock K26/8). At WOT in 4th and 5th gear, I measured 10% more flow with the MAF than I ever saw with the VAF.

 

I also have the Guru Stealth setup and once I get my wastegate on and coarse tune, I'll put it on the dyno and get some numbers. Though this may take around 2 weeks.

JustinL: With the Guru Stealth setup did you notice any increase in the turbo-spool noise? I thought that there would be a noticable increase in the spoolup sound but when I installed everything, it sounded like normal...Kinda dissapointed because thats what I wanted..

 

I am very happy with the stock AFM but I agree that it can be a weak link if it failes (mostly due to age).

 

I've noticed a mild increase in intake noise. The CBV is faint but audible and I don't hear much turbo whine at all. The biggest noise difference has been from the poping in the exhaust.

Justin

 

hahaha yeah popping from the exhaust! guess we need to tune more huh haha