does my intake suck (or is it my tune)?
 

so this is something that has been bugging me for quite some while now: compared to what I see on other people's maps, my normally aspirated VE figures seem to be significantly lower. I'm running a '03 VVT engine, flat-top intake header, stock 4-2-1 exhaust header attached to a 200 cell cat and a BBK catback silencer (absorption type, not reflecting type). My intake consists of an open cone filter (Vibrant), a 45° silicone elbow, some 2.5" aluminium piping and another 90° silicone elbow attached to the throttle body. I was wondering if my intake and/or air filter is causing to much restriction?

1 caveat: Due to altitude (500-600 m above sea level; 1640-1970 ft.) I never really see MAP readings above 94 kpa.

Today I was auto-tuning once again. This time around it was cooler (MAT 21-25° C) but rainy. (MAT correction was set to 100% to prevent interference, but I kept a close eye on MAT)

https://www.miataturbo.net/attachmen...ine=1464732637current VE and AFR tables
https://www.miataturbo.net/attachmen...ine=1464732637VVT table was taken from DIYautotune.com

The VE on US-NBs goes up with MAP because they run static fuel pressure at the rail. So the higher the absolute pressure in the intake, the lower the pressure difference across the injector and therefore you get less fuel flow at the same opening time. MS doesn't correct for that by calculating reduced flow numbers, but by artificially increasing VE.

So if you're running static fuel pressure, something may be wrong with your engine. If you're running a return-style system, you're probably OK and there's nothing to worry about.

Edit: I read in another thread that European NBs have return-style fuel delivery. So you're probably OK.

Schoene Gruesse aus den USA.

Danke Stefan! Matter of fact I'm running an NA fuel system since the engine was dropped into a '91 MX5.

Maybe I have to play a little bit with my VVT advance. There was one guy who had better numbers with more VVT advance towards the top RPMs

Am I wrong by thinking higher VE numbers mean moar powarrr? (given AFR and spark weren't changed, and MAT is the same as before)

That would give me a possibility to road-tune my VVT table then?

Has anyone made an 'intake sucking' pun yet? No? ok

VE numbers don't mean a lot. If you move the reqd. Fuel in either direction, your map would have to change to compensate.

;)