NA vs NB - Stock injectors and fuel pressure
 

Hey,

I though about the NA vs NB injectors and fuel pressure, I used to think that the NA and NB have about the same flow size injectors 254 vs 265 @ 3 bar, so they should support about the same boost. But lately I've found out that the NB fuel pressure is 4 bar, meaning the injector is running at 306cc so on the NB the stock injector can support a little more boost - I saw NB running almost 200whp on the dyno with stock injectors and stock pressure - now I understand why...

Just a though
Elior

Is this a question?

You forgot to enlighten us that NB is not vacuum referenced.

Do you see and question mark ?

And thank you for the remark.

I was only curious why this thread existed as it seems most never really care about stock injectors anymore. But hey, congrats on your revelation. ;)

Have you considered alternative drop in FPR to increase base pressure for stock injectors that will then be vacuum referenced?

This revolution came when I needed to setup an ECU for a turbo NB - the stock pressure was not 3bars like on my NA - so in order to get correct numbers from the ecu a correct fuel pressure is one of the parameters.

Wouldn't you agree that a stock 4bar pressure is uncommon ?

Not at all. 4 bar pressure is very common for returnless fuel setups. The difference is at 1 bar of positive boost pressure, the pressure differential over the injectors is now 3 bar. I believe in an NA, with the vacuum referenced FPR, the pressure differential is always 3 bar.

My head hurts.

NA is returnless and the NB is return (01-05).
NA 3bar
NB 4bar
Am I wrong ?

Yes.

NA is a vacuum-referenced return-style.
NB is non-vacuum returnless.

NA runs ~35psi at idle, and ~45psi at atmosphere, then 1:1 per psi after that.

this also makes sense since idle is about -10psi...

For the USA market that is.
NB 99-00 1.8 in EUDM still has a return line.
NB 01-05 1.8 in EUDM is returnless.
I do not know about the 1.6 NB EUDM, I think 99-00 still has return. 01-05 not sure.

Do you know if the EUDM NB 99-00 runs 3 or 4 bar, since it's return style?

My ID1000 is set to aprox 1200cc @ 4 bar in megasquirt.

Got a -00 EU market with returnstyle

All this tells is us what you set it to. Not what it actually is.

So,

He finally realized what we've all known since the late 90's?
And this is a discovery?
And this guy is a tuner?

LOL

Jeeez...

Yes the fp is 4 bar.
I think much of my tune would be fucked if I got these numbers mixed up...

No, because presumably you'd tune your VE table.

To put the thing you're missing about the manifold reference in more direct terms: it's not 4 bar in boost.

But it is not vacuum referenced

Exactly. Differential fuel pressure. Fuel rail is always at 4 bar. But when the manifold is at 1 bar, the injector only has 3 bar of pressure through it.