Thread: JWT ECU Re-tune??

Yes, you are correct. STIs are 520cc @ 3 bar. The tune is for 4 bar. On the phone, I told him 520cc@4bar and he said, that's 605cc@4bar. I said, yes, technically 520cc @ 4 bar = 605cc, but I want to use 520cc injectors @ 4 bar, then he said ya [email]605cc@4bar....Kind[/email]a got into a car geek semantics argument lol.

So I'm pretty sure it's 520cc @ 4 bar, it's just listed as 605cc which is what 520cc @ 4 bar equals..confused yet? I assumed it would be listed as 520cc@4bar and not 605cc@4bar because it makes it look like the tune is for 605cc@4bar which = 705cc

Yes, I have an AFPR.

Hmmm, do other JWT ECUs list the Ro2 and EGR temp stuff? Anyone else have this? Also, what does the 'Rest' mean after 'EGR Temp'?

Mine dosen't say anything about Ro2 or egr, but I've been running the egr tube open with the vacuum line going to it plugged and a wide open downpipe thus no cat or R02. Iv'e been runnung it like this for 2 weeks and I have no CEL, so maybe they do program it to disregard those.

It kinda makes sense to why JWT would say it the way they did.

It should be 520cc Injectors @ 4 bar, thus it equals 605cc, so to either make it look better or to make an average Joe not as confused they just say what the current cc is.

Injectors are rated for flow at a specific pressure. A flow number without the differential pressure means nothing. The common assumption when people talk about injector size is the flow rate at 3 bar. When you increase the fuel pressure to 4 bar, it is no longer correct to use that same flow rate to describe that same injector. You should use the new flow number.

I don't really understand your thought process. To me, it's semantics.

I can say it two ways:

520 cc @ 4 bar
605 cc @ 4 bar (520cc injectors)

He should have specified more than 'STI' injectors because there's all types of STI injectors. If he had (520cc) in quotes or (520cc STI), then it'd make more sense. Or if there was one flow rate of STI injectors then it'd be clear, but that's just not true.

Plus, I've seen a lot of JWT ECU's that say 370cc @ 4 bar. So what say you to that sir?

I don't think I've seen one ECU with 427cc @ 4 bar listed for the 370cc injectors. Granted, I haven't spent a lot of time looking at other JWT ECU's, but the ones I have seen are not like that.

-G

G,

I'm getting my 4 bar STi/Z32 MAF ecu sometime today and hope to install it. I'll keep you up to date on how it runs. I'm sure JWT has a good reason for setting them at 605cc rather than 520cc.

Cool, let me know what they write on yours. Like I said, it is programmed for 520cc@4bar, they just write it as 605cc@4bar because 520cc@4bar = 605cc

I'm wondering if they'll do the same on yours. Also, look forward to seeing the car on Sunday

They wrote 605cc @ 4bar.

aha! Craziness.

I say what I've previously said. Flow rates will tell you nothing about the injector size without a differential pressure rating. If you really want to learn about it, look up restricting orifice calculations on wikipedia or the like. You cannot calculate a flow rate through an orifice (such as an injector nozzle) without a differential pressure. The other main factor involved is cross sectional area (or equivalent area) of the orifice... which is the true injector size. There are other factors such as orifice inlet and outlet shape that change the pressure drop due to eddy currents, etc., but in simplest terms orifice flow is based on area and pressure differential.

The world of car speak may want to say 520cc at 4 bar and 520cc at 3bar means the same thing, but in reality it does not. Those are two different injectors.