Out of curiosity, what consequences result from running the 3.5's 315cc injectors vs. the stock 3.0 259 cc on the same, completely untuned ECU?

 

You run rich...

 

Is it directly proportional?

 

You would definatly run rich like kevlo said. But some people are saying that on the long run, the ECU will accomodate for the larger injectors and "remake" or "readjust" its long term fuel trims (Im not sure if Im using the correct terminology, some1 correct me if Im wrong). How far its able to adjust? Who knows. Get some kind of a/f controller, its fun watchin your WHP/WTQ #s at the dyno go up by just pressing a few buttons .

 

It only adjusts in closed loop form. In open loop(WOT) you are rich as (insert word)

 

I would think it is. At WOT, depending on the rpm/MAF signal, the injectors will hold a pulse for x amount of time. The larger injectors will stay open for the same amount of time, but flow more in that time according to their capacity.

 

Stock ECU adjusting its' own maps in closed loop form.

 

That's what I was fearing. Jesus, it's a nearly 22% difference. I can't believe I ran the car hard all year. Congradulations, I'm a moron.

 

Better than being lean.

 

I was fearing the same thing with the 5th gen injectors running off my JWT ECU for the 4th gen. When I went to dyno I ended up running fairly lean (13.5:1). It could have been due to the tailpipe sniffer reading leaner than a wideband up stream, but if not that, then I have no idea. Unless the car compensated somehow (not possible?), or the difference between the 259cc injectors and 290cc isn't enough to trip the ECU up.....
Who really knows......

 

Stock cat makes readings leaner IIRC

 

I assume you mean with a tailpipe sniffer? (I have a test pipe)

OT- Where is the best place for a bung for a wideband? In the Y pipe before the cat? In the cat/test pipe?

 

In a test pipe would be fine. Near the flex would be perfect.

 

what could you use to tune vafc2? jwt? both?

 

JClaw
Are you running the stock 3.0 fpr or no fpr?
Do you know what your fuel pressure is?

The 3.5 injector 315cc rating is for 3.5 bar fp (50.8psi)
The 3.0 injector 259cc rating is for 3.0 bar fp (43.5 psi)

At 3.0 bar, the 3.5 injectors would only flow about 270cc (assuming Bernoulli flow)

You may not be as rich as you think.

 

yea get an afpr and turn it down a smidge

 

Yes 1995 FPR, but will be aftermarket next year (actually this year lol). I guess that means it's 3.0 Bar/43 psi but with the 315 injectors. So they need to be at 3.5 Bar to flow 315?

 

You do not want them to flow 315 if you are using the stock 3.0 ecu with no other means of fuel control.
Then you will be running 22% excess fuel in open loop.

 

The ecu is gonna get tuned sooner or later, that's a given, but I was thinking of "immitating" the 3.5 ECU by running it 3.5 bar w/returnless, get it tuned accordingly and generally act as if I'm running a full 3.5 swap without VTC's,

 

That would be the best thing since 1. there'd be no "heat-soaking" of the fuel and 2. it would make for the best possible atomization due to the correct fuel pressure.

 

isnt running rich increase your chance of pingage? causing the infamous ks to go off???

 

Left field --->here

You ---> parking lot.

 

I was thinking the same exact thing but didn't bother...

 

the newer ECUs refresh data faster than our vq30 ECUs

people use a/f meters/dataloggers to tune for optimal fuel mix

Don't forget Exhaust Leaks will make you run LEAN as well, so make sure to check for those.

 

What's that matter?
True, but what's your point?
They'll actually make you run rich, since the o2 sensors are reading more oxygen in the exhaust than there really is. The ECU dumps in extra fuel to compensate.

 

My setup:

3.5 w/o VTC's
DE-K FPR
DE-K Injectors
Stock Fuel PSI
Stock pump
3.0 ECU


Any red flags?

 

Where's the A/F data? That will show you a red flag...if it does exsist.

 

I will dyno come spring time. The car really feels like it could use a tune after the headers install.