or so.

I was, as I was under the impression I could go to 10 psi on stock injectors. Apparently, I was misinformed.

Thanks

Jason

you can go 15psi on stock injectors*

































* so long as your fuel rail pressures are 200psi.

[QUOTE=Braineack;1021859]you can go 15psi on stock injectors*


A major kit vendor is selling a kit that claims to make 200HP with stock injectors, at 8-10PSI, and a second kit vendor is not far behind. That isn't helping those of us who want to "roll our own". We're likely to want or need to save money and use what information we can scrape from others.

I'm a noob, but I've been reading, and my conclusion (so far) is that it might be possible, if everything is perfect, and you're holding your mouth just right, and you're using a rising-rate fuel pressure regulator to cram more fuel through the stock injectors than they're supposed to, and achieve these numbers. I don't think it's prudent to attempt it without a lot of guidance and experience with stand-alones and FI, or have a lot of hand-holding from the vendor.

My heart goes out to the OP, who has lost his motor! That's a big bite, and one that doesn't have to happen. The stickies in this forum are great, and they're full of correct information.

However, I haven't found any that look specifically into some of the ways that kit makers cut corners to meet power goals, and to meet price competition. I think this would be extremely helpful for those of use who are trying to get up to speed quickly.

I'd volunteer to do this, but I'm too new in the game to have the experience I'd need. Hell, I hope I don't end up like to OP when I get the turbo installed in my car! I *would* be willing to do it after I have enough experience to be credible and get things right.

Eh? You completely contradicted yourself there.

Better as a one man job, but not safe looking at the gauges... 2 people means one can concentrate on driving, and the other on engine vitals.

Experienced tuners don't need a helper, but for noobs it's an absolute boon.

Do you even know where the A-pillar is?

Yup i've disagreed with them many times... what they dont mention is that they are running 8psi at 13:1+ afr ratios... Why? Because if they say their kits only make 180 at the wheels and are limited by the injectors you'll go to the competitor that claims their kit makes 200 using the same injectors. If the op had started reading this forum and the truth first, his motor still would be in 1 piece.

Last time i got into it with Corky from begi... even his own math showed that the stock injectors max out at 180ish crank hp which is about 6 psi.

At 100% duty cycle i started leaning out at about 6.5k rpm and went up to 12.2ish afr by the 7.2k redline. Again that was at 6 psi.

Alright, I've tweaked my AFR targets, does this look better:

https://www.miataturbo.net/attachmen...ine=1371255585

Also, I did some digging, and found that the DIY 1.6 map is for a 2560, which is what I'll be running. Does this timing map look pretty safe as a base to work with:

https://www.miataturbo.net/attachmen...ine=1371255585

Again, thanks everyone for your help, and not beating me up too bad. This has definitely been a learning experience, and a mistake that I will NEVER make again.

Thanks,

Jason

Your next main concern will be the VE table because that is what your ecu will actually be running. Whatever it says on the VE table is how much fuel the ecu will spit out.

Yes your afr table looks better. Personally i'd go to 12 afr at 101 kpa and 11.5afr for the 156kpa

To triple 88a note my previous sarcasm..

Sigh.

To Op,

The ve table is that actual fuel numbers the ecu is using. The afr table I just a long term target that auto tune is slowly working towards, it will get there eventually but if your 8psi pulls are 20% too lean the auto tune just makes sure they are 18% too lean next time.

So you do a pull at the lowest pressure your setup will allow you to run. Which is 6 or 7psi of - vacuum-.
You watch the boost Guage to ensure this and you check the data log after. Double check afr against known good values at this pressure and if it isn't within 5-10 percent you go to your ve map and add the right amount of fuel to get it there.
You then move to the next kpa row up (still way in vacuum no way near boost.
Using the numbers you just found for the last row check the next row looks sensible, if not adjust it manually.

Now do another logged pull and repeat all the way to 100kpa.
Now once you have cruised around with auto tune with one eye on the wide band gauge and auto tune has trimmed the last few percent so it drives really nice, you cut the wire holding your waste gate open and continue tuning the same way 1psi of boost at a time.

Dann

Theoretically you could, as long as you boosted your fuel pressure A LOT with an AFPR, which you don't really want to get into since the MS with larger injectors can do the job at lower fuel pressures.

In other news, I've been running my stock 99 injectors with a walbro 255 fuel pump and an sr20 turbo on 7psi for years with no issues. I don't even remember my duty cycle.

Triple, I'll tweak the AFRs a bit.

Dann, thanks for the step by step procedures, much appreciated. I do get that the VE table needs to be right before using VEAL now (I was thinking VEAL would take bigger swings in tuning runs, now I know better).

How does the timing map I posted last night look, safe enough to tune with?

Thanks again,

Jason

For injectors, I am thinking ID725s with PNP harnesses. Sound good for my application? based on the turbo/boost levels I plan to eventually hit, I'm thinking I should be fine.

Thanks,

Jason

As you can see in my signature, I am running stock 2001 injectors with an EMB and my Autotune, BUT my AFPR takes my fuel pressure to 95psi @15 lbs of boost. I maintain a steady 12.5 AFR whenever I am in boost.;)

The version of stock injector on the NB2 running a higher fuel pressure will support at least 8.5 psi of boost (Mazdaspeed). My 2002 on stock injectors easily supports 7psi, 182 rwhp, tuned at 99 degrees ambient for 91 octane and I'm still pig rich in boost.

The NB2 is a different animal. With 10:1 compression ratio and the variable cam we make more horsepower at lower boost.

Well yeah at higher fuel pressure....

NB2's run a higher pressure, around 55 - 60 psi stock as per factory design.

The fuel pressure on an NA is regulated to appx. 42 PSI above manifold pressure. Thus, the pressure differential across the injectors is a constant, and flow through the injectors (mass units per unit time) remains constant regardless of load.

The fuel pressure on an NB is regulated to appx 58 PSI above atmospheric, regardless of manifold pressure. As a result, the pressure differential across the injectors decreases as manifold pressure increases, and the effective flowrate of the injectors is lower at higher loads, and higher at lower loads.

This, the difference in fuel pressure between the two cars is not a constant. At 100 kpa of MAP, the NBs fuel pressure is ~ 16 PSI greater. At 10 PSI of boost, the NBs fuel pressure is ~ 6 PSI greater.

An injector which is rated to flow 230 cc/min at 42 PSI (the nominal NA fuel pressure differential) will flow 246 cc/min 48 PSI differential (what an NB will experience at 10 PSI of boost), which is a 7% increase.


I would not hang the safety of my engine on 7%.

(7% smarter than FaeFlorida is still dumb enough to keep you out of the electric chair on the grounds of "not mentally competent to stand trial.")

NB2 injectors are 265 cc/min. I did a search here. Showed up in FAQ. I expected better from you, Joe. You are my hero for getting the science right.