My Plan...N2O Experts help out

[Weasy2k]

So i am going with my N/A 3.4L V6 with a new rev limit of 7000-7500rpm

I have to practice tuning with N2O and EMS so I decided to go with a 50/100shot to play around with. I have tuned for a couple years but always anything other then N2O.

WHat companys are good...I was looking at some ZEX kits but am unsure. I do know that a wet system is something I should look into and will most likly be shooting either 1 jet in the TB or 6 down the intake plenum.

[Enthalpy]

May I be the first to say, "yummy!" If you add cams to this and fart with the pistons so your CR is in check, this could be a beast of a setup!

The main enemies to engine longevity with N2O are cheap-ass systems. You want one that provides good cylinder-to-cylinder AFR. If you have a single-point nitrous and fuel injection, then that's the worst-case for cylinder-to-cylinder AFR differences. Fuel doesn't round corners as well as air/nitrous does, so the cylinders with a more "torturous" route from the nozzle to the intake valve will receive less fuel and the same amount of air/nitrous.

Then, you want an EMS that's smart enough to add fuel and remove timing. I'm sure you already know this, but only doing one or the other won't cut it.

I admit, I haven't tuned any nitrous systems either, but I'm sure it's like forced induction. You start with targets you know are safe and work your way to more agressive settings until you hear trace knock, then back off. Pulling 2-3 degrees of timing and leaving the AFR 11.5 or richer is probably a decent starting point.

Of course, you always need to watch temps! Start with a lower shot count so you aren't tempting fate until you have some experience with it.

[Weasy2k]

Well the cams are already thier for this year...This fall even crazier cams will be going in 294's as well as ITBS

I think im going to stick with 6 injectors for the N2O that way i can keep that whole problem of misfueled crap to a min

If i go with a wet N2O setup the fuel wil go in with the N20 but I am wondering if i go with larger injectors should i just control the fuel with the EMS.

[Enthalpy]

That's certainly an option. With 6 injectors and all-motor with a 100 shot, perhaps 550 or 650 is big enough. Most EMSes, even the ones with saturated drivers like the AEM EMES can handle those injectors.

[Weasy2k]

yea my stinkin ems is saturated as well...
I was thinking about using the stock resistorpack to bring that up to high IMP...

your views?


The thing with using the N2O injection you can have similar ot stock injectors and not worry about that added cost...soo looks like i will take that route. Just gotta learn more about this.

[MrGrimm]

my question is, how does one learn to tune themselves. is there a school for it or is it all street knowledge

[Weasy2k]

read read read...

www.efi101.com is the only school...its not a bad place to start really.

I learned tuning piggybacks and then got the concept down.

[MrGrimm]

is ti really easy to mess your engine up when you tune yourself though? when i think tuning i think the aem laptop hooked up full on tuning. am i wrong? sorry to discuss this in this thread

[Weasy2k]

(its my thread so i dont care :P)
Yes that is tuning and yes you can damage your engine if you dont know what your doing.

take a look at that efi course if your really interested

[Enthalpy]

Originally Posted by Weasy2k

yea my stinkin ems is saturated as well...
I was thinking about using the stock resistorpack to bring that up to high IMP...

your views?


The thing with using the N2O injection you can have similar ot stock injectors and not worry about that added cost...soo looks like i will take that route. Just gotta learn more about this.

If you have saturated injector drivers, you likely have a current limit of ~1 amp or so. That means if your steady-state resistance in the injectors is ~12 ohms or more, then do NOT use the resistor pack. These would be high impedance injectors.

If your measured resistance across the injector terminals is more like 2-5 ohms, then you need a resistor pack wired in series to bring the total circuit resistance up to ~12 ohms.

Don't worry too much about idling big injectors with saturated drivers. Unless you are going north of 800 cc/min., you will be just fine.

You can only have similar-to-stock injectors (assuming you are talking about a dry kit) if your injectors have the headroom to handle the extra oxygen coming in.

A BSFC of ~0.55 is probably relatively safe to use. That's in pounds/hour-hp, measured at the crank. That means you take your expected crank hp divided by the # of injectors and multiply it by 0.55 to get the total per-injector flowrate in pounds/hour. To convert to cc/min., you multiply by 10.2.

The above assumes 100% duty cycle, which is obviously bad. To correct for a safe duty cycle, you take the resulting number and divide it by the max duty cycle you want to see. Most use 80%. This means you would take the above number and divide it by 0.8.

The result will be a per-injector static flowrate in cc/min. This is the minimum injector size you should use.

My BSFC figure might be off since I'm not 100% used to Nitrous. That would be the only thing to verify with a google search.

[Enthalpy]

Originally Posted by MrGrimm

is ti really easy to mess your engine up when you tune yourself though? when i think tuning i think the aem laptop hooked up full on tuning. am i wrong? sorry to discuss this in this thread

Since Weasy didn't mind, I will answer this as well. Take the EFI 101 classes, it's fantastic! Then, come back to the EFI corner and post any questions you have. I frequent this section and will answer them to the best of my ability.

www.efi101.com.

[Weasy2k]

Yea my injectors are 12-13ohm and my drivers are capible of driving one 3ohm injector per line. Max 12a

Im more used to tuning then to building still...

[Enthalpy]

No worries! I have my degree in engineering, so building this stuff comes very natural to me.

Leave off the resistor pack. At 12 ohms with a driver current of 12 amps, you aren't doing anything to help yourself with the extra circuit resistance. Take all 5 leads on the resistor pack and solder them together.

Before you turn on the key and power up the EMS for the first time, make sure you test the injector circuit to make sure it isn't shorting anywhere, giving you ZERO ohms!

[Weasy2k]

This is going on my v6 engine so im wiring everything up on my own.

AHHHH i just get it now...correct me if im wrong

If you have a low imp driver the high imp injectors dont need as much power to drive them as the low peak and hold type do?

[Enthalpy]

Not exactly. There's no such thing as a "low-impedance driver". The driver is inside the EMS. You are thinking of a "peak-hold driver" and "saturated driver." Impedance is an expression of various types of circuit resistance, but in our case, it's just resistance you measure on a $20 ohm meter. The addition of resistors in series in the circuit adds to the overall resistance and bumps the circuit's "impedance."

The big difference is the peak/hold driver clamps the current (prevents it from going any higher than a specified value) regardless of how low the circuit resistance is. The saturated driver has no such device, it simply throws a switch and hopes for enough circuit resistance to avoid being blown.

With a saturated driver, you usually use high-impedance injectors to manually keep the current down. Since you are dealing with 16 (worst-case) volts, if you have a saturated driver that can only handle 1 amp, then you need 16 ohms in your circuit. In your case, you have 16 worst-case volts and a saturated driver that will handle 12 amps. That means your minimum circuit resistance is 16/12 = 1.33 ohms.

With a peak/hold driver, the EMS opens the injector using a 4-amp clamp initially (for about 0.1 milliseconds) and then drops the clamp to 1 amp while the injector is held open. This is where it gets its name. What this does is SLAM the injector open QUICKLY then use just enough current to hold it open after that. This will give you much more EVEN fueling at idle.

No, it doesn't hurt the injector.

Peak/hold drivers only benefit you when your total voltage / total reistance is more than 4 amps. In my case (Nemesis), I have 2.5 ohm injectors and 16 (worst-case) volts. That's 16/2.5 = 6.4 amps. Since this is more than 4 amps, my peak/hold injector drivers are clamping at 4 amps, then clamping at 1 amp after the injector opens.

If you have low-impedance injector circuits with saturated drivers, then you might pop your circuit protection inside the EMS!

Does this make sense?? I'm sort of a crappy teacher, but I make up for it by being persistent (and apparently verbose... ). I love teaching people about EMSes! Please ask any other question you have.

[Weasy2k]

AHhh snaps yea i was confusing the injector with the driver....baaam..

I will make this info usefull soon in the EFI section

its been a while since i looked at EFI stuff...been doing cyl head research latly...cams is another headful of info!

Thanks man at least im ok for my setup. I have to buy some injectors for the other v6 im building and this made it clear as to why i needed high hz injectors i just forgot why