For those that went with injectors in the 510c-770cc range, which brand and size did you choose...and why, and what type of modifcations did you need to make to the fuel rail. Spacers? Grinding?

What ECU/eManage solutions are you using to get everything running correctly. Was idle air adjustment needed?


It's strange, but when I goto the RC Engineering website and plug numbers into their calculator, they claim I need like an 850cc injectors to run 750crankHP or about 600whp at the wheels at 52psi of fuel pressure. That seems a bit much for a V6 with 6 injectors.


For daily drivability, a smooth idle, and low fuel consumption, the idea is to go as small as possible, but still deliver the fuel you need for your max HP goals, hopefully using 80-85% of the injectors duty cycle. But 850cc seems too big to me...any thoughts?

 

I'm no expert but I can tell that I have been researching this for many hours for the last few weeks.

Here's what I've concluded for myself.....
1) Having injectors that are too large can be just as bad if not worse than having too small injectors
2) I have heard of reports where I surmised that engines have melted pistons (not 350zs) because they have run way too rich by running injectors too large and dumping way too much fuel in the cylinders
3) Too rich or too lean and your emissions will be out to lunch if that's an issue for you
4) You would need to modify the Z's fuel system to have a return, to allow for better tuning if you go beyond say 510cc s
5) The bigger you go with injectors, the harder it will be to tune with a piggyback ECU - you will need more sophisticated electronics, and spend much more time, effort, and money tuning because you are venturing so far away from the stock setup. It get's harder to maintain the 'civility' of the car as temperature changes, fuel octane changes, keeping a nice idle, and mainaining good mileage.

I have read posts where I'm left with the impression that the advice is 'buy bigger injectors now for when you upgrade your HP'. I think this can be misleading - True it's better to have any piece of equipment be always slightly underutilized than always overutlized because that leads to failure. I tend to think of it as you must target the HP and stay plus or minus 15% the calculations for injector size to have a robust solution. If you get mods to move you up to the next level, then you should sell your old injectors and get the larger ones.

My 2 cents. Hope that helps a bit...

 

GQ - actually, assuming you are doing some safe BSFC assumptions, an 850cc injector seems just about right for making 600 wheel hp on a 6 cylinder turbo motor. at 53 psi rail pressure (stock), with a modest 80% - 85% duty cycle.

The real challenge you run into on this car is going to be finding something to control 6 850cc high impedance injectors This is where a truly flexible engine mgmt solution is really handy. If it were me, going for that type of ultra high HP, I'd be converting to a MAP based setup post haste, and swapping to a low impedance injector (and thus an ecu that can run it) whcih will allow for much smaller on times and as a result, an easier car to program for idle.

Chris - you postively cannot melt a piston by using too much fuel - just the opposite in fact. Fuel is a coolant! Yes there is such a thing as too much fuel - the extreme end is called bore washing, where you literally just dump fuel to the combustion chamber and damage occurs. In all my years of modding and tuning imports, I have never seen any car ever do this.

Your advice though Chris in terms of maintaining near stock driving and reliability when going standalone and thinking ahead when selecting components is very well put - guess you have been listening when we've talked

A truly reliable, get it in and forget it 750 (crank) 350Z is not going to be an easy achievement by any stretch of the imagination

 

Adam,

Yes Obi-Wan, I know I am not a Jedi yet!

What he said.

Just hope I don't have to eject the warp core!!!

 

well another method though more crude (as we know) but offers the best driveablity at "off boost" is to use a Rising rate regulator greater than 1:1. If you replace the typical 1:1 with say a 1:2 , you can still stick with your medium size injectors and get that extra 25-50% flow at the boosted top end. Given that you will have forged internals tuning will be more forgiving than FI @10.3:1 OEM.

 

I smell another group buy once we have come to a conclusion.

 

actually SGP was able to run 600rwhp on just 720cc injectors and was told those have plenty more room to grow. So 850cc injectors I would say are way to big. I am planning on going with 510s at 45psi with no riser and i bet it will be fine.

 

does anyone know of an injector that is the factory style and dimensions but much larger size? I would like something that fits just like stock but is like 720cc or larger.

-Charles

 

Yeah on 300zx's we have done close to 700 Rwhp on 740cc injectors and over 850Rwhp on 850cc injectors.

Kyle
SGP Racing

 

what type of fuel rail mods are needed to get the 700cc injectors to fit?


Yes...group buy....group buy...I see another one on the horizon.

I was told that TS can reflash for 510 injectors. If they can, they a solution would be to get that reflash, and then scale a bit further with the eManage.

Can somone also explain the difference between low and high impedence injectors, and the difference between peak and hold and saturated injectors? I sorta know what they are, but I'm curious as to what is their inteneted application in terms of the 350Z?


Here is RC Engineering's list of injectors and prices.

http://www.rceng.com/prices.htm
Thanks!

 

on another note, it would be relatively easy to sell our 440cc injectors that came with the Greddy...so incremental costs would be small.

 

After talking to Phunk, and confirming with RC Engineering, the 440cc injector has the same physical dimensions as the larger sized injectors. This means to upgrade, it would be a direct swap, without any additional mods to the fuel rail or anything of that nature.

I also called TS, and although they dont have a 510cc reflash, they recommended using the 380cc reflash, and then scaling the rest of the way with eManage.

Anyone wanna buy a set of gently used 440cc injectors? hehe

 

Saturated high impedance, peak hold= low impedance (they are synonymes).

Low impedance are far easier to control, and allow for much lower on tiems......

a Stock Z uses high impedance.

as for netting x hp out of y injector its not always that simple....methods of tuning, peak timing and overal timing curve, CR, combustion chamber cc, etc etc all play a large role in the amount of peak power you can generate, not to mention voltage to the pump and fuel pressure.

RC is not often a well suited first choice, as they often use ucas based injectors that are simply bored out to flow more. The Denso alternative tend to have a much better flow pattern. However the Bosch upgraded units sometimes offered by RC are a good choice..we have used them tons of times (I run 720's in my 280ZX), and have not had a single one fail. I've had more standard issue Lucas RC units fail than I care to remember

adam

 

The Denso alternative is like the PE injectors..right?

 

Hmmmm i believe you can directly replace the injectors with up to 900 cc if i remember correctly as a direct bolt in with no modifications. cant remember which brand.

The problem it seems is controlling these injectors . Do u guys know if a piggyback system can ever control injectors like 700cc-900cc or are we talking stand alone em only?

 

Did some more research on RC...looks like many of their injectors are Denso based. At least the 550 and 650's are.....

Can someone confirm this for me? I dont really care either way, becuase I am going with RC's just becuase I wont have to change anything else...and I've already cut the stock harness, so I don't care about plug/play capability.

RC Engineering as been making racing injectors for 30 years,and would be surprised if the failure rate is greater than other high performance injectors.


Squill, regarding control...SGP Racing got 700'something CC injectors working with the eManage coupled with a 380cc reflash. The eManage will have no problem controlling them. The eManage, technically, can controll injectors 150% larger than base.

I plan on going either 550cc or 650cc. Since I dont intend ever run more than 600whp on my car. Probably like 500-550whp.

 

650cc founds nice for my 600 rwhp goal. I thought TS has a flash for their 5xx cc injectors. I guess it depends on who you talk to because.

 

just remember the larger the injector the harder it will be to tune. just my .02

 

That is far from true. The smaller the injector the harder you have to make it work to get proper A/F ratios. This means that it will fail sooner then a properly tuned bigger injector. We use 1200cc injectors in Supras and they idle at 900 Rpm and run fine .

Kyle
SGP Racing

 

I think Spaz meant that as a general rule of thumb, a larger injector will be spraying more fuel at its lowest duration (1ms). So at some point, idle, cruise, and driveability can be effected because you can't get the mixture to 14.7:1 at idle and cruise.

Under WOT, an injector working at 80% max duty cycle is ideal.