Spooledup300z

I was wondering cause most of u modded guys use something like 720cc primary and 1600cc secondary.. why is that???


why does the primary rotor need less than the secondary??


im going with 450cc or 550cc injecotors and thats rich for my Z.
1600cc's or 720cc would make it run way to rich.

JoeD

you can never compare the amount of fuel and air the rotary ingests to a pison engine. and just cause a car has 1600 cc injectors for example, doesnt mean that the injectors are injecting 1600 cc's of fuel the whole time. its called tuning.

Spooledup300z

ok so what ur saying is.. they put 1600cc injectors on there but they dont push them to there make..1600cc?

but u did'nt answer my 1 Q.. why is the primary bigger than the secondary?

Cap'nWankel

Think of it like a 4 barrel carb. the secondary's only open up during the harder driving, and since it IS during harder driving, the motor requires more fuel i.e. bigger injectors... and per your first post, its not primary/secondary rotor, each rotort has both a primary and secondary injector.

JoeD

both rotors have a set of primary and secondary injectors. (its not like one rotor has primaries and the other has secondaries). the primaries are used at 3K RPM and below. above that, the secondaries kick in.

JoeD

you beat me to in Cap'n.

Cap'nWankel

i thought 3800?

Jedon

The primaries are smaller and are for idle and low rpm use. The secondaries are larger and come on when you are in boost, a rotary uses a lot of fuel when turbocharged. Also, your Z is 6 cyl right? So you have 6 injectors? 6 550 cc injectors is 3300cc of injection, 2x550 + 2x850cc on an FD is 2800cc.

crispeed

You couldn't have put it any better!

crispeed
87TII
9.20@150mph

Spooledup300z

Man u guys kick *** so ******* much!!!!!!!!!

ya'll r u supportive man... Thanx alot.. and now i know the answer to my questions thanx everyone!!!!!!! :1party:

Node

iTrader: (1)

What is the biggest size fuel injector you can use without needing a modified fuel rail?
I'm mainly asking about series 4 and series 5 13BT engines from a 2nd gen

maxcooper

From my experience of having a siezed secondary on my FD, it seems the secondaries come in when there is any boost (at any RPM) or about 4000 RPM when you are cruising as lightly as you can. So, the exact point they come in seems RPM and load dependent, rather than just at a fixed RPM. So its...

Idle, light load, & low RPM: primary injectors only
Load or higher RPM: primaries + secondaries

It's kind of like the turbos in how they are staged: just primary and then both rather than switching from primary to secondary.

The different fuel consumption rates of rotary versus piston engines can be compared -- as the difference in the BSFC. The Brake Specific Fuel Consumption (BSFC) tells you how much fuel it takes to make a given amount of HP per unit time -- the units are often pounds of fuel per HP per hour. A turbo rotary might take 0.65 lbs of fuel to make 1 HP per hour. A turbo piston engine might take just 0.60 lbs to do that, and is thus more fuel efficient.

Rotaries take more fuel for the same HP level largely because of the shape of the combustion chamber. The rotary chamber has a higher surface area to volume ratio, so it loses more of the heat to the cooling system and is thus less efficient at turning the energy in the fuel into power at the main shaft. How rich you run the engine also affects BSFC, and rotaries like to run rich to avoid detonation. See my web-based fuel requirements calculator to see the effects of different BSFC values on HP and fuel requirements:
http://www.maxcooper.com/rx7/how-to/...tem/calcs.html

-Max

Node

iTrader: (1)

Hmmm, odd, can anyone back that up about FDs. I know on Series 4's that its 3700/3800. The cause of the famous 3800RPM Stumble is caused from the ECU having crappy grounding and not handling lowering the flow rate of primaries and turning on secondaries or something like that.
BTW anyone know if it is 3700 or 3800. I always see both

Dyre

Node, i think most 1200cc/min top feeds will fit the secondary rail. But K2RD and others make or modifty the secondary rails to accept the more common (and sometimes cheaper) 1600cc/min injectors.

Node

iTrader: (1)

thanks Dyre

Jedon

You can also get the stock 850cc injectors bored by RC Engineering to 1300cc.
Given that I have a PowerFC and will be putting on a T04E 60-1, which injector setup should I use? I take it that the PFC can not control extra injectors so I'm limited to 4. I'm leaning toward modifing my primary rail to accept my 850 secondaries and getting my spare 850's bored to 1300 for the secondaries. This solution is good purely from a cost standpoint, which is definately an issue. Thanx!
-Jedon

Maxthe7man

I followed that link that was posted to the Precision Turbo GN site, they have other injectors as well, in the 720, 850cc and 1200cc sizes, I wonder if they are the same configuration as the 1600's?, if so this would be a place just buy your 1200 cc injectors from instead of boreing them out to a larger size, for what RC wants to just bore them, you could probably buy new injectors less, they were pretty cheap on that site.. I was looking at getting my TII injectors done, its alot of coin to get them increased in size..Max

AJC13B

I have the standard 550cc primaries and they are used up until over 4000rpm when the 1650cc secondaries cut in.

Nice and smooth transition

20B_FC

The secondary staging point on the FC's and FD's are about 3800 to turn-on when the rpm's are increasing. When the rpm is decreasing, the turn-off point is about 3700. This is a common trick they use in control systems to avoid stuttering problems when the rpm is hovering in the ~3700-3800 rpm range.
In the Haltech E6K's, the staging has this hysterisis control similar to those stock ECU's. The Electromotive GPO and other ECU staging outputs are just rpm on-off switches, thus very unstable when "hovering" around the staging point.

PK

maxcooper

It may often be about 3800 RPM, but my FD would fall flat on its face when I started to get boost below that RPM point when I had a stuck secondary. That leads me to believe that it is more than just RPM that decides when they come on for the FD.

-Max

Wade

iTrader: (1)

I can support Max Cooper on the FD staging. The RPM on/off point depends on load vs. RPM. From memory, I could get up to 4500-5000 RPM when driving very lightly, but the secondaries came on much lower if I built boost. This is easy to verify, just unplug your secondary injectors and when your car falls on it's face, that's when the secondaries are coming on.

It also seems like the staging point is lower when the car is cold. So water or air temp might be yet another factor.

Wade

Dragon

Don't try this at home kids!

spyfish007

Ok lets try and clarify some topics and sort them to specifics:

3rd gen ECU: 2700 ... turns on secondaries regardless of load/boost. It actually turns them on off and then back on again which causes the stubble know as the 3k hesitation. With poor grounding this problem is amplified a couple times over and the car doesn't run as well in general.

2nd gen ECU: 3800/3700 ... turns on secondaries regardless of load/boost. Grounding issue is similar to 3rd gen.

PowerFC: secondaries turn on when the duty cycle is above 50% on the primary injectors.

Haltech: set by pressure values ... mean say 2 psi of boost then secondaries come online for all rpm valves.

Another clarification on Max's discussion of thermal ineffiencies in a rotary (which is a good write-up) is that a rotary retains more heat than a pistion engine because it has a higher surface to volume ratio in the combustion chamber. The increased surface area of a rotary engine absorbs more heat and hence is not as effiecent. Note: mainly a clarification on the phrase, "loses heat to the coolant system".

Wade

iTrader: (1)

By clarify, I guess you really mean "add some inaccurate information"?

3rd gen DOES NOT turn on secondaries at a set RPM regardless of load/boost. Max had a stuck secondary injector, and I once forgot to plug mine up after working on the car, and we both found that staging occurs at different RPMS depending on LOAD (and I also found that water or air temp also plays a role).

Also, the 3rd gen 3k hesitation has nothing to do with the secondaries, this is easily demonstrated by the fact the 3k hesitation happens at low load, low load staging of the secondaries is demonstrably at a higher RPM than 3k.

Like I said, this is easy to verify by unplugging the electrical connectors to the 2ndary injectors. There are some other ways to verify it that are safer but this is by far the easiest.

Wade

13BAce

I would go with the 1600's because you can get them for only $90 at http://www.precisionte.com . If you don't want to bore out the fuel rail then you can just cut some of the plastic off of the top of the Bosch injector.