Question 1
Has anyone successfully run 4x1200cc/min injectors with their Rtek 2.1 in map based timing mode? By successfully I mean that the car doesn't flood, the secondary injector transition is relatively smooth and their low load low rpm engine performance was unaffected.

I'm currently running four 720cc injectors. The car runs, starts and boosts well in it's current configuration, but my goal is the be able to run about 14-16 psi with injector DC below 90% on my BNR Stage 4. Right now I'm hitting 85%+ injector DC above 10-11psi. I've seen others using 4x1000cc/min injectors maxing them out right about 14psi, so I'm wondering if I can use 1200cc/min injectors. I want to have some room to work with when the AFM elimination and 2Bar map sensor options come out .

Question 2

If I was to install four 1200cc/min injectors w/ my Rtek 2.1 in 4x720cc/min and map based timing mode, would I theoretically be able lean out the fuel map 40% (1-(720/1200)= 0.4) across the entire fuel map and have the car run reasonably close to how it did w/ the 4x720's?

Question 3
What other injector size combos larger than 4x720 are people running and how well are they working. I would be interested in hearing about 720x1000, 4x1000, 1000x1200, 4x1200,1200x1600, 4x1600 etc. I'm also considering creating an E85 map so I would like to get the largest injectors that will still allow the car to run well.

The biggest problem I can think of would be the secondary injector transition.
It seems that in map based mode on the Rtek 2.1, the secondary injectors are no longer activated at a specific adjustable rpm( like they are in load based mode). I think the secondary injectors come online when the primary injectors reach about 60%DC. I can imagine that this would make tuning the fuel map when using very large secondaries very difficult if not impossible. Since the secondaries could come on when ever the Primary injector %DC was above 60, which isn't always the same engine rpm, it would be difficult to determine where in the fuel map to start leaning it out for the larger injectors.

I was thinking that if I kept the flow ratio difference between the primary and secondary injectors relatively close to 24% [(1-(550/720))x100 =24%], and the difference between the new and old primaries was within the correctable range using the Rtek that the secondary injector transition would remain smooth.
What do you guys think?


Injector combo % difference

550/720= 23.6%
680/850= 20%
720/1000= 28%
750/1000= 25%
800/1000= 20%
850/1100=22.7%
850/1200=29%
1000/1200= 16%
1200/1600=25%

I would love to run 1200 x 1600 using the 550x720 injector preset in the Rtek, but I wonder if the Rtek can correct for a 55% larger primary injector. If it could, it would probably be just about the limit, what do you guys think?

Please correct my list if I'm wrong, but I think I've seen all of the sizes I've listed available for the FC as drop in replacements.

 

it all depends on the ratio between the primaries and secondaries. i had 750s and 1000s and it worked fine at only 30% difference. 750s and 1600s dont work very well, which is over 100% difference. But too big primaries will cause idle/cruise problems at low injector pulsewidths

+ eleventy it would be better for tuning if the staging was boost/rpm based, not load or d/c based as you say. that way you would be able to tune the transition

 

Your 750x1000 combo have a 25% difference, which is only a 2% difference in ratio between the 550x720 preset which have a 23.6% difference. I would imagine that this size combination would work very well. I know that I will need more fuel than that if I want to keep the DC's down.

Are 1000cc/min injectors too big as my primaries? I need it to run well in cruise, idle and starting. I didn't notice a difference at all between the way it starts or idles with the 550's vs the 720's in the primary position. I may just try 4x1000, does anybody have first hand experience with this size combination?

 

I'm so glad you posted this question, I was about to do it myself.

So what is the largest primary injector that can be ran before having the idle/cruising issues that GXL mentioned? 850? 1000?

I am considering running the an 850/1090(1200) setup and was worried about the transition as well.

 

what prevents the rtek guys from adding in other presets? Is there some limit on the duty cycle minimum?

 

That is a good question, I would like to see some additional presets also. What would be even better would be some sort of fuel calculator that would allow you to enter your primary and secondary injector sizes, and then convert the stock fuel map accordingly. Then again that might be a little much for our little palms to handle, maybe when we move to the new platform.

 

i dont think presets are the answer. with my bnr stage 3, my fuel map looked like -25% at idle to +15% at full boost with 750cc/1000cc injectors. its not going to be as simple as taking out a static % for your injector size.

What would be better is if you could enter the ratio between your primary and secondary injectors, and it would automatically take that % fuel out whenever the secondaries are on. Then you tune your fuel map like normal, but not have to worry about tuning the transition.

the secondary injector transition is what is the problem

 

yep the transition is what hurts the most. I think this might be a physical limitation of the ecu in regards to how the fuel map is computed. maybe turbo2ltr can chime in on this.

i know the numbers we put into the rtek in regards to correction is a percentage of what the preset is. More presets would allow people to run larger injectors without issues though.

 

Not unless u run another injector(or set) like the boys do it in japan

 

Looking for a decent solution to the injector mismatch problem is on our things to do list.

 

Is your fuel map near -25% all the way up until the point at which your afm maxes out? I would think that after your AFM maxed out you had to add fuel to compensate for the air flow above what the afm could measure. That would explain the +15% at full boost(above 10psi?). Is that roughly how your fuel map is laid out?

550/750= 28% difference which is close to the -25% you take out at idle.

 

nope, after i tuned it for 11/12's AFR in boost, the fuel curve ended up being fairly linear from -25% at high vacuum/low rpm to about -5% at 0 vacuum to about +15% at 12-15 psi/high rpm. AFM was not maxing out, ithink the highest i ever saw it was 800 cfm or something

 

just curious on this. is it a software thing (like an update to the palm can fix this) or is it an actual hardware limitation.

I think just having it so you can select a primary injector size and a secondary injector size and it will calculate the variance from stock and then trim fuel accordingly.

I can see this being an issue depending on how the stock map is laid out in the ecu. Maybe you can shed some light on how the stock computer figures out the injector duty cycle after the secondary transition.

 

It has more to do with making the math work within the ECU than anything else.

 

I am pretty sure I am not alone on this one but this would definitely be something I would see as a priority. AFM delete is cool and all that but if we can properly compensate for larger secondaries and primaries to eliminate transition issues that would hold me over for waiting on the afm delete.

 

So, has anyone tried running 850s for primaries on the 2.1? If so, did you have any issues tuning your idle?

Right now, I'm trying to decide between 750s or 850s.

 

I'm about to go 950cc primes and 1000cc sec. I'll let everyone know how it goes in about a week.

~M

 

it seems like the practical limit at this point is 720ish/1000 if you want consistent low load driveability and a decent injector transition.

 

Any feedback yet?

 

Sorry, Sandbagger. The weather out here hasn't been the best for working on a car! The next few days are looking up, so i should start working on my stuff.

 

Sorry, Sandbagger. The weather out here hasn't been the best for working on a car! The next few days are looking up, so i should start working on my stuff.

Arghx, curious. Why do you not think that these sizes will not work? I ask purely as a newbie to engine tuning as I just don't know for sure. Looking at the instructions, the ecu is capable of removing @ 34% fuel from the programming (950/34%=323, 950-323=627), so in essence, you could see the "flow" of a 627cc/min injector at any given time. With the addition of just 1000cc/min secondaries, my adjusting of the transition is minimized. I ran this by the person who will be tuning my car (a Motec cert. tuner) and with being unfamiliar with the Rtek felt the logic was sound.

Is that fuel adjust for adding/removing across a range on a map or just relagated to the Rtek presets (550/550, 550/720, 720/720). Even if this is the case, my primes are still within this window. Again, I'm new to this, so teaching is welcomed.

 

i think its more of a matter of will 1000cc primaries idle. the pulsewidths will be very small, somewhere in the range of 1.2-1.5ms, which may make for a rough idle

 

OK, I see. I'm curious to see what my tuner ends up suggesting.

 

There seems to be a "solution" with regards to adding large low impedance injectors on, say, a Power FC. Could this be used to correct our issues?

https://www.rx7club.com/showthread.p...jectors&page=7

 

^^^GXL90, weren't you a part of the aforementioned thread? Perhaps you can shed some light on the subject.

~M