This may be a dumb question, but has anyone ever tried only running 2 large injectors in the primary spot? Im under the assumption that the primary injectors are in a better location and with injectors improvements over the last x years big primaries could povide good idle and still be enough for a 300-400 hp car

 

To answer my own question, yes and no.
it would technically work but at the expense of idle and cruise. For me it would probably be ok, the car is not street driven.

 

It just depends on the ecu and injectors. Modern ECUs can handle large primaries so long as they are quality injectors like IDs. ID has a great article on low pulsewidth operation that explains it in detail.

Low Pulse Tech - Injector Dynamics

I've managed a street port rew to idle perfectly smooth at 900 rpms at a 13.5 afr on pump gas with ID2000 2200cc primaries on a haltech elite pretty easily.

Skeese

 

Well that’s encouraging. On pumpgas?

Anyone know if the primary injector location has any advantages?

 

I would guess so since it injects close to the port opening making the port wall fuel pooling less of a factor.

 

You will make the most power with multiple points of injection, furthest from the port, that is why F1/touring cars/powerful bikes have over trumpet/plenum injectors. It allows the most time for evaporative cooling before the chamber.

Best idle would ideally be one very small injector very close to each port for minimum wall wetting and best charge mixing.


If you want the very best mix of idle quality and top end power you would run a pair of small primaries on each rotor, one in each runner and a pair of secondaries pretty muxh on the throttle body side/under the plenum to get best evaporative effects at higher loads.

While a relatively large new injector will idle ok in the primary with a decent ecu it would be a step backwards performance wise.

 

Well, given that I've done these calculations for my motor, I can break it down with you. I have 6x ID1700x in Primary > Secondary > Tertiary injection form.
As a side note, I prefer to run HIGHER nominal base pressure (which reduces pump flow, but increases cc/min of injector output and more importantly ATOMIZES the fuel better) if the vehicle is setup for shorter run times such as drag racing, time attack, hill climb, etc. Keeping nominal base pressure closer to 3 BAR (43.5psi) will help keep fuel cooler for a vehicle setup for long run times such as daily driver, canyon carver, drifting, Silver State Classic, etc.

The ID1700x can go down to about 16uL (per injector).
A stockport 13B requires roughly 20uL (per rotor) of fuel to idle properly on pump gas.
Obviously MORE fuel for e85, in which case the injector has more flexibility to maintain requested Lambda values.

Andy did a pretty damn good job on this video:

 

I can idle our supercharged 3 rotor race engine (very large street port) at 1100 easily with 1700s controlled by an M600 in the primary position. Never saw a point in going lower but thats an FYI for you.

 

Not to Hijack the thread...but I'd love to hear more about this supercharged 3 rotor =-) in the DM box

 

Sorry I haven't responded to this sooner, the flooding/mudslides etc here in Santa Barbara have made for a hectic bit of time. I don't want to hijack either and since Elliot threw a thank you at your post I suppose I'll create a build thread when I'm back in the shop mid next week and can take some photos. Here's a bit of info since I wont have photos/a thread for a few days:

The current chassis is kind of a mashup, used to be a tube framed strut based RX3, then it got converted to a double A arm FD body by a previous owner so there's a lot of weird reinforcement in the strut towers that doesn't need to be there. When we got it we tried to play by the rules and threw in an NA periph in but the Vipers and Corvettes were just too powerful and SCCA hamstrings rotaries in anything other than GT3 it feels link. Stage two/beta test is currently running a side port 20b and a modified Vortech V-2 Ti supercharger putting down roughly 570 to the wheels (we're not looking for power, but 30-45 minute full throttle longevity 3 times a weekend out as well as a full season of use). We've also mounted an efr 9180 on another 20b that's currently on our engine dyno that's waiting to get flogged, I'm hoping to see something like 750 to the crank and have a bulletproof platform but we'll see.

Also, concurrently, we'll be pulling out another more refined chassis that is going to get one of Logan @ Defined's 4 rotor beasts, I believe he's just finishing up the machining on the e-shaft and other smaller bits. Full slide throttle setup, the works. That'll be fun.


-Dave


P.S. I'll post a link here when I have something tangible to show you guys/photos. Thanks!

 

the newer Bosch EV14 injectors (ID included) feature a dynamic component that is significantly lighter than the older Bosch offerings and as such can work much better at lower duty cycles easily enabling an 850 idle even w a large primary port. better atomization also helps.

the OE primary port is miniscule. tiny. i spend lots of time make it much much larger for a couple of reasons, one of which is germane to the OP.

larger for more ultimate flow but also larger because...

the primary and secondary ports flow into the rotor chamber from opposite sides. i favor similar flow from each direction.

in addition, if we were to eliminate the secondary injector, the flow thru the port would contain little fuel. while all the charge goes back and forth within the LIM the AFR thru the secondary would be way lean.
i have no data on this but i like the idea of equal fuel airflow and AFRs thru the primary and secondary runners.

 

I agree, I have the Adaptronic modular ecu programmed for my 6-port Renesis/RX8 to only use the P1 primary injectors (ID750) until the SSV opens to allow intake air flow into the secondary ports. Then the four ID1300x for Sec & P2 positioned up higher in the manifold come on. When that occurs, P1 at the primary port drops back to 10% with 40% on P2 and 50% on Sec. I wanted to turn off P1 and have P2 & S2 both at 50% only, but I was concerned P1 might have issues turning on/off at the transition point and just settled on 10% instead.

The Mazda programming is to run out P1, then bring on Sec and run it out, then P2. The OE Sec & P2 are the same size and P1 are about 50% less flow rating. So you end up with a lot more fuel flow in Sec ports than Primary until the P2 finally kick in. Adaptronic found out on the dyno by instead balancing the fuel flow between primary and secondary ports a 6-port the Renesis engine picked up BHP through the entire curve with no other changes.

That's basically what I did, but in addition to balancing flow wrt to fuel flow distribution between primary & secondary ports, I took it a step further by also having the majority of the fueling using Sec & P2 injectors to come from the same positions up higher in the manifold during medium - high engine loading as an additional balancing step. Otherwise the primary injectors mostly handle low engine load conditions on their own. Another reason I set it up this way is because the E85 fuel is being used. The ID1300 have the stainless internals that support this more that the primary injectors don't. Competition car, so most of the time it's run under high load conditions, low load is tooling around the pits, loading on the trailer, etc.

Here's the dyno run showing the difference between OE injector staging vs the balanced staging that Adaptronic did. This is duplicating the same AFR, more could be had by leaning it out. The NA Renesis is best run around 13.1 AFR. Higher AFR will yield more power still, but at the expense of lower side seal life:

 

Looking forward to it. Thanks for the info!

 

You can run 1700s no problem. With newer ECU and EV14 injectors, idle and low load won't be an issue.