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Got an annoying problem preventing me from continuing with the tuning of my car. As my secondaries come on my VE drops substantially. It makes for terribly shaped VE map and is impossible to smooth out and fine tune. To me it indicates that my injector data is wrong for one of my stages. I’m using AEM infinity, and I have ID1050x primaries and ID2000 secondaries. AEM doesn’t have a preset for the 1050’s, but I’ve tried the ID1000/2000 presets and tried entering the Injector Dynamics info (emailed them and got the AEM specific offsets) with almost identical results. At idle 1200rpm, there’s a 20% VE difference if I run on 100% secondaries vs 100% primaries. Adjusting the flow rates even drastically doesn’t seem to effect the VE more then a few percent.
Am I wrong to think that I should be able to run the secondaries at such a low rpm at a similar VE? Or would my theory only apply at a higher load/rpm where the increased airflow makes up for the injector location? Or perhaps there’s another reason I’m not seeing. Thanks for any help, even if it’s just conjecture.
There will be more wall wetting from the secondaries and worse atomisation by the time the charge is in the chamber at idle. What manifold/throttle body?
Is your base fuel pressure close for the nominal injector flow ratings you are using?
Lower than expected VE would suggest you need to lower the dead time value you have for the secondaries If the observed AFR doesn't change much with table changes but you are at a low VE.
That size injector is probably pushing the friendship for ability to idle on petrol, if the secondary runners aren't flowing air if it's a factory style rx7 manifold/throttle won't be helpful either.
Sorry, I guess I should’ve shared a little more information. I’m using a GM LS3 drive by wire throttle body in a heavily ported OEM FD intake manifold, so the airflow in the secondaries aren’t restricted in anyway.
Base pressure is 43-44psi but is down to 37psi at idle around 50-55kpa. As it sits, VE at idle is around 50% on the primaries and 32% on secondaries.
Its also a Bridgeport if that factors in at all. Without a dyno it’ll be hard to hold a higher rpm load cell to see how changing injector flow rates might allow me to have them both netting a similar VE.
I can’t think of any other cause for the VE drop when the secondaries come on, but that’s why I came here. Tried watching all the related webinars, but that only reaffirmed my suspicions without getting me to a solution.
I believe Slides is referring to secondary injector placement in the LIM vs on the block rather than suggesting there are any restrictions due to the the factory throttle and its linkages.
Actual airflow if RX7 too, I can actually feel the torque drop at WOT in my fd3s with apexi, it seems the "warm up" throttles open at 70C.
Unrelated to the OP's issue but I'm keen to see some testing of your theory Slides, especially with a ported rotary it makes sense to block the secondaries for longer to keep air velocity up on the primaries. You need to upgrade that ancient apexi doorstop!
I don’t have a great pic with the TB off but this is what mine looks like. Not really related to the problem at hand, but since we’re posting pics of manifolds, lol.
Makes it clear you have air flow in all runners all the time.
I'm hoping to run the warm up throttles from the secondary charge air solenoid trigger when I go single. If I get frustrated with the Apexi I might try a Link or Motec. I'd say there is a pretty significant airflow/torque difference around 3000rpm, I will get some BMEP logs (Plex PCA2000) with that throttle set wired open and close (fuel and ignition optimised) to work out the difference but I think it is worth a fair bit of bottom end torque and should lower boost threshold too.