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ok if i buy bigger injectors r they ran by the ecu?what i mean is since is the ecu is used to running 240cc and i buy 320cc will it compensate for them on its own or do i have to tune?basically will it just keep sprayin the same amount of fuel through bigger injectors or no

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no it wil be different. your ecu controls the injectors and is spraying them at a certain duty , at a certain vacuum , or load , at a certain rpm , blah blah. well if at 3000 rpm , your ecu is spraying 35% duty , 35% duty of bigger injectors is more than 35% of stock. if you follow. plus the ecu will not be getting the A/F its looking for , basically will confuse the hell out of it and make it run like ass. if your putting bigger injectors in , you need fuel managment to control it , thus the name fuel managment , lol.

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Duty cycle is part of it. How the ECU actually controls the injectors is in a pulse width modulated cycle. The injectors fire in a pulse measured in milliseconds (thousandths of a second). The ECU will make some adjustment in open loop but nowhere near enough to account for injectors that flow more than stock by any appreciable amount. It will run pig rich if it will start at all. An FMU, re-tuned PCM, or a piggy back fuel controller will be needed. I'd go the PCM route if possible.

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Well i think they will but it wont be that bad becouse i went from my jdm ITR injectors to 370;s runnin it with my chiped p28 i smoked liek a mofo....SOLVED IT BY buyin a used AEM EMS throwin it on the dyno to come realize my tuner put on the aem i got 440's so i ran rich still,we fixed it, ever since then cars runin like a CHAMP... i thynk with a vafc or neo you can controll 320cc inj. good luck!

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alright thanks guys.i talked to some dude who said he will sell me a p28 chipped and a basemap for me that will run them.but i think im still gonna go with an afc and pressure regulator just to be safe.def dont wana go lean so ya.one more thing.has neon heard of peak performance cams?i jeard their profiles r very similar to skunk 2 2s or jun 3s but i dont know how good they r but a guy said he will sell me a used set with 2500 miles on them and skunk 2 cam gears for 325.what do u guys think?

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ecu is set to in case of anything, just go with the running rich option to avoid lean (detonation) but a tuner just setting it to too rich is just wrong!

 

 

You do know it's possibly to have detonation with overly rich conditions too. Seen mostly in FI applications but it does happen.

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You do know it's possibly to have detonation with overly rich conditions too. Seen mostly in FI applications but it does happen.

 

have some documented cases of this being because of the rich condition, and not due to some other underlying issue, because I have never heard of this before.

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have some documented cases of this being because of the rich condition, and not due to some other underlying issue, because I have never heard of this before.

 

 

I don't but it was covered by an EFI tuning seminar I took. Has to do with charge density, charge stratification, and how overly rich AFR's slow down the flame front during a combustion event. I know there are ways of taking advantage of it too. Upper class NMRA cars run non-intercooled turbo/supercharger combos with AFR's in the 8's and a rather unconventional timing scheme.

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you guys are assuming fuel is only cause of detonation. theres 2 variables , timing advance an fuel. so if your engine has detonation , which for those who dont fully understand what it is , its when the fuel/air mixture , is igniting on its own before the spark plug sets it off. theres 2 fixes , better fuel , or less timing. you retard timing so the plug goes off before it preignites at whatever rpm or condition it is happening.

 

and yes , rich can cause detonation as well. i know from experience now. while playing with my car and say after datalogging a pull , notice a point between 5k and 55k rpm where my A/F is 14.3:1. so i go into my maps , make adjustments to increase fuel at that rpm/load/cam advance. than go do another pull. during pull , at said rpm , i get spark knock(plus i have Kpro set so my CEL will flash when knock is detected by the knock sensor , sweet option) , i was like wtf , lol. i abort the mission , lol. go into my high cam timing maps for what cam advance i was running(40 degrees dvance) , and pull a few degrees timing out of it. i actually pulled timing out from 5k to 8500. just to be safe. once A/F is perfect , i can than play with timing , and various octane fuels , teehehehe. plus ill have cams soon so , the fun begins.

Edited by cranny
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and yes , rich can cause detonation as well. i know from experience now. while playing with my car and say after datalogging a pull , notice a point between 5k and 55k rpm where my A/F is 14.3:1. so i go into my maps , make adjustments to increase fuel at that rpm/load/cam advance. than go do another pull. during pull , at said rpm , i get spark knock(plus i have Kpro set so my CEL will flash when knock is detected by the knock sensor , sweet option) , i was like wtf , lol. i abort the mission , lol. go into my high cam timing maps for what cam advance i was running(40 degrees dvance) , and pull a few degrees timing out of it. i actually pulled timing out from 5k to 8500. just to be safe. once A/F is perfect , i can than play with timing , and various octane fuels , teehehehe. plus ill have cams soon so , the fun begins.

 

i extremely dis-like you :p

Edited by Hatch92
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you guys are assuming fuel is only cause of detonation. theres 2 variables , timing advance an fuel. so if your engine has detonation , which for those who dont fully understand what it is , its when the fuel/air mixture , is igniting on its own before the spark plug sets it off. theres 2 fixes , better fuel , or less timing. you retard timing so the plug goes off before it preignites at whatever rpm or condition it is happening.

 

that is not detonation, that is pre-ignition which can lead to detonation, but not always.

 

detonation is defined by the erratic uncontrolled burn, where multiple supersonic flame fronts collide (instead of just one sub sonic front).

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