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298 Posts
Discussion Starter #1
heres my setup

-sc300 with a jdm 2jzgte
-using the jdm ecu
-stock fuel with a supra tt denso pump
-12v fuel pump ecu mod
-70mm single turbo only @ 10psi

it idles perfect and runs perfect and no check engine lights.

i have a aem wideband gauge about 4-6 inches away from the turbine housing. cold start my afrs are at 12 after it warms up it goes to 14.5-15.5. cruising on the freeway at holding the throttle constant its at 14.5 to 14.7.

heres the thing...

if im driving and holding it steady at partial throttle at about 2500-3000 rpm's afr's are fine at 14.7... if i immediately go 100% throttle from there it goes lean to about 16 to 17 afr for a second then goes right to 10 to 10.5 and stays there.

and if im cruising then lay into the throttle a little bit more like trying to pass someone it goes to about 16 afr... but im probably only at like 30% throttle and in vac or maybe 1 to 2 psi of boost.... is that normal? and from there if i mash it all the way it goes right to 10 again... like if i go past a certain throttle % it completely goes rich again
 

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Engmaineer
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is that normal? lol noooooooooo

You will be melting a piston soon sir.

Your running a 70 mm, with no piggy back or anything . . . not to smart.
 

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Discussion Starter #3
the cars only been up and runnng for about 2 months... and i dont ever drive it... like once a week if that much. and most of the time i never get on it.

it just seems like either the gauge or fuel is trying to catch up. right when i stomp on it it swings to 17 for a split second then goes right to 10.5 or so. sometimes it takes a sec sometimes its less... it never stays 17. and when its at 17 my rpms are at about 3000 and beginning to build boost
 

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Not so boring anymore
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If its only in lower rpms and no boost, I wouldn't worry about it too much it wont hurt anything really, just drive like poo.
 

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Discussion Starter #7
yeah I want vpro or at least a map ecu2 for now with larger injectors but not enough funds at the moment.

I have a safc2 but I also have a bcc. But those 2 don't work together on a map based only car since both the afc and bcc both intercept the map signal

Some people are telling me to get larger injectors, ditch the bcc and use the afc to lean out the car to the target afr and it also lowers the voltage so it won't hit boost cut. But then my timing will be a little off due to the afc altering the maps to pull fuel
 

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Engmaineer
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2,408 Posts
yeah I want vpro or at least a map ecu2 for now with larger injectors but not enough funds at the moment.

I have a safc2 but I also have a bcc. But those 2 don't work together on a map based only car since both the afc and bcc both intercept the map signal

Some people are telling me to get larger injectors, ditch the bcc and use the afc to lean out the car to the target afr and it also lowers the voltage so it won't hit boost cut. But then my timing will be a little off due to the afc altering the maps to pull fuel
Ya I tried to wire up a BCC and SAFC2 to a jdm car. I told the owner I didn't think it would work. But I put the BCC in line after the SAFC. So if I modified a signal , it would clip the signal and bring it right under the cut off voltage for the fuel cut. Sounds like a great idea by concept, didn't work of course.

Your timing is already way off. Boost doesn't matter, the volume of air that is being delivered to the motor does though. The stock ecu at 100% throttle is going straight off pre-programmed fuel/ timing tables, those tables were designed some smaller twins. At the low rpm, its expecting the sequential setup. Small amount of air when the first turbo is on, then the big one joins in as rpms grow, and more air is delivered.

Your 1 second of acceleration is probably pointing to a section of the map when that small ammount of air is starting (first turbo boosting), when it kicks over to a higher rpm it fattens up because it believes the 2nd turbo is now flowing a decent amount of volume hard.

With your bigger 70mm your map is way off, fuel and timing.
 

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Discussion Starter #9
yeah the lean afr's worried me a but... but in boost it stays right at 10... ive never even seen it hit 12 even if i slowly bring the boost to 15 psi. but at the initial tip in it sweeps over to lean then right back over to rich.

you think my timing tables are off enough to cause detonation?
 

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yeah I want vpro or at least a map ecu2 for now with larger injectors but not enough funds at the moment.

I have a safc2 but I also have a bcc. But those 2 don't work together on a map based only car since both the afc and bcc both intercept the map signal

Some people are telling me to get larger injectors, ditch the bcc and use the afc to lean out the car to the target afr and it also lowers the voltage so it won't hit boost cut. But then my timing will be a little off due to the afc altering the maps to pull fuel

you need to daisy chain the two together and it works perfect ^^^^^^^^^
 

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If you are set on piggy back I say AEM FI/C get tuned and call it a day. It also has a built in map that can take over to alleviate any boost cut
 

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Discussion Starter #12
I looked into those too.

That's what you're hooking up in your 1j sc right? Did you ever get it running?
 

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Originally I was but now I have the Race AEM Standalone Box with custom harness. The FI/C is what we have ran on a few cars that were on a budget or just didnt have the need for a multi-thousand dollar standalone. It is on Jason's (Crunk) GS300 with the stock twin 2jz vvti swap making about 400rwhp. Only downfall we have noticed on some cars is with certain engines/manifolds that tend to boost creap you cannot set a boost cut with the FI/C but to my knowledge you cant with any piggy back.

My car is getting a new engine, bigger single, and couple other things before it comes out
 
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