2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

boost / fuel question

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Old Jun 7, 2002 | 12:31 AM
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boost / fuel question

I`m getting 1500's for secondaries, primaries will be still 550's..

I have S-AFC and S-ITC and would have custom made boost controller with high/low settings controller by in cabin switch (electronic)

Its cool to have stock/high boost settings, but what about fuel? If i will tune my S-AFC for high boost position of switch, my car would run way too rich on stock boost setting...

Any ideas ?

What is stock boost on Series 4 turbo and how high i could go ?

Would be 1st gen S-AFC (no LCD) able to tune those 1500's down to some decent numbers ?
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Old Jun 7, 2002 | 12:56 AM
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1500's?? that seems like to much for your mods, also your planning on replacing the fuel rail right? Also, I would not advise using a S-AFC with that type of fuel set up, you really need a total stand alone system. Why not 720's and a S-AFC? are you upgrading the turbo to a full T04?
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Old Jun 7, 2002 | 01:11 AM
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1500's would be modified to fit stock fuel rail (by Tim at RPM Performance)

standalone (E6K) would come by end of year, but for now i want to make it running with S-AFC / S-ITC

fuel pump - walbro 255lph high pressure, rewired
turbo - stock S4 unit, ported wastegate, removed twinscroll
intercooler - for now probably stock, later Greddy FMIC, probably water injection too
other mods - lightweight (4,3kg) steel flywheel, heavy duty ceramic button clutch, ported TB, removed all emissions & solenoids, ported intake, dual alternator underdrive pulley, RPM Performance billet alu BOV, intake, downpipe, midpipe, FCD

all i will have for tuning (no dyno) will be air fuel ratio monitor and Defi Boost & EGT gauges...

still hoping to get answers

1) what are stock boost levels and where i should set HIGH boost

2) is it way to controll fuel on both settings or would i have to tune it for HIGH setting and have it on all time till i`ll get E6K ?
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Old Jun 7, 2002 | 01:42 AM
  #4  
NZConvertible's Avatar
I'm a boost creep...
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Re: boost / fuel question

Originally posted by hIGGI
I`m getting 1500's for secondaries...

Would be 1st gen S-AFC (no LCD) able to tune those 1500's down to some decent numbers ?
Those are far too big to be controlled by an AFC or S-AFC. You'll never get then down enough for suitable mixtures. Either find some smaller injectors or wait for the Haltech.
If i will tune my S-AFC for high boost position of switch, my car would run way too rich on stock boost setting...
It doesn't work like that. The ECU calculates fuelling based on airflow, so when the boost is lower, the airflow is lower and less fuel is supplied. Tune it on the high boost setting.
Being able to switch between stock boost and a higher setting is useful. Basically it's a "wet road/dry road" switch!
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Old Jun 7, 2002 | 02:05 AM
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the newer AFC goes to max -50%. so your injectors at max removed are still way bigger then stock... you can't control that big with the S-AFC

stock is 5.5psi. if you're on stock turbo and IC max about 12. which you don't even need bigger injectors for. just get a big pump.
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Old Jun 7, 2002 | 02:06 AM
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NZ Convertible

so u are saying if i`ll tune it for high boost, low boost switch would not make it running too rich ? atleast one good thing ;o)

i know my S-AFC is not best solution, but wasn`t cym running 1600's in secondaries on stock ECU even without S-AFC ?
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Old Jun 7, 2002 | 02:51 AM
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on same basis like S-AFC controls injectors there should be way to fool ECU more than how S-AFC it does...

basically what it does ? changes original voltage output from AFM to ECU ?
if i`ll put something inline (ie voltage regulator) what will drop it down more, i should be ok, right ?
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Old Jun 7, 2002 | 11:14 AM
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DSM people have put potentiometers (variable resistance) inline between the ECU and AFM. Not sure how this will affect cruise and WOT on an RX7 though, just get the stand alone and do it the right way.
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Old Jun 7, 2002 | 01:17 PM
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Ryde _Or_Die's Avatar
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Originally posted by Scott 89t2
stock is 5.5psi. if you're on stock turbo and IC max about 12. which you don't even need bigger injectors for. just get a big pump.
So would my walbro fuel pump be good enough for intake/DP/MP? Without a s-afc? I think I am running rich right now anyways but am not positive. If so I will get my gauges all installed an order my 3" DP/MP this week.
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