Boost and Fuel...hack this, FMU that...
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Boost and Fuel...hack this, FMU that...
Ok, before sending me a search link please just finish reading my post. I have only gathered more questions since I began searching for my original answers. As far as fuel management goes. You can use <U>either</U> check valves with an FMU, only a missing link, or only the AFC hack, but no two together will work. Right? Which is the safest, most reliable? Can I use the missing link with larger injectors on the stock computer? I know you are supposed to use 440's with the AFC hack and then lean it out...why not just use smaller injectors with the AFC hack. Last but not least, why does the FMU suck? Is it only because it only assists the ECU under boost? What gives? Thanks
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Joined: May 2001
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From: Trinidad, W.I.
Re: Boost and Fuel...hack this, FMU that... (-TRINiTRON-)
Lord... it seems you haven't read much in your 'search'.... or are totally confused.
I'll try to help here.... your options are as follows (aside from an engine mgt):
A) FMU + In line fuel pump + Check Valves OR Missing Link (pick one) + OEM Injectors
B) VAFC + Larger Injectors
The reason (A) works:
Your honda uses a MAP sensor to determine how much air is coming into the motor and sends a voltage signal (from 0-3v) to the ecu, which determines your fuel map... problem is... once it 'sees' boost, the ecu goes WTF !?! (Boost is OVER 3volts) and kills the party, so you need to add a missing link OR a series of check valves that bleed off excess air pressure (boost) before the MAP sensor sees it. Hence the ECU thinks it's all good and the ECU delivers fuel and timing maps as usual. (Keep in mind...the Honda MAP sensor is ABLE to read up to 11psi of boost, but the ECU is designed to work only to 0psi)
The FMU increases fuel pressure relevant to boost pressure by a fixed ratio (4:1, 6:1, 10:1...etc...) depending on which one you have. Say you have a 10:1 FMU.... your car has 240 injectors that run, say, 40 psi fuel pressure at idle. The 10:1 FMU will increase your fuel pressure +10Psi for every pound of boost it sees (The FMU has a vacuum line connected). So lets pick round figures and say you run 10psi of boost. That's 40psi stock pressure + the increase of the FMU... 10:1 FMU X 10psi of boost= 100psi MORE fuel pressure. This increase in fuel pressure allows your injectors to pass more fuel w/o physically altering the injector.
The problem in this setup is this... the FMU can easily add soo much fuel pressure that your stock pump can't keep up. Since your stock fuel pressure regulator only increases at a 1:1 ratio... your pump typically will only see about a 20psi jump in pressure at full throttle. (40psi + 20psi at WOT= 60psi). BUT with the addition of the FMU, your new pressure at WOT and 10psi of boost is more like 140psi of fuel pressure. Your stock pump doesn't do too well over 90psi !!!
To fix this... you'd need to add the last part, an inline fuel pump. The inline allows your stock intank pump to take it easy... and ups the fuel pressure. Which WORKS, but the increase fuel pressure is putting your other fuel components under alot of stress (injectors). So you risk certain things with this setup, tho it works.
The reason (B) works:
Adding larger injectors, like 450cc's, you are essentially doubling the flow rate of your stock units. These large injectors are still controlled by the stock ecu, which thinks the units are 240's, so it opens them for the pre programmed amount of time (milliseconds). Opening for that long on a larger injector just floods the motor w/ too much fuel at idle and above, so you need to adjust the fuel flowing rate (controlled by the MAP sensor).
The VAFC hooks inbetween your MAP sensor signal and the ECU... the AFC alters the voltage going to the ECU and can 'tell' the ecu that it needs to adjust the fuel flow to compensate for the larger injector. The AFC is adjusted by the user/tuner and they can 'back out' fuel, so the injectors don't flood the engine. It does this by lowering the voltage at idle from the MAP sensor. This, in turn, reduces the amount of fuel the injectors are spitting....allowing your stock ecu to 'idle' the large injectors... and also allows the ecu w/ the help of the AFC, to provide enough fuel to run the car properly. (The AFC is adjusted in rpm increments)
Now the AFC takes OUT voltage going to the ECU from the signal sent by the MAP, so the ECU never 'sees' boost AND you don't need to add the check valves OR Missing Link. Even tho the MAP is sending the signal that boost is present. Since you don't use anything to chance the fuel pressure... you don't really need to worry about high pressures.
The two main problems are that the AFC cannot adjust fuel at ANY spot.. only pre determined rpm ranges. AND The AFC is backing out so much from the MAP sensor signal to idle and run the larger injectors... that we DO NOT know what the ECU is doing to the ignition timing at that time. (That's why people back out distributor timing when running an AFC setup). But that's a whole other issue (ecu advancing timing at low boost/partial throttle... do a search...heh heh heh)
OK...borded of typing... but that should be a good run down for you to start understanding the difference between the setups. And keep in mind the cost of all the parts involved... an FMU setup can easily get up to the price of an AFC+Injectors. There is more... but this is a start...
X2
I'll try to help here.... your options are as follows (aside from an engine mgt):
A) FMU + In line fuel pump + Check Valves OR Missing Link (pick one) + OEM Injectors
B) VAFC + Larger Injectors
The reason (A) works:
Your honda uses a MAP sensor to determine how much air is coming into the motor and sends a voltage signal (from 0-3v) to the ecu, which determines your fuel map... problem is... once it 'sees' boost, the ecu goes WTF !?! (Boost is OVER 3volts) and kills the party, so you need to add a missing link OR a series of check valves that bleed off excess air pressure (boost) before the MAP sensor sees it. Hence the ECU thinks it's all good and the ECU delivers fuel and timing maps as usual. (Keep in mind...the Honda MAP sensor is ABLE to read up to 11psi of boost, but the ECU is designed to work only to 0psi)
The FMU increases fuel pressure relevant to boost pressure by a fixed ratio (4:1, 6:1, 10:1...etc...) depending on which one you have. Say you have a 10:1 FMU.... your car has 240 injectors that run, say, 40 psi fuel pressure at idle. The 10:1 FMU will increase your fuel pressure +10Psi for every pound of boost it sees (The FMU has a vacuum line connected). So lets pick round figures and say you run 10psi of boost. That's 40psi stock pressure + the increase of the FMU... 10:1 FMU X 10psi of boost= 100psi MORE fuel pressure. This increase in fuel pressure allows your injectors to pass more fuel w/o physically altering the injector.
The problem in this setup is this... the FMU can easily add soo much fuel pressure that your stock pump can't keep up. Since your stock fuel pressure regulator only increases at a 1:1 ratio... your pump typically will only see about a 20psi jump in pressure at full throttle. (40psi + 20psi at WOT= 60psi). BUT with the addition of the FMU, your new pressure at WOT and 10psi of boost is more like 140psi of fuel pressure. Your stock pump doesn't do too well over 90psi !!!
To fix this... you'd need to add the last part, an inline fuel pump. The inline allows your stock intank pump to take it easy... and ups the fuel pressure. Which WORKS, but the increase fuel pressure is putting your other fuel components under alot of stress (injectors). So you risk certain things with this setup, tho it works.
The reason (B) works:
Adding larger injectors, like 450cc's, you are essentially doubling the flow rate of your stock units. These large injectors are still controlled by the stock ecu, which thinks the units are 240's, so it opens them for the pre programmed amount of time (milliseconds). Opening for that long on a larger injector just floods the motor w/ too much fuel at idle and above, so you need to adjust the fuel flowing rate (controlled by the MAP sensor).
The VAFC hooks inbetween your MAP sensor signal and the ECU... the AFC alters the voltage going to the ECU and can 'tell' the ecu that it needs to adjust the fuel flow to compensate for the larger injector. The AFC is adjusted by the user/tuner and they can 'back out' fuel, so the injectors don't flood the engine. It does this by lowering the voltage at idle from the MAP sensor. This, in turn, reduces the amount of fuel the injectors are spitting....allowing your stock ecu to 'idle' the large injectors... and also allows the ecu w/ the help of the AFC, to provide enough fuel to run the car properly. (The AFC is adjusted in rpm increments)
Now the AFC takes OUT voltage going to the ECU from the signal sent by the MAP, so the ECU never 'sees' boost AND you don't need to add the check valves OR Missing Link. Even tho the MAP is sending the signal that boost is present. Since you don't use anything to chance the fuel pressure... you don't really need to worry about high pressures.
The two main problems are that the AFC cannot adjust fuel at ANY spot.. only pre determined rpm ranges. AND The AFC is backing out so much from the MAP sensor signal to idle and run the larger injectors... that we DO NOT know what the ECU is doing to the ignition timing at that time. (That's why people back out distributor timing when running an AFC setup). But that's a whole other issue (ecu advancing timing at low boost/partial throttle... do a search...heh heh heh)
OK...borded of typing... but that should be a good run down for you to start understanding the difference between the setups. And keep in mind the cost of all the parts involved... an FMU setup can easily get up to the price of an AFC+Injectors. There is more... but this is a start...
X2
Joined: Mar 2003
Posts: 616
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From: Grand Rapids, MI, USA
Re: Boost and Fuel...hack this, FMU that... (m R g S r)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by m R g S r »</TD></TR><TR><TD CLASS="quote">Very informative, but I'd like to hear more about the ECU advancing the ignition timing at partial throttle/low boost....</TD></TR></TABLE>
The AFC hack advances ignition timing at partial throttle/low boost
The AFC hack advances ignition timing at partial throttle/low boost
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From: Pembroke Pines, Florida, United States
Re: Boost and Fuel...hack this, FMU that... (InTeGrA B18b1)
I was thiking of a easy way for people to understand the afc hack. this is what i've come up with so far. if you can understand that the sensor/ecu works off voltage range, and that the afc modifies the voltage the ecu sees then it should be easy to understand
Voltage range
.............0V.............................3V
.............-30.............................0.............................30psi (Stock map sensor)
-30.............................0..........11.................30psi (AFC Hack)
Voltage range
.............0V.............................3V
.............-30.............................0.............................30psi (Stock map sensor)
-30.............................0..........11.................30psi (AFC Hack)
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Honda-Tech Member
Joined: May 2001
Posts: 5,089
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From: Trinidad, W.I.
Re: Boost and Fuel...hack this, FMU that... (InTeGrA B18b1)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by InTeGrA B18b1 »</TD></TR><TR><TD CLASS="quote">i hope he just found that somewhere. If you typed that you got some time on yo hands.</TD></TR></TABLE>
Ummm... I typed it...
Didn't take long at all... I type really fast.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">The AFC hack advances ignition timing at partial throttle/low boost</TD></TR></TABLE>
Correction... the AFC hack does NOT affect ignition timing whatsoever. The ONLY thing the AFC does is affect fueling and vtec x-over points.
The reason the hack has potential issues with timing is this (I'll try to be brief this time):
The honda ECU advances and retards timing according to engine need, using input from the MAP sensor as well as intake air temps and other sensor input to determine whether it should advance timing events (producing more heat and a more complete burn, ie, more power) or retard it to reduce the timing of the power stroke, producing less heat and an inefficient burn, worse gas mileage..etc... It all depends on the engine's needs at the rpm/throttle position, MAP, etc...
The 'hack' lowers MAP signal so drastically, that the ECU may see the need to drastically advance timing at certain points to produce the desired power (tq) to get the car moving. REMEMBER, even tho the car's boosted, the ECU still thinks everything is the same (thinks it's still N/A). So under partial throttle, the ignition timing is still under ECU control. This is where some people think the 'hack' has it's weakness. When the ECU sees such low numbers from the MAP (caused by the AFC altering voltage) it may be inclined to advance timing to increase power production at that throttle position. And as you may know... advancing timing increases the possibility of very damaging detonation...particularly in a boosted car. At WOT, the ECU switches to prewritten fuel and ignition tables.... so it's not so much of an issue.
X2-- A man with time on his hands....
Ummm... I typed it...
Didn't take long at all... I type really fast.<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">The AFC hack advances ignition timing at partial throttle/low boost</TD></TR></TABLE>
Correction... the AFC hack does NOT affect ignition timing whatsoever. The ONLY thing the AFC does is affect fueling and vtec x-over points.
The reason the hack has potential issues with timing is this (I'll try to be brief this time):
The honda ECU advances and retards timing according to engine need, using input from the MAP sensor as well as intake air temps and other sensor input to determine whether it should advance timing events (producing more heat and a more complete burn, ie, more power) or retard it to reduce the timing of the power stroke, producing less heat and an inefficient burn, worse gas mileage..etc... It all depends on the engine's needs at the rpm/throttle position, MAP, etc...
The 'hack' lowers MAP signal so drastically, that the ECU may see the need to drastically advance timing at certain points to produce the desired power (tq) to get the car moving. REMEMBER, even tho the car's boosted, the ECU still thinks everything is the same (thinks it's still N/A). So under partial throttle, the ignition timing is still under ECU control. This is where some people think the 'hack' has it's weakness. When the ECU sees such low numbers from the MAP (caused by the AFC altering voltage) it may be inclined to advance timing to increase power production at that throttle position. And as you may know... advancing timing increases the possibility of very damaging detonation...particularly in a boosted car. At WOT, the ECU switches to prewritten fuel and ignition tables.... so it's not so much of an issue.
X2-- A man with time on his hands....
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Joined: Jan 2001
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From: Portland, OR
Re: Boost and Fuel...hack this, FMU that... (Poop111444)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Poop111444 »</TD></TR><TR><TD CLASS="quote">
The AFC hack advances ignition timing at partial throttle/low boost </TD></TR></TABLE>
well no..the afc cannot control timing...the honda ecu does that. And it wont advance it anymore then if you were running a FMU.
liam
The AFC hack advances ignition timing at partial throttle/low boost
</TD></TR></TABLE>well no..the afc cannot control timing...the honda ecu does that. And it wont advance it anymore then if you were running a FMU.
liam
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Joined: May 2001
Posts: 5,089
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From: Trinidad, W.I.
Re: Boost and Fuel...hack this, FMU that... (liam821)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by liam821 »</TD></TR><TR><TD CLASS="quote">
well no..the afc cannot control timing...the honda ecu does that. And it wont advance it anymore then if you were running a FMU.
liam</TD></TR></TABLE>
Would you elaborate on this ? The FMU setups does not affect MAP signal at all and although I haven't seen hard numbers on this... the effect of the AFC should affect ignition timing... or at the very least, prolong the duration of the ecu's advance....
I wonder why no one ever hooks a timing light up at the dyno to plot this...lol
well no..the afc cannot control timing...the honda ecu does that. And it wont advance it anymore then if you were running a FMU.
liam</TD></TR></TABLE>
Would you elaborate on this ? The FMU setups does not affect MAP signal at all and although I haven't seen hard numbers on this... the effect of the AFC should affect ignition timing... or at the very least, prolong the duration of the ecu's advance....
I wonder why no one ever hooks a timing light up at the dyno to plot this...lol
Joined: Oct 2000
Posts: 4,440
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From: Surrey, BC, Canada
Re: Boost and Fuel...hack this, FMU that... (X2BOARD)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by X2BOARD »</TD></TR><TR><TD CLASS="quote">
I wonder why no one ever hooks a timing light up at the dyno to plot this...lol</TD></TR></TABLE>
Have you ever tried to read a timing light while revving a motor? Hard to hold it steady enough... but I get about 30 deg timing at 3k, steady-state Who knows (or can tell) what happens when the engine is at WOT! Maybe a steady-state dyno could tell us...
Thank you for the post
Pretty much summarized what I understood and condensed the 10-page 'official afc hack' thread into one or two posts 
I wonder why no one ever hooks a timing light up at the dyno to plot this...lol</TD></TR></TABLE>
Have you ever tried to read a timing light while revving a motor? Hard to hold it steady enough... but I get about 30 deg timing at 3k, steady-state
Who knows (or can tell) what happens when the engine is at WOT! Maybe a steady-state dyno could tell us... Thank you for the post
Pretty much summarized what I understood and condensed the 10-page 'official afc hack' thread into one or two posts
Joined: Sep 2003
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From: lebanon, pa, 17042
Re: Boost and Fuel...hack this, FMU that... (X2BOARD)
You seem to really know your **** about this i'll ask you my question. I have searched and have found mixed results. With a 96-99 greddy turbo kit for a integra gsr, is it possible to rewire the plug and use an obd1 plug and use the fmu, it is basically the same setup just different pinout locations any help would be greatly appreciated. Thank you.
vtec-power of dreams
vtec-power of dreams
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Joined: Jul 2001
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From: Colorado, USA
Re: Boost and Fuel...hack this, FMU that...
thanks for all the info X2, I'm a super nOOb when it comes to boost (in the thinking about it in the future process) so posts like this really help me out. Thanks a bunch
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Joined: May 2001
Posts: 5,089
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From: Trinidad, W.I.
Re: Boost and Fuel...hack this, FMU that... (eg6gsr)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by eg6gsr »</TD></TR><TR><TD CLASS="quote">You seem to really know your **** about this i'll ask you my question. I have searched and have found mixed results. With a 96-99 greddy turbo kit for a integra gsr, is it possible to rewire the plug and use an obd1 plug and use the fmu, it is basically the same setup just different pinout locations any help would be greatly appreciated. Thank you.
vtec-power of dreams</TD></TR></TABLE>
Are you talking about an FMU, or the Greddy Blue box ? (sounds like the box)
vtec-power of dreams</TD></TR></TABLE>
Are you talking about an FMU, or the Greddy Blue box ? (sounds like the box)
Joined: Oct 2000
Posts: 4,440
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From: Surrey, BC, Canada
Re: Boost and Fuel...hack this, FMU that... (X2BOARD)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by X2BOARD »</TD></TR><TR><TD CLASS="quote">You're welcome.... hey... I can't talk smack ALL day... right ?</TD></TR></TABLE>
That depends on how fast you think you are
That depends on how fast you think you are
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