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Old 03-16-2013, 01:30 AM   #21
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MA70-3.0GT, fuel controllers aren't essential but they're a very good idea and I wouldn't try for that level of power increase without a basic SAFC II at the minimum. Just because a 550cc/m injector flows 125% of what a 440cc/m injector flows it doesn't mean they flow the same amount at idle, low load, mid loads, or even high loads. You may waste fuel, lose power or in some odd cases find that the 550s flow LESS at low or mid loads. Depending on if your ECU is setup to still run closed loop you could spend a lot of time running quite poorly (whenever the system is operating in open loop). A fuel controller isn't going to change the fuel cut level, that's determined by factors such as the duty cycle of the injectors (which IS affected by the size of the injectors).

Ochowdero, sure there are simpler piggybacks than the MAFT Pro or MAP ECU, etc. There are a lot of simpler devices with fewer functions and a ton of support... I'm sure you've hear of the SAFC, SAFC II, NEO all by Apex'i. These are just fuel controllers, the list is quite long. The functionality varies per device, some support data logging and some will integrate with an on-board wideband which I also strongly recommend (and it's essential if you're looking to tune on your own). There are independent units for timing control and boost control. The 'super piggybacks' roll all of these into one package which uses one app for data logging but often at the expense of a steep learning curve.
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Old 03-16-2013, 02:48 AM   #22
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No worries, I was under the impression from that write-up that fuel cut primarily based on the frequency of the signal from the kvafm (partly why the lexus body was used, with the adjustable "bypass" to allow more air to be flowed than the ECU believed), and the ECU then used the O2sensor to correct the resulting lean mixture using the fuel trim.
Then the 550cc injectors were required to "correct" the fuel trim back to the basic level by flowing more fuel for a given pulse width hence leaving more room to correct when boost increases.

All that worried me about the f-con was that modifying further the kvafm signal might affect fuel cut, but you're right it'd still cut at around 80-85% injector duty cycle so no probs.

I was thinking of building a fuel trim monitor using the Vf terminal in the diag. socket, that'd be nice to know what it's doing through the rev range (guess it'd help you pick up a slow switching O2 sensor too)

Anyway, not wishing to hijack the thread sorry ochowdero. so I'll do a bit more research & any questions I'll be sure to bore you with them cre
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Old 03-16-2013, 09:05 AM   #23
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Haha your not hijacking. I like this info. I'm working on building an engine to perform reliable power and durability but for a low.cost. This thread is about that (well the title doesn't say so but I intended it to progress this way)so thank you for you input!

I'm looking for a fuel pump, a good one. Strong!. Any recommendations?
My fuel filter is clogged or something else going on in my fuel system but I can't get my hands on a fuel compression tester. I'm going to do further testing to see why my car stalls when slowing down but I plan on replacing my fuel pump with a stronger one anyway.

Cre- yes. I'm looking at Acouple but I am not fully understanding what I'm looking at. I feel slight shocked cause I worked with them quite often. But I am just lost. Haha, I.think it's Because I thinking about everything and not focusing on a Part at a time.
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Old 03-16-2013, 06:32 PM   #24
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MA70-3.0GT, fuel cut is based on a couple factors.... I think I remember injector duty cycle, RPM and airflow being the primary factors although I could be wrong. It doesn't matter much for this situation as duty cycle is largely determined by the airflow signal.

The adjustable bypass screw on the KVAFM isn't a fuel cut device (that would be a side effect though). IMO, It's a crude hack to fix poor idle and low load issues when running in open loop. This is precisely where a fuel controller is the better system as otherwise you're still not managing any imbalances in the mid loads and you've only got one single adjustment to try to balance out a pretty big range. The O2 sensor has a very tight range of operation, isn't referenced under a number of circumstances. It's unreliable as a diagnostic device and I'd prefer not to bet the performance and safety of my engine on it. I don't believe in cheaping out on this stuff especially when doing a better and more trustworthy job/setup doesn't cost that much more.

The Vf circuit is a crap circuit for monitoring fuel trends real time, on a regular basis, especially on any non-stock setup. When I setup a data logging system on a TCCS type Toyota I usually add that to one of the monitored auxiliary inputs but it's yet to provide anything useful which wasn't made more obvious by better devices and much more quickly. A slower responding O2 isn't going to help, you'd be better off dampening the comparator circuit for your Vf meter. Dampening the actual O2 signal is going to affect your entire system. I know a couple of people love Vf but half of those who do still agree that unless the car is bone stock it's worthless and it's definitely no substitute for proper diagnostic devices (namely a wideband).


Ochowdero - If you have tuning experience then you should be fine with any of the 'super p/bs'. Just wire them up and if possible skip wiring in optional functions until you're ready to work with those. With some decent experience under your belt the things that are likely to make things difficult diminish in number quickly. Certain finer things such as tip in enrichments, decay rates and the like and then the functions related to converting to a different type of air flow measurement system should be the only things you'll have to do significant homework on... Even the timing control isn't too bad (but you probably aren't even going to want to use that).
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Old 03-16-2013, 08:04 PM   #25
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Cool, not suggesting anyone "cheap out" on mods that handle the safety of your engine, just feeling out the limitations of the stock system. I was thinking the lex AFM body was mainly for increased flow capability with bigger turbos anyhow,
but the reading I did seemed to suggest that fuel cut would come in at a set KVAFM signal frequency regardless of duty cycle/rpm etc hence the larger unit would be required once fuel flow capability & boost were increased in order to make use of anything above stock max airflow rate.

Just one thing on the O2, I wasn't saying to USE a slower switching O2, was saying that if a Vf monitoring device was used it may help detect if the O2 was slowing down with age/damage. (though thinking on it I guess a wideband O2 sensor & a monitoring system directly signalled by it's output would be much more informative on the things that matter anyway)

It'd still be nice to have a Vf monitor as well though, with a min/max data hold to keep an eye on how much "reserve capacity" is in the ECU's map at a given boost & fuel system spec...



I suppose most of the information written in the link was written back when f-con's were in their infancy & he felt the lex/550 was a better solution than the then-basic programming of said f-con's, so maybe not so relevant now that the companies have had 10-15 more years of development time. I guess it's glaringly obvious I haven't really looked into any of them & really I should as they likely have all the monitoring capability & more that I'd ever need or want.

EDIT-: just thinking about it, using a MAP based fuel controller would eliminate the problem of AFM restriction completely, and in theory the fuel cut feature should still operate based on the injector's duty cycle right?
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Old 03-16-2013, 08:15 PM   #26
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7mgte can be reliable and make power



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Old 03-17-2013, 12:52 AM   #27
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The Lex/550 mod isn't anything that's going to kill your car or leave you running so rich that gasoline is pouring out of your tailpipe. It's a cheap, crude mod and there are better options which cost little more (SAFC IIs are pretty damned cheap these days), provide more control and better power.

Ok, a Lex AFM housing may be used to limit restriction on any setup as you're reducing a bottleneck. The Lex/550 setup works under the gross assumption that a 25% increase in air needs a 25% increase in fuel... The problem here is that neither flows with linearity as duty cycle/volume increases. Most people who are trying to get the most they can out of their 550s are using a fuel controller and the Lex AFM is optional... In this case it provides some very subtle benefit in throttle responsiveness but it's not a lot (it is a little more noticeable with a big turbo but if you're running that large of a turbo these days you should be running a better EMS anyway). The stock intercooler and IC plumbing are just as much, if not more of a restriction than the stock AFM housing.

A peak/hold meter on the Vf signal would be useless. It's a dynamic output which is constantly fluctuating. The problem is the minute you let off the throttle it goes 0v and the minute you go 70% throttle or more it'll go ~4.8v, the rest of the time it bounces all over and you need to average it to get an overall trend. I think it's just a worthless light show unless you have it connected to an oscilloscope or a datalogger and the car is running in a controlled environment (just sitting out of gear with the engine held at certain RPM or on a dyno). With a data logger you have all the other operational stats to compare to the Vf readings but at that point you've already got more info than you need to determine the cause of a problem (because the basic feedback mode of Vf doesn't *really* tell you a thing). Reading it with a sluggish, analog multimeter will give you an averaged reading too (which the TSRM specifies). Vf is the most overrated and misunderstood diagnostic device on the MKIII. It is NOT an A/F indicator, it is NOT an injector or AFM diagnostic and it is NOT something you can use to tune your fuel controller. With a special TCCS service manual from Toyota and an oscilloscope it does tell you a LOT about the ECU's operation at any given point but I feel it's not helpful while it's actually in a car and not connected to a test bed. Ok, I'm done complaining about this particular system... /RANT

Wideband controllers run their own diagnostics on the sensor whenever they start up during the warmup cycle. They also usually have an 'emulated' narrowband output which you can connect in place for the signal line for the stock narrowband sensor so you may delete that unit. So you've got a diagnostic system, a sensor which accurately measures your fuel mixture (as opposed to the guesswork done by a narrowband), an output to simplify and supply your ECU with the older signal type it expects and you can change the signal range of the sensor's output and use it to adjust the fueling ( <-- I DO NOT RECOMMEND THIS). You can also recalibrate some wideband controllers to account for an aging sensor (Innovate Motorsports' controllers are usually ranked as the best when it comes to this.).

Air flow meter conversion is a separate entity. Some advanced piggy back's have this bundled in but there are units available which do nothing but convert from one type of meter to another. Yes, regardless of what system you convert to fuel cut will remain at relatively the same place unless fueling is changed too. Change the fueling you change the air flow scaling and then you change the fuel cut level. There are piggy backs for changing or eliminating the fuel cut level too and again some of the advanced ECU piggy backs have this bundled in, but it's still controlled separately of the air flow conversion functions.
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Old 03-17-2013, 01:15 AM   #28
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Nice post (and nice Vf rant lol), it's harder to find any electronic mods piggyback or otherwise for the MA70 in the UK than the US I think, so far found 1 HKS f-con & 1 GCC for same... and then the wiring loom separately for more money than both units together!!!

Ah well, I'm sticking with 11ish psi for now plenty good info in this thread at least
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Old 03-17-2013, 02:15 AM   #29
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You might look for US based retailers or eBay sellers who will ship to you... I think a number of them will. Also you should check ebay.COM as a lot of international sellers list there as opposed to their country's ebay site.

Fuel controllers are all pretty simple devices. Unless you absolutely MUST keep the stock wiring harness in tact it's not worth it to get a patch harness. It may be convenient but it's not as if we're talking about splicing and tapping 40 some wires.
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Old 03-18-2013, 07:58 PM   #30
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im going to read more up on fuel controllers and find one that fits me and my application.

i looked at the wideband controller and the one i saw, had a sensor thT GOES IN PLACE OF THE NARROWBAND thats all ready in the car?
these 2 devices, FC and WbC , i seldomly messed with. so im more on the "i need some knowledge on this equipment" side.
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