i noticed that filetofit is building DIY maplimiters to use to do the same purpose as an apexi AFC, anyone else use this >? downsides ? upsides ? etcc thanks

 

... i am planning on building one in the next week or so... i just got the parts list and schematic... now i just gotta pick up the parts... also, ion_four is running one ((or used to))... late...

 

Filtofit has one he's selling. He makes them and uses them. I'm gonna get one soon, but I don't have injectors yet. Try searching that name on here and he should have the info you need.

 

If you want to build one yourself you can get free samples of the chip I use at
http://www.national.com Do a search for LM6134AIN. Also you can find my circuit design at http://www.angelfire.com/ab7/diymaplimiter

I sell them built for $20 shipped ($21 if you use Paypal).

The principle is the same as the AFC hack, you scale down the MAP sensor voltage that the ECU sees in conjunction with larger injectors.

 

Just got my Filetofit circuit in today,

I will let you know how it turns out!

but as a customer service guy and someone who tries to help you out whenever he can

Filetofit =

 

ive been running the circuit for a few weeks now, and all i can say is WOW!! @ 7psi intercooled on a stock d16z6 w/ the 450cc injectors, my car DOES NOT even think about leaning out under full boost, and breaks the tires loose all the way into 4th gear. Im running stock fuel pressure, with a stock fuel pump, idle is gorgeous at 800rpm and there is no delay when i romp on the pedal.

this circuit is amazing and far cheaper than getting a vafc, and MUCH cheaper than a hondata.

i recommend this setup to anyone running boost to get rid of those crappy FMU which is just running risky high fuel pressure which will eventually just ruin ur injectors.

 

Glad to see it's working out well for you!

 

any pics of a completed product? Thanks

 

I just posted a pic on the website, http://www.angelfire.com/ab7/diymaplimiter

 

yeah filetofit is a good guy, we just got off on the wrong foot

Rob


[Modified by rjardy, 9:45 PM 10/1/2002]

 

Hmmn interesting. So can you adjust at different RPM levels as well?? Sounds cool for the price..

 

Yeah Rjardy's a good dude, just make sure you use the quote feature correctly.

The circuit I made isn't RPM adjustable, it's boost adjustable. You tune the MAP cut at two different points, idle and WOT.

 

so this just scales the map voltage from a max of 5V at 11psi to about 2.8V at 11psi? drop in 450cc injectors and you're on you're way with no CELs?

only concern is the ecu is in closed loop and will be trying to force 14.7:1 while in boost. or am i missing something. pretty cool though. so simple.

 

The ECU goes into open loop at a certain percent throttle based on the TPS, not sure exactly how much throttle it takes to trip into open loop.

It's basically the same thing as the AFC hack and I haven't heard of anyone having any problems running the hack vis-a-vis part throttle open loop detonation.

 

cant you turbos boost at like 60% throttle? In this case the ECU will be in closed loop. ecu wont go open loop until close to WOT...when the tps voltage approaches 4.5V

i am still amazed the stock ecu can shorten injector pulsewidths so much as to allow this to work. its awesome! i guess zip's SMC is a slightly more flexible version of this.

i am tempted to try this just for grins...maybe even tie a wideband o2 in with it so that the gain of the feedback loop is adjustable to maintain a target air/fuel ratio. how cool would that be?

 

filetofit : .... if i wanted to build one of these custom circuits myself, how would i know what resistance to set the 3 potentiometers to?... and how would i go about doing so?... ((i am guessing that i would need a voltmeter of sorts))... if you can, please let me know... thanks...


[Modified by 1.8T_EG, 5:47 PM 10/1/2002]

 

It is amazing, I wish I'd thought of it but it's really just a budget AFC hack.

For some reason I thought the ECU went into open loop at 50% throttle, I could be wrong. I think it would be pretty easy to add a comparator or something like that to the circuit so that at a predetermined MAP voltage you force the ECU into open loop by maxing out the TPS signal wire.

I don't think o2 sensors can really respond fast enough to provide fueling to prevent detonation. That's the whole point of open loop. In other words you might achieve your target lambda but after the damage is done.

 

Yes you definitely need a voltmeter/ohmmeter. You also need to set up a battery pack or a voltage regulator to supply you with 5 volts for bench testing it. I posted values for the pots on the website. You don't necessarily need to set the pots exactly to where I set them it's just a good starting point. Then you can bench tune the circuit output.

 

... the only issue with going open loop so early is that you then rely on the maps in the ecu... this could be a good thing or a bad thing depending on the reliability of the maps that you have... just something else to think about...

 

where exactly do you install this, is it run in line on just one injector?

 

It's installed on the MAP sensor signal wire.

 

wow! this stuff is crazy! filetofit is a sav!!!