bean Posted February 3, 2004 Share Posted February 3, 2004 Hi guys, Is it feasible to use the 86 electronics in the 87 to get rid of the dreaded MAF system in the 87 body - or is it too much trouble for what it's worth? My plan is to run 12 - 14 psi. A piece of cake inthe 86 - not so much in the 87. Is it worth swapping - or is it more trouble than it's worth? Thanks... Quote Link to comment Share on other sites More sharing options...
WJM Posted February 3, 2004 Share Posted February 3, 2004 take a look at the air flow meters. the flapper is incredibly restrctive at high performance levels. Keep with the MAF. There are ways around the boost cut. MegaSquirt......and other methods. (i dont know of any more actually) Quote Link to comment Share on other sites More sharing options...
bean Posted February 3, 2004 Author Share Posted February 3, 2004 MS is definitely an option I've been considering - so I think I will just go the easy route and leave the MAF in instead of the vane type. It's way easier to do too! Peak boost with MAF is what? 9 psi? Or can it be higher? Rabin Quote Link to comment Share on other sites More sharing options...
Subarutex Posted February 3, 2004 Share Posted February 3, 2004 bean... i picked up an HKS fuel cut defencer. I'm going to give that a go. Its basically just a voltage clamp that clamps at a certain amount. You set it right before the fuel cut voltage, and your set. Now, on my car, i run and SAFC (made by apexi) that modifies the MAF voltage so I can control (to a crude degree) the amount of fuel the car injects. So, i questioned the function of the HKS FCD. I wasn't certain if it would work, since i'm already modifing the MAF signal. After some email with Skip, we decided it would work best to have the FCD (voltage clamp) between the SAFC and the stock ecu. The ecu will cut the fuel if it sees a certain maf voltage for a preset time no matter what we do. Its right before the fuel cut that we get the most fuel out of our cars. The most we can do, is prevent the fuel cut from happening (with a voltage clamp) so we can drive through it and hope our gauges don't lie. We can then use a voltage modifier (like the apexi SAFC, and similar products) to control the ecu to inject fuel when we want it (up to the fuel cut amount). Quote Link to comment Share on other sites More sharing options...
bean Posted February 3, 2004 Author Share Posted February 3, 2004 So what is peak boost the MAF ECU allows? Does it vary according to conditions? Does the boost signal have anything what-so-ever with the fuel cut or is it entirely MAF? I've tricked the 92' Turbo Legacy ECU and have seen 17 psi with no cut - strange they had the algorithm in the EA82T and not in the EJ22T... I'm kinda looking forward to manipulating this system though... Ideally I would not spend anything on doing the mods (up to $50?) If it needs electronic intervention - I'd go MegaSquirt'n EDIS. My current project is the 90' Legacy I just bought - so once that replaces the GL-10 as the dailer driver, I can then work on doing the swap with no time constraints to do it right. I'll get the car running really nice stock, then after the wife decides which one she wants - that will be the car that gets modified. My plan is to stack the cards against the Legacy - I WANT the GL-10 Turbo 5sp hi/lo!!! I can have fun inthe Legacy too though... Rabin Quote Link to comment Share on other sites More sharing options...
bean Posted February 3, 2004 Author Share Posted February 3, 2004 Is the FCD just a voltage regulator then? If so, a simple circuit should be able to allow a certain voltage through then limit it after a certain point... Has anyone found which wires need to be intercepted and what voltage fuel cut occurs at? Quote Link to comment Share on other sites More sharing options...
Subarutex Posted February 3, 2004 Share Posted February 3, 2004 As I believe... the fuel cut is only determined by the amount of air coming into the engine. So it is determined by just the MAF signal. After looking at the wiring diagrams... The ECU never know's what the manifold pressure of the engine is, because our cars have no MAP sensor. So, as the ECU see's an increase in airflow from the MAF, it increases the amount of fuel injected. It does this by taking the MAF signal voltage, the rpm signal and placing it against a premade database. So it takes the 2 inputs, sets it against the table of values... from that table it gets the amount of fuel to inject. Modern FI systems usually use both a MAF (mass air flow) and MAP (manifold air pressure) So, i guess there is no peak boost the ecu can take... there is a peak amount of air the ecu can take. The FCD is a voltage clamp circuit. It will let the signal pass unmodified until it hits the set voltage. If the input voltage is that, or higher... it will output the set voltage. For example... our FCD is set at 2.4 volts: MAF Voltage - What ECU see's 2.3v - 2.3v 2.4v - 2.4v 2.6v - 2.4v 3.0v - 2.4v 2.0v - 2.0v I hope this makes sense... There are cheaper alternatives to make an FCD. Here is a link to a site that has instructions to make your own: DIY FCD I bought all the necassary components to make this. I started assembling it, but partially through, via email with Skip, we discovered that this device requires a 5v reference signal. I got stumped, and happened upon a very good deal with the HKS FCD, so I got it. Skip was goign to work some of his elctromojo and get one of these to work... This reminds me I need to send my parts off to him... Hope this was informative. Quote Link to comment Share on other sites More sharing options...
bean Posted February 4, 2004 Author Share Posted February 4, 2004 Thanks Subarutex! Awesome info - now more questions... The 86 Turbo relied on the boost switch to also trigger a full rich signal from the ECU - thus the crappy mileage. Is the 87 MAF system better on gas - or does it also have a boost rich switch with the FC as an extra protection? If the 87 doesn't go full rich at 5 psi boost, does than mean mileage is significantly better than the air vane type? (I currently get about 20 - 23 mpg) The more I think about getting max power safely - the more I'm leaning towards MS'n EDIS. I think my plan will be to run the car stock with as much boost as the MAF will allow - I'll then save my pennies for an MS system then start playing with that. Thanks! Quote Link to comment Share on other sites More sharing options...
bean Posted February 4, 2004 Author Share Posted February 4, 2004 If there is interest in doing MS for the EA82T - I'm in! It would be so much easier building MS for the first time with someone who is experienced, and building one for their EA82T too. Also good to share maps and set ups - we could develop it quite a bit with a few members working on it at the same time. Would fuel control be it, or would anyone want to do spark as well? I like the idea of doing spark - but I guess that can done done later... I'll be watching to see if this takes off - hopefully not for the next few weeks though Rabin Quote Link to comment Share on other sites More sharing options...
Subarutex Posted February 4, 2004 Share Posted February 4, 2004 The only boost switch on the 87+ that I know of is the one that turns that little dash light on. Even so, the fuel mileage will still go down. More boost = More air which means more gas is injected. The SAFC i bought used for $125, the FCD I got for $80, had been purchased, but never installed. Shhh... but i'm currently inbetween motors. Cracked heater hose -> overheat -> no more head gasket, cracked heads But, i was running 13psi intercooled. Stock turbo, stock block, stock heads. I'm definately into the MS thing. Ignition isn't a huge deal with me... so just a barebones one would be best. Let me know when we want to get going on this... Something that HAS to be done for these engines to come to their full potential. Quote Link to comment Share on other sites More sharing options...
WJM Posted February 4, 2004 Share Posted February 4, 2004 Count me in too! Quote Link to comment Share on other sites More sharing options...
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