MPI conversion

[Zoskalon]

Hey, I'm pretty much a noob, although a noob that has potential. I converted my 93 Dodge Daytona to MPI, and even though I do have a bit more power, the idle SUCKS. I mean its not horrible, but annoying as hell. I used my stock computer and am "batch firing" my injectors. I'm guessing that the idle would be its old smooth self if I had used a turbo computer, right? If going with a turbo computer would be better, do I NEED to use a Daytona computer or what computer do I need to use, and what exactly will I need to alter in order to hook it up to the rest of the car's electrical crap. Can I just have your input on what I should do or any suggestions you might have will be very much appreciated. Thanks

[turbovanman²]

Hey, I'm pretty much a noob, although a noob that has potential. I converted my 93 Dodge Daytona to MPI, and even though I do have a bit more power, the idle SUCKS. I mean its not horrible, but annoying as hell. I used my stock computer and am "batch firing" my injectors. I'm guessing that the idle would be its old smooth self if I had used a turbo computer, right? If going with a turbo computer would be better, do I NEED to use a Daytona computer or what computer do I need to use, and what exactly will I need to alter in order to hook it up to the rest of the car's electrical crap. Can I just have your input on what I should do or any suggestions you might have will be very much appreciated. Thanks


I am assuming this was a TBI engine? You will need a 93 2.5L turbo SBEC and if memory serves, very hard to find. Whats your idle vacuum, it could be something else causing it, IE vacuum leak etc. What did you use for injectors, reg etc. What is your fuel pressure at?

[j4278h]

why couldn't he use the FFV computer from a 93-94 spirit with the 2.5 mpi?

THere is a jyard by yogurtslinger that has 2 of these spirits with computers still in them.

[Zoskalon]

See, I don't know what's up with the vacuum, because when using the stock crap hosing, it idled at the regular 800RPM, but I replaced all the hosing last weekend, and now it idles sometimes at 1000RPM and sometimes an upwards of 1500RPM, I checked and rechecked the hosing, and I doubt there's a leak. And another little issue I have, I read that I can use the 52MM throttle body off a 3.3L but after doing the whole conversion, I found out that there are like two different 3.3Ls out there, and I have the one with just one vacuum nipple on it, whereas the guy I copied the conversion off has the one off the other 3.3L with the 2 nipples. I connected my throttle to the vacuum, but the guy's diagram shows that the other nipple goes to the gas vapor purge canister. But I connected the line from the canister straight to the vacuum. Is this wise, or what?

[turbovanman²]

why couldn't he use the FFV computer from a 93-94 spirit with the 2.5 mpi?

THere is a jyard by yogurtslinger that has 2 of these spirits with computers still in them.

Didn't think of that but aren't Spirit computers different? I thought Daytona's had a bunch more interior gizmo's that the computer controlled?



See, I don't know what's up with the vacuum, because when using the stock crap hosing, it idled at the regular 800RPM, but I replaced all the hosing last weekend, and now it idles sometimes at 1000RPM and sometimes an upwards of 1500RPM, I checked and rechecked the hosing, and I doubt there's a leak. And another little issue I have, I read that I can use the 52MM throttle body off a 3.3L but after doing the whole conversion, I found out that there are like two different 3.3Ls out there, and I have the one with just one vacuum nipple on it, whereas the guy I copied the conversion off has the one off the other 3.3L with the 2 nipples. I connected my throttle to the vacuum, but the guy's diagram shows that the other nipple goes to the gas vapor purge canister. But I connected the line from the canister straight to the vacuum. Is this wise, or what?

That link I gave you on the other sight should help alot with the vacuum routing.

I am using one nipple, just tee the two cannister lines together or just use one and plug the other one off. No, you don't want straight vacuum to the cannister, that could be your idle problem.

[Zoskalon]

so make both go to the solenoid from the canister?

[turbovanman²]

so make both go to the solenoid from the canister?

No, theres 2 lines that go to the cannister, block one off and use the other one at the TB.

[Zoskalon]

Sorry, I'm not following you, one line from the cannister goes to the solenoid, right? so do I block off the other line from the cannister or merge it with the one going to the solenoid, or connect it to the throttle body?

[turbovanman²]

Sorry, I'm not following you, one line from the cannister goes to the solenoid, right? so do I block off the other line from the cannister or merge it with the one going to the solenoid, or connect it to the throttle body?

Ok, I'll look at my van tomorrow and figure this out.

[daytnaes_92]

I am pretty sure you copied my conversion. You can just ditch the whole vapor purge setup, that's the way I was running mine. I just added it to the diagram in case you did want to run it. Just cap off the vacuum ports on the throttle body, and you're done. Make sure you leave the vapor line coming from the gas tank to the canister connected.
I eventually converted to a turbo computer. I ran a 1990 VNT computer. The 2.5 ran lean in mid range acceleration, so you would be better off getting a 2.5 computer. You could use any of them from '88 and up. There isn't a whole lot of work involved to convert it. You will lose cruise control, and the automatic door locks. If you have a traveler, it is also not going to work. After I got the turbo computer in, I ended up going turbo, and swapping in the engine from the VNT car. By the time you get to that point it just makes a whole lot more sense to do that. It will run very nicely with the turbo computer and the MPI setup though.
As far as the idle goes with the TBI computer, I was having problems with getting it steady too. The best solution for me was to block of the AIS port in the throttle body, and set the idle manually with the idlae set screw on the throttle body.

[Zoskalon]

DUDE! ITS YOU! I have so much to thank you man! You inspired me to do this whole conversion man! And thanks a lot for the detailed instructions on cardomain on how to do it! Honestly, the first time I saw that page, I thought wtf is this guy doing writing it all out, like who's gonna use it, but man was I ignorant.

I have a few questions though, what is the whole purpose of the cannister, that I can just toss it aside so easily? And how EXACTLY do I block off the idle and where is the idle adjustment screw? Cuz my bro looked at it and said that there's no screw in there. Keep in mind, you said to use a throttle off a 3.3L, but there are TWO 3.3Ls out there, so are there any differences? And you're saying that I can stick any 88+ Daytona 2.5L turbo computer in there? Would there be any wiring to do besides the obvious injector harness?

[MiniMopar]

The canister is an emissions device. IT's job it to collect gas fumes from the tank while the car sits. After the engine is started, the canister will purge and the fumes will get pulled into the TB.

[turbovanman²]

And how EXACTLY do I block off the idle and where is the idle adjustment screw? Cuz my bro looked at it and said that there's no screw in there. Keep in mind, you said to use a throttle off a 3.3L, but there are TWO 3.3Ls out there, so are there any differences? And you're saying that I can stick any 88+ Daytona 2.5L turbo computer in there? Would there be any wiring to do besides the obvious injector harness?

You need to block off the idle motor passage or put the motor plunger in the middle of its stroke or something similiar. There is a screw that adjusts the throttle blade but you will need to remove the tin shield. Just use a sharp awl and pry it out.

[daytnaes_92]

There is a bunch of wiring changes to be made depending on what year turbo computer you use, but none of it is too hard. Mainly just moving pins around in the connectors. I switched computers in a couple of hours. There will be more wiring that has to be added in you go this route. How good are you at reading wiring diagrams?
I blocked my AIS passage with epoxy. I filled the passage on the back side of the throttle body. You need to be able to have the AIS plugged in, otherwise you will get a check engine light. Like Simon said, you have to pry off the cap that covers the adjustment screw. Both throttle bodies should be similar, just slight differences between the two.
I posted the stuff on my cardomain page because I was getting so many questions about how I did the conversion. It was easier than answering a bunch of email about it.
Let me know if you have any other questions!

[Vigo]

Congrats on the mpi swap.

Your idle is probably caused by many things, one of which would be running oversized injectors (assuming you used the turbo ones) for what the computer is expecting. If you dont have an adjustable fpr you will probably always run rich at idle with the tbi computer.


As far the idle motor goes, PLEASE unplug it. why ANYONE still has that thing plugged in on a k-car is beyond me, except people who live in cold climates. The way that motor is run is so infuriating i always unplug it, and on my older cars that doesnt even set a light.

on the 3.3 tb with two ports, one is behind the throttle plate and one is in front, so one will be vacuum all the time and the other one will basically be ambient air most of the time so if you use that one to try and run some kind of vacuum accessory it wont work well.

there is a throttle adjust screw on the tb, but as mentioned, its behind a little freeze-plug looking thing that you need to pop out. also, i believe its a torx, use the right bit to turn it or you're asking for problems.

imo using the 52mm tb on a 1-piece intake is a waste of time, you will find pics on here and other forums of how the neck of the manifold shrinks to a small oval which will restrict the volume of air entering the plenum regardless of how big you make the tb. you may notice some difference, but i would look elsewhere for mods imho.

as for evap system, its purpose is to capture evaporative emissions from the gas tank (ie gasoline fumes) and then let them into the engine at a controlled rate to be burned. ditching the whole system doesnt cost you anything in driveability or performance, but be aware that if you remove everything and just leave the hard lines open in the engine bay, all the highly combustible evaporated gasoline that was going into your charcoal canister will now be released into your engine bay. probly not the safest. i think you would want to block those hard lines and get an older style gas cap with the vent.

i personally have debated doing the mpi thing myself. there is absolutely no doubt that the tbi throttle body and to a lesser degree the manifold are the largest bottlenecks in the system, but to me the 1-piece isnt enough of an improvement to warrant the effort of the conversion. But i happen to already have the parts, so im thinking about lowering my standards out of curiosity.

bigger tb and another modified manifold are next for my car, already runs 17.0 or so and thinking ill drop straight to 16.5 with whatever i do next.

[Zoskalon]

Congrats on the mpi swap.

Your idle is probably caused by many things, one of which would be running oversized injectors (assuming you used the turbo ones) for what the computer is expecting. If you dont have an adjustable fpr you will probably always run rich at idle with the tbi computer.


As far the idle motor goes, PLEASE unplug it. why ANYONE still has that thing plugged in on a k-car is beyond me, except people who live in cold climates. The way that motor is run is so infuriating i always unplug it, and on my older cars that doesnt even set a light.

on the 3.3 tb with two ports, one is behind the throttle plate and one is in front, so one will be vacuum all the time and the other one will basically be ambient air most of the time so if you use that one to try and run some kind of vacuum accessory it wont work well.

there is a throttle adjust screw on the tb, but as mentioned, its behind a little freeze-plug looking thing that you need to pop out. also, i believe its a torx, use the right bit to turn it or you're asking for problems.

imo using the 52mm tb on a 1-piece intake is a waste of time, you will find pics on here and other forums of how the neck of the manifold shrinks to a small oval which will restrict the volume of air entering the plenum regardless of how big you make the tb. you may notice some difference, but i would look elsewhere for mods imho.

as for evap system, its purpose is to capture evaporative emissions from the gas tank (ie gasoline fumes) and then let them into the engine at a controlled rate to be burned. ditching the whole system doesnt cost you anything in driveability or performance, but be aware that if you remove everything and just leave the hard lines open in the engine bay, all the highly combustible evaporated gasoline that was going into your charcoal canister will now be released into your engine bay. probly not the safest. i think you would want to block those hard lines and get an older style gas cap with the vent.

i personally have debated doing the mpi thing myself. there is absolutely no doubt that the tbi throttle body and to a lesser degree the manifold are the largest bottlenecks in the system, but to me the 1-piece isnt enough of an improvement to warrant the effort of the conversion. But i happen to already have the parts, so im thinking about lowering my standards out of curiosity.

bigger tb and another modified manifold are next for my car, already runs 17.0 or so and thinking ill drop straight to 16.5 with whatever i do next.

Well, since I'm using my TBI computer, I'm running (I hope) 14PPH ford 4 cylinder injectors. And yeah, I do feel as if I'm running rich at idle, because I mean, I'm shooting 4 times as much fuel, right? And I looked at adjustable FPR online before, and they're like over $200?? Not gonna spend that.

And I'm sorry, but I am not sure what you mean by unplug the AIS, do I just take the wire plug out, or unscrew the whole AIS? And do I plug THAT hole, or the hole(s) inside the throttle passage? Because I thought that if you plug the holes inside the throtte passage, there'll be NO air entering when idling. If yous can please make it a little more detailed, I'd be very thankful.

And I'm still fuzzy on doing the vapor system. I have 3 ports on my solenoid and 2 on the cannister. What exactly do I do with each of these ports?

And my BIGGEST concern, is passing the emissions test. Are my chances lowered with this conversion? Possible richness is bad, right? And ditching the whole vapor system will lower it too, right?

[daytnaes_92]

You are not injecting 4 times as much fuel. The 14 PPH ones are way smaller than the original. You are injecting about the same amount.
As far as the AIS goes, just block the passage in the throttle body, leave the AIS installed and plugged in. You are correct, no air will be flowing through this passage. You will manually set the idle with the set screw.
As far as emmisions is concerned, if youur state has a visual inspection, there is no way you are going to pass with this setup. If it is a tailpipe only, it should be OK.
The three lines coming off the cannister are as follows: One coming from the tank, that stays as is. One that the vapors are drawn out of-that goes to the nipple on the throttle body that is ported in front of the throttle blade. (The larger nipple) The third runs to the solenoid that controls the whole mess, and then to the other port on the throttle body. All three are shown on the diagram.

[Zoskalon]

You are not injecting 4 times as much fuel. The 14 PPH ones are way smaller than the original. You are injecting about the same amount.
As far as the AIS goes, just block the passage in the throttle body, leave the AIS installed and plugged in. You are correct, no air will be flowing through this passage. You will manually set the idle with the set screw.
As far as emmisions is concerned, if youur state has a visual inspection, there is no way you are going to pass with this setup. If it is a tailpipe only, it should be OK.
The three lines coming off the cannister are as follows: One coming from the tank, that stays as is. One that the vapors are drawn out of-that goes to the nipple on the throttle body that is ported in front of the throttle blade. (The larger nipple) The third runs to the solenoid that controls the whole mess, and then to the other port on the throttle body. All three are shown on the diagram.

ok, but there are 3 nipples on the solenoid, one is connected to the canister (the middle one I believe), and do I keep the top one connected to the vacuum? and what is the third one for? Mine looks as if the plastic tube was pulled off the rubber connecter to the nipple and I have no clue what this is for.

[Vigo]

Well, i dont know exactly what you're talking about, but i know evap systems usually have 3 tubes: 1 from the tank to the canister, one from the canister to the intake, and one vent tube. the purpose of the vent is to allow air to flow into the evap system to replace that which is sucked into the engine. otherwise, opening the purge solenoid would lower the pressure in the system to the point where there wouldnt be any differential and thus any flow. so the vent keeps air flowing through the evap can to 'pick up' the vapors and carry them to the intake.

so i think its the vent. but again, im not looking at a vacuum diagram or anything, could be wrong..