My MPI Conversion (w/ pics :D !)

[sgtarky]

yes,batch fire.as I said I will be getting some help from the guy that did the daytona on cardomain. If you look at my cardomain page you can see the shape of the engine, I had to rebuild it. I don't want to turbo it, might pick up a daytona for such a project. I will probably get an adjustable fuel regulator, that should help out with rough idle. As far as power is concerned, you can run turbo cars with out the turbo, they work a hell of alot better on non-turbos because the compression is higher.

[TurboTurismo]

Hmm, didn't consider the compression........I have a friend that is doing his 2.5 tbi up with the mpfi setup and he is using the turbo comp harness and injectors..I am looking forward to this being done and working so I can do it without having the problems first.LOL, guess I am a cheater of sorts by waiting....... On the other side of things, The FFV stuff from a yard car might be the way to go if it could be found

Robb

[sgtarky]

I will eventually use megasquirt tho.

[TurboTurismo]

Yes I have heard of Mega Squirt systems.... Heard some great things about it

[phantomrt]

There was a quote from the dodgegarage.com that when using a turbo computer without an actual turbo, it "takes a dive at WOT". I strongly disagree with that. With the wastegate held wide open on a turbo car, its still a bunch faster than the TBI is... and the turbo has lower compression.

[TurboTurismo]

So possibly the turbo comp and wiring setup without the turbo may work, a wimpy 14 tbi pump wont work tho.Would have to go with the higher 55 psi pump correct.I think the 39psi out of the 90s tbi might work? Maybe the setup could work for a DD....worth a try anyhow

[phantomrt]

It depends on what year... in 1991+ the turbo's / V-6 / TBIs all used the same fuel pump. My '92 Daytona was TBI originally and now boasts ~200 turbocharged horsepower with the TBI pump. They also used the same size clutch. Automatic transmissions probably followed suit with the beefier internals in TBI cars as well.

The turbo computer and wiring WILL work without the actual physical turbocharger there. It will run well and get good mileage.

[ZoskalonMPI]

My only concern, is that even the sequential fired SBECs batch fired all the injectors after 3K RPM. My car ran like crap with 19PPH injectors batch fired, even after 3K, 14PPH worked very well. But with sequential, you'd have to use the 33PPH injectors. So wouldn't THAT run especially badly AFTER 3K RPM? The turbo would make up for the extra fuel, but without a turbo? Or am I wrong and the computer can adjust the fuel to match the air flow via oxygen sensor?

[phantomrt]

The engine computer will add appropriate amounts of fuel based on the manifold pressure, throttle position, engine RPM, etc. If one of these multipliers is not registering high numbers (manifold pressure) it *shouldn't* add excess fuel.

Do they batch fire after 3,000 RPM? Is this fact? I'm not being smarty pants but I always found it a bit strange how my engine suddenly turns on like a switch right at 3000 RPM. It is pretty gutless below that, but it seems so instantaneous when the power comes on. I do know that 3000 RPM seems to be a magical number where at over a certain % throttle, it will suddenly go out of closed loop. At the same time the engine smooths out and goes like hell.

Hmmmmmmm. You got me thinking now. This may help solve some of my drivability issues.

[ZoskalonMPI]

Quote:

Originally Posted by phantomrt The engine computer will add appropriate amounts of fuel based on the manifold pressure, throttle position, engine RPM, etc. If one of these multipliers is not registering high numbers (manifold pressure) it *shouldn't* add excess fuel. Do they batch fire after 3,000 RPM? Is this fact? I'm not being smarty pants but I always found it a bit strange how my engine suddenly turns on like a switch right at 3000 RPM. It is pretty gutless below that, but it seems so instantaneous when the power comes on. I do know that 3000 RPM seems to be a magical number where at over a certain % throttle, it will suddenly go out of closed loop. At the same time the engine smooths out and goes like hell. Hmmmmmmm. You got me thinking now. This may help solve some of my drivability issues.

Didn't you turbo your car though? And I've read that on several places and a couple people have mentioned it, about the batch firing after 3K. So then my question is, why did my car drive like HELL with the 19pph injectors? I would literally half the time have ZERO power, I'd be at lets say 2K rpm, and no matter how little or how much I'd open the throttle, the rpm would not go up at all, at which point, I'd have to drift to the side and put it in neutral and give it a good rev. And the car would die if I pushed the gas pedal down a little hard after a stop, which I'm sure was due to drowning the engine, because I'd have to crank it a couple times before it'd start again. And even now, (or should I say before, now my car's in the garage waiting for the electronics to fix themselves ) I'd have the same problem, where my car would almost shut off if I floored it after a stop, and every time I punch the accelerator while driving, the car would drop a few rpm first and then start pulling ( not downshifting related ). So what the hell? Is it faulty sensors? But I'm just gonna see if I have these problems with my new set up, once I figure it out

[DaytonaTurbo87]

ZoskalonMPI, are you talking about how your car was running like crap running 4 injectors on TBI electronics or have you changed over to a true MPI harness yet?

The turbo computer without a turbo should still run well even at WOT. The map sensor tells the computer there's no boost and it scales the injector pulsewidth and ignition timing curve appropriately. All I know is I drove a daytona identical to mine with a low mileage 87 log intake T1 and a blown head gasket, cylinders drinking coolant, and it still had better throttle response than any TBI I've driven. Sad I know. Run the proper 33# injectors the one-piece intake and matching T1 or T2 computer was designed for and there's no reason it wouldn't run good.

[phantomrt]

I remember back in my TBI days I played around with removing the coolant line that went through the intake manifold--big power gain, but the off-idle hesitation when you gave it some good gas was unbearable when ambient temps were below 50 degrees.

Unless unless you are running VERY VERY rich (you will smell PLENTY of exhaust) when you hit the gas, and the engine stumbles and wants to die, that is a lean condition. This is assuming the ignition system or other things on the car have no issues.

As far as the batch firing thing goes.... it does not sound logical to me. I mean, what purpose would that serve? How would it be better? If it does batch fire, it is probably injectors 1&3 and then 4&2. I can assure that ~3000 RPM under moderate throttle is when it leaves closed loop. But other than that... only noid lights with a good eye watching them would be able to tell.

[ZoskalonMPI]

Quote:

Originally Posted by DaytonaTurbo87 ZoskalonMPI, are you talking about how your car was running like crap running 4 injectors on TBI electronics or have you changed over to a true MPI harness yet?

I was talking about when I had 19pph injectors batch fired. 14 pph injectors batch fired work VERY well, aside from the rough idle.

And just because I'm a noob, what is "closed loop?" And the previous systems (-89) were batch fired IN PAIRS, as far as I've heard. So I guess it would make sense that the batch firing I heard about after 3K is the same as the batch firing all the time before 89. And I mean, would it even make any difference if it was sequencial or batch fired after 3K? at those speeds, the injectors mind as well stay on the whole time lol

(in terms of one cylinder)
3000rpm, fired every other rotation, so 1500 firings per min, thats 25 firings per second at 3k RPM :/ 40 firings per second at 5K RPM. I don't see how precise these injectors really are, and this is ALL speculation and theorization, so don't necessarily believe it.

And wouldn't batch firing allow much more fuel into the engine? 2 injections per cylinder instead of one? to compensate for the turbo kicking in around there? wouldn't it be BETTER to batch fire under boost? I'm asking, tell me :|

[DaytonaTurbo87]

closed loop is normal driving where the computer reads the oxygen sensor signal and adjusts the amount of fuel it injects to attempt to attain 14.7:1 air/fuel ratio. Open loop mode is just the opposite. It happens at WOT and when the engine is started from cold. O2 sensor is ignored and the computer injects the amount of fuel it calculates as being required. The o2 sensor corrects the mix during closed loop, but in open loop it has no say. In ideal conditions the engine runs good in open loop, but if you start messing with stuff that you shouldn't be, as soon as the o2 sensor can't help control the mix, the engine can run like crap.

Yes, 89 and prior systems were fired in pairs. Sequential firing above 3000rpm was deemed not useful cause at those rpms the injectors can't open and close fast enough to usefully control the mix sequentially. But just because it's switched from sequential to batch firing doesn't mean the computer has kicked into open loop mode. Many TD's cruise on the highway at 3000rpm or above and the computer still runs in closed loop mode. Unless I'm mistaken the SBEC only kicks into open loop at a certain % throttle opening or if a certain boost level is hit, along with the usual idle and cold start open loop settings.

It's not BETTER to batch fire at higher rpm's or under higher boost, but it's pointless to try and sequentially fire it. The injectors just can't keep up at those speeds. Plus they would need to stay open longer to deliver the required amount of fuel, it just makes sequential firing not feesable IMO.

[phantomrt]

I guess that the added benefit of sequential injection would diminish at greater RPMs... hence sequential firing is not necessary, but the question is, what would the benefit be to have the computer switch modes? Each intake runner has its own injector, so one injector cannot affect the fuel mixture in another wether it is batch fired or sequentially fired. May as well stay sequential all the way to redline IMO.

Also remember that the engine management doesn't switch to open loop ONLY at full throttle. Easily as low as 50% throttle does it on mine under the proper conditions. In a perfect world, oxygen sensor feedback would be pointless. It is just an input to the engine computer to optimize the injector pulsewidth to achive 14.7:1 air/fuel mix. No two engines combust equally especially after 100,000 miles. Oxygen sensor feedback "fine tunes" it.