I have a question...

[sLoWnStEaDy]

I have been looking into going MPFI on the conquest. I was talking to a buddy the other day and he had an idea that made a little bit of sense, sounded really cheap and easy so I am wandering why it won't work...

Basically, people have used a stock intake and just added fuel injector bungs to the top or bottom of the intake and ran megasquirt. His idea was to keep the primary/secondary along with all the factory wiring and going MPFI. We bounced it around a little bit but I have very little experience in this area.

ANYWHO, idea would be to run a set of 450cc injectors on the top as primaries and a set of 750cc injectors on the bottom for secondaries. He/we were thinking the factory fuel injector connectors just provide a signal to the fuel injector so we could basically just "splice" four fuel injector pig tails together and connect them to the "primary" fuel injector wires. Do the same with the secondaries...


My problem with this "theory" is that it is simple and cheap so I am sure it won't work. Whatcha think?

[sLoWnStEaDy]

here is an example of top/bottom mounted injectors on a stock intake. Doesn't look great but the stock TBI setup has been proven up to 400+ and the MPFI using stock intake has been proven to like 600+...

http://img222.imageshack.us/img222/9211/mpfiintake.png (http://imageshack.us/photo/my-images/222/mpfiintake.png/)

[Drifte]

So theres a factory MPFI on the Starion, but you have the TBI version? The MPFI version I would imagine does not use primaries or secondaries but all 4 matched injectors. How your TBI computer/injector driver would handle the change idk.

[SLVR7]

It would make it a batch fire system then, might as well keep the tbi at that point. You would also need an injector driver box, or it will probably overload your tbi injector driver in the ecu.

[sLoWnStEaDy]

So theres a factory MPFI on the Starion, but you have the TBI version? The MPFI version I would imagine does not use primaries or secondaries but all 4 matched injectors. How your TBI computer/injector driver would handle the change idk.

No, they are all TBI... those are TBI intakes that have been modified for MPFI...

[sLoWnStEaDy]

It would make it a batch fire system then, might as well keep the tbi at that point. You would also need an injector driver box, or it will probably overload your tbi injector driver in the ecu.

I have an Accel Variable Injector Controller.... (#74070) I am sure I will stick with TBI for the time being, this just came up in conversation and I was curious.

[sparkles]

It would make it a batch fire system then, might as well keep the tbi at that point. You would also need an injector driver box, or it will probably overload your tbi injector driver in the ecu.

What he said. Tried to do that with a guy's TBI Camaro. Doesn't work so hot.

[sLoWnStEaDy]

Since when is sequential better than batch? I knew for emissions/idle and such it is better but I always thought batch had a little more power potential, or at least, no less the SFI...? and Sequential pretty much turns into batch at higher RPM's anyways...

I have not really looked into it a lot yet but my "theory" would be as fallows. the VIC has controls for 8 injectors, the Conquest has two injector signals, a primary and a secondary. Simply wire the primary from the stock ECU to one side of the VIC and thus have 4 primary injectors. Then do the same for the secondaries. I am not 100% sure how the VIC works, it is a "driver" or just more of a "distribution center"?

Lastly, I keep seeing the only real "advantage" to Sequential is that you have individual cylinder tuning capabilities that you don't have with batch firing. However, the VIC would allow for that, wouldn't it...?

[SLVR7]

Seq. fires when the intake valve is open. Most oem has the injector angled to spray the fuel directly into the cylinder barely touching the port walls or intake valve. Atomization is the name of the game, liquid fuel does't burn. With batch fire the injector fires multiple times into a stagnent port with a closed valve, fuel pools on the valve waiting for it to open. The vic is a driver it mirrors the ecu pulse width, but is able to handle the load of more and/or different resistance injectors. It won't make it seq., just mirrored batch fire.

[sLoWnStEaDy]

Seq. fires when the intake valve is open. Most oem has the injector angled to spray the fuel directly into the cylinder barely touching the port walls or intake valve. Atomization is the name of the game, liquid fuel does't burn. With batch fire the injector fires multiple times into a stagnent port with a closed valve, fuel pools on the valve waiting for it to open. The vic is a driver it mirrors the ecu pulse width, but is able to handle the load of more and/or different resistance injectors. It won't make it seq., just mirroed batch fire.

true but at a certain RPM is sequential REALLY able to work as it "should"? Sequential works off cam timing I believe, I would think at a certain RPM it would be spraying so much, so quick it would basically be no different than a batch fire setup?

I knew the VIC would keep it batch fire but didn't know if it would mirror the signal or just distribute the signal, Thanks for answering that.

[SLVR7]

I think seq. work as it should even at high rpm. Oem must believe it too, since they are now going to direct seq. fuel injection. Old seq. work off of cam timing, new is off crank timing, since they now have very accurate high tooth count trigger wheels. Usually cam timing is now only used as a redundent cylinder #1 tdc signal.

[sLoWnStEaDy]

I think seq. work as it should even at high rpm. Oem must believe it too, since they are now going to direct seq. fuel injection. Old seq. work off of cam timing, new is off crank timing, since they now have very accurate high tooth count trigger wheels. Usually cam timing is now only used as a redundent cylinder #1 tdc signal.

Well, that makes sense as far as the new sequential goes. I just remember reading some HUGE thing about batch vs seq. years ago in a magazine and they basically said after a certain RPM, they where pretty much the exact same thing. That, of course was on the cam timing seq. setup though. I think 5.0HO's LT1's and 1JZ's are all batch aren't they? They all make pretty damn good power pretty easily.

not trying to start a "vs" discussion as I believe that the crank timing sequential of now is probably far superior to batch. I am just saying i think a batch fired MPFI is going to be better than the TBI setup from the factory. In all honesty, the factory TBI setup is good for a pretty decent amount of power but a simple MPI switch has gained people a fairly decent amount of power in itself. I might just rebuild the TBI, and throw a bigger secondary in there, throw on an 18G/20G and see how long it will last.


As of right now, the tiny 12A makes more power than my current clutch can handle at about 10psi. So, first thing is to get a new clutch, which I will do shortly. then I am going to max out the 12A and go from there.