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When most people hear "TBI" they think of the units installed on the F-bodies and trucks of the 90's. Those were certainly capable of 300+ HP when properly equipped. The Metro TBI is another beast altogether.

Truth told, there were a dozen "TBI" units from GM and Chrysler, all similar but differed in intake diameter and injector flow rate. Almost all incorporated idle control and the necessary throttle and load sensors. (GM began to use the MAF in the mid-90's and Chrysler followed suit shortly thereafter. Ford doggedly stuck to the MAP sensor and still does to this day, I believe.

My opinion is that the peak of performance and driveability is achieved through a single air metering mechanism (common throttle body) and individual fuel injectors for each cylinder. (Multi-port fuel injection) This makes the hard part (air control) easy and the easy part (fueling) most effective by putting it as close to the valve as possible.

-Deek

FirstYearDeek wrote:When most people hear "TBI" they think of the units installed on the F-bodies and trucks of the 90's. Those were certainly capable of 300+ HP when properly equipped. The Metro TBI is another beast altogether.

Truth told, there were a dozen "TBI" units from GM and Chrysler, all similar but differed in intake diameter and injector flow rate. Almost all incorporated idle control and the necessary throttle and load sensors. (GM began to use the MAF in the mid-90's and Chrysler followed suit shortly thereafter. Ford doggedly stuck to the MAP sensor and still does to this day, I believe.

My opinion is that the peak of performance and driveability is achieved through a single air metering mechanism (common throttle body) and individual fuel injectors for each cylinder. (Multi-port fuel injection) This makes the hard part (air control) easy and the easy part (fueling) most effective by putting it as close to the valve as possible.

-Deek

yep sequential mpfi is the best no 2ways about it. However, it is the most expensive means. TBI can be done cheaper.

Actually most fuel injection systems on gas burning vehicles do not run sequential injection per se.
However my Dodge Pickup with Cummins Diesel Engine does run sequential injection, and it is all mechanical, no computer control.

It is a 96 model, I even turn the pump on and off with a cable rather than a selinoid.

kb0ou wrote:Actually most fuel injection systems on gas burning vehicles do not run sequential injection per se...

Since about 2000, most manufacturers have used true sequential injection on MPFI motors. This might not mean what you think...

With regards to a gasoline engine, "sequential" just means that injection events are timed within the window of a single cylinder, not a single revolution of the motor. (There's a difference.) It does not mean that ALL the fuel is injected while the valve is open.

Whenever the duty cycle allows it, an individual fuel pulse will start just as the intake valve is opened and end well before the intake valve closes. Due to the flow rate of most injectors, this can only be accomplished at low RPM's (idle) and slow cruise.

Whenever the flow rate cannot support this scheme, the engine is still calculating timing events within the window of the individual cylinder, the injector just can't get all the fuel in in that 1/4 (or less) of a cycle. Most ECU's will begin the injection early and end as the valve closes.

The converse of a sequential scheme is the batch scheme. On an MPFI batch injection motor all the injectors fire at once, usually (but not always) timed to a revolution of the motor, often by signalling off of the coil. That means the injection event starts at that signal and stops when the duty cycle expires. This can cause some issues, as the most recent cylinder to intake prior to the fuel pulse has three cycles to go before that fuel is ingested. In a cold engine at idle, 3 revolutions is an eternity for fuel to sit around and condense.

At wide-open-throttle, sequential motors act very much like batch motors as injection events start to overlap. But then again, no one cares much about emissions or efficiency on an engine at WOT!

-Deek

Very good explanation Deek,
Also a lot of injection system alternate firing of injectors in banks so not all injectors fire at once to lower current draw on the firing circuit etc.
The Microsquirt can be set up to alternate or not.

Yep what Deek said, and I was still talking about the GM 2bbl TBI system when I was referring to the 300hp. You guys got me thinking now. I might have a spare goldwing to mess with soon and I happen to have the entire 2bbl TBI system (wiring, ecu, main unit, sensors etc.) off a 86 2.6L V6... I was looking up pumps at work and it seems a inline fuel pump from a 89 F150 would do nicely for pressure (hell would probably only ever see 1/4 of it's capibility) and only set me back about $60.

seeing my bike will be totally apart this winter, I was going to bench test my theory. If it works as expected, you will get a tutorial and some videos.

I'm very impressed with the cost and level of engineering in this efi conversion kit:
http://www.ecotrons.com/Kawasaki_Ninja_ ... I_kit.html
For $499 you basically get everything needed to convert a 250cc 2 cylinder Kawasaki Ninja, including ecu, harness, twin 28mm throttle bodies, injectors, pump, sensors, tuning software, etc.
The ecu is based on a Freescale s12p micro and (judging by the web page description) much superior to the microsquirt, which is $500 all by itself.
Should be fairly easy to add another throttle body set, larger injectors, and run in modified sequential to work with a 80+ HP 4 cylinder.
Will probably give them a call and see what they think of the idea, hopefully while they're still in business..

nice find, keep us in the loop

The microsquirt is only $380 and has quite a few more features. Not to mention the enormous support from the web forums.

Not arguing, just setting the record straight.

-Deek

You're right right about the price Deek, it's been cut substantially.
I like the Microsquirt concept, but it just doesn't have the capabilities to do what I want.

Which feature are you after? Just curious... The Microsquirt was aimed mostly at the V-twin crowd (that's why it has two seperate ignition clocks) but really, with all the room on our bikes, and being an even-fire monster, a normal MegaSquirt II would fit nicely and give you every feature you're after.

I can't say enough for the support group there. I was once very active and went on a couple of road trips to help guys with their installs and tuning. Tuning is so much easier now with the upgraded MegaTune software; people rarely need help with that anymore!

-Deek

If I only have the 2 throttle bodies, I can use the microsquirt no problem. FWIW I could probably use the ninja set up too.

My current ecu (and the ninja kit) can use MAP sensor to id cyl1 and use it for sync injection. There's also table size and number that's probably more related to use of megatune. May wind up usinging it anyway given reduced price!

I keep looking at the hardley systems, you can buy a box for 380, and it has the harness ready to go and its mapped for bikes. Seems like pretty plug and play if I use dual TBI's for the bike.