Have any of you guys ever saw this? Do you think its worth getting it looks like a Sequential Fuel injection conversion for TPI.

http://www.bakengineering.com/page5.html

 

Well, from my education and experience and research, he's dead wrong about the correct time to inject. That alone would make me not want to buy it, unless it (the injection phasing) can be modified.

Sequential injection is meant to inject on a closed intake valve.
1) Because the warm valve can help vaporize the fuel
2) The strong exhaust pulse that travels up the intake, just as the valve opens, vaporizes (blasts apart) the fuel even further
3) When injecting on an open valve, the fuel can enter the chamber as larger droplets and make it's way to the cylinder walls. Liquid fuel does NOT burn.
4) There simply isn't enough time to inject all the fuel while the intake valve is open, unless you target <30% max duty cycle (which requires quite oversized injectors, which don't like to inject small enough pulses to idle well).
5) Injecting on an open valve is only OK with the newest air assist injectors. They provide enough atomization to allow not shooting the fuel to the walls first. This lessens the extent of wall wetting (which is a big part why acceleration enrichment is needed - but not the only part), and reduces emissions, otherwise, with our injectors, stick to the old fashioned way.

Sequential does have benefits. Lots of them (but mostly emissions and idle quality, but not much in terms of HP). But with stock injectors, you won't see ANY WOT peak HP improvements because stock injectors require high duty cycles (longer than the intake valve is open OR closed) at high RPMs.

On the technical side, I wonder, does it just double the pulsewidth? If so, it's going to scew the calibration a tad (by one injector turn-on-time). It also has to repeat the pulse 4 times before it recieves the next pulse. I wonder what it does with the TBI ECU's Asynchronous AE fueling.

I would wait on buying something like this until you have the need to run HUGE injectors and still want it to idle easily while using a factory ECU.

 

I contacted this guy via email. The timing of their injector pulse is fixed at 110 degrees and does not vary/advance with engine rpm. IMHO this is a disadvantage compared to a true SPFI system. I would guess that at some (most?) rpms, especially higher ones, you are not any better off than batch firing. And certainly no advantage at WOT when the injectors are near static.

I don't know where he came up with the 110 degrees atdc to start the pulse. At that phasing the majoroity of the fuel will be firing onto the intake valve when it's beginning to close at anything much over 2000 rpm. I didn't ask why it was where is was, just if it was varable.

He said they didn't vary the start of the pulse because it got too computationally complex. I followed up with a suggestion that it would be easier if they considered the pulse to be a delay off of the previous spark, but got a short reply saying that's what they're doing.

FWIW.

 

Any price info BTW?

 

They quoted $379 for it on the gm-ecm mailing list last month.

 

Hello,

On a stock 1991 L98 350 Firebird speed density engine;
Are the fuel injectors fired sequencial, Bank or batch fired ?

What method is used to fire the spark plugs ?
are the Spark plugs sequencial firing one at a time ?
They should because of the distributor.

Let me know please.
Firebirdjim@hotmail.com