Choosing injectors for batch fire MPI.

[EagleMark]

It was just a theory, I have no information or engineering knowledge on it.

It would keep valve cooler, but that is not an issue on intakes... it's so close to intake valve or on intake valve, I don't think it would be worth the effort? It's all getting sucked in so fast it hardly has a chance to settle. DIS would probably be a better improvement!

Easy way to tell is look at newer and newer cars and see if detroit and others started pointing injectors at intake valve more?

Now read up on direct injection! Not that we could convert an old engine to it. But that is a huge leap in internal combustion engines. No fuel in intake or on valves. Cools combustion chambers which allows leaner mixtures, dual injector shots! Way high pressures! Cool stuff!

Off Topic: Hey you interested in doing a thread on 4l60E tranny improvements VIA PCM?

[EagleMark]

Batch fire would make no difference, seqencail... maybe...

You were right, I typed that backasswards...

I still don't think the effort to build an intake would be worth any if any improvement. Just thinking about it I don't know how you could lay down the injector without it being IN the intake runner? Hence my first thought of why it's not done because of clearence.... but if you put the fuel rail on the outside toward valve cover instead of towards inside towards throttle body? That would give you more room to lay down the injector angle!

[gregs78cam]

[EagleMark]

Hope that was a good

[JeepsAndGuns]

Well I dropped the hammer on a intake. I think its out of stock because it had a expected ship date of 11-2. Pictures once its in my hands

[1project2many]

The TPI Chevy fires the injectors 8 times for every cam revolution. One injector pulse per distributor pulse. It takes a bunch of heat to vaporize that fuel. The intake valve isn't a large piece of metal. It cools quickly and can't draw a substantial amount of heat from the head. Injectors directed at the port floor will spray fuel at the head itself where there's plenty of thermal mass to contribute to vaporization. What's interesting to think about is that as the fuel droplets vaporize and expand, the gas will push O2 back up the runners. So the initial intake charge after the valve opens is extremely rich, followed by an extremely lean shot of intake "air." There has to be a lot of swirl going on during the compression stroke to get this mixture blended a little better.

Intake runner length plays a huge part in determining the rpm where the manifold makes best power. But the TPI's power was limited by runner diameter, not length. The same runner on a 302 CI engine would go to 5k, but on a 383 it was starving around 4k. Now the AirSensors / F.I.R.S.T. TPI manifold, OTOH, did not suffer from the same limitations. Somewhere on the 'web is a page describing a 406 powered Vette making over 400hp using one of these manifolds. Definitely not your stock GM TPI.

As far as converting an engine to direct injection, the latest round of 60 degree GM V6 engines are just that, pfi engines converted to DI. GM designed this system to be installed with as few changes as possible. And from what I've read, it's relatively trouble free. Found a nice post by a GM tech the other day which detailed some changes, but I can't seem to find it now.

JeepsAndGuns, can't wait to see what you've found.

[JeepsAndGuns]

JeepsAndGuns, can't wait to see what you've found.

And here it is! Just got deliveried yesterday.

[EagleMark]

Nice!

[1project2many]

That intake should be a nice improvement over stock. Did you get fual rails, or are you planning to machine them from rail stock? If you look at the pics in the TB thread, that intake was designed for the short Weber Marelli injectors that Edelbrock uses with the pro-flow kits. I had to use spacers and make a few changes to switch to standard height GM Delphi injectors.

I'm not an AMC guy. What's with the dual bolt patterns?

[JeepsAndGuns]

Yes I got the fuel rails too. Thats them in front of it on the bench in the first pic.
I noticed from looking at pictures of the complete kit online and looking at replacement injectors on edelbrocks website that it used those short pico injectors. I figured the o-rings were most likely the same size and I should be able to use standard bosch style injectors with just a little spacer that shouldnt be too hard to make.
I test fit my injectors and they fit just fine. Just gotta cut out some spacers.

The dual bolt pattern on the center holes is so the intake can fit the older heads as well as the newer ones. (old square port, and newer dogleg port heads)