OK, so I'm futzing with my dual Webers, but I'm convinced that someday I'll switch over to fuel injection. I'm a total newbie on this, but there are a few initial questions/feedback I'd like.

I really want to use an offy dual intake, like I have now. What throttle bodies would be appropriate for a 225 slant to get the correct CFM's, considering I'll have two? I have a slightly built engine, larger valves, good flowing head, dynamic compression ratio is 8:1. I use Dutra Duals.

I see that folks often drill for the injectors but epoxy the bungs in rather than welding them in, why is that? Aren't there bungs that screw in, i.e. can't one drill and tap the intake for the injectors? Again, I'm a newbie, be patient with me.

I'd like to start collecting parts for this project. Are there injectors, bungs, rails that are good place to start? Megasquirt comes up a lot, is that a good platform to use? Any specifics? I can do some machining, just need some quidance. Lot's of good projects on the boards, looks like a fun, long term project for me.

brian

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Brian-

Take this with a grain of salt because my slant six fuel injection efforts have not prgressed beyond the planning stage, but the system I would go for is the Ford MAF based system.

I like the Ford system because it is a true mass air flow and sequentially fired system. In you application there woul be the added benefit of simplifying a dual throttle body installation. Have the air intake tract go through the MAF sensor and then split to feed the throttle bodies. You wuld only need to run one TPS sensor and you could split the IAC control signal (but that might be problematic). A single throttle body would be MUCH easier, especially since the Ford system uses a throttle body intended for a 300CI +engine.

The Ford system is a fully stand alone system that has great aftermarket support through devices like the Tweecer or the Quarterhgorse with various software package that let you have complete control over all aspects of tuning. I like the Ford system because it controls the fuel injection and timing and emissions components all in one system. And you have full control over it all.

I am partial to the Tweecer since I have two of them and have been using one on my 89 Ford van since 2010 when I converted it from a MAP based batch fired injection system to MAF based sequential MPFI. My engine is so close to stock right now that I can run the stock tune, but I know I could be runnign a bit stronger if I spent the time to tune the engine. Another benefit of the Ford system is it can be scrounged fairly cheaply form junkyard parts. And it uses all the modern emissions systems, so you can run the motor cleaner than ever with properly modern control of air injection and EGR.

Megasquirt now makes an MPFI system, so that might be worth looking into. http://www.diyautotune.com/tech_article ... 3-nova.htm

FAST also makes an MPFI system, but it runs over $3k!

Whatever you do, I say skip any TBI systems and go straight to MPFI. TBI was really just a bandaid before MPFI was ready for the public and TBI retains all of the roblems inherent with a wet intake manifold. If you are going through the bother of converting to MPFI, just go all the way and do it right.

I would be tempted to run a pair of throttle body injection units. This would save all the drilling and fabrication of installing 6 injectors and the fuel rail. It would also largely preserve the look you've created with dual carbs. Plenty of Chrysler 2.2s and 2.5s came with TBI and a pair should provide enough fuel and if not the injectors themselves can be swapped.

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Joshua

That is very temptig, especially since it eliminates the machine work.

Either way you go, keep us updated. Carbs are fast becoming obsolete and expensive and hard to find in good condition.

I with Josh here. TBI has its advantages ,,,,especially if you want to keep that manifold and look. Megasquirt can easily handle the 2 throttle bodies and a MAP sensor. TBI has the advantage of lower fuel pressures.

You should be able to use a 7 pin HEI unit to trigger .

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Yeah....Im the one who destroyed this rare, vintage automobile.....

A big part of this is the physical limitations of pointing the injectors so that they spray into the intake ports. The injectors have to lay down at a very shallow angle to avoid just spraying fuel onto the floor of the intake runner. Putting the bungs in at that shallow angle makes welding very challenging. Trying to weld into the tight corners and also not distorting the bung to the point where the injector doesn't fit properly can be very difficult. Drilling and tapping at that angle isn't easy either - especially figuring the large diameter thread that would be needed.

To make the fabrication easier some folks just go ahead and squirt the fuel straight against the floor of the runners and still have acceptable results - but it isn't ideal.

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I see no problem with 2 TB's, either TBI (2 X 2.2L or 2.5L TBs would work well) or MP-EFI with 2 TB's. Definitely nice on the cool factor.

I doubt you will make as much top end power with that manifold as a single Clifford 4V, but maybe that is not what you are after anyway. Low and midrange will be great with the Offy 2X1.

Easiest is to get a Clifford 4V or Aussiespeed with the angled bungs cast in, and then you can drill them (see DadTruck's thread).

Happy building!

Lou

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Home of Slant6-powered fun machines since 1988

Hey guys, I was thinking the same thing with the dual throttle bodies, if it worked well, it seems like it would be way easier. That said, after having devoted so much time and effort into those dual Webers, you can tell that I'm not afraid of a project. Yes, I'm trying to keep the form factor that I have, just do a fuel system transplant. If TBI works nearly as well as MPFI and is easier to do, then I'm all for it, please send links to the 2.2, 2.5 systems you are referring to. If you guys tell me that MPFI would provide way better performance, then I'm not afraid to go there.

Regarding the lower fuel pressure aspect with TBI, would that heat soak still be an issue? Part of the reason I wanted to go with FI is to eliminate any chance of heat soak; I figured a high fuel pressure FI system (with appropriate heat shielding) would eliminate the possibility of that issue, make for a really dependable system.

Yes, I did see the recent post, the intakes with the bung castings are nice for the drilling work. I have a buddy who can do just about anything in that regard, so I'm sure he could do the offy 2 x1. I could foresee him welding similar surfaces onto the offy and then milling them appropriately, or maybe finding/making bungs to weld directly to holes he drilled ahead of time. I'm not a machinist but this seems like something that is, although challenging, pretty doable. He can mill/drill/Tig just about anything. I'm sure it works fine, but epoxy rather than metal just worries me.

Exciting stuff. Reed send me any info/links on the Ford system etc, I'm eager to read and absorb before making a decision.

Brian

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Lou,

It's hard to say what my low end is, as I have 2.76's in the chunk, I'm not doing any drag racing. She's a screamer on the highway though; when I kick it down, it really has strong acceleration. That all said, I rarely get above 4k rpm, so essentially I am working on the low end side of things. Even cruising at 75 mph I'm just above 2k rpm.

Someday I want to install a 6 speed Tremec and 3.55's (3.91's?) in the chunk, best of both worlds...maybe I can actually use that sure grip for a burn out...the only time I chirp the tires now is going around a turn sometimes and when it hits second gear.

Brian

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If you are concerned about heat soak, use a fuel supply system that has a return line to the tank. That way the fuel is always circulating through the linme and will never get hot and will keep the throttle bodies cool. The Ford MAF system ues a fuel return line, although heat soak is never an issue anyway since there is no float bowl or carb to worry about. Just saying.

The Pontiac guy proposed a similar system a few years back. He showed up one day posted some neat stuff and then disappeared.

I believe that has was going to use GM 110 TBI units. They are basically half of the usual GM 220 TBI used on the v8's, and use the same injectors. They are on late '80s GM econo cars. You need to be careful as GM did change them towards the '90s and those are no longer compatible

.

You could use 2 GM 110s and split the harness from a TBI GM truck ....use a 747 ECU. 5 wires (3 hot 2 ground)

That would take all afternoon and cost next to nothing.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

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Yeah....Im the one who destroyed this rare, vintage automobile.....