Inliners International Forums General Discussion Blown and Injected Frustrated in Fort Worth...

I'm in the process of attempting to build a turbo 292 with a MegaSquirt EFI, and am at a point where a re-thiink of my design assumptions is warranted.

I've spent the last several months attempting to fabricate an intake manifold, and have just thrown the fourth one away when pressure testing revealed that it is one giant leak.

Here are the assumptions that have driven me to the point of drooling idiocy:

1. That because an intercooler is planned, draw-through is not a viable option.

2. That because the rebuilt 292 I'm using is equipped with the heavy stock-type pistons, it will have zero tolerance for running lean under boost.

3. That I should concentrate on a TBI system rather than port injection due to charge robbing, especially when under boost.

4. That because of the relatively long intake manifold, multiple throttle bodies would equalize flow paths and reduce any tendency for poor mixture distribution.

5. That although dual-quad intakes are available which could mount a pair of TBI, the requirements for multiple 90 degree airflow turns make these manifolds relatively inefficient.

6. That in order to minimize the number of airflow directional changes, I should base the intake design on side-draft throttle bodies.

Based on the above assumptions, I've purchased a set of four motorcycle individual throttle bodies of 46 mm bore. They conveniently split into two pair; I had considered buying another set so I could use three pair, but figured I was at the point of diminishing returns.

The manifold I designed is a side draft configuration with two pairs of TB spread far enough to slightly bias for the outer ports since the center is fed from two sources, and is bent up at a 45 degree angle to space the manifold farther away from the turbo and exhaust manifold. I had planned to equip each TB with two injectors; one upstream of the throttle plate like the usual GM tbi, and one downstream for supplemental fuel during high-flow periods.

I've learned that when one is but a rank neophyte at welding aluminum, that complex projects are contraindicated. The manifold could probably be saved by a pro, but the cost would exceed the price of a purchased manifold.

I expect that the simplest and most cost-effective path forward would be to slap a pair of GM tbi on a dual-quad intake and call it done. This would likely perform only adequately, and would not be at all unique.

I could re-fabricate the intake and have a pro weld it, but it would be likely too costly for my meager purse. I could re-fabricate the intake out of steel or stainless, materials that I cold handle somewhat more competently. This would be unique, but would the (putative) performance increase justify the trouble?

I could also fabricate three individual port runners, each mounting a tbi, linked by cross-over tubes. These would likely be simple enough that even I could handle the fabrication. And, if the runner bent up at an angle like the existing design, the tbi could mount at that angle for a pseudo side draft configuration, which would seem to be relatively efficient.

Obviously, there are countless other possibilities such as port injection, those non-electronic fuel mixers, what ever they're called, and so on. Before my wife has to go through my garage and remove all sharp objects, a bit of a reality check would be a help.

First, I don't think that dual tbi's are going to be as bad as you think as far as mixture distribution.

If you want to build a cheap simple multiple throttle body setup, my 2cents is get 3 stock 5.0 mustang throttle bottles. You can cutout 3 t/b flanges, 3 intake port flanges, and use 6 pieces of cee channel, weld it all together, then voila you're done. You could probably build it out of sheet metal which would be easier to work with IMO. You can also use epoxy to seal leaks in welds (I am a sucky welder).

Have you checked out the MSextra code for siamised port injection? I'm going to give it a try what the heck. Theres some interesting web sites on injecting into siamised ports. They've been dealing with it in the uk for a while and seemed to be getting a handle on it. I'll be using an add on board to my MSII which has extra injector drivers and ignition drivers to time the injection for each cylinder. Should be fun. Good luck.

56er...

The Mustang TBs are throttle bodies only, if I remember correctly; that would be fine if I was planning port injection. I also agree re the channel; there are simpler ways of construction, but I wanted to maintain the 10 degree taper that is supposedly mandatory for performance.

Harry...

I am aware of the MSextra code for siamese port injection, but was skipping over that due to the requirement for a crank position sensor. Easily done if one has access to a machine shop; not so easy otherwise. I'd also need the add-on board to handle 6 separate injector circuits.

Now obviously, both of these suggestions would meld together, and maybe that is the best way to go... What I'm trying to get a feel for is the difficulty of these new conundrums. Is the sum of the new challenges outweighed by my existing can of worms?

I've never looked at a Mustang TB; if you have a picture, that would be helpful. Because there are several aluminum foundries in the area due to the aerospace industry, it might also be possible to make a wooden pattern and have three runners cast. I may also begin searching for more information re the sequential injection board and software.

Here is another problem I ran into last weekend; the junkyard L6 motor mounts (from a '68 or '69 pickup, which should have been a 250) don't fit the 292. Passenger side mount bolt patter is ~3/8" taller than the pads on the block. I thought all 194 to 292 engine mount adapters were interchangeable.

On the 292, the engine mount is indeed different, and is a dedicated 292 piece. You could fab something, or get the perch and mount from a 292 equipped truck. I'm ditching the 8 in my 64 GMC and had to get a 292-only mount setup. It'd be fine if it was a 194 thru 250 ci, but... There is provision on the frame in the way of predrilled holes for the 292 mount-it sits further forward as well.

I had to fab my passenger side mount as well. Someone offered to sell me one for 180 and my fab job looked much better to me after that.

Doug, I wouldn't get too worried about the 10deg - while its a great tool for "packing" an intake port when ram tuning, ram tuning doesn't really work on our engines so I wouldn't really lose sleep over it.

I had rather desired to fabricate the drivers side motor mount just to make more room around the turbo and oil drain, but was hoping to have factory mounts so that the engine would be properly located and leveled. Because the truck is completely disassembled, it means replacing the cab to determine clearances. Oh well.

I've been talking to a foundry in FW to see what it would take to build tooling to cast individual runners; a long shot at best. From a cost, practicality, and tunability standpoint, the pair of TBIs on a dual quad manifold is probably best; just not real exciting...

Sorry for the whining; just going through a period where everything I touch turns to crap. Even the tools are breaking.

You should visit http://www.mighty6.com. Then contact Steven Staff at
stevenm6m@suddenlink.net. He runs a quick 292 at over 700hp. He's
a member of the Texas/Gulf Coast Chapter, living in Victoria, Tx.
His brother has fabed most all of the Intake and Exhaust system.

Steve is not running a stock head so he does not have issues with port injection.

If you choose to add a crank position sensor (can be a 36-1 timing ring from a Ford Escort) the as others have mentioned then the solutions are much easier. In my books much easier to mount the crank ring/sensor than try and get boost referenced fuel regulation into a TBI which has internal fuel regulators.

One upside of going crank trigger with the EDIS-6 is its a near bullet proof ignition. Easy to hook up to the MS for timing control.

Also available now is the MS3 which is sequential injection - this allow individual cylinder fuel trim. Mind you it is another level of complexity to deal with.

EFI...

I've read somewhere (and of course can't find it again) that indicated that the stock TBI fuel regulator is vented to the air horn, so that it is referenced upstream of the throttle blade. I seem to remember reading that it was relatively easy to drill that vent path into the downstream side and to plug the upstream opening. The alternative is of course, to remove the internal FPRs and use and external unit, which is probably better anyway.

I would like your take on the notion of using the 4 motorcycle ITBs and two stage injection... Overly complex for little benefit? (Note: if anyone is a better aluminum welder than I, and would like to attempt to play with the concept, I'll donate the manifold for re-welding along with the ITB set up...)

Also; am I giving up on batch-fire port injection too easily? I don't expect vast horsepower; maybe 400 at the best. Is this in a range where I'll have serious issues with charge-robbing? If my assumption that TBI is safer is correct, do you know of any throttle body injection hardware that would be a better choice?

(I'm sorry to be asking so many questions, but seldom get the opportunity to talk to anyone as knowledgeable...)

I've discovered that I can have castings made for ~$150 which mount 3 small GM TBIs on individual port runners. The 3 small TBIs (as used on 2.8s are not sought after and so are dirt cheap) should be about right for my projected output. 2 larger TBIs on a dual quad manifold would also work, I'd think.
If I make a pattern for the single port to generic carb or TBI casting, re-runs of the casting would be easy; might others be interested in such manifolds?

Just for fun, here is a photo of what I've been babbling about:

http://i795.photobucket.com/albums/yy235/dougorcathyevans/8-12-2010002.jpg

Before making patterns, I'd finish what you started and get it on an engine and test. Use an wideband O2 and 6 EGT to monitor the distribution.

3 of these throttle bodies would be a lot simpler to make a manifold for - run a balance tube between them.

Remember that with EFI your not relying on the intake to provide a strong signal to the venturi's so going with more throttle area has minimal impact - which is off idle throttle response it "fast".

I agree, spend some more time to get yours sealed up better and get it running.
The charge robbing really occurs with port injection like mine is. Although when serious power is reached, charge robbing will occur to carb or TBI injection too.

DougE, PM'd ya.

-Stephen

Tom...

The problem is that every time I attempt to reweld to reduce leakage, I wind up making it worse. This is the 4th version of this manifold design I've attempted: I've invested many hours, much new tooling, and enormous study, practice, and effort; all have suffered from the inability to get the welding performed adequately.

Unfortunately, having the imagination and willingness to attempt such a project is no guarantee that one will be able to muster the skills to complete it successfully. I'm afraid that this experiment is circling the bowl.

Can you just seal it with epoxy to get it operational. If it works good then a better version can be made. Tom