Slant Six Forum :: My EFI thread

Hi GunPilot.
First of all, I don't know how the TBI unit open it's butterfly valves, is it a two stage with primaries, and mech. or vacuum operated secondaries like a carburetor, or do all open simultaniously?
If it is a two stage setup, I can see from your pictures that you have oriented the setup so that you have primaries/secondaries oriented in a front/rear (or rear/front) position.
It is sometimes a problem with 4-bbl carburetors - and even with 2-bbl with vac. operated secondary - like the Weber 32/36 - that you have richer mixture to the cylinders on one side of the manifold when the carb is mounted that way.
If it is possible to test rig the TBI, so that you can undo it later if not successful, with some extra length hoses and other bits and pieces, try mounting the TBI sideways with the throttle shaft parallel to the cylinder head, with the primaries on the outside. That may cure the uneven fuel distribution between front and rear 3 cylinders.

Olaf.

Author:	Sam Powell [ Sun Aug 22, 2010 7:32 pm ]
Post subject:
That would explain the black plugs. Good work. Yes, Lou has always worked magic sitting in the co-pilot seat of my EFI Dart. Tappity, tap-tap. George, I am guessing Lou has already suggested you need a bigger cam. Sam

Author:	GunPilot [ Sun Aug 22, 2010 8:25 pm ]
Post subject:	The close of the thrash
Well, the race is over so the thrash is over. By Sunday AM we had the car running as well as it can. My best ET came up to 18.95 and that was with me backing out to keep from breaking out (I did anyway). So it has more speed in it. Some more incremental tuning will bring more speed out. I especially want to try some timing changes, but for the most part, that's it for now. I had my doubts for a while on Thursday but it all came together this weekend.

Author:	GunPilot [ Wed Jun 01, 2011 3:26 pm ]
Post subject:
Getting ready for Kearney Reloaded. Some things I have determined in the year (almost) since doing the EFI swap on this: 1. TBI is NOT the way to go if not using some sort of manifold heat, as in my case with the Dutra Duals and the Offy. The fuel just runs straight back into the back three cylinders and fouls the plugs in no time. So I have to warm up the car on old plugs, until the mani is warm, then switch to new. Sucks. I still think TBI would be okay if using a stock manifold setup, like a super six with the manifold heater stove. 2. The way to go is multiport. Simple as that. Lou is right, the dry manifold is best. 3. Controlling spark is a very good thing. I learned a lot about it as I setup the MS II with spark. One thing I learned was the limitations of a distributor system, controlling spark. I can easily see the variations in timing cause by all the tolerances in the system. I'm currently using a locked, stock distributor. 4. The way to go is using a crank pickup and some sort of distributorless system, like EDIS. 5. Variables in the system, such as fouled plugs, can have you chasing tuning for hours and days. Going back to a known point is good. Saving a good tune under another name and having it for recovery is a very good thing. Changing one thing at a time, as Sam Powell said, is very very sound advice. Tuning spark and fuel at the same time is not fun. Doable, not enjoyable. 6. I hate the way I do some things, particularly wiring. It's functional, it works, but man is it ugly. Like my welds. I'm going to run what I brung this weekend at Kearney but the Duster is going to get the multiport and crank trigger. It just has to happen.

Author:	Dart270 [ Wed Jun 01, 2011 9:12 pm ]
Post subject:
I don't necessarily agree with the TBI puddling. I have been running TBI on my '64 Dart for 10 yrs with a big lumpy cam, headers, and no manifold heat. It is a bit cold blooded, but fine for a fast NA street car. Better than a carb. However, your points are all well founded and well taken. I would not bothered with TBI/wet manifold under boost. Thought it would be a nightmare. I can tell you that it has been pretty easy to tune my '68 under boost (in last 36 hrs) with MS-I and port EFI. See you soon! Lou

Author:	GunPilot [ Wed Jun 01, 2011 9:58 pm ]
Post subject:
That just ain't right, Lou. You having boost and not me I mean. Well, I don't know what is going on, but I have a pretty good collection of black spark plugs. The ones in front never foul. Anyway, with that TBI I have, I can plug the injector bosses and use it as a TB for multiport so it's a matter of evolution for me. There was some reason someone glued sticks in that manifold. BTW I already bought some more injectors I can't wait to see that turbo setup you have... Edit: One difference may be in the TBI I have. If I recall you are using a GM TBI right? It has two big injectors in the center. Mine has four spraying in from the sides. Maybe it doesn't atomize as well as the other design. Just a guess.

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My EFI thread https://www.slantsix.org/forum/viewtopic.php?t=41445	Page 3 of 3

Author:	Dart270 [ Thu Jun 02, 2011 6:10 am ]
Post subject:
Yep, could be that TBI is not good design, and perfect to use as TB for port EFI. Lou

Author:	olafla [ Thu Jun 02, 2011 2:01 pm ]
Post subject:
Hi GunPilot. First of all, I don't know how the TBI unit open it's butterfly valves, is it a two stage with primaries, and mech. or vacuum operated secondaries like a carburetor, or do all open simultaniously? If it is a two stage setup, I can see from your pictures that you have oriented the setup so that you have primaries/secondaries oriented in a front/rear (or rear/front) position. It is sometimes a problem with 4-bbl carburetors - and even with 2-bbl with vac. operated secondary - like the Weber 32/36 - that you have richer mixture to the cylinders on one side of the manifold when the carb is mounted that way. If it is possible to test rig the TBI, so that you can undo it later if not successful, with some extra length hoses and other bits and pieces, try mounting the TBI sideways with the throttle shaft parallel to the cylinder head, with the primaries on the outside. That may cure the uneven fuel distribution between front and rear 3 cylinders. Olaf.

Author:	Dart270 [ Thu Jun 02, 2011 8:24 pm ]
Post subject:
I think the problem is that these TBI setups use port EFI injectors firing across the throttle bores, and a bunch of fuel just runs down the sides. Ryan Covalt has one of these things on his Dart and I don't like the look of it. My TBI is an OEM/Holley design with real TBI injectors and was used on millions of vehicles in the 80s and 90s. Just some thoughts... Lou

Author:	olafla [ Thu Jun 02, 2011 8:37 pm ]
Post subject:
Quote: ...port EFI injectors firing across the throttle bores, and a bunch of fuel just runs down the sides. It's probably an unfitting remark in a fuel injection thread, but that is one of the reasons why I love my Autolite/Motorcraft carbs with annular boosters... Olaf.

Author:	Dart270 [ Thu Jun 02, 2011 8:57 pm ]
Post subject:
The TBI injectors make a pattern that is very dispersed over the throttle bore area, like annular boosters. Nice parallel. Lou

Author:	GunPilot [ Tue Jun 07, 2011 6:58 am ]
Post subject:
Quote: Hi GunPilot. First of all, I don't know how the TBI unit open it's butterfly valves, is it a two stage with primaries, and mech. or vacuum operated secondaries like a carburetor, or do all open simultaniously? If it is a two stage setup, I can see from your pictures that you have oriented the setup so that you have primaries/secondaries oriented in a front/rear (or rear/front) position. It is sometimes a problem with 4-bbl carburetors - and even with 2-bbl with vac. operated secondary - like the Weber 32/36 - that you have richer mixture to the cylinders on one side of the manifold when the carb is mounted that way. If it is possible to test rig the TBI, so that you can undo it later if not successful, with some extra length hoses and other bits and pieces, try mounting the TBI sideways with the throttle shaft parallel to the cylinder head, with the primaries on the outside. That may cure the uneven fuel distribution between front and rear 3 cylinders. Olaf. Hi Olaf! No, this TBI has four butterflies that open simultaneously. All the bores are the same size so rotating it won't make a difference as far as primary/secondary. One thing I can do is vary the size of the bores. I have some venturi spacers that slip into the venturis to reduce them. I've tried doing that in various ways but not much effect. With the spacers out, the TB is about 750 CFM. The spacers are about 100CFM so with them all in I'm at about 400 CFM. I ran it with them all in this weekend and had no restriction in TB size according to the datalog. Throttle repsonse is more manageable with them in. Anyway, I think the key is the type and angle of the injectors as Lou says. This setup was designed to replace a carburetor on a V-8 so probably this situation doesn't manifest itself so much in that type of manifold. It's magnified by this long cold manifold and no exhaust heat. This weekend I warmed the car up on the old set of plugs in 4-5-6, changed to new pulgs in those cylinders and then ran it all day with no problems. After a day of running those plugs looked great. I think I'll go to plan B on this setup which is port injection. Actually I had a wild idea driving home from the races...

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