[Gmecm] Project underway...

Wed Sep 5 04:29:41 UTC 2007

Hi David,

With only 100 hp, those injectors may be too big for that engine... you'd 
have to look up the flowrate and check it with a HP calculator and see how 
close they are. I know there was a lower flow version for the 2.8L.

Yea, you might run into some difficulties with lean spot on throttle bumping 
due to that large plenum. I have a 95 truck I upped the compression on when 
I was experimenting with some combustion enhancements to the heads... I get 
slight knock when I bump the throttle, but goes away quickly. Seems to be 
the time it takes for the fuel to get from the TBI to the cylinders... most 
noticible at low rpms and a for the most part just as you get in the 
throttle a bit. Either that or my combustion mods arent working... lol

The MS I bought was a couple years ago, just a fuel controller, so the HEI 
dist still runs the spark. The new version now has a lot of good features 
like spark control, IAC hardware for the GM type and bigger fuel tables. I 
need to get one, just too many other projects. The nce thing is that once 
you have the MS, any tuning sotware is free (all posted on the web) and even 
the source code is all open source, so if you want to get in and mess with 
the microcode, you can go ahead. Pretty much any parameter you can adjust 
and set. The hard part is probably putting together hardware and getting it 
all wired up. Most common hardware works, but I know there are some 
specifics with the distributors and a crank trigger for it. The downside is 
there is no diagnostic stream.. you do have a data stream of all sensors and 
settings, but if soemthing goes away, there is no limp home mode... Although 
after I put mine on, I did drive 1200 miles to a MS get together, so the 
durability is there... I'd have to pick up one of the V3 MS's to see how 
they map the ignition though... Overall you cant beat it for the price... 
esp when you look at what they like to get for aftermarket systems... That 
dont work 1/2 as well.

Garrett

>From: "David Allen" <davida1 at hiwaay.net>
>Reply-To: gmecm at diy-efi.org
>To: <gmecm at diy-efi.org>
>Subject: Re: [Gmecm] Project underway...
>Date: Mon, 3 Sep 2007 22:59:29 -0500
>
>  Thanks for the comments!  My friend is doing the fab work on the TB 
>adapter.  He's got a really cool looking "bug catcher" scoop that was 
>hand-made by a friend of his.  The TB will sit as you suggest, with the 
>bores front to back.  It'll feed the front and rear groups of cylinders 
>better that way, plus the scoop will fit over it better. Will have pictures 
>as soon as it is done. We're lacking fuel lines and completion of the TBI 
>adapter plate/scoop holder before starting the engine.  The rest of the car 
>is lacking some of the last electrical details (gauges, exterior lights, 
>etc), cooling fan, and seats.  It'll be a while before it is ready to drive 
>and be real-time tuned; but the engine may run in a few days or so.
>  I'm using the ECM that came with the TBI, I have a 5.0 V8 calibration to 
>start with.  The flahead engine was 80 to 90 HP stock, with a tiny 
>carburetor.  The bottom end is not designed for high RPM use, it only has 3 
>main bearings.  It will not see over 5000 RPM; if that. The top end 
>injector flow should not be a problem, but filling that cavernous manifold 
>plenum with a proper A/F mixture when the throttle is bumped open, scares 
>me!
>  I have heard nothing but good success stories with Megasquirt EFI, but 
>I've never used it.  For some reason I like the GM computers.  The fully 
>mappable ignition timing and fuel tables; and low cost were my deciding 
>factor. I've got 4 GM engines of my own (plus several outside projects) and 
>the same tuning hardware works on all.
>  How much tunability is in the Megasquirt ECU? How is the ignition mapped?
>  Later,
>David
>
>----- Original Message ----- From: "Garrett Herning" <herningg at hotmail.com>
>To: <gmecm at diy-efi.org>
>Sent: Monday, September 03, 2007 6:02 PM
>Subject: RE: [Gmecm] Project underway...
>
>
>>Hi David,
>>
>>I think the injectors would be about the right size. Unless you are trying 
>>to push some large horsepower out of that flathead with a hugh compression 
>>increase and a turbo or blower...
>>
>>I put a TBI from a 4.3L on a 78 pickup I have with a 5.7L. Since its for 
>>the most part a stock engine (8:1 compression or whatever 1978's best 
>>was), and its not a real hp monster I thought they would work ok. It runs 
>>fine and I haven't had any trouble with it bogging down. I used a 
>>MegaSquirt, and if I crank up the high throttle end of the fuel table, it 
>>moves pretty good (along with the gas gage..lol).
>>
>>I think the biggest decision would be how to orient the TBI. The stock 
>>manifold seperate each bore to feed 1/2 of the cylinders... a V8 would 
>>feed 4 with one and the other 4 with the other, 2 on each side. Since you 
>>have a totaly different manifold you'll have to see the best way to feed 
>>them. On my 78, I made an adpater for a normal Qjet type manifold and so 
>>there was a plenum area under the TBI where they could mix. The only thing 
>>I see on your pic is it appears that the runners go down toward the front 
>>and back, so having it sit 90 deg from normal might work better on that 
>>manifold... maybe even some kind of divider that helps direct the flow of 
>>air and fuel from each bore down to the front or back.... just a 
>>thought... I'd not an expert of intake design though.
>>
>>Good luck, looks like a cool project!
>>
>>Garrett
>>
>>
>>>From: "David Allen" <davida1 at hiwaay.net>
>>>Reply-To: gmecm at diy-efi.org
>>>To: "GM-ECM" <gmecm at diy-efi.org>, <diy_efi at diy-efi.org>
>>>Subject: [Gmecm] Project underway...
>>>Date: Sat, 1 Sep 2007 12:45:15 -0500
>>>
>>>  I'm working on a project with a friend, converting a 1940's Ford 255CID 
>>>flathead V8 from carb and points to a TBI/ 1227747 setup.  The 
>>>electronics hardware side is done.  The engine has an afermarket 
>>>distributor with a conventional VR pickup coil.  This is connected to a 
>>>standard HEI module that is firing an MSD box. In the pictures the 
>>>advance weights are still present, but they have been removed and the 
>>>advance bolted so the ECM can control the timing.
>>>  Here's where I want you guys' thoughts.  The intake manifold has a huge 
>>>plenum, look at pictures linked at bottom. We're using a 4.3V6 throttle 
>>>body and injectors.  Do you think the injectors flow enough for accel 
>>>enrich to keep from bogging when you open it?  It is a very mismatched 
>>>setup on the engine/ cam/ manifold but this is what we have to work with.
>>>  We'll be using Cats RT Tuner and a wideband to adjust the VE tables. 
>>>This has been a fun project so far, but the real fun will be making it 
>>>run correctly. It will be an open-loop calibration, tuned for drivability 
>>>first, power second.  Any thoughts?
>>>Thanks in advance,
>>>David
>>>
>>>
>>>
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>>
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>
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