MG Midget - 1973, 1275 A Series engine.

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simonbos
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MG Midget - 1973, 1275 A Series engine.

Post by simonbos » Sat Jul 22, 2006 3:01 pm

Name: Simon Bosworth
Vehicle: 1973 MG Midget
Engine: 1275cc
Injection: Two gsxr600 TBs on a DCOE manifold. Two 22.5lb injectors
Description: MSII v2.36, V3.0 board, LC-1 wideband, fuel only at present
Website: http://www.sandlbosworth.com/jsp/midget ... t_EFIl.htm

The gsxr600 TBs are a bit large for this engine. I added a 1.25" restrictor plate
over each bore and that helps a little. The VE map looks rather weird; everything is rather
compressed at the top. I am using TpsAccel only and that seems to work ok.
The engine already runs much better from a cold start than it did with carbs (not difficult!).
I was unable to get a reliable idle with a MSII v1 processor, but after switching to the V2
I now have a nice idle.

Thanks to all the manual writers, it wouldn't have been possible without their efforts.

remkovandongen
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Re: MG Midget - 1973, 1275 A Series engine.

Post by remkovandongen » Sun Jan 04, 2009 4:07 am

Very nice!!
I'm going to convert my supercharged 1275 a+ engine to MS and I'd like to do it the way you did. Can you please post some pictures? Do you have any problems with the siamese head?
Regards,
Remko
Supercharged Mini Van
www.miniasfaltvreters.nl

simonbos
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Re: MG Midget - 1973, 1275 A Series engine.

Post by simonbos » Sun May 10, 2009 6:01 am

Remko,
sorry I haven't looked at this thread for a long time. I just (yesterday) finished up a completely home-made throttle body assembly for the Midget. The previous attempts used a) The GSXR 600 ITBs and b) A single TB from a 1991 Ford Escort. Both of these suffered from having a bore that was too large, leading to tuning problems particularly at large throttle openings. The 37.5mm intake runners were too large as well. Since I coudn't find 31mm TBs I decided to make my own. That took me many months (I put it aside for quite a while). The hardest part was working out where to put the TPS, IAC and 4 injectors on two TBs. I am using 4 19lb injectors (which are as common as dirt in the USA). The performance is lighyears ahead of what it used to be with the other setups. It appears air velocity is important to an A-series engine ;-). I will try and get a couple of pics later today.

Cheers,
Simon

rogerntanner
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Re: MG Midget - 1973, 1275 A Series engine.

Post by rogerntanner » Fri May 29, 2009 9:06 am

Siamese port solution:
I am building (very slowly) a throttle body injection set up for a 1.8 L MGB. The first car I will install it on is a 1977 which originally had a single Z/S carburetor.

I selected a throttle body made to look like a 1930's vintage Stromberg 97 carburetor. (see enclosure). It has two throttle bores and the "float bowl" is actually a fuel rail with inlet and outlet fuel ports (one side shown on enclosure), with two Bosch type injectors inside the float bowl enclosure. These were made to be used in threes on top of 350 c.i. Chevy V-8s, so my quick logic is that it should work on on the 1.8 L (110 c.i.) MGB. The drawing in the enclosure includes a photo of the throttle body.

The manifold is a simple log manifold with two intake runners. The MGB engine compartment has room for quite long intake runners. These look large; but they are the same ID as the available aftermarket aluminum large port manifold.

The end result is months away from completion....I live in CA fire country....and I have a lot of area (acres) to clear in case a fire comes our way.

Roger Tanner
Lompoc, CA

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