TPI / 700r4 Questions..

[Crafty]

Is anyone familiar with TPI setups and 700r4 boxes ?

I'm putting together a TPI system for my engine.. what I have is the manifold/runners/plenum from an '86 TA - this is good because the manifold bolts straight on without having to redrill the centre bolt holes.
The setup came with its ECU, but being an '86 its a MAF setup, which I don't want to run ( clutter in the engine bay ) - and the '86 uses a coil in cap dizzy, which gives me space issues.. so I want to convert to speed density system - I picked up the small cap HEI dizzy from ebay and am now looking for the ECM..
I decided to change the trans to a 700r4 (yea, I'll probably regret that at some point!).. it came out of an 88 3rd gen. I've already changed the filter in it and the old fluid looked ok so fingers crossed..
Now, cos the trans is an 88 is has a 2000 pulse per mile VSS sensor in it, but the speed density cars used a later 4000 pusle per mile sensor, so I need to convert over to that.. I see the sensor ok US Ebay for $30 or so, but I presume I need to change the gear in the tailshaft to suit ? Does anyone have some pics of what I need or know where I can get the parts to convert ?

I have read on a 3rd gen forum that you can run the 2k sensor with the speed density ECM by doing a little repinning and changing the bin file in the prom.. anyone know if this is successful ?

TIA.

[WZ JUNK]

I used an electronic device from Dakota Digitial to change the pulses per mile.  Theirs is a little pricey but there might be others.  If you just want to control the injection and not the timing you might take a look at Mega Squirt  http://www.bgsoflex.com/megasquirt.html

[enjenjo]

I have done a couple conversions from MAF to MAP. It's not difficult. You will need an 89 and up computer wiring harness, since the computer plugs on you current ECM are not compatible with the right computer. All you need is the part that connects to the computer to get the plugs.You are going to need a computer pn 1227730, or 16198262. They are relatively common, and were used in Oz too. With this setup, and the small body HEI, you do not need the external ESC module either. The Map sensor will be pn 16137039 Most of the other parts, relays and so forth will work. There are seveal places on the web that you can find pin outs to wire this.

On the VSS, output, GM used a module called a VSSB or vehicle speed sensor buffer, that has multiple outputs, one of which converts to the 4000 ppm you need for the computer There is info for this on the web too.

I don't like splices, so I generally install new terminals on the wire for the new connections. If you have to splice wires, make sure you have a good connection, soldered, or crimped, and use a high quality shrink tube to seal out any moisture

[Crafty]

Thanks for the info guys.

I was originally going to go with megasquirt, but I'm keen to use the convertor lockup and having to build an ECM just adds time and another thing I can get wrong !

I'm already on the lookout for a 730 ECM. The biggest problem I have is finding a memcal - all the ECMs on ebay are sold without it and they don't often come up (although there are a few on there at the moment). I don't have any loom at all at the moment.
Right now I'm looking at two options - collect all the parts seperately (ECM, memcal, map sensor etc ) and build a loom ( quite happy doing this because as you say new connections are better than re-jigging old ones ) or to buy a kit from a guy on ebay ( he runs www.chevythunder.com ) which includes a loom, ecm, memcal and all sensors, relays etc. His "buy it now" is about $370, which isn't bad for all that stuff.

I don't have the speed buffer but I knew about it - what I don't know is if the 4k output on this a sine wave ? ( according to that chevythunder site the later VSS sensor puts out a sinewave, so I guess thats what the ECM needs ). I did find the dakota digital box but I had the impression this was only to drive their gauges ? or will its output be suitable for the ecm too ?