3tgteu on Mega squirt?

[thechuckster]

twin post coils are for waste spark not twin sparks - you'll need two coils.

there's advise on msefi and msextra about how to run two VB921 ignition drivers from the one output on the MS 2.1 & boards

gimme a few minutes and i'll confirm what/how you do this.


edit: this bit in the Msextra manual tells you how

[The Witzl]

Chuckie to the rescue.

[thechuckster]

me = teh win?

[3jcelica]

Thanks Guys for the valuable input, I will probable go down this path. I have had a look at DSE, JAYCAR and RS but could not find the VB921, Do you know where this can be sourced?

The Witzl,

I have successfully run my 3tgteu on the 8 pin GM HEI from a camira (one coil only). It didn't like certain coils however so I tried a few and it ran ok with a magan one but would obviously be best with the camira one. I know what you mean by spastic, the engine seems to break down, fire irregullary and not rev past about the point you talk about. I have also run a Delco setup using the vr sensor from a 2tgue on an RS escort with a locked dizzy running delco(camira 8 pin GM HEI) and this work no problems again coil selection helped.

The Chuckster,

You say the double post is for wasted spark, i.e firing on two cylinders and one in compression the other in exhaust or something. Is there an issue on using a twin post if both hit compression at the same time?

I don't belive V6 commodores use wasted spark, however I do think they use twin post coils(3 coils) which would suggest both sparks under compression. I could be wrong though

Thanks

Roger

[The Witzl]

Roger,

no, they run one spark on compression, the other on exhaust.... means one spark is strong and the other weak. If they are both in compression they will probably both be weak, and no one does it this way (obviously for good reason).

YOu can get the VB921 from diyautotune.... or buy it with your MS-2 kit

[3jcelica]

The Witzl,

I have done some more research and confirm what you are saying about the running of two sparks in compression. Look like I might run a single spark, apperntly little difference in performance from what I have read and also experimented with.

After looking further into the V2.2 mods required to get the VR input (sensor circuit) going and the VB921 I can safely say the HEI circuit look the easiest (no VR sensor circuit and minor mods to the board. Since I have had some success with running this module I think I will continue down that path with a single coil. I will let you know how I go (it will be a couple of weeks).

If this doesn't work I may well opt for the MS-2 kit

Thanks for your help

Roger

[thechuckster]

Roger: you'll need to run two coils from the one spark output on the ECU - the 3TGxx needs both plugs in ech cyl to fire at at the same time.

If you interface the VR sensor with a HEI unit, you'll then need two more of those to drive the two coils. MIght be worth pricing 3 HEI units before discarding the VR interface.

I built my own VR interface using this circuit:
http://www.msextra.com/manuals/MS_Ex...r-inputV22.jpg

and in the same external box is 2 VB921s as i was going to shift to waste-spark on the 18R. The benefit of the LM1815 VR interface was using the one circuit to interface with a 22RE dizzi sensor and later an EDIS sensor pointing at a 32 tooth wheel on the front crank pulley.

[3jcelica]

thechuckster,

certainly an option building the VR sensor input circuit and the Vb921, it just means i have to get off my arse and build another box up.

However bear with me, the HEI not only has the VR senor conditioning providing appopriate Tach output but also drives one coil (hence no need for three modules, two will surfice). MSNSextra controls the dwell. So to drive one coil (which works fine from my experience resulting in no loss in power) on the 3tgxx you only need one (which i currently have) now you could potentially drive two HEI from the same VR input,

One modules tach output(module pin R) to wired to pin 24 on the DB37 (no need to provide both modules tach out puts)

Send the dwell (module pin E) and cranking signals (module pin B) to both modules resulting in both coils firing at the same time.

similar to this setup here but I guess two working in parrallel

http://www.msextra.com/manuals/MS_Ex...ual.htm#gm7hei

If this doesn't work I will then go back to the first option - i.e build the VR senor input circuit and VB921. This option has the added advantage of wated spark further down the track as you mentioned

roger

[XR Pilot]

3jcelica - seems like a lot of extra complexity for no apparrent gain. Instead of using 2 HEI modules, you could just use the standard VR conditioning circuit, and use two VB921's to drive two coils, or alternatively a single VB921 to drive a double-post coil such as a single Commodore V6 coil if you want to give single coil a shot. At least this way, if you have an ignitor fail, you have a $6 part to replace, at worst two VB921's, vs a HEI module. And as a bonus, wiring is simplified, and you can then play with launch control, rev limiters and flat-shifting down the track if you want to, which as far as I know isn't possible with the GM HEI module

[thechuckster]

roger: ah, i thought that the VR interface and coil driver parts of all the HEI boxes were intimately joined - if they act as two seperate circuits (as the 7pin unit would suggest) then not so bad.

XR_pilot: commode coils are also waste-spark not twin spark. You'll still need two coils for a 3tgte head.

[The Witzl]

Roger,

I can CONFIRM that the HEI module will work... but it will NOT work above 3000rpm with the Toyota sensor. THe toyota VR sensor's output voltage starts going too high for the GM HEI module, and the module just shits itself and starts skipping pulses and stuff.

Trust me, I ran one on my 18R-GE, and after about 2 months of fucking around, scratching my head, bench testing, signal analysing, and everything........ i smashed the fucking GM module and installed the VB921 coil driver.
Great Success!



... trust me on this one. The GM's VR conditioning circuit only works on a GM VR sensor.

[3jcelica]

The witzl,

not sure what was going on there, But I have run the GM module in an escort daily driven for two years with a locked dizzy and a 2tgeu vr sensor. I had no problems with the setup the whole time and it certainly work well over 3000 rpm in fact it worked good at 6000rpm. Maybe a dodgy module you had or some other noise associated with the signal.

With all your inputs I think I will venture down the VR signal conditioning circuit and the VB921 as it expandability in the future is better.

As an aside note I was wondering what people are doing about the TPS in relation to there 18rgeu setups. In the past I have used camira throttle body which addapted quite easily (besides accelerator cable). Just wonder if any one knows of a sensor that will sit in place of the ljet style switch.

roger

[oldcorollas]

is it a D shaft?
you can get some nice rotary position sensors for D shaft from.. farnell i think.. or used to.. they look basically like the haltech or wolf ones...

[3jcelica]

Old Corrollas,

Yep they are a 'D' shaft, Farnell do have them (~$55), but but I think the haltech ones may be better ($65 including connectors).

[The Witzl]

Or CHEAPEST OF THE LOT...... old fwd Nissan Pintara (2.4L motor).

Just remove the tps, and adapt to the 18R-GE throttle body. Note that the TPS wires are actually not the fixed plug, but the loom that comes out the back of the nissan TPS to an external 3-pin plug.


NOTE - I did this exact same mod on Riceburna's 3T-GTE running a Microtech LT-8. Was a piece of piss.