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Vacuum Module Turbo 202

Started by _73gtr_ , Jun 03 2010 02:15 PM

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9 replies to this topic

#1 _deviot_

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Posted 03 June 2010 - 02:15 PM

I'm currently putting a turbo 202 back into my car again and keep running into little problems.
Last time I was using a supra 5 speed but as this time I'm going auto and using a trimatic.

I'm just wondering as to where I would hook up the vacuum module to? Before the turbo where there is constant vacuum (think this is correct?). Or after the turbo where vacuum would be present at low loads and positive pressure at full load?

As my understanding is that the vacuum module is used to up shift gears when there is vacuum. This leads me to believe I should hook it up after the turbo or to the inlet manifold?

Any can confirm or deny this?

Thanks.

Edited by deviot, 03 June 2010 - 02:18 PM.

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#2 76lxhatch

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Posted 03 June 2010 - 02:46 PM

You don't want constant vacuum as such, it needs to be a load indication. I don't know much about turbo stuff but I would guess that you'll need an adjustable aftermarket modulator so that you can cater for any differences in vacuum compared to a naturally aspirated engine anyway.

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#3 _deviot_

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Posted 03 June 2010 - 02:50 PM

So that would mean after the turbo with the source from the inlet manifold, I wonder how the vacuum module will go seeing boost?

Anyone else got any ideas, worst case trail and error for me

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#4 J-Rod

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Posted 03 June 2010 - 03:37 PM

How about using a check valve to prevent the module seeing positive pressure?

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#5 _oldjohnno_

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Posted 03 June 2010 - 04:34 PM

Depends on whether it is draw through or blow through. Draw through is easy to hook up, just connect it between the carb or throttle body and the turbo. An adjustable modulator would help with fine tuning part throttle shift points.
Blow through would be more of a challenge as there's nowhere to easily obtain a vacuum signal. You could possibly fabricate a mechanical modulator or convert/make a pressure actuated unit.

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#6 _mello92_

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Posted 03 June 2010 - 04:38 PM

Going out on a limb here...but if you manualised the trimatic, would you still need the module?

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#7 _deviot_

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Posted 03 June 2010 - 04:43 PM

Well it is in fact a draw though LPG system and I do have a port between the throttle body and turbo for the brake booster. I can just tee that line off.
I was under the impression that when producing boost the air space between throttle body and turbo would be under vacuum?

Unless that is what I want?

Maybe if someone could explain what the module does or more so the effects of vacuum on the module. (ie: shift up/shift down etc)

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#8 _oldjohnno_

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Posted 03 June 2010 - 04:53 PM

Basically as the vacuum increases upshifts occur earlier and are softer. So gentle driving with not much throttle tends to make it shift up at low rpms. At low or no vacuum such as when you have your foot in it then the upshifts occurs at a fixed rpm as set by the centrifugal governor. The other control is the kickdown detent which is only active at full throttle.
It is possible to have a little vacuum between the throttle and the turbo at full noise, particularly if the TB is a little bit undersized. If that turned out to be the case I'd be surprised if it couldn't be overcome with a little creative shimming or an adjustable modulator.

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#9 _deviot_

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Posted 03 June 2010 - 05:00 PM

It all makes sense now

I guess ill have to see with a bit of trail and error.

It's got a Impco 225 with a RB30 Turbo Throttle body.
Still a few days before it all goes back in, I hope the changes this time are worth it.
Once it's up and running I'll post back and let you know how I go.

Thanks for all your help.