4agze, making the SC pre throttle body.

[Casey-G]

Hey all,

Need your thoughts on this idea i had, it will involve keeping the car supercharged (for now at least) and use a naturally aspirated inlet manifold.



Having a chat with the old man a few mates in theory it should work, i cant quite pull up much info on it however.

So ill put it out there to the rest of you to tell me what ive missed...


Obviously the top SC bracket will need fabrication, no biggie.

not to sure what i do with the SC air inlet?? Came to the conclusion that it just has the air cleaner attached to it some pipework.




its late, im a little fatigued but all feedback is appreciated.

[JustenGT8]

What's your question? Will putting the SC pre throttle body work? Not very well. You need a bleed valve to vent excess intake charge on throttle close and still keep the bypass valve operating for cruise....in theory you could get the plumbing working but you will have compromised the the way a positive displacement SC is supposed to work.

why not use the n/a inlet (why BTW?) but simply move the TB pre SC like it should be?

[Casey-G]

Okay yeah sorry,

Motor that is going in has a bigport head with NA inlet manifold, i dont have a gze bigport inlet manifold.

Obviosly the the NA manifold will favour me when the sc dies and it comes time to turbo it, plus the NA TB is a little bigger than the gze TB.

I can retain the ABV thats not that much of an issue.
how does the pre TB method comprimise the positive displacement blower?

[JustenGT8]

because they are just designed to move air and so it makes little sense to move it straight into a throttle plate

just take the TB off the big port manifold....mount it in front of the SC....run the SC thru an FMIC into the big port plenum...win.

[e30-323ti]

If you have a look at the Blitz SC kits for the 3S-GE Altezza's, the SC goes before the TB and they run (what looks like) a BOV.

They seem to go just fine with that setup.

Also, even if you are going to an NA inlet, doesn't mean you need to keep the TB bolted to it!!
Put the TB in the piping leading to the revised SC inlet.[edit] What Justen said[/edit]

[Casey-G]

Not really keen on the idea of TB pre SC...


you get a funny throttle response off boost, plus the TB restricts the SC's inlet tract.


Im going to run the TB post SC, people have done it with good results such as improved head flow from the manifold, and improved throttle response. I think its worth having a go at. I imagine the hunting of the motor will dissipate after doing it.

[Harreh]

What funny throttle response? Perhaps thats more related to your ECU or aftermarket ABV.

I know you're just doing this so you can be a mad sick kent with BOV Casey.

In all seriousness I'm gonna watch this, the stock SC inlet mani sucks ass and I'm upgrading my throttlebody anyway so I am interested to see the result

[Casey-G]

What funny throttle response? Perhaps thats more related to your ECU or aftermarket ABV.

I know you're just doing this so you can be a mad sick kent with BOV Casey.

In all seriousness I'm gonna watch this, the stock SC inlet mani sucks ass and I'm upgrading my throttlebody anyway so I am interested to see the result

Nah, i just think it has a bit strange throttle response down low rev range.


Im just gonna turbo the fucker to save me having to rip the SC12 out when it gives up on life.

two birds one stone, more fasts

[Harreh]

Mine has odd response but thats mainly due to deleting the ABV

[TERRA Operative]

The stock system has the TB pre SC. I've done the new ABV mod and Gen2 3SGTE TB and the throttle response is nice and crispy.

[Dangerous Beans]

If you have the TB post SC, then when the TB closes the SC starts pushing air into basically a closed tube. This means that the SC starts pushing against a very high pressure ratio, becomes inefficient, produces lots of heat, and kills the SC. The ABV helps prevent this, but it is not designed to move 100's of cubic feet, just equalise pressure at 15% throttle, so you still get problems.

You could do TB post SC, but you would need a much larger external bypass valve (~90% TB size, maybe?), and it would might increase the power draw of the SC at cruise.

edit: as for systems that put TB post SC, they probably use a centrifugal SC, and it isn't an issue in that situation as the centrifugal SC allows air to flow backwards through the SC.

[Invid]

I've run a TB post SC on my 2TGEU and it works fine. Had to run a plumbed back BOV to stop the SC pushing air against the TB when you're off the gas pedal (You can use the plastic Bosch bypass valves if you want to do it on the cheap). Otherwise works great (sorry Justen).

Set up runs:
Air filter -> SC -> FMIC -> TB

[Casey-G]

If you have the TB post SC, then when the TB closes the SC starts pushing air into basically a closed tube. This means that the SC starts pushing against a very high pressure ratio, becomes inefficient, produces lots of heat, and kills the SC. The ABV helps prevent this, but it is not designed to move 100's of cubic feet, just equalise pressure at 15% throttle, so you still get problems.

You could do TB post SC, but you would need a much larger external bypass valve (~90% TB size, maybe?), and it would might increase the power draw of the SC at cruise.

edit: as for systems that put TB post SC, they probably use a centrifugal SC, and it isn't an issue in that situation as the centrifugal SC allows air to flow backwards through the SC.

I also didn't mention that the clutch is triggered to engage at 55% throttle and off at 54%... it would never push into a sealed volume. This in itself pretty much deny's the need for a BOV but you would hook one up to be on the safe side..

Being FWD SC12 front mounted inter cooler piping tends to be on the long side, I think this is where i found the strange hunting and throttle response.

Anyways, in theory and if i wanted to do it it would work, but the cost of replacing the charger later vs a turbo now is outweighed.

[Hen]

I built a 4AGZE with NA intake manifold and SC pre-TB. I put a fairly big blow off valve between SC and TB.

It works, but I have driven it very little since getting it running. You will have to be careful with your SC switching point.

[TERRA Operative]

Also, to prevent the hunting issue with a front mount intercooler and TB pre SC, you need to replumb the ISCV to short circuit the entire intake tract, so it goes from pre TB straight into the intake manifold.