Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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The C20XE throttle body has a two stage butterfly valve system to provide a smooth throttle as airflow is gradually increased into the inlet manifold.
From reading up on Mig, the first valve opens at 22deg of throttle, with the larger main valve opening at 24deg.
With the Ecotec pipe, you need to use an adapter to mate the round pipe to the teardrop shape of the tb - so now the only hole for air intake is the main valve.
Without the butterfly mod to remove the wedge or 'ruck sack', won't the engine be hesitant until 24deg? With the wedge removed it's still only open at 22deg.
Any thoughts on how to claim back the missing 22 degrees worth of air flow? Not really essential admittedly, but the engines have worked so well across so many platforms for all these years and it seems a shame to just butcher the air intake 
A possible solution would be to enlarge the hole on the adapter plate to not restrict air flow, but then the ecotec pipe will be useless (Powercap time!)...
Or perhaps by making a twin ported adapter plate, with a second air take off from the Ecotec pipe to feed the first valve, initial response would be better?
(or the airflow could get so mangled with the extra pipe work you'll just end up restricting it more!).
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ed
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Registered: 10th Sep 03
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Solution: Don't wast your time doing things by half. Buy a powercap.
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James R
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Registered: 4th Feb 03
Location: 205GTi16/306GTi16
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It's a hard one, but at light throttle the air will still be able ot flow over to the primary TB, then when you open up you may find a slight "gulp" effect, esp if you take out the Terry orange triangle. But the later 20XE's didn't have it on. This is becuase the 2.5motronics has a throttle switch, ie, close, in th emiddle WOT. and the later 2.8moptrinic has a potentometer, so the amp is more refined and less dictated from the AFM. seems to work well for many though.
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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quote:
Originally posted by 1800ed
Solution: Don't wast your time doing things by half. Buy a powercap.
I had two.
One was an MTech/Mantzel one, which I sold.
The other was a weird one, but still fouled the bulkhead, which I sold.
I agree, the Powercap is a better route to take, but I didn't want to butcher my firewall unnecessarily..
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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quote:
Originally posted by j1400
It's a hard one, but at light throttle the air will still be able ot flow over to the primary TB, then when you open up you may find a slight "gulp" effect, esp if you take out the Terry orange triangle. But the later 20XE's didn't have it on. This is becuase the 2.5motronics has a throttle switch, ie, close, in th emiddle WOT. and the later 2.8moptrinic has a potentometer, so the amp is more refined and less dictated from the AFM. seems to work well for many though.
By later 20XE's do you mean dispack? So these are sans-wedge?
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ed
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Registered: 10th Sep 03
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Why don't you have to pipes attatched to the ecotec adaptor pipe - then either make a T piece to join the two pipes together - more like y shaped piece to keep turbulance to a minimum or have a smaller air filter attatched to the extra pipe instead... Two air filters 
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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quote:
Originally posted by 1800ed
Why don't you have to pipes attatched to the ecotec adaptor pipe - then either make a T piece to join the two pipes together - more like y shaped piece to keep turbulance to a minimum or have a smaller air filter attatched to the extra pipe instead... Two air filters
Sounds too messy, SFi box or Powercap is ideal.
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ed
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Registered: 10th Sep 03
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But then you have to cut the bulk head... Either have messy or cut the bulkhead. Unless it is possible to make the ecotec adaptor plate an oval shape to include the smaller tb and use a different type of pipe that would stretch over it...
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ed
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Registered: 10th Sep 03
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Or just stick a sock over with a jubilee clip - I hear Nike ones are best.
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miles
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Registered: 25th Mar 02
Location: plymouth Drives: Astra Sport
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I dont understand. The throttle body tapers down into the seperate small and larger butterflies, so as long as whatever pipe/adaptor seals to the top of the tb whats the problem?
I've removed my ruck sack, not noticed any difference in driving.
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miles
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Registered: 25th Mar 02
Location: plymouth Drives: Astra Sport
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You are aware that the picture is of the bottom of the throttle body?
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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quote:
Originally posted by miles
You are aware that the picture is of the bottom of the throttle body?
Yes
I couldn't be arsed to trawl through pages on Mig to find the "in" side 
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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quote:
Originally posted by miles
I dont understand. The throttle body tapers down into the seperate small and larger butterflies, so as long as whatever pipe/adaptor seals to the top of the tb whats the problem?
Because the intake pipe has about a 40% reduction in size compared to the underside of the SFi box/Powercap.
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Adam_B
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Registered: 13th Dec 00
Location: Lancashire
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all this seems a bit extreme on a fairly standard engine, would be different on a 300bhp race engine. but then you wouldnt be using the standard throttle butterfly anyway.....
Never really noticed any hesitation on either of my engines 
[Edited on 18-12-2004 by Adam_B]
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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People seem pro-active when removing the wedge, but no-ones considered implications of blocking up half the tb?
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myke
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Registered: 7th Feb 01
Location: High Wycombe, Buckinghamshire
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quote:
Originally posted by Joff
People seem pro-active when removing the wedge,
and the afm mesh
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James R
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Registered: 4th Feb 03
Location: 205GTi16/306GTi16
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quote:
Originally posted by Joff
quote:
Originally posted by j1400
It's a hard one, but at light throttle the air will still be able ot flow over to the primary TB, then when you open up you may find a slight "gulp" effect, esp if you take out the Terry orange triangle. But the later 20XE's didn't have it on. This is becuase the 2.5motronics has a throttle switch, ie, close, in th emiddle WOT. and the later 2.8moptrinic has a potentometer, so the amp is more refined and less dictated from the AFM. seems to work well for many though.
By later 20XE's do you mean dispack? So these are sans-wedge?
Yes that's right. I'd personally hack the abck off the SFi box as it look nicer than the powercr*p imo. You will also loose less midrange torque as a result.
quote:
Originally posted by myke
quote:
Originally posted by Joff
People seem pro-active when removing the wedge,
and the afm mesh
Yeah no the best idea
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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quote:
Originally posted by myke
quote:
Originally posted by Joff
People seem pro-active when removing the wedge,
and the afm mesh
bless 
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miles
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Registered: 25th Mar 02
Location: plymouth Drives: Astra Sport
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Whats wrong with removing the afm mesh?
Any pics of what your on about?
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James R
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Registered: 4th Feb 03
Location: 205GTi16/306GTi16
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The AFM on the 20XE has a mess on both sides of the AFM. you can remove these to "improve" airflow, but the meshis there to take the turbulence out of the air stream. It can result in poor low throttle driving. Least that's what I found.
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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In theory the mesh would promote laminar air flow, but it's more likely the mesh is there to stop people damaging the fragile wire and/or stop bits of the AFM finding their way into the engine when they break up.
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miles
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Registered: 25th Mar 02
Location: plymouth Drives: Astra Sport
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I meant pics of the ecotec pipe.
I removed my meshes.
I cant see that they have any practicle use. There is no way they would stop the tiny afm element; the mesh is too coarse for that.
It would be useful if the standard paper filter got wet and broke up, but thats the only scenario I can think of.
I cant see how they can affect low throttle driving. Surely whatever flow pattern advantages they promote must be outweighed by the restriction?
I've removed mine anyway 
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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Ah.
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and-m
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Registered: 5th May 02
Location: Liverpool. Drives. Skud vRS.
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I dont see the problem, mine drives fine with the ecotec pipe and makes good power. Other cars have been RR'd and have made good power figures with the ecotec pipe.
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Joff
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Registered: 17th Oct 00
Location: Cambridgeshire
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quote:
Originally posted by and-m
I dont see the problem, mine drives fine with the ecotec pipe and makes good power. Other cars have been RR'd and have made good power figures with the ecotec pipe.
So you're not interested in seeing if it can be improved? 
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