Guinness Induced Ramblings

[Guest turbolag]

Siiting here drinking a pint or 5 or the blackstuff, and looking at my pile of spares in the lounge (really should tidy up!) had be looking at my spare inlet stubs withthe ACAV butterflies.

 

I'd lit a GTi6 inlet, but don't have one. Does anyone think anything is to be gained by perhaps flowing the ports on my spare inlet, perhaps combined with knife edging the ACAV butterflies, or removing them altogether. Looks like a fair bit of meat could be removed from there.

[welshpug 1,657]

I've often wondered ever since I heard that the GTi6 manifold flowed better that it would be nice to do some work to the ACAV manifold, to see if any gains could really be had as the ACAV system really does work but doesnt flow enough at the right times.

 

I think what has highlighted that the ACAV is worth looking as it the popularity of the Twin-port Vauxhalls, which I'm sure are a GM version of the same thing.

[Jer309GTi 3]

I always wondered what the Twinport thing was all about...

[KRISKARRERA 2 1 Cars]

Me too!

I'd like to get hold of an XU10J4RS lump and bung it in a 405 though I'd use an Xsara VTS to save killing a GTI6. plus also the VTS has the Mi16 gearbox.

[Guest turbolag]

Ah, well it's encouraging that the principle at least sounds sensible.

[Sloppy 0]

it really is far to long and crap.

 

after replacing the vacume hoses, the vacume cylinder thingy the cleaning it they still lack the flow through the rev range.

 

Done get me wrong my mi16 from 5.5-7k pulls like nothing ive ever driven but i cant keep it at these revs all the time, and before this its poor, my td literally is faster all be it heavily tuned.

 

i have invested in the gti 6 inlet, going to polish the 'trumpets' witin it before fitting to get maximum flow too.

 

now when i sit and look at the gti inlet, for starters it has a inlet butterfly wich is literally twice as big, i will upload some pics as i took some during the swap.

 

then the gti inlet is really direct i.e bang on a filter on the end and the distance to the valves is just over a foot to the first valve, on the avac system the inlet is massively drawn out so the air is having to travel literally twice as far to get to the valves, through crappy pipe work AND a much smaller butterfly.

 

if it was so good the gti would have had it on, and it does not, this is enough for me!

[stuart.m 0]

then the gti inlet is really direct i.e bang on a filter on the end and the distance to the valves is just over a foot to the first valve, on the avac system the inlet is massively drawn out so the air is having to travel literally twice as far to get to the valves, through crappy pipe work AND a much smaller butterfly.

<{POST_SNAPBACK}>

 

yes the gti manifold is much better as it comes. id still be very curious to see if much gain could be made by altering the original manifold setup though although id imagine it would cost alot more to make it flow as well as a gti6 manifold than it would cost just to buy one.

Edited July 10, 2007 by stuartm

[welshpug 1,657]

it cant be that bad or Vauxhall wouldnt be using the same principle on many of their engines, from 1.2 16valvers to 3.2 V6s!

[Guest pugmt]

It is all to do with trying to increase the low down torque and drivability, manufacturers work to principals, noise, drivability and a power aim. the reason for the AVAC 0r VASC system was to get rid of the flat spot that was so pronounced on the 1.9 mi16, which this acheived but is unfortunatly restricted at higher RPM.

[Sloppy 0]

It is all to do with trying to increase the low down torque and drivability, manufacturers work to principals, noise, drivability and a power aim. the reason for the AVAC 0r VASC system was to get rid of the flat spot that was so pronounced on the 1.9 mi16, which this acheived but is unfortunatly restricted at higher RPM.

<{POST_SNAPBACK}>

 

meh that not really the characteristic, the avac produces massive power at high revs and they are supposed to pull harder than the 1.9 at these revs, mine went like a rocket after 5.5k but its all to late!

 

The gti manifold should give a nice liner power curve right through the revs, al be it less low down torque and less high end 'rev' but liner is more driveable.

 

The avac makes the inlet longer at lower revs for torque and short fat inlet at high revs for power, the gti one is short all the way through so as said less low down torque but my second car is a derv so i get plenty or torque with that!

Edited July 12, 2007 by Sloppy

[Jer309GTi 3]

So does the avac give the 2.0 more torque than the 1.9? I know the 1.9 has the extra 5bhp (on paper), but don't recall seeing any torque figures

[JamesLeMans831345402285 0]

So does the avac give the 2.0 more torque than the 1.9? I know the 1.9 has the extra 5bhp (on paper), but don't recall seeing any torque figures

<{POST_SNAPBACK}>

 

My dad has owend at least 5 mi's from the late 80's onwards and says the first ime he drove a 2.0 he thought there was something majorly amiss. Guess that says it all. I can say tho having recently fixed the avac on my lemas it does make a big difference in low down torque. Which in my unfortunate driving life of my house to town and back makes it much more 'drivable'. Especcially as i dont like to rev it beyond 5k because of the stupid 4" fartbox the previous owner saw fit to weld to the centre pipe which he welded to the cat. Grrr! just gotta wait for me mate to get acess to his shop to grind it off so I can have a nice quiet standard. Sorry if that wandered a bit off topic but a few beers will do that..

[Guest turbolag]

it cant be that bad or Vauxhall wouldnt be using the same principle on many of their engines, from 1.2 16valvers to 3.2 V6s!

<{POST_SNAPBACK}>

Indeed. i used to spanner poxhauls for a living and recall that they even sold an Irmscher (back when it was proper Irmscher, and not the poxy Vauxhall manufactured kit with the 'i-line' name licenced to it) tuning accessory manifold for the 18SE, 20SE, 20NE, C20NE family of engines that was visually very similar, but worked out has having longer, tuned tract and gave a very subtle, but noticeable improvement in performance.

 

Distance twist filter and head isn't always a benefit either. The Mi 2 litre works well, as Sloppy points out, with the GTi6 setup and the TB close to the motor - on many other cars it can make the power delivery rather poor, and unusable, if this distance is alterered and the throttling/resonance charcteristics of the gas flow are messed with.

 

Getting mine opened out would be no prob - my mates dad owns Mez Porting, who do motorcycle head tuning (mainly BMWs) so i'd take it to him, but till in 2 minds whether to try or just save my pennies for the GTi6 inlet.

[welshpug 1,657]

keep it looking stock

[Guest turbolag]

I'm inclined to err in that direction mate. Though it'd be a pain if it doesn't work, i won't have cost me owt more than a gasket. I'm still debating about ditching the ACAV on a flowed inlet, or to knife edge the butterflies/lose some meat off the butterflies.

 

Need to get my rear brakes sorted first, but i can't find my caliper piston windie-innie tool. Duh!

[welshpug 1,657]

biig screwdriver is all you need

[Guest turbolag]

Indeed - I have the Glasgow socket set on standby!

[KRISKARRERA 2 1 Cars]

Jer, 1.9 is 133lbs @ 5000rpm. 2 litre is 135lbs @ 3500rpm.

 

I've got the Autocar review of the 306 S16 - same as the 2 litre Mi 405 but 20kgs lighter. The low rev performance figures are better, you know, 50-70 and all that. Obviously makes the car more flexible, less need for gear changes etc. But then I always think that if you're wanting to go fast in the 1.9 just use those revs.

 

What's interesting is if you take the 1.9 Mi16 to 2 litres it'll make more than 135lbs!

 

The GTI6 engine makes more torque low down than the 1.9 Mi, I know part of that is the extra 93ccs but PSA did something else in the head to help things I'm sure.

[Sloppy 0]

ha ha like you say the 2.0 is torquey low down and when i drov mine back from birmingham to leeds it really was a pleasure to drive, BUT the avac makes it behave very wierdly between say 3.5-5.5 then it comes alive.

 

I have to agree with KRISKARRERA, i bought an mi16 to drive it not to commute, so when i put my foot down i dont care theres losts of low down torque i just want blistering acceleration untill the rev limiter cuts in in 1st 2nd and 3rd

 

the avac seem to maske it slower to rev up fast which just feels very dissapointing. Although i do agree similar systems work well on other cars it does not on the mi16 from what ive heard and seen.

 

You can apparently get enven more power from the gti6 manifold if this is shortened, but i suspect this would make to thrque even lower to the point of making it hard to drive

 

ive sent my phone off to be fixed when it gets back i will get all the pics i have of the manifold swap so far.

[Guest turbolag]

ive sent my phone off to be fixed when it gets back i will get all the pics i have of the manifold swap so far.

<{POST_SNAPBACK}>

Ooh, yes please! (feels wallet titching and ebay trigger finger flexing...)

[KRISKARRERA 2 1 Cars]

The 2 litre has thicker conrods and less squish.

[welshpug 1,657]

The 6 has a far superior exhaust manifold, fit a tubular item to an Mi and you'll get a fair bit more grunt out of her, I know of an S16 that I've had a ride in, which is totally standard bar a larger bore downpipe and decat exhaust and its hit 171bhp on the rollers many times and a few different places, mine has made just over standard with a catback

[JamesLeMans831345402285 0]

The 6 has a far superior exhaust manifold, fit a tubular item to an Mi and you'll get a fair bit more grunt out of her, I know of an S16 that I've had a ride in, which is totally standard bar a larger bore downpipe and decat exhaust and its hit 171bhp on the rollers many times and a few different places, mine has made just over standard with a catback

<{POST_SNAPBACK}>

 

 

I take it you cant bolt the -6 mani to the mi 2.0litre? Would be interesting to find out.

[welshpug 1,657]

nope doesnt fit! stud and port pattern is very diffferent

[JamesLeMans831345402285 0]

nope doesnt fit!  stud and port pattern is very diffferent

<{POST_SNAPBACK}>

 

Knackers