Cutting open 2.8 inlet mani

[VR6Will 0]

I remember seeing a thread somewhere, not sure if it was on here or on vwvortex, used the search on both, but still not found it.

 

Anyway the thread was comparing a 2.8 and 2.9 inlet manifold, basically cut the back off the 2.8 manifold took all the guts out and welded a plate striaght across the back so its like the 2.9 manifold...

 

does anyone remember the thread? any links to it?

[Kevin Bacon 5]

Yeah I remember that, can't remember where it is though.

 

There's no point in doing that tho. The Americans did it because they never got the 2.9 manifold, so EIP replicated it by cutting and shutting 2.8 mannies as you say.

 

The 2.8 manifold is actually better for torque anyway.

 

Put a standard Rado 2.9 and a standard 2.8 Golf highline on the rollers and they'll make the same power. There is little to be gained from playing with inlet manifolds unless it's a schrick or VSR.

[VR6Will 0]

yeah, but your comparing a 2.9 obd1 with a 2.8 obd2, the 2.8 obd1 only makes 174bhp

 

correct me if im wrong, but only difference other than 100cc is the inlet manifold and throttle body

[Kevin Bacon 5]

Yes but the OBD1 2.8 uses the same manifold as the 2.8 OBD2. The point I'm trying to make is the differences in power don't come from the manifold.

 

OBD1 2.8 throttle is the same bore as the 2.9 throttle. The 2.8 OBD2 throttle has the smallest bore, but makes the same power as a 2.9 despite the restrictions.

 

The only reason the 2.9 makes more power than an OBD1 2.8 is due to the capacity increase.

[VR6Will 0]

The point I'm trying to make is the differences in power don't come from the manifold.

 

The only reason the 2.9 makes more power than an OBD1 2.8 is due to the capacity increase

 

i disagree with both those statements.

 

Im saying its not just the manifold, but it helps.

 

I'd like to see a 2.8 obd2 run a 2.9 style inlet manifold

[Kevin Bacon 5]

Fine, go and look at Stealth racing dyno plots of both engines then.

 

Put a 2.9 manifold on an OBD2 2.8 and you lose the torque advantage.

 

I have actually tried these things, you're just speculating and guessing.

[VRTrickster 0]

I think ive heard somewhere before that a 2.9 mani on a 2.8 is supposed to give more torque, and thats the reason why people fit them?

[Kevin Bacon 5]

It gives a few hp at the top end, but does nothing to the torque.

[VR6Will 0]

looking at the maps, both odb1 5wire maf, you can see they are different, more ignition and more fuel on the 2.9 code there's your increased bhp, not from 100cc's

 

i bet you, take a standard 2.8 odb1, strap a 2.9 inlet on and run 2.9 code you get close to 190

[VR6Will 0]

maps...

[NormanCoal 0]

OBD1 2.8 throttle is the same bore as the 2.9 throttle. The 2.8 OBD2 throttle has the smallest bore, but makes the same power as a 2.9 despite the restrictions.

 

I dont agree with that, otherwise why would tuners, including Stealth, change the inlet and TB on ODB1 Golfs to that of the Corrado? Surely this lends weight to the fact that the 2.9TB is larger than that of the ODB1 Golf. Surely somewhere on here there are the pics or facts about this?

[NickVR6 0]

My OBD1 golf 2.8 definately felt like it had more torque than the corrado at low revs. The wifes vento 2.8 is obd2 and is much smoother than my C, and definately has more responce lower down. The corrado feels a lot quicker than the golf at high revs, and a little better than the vento.

 

OBD2 is much better for round town/traffic driving on a light throttle. Allways end up pulling onto roundabouts in 2nd, which my C wont have any of. I still like obd1, its raw and has character lol.

[12valve 0]

I had a brand new 2.9 vag block on obd2 in my 97 VR golf, and after i had put a few thousand miles on her it made 8LBft and 2hp more than the 100k 2.8 engine that i removed.

 

 

It eventually made 211hp & 206lbft after schrick manifold and cams.

[Kevin Bacon 5]

I dont agree with that, otherwise why would tuners, including Stealth, change the inlet and TB on ODB1 Golfs to that of the Corrado? Surely this lends weight to the fact that the 2.9TB is larger than that of the ODB1 Golf. Surely somewhere on here there are the pics or facts about this?

 

It isn't, they have exactly the same 65mm bore throttle plate. The only difference is the Golf throttle has a step in the throat to speed up gas flow for torque. The 2.9 throttle has no ramp in the throat but instead has a staggered opening action to mimic the Golf's ramp. The only throttle that is totally different to those two is the OBD2 one, which is smaller bore, again, for torque.

 

The 2.9 intake arrangements (larger plenum) were tuned for higher power, not torque, for autobahn cruising and the Corrado also has a higher rev limit than the golf, read into that what you will. In reality, a decent highline can keep with a 2.9 easily, so VW's efforts were somewhat wasted. They just never disclosed the gains OBD2 brought about.

 

As NickVR6 says, OBD2 2.8s pull a lot better than the 2.9 at almost all revs and ask Vince about throttles and manifolds and he'll tell you the differences on the dyno are negligable. In fact, in Vince's own words "We don't fit them anymore as the gains are so small". A larger throttle (i.e 68mm plate) will give you a better throttle response, but don't expect massive amounts of extra power.

[Mike Edwards 0]

So in summary the best combination is?

[Trig 0]

OBD2 everything :)

[VRTrickster 0]

I think Im going to fit my ported/port matched manifold at the minute with a reprofiled 2.9 TB. A little down the line use an adaptor to take the OBD2 TB with the manifold, and convert to OBD2!

Itll be interesting to here how yours is now with OBD2 trig ?

[Trig 0]

VRTrickster, You'll need the loom and all the other gubbins to go with the OBD2 TB, Micha (GermanCustoms) was selling adapters to go on OBD1 Manifolds I think...

 

Chack out my Members Gallery for the OBD2 review mate :)

[VRTrickster 0]

Yes thats right, thats who I got this lot off. I do realise that trig ,Im thinking in the future mate not right now. Id like to see what Ill get with the goodies Ive got so far! Is your car finished now mate how does it feel ?

[vdubjb 0]

I recently swapped to a 2.9abv TB and indeed the torque rush is gone. I did a rolling road recently and lost 10lb/ft after cams/Big valve head and the 2.9 tb. I am maing ~30 more hp though.

[eatthis 0]

i always thought the obd2 tb was bigger boew than obd1 hence uuprated tbs for obd1 bu can buy t not 2

[Mike Edwards 0]

The OBD 2 tb does appear to be larger diameter than any of the OBD1 items (I have obd2, ABV and AAA obd1) interestingly the AAA is a very late model item and has the same i.d. as the gas flowed ABV item.

 

As far as torque rush goes, the 2.8 manifold increased the kick in the pants feeling and appears to have moved it down the rev range (but has probably lost me some top end - but I don't spend much time at w.o.t. at the top of the rev range...)