Different inlet manifolds

[mgbv8mike 1]

I have 2 different upper inlet manifold, casting dates are 11/12/91 and 30/7/93.

Looking underneath, the later one has a larger triangular shaped plenum chamber, whereas the earlier one is more 'L' shaped.

Has anyone compared the performance of different standard manifolds ?

I am not looking for hypothetical opinions ( I already have my own, thank you)., but comments from someone who has actually tested the two .

[antera309 3]

Different VR6 OBD1 manifolds, Left to Right:

2.8 VR6 manifold, early engraved type (rare)

2.8/2.9 VR6 manifold, early type

2.8/2.9 VR6 mainfold, later type

Difference between 2.8 & 2.9 manifolds (later type)

2.8 on the left, 2.9 on the right.

All of the manifolds pictured above are OBD1. The OBD2 2.8 manifold is similar to the 2.9 one in the above picture (marked "E"), except with changes to the throttle body mounting face and no ISV pipe flange (the flange right next to the TB mounting face). All OBD2 manifolds were the same design.

An OBD1 manifold will not fit straight on an OBD2 engine due to the different throttle body mounting points. However, an adapter is available which gets around this problem: http://www.pixum.de/members/chocolatestyler/?act=a_view&album=2037917&st=1&sid=r4wz5d0e7f1e074d0ff517f20f4efd2d&sid=r4wz5d0e7f1e074d0ff517f20f4efd2d

OBD2 manifolds do not fit OBD1 engines.

To complete the picture, here are the Schrick VGI & VW Motorsport VSR Manifolds:

Shrick VGI manifold with Nothelle Branding. The throttle body is fitted in this pic:

The aftermarket Schrick VGI is available for both OBD1 and OBD2. The manifold has a removeable rear section which can be changed for OBD1/OBD2 fitment without having to replace the entire manifold. The Schrick VGI uses an internal vacuum-operated flap to boost low-end torque (particularly between 3000 & 400RPM). It also has tuned-length inlet runners which boost top end power. Expect another 10-15BHP and 25-30lb-ft of torque with one of these fitted. The only drawback to the Schrick manifold is that it covers the spark plug holes, so the manifold has to be removed every time you change your plugs. Shrick VGI manifolds are available to buy new and, thanks to a 30+ group buy organised by the VR6OC in 2002 are fairly plentiful on the UK second-hand market too!!

The Schrick VGI is available with or without the Schrick logo. In the US, the Schrick VGI manifold is also sold by Nothelle, and bears the Nothelle logo. However, it is exactly the same manifold.

The VW Motorsport VSR manifold was a limited-edition aftermarket option offered by VW themselves in 1992 & 1993. It works in a similar way to the Schrick VGI, using a vacuum operated flap to boost low-end torque. It does not have tuned inlet runners, so does not give the same top-end BHP figures as the Schrick, but its fitment is more "OEM", allowing you to run the stock engine covers. It also allows the spark plugs to be changed without the manifold having to be removed. VW Motorsport manifolds are no longer available new and are EXTREMELY rare. It is believed that only 500 were made, and most are now in the hands of VW enthusiasts. The VSR is OBD1 only, but can be fitted to OBD2 engines using the aforementioned throttle body adapter.

[Nerih 0]

tbh im surprised no one has mentioned, the manifolds are off odb1/odb2 cars, the odb2 have variable fuel injection for rear bank of cylinders, which changes the flow characteristics in the rest of the manifold when under slight vaccum (partial loading).

[FishWick 21]

Good post Antera. You've highlighted the biggest differences in pic N. You can see why the Euro 2.9 is so sort after in the US looking at that. Eurospec do a copy manifold buy cutting out the arrowed bits and plating over the top to give the same plenum area as manny E. E is the better manny for FI too.

OBD2 manny is the same as E but OBD2 also has the stepper motor throttle.

As for the injection, all coilpack VR6s have cylinder selective timing and sequential injection.