I'm in the process of swapping out my 1991 vert engine (blown) with a reman 1989 GTU engine. The intake manifold on this 89 engine is a VDI while the one on the vert is a regular (extension) manifold. I'm am wondering if I need to keep my original manifold, or use the VDI. Also, this VDI manifold has some weird valve right below the BAC..small metal tube coming out? I'm thinking that it might be the "cold start assist valve". if it is, would it be ok , to take this off and use a BOP? Thanks, PJ

 

An '89 GTU and '91 vert are both going to have the exact same engine (series 5 NA). If they don't, someone (or you?) swapped in a series 4 engine.

 

Hi, Thanks for your answer. Yes The reman is definitely S-5 (from Rotary Ressurection) .. has the anti-knock sensor inlets right abouve the "T' Plugs etc.

I guess what HAD me confused is that the reman has one of those VDI Intake manifolds, looks so different from the vert's smaller S-5 extension Manifold on the blown motor.

This VDI manifold has eveything brand-new, including the entire throttle body, actuators etc

My bother ( a GM mechanic) wants to use the original Vert manifold and throttle body on this new engine...only for the mere fact that this VDI manifold "looks different"..mainly that subzero assist valve has him confused. Well after hours of research on this great website..I learned that this can and should be removed as it is useless. Mazda had a TSB on removing it in 1990. I guess that I need to get a block off plate for that

In any case, I said "Absolutely No" to his plan of using the old manifold and TB ..I'm a girl and he is a boy...think that an arguement ensued?? A huge one.

My thought is to use the reman engine and all the correct peripheral parts that came on the long block....do not mix and match old **** on a basically new engine.

What are your thoughts?
PJ

 

Either your vert is an 88, or you're car doesnt have is original motor, because a 91 VERT would have come with VDI.

 

No, it is definitely a 91. Probably someone had replaced the current blown motor along the way?? Probably explains why it when to crap ..9replaced it with crap!) Thanks, PJ

 

As replied to your PM:

As I mentioned before, all S5 NAs had the exact same engine, so every single part will be interchangeable. I'm also not sure what you mean by the "extension manifold." The intake manifold consists of 3 parts: the lower section w/ aux. port actuators (LIM), the upper section w/ VDI actuator (UIM) & the plenum which is bolted to the throttle body. All of these parts should be identical if both engines are 100% S5. It's possible someone has mixed and matched parts (ie S4 intake manifold on an S5). Take a look through the S4 and S5 factory service manuals for pictures to compare. Download links are in the FAQ, or go here: http://www.rotaryheads.com/PDF/2nd_gen/index.html.

And the cold start assist is useless and should be removed. Mazda released a technical service bulletin years ago suggesting its removal.

 

In the Haynes Manual ( almost useless!), on page 137, there is a section on the VDI manifold (1989 -forward) the first sentence reads " On 1989 models, a variable dynamic effect intake (VDI) manifold is used in place of an extension manifold". i'm thinking that the earlier S-4 etc manifolds were what Mazda referred to as "extension" manifolds??



I've been to that thread..spent many hours! It is as you suspected, the blown engine has an S-4 LIM and and an S-5 UIM. Yea, I read up on that cold start assist valve, I will just cap it or buy a BOP ..in any case , I'm not going to worry about it. Thanks for your help!

PJ