We are in a quandry about the correct exaust manifold for our GEN 3. We read the stock ones crack, the stainless ones crack, the iron ones are heavy... which way to go?
What works, what lasts and what about performance?
...Chrissi

I assume this is for a turbo version of the gen 3.
Did Greg Richter say his off the shelf  after market HKS TO4 turbo
manifold cracked?

The 1989-92 stock Mazda cast iron turbo manifold does not crack in automotive
service, it will fit the gen 3 and it is not that heavy as I recall
because it is small. See the picture below.

If you can afford it Inconel is the ultimate way to go.

Performance does not seem to be that big of an issue. The turbo
is capable of generating way more power than the turbo and the engine
can tolerate for long periods of time. People have got 800 HP out
of a 13B for drag racing with a simple turbo exhaust manifold.

The big question we have now is; how much boost can you run continuously
and for how long? Greg is our guinea pig.

We discussed this for years off and on and it is all on the CD.

Paul Lamar

In a recent email with Greg, I posed this very question.  I am sure he won't mind my sharing with you.

Greg Richter wrote:

Hi Dale,

The manifold is an HKS unit that the rotary racers like.  Heavy, but
bulletproof.  You may want to checkout www.rotaryaviation.com  ...etc.

snips

On further investigation, I have found at least one source of these at  http://www.rx7store.net/turbomanifolds.htm , but they are pretty pricey at $600 ... I still have hopes
of maybe getting one used, but I like "bulletproof" and may sacrifice the weight and "bite the bullet" and shell out if I have to.

I see this as a "critical failure" part, failure of which is not an option if it can possibly be avoided.  I am still not clear on the engines' ability to run in the event of
turbo failure?  Reduced power, I would assume, if it runs ... but how much?

Dale Smith

The HKS works with the Garrett TO4 so the bolt pattern is different
than the stock turbo bolt pattern I think. Perhaps an adapter can be made.
As a quick check the TO4 bolt pattern is 2.750 by 3.250 inches. My 91 turbo
is up at the hangar so I can't check at the moment. I know the 87-88 won't
fit the TO4 pattern.

If you go the HKS TO4 route you are looking at another $1000 for the TO4.

Here is Greg's HKS showing the blocked off waste gate port. Apparently Greg
is getting along with out a waste gate.

Paul Lamar

Paul,

I know your $1000 figure is correct, possibly even conservative ... but FWIW, a new T04 is currently for sale on eBay at a bid price of $500 (as we speak) ... URL is:
http://cgi.ebay.com/ebaymotors/aw-cgi/ebayISAPI.dll?ViewItem&item=601022275&r=0&t=0

Since I am not in a buying mood after the new engine purchase, but I thought I might post it for others on the list that might be.

Dale Smith

We need the details on that turbo but it sounds like a real buy
if someone does not mind a less than optimum match with the rotary.

Paul Lamar
 
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