Intake manifold support bracket delete?

manga_blue · Postby **manga_blue** » Sat Jul 05, 2014 7:38 pm

Has anyone done this? Did it work out OK?

I can't really understand why the manifold needs this support. The manifold is not THAT big. It has a good solid flange with a fair number of studs holding it. I used to have Fiats with pairs of Weber IDAs and big DCOEs swinging off the manifold and they didn't break. Mind you nearly everything else on them broke, sometimes, repeatedly, but not the manifolds. The NA8 setup is positively featherweight in comparison.

The trouble with the bracket is that it makes skin removal a necessary part of filter removal, especially with a cold side coolant re-route. It also limits the size of the filter you can put there.

Compare an MX5 one to the one that goes into a lot of other Mazdas. The base plates and diameters are the same but the longer one has about twice the filter area.

The longer one also gives you a lot more purchase to unscrew it.

I could just cut out part of the bracket where it fouls the extra length, but removing the bracket entirely looks a better way to go, as long as it doesn't cause any other problems.

zossy1 · Postby **zossy1** » Sat Jul 05, 2014 8:45 pm

I bought a damaged NA8 from the auctions a few years ago, one of the ones I ended up fixing and selling. It had had the bracket removed by a PO and it seemed to be holding together fine. No idea how long it had been gone for though.

Lokiel · Postby **Lokiel** » Sat Jul 05, 2014 9:21 pm

A lot of guys remove this with no ill-effects, even with track dríven cars.

FM suggest it's not needed but I'd only remove it if you really need to. In my case, I've removed it since it obstructs my oil filter relocation hoses.

Nevyn72 · Postby **Nevyn72** » Sat Jul 05, 2014 10:02 pm

I was fortunate that the way my oil filter relocation kit aligned it allowed the bracket to be refitted.
I know a lot of people have had no issues removing it but they are often people with track biased cars, ie. a nice smooth driving surface.....

I am a little dubious leaving it off for two reasons;
- firstly, normal roads aren't nearly as smooth as tracks and the leverage of that whole plenum (ie. impulse loading) would be significant over larger bumps and potholes.
- secondly, I don't imagine Mazda engineers would have invested so much material and design into such a large structure for no reason..... :wink:

In the end it's your choice what you do but I would (and did) retain it if at all possible.

sailaholic · Postby **sailaholic** » Sat Jul 05, 2014 11:00 pm

I don't have it but have itbs. Plohl removed his all ok.

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Hellmun · Postby **Hellmun** » Sat Jul 05, 2014 11:04 pm

I removed mine when I installed an oil adapter sandwich plate 3-4 years ago. No ill affects as yet... I couldn't seen any reason to keep it either.

ralt · Postby **ralt** » Sun Jul 06, 2014 1:22 am

Hi.
Mazda would not have put it on for appearance. I believe it is there to absorb engine harmonics. If you have problems getting your filter off you are over tightening it.

KevGoat · Postby **KevGoat** » Sun Jul 06, 2014 2:15 am

I guess it's different with the reroute fitted, but I've never found it that hard to just unbolt that bracket when I need to.

I'm in the camp that it's there for a reason.

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gslender · Postby **gslender** » Sun Jul 06, 2014 8:25 am

Simply cast material is subject to fatigue and cracking. The support bracket is designed to reduce that chance. It will work fine without it, but you increase the risk of it cracking. Much like never flushing brake fluid. Some cars can do 300,000 klms with never having it done and brake fine, but brake fluid is known to absorb water over time, so changing it is subscribed to ensure braking performance is maintained.

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Mr Morlock · Postby **Mr Morlock** » Sun Jul 06, 2014 12:21 pm

Car companies engine designers etc do FMEA's i.e. failure mode effect analysis for designs. The purpose is to identify what may be a potential design fault under certain conditions and they test components and assys against rigorous specs. This can end up with a change to a design for the better. It does not mean that a failure etc happens under all conditions. My view is that its probably there for a good reason. I think gslender said the same thing in a different way.

manga_blue · Postby **manga_blue** » Sun Jul 06, 2014 1:15 pm

Thanks for all the advice. It looks like it's coming off. It's only a minor risk for me since I think I'll only keep this head until the next rebuild in a year or two and then go to BP4W. What FlyinMiata said was "4. Remove the aluminum brace that goes from the intake manifold to the engine block. This may or may not be re-installed, depending on your particular car. We’ve run cars without this brace for years, there’s nothing wrong with removing it altogether."

For those interested in the bigger filter and you want to buy OEM then it's for F-series Mazda engines (Capellas, 626s,Telstars, 929s, B-series, E-series, etc) and the RX2/3/4/5/7 series. All the fittings are identical to the MX5 one except that it's stretched. As an alternative to removal it looks like about 30 mins work to take the bracket out and reshape it with an angle or die grinder to fit a bigger filter.