Will a ported stock intake manifold cause cylinder 3 to fail?

Hi guys first time poster, I'm in the process of going full bolt on with a custom cst4 sized turbo on stock block and currently have a stock intake manifold that is ported with a vcts delete that i was going to install.
After talking to my tuner and another person in the community that works on mazdaspeeds I was advised that the stock intake manifolds are known to cause cylinder 3 to fail.
I talked to someone else who is knowledgeable in the community about this and he suggested that a stock Manifold would be fine to run for my power goals aslong as I run an aftermarket exhaust manifold. He also said:

"My theory on it is that with the stock exhaust mani, no.3 flows almost twice as much, and the firing order is 1342. I'm wondering with the overlap on exhaust timing whether no.4 actually shoots a flame in the turbo which bounces back into no.3 right before the exhaust valve closes, and causes a stupid amount of heat in the combustion chamber which when the fuel is injected spontaneously combust. Seems to me like the most likely rod bendy scenario to me"

After hearing all this I am considering going for a ford focus st intake manifold instead, but would love to save the money and stick with the ported one I already have if it's not likely to cause me any issues due to the imbalance.

Would love to hear your thoughts thanks!

 

You should look at flow numbers in this thread
https://mazdaspeeds.org/index.php?threads/your-intake-manifold-and-you.1271/#post-8167
A ported intake manifold may not actually sort out flow balance and seems to have a greater % difference.... If you really want to mitigate the effects then yes an after market intake manifold WITH an exhaust manifold is the way to go for flow balance.

Ps you're not FBO unless you have manifolds as well

 

Thank you for that! I think I'll go ahead with an aftermarket intake manifold then, maybe I'll pick up a corksport throttle body along with that... Haha cheers!

 

You're welcome, if you don't already have an exhaust manifold you'd be better off spending your money on one of those than the CS TB, you'd get way more bang for your buck out of it for HP too. Stock TB drives well and flows good too not something I'd even consider myself until north of 700-800hp

 

I already have an XS power v3 manifold for external wastegate with me ready to go in, I was suggested to get a cs throttlebody for a bit more flow while I'm at it, although still deciding on it!
Ps here's my list of mods that'll be on my car for the next tune.
Hpfp stage 1 VIS, HDI gt2 intercooler, 3.5" intake + maf housing, 3" downpipe, 3" catback, XS v3 power exhaust manifold, gfb ex44 external wastegate, 3port boost controller, focus ST intake manifold, sst-x4 turbo ported with xona turbine by scales snails (similar to cst4), (gtr coilpacks maybe..), overspeed injector seals, thermal intake and throttle body gaskets/coolant bypass, 3.5 bar map sensor, solid rear motor mount, passenger side motor mount.

 

Personally I wouldn't worry about the throttle body airflow won't matter for the turbo size and fueling you have, I don't know anything about the gtr coil packs only thing tracking is OEM coil packs as working seen wonky things about non OEM ones

 

Yeah you're right might not be worth it where my car is at. As for gtr coils my tuner in new Zealand has been doing them on a few speeds and running larger gap and seeing great results. But again don't think I'll need them for my power level. If you have any other mods I could do with suggestions would be appreciated!

 

Probably time to look at handling mods, rear sway bar (white line is my go too), solid shifter bushings and the transmission motor mount would make it all solid plus a good set of rubber to put power down. You'll have enough flow power mods to max out stock fueling, I'll always recommend an occ and egr delete (this oke you're doing anyway with the fost manifold) for engine health too if not already on there

 

Thank you for the advice! Will send an update once the cars all tuned

 

Good luck you'll be making some good power

 

This person is correct. #3 fails because of the exhaust manifold, not because of the intake manifold. Now you can tell your tuner, whoever that is, that at least two other forum members told you so.

 

The intake manifold theory always baffled me.

Cyl 1 flows the most and cyl 4 gets the least air (with vtcs closed...which would occur during most peoples low load daily commutes). Meaning cyl 1 would be running lean and 4 rich considering each are getting the same amount of fuel injected. Which would lead to cylinder 1 failure...not 3.

But it's one of those things people ran with and continue to go with over a decade later.

The stock exhaust manifold on the other hand, makes sense.

 

Exhaust before Intake...good to know. There has been more talk about intakes than exhaust manifold for sure.

When looking at a replacement for the OEM exhaust manifold, would one purchase an equal length header or just anything with a longer 3&4 runner? Looking at the stock unit, the 3&4 runners are really short and almost look Siamesed LOL.
Begs the question has anyone done a serious test or comparison of any or all of the units like we have had for intake manifolds?