Intake manifold upgrades

[m1tch]

Hi all,

I just wanted to start a thread to catalogue my current struggle and hopefully solution to an upgraded intake manifold for the 1zz when going boosted. The stock plastic manifold has a glued in divider which on an NA engine can sometimes start to fail causing a rather annoying and can be fixed using some short screws to hold the divider, fix is documented here:

http://gorup-sinkovec.net/diy/rattling-noise-in-toyota-corolla-intake-manifold-solved/

My issue with the intake manifold divider is that on a boosted application, the boost gets behind the divider which then constantly flexes the composite which then shatters, the divider is located just below the intake runner bell mouths. The composite itself is actually very strong, the stock plastic manifold itself is actually perfectly strong even for higher boost, the issue being is that if/when the divider fails it cracks and shatters into bits rather than just flexing sending chunks into the intake.

Here are the current options I am looking at, will be updating the thread as I find/research more:

Run the stock manifold with the divider and hope it doesn't fail - Free
Import at high cost a modified stock manifold from Monkey Wrench Racing with the divider removed - ~£300
Fit an OEM metal 1zz manifold from a 99-02 Corolla in the US ~£100
Fit a 2zz intake manifold from the Corolla T sport or Celica GTS - unsure as to current costs
Fit a performance manifold from a different engine - unsure as to current costs
Custom intake - big money

OEM plastic intake

Ideally I would love to just run the stock plastic intake but am concerned with protecting my investment I have in the engine currently, the divider is very difficult to remove due to its location within the manifold and limited access. I have cut the top off a spare OEM manifold to find the divider, I might actually be able to remove it and possibly reseal it but not ideal. The stock manifold with the divider removed has made over 500bhp with Monkey Wrench Racing at high boost so might be the final option to import a modified one at high cost as I know it will work and will be safe.

OEM metal 1zz manifold

I have been told that this manifold really doesn't flow well, it has a tiny plenum with small throttlebody and was only meant to go on an engine making around 120bhp, its interesting however as it uses a merge collector with equal length runners to each of the cylinders, this will bolt right onto the engine without issue as its meant for a 1zz. My thoughts are to look to modify the OEM metal manifold as I would need to mod it anyway to fit a decent sized throttlebody. My thoughts with modifying this manifold is to increase the plenum size, might look to do this by cutting a larger hole at the end of the manifold and then bolting a 2.5" or 3" V band flange to the manifold (looking at those 4 bolt to V band adaptors. From this I can then easily attach some pipework to increase the size of the plenum by varying the length of the pipe - I can then attach a throttlebody to one end giving it a straight shot to the runners.

2zz manifold

I have already got a 2zz manifold on the work bench, there are 2 types of 1zz manifold, the 1 piece and the 2 piece, the 1 piece manifold comes off the Celica whereas the 2 piece comes off a Corolla T sport. Apparently the 2 piece flows slightly better than the 1 piece and has the added benefit of being able to be taken apart for clean up and any porting. The runners and plenum of the 2zz manifold are massive, I can see that this manifold will flow well at the top end.

Looking at options to fit the manifold to the engine, a few years ago you could buy an adaptor plate that goes between the 1zz and 2zz, it wasn't cheap as was custom, I think it was actually a 2 piece adapter meaning that it might be ok for engine bays with the intake at the front, not idea for the MR2. I have had a look at the 1zz and 2zz manifold mounting flanges and it would seem that the 1zz mounting points on the head don't interfere with the 2zz runners - this means that I might be able to simply drill additional holes in the 2zz manifold to fit it to the head. I would however need to enlarge and gasket match the 1zz head as the runners are much larger. Speaking with MWR apparently they did run an engine with the 2zz manifold on a 1zz using the adaptor plate mentioned, it apparently lost out low and mid range and about the same at the top end - this is why I am looking into why.

Performance manifold for a different engine

This is an interesting option which I am looking into, there are engines such as the VW 1.8T, Mazda BP05 or the Honda B18 which have many aftermarket options for intake manifolds, I might look into these engines to see if the intake manifold flanges would fit up to the 1zz if the flange was either redrilled or removed and a 1zz flange welded on. I know when I had a BP05 powered Mazda the intake had flaps which allowed for a variable intake length depending on the engine conditions - this would mean I would have a 2 in 1 manifold for low down torque as well as top end flow. There are quite a few options for manifolds, some of the stock B18 manifolds actually flow really well so those might be an option as a starting point - looking at 1.8 engines as those will have the correct flow characteristics.

Fully custom

The final option is the most expensive, going for a custom manifold which would allow me to have the best flow and characteristics but its also the most expensive.

[1979scotte]

For me it's a toss up between MWR and metal stock.
I think I would just pay for the MWR plug and play IF the metal 1zz manifold is as poor as you say.
Adapting stuff can cost more in the end and be massively time consuming

[Call the midlife!]

As Scotte, you're that far into the build now go with the MWR if you're that concerned about the self destructive nature of the standard one.
Plus I imagine there's a reasonable weight increase with the metal one which would negate some of your losses in other areas?


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[jvanzyl]

I have a friend coming over from the US regularly and he's very happy to bring hand luggage over...
Send me a PM if you want to leverage this service.

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[Nvy]

I have a friend coming over from the US regularly and he's very happy to bring hand luggage over...
Send me a PM if you want to leverage this service.

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I might take advantage of your proposal for some goodies over xmass if there are any deals to have from MWR. Id love some pistons and arp bolts Ofc you would have to ship them over to Bulgaria but i dont mind paying shipping UK - BG and ill toss in some monies for beers and stuff for the favor

[m1tch]

I have a friend coming over from the US regularly and he's very happy to bring hand luggage over...
Send me a PM if you want to leverage this service.

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Hmm that might be of interest - although not sure if a manifold would class as hand luggage! The MWR modified intake is $175 plus $75 core charge so $250 all in, I think delivery is something like another $130 on top to the UK and I don't know how much more VAT and Duty will be on top of that!

[m1tch]

I now have the OEM metal 1zz manifold, the throttlebody size is something like 50mm so no wonder it doesn't really flow that well, I am looking into options to simply bore out the opening but leave enough around the edge to be able to then bolt on an adapter plate which can then be used to add additional volume to the plenum and also run a larger throttle body.

So far I can see the metal 1zz manifold has quite a small TB opening, goes into a small plenum and then turns into a 1 to 4 merge collector into individual runners into the head. The 1zz plastic manifold has a slightly larger throttle body opening with a decent sized plenum and bell mouthed runners. The 2zz manifold has a large throttlebody opening, fairly massive plenum and large runners - I can see that the 2zz manifold would flow well up top.

To make the manifolds work for my engine, here are the stages I would need to do for each of them:

OEM 1zz metal manifold

Reweld runners to the back side of the header flange - the runners seem to be welded on the inside of the flange meaning that they actually restrict flow, simply welded or bonding the runners to the other side of the flange and cleaning up the inside of the port will help.

Bore out the current throttlebody opening to allow for a larger bore of throttlebody or a plate to then increase the plenum size

OEM 1zz plastic manifold

I would need to purchase a plastic 1zz manifold from MWR, I might still look at options to remove the divider from the intake myself and then reseal the manifold.

2zz manifold

I would need to measure up and redrill the OEM flange to accept the different 1zz bolt pattern, I would then also need to port out and gasket match the 1zz head, I would be slightly concerned that the 2zz manifold is too large for the engine and only work at the top end.

The current options I am looking at, the 1zz metal manifold will need the more work done to it in terms of modification but will then bolt on, the 1zz plastic manifold will be the most expensive option but should flow well over 500bhp worth and the 2zz manifold doesn't need too much work from a manifold perspective but would need a fair amount of work to the head.