2nd gen intake manifold on 1st gen?

[Tatsu333]

In this post talking about a Japanese shop's FA24 motor swap into a late-1st-gen (17-20) with the 17-20 ECU, it seems the 2nd gen intake manifold makes a LOT more power (15 hp peak with gains from around 4,250 rpm on up) vs. the red aluminum 1st gen manifold, at least on the FA24.

Might be worth trying on a 1st gen to see if it makes more power without losing a lot of bottom end, or might be a good solution for a centrifugal supercharged or turbo FI build that retains the factory IM.

Looks like a new complete manifold and gasket is $363.28 USD. If similar gains are seen on the FA20, that's about $25 per hp...

Anyone willing to give it a try? I *might* give it a go later in the year when I have some budget available, and after I've got my ACE A350 headers and tune done already.

[norcalpb]

$257 from here:
https://www.subarupartsdeal.com/part...tra2=&filter=()

Strongly considering doing it myself.

[tomm.brz]

Seems cheaper than the useless heatsoaking Red manifold

interested too

[Tatsu333]

To be clear, it almost certainly needs tuning to dial it in, and it most likely will lose some bottom-end / mid-range, but if the top-end gains are similar to those on the FA24, it would be great bang for the buck for those chasing peak HP numbers.

EDIT: do we know if the throttle bodies are the same, or are interchangeable? The article didn't mention it, and that could affect the feasibility / cost of this a lot. I'll try and do some research and add it here.

EDIT 2: OK - from a quick look, it seems the 1st gen plastic manifolds use a similar o-ring type throttle body gasket (P/N 16175AA420) to the 2nd gen (P/N 16175AA570), while the 2017+ manuals with the aluminum manifold use a flat gasket (P/N 16175AA520). The throttle body (P/N 16112AA400) for ALL 1st gen's is the same though, so it will work with both types of gasket, which is good.

However, the part # for the 2nd gen throttle body (P/N 16112AA550) is different from the 1st gen (P/N 16112AA400), as are the gaskets (part #'s above), but it's unclear from the diagrams online whether the throttle plate diameter, bolt pattern, etc. is different.

In the original article's pictures, it's clear that they have the FA24's throttle body on the FA24 manifold, because the FA20 one has the vacuum port at the top (with no vacuum line connected in this photo) and in the photo with the FA24 manifold installed, it's not there, so definitely different.

Since even if the o-ring type gaskets are the same size we don't know if the bolt pattern is the same between the 1st gen and 2nd gen, it's unclear whether this will work.

Someone will have to buy and try I guess...or bring a 2017+ aluminum manifold gasket to a wrecker with a 2022+ and see if it matches up to the throttle body bolt holes? This presumes they'd let you test fitment.

Since the bolt pattern looks square on both in the diagrams, I guess if we could get a centre-to-centre (center-to-center for the Americans ) measurement off both, even installed, that should give us a good idea.

EDIT: a local tuner I know has a GR86 and is willing to check the measurements on the TB for me to see if they're interchangeable. I'll report back here when I hear back.

[EndlessAzure]

I'm not that surprised that a Gen1 intake manifold would do worse on a Gen2 block. It isn't meant for that block and probably not designed to flow properly.



I'm not convinced that a Gen2 intake manifold just being larger will net you many gains for NA application



If anything is to be gleaned, look for all those ITB development threads on Gen1; that should temper your expectations

[soundman98]

how much larger is a bigger question.

i suspect the overall size isn't going to be much larger than the power blocks mod. just look at what those do to the dyno curve-- any increase in intake length is just going to exacerbate the same qualities.

[tomm.brz]

Originally Posted by EndlessAzure

I'm not that surprised that a Gen1 intake manifold would do worse on a Gen2 block. It isn't meant for that block and probably not designed to flow properly.



I'm not convinced that a Gen2 intake manifold just being larger will net you many gains for NA application



If anything is to be gleaned, look for all those ITB development threads on Gen1; that should temper your expectations

well to each his own thought
You very well can be right, buti think the opposite of you, i think a plenum helps this car more.
and when you play with this car that has just 1 afr sensor, not even so precise, and cam timing are slow responding and imprecise too, empiric tries can put out things no one expected.. we already saw this with exhaust manifold... some work excellent, some give only problems and change a lot the torque production
I guess we'll see what happens with that manifold in gen1 cars, i m sure someone will try

[Tatsu333]

Originally Posted by EndlessAzure

I'm not that surprised that a Gen1 intake manifold would do worse on a Gen2 block. It isn't meant for that block and probably not designed to flow properly.

I'm not convinced that a Gen2 intake manifold just being larger will net you many gains for NA application

If anything is to be gleaned, look for all those ITB development threads on Gen1; that should temper your expectations

ITB's are not a valid comparison. If anything they usually drastically shorten the runner length, and also come along with a host of other compromises / issues that make them problematic in a street-driven application.

Absolutely, it makes sense that a manifold designed for a 2.0L motor would perform worse than the OEM manifold on a 2.4L - that is not surprising. The magnitude of the difference, and the visual of how much longer and larger the runners are what is interesting, and there is a *possibility* that the FA24 manifold could make more power on the FA20.

It's well established (and confirmed with my own dyno testing as talked about in this thread) that the Power Blocks (which effectively lengthen the intake manifold runners) make more power everywhere in an FA20 NA application except at the very top of the power band.

The added plenum and runner volume that is apparent in the visual comparison of the two manifolds *could* help with that lack of power in the top end. Again, I have first-hand experience with a similar change (larger plenum and intake manifold runners) doing exactly that, albeit on a vastly different platform with my previous car.

For those reasons, I think it's likely that there will be gains at the top end. What remains to be seen is how much of a gain, and how much, if any, low to mid-range torque / power will be lost.

Originally Posted by soundman98

how much larger is a bigger question.

i suspect the overall size isn't going to be much larger than the power blocks mod. just look at what those do to the dyno curve-- any increase in intake length is just going to exacerbate the same qualities.

I totally agree that the overall length is unlikely to be much (if at all) longer than the FA20 manifold with the Power Blocks - there just isn't really room to make them much longer.

However, as I noted above, the added plenum and runner volume that is apparent in the visual comparison of the two manifolds *could* help with the lack of power in the top end that happens with the Power Blocks and balance out "what those do to the dyno curve", but whether the resulting loss of velocity from the increased volume would result in too much torque / power loss in the low to mid-range on an FA20 remains to be seen (the 20% increased displacement on the FA24 pretty much negates that concern).

For me, it's interesting enough and relatively inexpensive enough (presuming the throttle bodies are interchangeable) that I'm certainly willing to give it a go to see if the potential is real.

[PulsarBeeerz]

I'm surprised the intake ports on the FA24 aren't physically larger or of different shape to the FA20.

[Tatsu333]

Originally Posted by PulsarBeeerz

I'm surprised the intake ports on the FA24 aren't physically larger or of different shape to the FA20.

They very well could be larger - the intake manifold gasket is a different part number (14001AC680 for FA24 vs. 14035AA610 for FA20), but they do look to be similar shape.

I do seem to remember reading somewhere that they were the same size though, but can't remember exactly where.

With the side-by-side picture having the ports on the FA20 manifold covered with masking tape, it's impossible to see, but it would be hard to eyeball it anyway.

[norcalpb]

Originally Posted by Tatsu333

They very well could be larger - the intake manifold gasket is a different part number (14001AC680 for FA24 vs. 14035AA610 for FA20), but they do look to be similar shape.

I do seem to remember reading somewhere that they were the same size though, but can't remember exactly where.

With the side-by-side picture having the ports on the FA20 manifold covered with masking tape, it's impossible to see, but it would be hard to eyeball it anyway.

Do we know if the FA20 fuel rails can be transferred over to the new manifold?

[Tatsu333]

According to this Toyota UK press pack on the GR86, the FA24D has a larger diameter throttle body, so I don't think it will be possible to use the 2nd gen manifold on the 1st gen without it, which then makes this a very expensive proposition and definitely not worth doing.

Oh, well - I'll just stick with my Power Blocks!