Plastic vs Metal Intake Manifold

This topic has been beaten to death over the years, but I've scoured the forums to find some hard data on the LGT intake manifold performance vs the STI and haven't come up with anything.

I'd like to see full boost as early as possible while still sticking to a decent sized turbo (gtx3071/76r or efr7163/7064 twin scroll). Does anyone know of any back-to-back dyno comparisons between sti and lgt intake manifolds and their effect on spool/torque?

I've found a few discussions, but nothing solid enough to convince me one way or another.

https://forums.nasioc.com/forums/showthread.php?t=2519436&page=1

plastic is best for heat. meal is better for holding high boost. so you just need to determine the pressure limits for the lgt plastic manifold.

There have been plenty of high boost builds using the LGT manifold. The plastic manifold definitely has weight and heat transfer advantages, but there are ways to mitigate the heat soak on the metal manifold (phenolic spacers, water spray, etc.).

I'm more concerned with the effect on the torque curve. The LGT intake runners are longer, smoother and smaller diameter. In theory, this should shift the powerband slightly to the left while not being a significant restriction in the top end. Dom at Maxwell Tuning used to run the plastic manifold on a bunch of his builds, and KillerB motorsports installed it on their shop STi. However, I'm yet to find a solid back-to-back comparison or anything properly data-driven to sway my decision one way or another.

FWIW when speaking with BCP regarding my X500+, they see more power out of the plastic IM. I have an STi IM and Im a bit disappointed with the numbers I put down. Granted, heartbreaker dyno, but comparable builds with a plastic IM are seeing 20-30 more HP and TQE. I plan to turn up the boost and go E85 ASAP to see what the turbo can do. Regarding power with plastic or metal, I can't speak to the plastic IM on this car since I bought it with the STi mani and 3076R.

Regarding powerband, I am also running Kelford 264s which obviously effects the curve. You might want to call over to BCP and see if they have any data showing the difference.

FWIW when speaking with BCP regarding my X500+, they see more power out of the plastic IM. I have an STi IM and Im a bit disappointed with the numbers I put down. Granted, heartbreaker dyno, but comparable builds with a plastic IM are seeing 20-30 more HP and TQE. I plan to turn up the boost and go E85 ASAP to see what the turbo can do. Regarding power with plastic or metal, I can't speak to the plastic IM on this car since I bought it with the STi mani and 3076R.

Regarding powerband, I am also running Kelford 264s which obviously effects the curve. You might want to call over to BCP and see if they have any data showing the difference.

Good to hear more confirmation of the performance benefits. I sent them a message, hopefully they have some solid info!

The debate between the two manifolds was moreso the availability of bigger turbos/wider turbo selection with the STI manifold than the LGT.

There are many ways to run a sti-style turbo, including the grimmspeed TMIC, PW TMIC and almost any variation of FMIC. Regardless, a rotated turbo setup negates all of that and opens up turbo options that won't fit either manifold in the stock location. I'm looking for performance information on the manifold itself.

There are many ways to run a sti-style turbo, including the grimmspeed TMIC, PW TMIC and almost any variation of FMIC. Regardless, a rotated turbo setup negates all of that and opens up turbo options that won't fit either manifold in the stock location. I'm looking for performance information on the manifold itself.

What I'm trying to say is that this was the initial debate between the two manifolds - turbo availability. GS and PW TMIC's only came out in the past 3-4 years, and FMIC-specific to the LGT had different issues with fitment and availability. This issue has been discussed for over a decade now.

What I'm trying to say is that this was the initial debate between the two manifolds - turbo availability. GS and PW TMIC's only came out in the past 3-4 years, and FMIC-specific to the LGT had different issues with fitment and availability. This issue has been discussed for over a decade now.

That's true, however it is not what I'm trying to figure out. Turbo and intercooler selection is not an issue, nor a point of debate for the purpose of this thread.

There are so many other aspects of the build that will affect spool that you won't find any information like this between the plastic and metal intakes.

In general, the plastic intake is superior. This is why Subaru, and most manufacturers, have switched to them. Lighter, smoother, better thermal properties. There is no danger of boost blowing one up either.