GR86 Exhaust manifolds

There's a fella who posted in the exhausts thread a while ago about installing a decat manifold, but he isn't in the UK. He says it's the best thing he's done to the car. It'll need mapping to clear any CEL though. People in the US claim to have used defoulers, (O2 sensor spacers) to avoid the CEL.

Something potentially very important, which our friend from the previously mentioned post in the exhaust thread pointed out; it seems eu (and I would assume UK) specced cars have an exhaust temp sensor. There is VERY LITTLE about this on any forums as I think we're the only English speaking country that has It on our cars. There is a mention of it on the cobra exhausts page, where they mention that their decat manifold doesn't have a port for it.
This put me off ordering a JDL catted header from the states.

I have searched high and low for a catted manifold with all of the appropriate ports, even messaging some suppliers, including Fensport, all of which said they don't currently have a product that is catted and has an EGT sensor port.

Please bear in mind that I haven't taken off my undertray and looked for myself. This is just what I've found online.

Please keep us posted with any progress you find during your search

Sonic said:

Removing the Primary Cat at the header is technically illegal (see regulations regarding tampering with emission systems). You can install a Sports Cat at the Primary location though - Inserting a replacement 200cel Sports Cat for example, is both legal and will pass an MOT. Retaining your Warranty is a completely different matter...

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Very good points made here, and anyone considering going de-cat or 200 cell sports cat should give careful thought to the potential ramifications here with your Totoya warranty. I would recommend a conversation with your Toyota servicing dealer to ascertain their position on whether they would continue to support you re warranty. Another thing to consider, and I'm not speaking on this point from first hand experience as we only offer a front pipe back system for GR86 at present. Some of you may know the answer to this, would a de-cat and GPF delete cause any EML/CEL dash warns, same goes for 200 cell Sports cat.

In addition, certainly to get the full potential out of a turbo back exhaust upgrade, with either de-cat or 200 cell, it's a remap. I suspect remapping the OEM ECU is likely to be an issue to the majority of UK Toyota dealers, but they 'may' still agree warranty claims on the vehicle for non engine related issues. They would find it very difficult to refuse a warranty claim on a defective headlamp for example, based on an ECU remap.

I do like the look of the hks catted manifold, am i right in thinking the gpf sits between the manifold and the cat back exhaust location, in whats normally called the overpipe?

Swizzle said:

I do like the look of the hks catted manifold, am i right in thinking the gpf sits between the manifold and the cat back exhaust location, in whats normally called the overpipe?

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It is between them. It goes: catted manifold > overripe > front/mid pipe (contains gpf and resonator) > cat back exhaust

so even with a better manifold / high flow cat you’ve still got the overpipe and the gpf pipe in there holding the flow up

GRistopher said:

It is between them. It goes: catted manifold > overripe > front/mid pipe (contains gpf and resonator) > cat back exhaust

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Is it where the second cat was on the GT86?

For everyone's information, my BRZ just went through its first mandatory MOT test (it will be 3 years old in May). Despite having both the HKS catted EL header and catted front pipe, emissions were very marginal, so be warned that using the two HKS cats is not as effective as in my old BRZ where I kept the 2nd OEM cat in place. I somehow doubt the claim that they pass Japanese emissions testing and they would certainly not pass more strict controls in the likes of California or Germany.

Hmm interesting. Had you warmed them up first?

MartinT said:

For everyone's information, my BRZ just went through its first mandatory MOT test (it will be 3 years old in May). Despite having both the HKS catted EL header and catted front pipe, emissions were very marginal, so be warned that using the two HKS cats is not as effective as in my old BRZ where I kept the 2nd OEM cat in place. I somehow doubt the claim that they pass Japanese emissions testing and they would certainly not pass more strict controls in the likes of California or Germany.

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Is the HKS front pipe not just resonated (without a cat)?

Ive been looking at the remainder of the exhaust system on mine this last week and wondering if itll pass MOT, good to know the manifold doesnt cause issues as its visible from the engine bay. I thought it might fail for exhaust tampering with the new MOT test requirements.

GRistopher said:

Hmm interesting. Had you warmed them up first?

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Takes me back about 20 years! My then girlfriend’s ~ 5 year old hot hatch somehow failed its second year MOT on emissions. Cat still in situ and the only mod was a stainless catback. The failure prompted a small meltdown on her part and panic that she’d need to swap out the exhaust etc. suffice to say a 30 minute utter kicking (thankfully not with her in the car) was dished out by me and it passed without issue