Aftermarket exhaust manifolds

[Dev]

Well, I went for a swap of standard manifold for a Malian straight through manifold in the end. All went well with operation with all head nuts coming free with studs remaining in the block, and the three amigos played ball although one stud decided to leave with the nut, no problems.
One small issue was the offside O2 sensor wire being a tiny bit too short to reach the connector on the engine block near the dipstick. Resolved by purchasing the rear Denso sensor with the long cable attached.

My question for members, who may have also experienced this, as the original heatshields associated with the original manifold are no longer in place, I wrapped the manifold in titanium wrap to help retain the heat. Despite this the engine bay and engine lid seem to be getting very hot after a "normal" journey (not a spirited drive 😉). Has anyone noticed this and is it or could it become a problem? Hoping its not an issue and am I worrying unduly 🙄?

It can get very hot back there and it is completely normal. The reason why it seems to be very hot is primarily because the exhaust side components are rear facing. With the same engine in the front engine configuration the exhaust header is against the fire wall and the cat under the car where the radiated heat is shielded. Our configuration is better because the area of the fire wall with all of its components and wiring stays cooler because there is no radiator in the engine bay.  When the car is in motion most of that radiated heat goes out the back.
 

Thanks Dev, that's good to hear, I was thinking some heat reflecting insulation above the engine fixed to the engine lid might help?

 There is some kind of insulation on underside of the engine lid. I think its for sound damping. It might have been removed on your car.  I removed mine many years ago and you would think with the amount of heat the paint would get damaged over time but I have no issues. If there was an issue with the heat it would have been reported by now.

 Some people believe adding electronic fans will help but it is an exercise in futility. There is not much you can do with fans when you are dealing with very high temps from exhaust components and are more likely to distribute it to the front of the engine. Just know that Toyota designed this car right and the actual engine has the potential to run cooler than a front engine car but it is all regulated by the ECU and thermostat to be at the correct operational range.
 
 In some other mid-engine configurations having the exhaust up front can create other issues with the hot exhaust pipes up agents coolant, oil and wiring harness lines which we don't have because its all packaged furtherest away from the engine. Very good design especially if you want to turbocharge.

[BARNPOT2000]

Well, I went for a swap of standard manifold for a Malian straight through manifold in the end. All went well with operation with all head nuts coming free with studs remaining in the block, and the three amigos played ball although one stud decided to leave with the nut, no problems.
One small issue was the offside O2 sensor wire being a tiny bit too short to reach the connector on the engine block near the dipstick. Resolved by purchasing the rear Denso sensor with the long cable attached.

My question for members, who may have also experienced this, as the original heatshields associated with the original manifold are no longer in place, I wrapped the manifold in titanium wrap to help retain the heat. Despite this the engine bay and engine lid seem to be getting very hot after a "normal" journey (not a spirited drive 😉). Has anyone noticed this and is it or could it become a problem? Hoping its not an issue and am I worrying unduly 🙄?

It can get very hot back there and it is completely normal. The reason why it seems to be very hot is primarily because the exhaust side components are rear facing. With the same engine in the front engine configuration the exhaust header is against the fire wall and the cat under the car where the radiated heat is shielded. Our configuration is better because the area of the fire wall with all of its components and wiring stays cooler because there is no radiator in the engine bay.  When the car is in motion most of that radiated heat goes out the back.
 

Thanks Dev, that's good to hear, I was thinking some heat reflecting insulation above the engine fixed to the engine lid might help?

 There is some kind of insulation on underside of the engine lid. I think its for sound damping. It might have been removed on your car.  I removed mine many years ago and you would think with the amount of heat the paint would get damaged over time but I have no issues. If there was an issue with the heat it would have been reported by now.

 Some people believe adding electronic fans will help but it is an exercise in futility. There is not much you can do with fans when you are dealing with very high temps from exhaust components and are more likely to distribute it to the front of the engine. Just know that Toyota designed this car right and the actual engine has the potential to run cooler than a front engine car but it is all regulated by the ECU and thermostat to be at the correct operational range.
 
 In some other mid-engine configurations having the exhaust up front can create other issues with the hot exhaust pipes up agents coolant, oil and wiring harness lines which we don't have because its all packaged furtherest away from the engine. Very good design especially if you want to turbocharge.

Yep, still got some insulation under engine lid, reassuring to know it should not be a problem 👍

[BARNPOT2000]

Quick piccy of the finished installation.... You cannot view this attachment.
Took the opportunity to start tarting up the top of the subframe as access was improved during installation of the new header. Actually access to this area of the engine bay is better with the heat shields removed. Possibly a mod to add some more storage space 🤔? Maybe not so good for carrying the ice cream home though 😂.

[Mr2paul]

Maybe a storage space could be made?
Personally I'd use it to heat a curry ready to eat when arriving at work  

[BARNPOT2000]

Maybe a storage space could be made?
Personally I'd use it to heat a curry ready to eat when arriving at work  

Absolutely, baked spuds, bacon, burgers.... the possibilities are endless 😂.

[Ardent]

Did yours not come with the optional Toyota manifold hot plate. Part number 1520-26365
You cannot view this attachment.

[ManInDandism]

Re the O2 sensors.  I've fitted a Zero Exhausts manifold and this came with instructions to replace the standard length offside sensor  (Bank 1 Sensor 1) with a longer one together with selected manufacture's part numbers. 

So for example standard Denso one is DOX-0204 which is 360mm long but says to use DOX-0205 which is 530mm.  Equivalent rear sensor (Bank 1 Sensor 2) on our cars is DOX-0206 and comes in at 850mm which is a bit too long.     

[BARNPOT2000]

Did yours not come with the optional Toyota manifold hot plate. Part number 1520-26365
You cannot view this attachment.

Sadly not 🤔

[BARNPOT2000]

Re the O2 sensors.  I've fitted a Zero Exhausts manifold and this came with instructions to replace the standard length offside sensor  (Bank 1 Sensor 1) with a longer one together with selected manufacture's part numbers. 

So for example standard Denso one is DOX-0204 which is 360mm long but says to use DOX-0205 which is 530mm.  Equivalent rear sensor (Bank 1 Sensor 2) on our cars is DOX-0206 and comes in at 850mm which is a bit too long.     

Useful info... the 0205 sensor would be neater for sure, but the 0206 was only £28 delivered which seemed quite good value 👍.

[BARNPOT2000]

Or keep the stock one. A big dump and a haircut will gain you more performance.

Definitely keeping the stock one... but on a shelf in the workshop to prove it was intact when removed 👍

[Joesson]

Or keep the stock one. A big dump and a haircut will gain you more performance.

Definitely keeping the stock one... but on a shelf in the workshop to prove it was intact when removed 👍

I photographed the intact pre cat honeycomb before removing it and refitting the OE unit. No pre de cat dyno,  no post de cat dyno, but pretty sure it gained me mucho horses!

[Joesson]

😉

[BARNPOT2000]

Can anyone please confirm if the two crush gaskets on the exhaust manifold require exhaust sealing compound or are they tightened up dry please? I used some paste but fear I shouldn't have 🙄.

[Carolyn]

Can anyone please confirm if the two crush gaskets on the exhaust manifold require exhaust sealing compound or are they tightened up dry please? I used some paste but fear I shouldn't have 🙄.

No - you shouldn't have.  Hopefully all will be fine.  Strictly speaking, one should not employ paste upstream of the cat.  But, if it wasn't large dollops, you'll probably be OK. I trust you used OEM spec ones.  The aftermarket ones are poor, I'm afraid.

[Joesson]

Can anyone please confirm if the two crush gaskets on the exhaust manifold require exhaust sealing compound or are they tightened up dry please? I used some paste but fear I shouldn't have 🙄.

The crush gaskets are intended to be used as they come, and my understanding is that they should be used once only, although there have been reports of their being reused. As you have applied an unnecessary sealing compound I suggest that you now leave the joint as it is and be prepared perhaps to spend a little time in cleaning the joint should you need to replace the cat for example.

[BARNPOT2000]

Oops! Well I've removed the cat section and have started to clean up the faces. New gaskets on the way. I've been concerned it hadn't sealed properly and after inspection it may well have been leaking, it certainly didn't sound as sweet as I think it should.

[BARNPOT2000]

Well all done, new genuine Toyota manifold to downpipe gaskets and a new donut gasket at the other end. Soo different, I thought it sounded too noisy, sweet now. Thanks #carolyn, I totally concur that the two genuine toyota gaskets are a must for a great seal below the exhaust manifold. Only about £12 for the pair. I asked the cost of a rear subframe when I collected the gaskets, nearly £400 plus vat. Ouch! Guy at Toyota seemed slightly surprised they were still available but said it was down to supply and demand and the folks like us who want to preserve the marque. But he joked don't wait 20 years to order one as they will cease to be available at some point 😎.

[Joesson]

Well all done, new genuine Toyota manifold to downpipe gaskets and a new donut gasket at the other end. Soo different, I thought it sounded too noisy, sweet now. Thanks #carolyn, I totally concur that the two genuine toyota gaskets are a must for a great seal below the exhaust manifold. Only about £12 for the pair. I asked the cost of a rear subframe when I collected the gaskets, nearly £400 plus vat. Ouch! Guy at Toyota seemed slightly surprised they were still available but said it was down to supply and demand and the folks like us who want to preserve the marque. But he joked don't wait 20 years to order one as they will cease to be available at some point 😎.

Recent posts on here advise that the subframes are available from our affiliate TCB at around £300 all in.

[BARNPOT2000]

Well all done, new genuine Toyota manifold to downpipe gaskets and a new donut gasket at the other end. Soo different, I thought it sounded too noisy, sweet now. Thanks #carolyn, I totally concur that the two genuine toyota gaskets are a must for a great seal below the exhaust manifold. Only about £12 for the pair. I asked the cost of a rear subframe when I collected the gaskets, nearly £400 plus vat. Ouch! Guy at Toyota seemed slightly surprised they were still available but said it was down to supply and demand and the folks like us who want to preserve the marque. But he joked don't wait 20 years to order one as they will cease to be available at some point 😎.

Recent posts on here advise that the subframes are available from our affiliate TCB at around £300 all in.

Just purchased at £264 all in.

[Joesson]

Well all done, new genuine Toyota manifold to downpipe gaskets and a new donut gasket at the other end. Soo different, I thought it sounded too noisy, sweet now. Thanks #carolyn, I totally concur that the two genuine toyota gaskets are a must for a great seal below the exhaust manifold. Only about £12 for the pair. I asked the cost of a rear subframe when I collected the gaskets, nearly £400 plus vat. Ouch! Guy at Toyota seemed slightly surprised they were still available but said it was down to supply and demand and the folks like us who want to preserve the marque. But he joked don't wait 20 years to order one as they will cease to be available at some point 😎.

Recent posts on here advise that the subframes are available from our affiliate TCB at around £300 all in.

Just purchased at £264 all in.

An indicator, if necessary that Main Dealers have to fund the chrome and glass of the new car sales showrooms. Also that it is a Specialist such as Paul at TCB that we should be supporting.

[bobbe]

Hello everyone,

I have a Malian header which arrived today. I realise that it doesn't have anything on the flange at the bottom of the header to attach to the brackets which brace the OEM header to the block. Is this a significant problem? I don't have the capacity to weld anything on to it.

I have the OEM manifold off the car already (it came off surprisingly easy for a 19 year old car!). The precats in it are thankfully in great shape, with no evidence of degredation. Instead of using the Malian header (without the brace, heat shield, etc), is the better option to remove the precats from the OEM manifold and refit it? I have a 3M mask and filters, etc from another job

Either way I have new OEM Toyota gasket and crush rings ready to go

Thanks!

[Carolyn]

Hello everyone,

I have a Malian header which arrived today. I realise that it doesn't have anything on the flange at the bottom of the header to attach to the brackets which brace the OEM header to the block. Is this a significant problem? I don't have the capacity to weld anything on to it.

I have the OEM manifold off the car already (it came off surprisingly easy for a 19 year old car!). The precats in it are thankfully in great shape, with no evidence of degredation. Instead of using the Malian header (without the brace, heat shield, etc), is the better option to remove the precats from the OEM manifold and refit it? I have a 3M mask and filters, etc from another job

Either way I have new OEM Toyota gasket and crush rings ready to go

Thanks!

Welcome!  Please say hello in the new members section. ( https://www.mr2roc.org/forum/index.php?board=75.0 )

Use the Malian one as it is.  It will be fine.

[bobbe]

That's great, thanks!

Please say hello in the new members section. ( https://www.mr2roc.org/forum/index.php?board=75.0 )

I will!

[bobbe]

I have another question, if that's okay - is it safe to use copper grease on the head to header bolts? I know the head is aluminium (which copper doesn't play well with), but presumably the gasket and the header flange would keep the copper grease safely away from it?

[Ardent]

@bobbe

Where in the UK are you based?
We have a meet coming up in September if you are within range.
Stanwick Hotel. Check the events section