2.8 (1gd - ftv) high flow muffler

[Brendos 150 Member Find all posts View Profile Close Brendos 150]

Can anyone confirm wheather or not installing a high flow muffler to the stock exhaust will give any really gains in performance. I have read that with the dpf in the 2.8 engine being the biggest restriction in the exhaust a high flow muffler is a wast of time. Is this correct??

[CamJam Senior Member Find all posts View Profile Close CamJam]

Yep, waste of time.

Someone was producing a High-Flow DPF earlier in the year that I heard nothing about since... I imagine it's not possible/ feasible, else they'd make a killing.

[Atherton Senior Member Find all posts View Profile Close Atherton]

I was under the assumption that it's basically a waste of time even on pre 2.8 (and therefore DPF's) vehicles unless you are doing serious performance upgrades (bigger injectors, turbo etc.) The stock ones are designed to work efficiently and all you're going to get with an aftermarket one is a louder car. Not sure how much restriction there is in the DPF. It would be interesting comparing power figures for a car with and without a DFP while leaving the rest of the exhaust system alone. My gut feeling is that the DPF is the problem with restriction and not the rest of the exhaust system. I know that if you're chasing big numbers with higher flow injectors and upgraded turbos it becomes neccessary to replace the exhaust system, but without that it's basically not really acomplishing anything.

[CamJam Senior Member Find all posts View Profile Close CamJam]

Yeah, I hate it when someone just says 'waste of time' like I just did - it doesn't value add.... so -

The highest gain I have seen from a new, full exhaust system is just under 10% - that's a naturally aspirated engine. That's the 'claim' of the retailer, mind you - so you're already you talking, what - perhaps 10Kw or less in the 150? And that's non-DPF. Have a look on line and you can see several manufacturers putting these claimed figures out there - that 10% example is for an NA engine with a swap of headers, extractors and full 3" all the way back, while deleting one of three mufflers in the process.

With the DPF being the most restricted part of the exhaust system (think of a thousand very small straws for your exhaust to go through) then that's the place you'll get any benefit of a more free flowing system. Anything back of that (DPF-Back Exhaust) is rather pointless, as the gain is how freely the exhaust gets out of the combustion chamber. DPF-Back exhaust won't change that. If you have 1000 litres of air that needs to pass through a 2mm hole, then the fact that after the hole it opens up to 3 inches won't change anything for the extraction pre-DPF.

A DPF-delete will, but then you're on your own on so many levels.

[Brendos 150 Member Find all posts View Profile Close Brendos 150]

Yeah, I hate it when someone just says 'waste of time' like I just did - it doesn't value add.... so -

The highest gain I have seen from a new, full exhaust system is just under 10% - that's a naturally aspirated engine. That's the 'claim' of the retailer, mind you - so you're already you talking, what - perhaps 10Kw or less in the 150? And that's non-DPF. Have a look on line and you can see several manufacturers putting these claimed figures out there - that 10% example is for an NA engine with a swap of headers, extractors and full 3" all the way back, while deleting one of three mufflers in the process.

With the DPF being the most restricted part of the exhaust system (think of a thousand very small straws for your exhaust to go through) then that's the place you'll get any benefit of a more free flowing system. Anything back of that (DPF-Back Exhaust) is rather pointless, as the gain is how freely the exhaust gets out of the combustion chamber. DPF-Back exhaust won't change that. If you have 1000 litres of air that needs to pass through a 2mm hole, then the fact that after the hole it opens up to 3 inches won't change anything for the extraction pre-DPF.

A DPF-delete will, but then you're on your own on so many levels.

Thank for your feedback.

I kind of figured the DPF was the biggest restriction on the 2.8. Definitely not interested in gaining noise levels with no real performance increase

[Leethal Advanced Member Find all posts View Profile Close Leethal]

I'm not so sure that the DPF will be the biggest restriction in the exhaust system, I remember years back similar statements about catalyst convertors being the restriction in petrol powered cars.
Then some comparison dyno test results came out for standard cat vs high flow cat vs no cat and there was little if any improvement going to high flow or removing the cat. As I understand it a properly designed cat did not increase restriction. If you think about it the engine/car builder is not going to reduce performance if they can avoid it, yes they minimise cost but they have to develop a DPF anyway so they will get the best result for the money they can. If simply putting a bigger DPF on increased performance then with their buying power it would be a minimal cost if any to do it.
Also consider that the engine is designed for the DPF exhaust system, particularly cyl head design (valves, port shapes etc.) to ensure good scavenging/swirl.

I work for an engine manufacturer and new engines often require a specific exhaust back pressure to perform at their best.

Just my thoughts, Lee

[Brendos 150 Member Find all posts View Profile Close Brendos 150]

I'm not so sure that the DPF will be the biggest restriction in the exhaust system, I remember years back similar statements about catalyst convertors being the restriction in petrol powered cars.
Then some comparison dyno test results came out for standard cat vs high flow cat vs no cat and there was little if any improvement going to high flow or removing the cat. As I understand it a properly designed cat did not increase restriction. If you think about it the engine/car builder is not going to reduce performance if they can avoid it, yes they minimise cost but they have to develop a DPF anyway so they will get the best result for the money they can. If simply putting a bigger DPF on increased performance then with their buying power it would be a minimal cost if any to do it.
Also consider that the engine is designed for the DPF exhaust system, particularly cyl head design (valves, port shapes etc.) to ensure good scavenging/swirl.

I work for an engine manufacturer and new engines often require a specific exhaust back pressure to perform at their best.

Just my thoughts, Lee

Thank Leethal,

I read a thread or two a while back on the pre DPF Prados stating a benefit from changing the muffler to a high flow type, so figured I would put it out there to see everyone’s thoughts.

I would like to think that Toyota would design the vehicles to be as efficient and as powerful as possible to a budget.

Thanks for the response.

Brendan