Replacement Cat and back box

[Dev]

 The major bottle neck is the catalytic converter/downpipe. The OEM one is very restrictive. Its not just the resistance of the cat its the diameter of the pipes where it bifurcates from two tubes to one. The OEM tubes in the flex section has welded in chokes that narrows the diameter to 1"! Chokes are usually put into exhausts for sound restriction.  When you get a properly sized downpipe that relieves this restriction the car can pickup anywhere from 5-8hp and improvement in torque across the rev band and there is economy benefits also. This was calculated long ago on a dyno however the owners that had them said it felt like more than the dyno figures indicated probably because most performance claims do not live up to their real figures.

A less restrictive muffler can help but not by the same amount however its benefits are in weight reduction. 
Not all aftermarket downpipes are the same, if you get a cheap replacement one it might not give you much but be warned if you get one that is less restrictive it can get really loud and that is why you would want a quiet muffler.

[Zspeed]

Thanks @Dev ,
so would you say as it's my cat flexis that are bust and I'm looking to see what is worth upgrading, my money is best spent on a pipe like this and even a stock muffler would be fine for now? I have found a reasonably priced custom muffler from a turbo but I have a feeling it's loud as the box is small.

[Iain]

That looks like the zero sports cat.

I dont want it too loud but i do want a bit of noise so my plan is to run the sports cat and keep the oem muffler.

[Zspeed]

That looks like the zero sports cat.

I dont want it too loud but i do want a bit of noise so my plan is to run the sports cat and keep the oem muffler.

It is! I just assumed that dev probably has not seen this particular one as he is state side.

I thought there might be a go to solution or three for effective exhaust systems if there is any more power achievable but seems to be a lot of claims.

I have always been a bit dubious on back box claims as I have never seen anyone with dyno figures to qualify it. Years ago, in my youth, people used to pay a fortune for complete systems but no one ever said it was necessary, they just seemed to have so much money to spend it was just part of what they did.

If there is something to gain with one of these as my cat Is broke I might as well do it now, and maybe a
Back box while I'm at it. Not bothered about sound as long as not too loud, if it does the job and is silent all the better. I'll quite happily by a second hand stock box like you but if a better one is available for £50 more I better get that to 😆

[Dev]

That looks like the zero sports cat.

I dont want it too loud but i do want a bit of noise so my plan is to run the sports cat and keep the oem muffler.

It is! I just assumed that dev probably has not seen this particular one as he is state side.

I thought there might be a go to solution or three for effective exhaust systems if there is any more power achievable but seems to be a lot of claims.

I have always been a bit dubious on back box claims as I have never seen anyone with dyno figures to qualify it. Years ago, in my youth, people used to pay a fortune for complete systems but no one ever said it was necessary, they just seemed to have so much money to spend it was just part of what they did.

If there is something to gain with one of these as my cat Is broke I might as well do it now, and maybe a
Back box while I'm at it. Not bothered about sound as long as not too loud, if it does the job and is silent all the better. I'll quite happily by a second hand stock box like you but if a better one is available for £50 more I better get that to 😆

The picture you posted is probably the best one. If you notice the primary collector is not restricted. If you see the OEM there is a major restriction at the collector and the tube diameter is too small. 

 I am aware of the Zero downpipe posted here and it is in my opinion the best one. I have something similar of lesser quality that comes from China. The Chinese version doesn't have a place for the ring gaskets to stay in place on the header side and it doesn't have the pipe extended slightly for the muffler side.
 I had to modify mine because it was leaky but I got it to work and it was cheap.

 There was a downpipe made long ago that has larger tubes that had all of these features the Zero has. I had it for a brief time and it produced power but it was way too loud so I had to sell it. 

 For the 1ZZ it does make power but for the 2ZZ it makes even more power because you should not use the OEM downpipe for the 2ZZ but many do. 

[Dev]

That looks like the zero sports cat.

I dont want it too loud but i do want a bit of noise so my plan is to run the sports cat and keep the oem muffler.

 Actually that is what some do or they use a quieter sports exhaust that is lighter. If you have a 2ZZ its even louder, not at idle but going into lift but it sounds like a Tubistyle exhaust. 

[Zspeed]

That looks like the zero sports cat.

I dont want it too loud but i do want a bit of noise so my plan is to run the sports cat and keep the oem muffler.

 Actually that is what some do or they use a quieter sports exhaust that is lighter. If you have a 2ZZ its even louder, not at idle but going into lift but it sounds like a Tubistyle exhaust. 

This is all good stuff and exactly what I was hoping for. Look forward to the dyno results but I might just get on and order one now.

[Dev]

That looks like the zero sports cat.

I dont want it too loud but i do want a bit of noise so my plan is to run the sports cat and keep the oem muffler.

 Actually that is what some do or they use a quieter sports exhaust that is lighter. If you have a 2ZZ its even louder, not at idle but going into lift but it sounds like a Tubistyle exhaust. 

This is all good stuff and exactly what I was hoping for. Look forward to the dyno results but I might just get on and order one now.

 I do not know how inflation is effecting your country but over here its taking hold especially raw materials. I would get it before there is a dramatic price increase or the lack of availably. I have seen some price increases in mufflers. 

[Zspeed]

[/quote]

 I do not know how inflation is effecting your country but over here its taking hold especially raw materials. I would get it before there is a dramatic price increase or the lack of availably. I have seen some price increases in mufflers. 





[/quote]

Very much so with warnings of more to come. My trade (fishing tackle) has seen big increases mainly due to shipping from the east but also anything with a high metal content has seen additional increases or even quite simply much longer lead times introduced (months).

[Dev]

 I do not know how inflation is effecting your country but over here its taking hold especially raw materials. I would get it before there is a dramatic price increase or the lack of availably. I have seen some price increases in mufflers. 





[/quote]

Very much so with warnings of more to come. My trade (fishing tackle) has seen big increases mainly due to shipping from the east but also anything with a high metal content has seen additional increases or even quite simply much longer lead times introduced (months).
[/quote]

Its getting crazy. Time to sell off things I no longer use and consolidate them into wise future purchases before they dramatically go up in price. 
 

[Alex Knight]

Here it is @Alex Knight .  To be fair the rest looks really good.

As long as it's structurally sound, it should be ok.

If it were me though, I'd be importing a better quality one from Japan.

[Zspeed]

Here it is @Alex Knight .  To be fair the rest looks really good.

As long as it's structurally sound, it should be ok.

If it were me though, I'd be importing a better quality one from Japan.

Is 'jauce' the Japanese bidding site you are referring to? Found one on there like new for less then £300 but shipping will be expensive I guess

[Alex Knight]

Here it is @Alex Knight .  To be fair the rest looks really good.

As long as it's structurally sound, it should be ok.

If it were me though, I'd be importing a better quality one from Japan.

Is 'jauce' the Japanese bidding site you are referring to? Found one on there like new for less then £300 but shipping will be expensive I guess

I normally browse Yahoo Auctions JP, then use Jesse Streeter as an import agent, he is very good and I've been using him for years.

https://jessestreeter.com/ordering-parts/

Yes, the parts are more expensive that way, but over the years I've found that generally if you buy cheap, you buy twice. Then it's not cheap at all!

[Zspeed]

Here it is @Alex Knight .  To be fair the rest looks really good.

As long as it's structurally sound, it should be ok.

If it were me though, I'd be importing a better quality one from Japan.

Is 'jauce' the Japanese bidding site you are referring to? Found one on there like new for less then £300 but shipping will be expensive I guess

I normally browse Yahoo Auctions JP, then use Jesse Streeter as an import agent, he is very good and I've been using him for years.

https://jessestreeter.com/ordering-parts/

Yes, the parts are more expensive that way, but over the years I've found that generally if you buy cheap, you buy twice. Then it's not cheap at all!

That's great, thanks for your help.  I can see the parts on there appear to be in much better conditions than those generally available here. I will be some searching now.

[Zspeed]

Anyone recognise this back box design with the pipe coming back?

Apparently tail pipe is 4 inches.

[Zspeed]

Yes they are made to order, I think it was about 3 weeks.

@Mikeymead what sort of back box do you run with yours?

[Mikeymead]

Yes they are made to order, I think it was about 3 weeks.

@Mikeymead what sort of back box do you run with yours?

I'm running a Blitz Nurspec, bought second hand and also a very good fit.

[Zspeed]

Add in the slight power gains, less weight and more sound its a good buy.

Id like to change the back box but there are limited options and i may custom build my own in time.

Agree with your post about quality. The Cats2u one works and is fine for day-to-day, but top quality it's not.
Tomaky was telling me he had to replace his after 3 years.

With the bit in bold above though, do you have evidence? I can't see how you'd get it as we have a post-cat sensor which gets the ECU learning.

There's lots of noise on the forum that this mod or that mod adds extra power, but the only people documented running more than 140bhp on a NA 1zz have spent a lot of money getting it.

I have no evidence no, just past knowledge of messing with many different cars for years.

Dont get me wrong, its not much power it frees up and i totally understand people who say it makes no difference, we all have our opinions.

But to me, a more free flowing exhaust, whether it be headers, sports cat or back box will release some power.

I felt the car had a tad more low-mid range power when i fitted the stainless manifold.

Not sure what you mean about the ecu learning, new to me that.

Also if there was no gains to be had, most of the runners in the mr2 championship are wasting there money.

I will be going on a dyno before long (just for giggles and ive never done it) so will see if theres any difference to be had, im interested to see the results.


@Zspeed the cat was £320.

Have you got your cat pipe yet? Spoke to Kevin today to order mine but he is waiting on the cats themselves. Apparently magnaflow is struggling to produce due to material shortages. He said he has sourced the same spec cat from a UK supplier though that he is even happier with so will start building next week.

I also spoke to someone today who said their car is running at about 160bhp with an complete exhaust change, air filter and a couple of other cheap mods which I hope to clarify soon. Feeling optimistic for some extra oomph for little money.

[Ardent]

I also spoke to someone today who said their car is running at about 160bhp with an complete exhaust change, air filter and a couple of other cheap mods which I hope to clarify soon. Feeling optimistic for some extra oomph for little money.

We are all ears and looking forward to hearing what the combo is.
Muchos time, effort and experimentation has been carried out re intakes. Conclusion. On a stock car. Stock is best.
That said, everyday is a school day.

[Zspeed]

I also spoke to someone today who said their car is running at about 160bhp with an complete exhaust change, air filter and a couple of other cheap mods which I hope to clarify soon. Feeling optimistic for some extra oomph for little money.

We are all ears and looking forward to hearing what the combo is.
Muchos time, effort and experimentation has been carried out re intakes. Conclusion. On a stock car. Stock is best.
That said, everyday is a school day.

I have to say I was shocked to. I will be pushing hard on this as i have been told it's rather cheap for the results. It's as much as I would want and would be great if reliable.

[Iain]

[/quote]

Have you got your cat pipe yet? Spoke to Kevin today to order mine but he is waiting on the cats themselves. Apparently magnaflow is struggling to produce due to material shortages. He said he has sourced the same spec cat from a UK supplier though that he is even happier with so will start building next week.

I also spoke to someone today who said their car is running at about 160bhp with an complete exhaust change, air filter and a couple of other cheap mods which I hope to clarify soon. Feeling optimistic for some extra oomph for little money.
[/quote]

No not recieved it yet. Kevin did say it was going to be a good couple of weeks and i ordered it on 13/07 so id hope to hear from him next week.

[1979scotte]

Add in the slight power gains, less weight and more sound its a good buy.

Id like to change the back box but there are limited options and i may custom build my own in time.

Agree with your post about quality. The Cats2u one works and is fine for day-to-day, but top quality it's not.
Tomaky was telling me he had to replace his after 3 years.

With the bit in bold above though, do you have evidence? I can't see how you'd get it as we have a post-cat sensor which gets the ECU learning.

There's lots of noise on the forum that this mod or that mod adds extra power, but the only people documented running more than 140bhp on a NA 1zz have spent a lot of money getting it.

I have no evidence no, just past knowledge of messing with many different cars for years.

Dont get me wrong, its not much power it frees up and i totally understand people who say it makes no difference, we all have our opinions.

But to me, a more free flowing exhaust, whether it be headers, sports cat or back box will release some power.

I felt the car had a tad more low-mid range power when i fitted the stainless manifold.

Not sure what you mean about the ecu learning, new to me that.

Also if there was no gains to be had, most of the runners in the mr2 championship are wasting there money.

I will be going on a dyno before long (just for giggles and ive never done it) so will see if theres any difference to be had, im interested to see the results.


@Zspeed the cat was £320.

Have you got your cat pipe yet? Spoke to Kevin today to order mine but he is waiting on the cats themselves. Apparently magnaflow is struggling to produce due to material shortages. He said he has sourced the same spec cat from a UK supplier though that he is even happier with so will start building next week.

I also spoke to someone today who said their car is running at about 160bhp with an complete exhaust change, air filter and a couple of other cheap mods which I hope to clarify soon. Feeling optimistic for some extra oomph for little money.

Who said that?
Do they have before and after dyno charts?
Find that very hard to believe we've got members running full stand alone ecu with fully rebuilt engines that only get 50 bhp max over stock.
The only way to make good power NA on a 1zz is to spend big otherwise just go turbo or 2zz.

[Zspeed]

Add in the slight power gains, less weight and more sound its a good buy.

Id like to change the back box but there are limited options and i may custom build my own in time.

Agree with your post about quality. The Cats2u one works and is fine for day-to-day, but top quality it's not.
Tomaky was telling me he had to replace his after 3 years.

With the bit in bold above though, do you have evidence? I can't see how you'd get it as we have a post-cat sensor which gets the ECU learning.

There's lots of noise on the forum that this mod or that mod adds extra power, but the only people documented running more than 140bhp on a NA 1zz have spent a lot of money getting it.

I have no evidence no, just past knowledge of messing with many different cars for years.

Dont get me wrong, its not much power it frees up and i totally understand people who say it makes no difference, we all have our opinions.

But to me, a more free flowing exhaust, whether it be headers, sports cat or back box will release some power.

I felt the car had a tad more low-mid range power when i fitted the stainless manifold.

Not sure what you mean about the ecu learning, new to me that.

Also if there was no gains to be had, most of the runners in the mr2 championship are wasting there money.

I will be going on a dyno before long (just for giggles and ive never done it) so will see if theres any difference to be had, im interested to see the results.


@Zspeed the cat was £320.

Have you got your cat pipe yet? Spoke to Kevin today to order mine but he is waiting on the cats themselves. Apparently magnaflow is struggling to produce due to material shortages. He said he has sourced the same spec cat from a UK supplier though that he is even happier with so will start building next week.

I also spoke to someone today who said their car is running at about 160bhp with an complete exhaust change, air filter and a couple of other cheap mods which I hope to clarify soon. Feeling optimistic for some extra oomph for little money.

Who said that?
Do they have before and after dyno charts?
Find that very hard to believe we've got members running full stand alone ecu with fully rebuilt engines that only get 50 bhp max over stock.
The only way to make good power NA on a 1zz is to spend big otherwise just go turbo or 2zz.

I will let you know when I have gone through it. Might take a while, they will be quite protective and rightly so.  I will certainly dyno mine if it feel it has worked. I will let you know if it is rubbish to.

[shnazzle]

Add in the slight power gains, less weight and more sound its a good buy.

Id like to change the back box but there are limited options and i may custom build my own in time.

Agree with your post about quality. The Cats2u one works and is fine for day-to-day, but top quality it's not.
Tomaky was telling me he had to replace his after 3 years.

With the bit in bold above though, do you have evidence? I can't see how you'd get it as we have a post-cat sensor which gets the ECU learning.

There's lots of noise on the forum that this mod or that mod adds extra power, but the only people documented running more than 140bhp on a NA 1zz have spent a lot of money getting it.

I have no evidence no, just past knowledge of messing with many different cars for years.

Dont get me wrong, its not much power it frees up and i totally understand people who say it makes no difference, we all have our opinions.

But to me, a more free flowing exhaust, whether it be headers, sports cat or back box will release some power.

I felt the car had a tad more low-mid range power when i fitted the stainless manifold.

Not sure what you mean about the ecu learning, new to me that.

Also if there was no gains to be had, most of the runners in the mr2 championship are wasting there money.

I will be going on a dyno before long (just for giggles and ive never done it) so will see if theres any difference to be had, im interested to see the results.


@Zspeed the cat was £320.

Have you got your cat pipe yet? Spoke to Kevin today to order mine but he is waiting on the cats themselves. Apparently magnaflow is struggling to produce due to material shortages. He said he has sourced the same spec cat from a UK supplier though that he is even happier with so will start building next week.

I also spoke to someone today who said their car is running at about 160bhp with an complete exhaust change, air filter and a couple of other cheap mods which I hope to clarify soon. Feeling optimistic for some extra oomph for little money.

Who said that?
Do they have before and after dyno charts?
Find that very hard to believe we've got members running full stand alone ecu with fully rebuilt engines that only get 50 bhp max over stock.
The only way to make good power NA on a 1zz is to spend big otherwise just go turbo or 2zz.

I will let you know when I have gone through it. Might take a while, they will be quite protective and rightly so.  I will certainly dyno mine if it feel it has worked. I will let you know if it is rubbish to.

That'd be good.

Remember you need a pre and post. Just the post-mod dyno leaves a lot of questions.

[Dev]

There is a lot of fraud with dyno numbers. The operator is able to skew the results to make the customer happy even if they bring in their own parts. There are only a few dyno machines that actually show actual wheel horsepower and the numbers are always disappointing.  As Shnazzle mentioned you need to do a pre and post to compare the difference between mods and it should be along the entire RPM band and not peak. A difference of +or- 5hp is usually inconclusive unless it is repeatable for at least two runs each.   

 It is down right hilarious when some 1ZZ owners claim their car with bolt ons is just as fast as a 2ZZ. The only 1ZZ that shows similar power figures is a fully built and blueprinted MWR 1ZZ which costs a small fortune.
 A real +8hp gain is huge for this car NA.