non-US market OEM 4-2-1 exhaust
08-20-2016, 11:50 PM
#1
Junior Member
Thread Starter
iTrader: (9)
Join Date: Dec 2011
Location: SFBay
Posts: 408
Total Cats: 61
non-US market OEM 4-2-1 exhaust
I am selling my UKDM 4-2-1 exhaust system.
It's generally held to be an improvement over the USDM 4-1 while maintaining the OEM look needed for smog:
It includes the 4-2, the 2-1, the heatshield, as well as the block-to-head gasket and gasket between the two parts.
If you want to replace the gasket between the two halves, it's Mazda part F20140306. It uses the same EGR tube as the US NB2.
I removed the studs from the header to clean the surface and could only find 2/3
It's the same stud as the NB2 exhaust as well as a number of other Mazdas and I'll include the ones I found.
The front O2 sensor is in the crossover section and on a CA-spec NB1 it doesn't require an extension.
Asking $280 shipped.
It's generally held to be an improvement over the USDM 4-1 while maintaining the OEM look needed for smog:
We did some A/B testing with the EUDM exhaust manifold last year, stock NB2 airbox. I can't find/identify the dynos but the approximate numbers were something like:
~127whp USDM tubular 4:1 & DP
~133whp EUDM tubular 4:2:1 & DP
~139whp RB 56006 header (NA chassis)
We then deleted the MAF and wrapped a KN 69-6000TP intake with thermal wrap for another 9whp-ish.
So the EUDM header is nice you need to appear emissions legal. If not, the RB is still a much more cost effective power adder.
~127whp USDM tubular 4:1 & DP
~133whp EUDM tubular 4:2:1 & DP
~139whp RB 56006 header (NA chassis)
We then deleted the MAF and wrapped a KN 69-6000TP intake with thermal wrap for another 9whp-ish.
So the EUDM header is nice you need to appear emissions legal. If not, the RB is still a much more cost effective power adder.
If you want to replace the gasket between the two halves, it's Mazda part F20140306. It uses the same EGR tube as the US NB2.
I removed the studs from the header to clean the surface and could only find 2/3
It's the same stud as the NB2 exhaust as well as a number of other Mazdas and I'll include the ones I found.The front O2 sensor is in the crossover section and on a CA-spec NB1 it doesn't require an extension.
Asking $280 shipped.
Last edited by scenturion; 08-30-2016 at 12:01 PM.
Reply
0
0
08-22-2016, 12:26 AM
#4
Junior Member
Thread Starter
iTrader: (9)
Join Date: Dec 2011
Location: SFBay
Posts: 408
Total Cats: 61
People should feel free to make offers!
Reply
0
0
08-26-2016, 05:13 PM
#10
I smogged my car with this header on my car. However, you are deleting the first "light off" cat, henceforth referred to as , (essential in startup emissions but not tested in your semi annual smog check). If you're second is in marginal health, having both s in the system might be the difference between passing and failing.
A couple notes on install. You're CA car has two o2 sensors. You're first sensor is between the exhaust ports and before the 1st . The second is between the 1st and 2nd . Since you are removing the first you will need to add a bung behind the second and install O2 #2 there and put O2 #1 in the new 4-2-1 header. The O2 sensors wires will likely need to be extended if I remember correctly.
Also, I'm not sure if the CARB EO for the CA miata states that it has two but if it does and the smog technician actually checks it (not too likely) they can fail you for visual. But since it looks and is OEM you should be fine on that visual.
, (essential in startup emissions but not tested in your semi annual smog check). If you're second is in marginal health, having both s in the system might be the difference between passing and failing.A couple notes on install. You're CA car has two o2 sensors. You're first sensor is between the exhaust ports and before the 1st
. The second is between the 1st and 2nd . Since you are removing the first you will need to add a bung behind the second and install O2 #2 there and put O2 #1 in the new 4-2-1 header. The O2 sensors wires will likely need to be extended if I remember correctly.Also, I'm not sure if the CARB EO for the CA miata states that it has two
but if it does and the smog technician actually checks it (not too likely) they can fail you for visual. But since it looks and is OEM you should be fine on that visual.
Reply
1
1
well i might just have to look into this but im not ready to put down the money yet 
let me sleep on it
08-30-2016, 02:09 AM
#13
Junior Member
Join Date: Nov 2012
Location: SF Bay Area
Posts: 58
Total Cats: 0
Assuming your car is running properly and your main cat is healthy, you shouldn't have a problem passing sniffer with no precat, though I can't say that I've tried.
I'd slap one of these on to my car if I was bringing it back to stock, though. I won't be doing that for a while though (fingers crossed). GLWS
Reply
0
0
08-30-2016, 07:19 AM
#14
Junior Member
Join Date: Nov 2012
Location: Netherlands, Europe
Posts: 204
Total Cats: 29
I have two of these headers on my scrap bin from the two NBs I stripped, ready to be thrown away.
They are incredible heavy and I have a stainless steel 4-2-1 which I bought for 50€ ready to go on my NB once it is fixed.
Shipping them from Europe to US costs probably around 100$, so I am not sure they are worth their shipping cost?
They are incredible heavy and I have a stainless steel 4-2-1 which I bought for 50€ ready to go on my NB once it is fixed.
Shipping them from Europe to US costs probably around 100$, so I am not sure they are worth their shipping cost?
Reply
0
0
08-30-2016, 12:00 PM
#15
Junior Member
Thread Starter
iTrader: (9)
Join Date: Dec 2011
Location: SFBay
Posts: 408
Total Cats: 61
Apologies for getting a little off topic, but it depends if your NB is a CA car or not. For example, my NB's emissions system is CA spec, and under the hood on the emissions sticker, it states that the car came with two cats. Depending on how ---- your smog tech is, you may be able to get away with this if they don't actually pay attention or care.
...
Assuming your car is running properly and your main cat is healthy, you shouldn't have a problem passing sniffer with no precat, though I can't say that I've tried.
...
Assuming your car is running properly and your main cat is healthy, you shouldn't have a problem passing sniffer with no precat, though I can't say that I've tried.
This particular NB1 model is ideal because on a CA-spec car the front O2 sensor is in the same place as the OEM setup. With the heatshield in place it looks exactly like they expect.
I have two of these headers on my scrap bin from the two NBs I stripped, ready to be thrown away.
They are incredible heavy and I have a stainless steel 4-2-1 which I bought for 50€ ready to go on my NB once it is fixed.
Shipping them from Europe to US costs probably around 100$, so I am not sure they are worth their shipping cost?
They are incredible heavy and I have a stainless steel 4-2-1 which I bought for 50€ ready to go on my NB once it is fixed.
Shipping them from Europe to US costs probably around 100$, so I am not sure they are worth their shipping cost?
Theyre definitely worth more than $100. Not that I'm saying you should undercut my for-sale listing, but based on the interest I've had in this 4-2-1 setup so far, if you listed yours up for a similar price I'm sure you could sell them for a profit. This setup is better than the OEM 4-1, and those already command prices of ~$150-200
Reply
0
0
