Hey Folks,

Trying to order a factory jdm downpipe, just wanted to check the latest p/n. I have N3A7-40-500A, but wasn't sure if it was superseded and didn't have much luck searching around. Anyone gotten one new recently?

Thanks

 

I also see this one listed as the “280hp” version: N3G140500B

Nengun has your part number priced, not sure where youre ordering from. https://www.nengun.com/oem/parts/MTE...N5c3RlbSAobXQp

 

the N3A7-40-500A is the 265ps version, N3G1-40-500B is the 280ps version. 280ps is slightly larger in diameter

they both are available, price is close, i'd go with the 280ps version

 

I ordered the old p/n from Nengun some weeks ago, but no tracking info yet. Hence me checking contingencies. Anyone other avenues to buy?

 

You could try rhdjapan. Though I ordered a few coolant hoses through nengun and they came in reasonable time. Have you contacted them for an update?

 

They have been responsive, we just don't have results yet. It is apparently some holdup on the parts supplier side, which I assume is Mazda.

 

I didn't know the 280hp one was different. It didn't even occur to me. I got mine used, and I presume its the 265ps one.

 

Is the diameter difference from 265 to 280 hp known?

 

I seem to remember that Mazda increased the downpipe diameter on the 99 280ps downpipe, that was in the literature when they were talking about all the changes - better IC ducting, abradable seals on the compressor housing, etc.

I think the difference is pretty small, like millimeters. Any aftermarket downpipe would outflow it by a large margin.

I can see the appeal of having the stock part especially in areas like Cali where it could be inspected.

Dale

 

From https://robrobinette.com/sae_article.htm

In the exhaust system, the front tube gauge has been reduced by 0.5 to 1.0 mm (0.02 to 0.04 in.) so that flow passage is increased while retaining the tube's outer diameter. The main silencer has also been redesigned. These changes result in about a 10% reduction - about 13kPa (1.9 psi) - in exhaust gas resistance.

Dale

 

the HKS downpipe is nice in CA, its pretty OEM looking

 

Ah, the ol' less is more. 20 years later and Robinette's site is still as useful as ever. Thanks for the link.

 

Heat management, OEM fit/finish, and boost control implications are also in play. I don't have the energy to fight Johnny Law, heat soak, boost creep, and OCD. Just trying to keep the car running happy. If it gets a wee bit faster, well that will be fine.

 

Got a tracking number. I wish they had been more candid about the process, but they did kindly write me back on all queries in good time. Maybe just an eastern/western business thing. I'll be interested to see if the new or old part shows up.

 

I heard that the HKS DP has attachments for the upper heat shielding from the OEM DP? That would indeed make it a somewhat safer choice for California smog check. BUT, I would still have some concern - last time I did smog check on my FD (which has a JDM DP) I went to a different shop since the regular one was down. Anyway this guy was super vigilant and he actually had his dyno installed between a vehicle lift and lifted my car for a walk around undercar inspection. I think any DP other than stock with cat or JDM would have been failed. I was a little concerned that even the JDM would not pass visual, but it did. JDM for the win IMO in California.

 

Also recall that. It has provisions in the casting, but you have to tap them out.

 

you are going to get the one you ordered...

 

That's what I would expect. Sometimes when parts are superseded you might order the old p/n and end up with the new one. That might explain the order latency also. Probably just wishful thinking. We'll see.

 

Post some pics when it gets here, I'm interested to see how a brand new one looks.

Dale

 

+1 on that!

 

these aren't superseded, there is the 265ps part and 280ps part. if it did supersede you'd be right. (sorry, parts are my job, its nit-picky! )

 

As ordered. Thanks, Nengun.



Gonna check the availability of the 280hp piece, too.

 

New is so nice. What is the inside diameter of the pipe?

 

Wow that is pretty!

Dale

 

I don't have a caliper handy, but IIRC it is 65.2mm, which is roughly 2.5". The restriction lies with the kinks in the cast, and it's pretty tight in there. I'd speculate the cross section is similar to a 2" pipe. No wonder people gain so much power with a fat DP. Extrude hone is the first thing that came to mind.

I thought it would be cool to cast a US style DP head to hook up to 3" pipe, so you'd get HKS stud fitment with US style flow and aesthetics. With rapid prototyping etc, it's probably not unrealistic to do a "small" cast run.