Making a custom downpipe
 

I'm trying to follow the reliability mod path. Just got the car running last week after doing vacuum hoses, FPD elimination, and fuel filter replacement. The car passed emissions with flying colors, so now i'm ready to work on the exhaust.

Does anyone know if there is somewhere I could buy flanges for making a downpipe for my FD? Or does anyone on here make them?

Are you looking for a DP for the stock twins?

If so, you should be able to pick one up in the For Sale section, just throw up a WTB add. It will probably be much cheaper (and faster) than trying to have one commissioned.

Yes, I want to make my own downpipe for the twins. I see some places that sell flanges for the s5 turbo but none for the FD.

Would really suck to have to get them made from scratch. Was hoping maybe someone on here knows if I can get one somewhere or if someone on here has access to a CNC plasma possibly.

Why bother when there are high quality bolt on options like the HKS for only $240

Downpipes & Midpipes (93+ RX-7)

^And a good used one for what...~$100? If you're REALLY into DIY projects fine I guess, but...

^ which was my point :lol: he could buy a quality piece that is KNOWN to fit and work well for the cost of the flanges that he wants custom made on a plasma CNC mill :rofl:

I have the HKS and its a steal for the price. 100% bolt on, and even got space for you to drill and tap holes to mount the OEM heat shields if you want (i did).

You could buy a used one, and cut off the flange. Then copy the pipe that you cut off, and weld it to the flange. When you are done you would have a custom DP just like the used one you bought :)

IIRC those are well made but for a RHD car...and intuitively seem like they'd be more restrictive. A good pipe if you have a RHD. Otherwise there are better choices IMO.

I think the trade off is worth it for the quality and EASE of install of the HKS compared to the Bonez and other downpipes I've had. I can't believe on the stock twins it's really that much of a power difference between HKS and some of the "true" 3" pipes.

To the OP, it's cool to fab your own parts, but save it for something that's not readily available, cheap, and foolproof. Buy a good quality downpipe (HKS is my vote) and don't look back.

^ I agree, dyno'd a completely stock car with just the HKS down pipe that we installed and it made 255rwhp

https://cimg3.ibsrv.net/gimg/www.rx7...1e0da18b9.jpeg

https://cimg8.ibsrv.net/gimg/www.rx7...337867df5.jpeg

^ So it made as much hp as a stock car that still had the precat with a similar design?

The FD is rated at 255 flywheel hp, not rear wheel hp. The stock FD makes around 225rwhp depending on health.

Dyno testing I did last month https://www.rx7club.com/3rd-generati...added-1104322/

^Ah...Awesome thread. Not sure how I missed that until now.

Can you recommend good downpipes for LHD cars other than HKS? I am in the market for one but the HKS design I am not really a fan of and what I've heard is that others have a very poor fitment.

Bonez, RX7.COM | 1993-1995 Rx7 Exhaust (330)7-ROTARY

There's also Pettit's. No personal experience but I know some who have them and no complaints Pettit Downpipe

And HKS is fine, just wouldn't be my first choice. It'd be fun to see side to side comparisons with HKS vs something like Bonez, but differences would likely be marginal.

Even if they're stainless, I would get it heat coated or at least header wrapped with sealant.

I have installed more Pettit & Bonez DPs then I can recall. The problem is that the turbos are very close to the body, making both of them a very tight fit. Additionally with that design, the pipe it bent in such a way that the bottom rear stud needs to be removed, not easily done with turbos that have been heat cycled countless time, new turbos are not an issue.

We used to offer the Pettit downpipe on our site, but so many people complained about installation that we took it down. Not to mention that both are more expensive than the already coated HKS.

Here is one we heat wrapped and painted.

https://cimg2.ibsrv.net/gimg/www.rx7...dcb4be733.jpeg


https://cimg6.ibsrv.net/gimg/www.rx7...f7d399548.jpeg

I really like how the pipe comes off the flange, the HKS has such a tight turn. What do you think is the power loss (if any) of the HKS against the Bonez or Pettit?

The HKS is actually not a tight turn and actually has a much larger exhaust capacity at the turbos, than any of the plain bent pipe DPs. Nobody knows if there is a HP difference, I know that I just made 340rwhp an a stock car with simple bolt-ons with this downpipe and I highly doubt it would have made any more with one of the other pipes. If you like the looks a different part, then that is your personal preference and has nothing to do with performance.


https://cimg7.ibsrv.net/gimg/www.rx7...e3a80cf822.jpg

https://cimg9.ibsrv.net/gimg/www.rx7...5ef7bc8cc7.jpg

https://cimg0.ibsrv.net/gimg/www.rx7...632b7a3864.jpg

https://cimg1.ibsrv.net/gimg/www.rx7...53eae933f2.jpg

And this one bolts right up to the stock cat, right? You have this HKS in stock?

i have an aftermarket JDM down pipe that was cut off when they pulled the JDM motor set.

It is cut off right where it collects into a normal round exhaust. It is NOT Cast like Banzai posted, but is either stainless or TI

I am in North Alabama, so shipping will be cheap/fast.

There is the FEED sonic, but the price is crazy at over $1000.00

https://cimg0.ibsrv.net/gimg/www.rx7...5349f5865f.jpg

Is this a custom coating over the HKS or does it come coated this way ?

Comes out of the box with that coating, just like the pictures I posted this morning.

Is that a ceramic coating?