Rexy84

I seen somewhere in some of the header threads that it is better to modify the existing manifold to flow from the stock size to a 3" outlet to mate with my Racing Beat midpipe. Does anyone have any recommendations on materials, where to cut or have any pictures or How Tos on this?

Thank you in advance.

CaymanRotary

It makes sense to have a wider opening if running an aftermarket exhaust. However, you wont see a lot of HP gains from it with the Renesis engine. Because the stock manifold is cast iron, I would be very careful if you are going to attempt to bore it out. There is no real way to repair the manifold if you bore it too thin. Also, you may need to tune the ECU so it can make use of the extra exhaust flow.

All in all, unless you are running a turbo or supercharger it's really not necessary.

Rexy84

I am not talking about ‘boaring’ or posting the exhaust manifold.

I actually found the thread I was looking for.

https://www.rx8club.com/series-i-aft...thread-266914/

scroll through and you’ll see team RX8s modified stock manifold

CaymanRotary

Yea, I wouldn't copy that. He has the time and resources to build more if something goes wrong in construction, or over time as the car is driven. Unless your car is strict racing application, this won't really be worth your time or money to do. Looking at a slight HP gain on a stock engine. If I were running a turbo racing setup, I would just buy a set of stainless steel headers.

Rexy84

My car is not a daily driver, it is about to go thru a Pettit racing stage 3 build. I’m sticking N.A. for now.

This isnt that much work, and a trustworthy header that I’d buy (racing beat, black halo) are $500, so in your opinion you don’t think the fabricated stock manifold will be in the end cheaper and more free flowing? The aftermarket headers only exit at around 2”...

thanks for your reply

200.mph

iTrader: (9)

pretty sure teamrx8 has a very detailed thread on the renny manifold fyi

CaymanRotary

Well in your case it is a viable upgrade then. Aftermarket stainless steel pipes pretty close to 3". Most are 65mm to 70mm. The thread seems pretty detailed but it doesnt show how he constructed those pipes. It's really not something that should be attempted unless you have background in that type of fabrication. For me, it would be cheaper to just buy an aftermarket header than to attempt to modify the stock header yes.

Rexy84

Check a couple comments above, I found and linked said build thread.

Thank you much tho, it is pretty insightful indeed.

Rexy84

Can you point me to a trustworthy RX8 header with a 3 inch outlet? I prefer not to have a “bundle of snakes” or “matched length tubing” and I’m not seeing any mainstream headers with an exit of 3”...

i currently have a racing beat dual resonated midpipe and HKS dual day back exhaust.

CaymanRotary

Cant really help with that. However, you could buy a cheap stainless steel header and modify it so it gets the 3" you want. Would be 100x easier than trying to modify the stock one. Cast iron is such a crappy material to work with.

Rexy84

Thank you. I thought about that. Just fearful of a cracked header and shitty fitment from the cheapo ones

CaymanRotary

It's time consuming, risky and expensive either way you go really. I like the idea, but its gonna be a lot and I still doubt it will give you huge HP gains even if you did it correctly. I'd save that mod and put the money elsewhere. Headers should be the last thing you think about if you are unable to get the power you want. You are better off just going the forced induction route to be honest. Money is better spent there.

Rexy84

Header is literally the only thing left for me to buy or replace, besides a Turbo or SC.

Also, if I were to go Turbo or SC wouldn’t I need an aftermarket header anyway?

Steve Dallas

A turbo would require a new manifold. A SC would not.

Really take your time and research what is available to be gained from a header. Most of the restriction is in the ports themselves. You might get 3 to 5 HP above 7500 RPM. Worth it?

TeamRX8

iTrader: (25)

Unless you want to spend between $1500-$2000, just take a Racing Beat header and put a good straight 3” collector on it. Even then it will still cost up near $1000 if all new parts. If you can find a used header it will save you some money.

Here is an example, longer tubes not necessary, do not put a reducing collector on it like he did

https://www.rx8club.com/rx-8-racing-...rx-8-a-220741/

Rexy84

So, to be clear... in all of your opinions... after I’ve exhausted (no pun intended)” all available and efficient porting, balancing, blueprinting, (stage 3 Pettit) and bolt ons (midpipe, Catback, ignition, AEM intake etc) you’d still not get a header? Stock is still the best option, even tho it would be the only “stock” piece left ?

Rexy84

I really like this idea of lengthening the Racing Beat header ❤️! See I’m successful with no kids and an awesome wife. I need something to spend my money on 😬

CaymanRotary

Nothing the bolt on, unmodified stainless steel aftermarket header couldn't handle. As mentioned before, the real restriction is in the ports, not the header. You could run a supercharger no problem with the stock header.

CaymanRotary

The Dream! Dude just go buy the new 2020 Corvette lol.

Rexy84

Haha stop. Don’t make me leverage my life savings for that magnificent mid engine masterpiece.

But, seriously...I’m going to make my RX8 as beastly and fun as possible and then most likely get a 2009+ 911 with PDK tranny. Or... a mid engine vet in 2-4 years

TeamRX8

iTrader: (25)

You don’t listen any better than anyone else, no surprise.

Rexy84

Interestingly you quoted my response to something I was listening to. My whole point was deduced and in direct response to Cayman... why bother with a nonsense comment?

Rexy84

Whats even weirder is you’re the whole reason I’m seeking this mod in the first place. I love your modified stock setup. Why not just appreciate the hunger you inspire in others rather than judge? You’re no one, in comparison to anyone else. Happy Thursday

TeamRX8

iTrader: (25)

No, you’re response was to my post and I responded back, noob.

Rexy84

Touché. However, Either way, sir. Noob or not, it’s my money, my time, my efforts. I’ll still be happy either way. I appreciate your input and the amazing thread and research you put into your original post that I cited and loved. Thus, provoking my entire thread in the first place.

I found a thought I liked, from you coincidentally... and somehow you’re still judgmental? I don’t trust someone or myself modifying a 15 year old iron manifold when I can buy something from Racing Beat and do a similar modification to with more longevity and similar results to add on to my existing and to be modified setup.

Thanks for your 2 cents.