Alfa Romeo 4C Forums banner
1 - 20 of 40 Posts

·
Registered
Joined
·
4,018 Posts
Discussion Starter · #1 · (Edited)
Having my race shop make up a custom 3 inch diameter downpipe along with a 200 high flow cat that is relocated downstream away from the turbo.

I felt this design would reduce the heat and back pressure on the turbo. Hopefully make it spool up faster and be more efficient.

Then we tied into the existing twin tube diffusers my center exit exhaust. Had to replace all the existing exhaust pipe because it was only 2 1/2 inch diameter. Now everything is a full 3 inches all the way through.

Did not set off any CELs yet but we just started it up and did a few heat cycles everything looks good so far. But in a day or two I'm going to drive it around for three or four days to see if it sets anything off. As long as it doesn't snow again!!

The exhaust sounds glorious. Sounds like a big hole. A big deep hole! Very low sounding and quite loud. But not so much that it would be illegal or stand out as long as I don't jump on it in front of the police. But in a tunnel probably sound like a bomb going off!

Included a few sound clips but they don't really do justice. In one of the clips at the very first you can hear the shop radio which was quite loud and then gets drowned out.

When I drive it on the street I'll do a few more sound videos.

So far looks and sounds great!! The high flow cat is right before the flex.



 

·
Registered
Joined
·
4,018 Posts
Discussion Starter · #3 · (Edited)
Wow that's a tight fit, no rubbing at all? Looks like the flex pipe is binding a bit:(


They're not quite done yet they're moving it away from the crankcase a bit. There will be no rubbing.

Also you may be looking at the heat shielding they installed.

The engine and exhaust move together also.

Not sure about the binding you're talking about it seems fine.

Had a hard time uploading videos of it. But I did it via YouTube
 

·
Registered
Joined
·
8,541 Posts
I think I would be more interested in something like this vs a catless downpipe.
The combination of a deeper sound and no CEL sounds like a win-win.
I agree that there's never enough exhaust noise. As a daily driver in a state where we get smogged with a tailpipe sniffer every two years, this is the ticket.

Now, if I were building a dedicated track car, absolutely the cat would go.
 

·
Registered
Joined
·
4,018 Posts
Discussion Starter · #9 · (Edited)
Stopped by to see the final install took a couple better pictures to show that the flex is not bent. My original picture was misleading. Also a new sound file. FYI The engine warms up and the valves adjust after one minute into the video then we rev it up.

I like how they how added lots of heat shielding in any critical areas.

Also another photo showing the end of the exhaust but also look at how big the Sector 111 rear sway bar is! Massive!

My techs seem to really like the new exhaust. And they say they can hear the turbo through the exhaust now whereas before they could not. They feel it should spool much faster now. And I'm all for that!!

FYI we also found the stock boost pipe is rubbing on the rear under panel. We are going to secure it up a bit higher so it doesn't rub. But other people should look at that. They do have some type of factory protection wrap on it but it's starting to fray away already from rubbing. Can't really see it in these photos but it's there.


 

·
Registered
Joined
·
4,018 Posts
Discussion Starter · #10 · (Edited)
Got the car for the weekend been almost four months without driving it. Car is awesome!!!

New custom downpipe, high flow cat relocated away from turbo and big 3" exhaust piping throughout sounds awesome!!

Turbo seems to spool up twice as fast!

No CEL. If you baby the car is pretty quiet and no drone at all driving it. But if you step into it, sounds like a madman.

With the air filter and my new exhaust all the turbo, turbo blowoff sounds and open exhaust sounds are crazy!

Got to be there one of the most exotic sounding cars I've ever driven.

I opened it a bit from a stop under a railroad tressel and the loud noise was incredible.

Couple sound files they really don't do justice though.


 

·
Super Moderator
2015 4C Launch Edition
Joined
·
5,788 Posts
Sounds pretty great...hopefully not loud enough to attract unwanted attention by police. Are you going to try another dyno pull on the same one you did before. If so it would be useful as it would be apples to apples...same car, same dyno. Even though your last time pulled a CEL after some puills, you evidently did get a valid pull before it faulted. Between all the latest mods and the driving school you just attended I expect you to give some even more impressive lap times than last year. Just be careful and work up to them as the car is probably dramatically different in many areas than before.
 

·
Registered
Joined
·
4,018 Posts
Discussion Starter · #12 · (Edited)
Sounds pretty great...hopefully not loud enough to attract unwanted attention by police. Are you going to try another dyno pull on the same one you did before. If so it would be useful as it would be apples to apples...same car, same dyno. Even though your last time pulled a CEL after some puills, you evidently did get a valid pull before it faulted. Between all the latest mods and the driving school you just attended I expect you to give some even more impressive lap times than last year. Just be careful and work up to them as the car is probably dramatically different in many areas than before.

Thanks, yes I'm way pleased with the sound.

It's not so loud you can drive it mellow and it will blend right in. But if I was to step on it for sure it will get attention! I consider an equivalent to a Ferrari driving around. Different sound but just as exotic and loud. Maybe even more with the big turbo blow off sound. The cacophony of all the different sounds really is something to hear.

That's a good point I'll see what it cost to do a dyno pull and maybe do one right after the exhaust work. The EC V3 computer is coming soon I was going to wait until I got that before a dyno but maybe I'll do two different ones.

Really pumped about the extra power and immediate turbo boost this new custom exhaust seems to have given. That combined with the new upcoming EC V3 computer and I really should have something wild.

Now I may have to worry about too much power and power induced oversteer. With my big fat tires I never had to worry about that before.

Yes I'm a pretty patient guy I don't move into things too quickly. I worked too hard on these projects to screw it up by being a hot rod.

Today was the first day I drove it with the harness on that was interesting. Clinched it up real tight and it was nice! Hard to look over your shoulder backing up ha ha!

Also first time I got to drive with my new bushings installed and a new alignment with a full -2° camber. Wow did the bushing make a difference. Car truly feels like a go cart now. Turn ins should be amazing.

With all the suspension work and the negative camber my car is not as easy to drive on the street as it was before. Basically just feels like it has no slop in the suspension or steering at all. But it's still really not bad and definitely still streetable.

Kind of excited to drive a stock 4C again to compare the feeling of driving them.

Just found our sister autosports club is having an autocross Saturday and Sunday I'm going to get up early and drive about three hours to it. So then I can give the car a good thrashing on the autocross course with my harness on. That should give me a good test of handling for the road course coming later. I will have street tires on so it won't be as fun as it could be but will be a good time I'm sure.
 

·
Registered
Joined
·
8,541 Posts
Sounds good (on all accounts). The autoX will be a good cell test as well.

Find out if your shop wants to build more of these down pipes. Once all the kinks are smoothed out, I'd be interested in one.
 

·
Registered
Joined
·
4,018 Posts
Discussion Starter · #17 · (Edited)
I thought I would put some of a post into this post now that I have really tested out the downpipe and exhaust.

The new downpipe and relocated cat and big 3 inch diameter exhaust throughout was incredible. Its loud and would be too loud for some people that daily drive their car. But I believe even some daily driver people would like that sound as it's not insane loud like a catless system probably would be. My system has a 200 cell high flow cat which is just about right. It also keeps the car legal.

Definitely feel some extra power. Not sure what it is but I from what I have heard from others and from what I feel would guess possibly additional 10-15hp.

And I just drove the car 400 miles and did nine hard autocross runs without triggering any CELs so I don't think that's going to be an issue with my exhaust. Seems Alfa has been liberal with allowing people to do this versus other cars that are very structured and it's hard to change your cat without triggering error lights.

Driving down the highway road you can definitely hear it but it's not a drone it's just a hum, almost sounds like road noise. If I turn my stereo up fairly loud almost goes away but I have a custom stereo that goes pretty loud. Even my prior exhaust which was quite loud but I could make the nose almost completely go away with the stereo. But with this new system it's always there a little. Who knows I might devise my own valved exhaust using a muffler for highway use but then being able to open it up like it is now for track use. But since I'm OK with the noise even though I daily drive the car I don't think I will do that.

On the track the sound is truly glorious! People told me my car was as loud as the modded Corvettes but that it sounded better and more tuned. They described as a loud low tuned sound. I really think it puts on a show! I'll get a video of my car doing some road course tracking April 1 and that should be a good sound file for everyone.

With the loud sounds of new 3"diameter exhaust throughout, the turbo sounds and the turbo blow off sounds the car is pretty exotic sounding. There are certainly cars louder exhaust systems but its rare to find other cars that sound as exotic as the the modded 4C does with its cacophony of crazy loud sounds.

Driving a car in the street you can just drive it mellow or in natural mode and no problem with the noise. You could drive by police all day without any problem. But if you step into it a bit during shifts omg whereas my car used to bark between shifts....now it explodes! I really think you could scare some person in the car lane next to you if you wanted to. I went through a small tunnel and punched and it sounded like a bomb going off!
 

·
Registered
Joined
·
8,541 Posts
Al, in another thread you said your race shop won't sell custom parts that they don't install.

Is this true for the downpipe?

If they won't sell the pipe, will they sell the information so a local fabrication shop won't have to start from the beginning?
 

·
Registered
Joined
·
4,018 Posts
Discussion Starter · #19 · (Edited)
Al, in another thread you said your race shop won't sell custom parts that they don't install.

Is this true for the downpipe?

If they won't sell the pipe, will they sell the information so a local fabrication shop won't have to start from the beginning?

Good point I didn't ask them about this. I think all models are exactly the same so I think they would.

But on the other hand being 3 inch diameter all the way through it's kind of tight. And they also installed heat shielding which attaches to the body I believe. But I will ask them next week.

But I'll be honest with you. I kind of asked my race shop the same thing about me buying a downpipe from a vendor and having them attach it to my existing exhaust system saying "so you don't have to start from scratch" he kind of smiled and laughed at me. Point being a great exhaust fabricator doesn't need any help to make a great one. The trick is finding one good enough.

Good place to look is a race shop or a hot rod American muscle car exhaust fabricator. They make one off stuff all the time that has to hold up during racing or drag strip racing.
 

·
Registered
Joined
·
8,541 Posts
Good point I didn't ask them about this. I think all models are exactly the same so I think they would.

But on the other hand being 3 inch diameter all the way through it's kind of tight. And they also installed heat shielding which attaches to the body I believe. But I will ask them next week.

But I'll be honest with you. I kind of asked my race shop the same thing about me buying a downpipe from a vendor and having them attach it to my existing exhaust system saying "so you don't have to start from scratch" he kind of smiled and laughed at me. Point being a great exhaust fabricator doesn't need any help to make a great one. The trick is finding one good enough.

Good place to look is a race shop or a hot rod American muscle car exhaust fabricator. They make one off stuff all the time that has to hold up during racing or drag strip racing.
There's a few good shops nearby.
 
1 - 20 of 40 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top