Roman's 4GR V6 Carina discussion thread

[xsspeed]

Fwiw imo just get the tuning in then worry about fine tuning the sound, I'd be pretty confident that you'll find a combo that works in time

 

/I heard there's a guy you can hire

[Stu]

Turbos will soften the exhaust sound

[mjrstar]

Maybe make it sound like a v6 honda*

https://www.facebook.com/newzealandrallychampionship/videos/677994621865142/?mibextid=rS40aB7S9Ucbxw6v

 

* mounted in the back of a jazz with added supercharger, and sequential gearbox.

 

[Rhyscar]

Can relate. I suggest megaphones and/or stepping down then up 1/2" about 2/3 the way down the exhaust will help. Break up those nang sound waves a little.  

Happy to help fabricate more intricate things if you buy the cones/materials etc. 

[yoeddynz]

It should only take you about 4 attempts at the muffler and you be sorted by my experience

I've always loved the sound of this little mazda v6 - I can ask the owner, Andrew, who  @kws also knows and could possibly get more details.

 

Go to 3min.. 

 

 

[Roman]

19 hours ago, yoeddynz said:

It should only take you about 4 attempts at the muffler and you be sorted by my experience

Yeah I can see that. 
So did some top level science today. 
I put a spatula type thing over one of the muffler outlets. It cuts down the bassy noisy by heaps and the tone changes a fair bit. 
I'm thinking the secret sauce is probably to do with keeping the exhaust pipe diameter small, then just adding more pipes if you need more flow. 
Reason I think this, is most factory cars have small diameter pipes. 
Then when someone puts on a big bore exhaust, it gets a real deep tone.
I think one component of the exhaust noise that you cant change is the frequency that relates to how many rpm you are doing x how many cylinders you have.

But then secondary to that, I think the tips probably resonate at a frequency relating to cross sectional area.

Some supporting evidence: 

Motorbikes usually have small dia pipes and sound great.

Zonda has 4x smallish pipes and sounds incredible



This other zonda has 4x smallish pipes and same deal



Then here is a zonda with only 2 pipes, that sounds like absolute bucket of shit:  (grading on a curve, for having started with one of the best sounding exhausts on the planet)
 

Four small pipes:
 

 

[mjrstar]

I thought I mentioned the tip Dia thing here but it may have been over on @yoeddynz thread.

If that diesel audi is like my suv, it may have speakers in the exhaust to augment the sound.

[keltik]

Best of luck. I have no advice because I've only ever been 100% happy with an exhaust note once.... And it wasn't on my car - but I spent a long time trying to recreate it

 

[Vintage Grumble]

I've always liked the sound of this, but its probably unbearably loud. Rice bubble tune and fancy g-bag probably add to the choiceness of the exhaust note.

 

[Guypie]

If it's one particular frequency you want to eliminate you could do a heimholtz resonator/j-pipe thing. I think it moves the frequency up or down by an octave

Calculators here:

https://strikeengine.com/helmholtz-resonator-calculator-exhaust-j-pipe-length/

An example of one:

[Muncie]

6 cylinders have a particular rasp to them unfortunately, i found this on my 300zx you need lots of mufflers to knock the rasp back, if you want volume go up in size at the back of system and keep the front mufflers.

Naturally Aspirated sound better with the back box not been straight through too.

My recommendation get an R35 GTR centre muffler I had one on my v6 NA and it actually sounded good, build system off that In 3 inch add or subtract rear mufflers till it sounds how you want. You have Throttle bodies to do all the squawking anyway.

 

 

 

 

 

 

 

 

 

Or chuck a turbo on it.

[Raizer]

I'll confess I haven't actually read the latest novel.

 

But X pipe, 2x small mufflers, side pipes, send it.

[yoeddynz]

Fantastic update. Very interesting for this fellow exhaust porn seeker.  

 

[mjrstar]

To save some fab time can you just make a slip on adapter, and get people to post you things to try with a  slip join inlet and whatever outlet they want tried?

Another Anecdote, young me and my mate built identical 1330 Cc engines for our minis, same cam  pistons, headers etc, mine had a 2 1/4 inch exhaust tip and his had a 1 3/4.

His sounded way better, mine was (still is) obnoxious. 

Your post also has me thinking maybe I should re-think the tip on my honda, then I realise there is no hope because its a honda.

[Nominal]

Lots of small tips you say?

[Beaver]

 @Roman same cross sectional area but more friction losses no? (Due to more wall area of multiple small pipes vs one big pipe). Dunno if it's meaningful or not but. May need to add on a few % bigger area.

I seem to recall @BobbyBreeze going down this rabbit hole many moons ago looking at oval pipe profiles to get max ground clearance but maintaining the same flow capacity 

[shrike]

For when you get FXE pistons :p

 

[Roman]

The 2GR is normally 10:1 compression or something, and the FXE pistons bump it up to 12.5:1

The 4GR is 12:1 by default, and there's no FXE version. 

As the 4GR is already a race ready engine (conditions apply)

Conditions: 
Absolutely garbage valvetrain, pulleys, rockers, valve springs etc

[shrike]

3 minutes ago, Roman said:

The 2GR is normally 10:1 compression or something, and the FXE pistons bump it up to 12.5:1

The 4GR is 12:1 by default, and there's no FXE version. 

As the 4GR is already a race ready engine (conditions apply)

Conditions: 
Absolutely garbage valvetrain, pulleys, rockers, valve springs etc

He also goes through machining the cam phasers for more movement and timing shift, think they get it up from 40degree to 55degree of movement

[Roman]

Might not be any point with my motor.
Since it's got a longer rod ratio than the 2GR, the piston dwells at TDC for longer.
So it would likely hit pistons sooner than a 2GR.
Maybe cant make use of the extra range anyway. 
Will see. 

Ordered big cams! Exciting