Exhaust design thread...

[wagoon 2,429]

I base my 1 3/4 idea on only what I have seen others use and the results. I am no techincal guru but I ask alot of questions to try and expand my knowledge, my brother use to throw stuff at me when I asked too many questions. The 1 3/4 is mainly based on v8 setups where the setup of the engine has passed a certain level of performance and the change to larger primaries has made a difference. I think this engines setup especially with the roller cam warrants the larger priamaries.

[matt_lamb_160 252]

Ok, wagoon that's fair.

 

Clevo, if you are looking for pulse tunning you use a baffle collector between the primarys and secondaries which in effect creates a big step anyway as a result of the collector volume. Without the step up you do not have two seperate volumes to tune (also why I do not like the 50-50 split) and you could use a 6 into one setup instead. The step up is a part of how tri y setups work. The 6-3-1 setup could be better (I have not put too much thought into it), but the 6-2-1 is a long standing arrangement.

 

Sly, if you do go 6-3-1 just watch your firing order and make sure the exhaust pulses entering each collector are evenly spaced.

[Clevo120Y 815]

I agree that the 6-2-1 is also a proven combination I just think it is more suited to lower/mid range power and the 6-3-1 for higher rpm output, if only we had the $$$$ to try a custom set of both

[wagoon 2,429]

Matt do you think that the way a roller cam works, the primaries should stay on the smaller side? The reason I ask is because my previous statment was based on a standard large cammed engines where the extra volume in the primaries seemed to work where as Im now wondering if a roller cam will need more scavenging to draw out all the gas as the valve will be open longer?

[matt_lamb_160 252]

The valve is not actually open longer in total, it just opens and closes at a faster rate. The cam type will not have much influence on the required primary pipe diameter which is set by the average mass flow rate/air velocity entering the exhaust. The same air is still pumped out, the better cam just makes it easier for the engine (lower average pressure drop across the head).

 

The main effect the cam type will have is on the tunned length as the effective valve opening will occur sooner.

 

Realistically speaking, because Sly will not use the power band below 4,000rpm and he will spend most of the time above 4,500rpm, the 1 3/4" pipe is probably pretty safe.

 

Hopr that all worked, all typed on my phone.

[wagoon 2,429]

Matt, thanks for that

 

Edited because I cant spell

[blu xe 825]

Fark me my head hurts reading all this! Lol.

[clevocortina 1,109]

Hey sly are you talking gonzo in geelong?

 

or is there another Gonzo with a excellent rep for doing grouse exhaust work.

[slydog 7,873]

Yeah Gonzo G town bruz...

[ando76 4,354]

Are the pipes you have 1-6 5-2 3-4 Ando? Keen to even see a pic TBH...

Going into the shed (toy store) in town tomorrow so I will have a look and take a pic. 

[ando76 4,354]

Sly, if you do go 6-3-1 just watch your firing order and make sure the exhaust pulses entering each collector are evenly spaced.

 

This is exactly why I am trying an X pipe on the roller cam engine.  6 into 2 into an X pipe.  Look at the configuration of an off the shelf set of extractors.  Look at the firing order. Correlate that to the extractor design.  Pulse - pulse.  Exactly the same as a V8 and X pipes have been proven to make more power on V8's for years.  Just look at Vizard's exhaust studies. 

 

Call me mad - many have - but I'm cool with that.

[matt_lamb_160 252]

You're mad!

[slydog 7,873]

After doing some nerd research of compressed fluid flows the biggest concern is every type of engine and cyl count likes different things to work best.Stepped pipes of surprisingly short primary lenths are used in f1yet nascar seems to like longer primaries due to the use of tri y pipes...prob get where this is going now.

 

My issue is mine will not rpm like a cup car @9000 plus but the basics are there to support steps and collector design as more important than actual pipe sizing after the collectors.A point noted already...but yes cup cars use tri y pipes and merge tapered collectors which is what I want to hear as I already have the extractors to support that design idea.

 

Ill cut the current collector off my pipes and do some measurements on the secondaries and plan the collector from there with in the constraints of the car.Ill cruise local shops but I doubt ill get any help as there all about stock mostly.

[n00bus m@x1mus 465]

Ive got a set of those Genie 6-3-1 extractors in the shed, they had a good throbbing note to them and got louder the more it revved.  I pulled them off to be replaced by the current ones that are pacemaker units with 6-2-1 design with lengthened 2" secondaries to about 1.2m total length from head to collector flange. Makes good torque up top but loses it off the line compared to the genies.

 

 

Comparing the pipes on that one above they look very very similar to the pacemaker 4480s that are designed for competiton 4.0L as opposed to the standard versions that are 6-2-1 design.  I also have a set of those pipes to go on my 4.0L build and take up a lot of room, so much that i think i will have to end up going to a rack and pinion setup just to get them past the steering.

 

 

If Pacemakers R&D is saying that the tripple secondary design is for top end flow in the 4.0Ls then id believe them to be the same for the xflow.

[Clevo120Y 815]

Yeah and you will notice also that the primary and secondary lengths are pretty much the same as each other. Nice pipes Clint.

[ando76 4,354]

Ive got a set of those Genie 6-3-1 extractors in the shed, they had a good throbbing note to them and got louder the more it revved.  I pulled them off to be replaced by the current ones that are pacemaker units with 6-2-1 design with lengthened 2" secondaries to about 1.2m total length from head to collector flange. Makes good torque up top but loses it off the line compared to the genies

 

See that feeling through the seat of the pants seems to contradict the theory that the 6-3-1's are better in the top end.  If the 6-2-1's are still making torque at the high rpm then that means that the HP ceiling is also raised.  Anyone that's spent anytime on a dyno knows that HP takes over when torque drops off.  Hmmmm me thinks two sets of pipes back to back on dyno and track only way to settle this. Time and Money once again. 

 

See how the secondaries stop short on the 4.0l set.  I reckon that has more to do with ease of fitment up to the Cat convertor than actual exhaust design.  I'd like to see a bit more length in that secondary before they meet the collector - especially as they have all just done a tight 90 to get to the collector.

 

One area where pacemaker are well ahead of the others is the pipe over cone design.  when I up my secondary pipe sizing I take the secondaries to the exhaust shop to have the ends expanded so that you get that same pipe over cone thing happening. 

[slydog 7,873]

Yeah didn't put it into words but thats the understanding I took from it too Ando...

[matt_lamb_160 252]

Pacemaker's R&D? They make pipes. They are great at what they do (fabricating extractors), but I wouldn't give them too much credit.

 

"See how the secondaries stop short on the 4.0l set. I reckon that has more to do with ease of fitment up to the Cat convertor than actual exhaust design". This quote from Ando is spot on I recon.

 

He is also correct about this "One area where pacemaker are well ahead of the others is the pipe over cone design". The cone over setup is about the extent of their "R&D" in my opinion.

 

The ratio between primary and secondary pipe length is reasonably arbitrary as it will not change the "tuned" rpm of the extractors (neither will the total length), it will just "rock" the output about the tuned rpm created by the pipe sizes (I am not going to go into how, because it doesn't matter). Long primaries and short secondaries support the upper rpm for the tuned region (5,000+rpm in this instance). The 50-50 idea is ok as it is taking a middle of the road approach. But, I think people designing extractors for maximum effort engines that use primaries that are on the short side when compared to the secondaries do it for one of four reasons:

 

1) They think the pipe diameters may be slightly to large (some could say this if Sly was to use 1 3/4" primaries as it is hard to pick between it and 1 5/8")

2) It is easier to bend two pipes around things than six

3) They are guessing because they saw someone else do it

4) They don't care

 

Stepped extractors would work for you Sly especially because you are right on the boundary between two pipe sizes. But, you need to make sure you do not bring the step in to early (based purely on what I have read/heard from professional engine builders, not my understanding).

 

I think the best bet is to tell us what you have got to modify and make the best possible setup out of them. If you keep similar lengths you should be able to cut them up and get the bends copied in a more suitable pipe size (if need be).

 

Or you could get these guys, http://www.hurricaneheaders.com.au/hurricane/index.htm, to bend you up some in one of their stock configurations but with your pipe sizes and you make/add your own final collector. I asked them about doing a set for me a few years ago (I ended up using a set of stock Perry extractors instead) and they were happy to do it for a reasonable cheap price ~$500 at the time I think.

[wagoon 2,429]

Noobus are the pipe diameters the same for both sets? Did the exhaust design change at all when the pacemakers were put on?

[slydog 7,873]

So doe's it matter if I'm happy with the current extractors as are but with custom collectors and pipes (as per first post LOL) or do I (insert Jim Jeffries voice over here) FUCKIN HAVE TO MAKE SOME FUCKIN CUSTOM one's SLY ya lazy kunt... LOL

 

The research I did found the higher the RPM use of the car the shorter the first step needs to be,F1 use ridiculously close first step of around 200-300mm and a step up by 10mm!They since went to 2 steps and evenly spaced but again we are talking 19,000RPM engines.Hence the connection to the Nascar cup car exhausts where they do infact run tri y pipes and no steps till collectors...but as the firing order and collectors don't match in for even pulses they run SLIGHTLY (and only just so) bigger pipes on them cyls to even out flow.Now as before they are a 9000rpm engine but they do use tri y's as per rules these days so if it works for them it should be a close indicator as to what should for my current pipes.

 

Funny I use to run Hurricane 4 into 1's on my ESP...

 

On another note I found a guy willing to help out in town and keen on the idea of working on a 6 banger.Fingers crossed it works out for me.Every single shop bar the shop that was closed didn't want to touch it except this little place.So on the walls in his office is pictures of Escort rally cars with webers and shit on em...hell yeah boi!

 

Right back to the nitty gritty shit of compressed fluid dynamics/flow or what the fuck ever...     

 

EDIT So Matt a set of HU408STM

[Clevo120Y 815]

For sure use your existing pipes and a merge collector. I don't know the answer but what are the fastest crossflows in the country running pipe wise? I know Jason's are 6-3-1 but what about Ken and Wazzy, I haven't seen there pipes.

[slydog 7,873]

Wazzy uses paceys with a single 2.5 or 3" before the diff,Mossy and Jase's extractors where built by the same place "but Mossy runs a 3.5" pipe size...somtimes,when it's not on the trailer as witnessed by Jase

[Clevo120Y 815]

So that's 2 out of 3 that run the 6-3-1, mind you wazzy's numbers are super impressive and his combination in Corty might go number 1 and through a smaller tail pipe is just freaky LOL

[slydog 7,873]

So back to this for a minute...I know it isn't spot on but for a custom exhaust that is on a "CAT" convertor car instead of the merge tapered expansion chamber use a 100CPI tapered cat for the chamber (to keep it legal) and functional.OK mine is beyond legal at any stretch but there is merit in the basic idea as you can cut shape make the front/rear of the cat anyway and still fit your collectors and yet retain a legal system.Just leaves the 4 link,chassis mods,space cab,no pollution gear,prob noise among other things to hide LOL.

 

In saying that I have yet to see a cop stick his head under the car and ask where the cat is

 

 

 

[PRO250 1,506]

the 6-2-1 pipes on a 4litre worked better then a 6-3-1 setup. jim mock motor sport did a back to back dyno and track testing on pipes and the shit press bent pips in the 6-2-1 with short primerys and long seconderys worked best in there car. i used a set of the paceys in my ED XR6 before it was turbo it was flat as a tack over the shitter pipes it had in it before. i still had the same exhaust i just changed them cause the new ones where jet hot coated and looked better


this is melting my brain i did all this in 2003 and it made more power, but i think anything over off the shelf gear will on a engine thats built for one thing, fast