Let the tinkering continue.....

[Preen59]

Woah that's a substantial increase in powers. Nice.

[Greg Roles]

...and that's over the entire band, on 103kw TDI's, with a more modest Water/Meth injection pattern. I'm interested to see what's possible for say a max dyno effort!

Bottom line is it will assist in tuning the bejesus out of it!

[Preen59]

Should cool your EGT's too right?

Hehe keen to stick 10% in it Greg? I'll send you a litre if you are!

[gldgti]

Been thinking ahead for an exhaust system, did have my mind set on the uber nice but expensive 2.75" Milltek cat back, but I am all too aware just how little power cat back's usually liberate, and the fact the stock 2.5" is full mandrel. The forthcoming JBS DPF delete pipe is only 2.75" anyhow, and it's the dump pipe area, where the exhaust is hottest, that needs to be the bigger diameter if anywhere. So it's got me to thinking.....

Modify the stock pipe! Given I'll be joining the 103kw crew with a bit of soot action, I figure a downswept pipe is the go. Keep the stock twin outlets, but just have them as dummy pipes for the stock look and to fill the bumper hole. Never have to clean them either!

Been looking around for a suitable muff. Diesels pretty much drone below 500Hz just like gassers, but they do have slightly different needs from what I have read thus far. Been researching Magnaflow and other diesel specific muffs, today I found "aero" mufflers, and they are VERY interesting. Seems if you mount it up close to the downpipe, it actually helps evacuate the system. I'm thinking of putting one of the resonated 2.5" versions right up behind the flexi joint post dump pipe, and deleting the stock resonator prior to the rear axle. Dump the pipe to the ground at rear axle level.




Despite obviously being a lot nicer, I just can't see a 1/4" bigger Milltek being $1000k plus better, nor liberating a whole lot more power. Hmmmmmmm

The "XL" version is resonated - but it's just a ceramic interior coating, still a straight through muff essentially. 15cm dia x 66cm long though! Lucky there's a ton of space in the floorpan tunnel, thanks to the R32.

http://www.aeroexhaust.com/

http://www.youtube.com/watch?v=iDTTO...eature=related

looks like a lot of expense to me mate - consider this- i went from a stock 2" press bent stock system including 2 baffled mufflers and a cat, to a 2.5" mandrel bent system with only a 12" louvred 'hotdog' (resonator) and a short, straight through "supercat" rear box. that resulted in basically zero increase in exhaust noise at cruise, and minimal increase under hard acceleration (i'm sure hte noise out the back is a little different, but inside the cabin is no real change).

now, i've increased the turbine outlet diameter from 24mm to 50mm, and what have i noticed??? didly squat. i was really looking forward to a bit of extra noise, but again, maybe a little different outside, but barely noticable (if at all) inside.

if i were you, i'd look at just removing the mufflers you have altogether and replacing with a resonator or two, or go a custom 3" system by a good exhaust shop. like you say, anything after the turbo is really just extra weight

[Greg Roles]

Yeah I see your point. Seems diesels, because of the lower EGT's simply have less noise than gassers. Noise comes from the retraction of the hot gas, so I can see a well designed system working without any muffs at all, but so too do I want to avoid that boomy noise old landcruisers with straight through systems put out. My research on about the only site i can find or have ever heard about says a system of at least 3" is in order, given the gas flows in a diesel to have true low restriction post turbo.

http://www.donaldson.com/en/exhaust/...ary/061237.pdf

Page 8. If I use the max efficiency of 3.0 ( which seems very possible from my research ) I get an intake flow (122"cubes) of 476cfm at 4500rpm.

The corresponding theoretical max is 1198cfm exhaust at a VE of 3.0, even 2.0 gives 798cfm which is a 3" exhaust minimum.

seems excessive, but I agree a big bore exhaust is far more important than a fancy muff, but I do like the science behind that Aero one, but yeah, a straight through hotdog to stop any resonance is all I really need.

The main pitfall exhaust wise is that the JBS DPF delete downpipe is 2.75", and whilst this is plenty big enough, if I truely want next to no restriction, I need a bigger dump pipe. Need to chat to Gav and JBS about that, and tossing up the idea of a parrallel 1" pipe giving 3.75" total, into a 3.5" cat back with perhaps a single big bore jap straight through muff. The jap stuff flows very well overall from what I read. Would only liberate the last 10hp, but heck, if I'm gonna spend the money, might as well go large!

I'm a long way off doing a muff, just tossing ideas at present. Spent my play money on the water meth, as that was a definate.

Oh and Preeny, I'd try 100% nitro injection just for giggles, might have to do a little research on it though!

[philthy]

The main pitfall exhaust wise is that the JBS DPF delete downpipe is 2.75", and whilst this is plenty big enough, if I truely want next to no restriction, I need a bigger dump pipe. Need to chat to Gav and JBS about that, and tossing up the idea of a parrallel 1" pipe giving 3.75" total, into a 3.5" cat back with perhaps a single big bore jap straight through muff. The jap stuff flows very well overall from what I read. Would only liberate the last 10hp, but heck, if I'm gonna spend the money, might as well go large!

G'day mate. Just a note that the cross sectional area of a pipe is proportional to the square of the area, so adding a 1in pipe to a 2.75in pipe in parallel will give you a cross sectional area equivalent to a 2.9in pipe, not 3.75.

Also, most of the losses in the pipe (pressure drop) are a result of friction between the walls of the pipe and the gas. These losses are proportional to the square of the velocity of the gas.

So, if you double the diameter of a pipe, you increase the area by four, and reduce the velocity by a factor of four (and therefore reduce the friction losses by a factor of four squared, or 16)

P.S. any mechanical engineers here please feel free to add re. losses in a gas pipeline, I usually only work with water

[Preen59]

Gees Greg you're really going hard core with this sucker. I like it.

Oh and Preeny, I'd try 100% nitro injection just for giggles, might have to do a little research on it though!

With what, 17.5:1 compression? That'll throw the crank into the road.. Literally. Nitro engines don't break, they explode. Haha.

[Greg Roles]

18.5:1 Preeny!! Where can I get methanol in bulk mate? VP fuels??

Given the DMF and gearbox etc is still stock, I reckon I'll be pushing things with just the delete, tune and Snow kit. See what happens.

Interesting stuff Phil, seems I need to enlist some more time into working this out, but it sounds like yet another vote for bigger is better? But how big is too big??? Seems odd the monster SUV's in the USA that run 500-1000hp use 4" and 5" systems, and here I am with a third the capacity, but more revs, talking 3-3.5". Seems excessive, even to me, and I'm keen to go nuts!

Anyone from Bris have any recommendations as to who can do nice inlet plumbing welding, and who would be right into the exhaust end of things?

[Greg Roles]

Gees Greg you're really going hard core with this sucker. I like it.

Was always the plan mate, just started out slow covering all bases, doing my research and testing. Also knew DPF deletes would be the answer, so as soon as one became available, I jumped onboard. Should be an interesting year. Hope my gearbox survives it!

[craigy]

Greg, when we were racing post classic road racers we bought our methanol from a chook farm. Apparently chook poo is used as the bio mass. It might be worthwhile talking to the speedway boys about where they get theirs from.

/methanol.htm

http://holdren.com/methane/operation.php

[Preen59]

FYI, A 200l drum of racing methanol is about $230. Yeah that's correct, it's about $1.15 a litre. The price hasn't changed in a couple of years. We recently just bought a drum off a friend who races Sprint Cars.

(Methanol used to be twice the price of petrol/diesel... You tell me we aren't getting ripped off for our fuel!!)

[gldgti]

G'day mate. Just a note that the cross sectional area of a pipe is proportional to the square of the area, so adding a 1in pipe to a 2.75in pipe in parallel will give you a cross sectional area equivalent to a 2.9in pipe, not 3.75.

Also, most of the losses in the pipe (pressure drop) are a result of friction between the walls of the pipe and the gas. These losses are proportional to the square of the velocity of the gas.

So, if you double the diameter of a pipe, you increase the area by four, and reduce the velocity by a factor of four (and therefore reduce the friction losses by a factor of four squared, or 16)

P.S. any mechanical engineers here please feel free to add re. losses in a gas pipeline, I usually only work with water

its all a fluid in the end mate, thanks for chiming in there with good info.

[gldgti]

FYI, A 200l drum of racing methanol is about $230. Yeah that's correct, it's about $1.15 a litre. The price hasn't changed in a couple of years. We recently just bought a drum off a friend who races Sprint Cars.

(Methanol used to be twice the price of petrol/diesel... You tell me we aren't getting ripped off for our fuel!!)

Greg, when we were racing post classic road racers we bought our methanol from a chook farm. Apparently chook poo is used as the bio mass. It might be worthwhile talking to the speedway boys about where they get theirs from.

/methanol.htm

http://holdren.com/methane/operation.php

preeny, theres you answer

[Preen59]

Very interesting.

I should point out that "racing methanol" isn't 100% methanol. I'm not 100% sure what else they put in it (and they're not going to tell you), but it has other things in it to produce more power and burn cooler. I know that "Shell Racing A" used to have acetone and a few other goodies in it...

Having said all that, i'm sure for what you are doing, Greg, whether you use racing methanol or bootleg methanol, it will work just fine..

[Russ59]

Very interesting.

I should point out that "racing methanol" isn't 100% methanol. I'm not 100% sure what else they put in it (and they're not going to tell you), but it has other things in it to produce more power and burn cooler. I know that "Shell Racing A" used to have acetone and a few other goodies in it...

Having said all that, i'm sure for what you are doing, Greg, whether you use racing methanol or bootleg methanol, it will work just fine..

The final result will be the same