Me and my Arrow

I've installed my Arrow titanium collectors and midpipe. I'm on my second map iteration and it's going pretty well. Initial impression from seat-of-pants is that I've lost a wee bit of low down torque. Once I've finished the map, I'll do an accelerometer 'dyno' run to confirm.

Weight saved is substantial. I weighed the Arrow collectors, midpipe and hardware in at 1.9kg. The stock headers and midpipe were 6.9kg! if you add that plus weight saved in doffing the Termi for the Mistral, plus rear pegs and all the other useless shit I've pulled of her, that's about 10kg. Not bad.

An interesting side effect is on the engine cooling, which is rapid. The stock double walled collectors help to retain heat, which is a good thing. Come the cooler months, I will have to install Mark III's  Simply Brilliant Oil Cooler Baffle (SBOCB).


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Noice!

I agree. Cool stuff.

Looks nice. Are the headers equal length, or at least nearer to equal length compared with stock?

No, they are within about 5mm of the stock.

Glad to see you are ignoring the flaky paint.

I was waiting for someone to comment. Bugger the paint, I'd rather be riding.

Mmmmmm... Titaaaaanium. I like it when the heat gets it all vari-colored.

On the heat loss - I wonder if an internal coating like Jet Hot would work with Ti? Cheaper to do the SBOCB for sure.

Looks good!

Right, finished mapping this Arrow-Mistral combo. The end result is a bit "meh".  

A heads up for those thinking about replacing the stock 'pretzel' midpipe. Be aware that pulling the pretzel will completely mess up your fuelling. 100% swear on a stack of k-mart catalogues this will complete feck up your fuelling. Fair dinkum, no bullshit. Even those who wouldn't piss on me if I was on fire, please believe this one little fact.

It doesn't simply require require a tweak of the main map, it also means a new delta-fuel map and a modified fuel-engine-temp correction table. It's not a bolt on replacement. Caveat emptor.


Now, the interesting bit. Comparing it to my favourite combo of the Mistral with dBk and stock pipes, top end power is better, but midrange power is lower, and low end and midrange torque is reduced. Not by much, but it shows up on the test runs and you feel it in your waters as well. This means acceleration is slower, which your bum dyno instantly notices.

Have a look at the curves. Remember, numbers are relative.

Power: Arrow midpipe + Mistral Vs Stock midpipe + Mistral

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Torque curves.

Arrow Midpipe

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Stock midpipe

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Data:

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Thanks, it confirms what I've though for a long while, that the 'Pretzel' had to be there for a reason. There is no physical/engineering cause for that loop. You could bung an O2 sensor in a straight pipe just as easily as a loop.

It also tends to reinforce my belief that physical resistance, especially in the inlet tract and the pre-muffler part of the pipe is a vital factor in maintaining good volumetric efficiency and cylinder fill, particularly in that tricky 4,500-5,500 region at wide throttle openings.

Pete

I won't be leaving it like this, I want my low down grunt back. I will play with the holes in the dB killer to see if I can slow down the exhaust to get some torque back. Alternatively a custom midpipe may be required. I am definitely keeping the Arrow headers. They look lovely in blue and purple.

I'm not educated in these matters at all, but now you've got the logical side of my noodle wiggling. Am I wrong in assuming that if the new header and mid pipe had a smaller inside diameter, you would retrieve the lost torque values?

CC, the new headers and midpipe have the same inside diameter as the stock pipes of ~47mm.

The issue is the Arrow midpipe has only one 90 degree bend, plus maybe ~45 degree at the collection point. The stock midpipe has two 90 degree bends, plus one of approximately 70 degrees. Bends effect exhaust gas velocity. The stock pretzel also adds more total length to the whole exhaust.

The end result is you get completely different exhaust pressure waves and velocities, which messes with combustion, which means different power and torque. In this case, less low down torque and power. But more power at the top.

Well, after the Ghetto Australis run and another ride today, I could probably live with Arrow headers & midpipe.  It rides super smooth and has enough went to keep most happy. I'd need to do a back-to-back comparo of my bike and a stock GRiSO, but I reckon this setup has more low down power and a smoother ride than a stock exhaust/mapped GRiSO and way more top end. However, having ridden her with the Mistral dBK map and pretzel, which has superior low down power & torque, I'm not sure I want to keep it this way, as I do miss the extra low down torque.

I've contacted a couple of custom exhaust specialists who claim to work with titanium to see if I could get a custom Ti pretzel made, but the response was "no" from one and none from the other.

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But it looks likeit has the same 180 degree bent as stock, maybe a bit wider but not so different, am I wrong? You could ask Arrow..

The colors are nice

Paul, it only has one 90 degree bend whereas the stock pretzel has 2. I figure the pretzel has a total of 260 degrees of bends and the Arrow has 135. Anyhoo, it's enough to change the fuelling requirements. I guess if you were looking for max top end power, the Arrow or the Agostini would be the choice.

You think I should ask Arrow to make me a pretzel? Hehe!

Oh, and if anybody is interested, I'm averaging 5.8L/100km or 40.3 mpg (US).

beetle wrote:

Oh, and if anybody is interested, I'm averaging 5.8L/100km or 40.3 mpg (US).

That's better than my normal mpg. If I hit "Trip 2" for the 1000 mile data sample I get about 36 mpg. Which is a data sample that covers everything I do - Not just a one day special.

Did you get the clutch fixed Mark?

Pete

Not yet. It was too freaking hot in the garage last night and I've only just dragged my arse out of bed this morning. I was thinking about riding it into the hills today, but it's 30 already and only 0830. Supposed to crack 40 today. You know I'm a sook. I'll have a look after I've had my wake up cocktail.

caffein, tablets + what?

beetle wrote:

Not yet. It was too freaking hot in the garage last night and I've only just dragged my arse out of bed this morning. I was thinking about riding it into the hills today, but it's 30 already and only 0830. Supposed to crack 40 today. You know I'm a sook. I'll have a look after I've had my wake up cocktail.

I just got back from Mystery Bay, have to say that given your propensity to going soft and floppy in the heat I'd leave the clutch lever until it cools down enough to be enjoyable riding!

Apart from the heat, it was 35*C at the top of the Clyde at 11.00AM, I have to say I'm very impressed with the Mitchy PR4's. The 3's were pretty good but the new 4's are very confidence inspiring.

Pete

I agree. Couldn't help myself. I adjusted the clutch and went up to Rosewood and down killer emu mountain. Clutch behaved and the G went like a dream.

It cooled down to a balmy 33 degrees across the mountain. Currently scarfing an ice cream and drinking bulk water at Tumut. 40 degrees. Managed 6.0L/100km even though I fanged it up to Rosewood and spent the last 20 km in 4th between 6k and 7k down through twisties.

living between 6k-7k is a lot of fun but I was surprised at much I enjoyed living down at 4k-5k. I am guessing I was probably actually going faster thru turns down in the lower revs but I am not very mature in most of my riding and I always wind up flogging the beast like a little boy.
When I was down around 4k I got 50mpg!!

DM

It's one of the things I like so much about the Mistral Hi-Pipe/with dBk map, it still has plenty of top end punch but the bottom end and midrange is so fluid and muscular that for where I ride and how I ride its a dream!

Pete