Down under, an idiot and a 400F
- Thread starter neevo
- Start date
crazypj
Split personality, I fake being smart
There is something wrong with the formula, it should be coming out longer than 10.5"
That does sound about right for an intake length though ;D
2nd harmonic will be at 13,577rpm, 4th harmonic 6,584rpm 8)
It should also be exhaust closes 30 ATDC not BBDC
You want 'extraction' pulse to return to cylinder as valve closes so time from valve open to valve close, try using gas velocity around 320 ft/sec (one way to end of 'pipe) and acoustics around 1100ft/sec
with time of 180 + 35 = 215 degree valve open divide into rpm/min (total crank rotation is 720 so not as radical as it sounds)
That does sound about right for an intake length though ;D
2nd harmonic will be at 13,577rpm, 4th harmonic 6,584rpm 8)
It should also be exhaust closes 30 ATDC not BBDC
You want 'extraction' pulse to return to cylinder as valve closes so time from valve open to valve close, try using gas velocity around 320 ft/sec (one way to end of 'pipe) and acoustics around 1100ft/sec
with time of 180 + 35 = 215 degree valve open divide into rpm/min (total crank rotation is 720 so not as radical as it sounds)
You want the sucking pulse (negative pressure) at TDC on overlap and the stuffing (positive) wave as the valve closes just like a 2 smoke, but the math usually gives odd numbers so you go with 2x the calculation or more times.
And peak revs for that motor should be closer to 10,000 or 10.500 which seems to be where it's most happy - or drop revs in the calculation to peak torque so that it pulls harder as you accelerate.
And peak revs for that motor should be closer to 10,000 or 10.500 which seems to be where it's most happy - or drop revs in the calculation to peak torque so that it pulls harder as you accelerate.
neevo
Over 1,000 Posts
Woo hoo! We have success on the exhaust calculations, although I still have a couple of questions. I found the exhaust opening number for the 400F from my Clymer manual (35 degrees before BDC) so used that. In addition PJ kindly sent me a link to the BG Tuning Manual which showed me some ways to calculate the exhaust measurements in metric (which is where I suspect I was coming undone before).
I had to estimate the revs the bike made max power, not sure if I had to do this based on the current max power point of the bike or if I could nominate an ideal RPM. I went the latter and put in 8,000 RPM (assuming this would give plenty of power in that point where you overtake). If those that know what they are doing could feedback on this point I would be highly appreciative.
All in all the measurements appear to be spot on (and the book is very easy to follow):
I built a spreadsheet for the calculations which I am happy to share of anyone wants it. Just enter a few items and the rest works itself out. Also most of the info I read (Sonrier's excellent Build a Functional Cafe Racer and the BG Tuning Book) talk about two ways to build a header for a 4 cylinder. 4-1 for max power or 4-2-1 or a broader spread of power, I am leaning to the 4-2-1 for street use as I would assume it would provide a greater sense of power and useability, however not if it really reduces the "hit", to those that know, please advise me on this one.
So the final results are:
Header length: 24.4"
Header diameter: 1.09"
Secondary header length: 24.4"
Secondary header diameter: 2.04"
I had to estimate the revs the bike made max power, not sure if I had to do this based on the current max power point of the bike or if I could nominate an ideal RPM. I went the latter and put in 8,000 RPM (assuming this would give plenty of power in that point where you overtake). If those that know what they are doing could feedback on this point I would be highly appreciative.
All in all the measurements appear to be spot on (and the book is very easy to follow):
I built a spreadsheet for the calculations which I am happy to share of anyone wants it. Just enter a few items and the rest works itself out. Also most of the info I read (Sonrier's excellent Build a Functional Cafe Racer and the BG Tuning Book) talk about two ways to build a header for a 4 cylinder. 4-1 for max power or 4-2-1 or a broader spread of power, I am leaning to the 4-2-1 for street use as I would assume it would provide a greater sense of power and useability, however not if it really reduces the "hit", to those that know, please advise me on this one.
So the final results are:
Header length: 24.4"
Header diameter: 1.09"
Secondary header length: 24.4"
Secondary header diameter: 2.04"
ronnie
Calm down and sail on
I'm just going to wait for the dust to settle on this haha! I am absolutely lost with all these acronyms and numbers and ratios yall are throwing around!
I do like the pipes kicked up and sucked in better, my opinion. I think you need to sit on it and see what it looks like with a body on it. Have someone take a picture of you sitting on it. The small seat and big cans may work great when you get on. Have a go at it!
Sent from my HTC6500LVW using Tapatalk
I do like the pipes kicked up and sucked in better, my opinion. I think you need to sit on it and see what it looks like with a body on it. Have someone take a picture of you sitting on it. The small seat and big cans may work great when you get on. Have a go at it!
Sent from my HTC6500LVW using Tapatalk
deepwaterimports
Over 1,000 Posts
How long till we can hear her purr
Ed
I have been skipping through this thread and your blog and this is a great build
are you still looking to do a little powder coating ?
It looks like I don't live to far away (Baulkham Hills) and have a stove that has just been replaced
if you want it you are welcome to it as I don't think I'll be doing my own powder work as I plan to leave my engine raw unpainted
Message me if interested
Keith
I have been skipping through this thread and your blog and this is a great build
are you still looking to do a little powder coating ?
It looks like I don't live to far away (Baulkham Hills) and have a stove that has just been replaced
if you want it you are welcome to it as I don't think I'll be doing my own powder work as I plan to leave my engine raw unpainted
Message me if interested
Keith
neevo
Over 1,000 Posts
Big amount of not much going on with the 400F at the moment as I'm saving budget to get some headers bent and also looking to buy the motor internals at some point.
However I thought I would get my arse in the shed this afternoon despite having a monster hangover, with the aim of getting the angle grinder out to do some remedial work. A few items on the bike have been bugging me for a while, namely the mounts for the subframe tray. I didn't weld them on very well originally so had to use washers to space them out properly plus they weren't perfectly symmetrical all the way around. So I hacked all but 4 of them off (left 4 as they are the battery box mounts) and I will look to cut some 5mm plate to redo them in different positions:
You can also see the clean tube sections where I removed the exhaust hanger mounts I welded on:
The exhausts will be hung from the upright tubes instead in the same way the rearsets are mounted.
Still got some work to do to tidy up the tubes on the rear of the bike, some flat sections from the angle grinder, not a huge issue as they largely won't be visible, however the uprights will, and they need some attention to get them as round as possible.
However I thought I would get my arse in the shed this afternoon despite having a monster hangover, with the aim of getting the angle grinder out to do some remedial work. A few items on the bike have been bugging me for a while, namely the mounts for the subframe tray. I didn't weld them on very well originally so had to use washers to space them out properly plus they weren't perfectly symmetrical all the way around. So I hacked all but 4 of them off (left 4 as they are the battery box mounts) and I will look to cut some 5mm plate to redo them in different positions:
You can also see the clean tube sections where I removed the exhaust hanger mounts I welded on:
The exhausts will be hung from the upright tubes instead in the same way the rearsets are mounted.
Still got some work to do to tidy up the tubes on the rear of the bike, some flat sections from the angle grinder, not a huge issue as they largely won't be visible, however the uprights will, and they need some attention to get them as round as possible.
neevo
Over 1,000 Posts
Celebrated another year on this earth this week and happy to say I got a few motorcycle related parts:
1. Replacement fusebox as I cracked the screen on the last one
2. Some 5mm fuel tube to finish the taps on the tank
3. Series 1,2 & 3 of Cafe Racer TV which I've seen bits of on YouTube but I'm really looking forward to watching them
4. Black billet single pull throttle tube, just need to get the grip off the old one
Plus some new goggles and gloves for the dirty. Good year!!!
1. Replacement fusebox as I cracked the screen on the last one
2. Some 5mm fuel tube to finish the taps on the tank
3. Series 1,2 & 3 of Cafe Racer TV which I've seen bits of on YouTube but I'm really looking forward to watching them
4. Black billet single pull throttle tube, just need to get the grip off the old one
Plus some new goggles and gloves for the dirty. Good year!!!
stroker crazy
crazy as a fox
Many happies neevo!
Crazy
Crazy
stroker crazy
crazy as a fox
If it wasn't for the prezzies, I would of given up having birthdays years ago!
Crazy
Crazy
