Wednesday, 22 March 2017

Crude formula to calculate boost

... for (non-360 degree) twin engines and fours like VW-flat twins. In reality you have to figure in a lot more variables, but just to make a rough guess, whether the supercharger needs to be over- or underdriven or simply be reduced to a mechanical hairdryer, because you have to spin it so much faster than it was intended to.

... that's of course meant to say - 14.7


Now let's have a look at the Eaton M45 setup on the TR1 and use the formula above:

Supercharger displacement: 45 c.i. ~ 737cc
Engine displacement of my TR1.1 engine: 1063cc = 531.5cc
Ratio: 1:1 = 1

Result: 5.6PSI

There's quite a few reasons, why in real life you (most likely) won't see exactly this figure:
1) engine efficiency and blower-efficiency are blatantly ignored in this formula
2) blower efficiency varies with blower RPM
3) overall pressure has simply be assumed to be 14.7PSI and varies greatly with altitude

Assuming that we roughly hit the numbers calculated above, why can't we spin the blower faster and faster or why can't we simply use a much bigger blower.  As with every mechanical machine, there's friction and all sorts of losses involved. Friction being one of the main contributors (among the work of compressing air. Luckily supercharger-manufacturers usually provide spec sheets, outlining where the "efficiency island" is in the pressure map and even more importantly where the redline for a supercharger is. This redline basically marks the point, where your blower turns into a mechanical hairdryer and only pumps hot air into the engine. (Incidentially on an Eaton M45 this is 16,000RPM, just to give you an idea!) On the other hand, a blower needs a certain minimal RPM to actually pump air efficiently, which is why you can't simply fit an Eaton M90 and then only run it on half engine speed and expect it to work somewhat efficiently. And as if this weren't enough, add the fact, that you have to apply some power to actually drive the supercharger, which can actually go up into the two-digit horsepower figures with said Eaton M90.

I hope you find this post (mildly) useful and I'd love to see/hear/read about at least one supercharger build one day that was sparked by this post outlining that it is a lot less of a dark art as some professional companies try to make you believe...

Tuesday, 21 March 2017

TR1 (non-stock) breather routing

This one was asked for by David from Oz as I have commented a few times on how I have modified my breather setup to reduce oil-loss through the breather, as the set of pistons I currently run actually already have a bit of blow-by at high rpms (over 7k).

As you can see (unlike stock) I use a long tube that goes over the back of the frame and down into a breather filter. The step rise is there to have the condensed oil run back into the engine, whereas the water vapour will just be blown out. The same system (and inspiration) can be seen on old Guzzis, Yamaha SRs/XTs (that's where I go the idea from) and old classic superbike Kawa Zeds and Suzuki GS thous. Which also somewhat means there has to be a grain of truth in it...



This is by NO MEANS a branded filter, but it doesn't have to be. It's surface is a multitude of the cross-sectional area of the breather tube, so even if it might not flow as well as a K&N or any other branded filter, it will EASILY be good enough. And honestly, the filter is only meant to prevent dirt from getting into the engine, so it doesn't have to do much really. 


I hope this answers all the breather-related questions, if you still have any or noticed other mods that you absolutely want to see a post about, let me know via mail or just write a comment below and I see what I can do about it.

Sunday, 19 March 2017

Eaton M45 on a TR1, perhaps?

I am of course not (yet) admitting that there will be a new project, but a potential project has already been christianed "Project Super TR1".

This post is mainly meant to give you an idea on the overall dimensions of an Eaton M45. And the next post will give you a *VERY* crude formula to work out supercharger sizing for your engine and thereby outline, why an M45 is about the right size for an 1100cc V-twin, but too big for a 1000cc inline four.

Let's dive into it then: The Eaton M45 I use, is out of a early 2000s Mercedes C180/200 Kompressor and goes by the Mercedes part no: A 271 090 20 80 or Eaton 307961.



By the way this is what you'll usually find, when you buy one from a wreckers:



As a matter of fact, only the portion in the red box is the actual supercharger. It measures approx. 250 by 180 by 130mm (length, width, height). An M62 is the same width and height, but is substantially longer and the M62 has got an electro-magnetic clutch behind the pulley, which is also the easiest way to find out which model the supercharger is that you're looking at. The other thing to note: This particular Eaton blower spins clock-wise and the pulley is roughly 71.5mm in diameter.




The following pictures are merely to illustrate how I took the measurements.







In the next post, I'll outline a *VERY* crude formula for guesstimating (I won't go as far as call this a calculation) supercharger-sizing in relation to engine size and thereby calculate also the resulting boost.

Friday, 17 March 2017

Guzzi V65 TT exhaust build

Now this exhaust build was an interesting challenge, as all I had was a badly scanned photography of the old factory V65TT-C.

The first tricky part was, that room in the cylinderhead was very limited and the exhaust pipe had to be necked down to 32mm.





Next step was to weld up some of the tubing in order to have some bits to play around with.




Then it's time to play a bit of Lego and puzzle the bits together to ressemble an exhaust.







And that's what it looked like in the end (all in all about two weeks from the start).



Tuesday, 14 March 2017

The XS Triple Sidecar - Earles Fork (part 1.1)

... or tidying up. As you might have noticed, there hasn't been a post in a few days, mainly because uni has started again and I am current spending quite a bit of my spare time on building an exhaust for a Guzzi V65 TT for a friend's dad.

Even little progress is progress, now the forks are wide enough so that the brake-caliper mounts fit in as well, just have to build them. 




Maybe there's some time on the weekend to make a bit more progress!

Saturday, 4 March 2017

Everyday TR1 - an update and a bit of an outlook

This week was busy, unfortunately for you, not in a bike-sense. On my eighteen year old Volvo V70 station wagon one of the drive shaft bearings gave up and I had to improvise a bit to get it back on the road.

On the upside this meant the old Everyday TR1 had to be quite quickly pushed back into everyday service. (Hence the name!)

That being said, VM38 jetting is now spot on: #17.5 pilots, #145 mains and air-screws 1/2 turn open, which goes lovely with those equal-length 1 3/4" header-exhaust.


As the title suggests, there's also a bit of an outlook involved: A while ago I bought two BT1100 Bulldog engines for spares and as I sold of one of them, I took the following pictures. With a spare set of TR1-crankcases I plan to build an updated version of the current engine. The (planned) specs are going to be as follows:
  • BT1100 crank (lighter than the current XV1100 crank)
  • BT1100 cylinders (they are Nikasil plated) and pistons (more modern slipper design)
  • XV750 cylinder-heads (to bump up compression)
  • BT1100 transmission (because of the longer 5th gear)
  • 9 disk clutch

The used engine, parts donor:





The combustion chamber volume is even bigger than the stock TR1 heads, which lowers the compression ratio even further to a whopping 7.8:1. (Which is nice for turbo use, but useless on a n/a bike!)


Almost 80,000km on the clock and the hone marks are like new. I hope the second engine is as good as this one. 



Luckily the current XV1100-based engine is running nicely, so there's no real pressure to rush this job and I can take my time to build this engine right, to release its full potential.

Oh and if you have a set of XV700 heads for sale, please feel free to contact me and include some pictures of the heads.

Monday, 27 February 2017

XT500 rewiring or why there's no part 2 of the earles fork story today

If you ask people about me, they will most likely tell you that I am a mighty friendly guy, who, if asked politely, will most certainly "have a look at it", which more often than not, leads to fixing stuff. And that's just what happened. My mate Philipp called me and asked me (tongue in cheek), whether I knew a thing or two about rewiring XT 500s as his had literally the worst wiring loom installed I have ever seen.

As he bought everything new, it was a pretty simple and straightforward process to be honest and the pictures will only show you a few spots where you have to have a second look at things.

Space in the headlight shell comes at a premium, so make sure you route everything as snug as possible.


There's two single yellow and green cables, those are high- and low-beam no matter what colour they are on the aftermarket reflector.


Same goes for ground (black on the loom) and blue-red for the pilot light and green is ground for the main bulb. 


Rear is straight forward, green is the left indicator charcoal is the right indicator. 


As we did a 12V-conversion with a Roebi-Regler (google it, this thing's the dog's danglies for XTs and other 6V Yamahas), things came out a bit brighter than stock...



Oh and, no it's very unlikely there'll be much of an update on the earles forks tomorrow either, because my car (trusty old Volvo V70 station wagon) killed on of its driveshaft bearings and I have to do that next...