October 31st, 2014, 05:50 AM | #1 |
KAWASAKI GURU
Name: Shawn
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Has anyone measured the ACTUAL compression ratio?
Just like the title states has anyone actually measured the combustion chamber and piston, etc. of the 08-12 250r to find out the actual compression ratio?
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October 31st, 2014, 06:24 AM | #2 |
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No
For me it changed from stock after the head is polished. To do it You need a cc measuring set up. And a third grader with a calculator to do the math. A Thread on how would be great. I would be interested to see what they are.
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October 31st, 2014, 06:42 AM | #3 |
KAWASAKI GURU
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I've done it on some other bikes before I just didnt want to tear into this engine :-/ but I do have a spare so yeah thats good.
Racer X I may have some up with a VERY cost effective way to lower our compression :-) |
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October 31st, 2014, 06:53 AM | #4 |
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Sub'd
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October 31st, 2014, 07:06 AM | #5 |
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You should be able to measure the compression ratio with a simple compression gauge. You know what atmospheric pressure is to a pretty good degree, so screw in the gauge, measure the greatest pressure, and take a ratio of the two. Make sure to close your petcock or disconnect the injectors beforehand. Do it a few times and you can build up an idea of the uncertainties inherent in the gauge you're using.
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October 31st, 2014, 07:27 AM | #6 | |
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Quote:
CR=(displacement + CCV)/CCV A lot of (auto) road racing bodies set a max compression ratio, they have this burette looking thing at the shop my brother co-ops in that they use to meter the water into the combustion chamber.
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October 31st, 2014, 07:36 AM | #7 |
ninjette.org sage
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It's not perfect, but treating the air like an ideal gas and assuming isothermal compression (not really reasonable assumptions, but probably enough to get you to within a few percent), the ratio of compressed to uncompressed pressures does give the compression ratio.
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October 31st, 2014, 07:44 AM | #8 | |
KAWASAKI GURU
Name: Shawn
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Quote:
I just might have to do this myself but I've done it before its really not that bad although I forget how I measured the piston side.... Plexiglass with a hole in it, grease around the combustion chamber and a syringe with water. I just looked online and they do the same thing with the piston but with the piston in the hole. |
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October 31st, 2014, 08:25 AM | #9 |
wat
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on the 40cc bikes we put sillicone down the spark plug hole at tdc and then disassemble, remove and weigh it to calculate a volume, then you can do basic math for the rest of the cylinder
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October 31st, 2014, 08:26 AM | #10 |
KAWASAKI GURU
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I sent out some eamils to JE and Wiesco hoping they would be willing to give me atleats the Piston Dome Volume but I doubt they would lol.
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October 31st, 2014, 09:27 AM | #12 |
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I wish I could say. I am going to start with 12.5 to 1 and polish the piston tips to remove sharp edges and the same with the head. This should be 11.8-12 to 1. I don't know how much you need to spin the turbo. But I know if the engine has less than 125 psi compresson it will not start.
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October 31st, 2014, 09:36 AM | #13 | |
KAWASAKI GURU
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10-4 well I Wiesco got back to me and sent me this:
Quote:
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October 31st, 2014, 09:51 AM | #14 |
KAWASAKI GURU
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OK @Racer x here is what I was thinking for lowering the compression.. Obviously we know we can get a set of custom pistons made which that will be a nice $1,900. We can also run a spacer under the cylinder as well a .080" spacer should lower it by about 1.5-2 points I believe but wed probably need adjustable cam gears.
How about this idea..... Ninja 300 rods? They are about 2.8mm shorter, I did some rough calculations and I think it might drop the compression to much, like down to 7-7.5:1... so if we ran the 300 rods with 12.5-13.0:1 pistons it might bring it up to the 8.5-9.0:1 ratio we'd be looking for without having to run block spacers and such? Benefits - Newer (possibly stronger) rods, little thicker on the small end and youd get a forged piston with it. Sorry all you N/A guys I'm trying to think of ideas for the turbo setup :-p |
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October 31st, 2014, 09:54 AM | #15 |
KAWASAKI GURU
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Know what else I just thought of, looking at the ninja 300 piston, they moved the pin location UP which means the piston would actually sit lower in the block.... HMMMMMM
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October 31st, 2014, 10:25 AM | #16 |
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I would not do the 300 rods myself. I have Carillo rods and love them. And if you go with custom Pistons. I have a good friend ,John Noonan at Wossner that can make custom Pistons. And he knows land speed racing.
If you want to go with thicker gaskets. Thick copper is good. Head gaskets.com has the pattern already and I have the gaskets. Ask to speak to Mordy Dunst. The cam timing would have to be adjusted for the taller head distance.
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October 31st, 2014, 11:11 AM | #17 | |
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Quote:
Here's some interesting reading on the subject - http://www.xcceleration.com/cr-boost%20101.htm |
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1 out of 1 members found this post helpful. |
October 31st, 2014, 11:18 AM | #18 |
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My plan because I am running at high altitude is high compresson low boost. And that chart says 11 to one with 7.5 lb of boost is about 17 to 1 and that is what I want. And why j have Carillo rods
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October 31st, 2014, 11:21 AM | #19 | |
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Quote:
This thread prompted me to pretty-up a spreadsheet I put together when I put up this thread https://www.ninjette.org/forums/show...ht=compression. If anyone is interested I'll attach the live spreadsheet Looks like (and this is assuming the new gen bore/stroke/CR is the same as the pregen) you need about 60 thousandths (1.5 mm) to get to a 9:1 CR. So about half what the 300 rods would get you. So if you can put your hands on a 0.060" gasket to run under the cylinder you'll be there. Although like Racerx points out, we have no idea whether it will start, etc at a 9:1 CR. What do the turbo 'Busa guys run for CR? I'm wanting to go the other way, by shaving .0125" off the block it will put the CR right at 13.5:1.
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October 31st, 2014, 11:50 AM | #20 |
KAWASAKI GURU
Name: Shawn
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Yeah I cant justify the cost of Carrillo's with these engines being so cheap ya know.
As of now I'm going to stay with stock compression and head studs and E85. But I was considering with the spare engine doing a lower compression and more boost. I might pick up some 300 engine parts for cheap and measure everything out and see what combinations I could use. The 300 has 10.6:1 compression so those pistons might drop it to much with the piston dome and the pin relocation |
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October 31st, 2014, 01:02 PM | #22 |
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Yeah sure can. Same bore and stroke?
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October 31st, 2014, 01:04 PM | #23 |
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Crap laptop battery is dead it'll have to wait till after trick or treating.
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October 31st, 2014, 01:05 PM | #24 |
KAWASAKI GURU
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yup, how did you figure that CC Volume?
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October 31st, 2014, 01:06 PM | #25 |
KAWASAKI GURU
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October 31st, 2014, 01:08 PM | #26 |
ninjette.org guru
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(Displacement + CCV)/CCV = CR, I don't remember how but you just solve for CCV.
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October 31st, 2014, 01:11 PM | #27 |
KAWASAKI GURU
Name: Shawn
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OK I got ya, so that should 15.55cc's should be the piston volume and combustion chamber volume.... hmmm very interesting!
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October 31st, 2014, 02:06 PM | #28 | |
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Quote:
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October 31st, 2014, 02:16 PM | #29 |
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This is some photos of the gaskets. The copper one is .040 abot four times the thickness of stock.
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October 31st, 2014, 03:50 PM | #31 | |
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Quote:
the 300 rods are indeed stronger and beefier at top end...using a couple of forged on top of them would be ideal... I had told you that when you first presented your idea but you had rejected it as being expensive for your project... the cheap version would be to keep stock rods and get a 300 aluminum block and pistons....the serious drawback is that the pistons are cast but on the other hand you have much lighter pistons and pins (about 10 grams less reciprocating weight on each cylinder), flat crown and better heat dissipation.... don't make it too powerful Shawn !! I am jealous already.... PS: it is really easy to make stock cam sprockets adjustable...
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October 31st, 2014, 04:37 PM | #32 | |
KAWASAKI GURU
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What I was trying to see is if I Could use just one part for the project like the rods or the pistons, sort of a drop in and go kinda deal, the rods would have been the best... maybe I Should start looking at other bikes rod dimensions to find out what would work. |
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October 31st, 2014, 04:49 PM | #33 |
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Forged Pistons are pretty important. J had no trouble smashing holes in forged Pistons and compressing ring lands. I would hate to see what would happen with cast Pistons.
The stock rods are good to 120 hp according to some people I have talked to.
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October 31st, 2014, 04:50 PM | #34 |
KAWASAKI GURU
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Was that on nitrous?
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October 31st, 2014, 09:35 PM | #35 |
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With my old system. The new syst does not do damage like that
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October 31st, 2014, 11:06 PM | #36 |
ninjette.org guru
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7:1 - 96psi
8:1 - 117psi 9:1 - 139psi 10:1 - 161psi 11:1 - 184psi 12:1 - 208psi You allow 60% ve at cranking speed |
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November 1st, 2014, 02:04 AM | #37 | |
modaholic junkie
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the '00 gen definetely is compatible in terms of top end since the piston pin is the exact same as for the 250 !! I' d appreciate some feedback on your findings since I might end up doing sth like that myself...don't forget to weigh them too !!
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November 1st, 2014, 05:40 AM | #38 |
Long Time Rider
Name: Blue
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Has anyone looked at reducing the flywheel weight for a slight HP gain?
http://www.xlitemoto.com/products_de...b3a9dd432.html |
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November 1st, 2014, 09:41 AM | #39 | |
ninjette.org guru
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Quote:
So go from 0.010" head gasket to 0.040" copper, and a 0.020" (maybe get copper made too?) cylinder block to crankcase seal and you're there.
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November 1st, 2014, 01:00 PM | #40 |
KAWASAKI GURU
Name: Shawn
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Thank you sir! Yeah I think I need to scrap this 300 rod idea, if they were maybe only 1mm shorter it would work but yeah to much.
I'm gunna stick to stock stuff for now! @Racer x I dont doubt nitrous did that to those pistons! Nitrous is a lot harder on pistons than boost. |
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