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post #81 of 609 (permalink) Old 12-13-2010, 08:01 AM
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SuperSkypilot wrote:
I use Engine Analyzer Pro for my stuff. I had a thread going last yearasking for information that nobody seemed to have. It took quite a while to gather all the data by hand, ...measuring each individual component.


Your post were from before I joined the group and I never saw them. Hopefully we will be able to fill in some more of the blanks . I'm not much of a mathematician but I get frustrated when people aren't willing to look at the whole picture. I have an older Dos program called Desk Top Dynos.

I'm old-school too, but that modeling program has saved me more time and money than I care to think about. I've gone Ken's route out of necessity in the past, asI had no choice. I have collected all of my GL1000 data/figures, and have finished building my engine. I plan to use a chassis dynamometer for final tuning, and to verify the model. I'm certain the modeling is accurate, as I bought and used the program for the last rebuilding of the engine in my Camaro and it was accurate for that build in most respects on a engine dyno. I'll have to extrapolate the results and be happy with the chassis route.

The program takes the guess-work out of the "what if I tried this". Spec'ing everything out for a GL engine is tedious and time consuming work to say the least, but again, enjoyable for those that like it.

Not many offering performance parts for GL1's, but WEB-CAM does some regrinds unless you have a shop that already does this kind of work, in caseany areinterested. Providing specs, they could probably regrind a set of GL-12 cams no problem.


My calculated redline is 10,200 RPM on my build.Theoutput is inits ability to rev...

It will be interesting to see what you find. It's pleasing to see the effort.

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post #82 of 609 (permalink) Old 12-13-2010, 08:04 AM
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This really is 5 star thread and I'm personally enjoying it more than almost any other, even though I doubt if I will ever want to put a 1200 motor in a 1000. The recent deviation into compression ratio measurement has probably been discussed over the years, but perhaps beforeI joined too. I have been modifying Minis (the old Brit ones) for many a year now and have often needed CR measurements. It's really only a matter of accurate measurement and an understanding of what is actually going on in the secondphaseof the suck/squeeze/bang/blow process.

When the piston is at the BOTTOM of the stroke; there is all that volume down to the top edge of the Top piston ring and up to and includingthe combustion chamber (with its valves and plug) which has to be squeezed into just the bit above the Top ring and including again the combustion chamber.

When working out the first bit we must add together the volume in the cylinder plus the small annular volume above the top ring plus the volume of a compressed head gasket plus the combustion chamber volume, with the valves shut and the plug fitted.

Secondly we need to know the volume at the TOP of the stroke byadding together the combustion chamber volume plus the compressed head gasket volume plus (again) the small annular volume above the top ring.

With a dished piston we must also add the volume of the dish to both of the Top dead centre and Bottom dead centre calculations, but in the case of a Wing we must subtract the dome volume.

Measuring the actual combustion chamber volume is fairly straighforward and I used to stick a thin piece of clear plastic sheet to the head face with grease. This sheet had 2 eighth holesin, and by angling the head so that the holes were uppermost, thin coloured oil was dripped into one of the holes (the other is a vent)using a measuring Burette until full. This is now the combustion chamber volume.

The bore volume is simply the bore diameter squared, muliplied by Pi (3.1416) and divided by 4, then multiplied by the stroke length.

The small annular volume is just that little bit between the piston and the bore down to the top ring.

Thecompressed head gasket volumeis quite straightforward but its not normal exactly the same diameter as the bore (a bit bigger to prevent the edge heating and detonating the fuel)

Measuring the piston dome can be done by clamping a thin strip around the piston crown with a hose clip and setting it a know distance above the edge, then filling it with oil using the Burrette as you did for the combustion chamber. This will be less than the volume of the space above the piston crown if it was flat - which can be calculated by using the piston diameter and height of the strip above it - it's just a short cylinder.

The compression RATIO is the that ratio between the big volume at the bottom of the stroke and the volume at the top of the stroke.

So if the above calculations gave figures of 330 ccs at the bottom and 30 at the top, then the ratio would be 11:1.

However, in reality temperature comes into play when you compress any gas so thefigure will not be the calculated one under running conditons - but we have to do the math(s)

Ian and Christine

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post #83 of 609 (permalink) Old 12-13-2010, 09:34 AM Thread Starter
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I cant afford to buy there program so I'm going to get by with trial version for now. I'm still digging out and I just trough a rod on my snowblower so I'm no sure anything will happen today.


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post #84 of 609 (permalink) Old 12-13-2010, 09:42 AM
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mail your motor to me in ravenel and i'll fix it and you can get back to the build:RO FL:
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post #85 of 609 (permalink) Old 12-13-2010, 10:03 AM
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...if the online calculators are of interest, then the Wallace Racing site is the standard..


I was going to post it last night, but their site was down. I haven't used their site for a while and I didn't know what was going on. It's back up now though...

Edit: You won't find these on the Wallace site and I realize that you'll probably stick with the factory carbs, but you implied that options are on the table. I had to find the calcs below because I haven't usedthem for a while either, but if you go with a alternate induction set-up, thissite uses Java and is the best I've found:


The othercalcs are of interest also.


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post #86 of 609 (permalink) Old 12-13-2010, 12:06 PM
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Just found this on an old motorcycle specs site: "In order to increase intake velocity, Honda reduced the intake valves' diameters 2.0mm, to 36mm; the 32mm exhausts are the same as the 1100's. The '84 head uses a combustion chamber with more squish area to centralize the air/fuel charge, and the new GL has slightly more "radical" valve timing and more valve lift. The new 32mm Keihin constant-velocity carburetors follow the pattern of the carbs used in the Honda V-four engines." More confusion, this must be the reason for the smaller dome?
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post #87 of 609 (permalink) Old 12-14-2010, 03:11 PM
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This is cool, and way beyound my expertise in building engines. I will pay close attention to see how things are going only because I have a 1200 standard that I want to make go a little faster. and I am redoing my standard this winter with a few mods.

I am all ears guys.


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post #88 of 609 (permalink) Old 12-14-2010, 05:53 PM Thread Starter
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Today's menu includes a healthy helping of crow.

I CCed the cylinder heads today. Here's how I did. I started with a 4 x 4 sheet of Lexan and a veterinary syringe.

After drilling in eighth inch hole near the top of the plastic I smeared a little bit of grease around the edges of the combustion chamber.

The grease is used to seal the Lexan plate to the head.

With the plastic seated in the grease and the head tilted slightly so that the hole in the plastic is near the top of the cylinder. I filled the combustion chamber with colored water using the syringe. The head was tilted so that any air pockets moved out through the hole in the plastic plate

I recorded the number of cc of water it took to fill the combustion chamber. I repeated this process three times to make sure I had an accurate reading. I repeated this process with the 1200 head.

To my absolute amazement both combustion chambers were about the same size within a CC or so.

I used about the same technique to fill the cylinder with colored water to calculate the volume of the piston dome. With that information in hand I was able to use a compression ratio calculator to determine that the compression ratio with the GL1000 head on the 1200 engine block would be about 9 to 1.

Next I set up a dial indicator to check the lift on both the GL 1000 and the GL 1200 cams. The lift on the GL 1000 was .275 for the intake and .261 for the exhaust. On the GL 1200 the intake lift was .227 and the exhaust lift was .228. I didn't profile the cams and I'm not sure that I will the GL 1000 has substantially higher left on both the intake and exhaust and I doubt that there is anything that could be done to the profile of the 1200 cam that would make it outperform the 1000 cam.

I'm not surprised at the cam profile differences but I would've sworn that the GL 1200 combustion chamber was smaller than the GL 1000. I guess that's why you need to measure everything, looks can be so deceiving.

Tomorrow I'm going to investigate milling a little bit off of the GL 1000 head to see if I can up the compression ratio. I also plan to get to heads refurbished and ready to go.


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post #89 of 609 (permalink) Old 12-14-2010, 06:14 PM
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this is some good news to me as i was starting to think it would be crazy to change to 1000 heads and loosing compression had any benifit ....now i fill better thanks steve this reveald a lot
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post #90 of 609 (permalink) Old 12-14-2010, 11:40 PM
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Ok I'm going to show my ignorance here with a couple of questions.

Are you going to relocate the pulse generator? Or do away with it completely? I was under the impression that it is an integral part.

Isn't the 1200 block wider that the 1000? Will this require major frame modification?

How much of this build do you think could translate to an 1100 frame?

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