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700cc Big Bore DR 650

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Anyone done a decent amount of miles on high cc or high comp upgrades???

I realy dont want to loose the reliability...much....

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I have a request in for Dyno time at a local race shop.. I plan to have them do a before and after run. My current setup is Mx_Rob flatslide, FMF Q2, header grind, Airbox mod and twin air filter.

Tomorrow I'm installing the Sidewinder 520 chain conversion with titanium alloy sprockets. The front sprocket has one extra tooth.. not sure how that may affect dyno numbers if at all. I will post to the group once I have all the data.

The after run will be post JE High Comp piston install with Web cam #223 grind and hopefully some head porting.

Gary

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I have a request in for Dyno time at a local race shop.. I plan to have them do a before and after run. My current setup is Mx_Rob flatslide, FMF Q2, header grind, Airbox mod and twin air filter.

Tomorrow I'm installing the Sidewinder 520 chain conversion with titanium alloy sprockets. The front sprocket has one extra tooth.. not sure how that may affect dyno numbers if at all. I will post to the group once I have all the data.

The after run will be post JE High Comp piston install with Web cam #223 grind and hopefully some head porting.

Gary

dyno #'s are unchanged by gearing.

+1 tooth in the front is gonna be quite a change, are you gearing for the highway or something?

hopefully some porting? who's doing the porting & why is it in question?

one porting job can vary vastly from another!

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dyno #'s are unchanged by gearing.

Not true. Higher gearing will have more losses through tire-to-roller friction, chain friction, even frictional losses due to spinning the roller faster. Some dynos and dyno software are better at compensating for these losses than others. You can almost always generate slightly higher numbers by running in a lower gear.

One thing that's important is to be consistent. If you intend to do before and after dyno runs make sure you do them with the same gearing, same tire and tire pressure, etc.

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Not true. Higher gearing will have more losses through tire-to-roller friction, chain friction, even frictional losses due to spinning the roller faster. Some dynos and dyno software are better at compensating for these losses than others. You can almost always generate slightly higher numbers by running in a lower gear.

One thing that's important is to be consistent. If you intend to do before and after dyno runs make sure you do them with the same gearing, same tire and tire pressure, etc.

my mistake!

I've always heard that the dyno is unaffected by gearing, it does not use your rpms to calculate HP/torque but goes by how fast the drum is rotated.

is this not true?

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Sure, that's all true but a chassis dyno measures the actual power that rotates the roller. There are always some frictional losses between the crank and the tire. Those losses will be larger at 100 mph (8000 rpm in 5th) than they will be at 60mph (8000 rpm in 3rd) so in 3rd the dyno will measure more power. Not a lot, but on a DR650 it might be equal to a couple of horsepower.

There has to be RPM data to calculate torque. Some dynos can give horsepower numbers without RPM data. Mine doesn't, it has to have an RPM input or RPM calculated by speed.

A sophisticated dyno setup can measure those losses by doing 'coast down' runs and then compensate for the difference.

None of that matters if you if you always test in the same gear, run the same tire pressure, etc.

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The reason I am unsure about head porting is because the dyno shop I've contacted hasn't called me back yet.. The shop is Steve Johnson (NHRA Pro stock racer).. They are currently still out on the road but will return next Thursday. They've done work for me in the past on my V-max. I know they have a flow bench so I'm sure they will/can do the head porting. Secretary says season is over next week after some awards banquet so I expect a call back soon after.

His shop is just a few miles from where I live. They love doing this type of work in the off-season so I'm expecting great results.

Gary

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don't know about his shop, but steve is a great guy.

Hi shop is nice.. they built a custom airbox for my V-max and did a great job.. also dyno tuned it. He has a flow bench so I hope to get the DR head worked.

Gary

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this is a cool thread. I bought a spare head earlier this year just to try and get something like this done. It's gotta make a difference. I've got an FCR39, full FMF system on my 1998. It's got over 50k km on it now. I bought a used 670cc kit on ebay. it's in great shape and thought about the webcam. i don't want a high rpm motor. I love the DR power but more is always better. I'm curious how the webcam changes the power. Also we have crap gas here in Brazil so I don't wanna bump up the compression too much. I can always convert to alcohol. what's a port job cost?

cheers,

Brian

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this is a cool thread. I bought a spare head earlier this year just to try and get something like this done. It's gotta make a difference. I've got an FCR39, full FMF system on my 1998. It's got over 50k km on it now. I bought a used 670cc kit on ebay. it's in great shape and thought about the webcam. i don't want a high rpm motor. I love the DR power but more is always better. I'm curious how the webcam changes the power. Also we have crap gas here in Brazil so I don't wanna bump up the compression too much. I can always convert to alcohol. what's a port job cost?

cheers,

Brian

Not sure what the head porting will cost.. soon as I hear from the race shop I will let this thread know the cost etc.. I asked a lot of questions before purchasing the high comp piston and cam as I too did not want a top-end monster. Of those I spoke to who had done this mod said it made the most difference down low and in the mid-range where you want it.

I'll be installing the stainless header tomorrow which has been jet-hot coated.

JetHot1.jpg

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this is a cool thread. I bought a spare head earlier this year just to try and get something like this done. It's gotta make a difference. I've got an FCR39, full FMF system on my 1998. It's got over 50k km on it now. I bought a used 670cc kit on ebay. it's in great shape and thought about the webcam. i don't want a high rpm motor. I love the DR power but more is always better. I'm curious how the webcam changes the power. Also we have crap gas here in Brazil so I don't wanna bump up the compression too much. I can always convert to alcohol. what's a port job cost?

cheers,

Brian

the web cam made a lot of difference it did move the power higher in the rpms but only about 1000rpms & didn't lose any on the bottom so overall it added 1000 to the power band & seemed to make more power all the way through.

highly recommended.

a port jobs' cost will vary depending on where & who does the work.

like wise the quality of the port job can vary considerably. choose wisely.

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I got the head back from the machine shop this afternoon & will hopefully have it all back together tomorrow for a test ride!

here's a couple of pics, 1 before & a few from today.

as you can see in the last pic I had about all I could (about .045) milled from the head without eating into the intake seat.

if I want to increase compression further I'll need to get a custom piston made.

BigBore083-1.jpg

BigBore165.jpg

BigBore148.jpg

BigBore163.jpg

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I purposely left the combustion chamber untouched.

the valves are hardly shrouded in this head & the only reason to polish the combustion chamber is to help prevent detonation, so far that hasn't been a problem.

mainly, any material you remove from the combustion chamber, for any reason, only serves to lower the compression ratio. so unless I see an advantage to be had, I've learned to just leave it alone.

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I purposely left the combustion chamber untouched.

the valves are hardly shrouded in this head & the only reason to polish the combustion chamber is to help prevent detonation, so far that hasn't been a problem.

mainly, any material you remove from the combustion chamber, for any reason, only serves to lower the compression ratio. so unless I see an advantage to be had, I've learned to just leave it alone.

One reason to polish the combustion chamber is to decrease the surface area which will lessen heat transfer into the head casting. Less heat escaping through the head can translate to more power output and a cooler running motor. I think it is a good idea to polish the top of the piston for the same reason.

Polishing doesn't remove much material so the effect on the compression ratio is minimal.

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One reason to polish the combustion chamber is to decrease the surface area which will lessen heat transfer into the head casting. Less heat escaping through the head can translate to more power output and a cooler running motor. I think it is a good idea to polish the top of the piston for the same reason.

Polishing doesn't remove much material so the effect on the compression ratio is minimal.

the combustion chambers that I've seen (DR included) are pretty rough & require quite a bit of material removal to get a polish. IMO

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Weighed the JE piston and pin today. This was done on medical grade scales at one of the Genetics labs where I work:

Piston 370.18g

Pin 118.41g

Gary Spradley

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that's about what Jeff came up with, still way lighter than stock.

how's your project coming along?

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that's about what Jeff came up with, still way lighter than stock.

how's your project coming along?

I'm awaiting a call from Steve Johnson racing to schedule dyno time and the install. I know they had an NHRA awards banquet in California and have just returned so they probably want to spend some time at home with family.

Hopefully I will hear from them early next week, if not I'm going to call again.

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