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post #1 of 10 (permalink) Old 02-13-2011, 09:11 PM Thread Starter
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New Member to the V-twin forum

Just a quick question and intro. Hi all you thumper owners anyone have an idea what kind of performance High comp. Pistons will have on the RC and how close would it be to the stoiometric rate?

Many thanks Cheers Mate
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post #2 of 10 (permalink) Old 02-13-2011, 10:58 PM
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The high-compression pistons should add more torque.
When using the OEM valves (which have dished heads) the 12.8:1 pistons equate to around 11.4:1.
Only when using HRC or aftermarket valves with flat valve heads does the compression bump to 12.8:1 (due to slightly less cylinder head volume).

If you have a power commander fitted, then it should have been dyno mapped for a 13.2:1 air/fuel ratio which is the optimum power ratio.
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post #3 of 10 (permalink) Old 02-15-2011, 03:19 AM Thread Starter
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Smile High Comp Pistons

Thanks for the reply and info regarding the High Comp pistons.

Cheers Mate
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post #4 of 10 (permalink) Old 02-15-2011, 07:56 PM
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If you have a power commander fitted, then it should have been dyno mapped for a 13.2:1 air/fuel ratio which is the optimum power ratio.
Care to expound a little more on this ar/fuel ratio? I am trying to review a map I have to see where it may need work. Once its warm enough, I will be getting a custom map completed (Quoted $150)



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post #5 of 10 (permalink) Old 02-18-2011, 02:49 AM Thread Starter
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Care to expound a little more on this ar/fuel ratio? I am trying to review a map I have to see where it may need work. Once its warm enough, I will be getting a custom map completed (Quoted $150)
Thats a great price if indeed your getting a custom map. Who is doing the mapping? How are they going about that exactly? Either they are data logging from a wide band O2 and making small adjustments in the air fuel map or they plan on tuning via dyno runs. The stoiometric (13.8-1) ratio is the best ratio for N/A machines and from what I understand is the closer you can get to that rate of 13.8-1 ratio the more power you will have, fuel economy will be sacraficed but they can tune it for a proper balance of power and fuel economy. The biggest concern I would have with a custom map is the tuner. Its very hard to find someone who really has a though understanding of the dynamics of tuning but with everything there is risk. Dan Kyle racing is a very good source for a proper tune with the RC's. Hope this helps and anyone who has any more info please don't hesitate

Cheers Mate
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post #6 of 10 (permalink) Old 02-18-2011, 02:51 PM
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Care to expound a little more on this ar/fuel ratio? I am trying to review a map I have to see where it may need work. Once its warm enough, I will be getting a custom map completed (Quoted $150)
The stoichiometric or chemically perfect air/fuel ratio for complete burning of gasoline is 14.7:1.
However that is only in a laboratory environment.
It's way, way too lean for an internal combustion engine.

The ideal air/fuel ratio for best power is 13.2:1.
You should strive to have that ratio across the board on your mapping.

As the air/fuel ratio starts to climb, you'll start to lose more and more power and if the ratio gets lean enough, the engine will even start to misfire or die.

If kept at a very lean state for some time, it may even start to melt the piston crown and/or spark plug.
This was a somewhat frequent occurrence in the 2-stroke racing days.
Sometimes it was caught in time, sometimes not, with a hole melted through the piston center.

If you pull your plugs and see a white insulator with gray specks, those specks are melted aluminum form the piston from overheating due to very lean condition.
You may also see melted electrode and porcelain on the plug insulator also.
This is very rare these days with fuel injection, especially systems that use a lambda sensor to measure oxygen content.

But since one can alter the air/fuel ratio with a power commander or similar systems, you can enter a too lean state if you mis-adjust the mapping.

Usually the ideal plug color is a tan or light gray color (usually tan).
Tan is a perfect ratio with light gray a tad on the richer side.
Any lighter or darker color shows which side the air/fuel ratio is at.

Here's one of my plugs from a previous mapping showing the tan color at the tip.


Here's a plug I pulled from my last valve check and plug replacement.

It's a bit of gray indicating it's running a tad on the rich side.
This is with the correct plug heat range. I'll take care of this on the next re-map session.
Also, if you run a cooler plug heat range and not get it up to proper temperature, then it may incorrectly show a darker color.
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post #7 of 10 (permalink) Old 02-18-2011, 08:45 PM
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Thread Jack LOL,,,,,,,,,,, Sub do you have your own dyno? How do you adjust your PC without a dyno?

2004 RC51 with multipul mods
1985 VF1000R SOLD 😭
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post #8 of 10 (permalink) Old 02-19-2011, 11:41 PM Thread Starter
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Led Blinker relay wiring?

I bought a Custom LED electronic led flasher relay but the problem is the relay has only two wires, red and black. Now I know that the OEM regulator has three wires on it and I am assuming that there is one constant 12v power source when the key is in the on position and one wire that pulses 12v, then the ground. The installation instructions tell you to wire the red wire with the constant 12v key power and the black wire to the pulsing intermitant 12v so do I just ground the last wire to the subframe or battery or anywhere. I don't want to blow anything or fry some wires so I am trying to clarify before I start cutting wires. Any one have suggestions?

Thanks
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post #9 of 10 (permalink) Old 02-20-2011, 08:17 AM
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Originally Posted by araipilot View Post
Thats a great price if indeed your getting a custom map. Who is doing the mapping? How are they going about that exactly? Either they are data logging from a wide band O2 and making small adjustments in the air fuel map or they plan on tuning via dyno runs. The stoiometric (13.8-1) ratio is the best ratio for N/A machines and from what I understand is the closer you can get to that rate of 13.8-1 ratio the more power you will have, fuel economy will be sacraficed but they can tune it for a proper balance of power and fuel economy. The biggest concern I would have with a custom map is the tuner. Its very hard to find someone who really has a though understanding of the dynamics of tuning but with everything there is risk. Dan Kyle racing is a very good source for a proper tune with the RC's. Hope this helps and anyone who has any more info please don't hesitate

Cheers Mate
Flatout in Indianapolis quoted me $150. It will be adjusted on a dyno.



The very first schoolbook that was written had God all over it. --Dave Mustaine
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post #10 of 10 (permalink) Old 02-20-2011, 05:47 PM
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Thread Jack LOL,,,,,,,,,,, Sub do you have your own dyno? How do you adjust your PC without a dyno?
I wish I had my own dyno (of course the neighbors may disagree).
My local dyno shop charges full price for the initial dyno mapping, but half price for subsequent re-mappings.
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