Raptor Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Hey There,
Can anyone tell me if I need a re-map after installing this 734cc big bore and everything else is stock.
Thanks.
Jarrad
 

·
I may be getting older, but I refuse to grow up!
Joined
·
10,800 Posts
NO, your changing cylinder volume, not intake or exhaust. Intake and exhaust changes are what affect the air/fuel ratio.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #4
NO, your changing cylinder volume, not intake or exhaust. Intake and exhaust changes are what affect the air/fuel ratio.
Thanks,
I just thought that the change in cylinder volume would change the air fuel ratio but if you are sure it's right I'll send it out soon. It's my first rebuild on the old girl and I'm racing in Australia's biggest off road race for my first race ever. The Finke Desert Race. I'm super pumped.? Hard to find any quad bike racing in Aus.
 

·
I may be getting older, but I refuse to grow up!
Joined
·
10,800 Posts
I don't know what you're current map is or if it can be improved on. What tuner are you using?
 

·
Registered
Joined
·
323 Posts
  1. I can tell you for 100% confidence, If you put just a BB on a carburetor engine with no other changes, the jetting will need to be leaned out on the main jet. The BB will provide a stronger signal to the main jet and pull more fuel. FI engines do not rely on a vacuum signal to pull fuel like carburetors. Keep this in mind for future use if ever working on a carb application.
 

·
I may be getting older, but I refuse to grow up!
Joined
·
10,800 Posts
A fuel controller should always be the first modification.
 

·
Registered
Joined
·
58 Posts
I just put a 745 kit on mine with auto tune and will find out but i can't see how i wouldnt have to richen it up. The cylinder will be pulling in more air and will need more fuel to go with it. A carburetor relies on a vacuum signal and mixes accordingly so it compensates to some extent. I know for a fact that fuel consumption on a big bore carb bike goes up!
 

·
Registered
Joined
·
323 Posts
On the BB engines I have built in the past, I go down 1-2 sizes on the main jet. I have yet to build a BB FI engine. Call one of the popular Raptor engine builders and get their advice.
 

·
Registered
Joined
·
58 Posts
The only way it wont need more fuel to go with more air that the big bore needs is if the intake air pressure sensor is seing the higher vacuum on the intake and adjusting the fuel amount to compensate which is possible...
 

·
Registered
Joined
·
58 Posts
Heres an update on the PC5 following my 745 upgrade. The picture shows just the fuel adjustments made after 5 miles of riding using autotune. Its definitely richening it up in the midrange so far. Again, the picture is only the changes made to the already enrichened map for previous mods.
 

Attachments

·
I may be getting older, but I refuse to grow up!
Joined
·
10,800 Posts
NO, your changing cylinder volume, not intake or exhaust. Intake and exhaust changes are what affect the air/fuel ratio.
Haha, who told you that? Haha
Air in, air out. If the fuel injected motor is set to say, 14 parts of air to 1 part of fuel, that requirement stays the same, no matter if the cam, valve size, porting, compression or cylinder volume are changed.
 

·
Registered
Joined
·
58 Posts
With porting, increased cam lift and duration and increased displacement, you affect air flow. Thats the whole point of doing them. You need to compensate by adding fuel. I can also show you the changes in fueling after i had cuervo do the porting, +1 valves and 5050 cam. The enrichment was huge. Agreed that compression changes shouldn't change a/f as that doesn't affect air flow.
 

·
I may be getting older, but I refuse to grow up!
Joined
·
10,800 Posts
With porting, increased cam lift and duration and increased displacement, you affect air flow. Thats the whole point of doing them. You need to compensate by adding fuel. I can also show you the changes in fueling after i had cuervo do the porting, +1 valves and 5050 cam. The enrichment was huge. Agreed that compression changes shouldn't change a/f as that doesn't affect air flow.
I agree, porting, lift, duration, and displacement affect air flow, and/or velocity. Using a MAF, TPS and ECU the A/F ratio is kept at the target 14:1 fuel ratio as it goes thru the throttle body..
 
1 - 16 of 16 Posts
Top