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Discussion Starter #1
Guys, I have been wondering ever since Dynotechjim has done his dyno runs if the F7 carb will actually be FASTER than the EFI. The reason I ask this is because Jim found that once the powervalves open on the EFI the sled gets really fat on top end. He says it could be leaned down significantly and still be safe for long WOT runs (he was getting about 132-133 hp). For the average joe that equates to lost HP and there is nothing we can do about it. The carb on the other hand is strictly a jetting issue and we can lean that down to a certain point to be faster??? than the fuelie (maybe get the claimed 140 hp). ^_^ Remember the only advantage here would be top end because Jim claims the lower and mid ranges are spot on for the fuelie. Is anyone else seeing the same possibility?? Personally I think the EFI is probably better all around. However, if I were to have any doubts at all the carb would be the way to go.... especially for lake runs.

Cat S.
 

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Makes sense to me. I went back and looked at the AMSNOW dyno on the F7 EFI from Cat it had an BSFC of about .68-.69 on top where it made the 140 hp. Something tells me it had a different fuel map from what was delivered. Think of it this way, you get an EFI you hope CAT gets it perfect. You get an Carb and it's not perfect you can always fix it. I have an EFI and am not happy with low end throttle reponse but there is nothing I can do about it.
 

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You need to remember that each dyno is different. Just look at what D&D and black magic are getting with the 600. DT's dyno numbers are always low it seems, and I wonder who is really right. I will stick with GLS on this one and believe that the EFI is the way to go!
 

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This is been argued a 1000 times, if you take 2 stock, same brand cc sleds one efi one carb. the efi will be stronger.
 

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Originally posted by fast 600@Mar 10 2003, 03:13 PM
This is been argued a 1000 times, if you take 2 stock, same brand cc sleds one efi one carb. the efi will be stronger.
you can tune a carb motor more. in the end it will probably be faster then a efi sled
 

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Discussion Starter #7
you can tune a carb motor more. in the end it will probably be faster then a efi sled
Actually that is not necessarily true. Cat can tune an ECU any way they want. They could program it for sno-x or 500' drags 1000' speed runs. They know how much fuel the motor requires to survive at these distances and will run them right to the edge for the racers.

Case in point. Do you think the guys at Haydays hadt the ECU that the 03 F7's have. NO. I know one of the guys that ran at Haydays with the prototype and it was pushing 150 horse......with the drag ECU.

So both EFI and carb can be good. The point I wanted to make is if you buy a carb you can jet it as lean as you think is still safe and makes the most power possible. If you buy the EFI and it's really fat on top you are stuck with it.

Cat S.
 

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you can tune a carb motor more. in the end it will probably be faster then a efi sled
Actually that is not necessarily true. Cat can tune an ECU any way they want. They could program it for sno-x or 500' drags 1000' speed runs. They know how much fuel the motor requires to survive at these distances and will run them right to the edge for the racers.

Case in point. Do you think the guys at Haydays hadt the ECU that the 03 F7's have. NO. I know one of the guys that ran at Haydays with the prototype and it was pushing 150 horse......with the drag ECU.

So both EFI and carb can be good. The point I wanted to make is if you buy a carb you can jet it as lean as you think is still safe and makes the most power possible. If you buy the EFI and it's really fat on top you are stuck with it.

Cat S.
I agree. Sorry, i was talking about the average joe consumer with a little mechanical tinkering ability
 

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Discussion Starter #10
No betting to be done here. A properly jetted F7 at 140 horse will beat a F7 EFI with 132 horse every time. Top end anyway.

Cat S.
 

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If one of the aftermarket companies would come out w/ a reprogrammer or power commander like the motorcycles then the efi would be untamed. I've made many fuel maps for the motorcycles, and the efi is so much better. Too bad cat locked up the ecu. Maybe d&d will come out w/ something.
 

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"Remember the only advantage here would be top end because Jim claims the lower and mid ranges are spot on for the fuelie"

Actually Cat has fattened mid range up by 2-3% on the map on the 04's also :angry:
 

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NO, the carbs are 40s but the throttle bodies are 46mm. Food for thought; The f7s I know of that were grass dragged had a +7 key,which was only safe for the short distance. Also If you think a EFI will be faster or should I say more responsive ask Tucker why his sled has carbs. I am sure Cat would rather sell us a EFI that most of us won't piss with, hence less motor problems,ignoring the dealer related Poofs with it this year.Instead of a carbed one we can easily destroy ??? Mine will be a carbed 04' and it will also be faster>>>>>>>>>>>>
 

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I know that a lot of you guys really do know your way around a sled, and have the ability to actually jet and tune your carbs for optimum performance and reliability. I can respect that.

I also know a lot of guys who think they do.

They are always screwing with them. Always thinking they can tinker another horse out of it.

I figure, if you want a faster one, get a faster one.

More power to you, if you like to tinker anyway, but I just like to ride.

EFI is my vote.
 

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I think a well jetted carbed F7 will be faster on top end but if your running WOT for a long dist. Ill take the EFI Because it wont blow after 4-5 miles wide open on big lakes. I know when we run Craine or Rainy lake we run 15miles at a time WOT and carbs hatch a motor.Reason Tucker runs carbed is because he changes jets,-mains & pilots. Needles& slides.+ his fuel map for short distance. Your always backing out of the throddle so you can run closer to the edge without hurting the motor.
 

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Mine will have Carbs! I rode a few F7s this past year, the throttle response made me sick. Hopefully Cat will have them remapped for 04 because they were way off lastyear. Maybe out of the crate the EFI will win, but you can always easily improve the carbs performance with a simple and cheap jetting change. EFIs, your stuck with what you get unless you want to dish out $300 for another CDI.
 

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I am with you on the carb vs EFI debate. I have a ZR9 with a Varyflow and I love it. We were riding on the weekend in 40F temperatures, I just reach down go click-click and I am jetted down 4 sizes. Perfect for the weather that day. You guys are communicating with people that are unwilling or unable to deal with carb adjustments. Obviously none of them have read Dynotech Jim's assessment of the F7's EFI. HE SAID IT WAS THE WORST EXAMPLE OF TWO STROKE FUEL CALIBRATION ON TOP END HE HAD EVER SEEN. There is 10-20hp being left on the table due to the over rich high speed mixture!!!!! We greasy folk will be riding sweet running carbed F7's next year while the EFI riders are crying in their beer.
Oh yeah, there's a reason the EFI throttle bodies are so much bigger than the carb openings. They have to be, they are full of throttle butterflies and other gobbledegook. All that's in a carb throat at full throttle is one thin needle.

Terry
 
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