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NeeD 4 SpeeD
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5,447 Posts
Discussion Starter · #1 ·
hey guys , i got an arrow full system. its 4-2-1 and its killing the low end power .
i read ivans website and it says that his jets wont solve the problem for 4-2-1 systems , is there a way to bring back the low end?
 

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Born to do trackdays
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390 Posts
Nope, it's gone with that setup. Some 4-into-1 systems do better at keep the low end, than others, but the 4-2-1 you have no chance.

Regardless of the system or the configuration, the fact that the EXUP is gone, is probably the reason, more than anything else.
 

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NeeD 4 SpeeD
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5,447 Posts
Discussion Starter · #5 ·
i never rode a bike with an akra system , so , changing it to akrapovic 4-1 with ivans jets will bring the low end to normal?
 

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THE MAN
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3,750 Posts
no matter what full system you put on a 98-01 R1 you are going to loose low end power and smoothness, and often that ability to use large throttle openings at low rpm in a higher gear.

Thats the nature of these bikes.

I have done to many of these bikes to remember, as well as still owning and riding my own 00 R1 with the Ivans/Akra/air box MOJO equipped bike.
 

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NeeD 4 SpeeD
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5,447 Posts
Discussion Starter · #7 ·
no matter what full system you put on a 98-01 R1 you are going to loose low end power and smoothness, and often that ability to use large throttle openings at low rpm in a higher gear.

Thats the nature of these bikes.

I have done to many of these bikes to remember, as well as still owning and riding my own 00 R1 with the Ivans/Akra/air box MOJO equipped bike.
dang, no longer got the stock headers /exup :hammer:
will v-stacks help here?
thanx guys.
 

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THE MAN
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3,750 Posts
no, they wont. Not any noticable difference.

Your 100% best bet is to do the air box mod, use an aftermarket filter, and the stock 130 mains. It makes a huge difference. It's not as good as stock down low, but it's the closest you will get with a full system on these bikes.
 

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Moderator - In Memorium
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25,903 Posts
With A LOT of tuning you can bring it back some, but it will always be different with the removal of the EXUP. Like everyone has said, a carbed EXUP bike really needs the EXUP valve. What you are now running into is so much valve overlap that exhaust gases are reentering the combusting chamber then moving on the way. You will gain top end HP to the tune of a couple ponies, but the low / mid range is pretty well what it is going to be. I learned this in 2000 when I put a full system on my FZR. Takes a while, but you'll get used to it.
 

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Wheelie Makin' MoFo
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660 Posts
or you can do a 520 conversion. -1 in front and +2 in the rear
 

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THE MAN
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3,750 Posts
no matter what gearing your bike has, it will still make the same power curve....

No need for expert tuning :) Ivans kit, full akro, air box mod and a K&N. It's been done a million times with the same amazing results. Thats why it's called the "MOJO" :)
 

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Moderator - In Memorium
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25,903 Posts
what about degreeng the cams or using high lift ones,will it do any good?
Yes. According to the things I've learned through playing with the EXUP engine you can advance the intake some and retard the exhaust to accomodate working around the overlap issue that necessitated the EXUP in the first place, but ultimately what you may end up with is back to stock or there about performance levels. JAYSTENSEC4CYL gave you tuning advice that will work for the R1 of your year. Trust what is proven... or you can spend hundreds trying to find out the same thing,
 

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NeeD 4 SpeeD
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5,447 Posts
Discussion Starter · #14 ·
i'm not going to switch to akra, just cause i want to solve this problem once and for all (and i dont wanna spend that kind of money :) )

i was thinking , why on the newer fi bikes this problem almost does not exist?
then i came to a conclusion :
i hope i'm right :crash

the lack of exup at lower rpms causes less mixture to enter the combustion chamber .
on a fi bike the cdi knows how much air has ebtered the cylinder , so it can compensate for it by adding the right amount of fuel and retard/advance the timing according to this.

now , on a carbed bike the only feedback the cdi is getting is rpm and tps ,so ,if u change the ammount of fuel/air that enters the cylinder the cdi doesnt getting any feedback whatsoever.
so, i was thinking ,maybe i can retard the timing at 1-4k rpm only to compensate for a lower ammount of mixture ,what do u guys think?
the electronics involved is not a big problem for me ,it will take me some time , but i'll be able to do it .
i just want to know if my theory sounds right,whatcha think?:)
 

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THE MAN
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3,750 Posts
With a full system on these bikes it's pig rich under 4k rpm. You can lower the needles to improve drivability in that range, but you will do so at the expense of top end power (the whole reason for putting a full system on these bikes).

The newer bikes also have an exup system.

Fi has many advantages, not relying on vacume to draw in fuel is one of the main ones.

These motors are great street motors, they have terriffic mid range power, and deliver great part throttle power.

They do have disadvantages as well though, in that the head is not a fast burner, and combustion space is not ideally shaped, it is exhaust sensetive, and cam timing changes don't seem to make as drastic a change as in other (read G1K) motors.

If Ivan could have made these motors run seemlessly at low rpm with a full system he would have done so. The guy is a genusis. A truely GREAT motorcycle tuner.

If you take away timing down low it will further reduce performance.
 

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Born to do trackdays
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390 Posts
For a full system, Akra would not be the answer to your specific needs either. If I recall the name correctly, there were systems such as Muzzy that produce better low & midrange (but less topend) power.

Even FI bikes get affected if the EXUP is removed. It is easier though to adjust and to lessen the impact than on a carbed bike.
 
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