Yet another round of "Guess that number"

[preddy08]

Dropped off the rappy tuesday night and was told it should be back today. Last dyno trip was 71hp, what do you think it will be now? Things I've changed, gapless rings, Sparks exhaust, DL programed Dyna, Bos updated head port, New larger Accel spark plug wire (indexed spark plug, got board...lol), Kennys evac valve. I'm sure hoping for 80HP!!!

Seeing the HP difference between the HMF and Sparks makes me think 80 is with in reach.


Keep in mind the bike litterly has a total of a minute run time. So once it breaks in I should see another couple HP.

[preddy08]

And more bad news! Stock injector is maxed out

[rutcutter]

I don't see anything that increased compression...... So I say you will see no more than 3-4hp gain.

I say 74-75hp and around 52TQ

[Krandall]

My guess.... 75-77.

Maybe get some duals on that beast and youll see 80

[preddy08]

I don't see anything that increased compression...... So I say you will see no more than 3-4hp gain.

I say 74-75hp and around 52TQ

going from a crappy single (like I did) to a sparks alone is 3-4HP. Theres alot more to Hp then added compression.

The stock injector is maxed out now and its sitting around 15:1 at 75HP

[Troy]

Something doesn't seem right about that injector, it should be able to support your mods easily.

[preddy08]

Something doesn't seem right about that injector, it should be able to support your mods easily.

Sounds like anything above 75 horse or so you'll get above 80% duty cycle and it will start acting real irratic (SP?).

[preddy08]

When I calculate it I usually use a .5 BSFC to error on the safe side. Also it seems like you are doing the math correctly, but I believe that your hp numbers are based off crank hp. This also needs to be taken into account, as the crank hp numbers and wheel hp numbers are much different.

For example: with a stock injector at 80% duty cycle, 45 psi at the rail and a BSFC of .5 you will be at about 66 crank hp. However if you change it to a BSFC of .45 and all the other factors are the same the hp the stock injector can support is about 73.

With that being said this is crank hp, and not rwhp. I'm not sure what the drive train percentage loss is on a atv (as I have never dynoed an atv at the crank), but typically on a manual transmission the loss is anywhere from 15%-20%.

This means that with a 15% loss (which is more likely with motorcycles) and based on the numbers from above a stock injector with BSFC of .5 should handle about 56 rwhp, and a BSFC of .45 with stock injector is about 62 rwhp.

Now don't take these numbers as "if I hit 56 rwhp then my injector is maxed out." Because there are many factors involved, and elevation is the biggest. Just because the dyno shows you have 60 hp at the wheels, doesn't mean you are really making that at your elevation. Dyno's put in correction factors for humidity, elevation, temperature etc....

You are asking yourself, well how do I know when the stock injector is maxed out? Well while you're on the dyno if you hit 80% duty cycle this is about as much as you want to push an injector. Sure you can go way beyond 80% duty cycle (many people have), but this is bad for a number of reasons. The biggest being inconsistent fuel delivery, as the injectors needle begins to bounce. Also it is stressing the injector beyond the point it was designed to operate at. The biggest give away when an injector is maxed out is told while you are dyno tuning it.

As you push the duty cycle higher and higher you will hit a point where the injector acts "goofy." It will not increase fuel as much as it was before (say 5% increase on the fuel map does not yield an actual 5% delivery of fuel), or it will add a big burst of fuel suddenly. This means the injector is probably past the max duty cycle it can handle and as a result you see the inconsistencies.

There is your fuel injector lesson of the day!

[Krandall]

I don't see anything that increased compression...... So I say you will see no more than 3-4hp gain.

I say 74-75hp and around 52TQ

going from a crappy single (like I did) to a sparks alone is 3-4HP. Theres alot more to Hp then added compression.

The stock injector is maxed out now and its sitting around 15:1 at 75HP

I'm just giving you my take. I don't think you'll see a 9+ hp gain.

Does the total seal gapless ring add 1 point to compression.



And injector.. I compare it to a hose w/ one of those standard copper nozzles on the end where you twist.. and you get a nice "V" shaped spray. and there's a point where it gets to a solid line basically " l "  but if you keep opening it.. it starts spraying really weird it loses that fine line. and doens't flow as good as when it was doin the solid line   (my theory anyways)

[preddy08]

I don't see anything that increased compression...... So I say you will see no more than 3-4hp gain.

I say 74-75hp and around 52TQ

going from a crappy single (like I did) to a sparks alone is 3-4HP. Theres alot more to Hp then added compression.

The stock injector is maxed out now and its sitting around 15:1 at 75HP

I'm just giving you my take. I don't think you'll see a 9+ hp gain.

Does the total seal gapless ring add 1 point to compression.



And injector.. I compare it to a hose w/ one of those standard copper nozzles on the end where you twist.. and you get a nice "V" shaped spray. and there's a point where it gets to a solid line basically " l "  but if you keep opening it.. it starts spraying really weird it loses that fine line. and doens't flow as good as when it was doin the solid line   (my theory anyways)

Sorry, I ment to say 15:1AFR.

On v-8 chevy motors gapless rings are usually good for 20HP or so. Not to mention that I'm only running one ring....lol

[Krandall]

Hmmm, I'm still sold on a mid 70's.. I'll give you up to 78hp.

[Peelz]

YOu guys seriously crack me up. 80 hp! on a f**king trail bike. Lay off the meth preddy.

[DL700]

my guess is 75-76 on that dyno with a lot better/longer power band


what are u seeing as far as map #'s go..... in my map for my bike the largest numbers i see are "37" at about 8500 rpm ..........duty cycle remains around 60% well within the means of the stock injector......i very efficent running port job and combo of parts......

[preddy08]

my guess is 75-76 on that dyno with a lot better/longer power band


what are u seeing as far as map #'s go..... in my map for my bike the largest numbers i see are "37" at about 8500 rpm ..........duty cycle remains around 60% well within the means of the stock injector......i very efficent running port job and combo of parts......

Thats what I think is weird. Not much has changed since my last build and now I'm maxing out the injector. I'm sitting at 75HP now with a 15 AFR.

[preddy08]

Come to find out its puffin smoke on de-cell?? He says it does'nt look like coolant.