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Going to start working on the bog and I already have PowerNow.

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Ok, before I open this can of worms let me say that I have the PowerNow on my bike and I like what it does.

Now I want to get rid of the bog. Going to start with the leak jet and work from there as I can afford it. Is the PowerNow going to adversely affect my results or will it not have much of an effect on jetting changes? Anyone out there have it all or at least some done, PowerNow, leak, JD kit? How is it working? I want to be able to crack the throttle all the way from idle and not have the bike "flood out". I also want the added low end from the PowerNow for the 1st and 2nd gear trail riding I do.

Any insight would be helpful.

Shane

PS.. I did do a search back 1 year and could not find much on this.

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Do you have the screenless air filter cage? That will help it breathe big time. I noticed a huge difference with that. More than I did with the powernow.

A Cheap way of doing this is, cut the screen out of your stock cage and get the flame resistant air filter from Twin Air.

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I have exactly these mods and it works perfectly. The power now will effectively richen the top end mixture so you'll probably want to go a little leaner on the main.

Cutting the air filter screen will adversely affect your low end, because it will significantly decrease one of the sources of low end vacuum, namely the vacuum differential between the engine intake and the airbox inlet.

My current settings are 42 pilot, 180 main jet, JD blue needle on clip position 3, with a 40 leak jet. I'll switch to clip position 4 during the colder spring and fall months.

Your mileage may vary, especially on the leak jet. Each bike is just enough different that you'll have to custom-select your leak jet for your bike and riding style. Good luck.

You might get more hits if you search for "bog", "AP" and "leak jet" on this forum. Also check out all leak jet and AP sections in the site map at the FAQ. Here's the link.

http://www.thumperfaq.com/sitemap.htm

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Cutting the screen out only added top end power, it did not affect bottom end power on our 250's.

It has enough blockage to kill top end airflow, but it's pretty much invisible to low rpm airflow

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Thanks guys, I have printed all the stuff on jetting and mods, the biggest question I had was about the use of PowerNow with all or some of these mods and if anyone noticed problems or solutions with or with out the PowerNow. I understand the problems that are fixed by Jetting, Mods, and tuning and I understand the problem that is fixed by the PowerNow, just wondering if more problems arise by combining the PowerNow and some and/or all of the tuning and mods.

Shane

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Cutting the screen out only added top end power, it did not affect bottom end power on our 250's.

It has enough blockage to kill top end airflow, but it's pretty much invisible to low rpm airflow

I'm sorry, but that's wrong. Try installing a filter frame with and without the screen, and you'll see what I mean. If you can't tell the diffference in your bikes, then they may be jetted incorrectly.

Two mechanisms provide vacuum in the carburetor. The primary mechanism, that everyone is familiar with, is the venturi effect. High velocity air in the carburetor throat has less absolute pressure (ala Bernoulli) than the air pushing on the top of the fuel in the float resevior. This higher relative pressure forces fuel up into the air stream.

Mechanism No.2 is the relative pressure differential across the carburetor. As a mental exercise substitute a PVC "T" for the carburetor. One end of the T would be connected to the vacuum source (the engine), while the other could be considered the inlet (or air filter box). The bottom of the T would be sucking fuel out of the carburetor bowl. The more you restrict the inlet (the filter box), the more fuel you suck up out of the bowl. Restricting the air inlet (like with a screen) will deliver more fuel (and a little less air), richening the A/F mixture (up to a point obviously).

Conversly, removing the screen will lean out the low throttle A/F mixture. You'll need to richen up the pilot circuit a little to compensate, but even with that you'll lose some of that snap off of idle, and sacrifice some torquiness as well.

This is why low throttle jetting is affected when you change the air box design by cutting holes, cutting the screen, removing the lid, etc. The air flow at low throttle isn't sufficient for Mechanism 1 to have any effect, but the pressure differential across the carburetor IS changed, which changes the mixture and, by extension, low end power delivery.

To answer the original question, the Power Now shouldn't have much effect on being able to cure the bog. You should be able to tune it out with or without the Power Now. You shouldn't, however, expect the Power Now to help the bog much.

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(scrubbed)

It didnt affect the low rpm airflow, and it is jetted correctly. I'm not the only one that has done this either, so it could be you that has the problem.

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Great, just what we need another bench expert. :devil:

It didnt affect the low rpm airflow, and it is jetted correctly. I'm not the only one that has done this either, so it could be you that has the problem.

Why is it that webexperts think they are the only one's capable of doing something or that if they cant do it themselves they find it impossible that anyone one else can? I still find that amusing. :thumbsup:

.

I'm not claiming to be any kind of expert. Only trying to make sure that forum-browsers get accurate information.

Having witnessed the futility of arguing the obvious with you, I'll spare the readership. For those who aren't familir with YZ250F_Rider, see the >Octane Booster< thread. A quick read through of this thread will make obvious who knows what they are talking about, and who's the dope(s). This is a thread in which not only did Mr. Rohrich unintentionally expose you for the fool that you are, but you yourself demonstrated that you're too dumb to know when you're wrong, even when it has been explained to you in excruciating detail.

A word of advice. Just because you fail to understand a concept, doesn't make it wrong.

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What you didnt learn was that the accelerator pump squirts fuel in the cylinder at the exact same time that "loss of snap, and sluggishness" is supposed to happen.

It does it because there is a huge change in that pressure differential due to the throttle plate opening. The air fuel mix needs enriching to compensate for the loss of air velocity in the venturi due to the loss of vacumn.

There is a huge difference in the quantity fuel being added to the quantity of fuel being leaned by the screen not being there. Thats why you cant feel any change in the low rpms. Assuming the bike is not bogging from a poorly adjusted pump to begin with.

You guys add a lot with the dissertations of why things shouldnt work. If you whould consider the whole system before assuming something, your dissertations might be able to explain why they do. :thumbsup:

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too dumb to know when I am wrong? LOL

ummm I am the one that said the toluene mix produces more power due to the toluene being denser than gasoline.

I notice someone seems to agree with that statement today.

In terms of absolute performance I doubt you would see any real difference between the two fuels unless they used some very heavy hydrocarbons to get the additional octane for the 98 fuel.

For you barton, that is exactly what is happeneing by adding more toluene to the gas. And if you read my post before this one, you will see what you failed to consider in your earlier assessment.

You should be more careful who you call stupid.

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I knew that wouldn't take long. :thumbsup:

I'm happy that you understand the operation of the AP. If you'll search for 'bog', 'AP', 'leak jet', and 'squirt duration', and read my posts, you'll find that I'm somewhat aware of how it works as well.

I never said that cutting the screen won't work. It works great, if you want more top end. However, the original poster plainly stated that he was interested in maintaining low end power. I guess that explains why you can't quite keep up with the thread; you lack reading comprehension. What kind of college hands out EE diplomas to guys like you? Should I use smaller words, or bigger type?

If I weren't leaving in an hour or so for Boston to meet with some folks from MIT, I probably still wouldn't argue with you. Bye bye, loser! See ya'll on Friday! :devil:

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You were definitely not the first to talk about the bog, nor will you be the last. Too bad all of your self awareness didnt allow you to realize the pump squirts at the very same time you think it's going to lose snap though.

I'm surprised that you missed that actually.

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I'll put this here so it's not missed.

Removing the screen does not affect the low end response because the accelerator pump more than compensates for any leaning of the mix at low rpms. Thus no loss of snap.

Thats the part you fail to comprehend. Hopefully others can get past your rants as your failure shouldnt be theirs.

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I notice someone seems to agree with that statement today.

Don't flatter yourself Mr. Clueless . :thumbsup:

In terms of absolute performance I doubt you would see any real difference between the two fuels unless they used some very heavy hydrocarbons to get the additional octane for the 98 fuel.

As usual you read things in that aren't there in an effort to try and prop up your total lack of understanding of the subject at hand.

If the refiners of the australian fuel used heavy hydrocarbons to get the additional octane for the 98 fuel the upper end of the distillation curve temps would be increased and performance would DECREASE at high rpm because the heavy components would never have the opportunity to vaporize and contribute to the combustion process. Based on the data provided this appears to be the case. Had you read the entire thread, or actually understood what we were talking about you would have seen that given the shape of the distillation curves that he posted it's likely that the lower octane fuel would make a bit more power in his 250F. Fuel components with temperatures above about 240-250F are basically wasted in water cooled, short intake engines that run above 7000 rpm. Fuels that contain these high temp components in significant enough quantities to alter the distillation curve past the 50% point tend to make less power above about 7000 rpm whether you care to believe it or not.

I realize in your magical chemistry impaired world you are allowed to ignore these types of things, but the rest of us are forced to contend with the basic laws that govern the planet.

Why are you even wasting your time with slow-witted backwards thinking clods like us? Shouldn't you be heading off to Home Depot to discover the next big speed secret?

One last thing as long as we are on the subject of the air filter screen. There is no major change in the pressure differential with or without the screen on the 250F just like it was in 1998 when I measured the original YZ400F. Unlike you Mr. Toluene I've actually taken the time to measure it on my flow bench and so did Dr. Rob Tuluie when he was doing the development work on Doug Henry's SuperMoto YZ450F last year. The end result after a lot of flow bench and dyno time looking for as much usuable power as they could get? Doug Henry's Super trick YZ450F that won Irwindale had the oem filter screen installed in his bike all season.

Dr. Tuluie is now working in Europe as one of the technical directors for the Renault Formula 1 squad. While you might not like MY pedigree, you are going to have a much tougher time trying to discredit his. But I'm sure in your bizzare convoluted way you'll come up with something. :devil:

Those of you who are looking for a power increase from removing the screen are likely to be disappointed.

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I love how you guys try to use dissertations to explain away what you cant do. And as usual they never consider all of the variables involved, leading you to false findings.

I originally said it makes more power than gas alone simply because it is denser than gas alone therefore more bang for the same volume. You confirmed that with your own statement.

Are you sure you're not related to kerry? You waffle as much as he does.

You really should track down everyone that says it works both toluene and the airscreen removal, and try to force them to think the way everyone that told you it wouldnt like. You'll find that they wont change their minds either.

Just because you are slow witted (your words, not mine) and cant find it for yourself doesnt mean the rest of the world has to have the same disability.

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By the way, you and barton should get together and agree on what you are going to say. You just biatch slapped barton in your quest to squelch me. :thumbsup:

There is no major change in the pressure differential with or without the screen on the 250F

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Man oh Man, I guess I opened up a HUGE can of worms. Should we host a TT boxing match?

Well gentalmen, thanks to both/all of you. Somewhere in this madness my real question was actually answered. I will continue with my jetting adventure.

Once again, thank you.

Shane

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