what exhaust? new to the forum

hey there new to the forum and just bought my first wr. iv had four stroke mx bikes but my question is can i run an fmf exhaust and still have it be street legal? i see a lot of people on here with aftermarket exhausts but just want to know if there are regulations. i know fmf puts not for street use on there website so just checking with you guys oh and some good brands you guys like would be awesome!

I have the FMF megabomb and a powerbomb(which I just took off) and their Q4 muffler.. I don't really care about being legit.. I think it's sounds good.. not too loud.. but I did re-pack the pipe the other day and put the spark arrester back in, then a little later that day, the spark arrester flew out and I lost it.. No I have no choice but to be loud until my new one comes in..

I'd say give'r with the full FMF system you won't be let down..

Almost all aftermarket exhaust systems come with some kind of disclaimer that they're "race track only" or "not intended for use on public roads" kinda crap.


The FmF Q4 is pretty much hands down the quietest aftermarket exhaust you can buy.

The jury is very much out on if a new header pipe does anything more than drain your bank account.

However, if you intend to open up the exhaust you should also open up the intake, which then pretty much means you'll need some kind of EFI programmer to prevent from running too lean in your air/fuel mixture.

Read around the forum. There's lots of info and recommendations here.

You're not the first to ask.

Thanks ill do some research in the forum I just think the stock exhaust sounds a bit puny and they didn't make it too attractive for my likings. Want a more Mx oriented one.

Hey mate i'm running the GYTR rear muffler, which i very much like for quality, fit & looks. It's pretty much the only performance unit available that allows you to retain the stock heat shield. Not sure where it sits in noise level comparisen with other "free flow" mufflers, but i consider it to be very loud.

Possibly only one negative, which is that it's alot more coin than most other aftermarket units.

Cheers.

Unless your in Ca and need to have parts that meet carb standards the only thing to worry about is sound levels, i think Fmf is just covering there butts with the "offroad only" stuff.
There's plenty of factual information showing headers making more power on these bikes, don't be discouraged by opinions
Fmf actually makes yamaha's gytr exhaust so you'll be fine either way!

Execelon wrote:

There's plenty of factual information showing headers making more power on these bikes, don't be discouraged by opinions

I know at least one guy here at this forum who can/might post dyno results that show the exact opposite.

If you could provide the "factual information" that would be awesome.

And I'm not being a smart-ass here.
I'd love to see dyno results with Yamaha header vs. FmF header on a wr250r/x

http://www.supermotojunkie.com/showthread.php?59432-New-header-gains&p=569026&highlight=#post569026

^^^ pretty self explaintory, the pics and dyno sheet are long gone but i think it's cut and dry.

Is it fmf's header or any "new header" that's not making any power? you seamed to make a blanket statement at first.

Please post any info you have I'd love to see it.

If you're in California leave it stock. I've seen a lot of people busted for loud exhausts and not let into riding areas like Gorman and Hollister.

Execelon wrote:

http://www.supermotojunkie.com/showthread.php?59432-New-header-gains&p=569026&highlight=#post569026

^^^ pretty self explaintory, the pics and dyno sheet are long gone but i think it's cut and dry.

Is it fmf's header or any "new header" that's not making any power? you seamed to make a blanket statement at first.

Please post any info you have I'd love to see it.

I'll see your post and quote this :

oic0 wrote:

motokid wrote:

oic0 wrote:

Also, don't bother with the aftermarket headers. The FMF models actually decrease power.

You have what evidence of this????

I'd love to know for real if there are any advantages, or if you're correct, disadvantages.


You may save people a lot of money if you have proof.

I can't find the post, but when thumper racing was sharing dyno results for their big bore kits they said the numbers on their kit in one of the graphs was down a bit because it had a powerbomb header on instead of the stocker. I figured they had probably dynod the bike dozens of times with different setups and would know. That paired with the threads saying the powerbomb is a smaller diameter were enough to prevent me from spending money on it.

oic0 wrote:

Found it

Quote :

"There is a slight dip in HP and Tq from 6500 to 8800rpms. This is due to the powerbomb header. Using the stock header would have improved this area and we would have run at or above the GYRT through here as well. I didn't bring the stock header with me or I would have gotten a run with it as well."

-http://www.supermotojunkie.com/showthread.php?84451-GYTR-290CC-bigbore-for-WR250x!/page3&p=881677&posted=1#post881677

Note that is with a big bore kit, but if it flows less, it flows less.

oic0 wrote:

Here is the chart that all of that was in relation too.

That's a dyno sheet comparing 2 different bigbore kits... And the one with more peak power has a header... Winning!!! ;-) lol Actually it a shit comparison for a header argument and for bb kit because the difference could be in the bigbore kits or header.. Can't change 2 variables and argue 1 made the difference...

Fmf's header does have a bigger OD then stock and unless its silly thick the ID should also be bigger so that's completey false..

Do you have the link for that dyno sheet? I'm sure someone called the bs out

[QUOTE=Thumper Racing;881677]We finished the dyno runs today. What a deal I left at 4am to drive to Vegas for the run and drove back to LA right afterwards. 9 hours of driving yuck. I did find out some real HP#'s from the guys at DynaJet and they were kind enough to give us an overlay of a stocker, the GYRT kit and the thumper Racing kit. I know different Dynos will give different readings but all 3 runs were taken on the same dyno with the differences noted. We now have maps for both the PC3 and PC5's available.

The ThumperRacing kit made the most peak HP +.75hp and maintained a 1-2 hp advantage from 9k to redline. If you look closely you'll see on the dyno chart for the GYRT kit it looks like Yamaha lowered the redline by 500rpm. There is a slight dip in HP and Tq from 6500 to 8800rpms. This is due to the powerbomb header. Using the stock header would have improved this area and we would have run at or above the GYRT through here as well. I didn't bring the stock header with me or I would have gotten a run with it as well.

All in all I'm very happy with the results. We are giving up 15cc to the GYRT and are still making more power.



It's interesting to note the ambient temp between the 3 runs is was stock 61deg, GYRT 82deg and ThumperRacing 95. Barometric pressure was all about 28 in-Hg and humidity was 13% for the GYRT and Thumper, stock run was 28%. We still made more power even though temperatures were highest during our test. We would have made another .5 hp if we tested with the GYRT at 82deg and about 1 hp if we could have tested with the stocker at 61 deg.

Mods:
Stock bike --well stock
Athena/GYRT kit-- GYRT exhaust, GYRT ECM, Athena/GYRT290 kit (289cc)
Thumper Racing-- Full FMF PowerBomb, PC5, Thumper Racing 280 kit (275cc)[/QUOTE]



This goes with your dyno sheet, also later in the thread he says he has airbox mods....

To be fair - from the link you provided there's not one single mention of the "header" being something "off the shelf" from an after-market company like FmF.


In fact - to me it sounds 100% custom built.

Quote :

Here are some pics and a graph showing the newest header I've built for my WR250X. I've been trying to broaden the power in the upper rev band without loosing snap off of the bottom. This is the 3rd version for this particular bike. Not a huge difference between the peak numbers, but the power is up 1-2whp from 8k until the rev limiter. Torque was up around 1wtq from 8k out aswell. You can definately tell a difference on the street as it feels much more eager to rev.

Then if you go looking at MPFab's other posts you'll see a big honking turbo kit on his wr250x.


I'm not saying one way or the other that an aftermarket header improves power or restricts it.

I'm just saying the jury is a bit out on any real gains as there's next to no concrete dyno evidence available to support any of the claims I've seen posted. FmF's website says "up to a 3 hp boost" simply from bolting on a header.

Until I see some true dyno charts with exact same conditions, one with yamaha oem header, and one with aftermarket header, all other things being equal, I will still contend that money spent on an EFI programmer will yield much better results for overall performance on our bikes.

Mpfabs header is a custom header but it clearly shows hp improvement.. He had 3 designs similar to power bomb, mega bomb and I think pro-circuits header.. So saying these headers don't show similar improvements is silly.. Also you should note the header made 1.x hp more in comparison to his old header which also had improvements with no TUNER!!!
Mpfab makes turbo kits.... Good point he doesn't really sell headers so there's no smoke and mirrors there.

Now your saying a just a programmer makes more then a header ?? Sounds irrelevant to the topic but plausible, prove it!

If you wanna wait for the perfect dyno comparisons of "fillin the blank" header go for it! Did you do that with everything on your bike? the rest of us crazy header people will enjoy them, Looks to me like you where once a believe in headers and where shoot down by misguided-misinformation.

power bomb vs stock

Edit: power is on top ;-)

Execelon wrote:

power bomb vs stock

Edit: power is on top ;-)

Pretty big difference. Great debate.

I never once debated or suggested the ID of the aftermarket header from FMF was smaller than stock.

In fact I stated without question it's not since I had to use a spacer/coupler to mount my Q4 to my stock header.

I've also posted pictures of my melted spacer/coupler.

What I, and others have questioned, is if there's any true/real advantage to power between a stock header and an FmF header.

I'm more than sure you're not getting a 3 hp increase by simply swapping out the stock header and putting in an FmF header.
Not on our bikes.

I believe you're more than likely getting a shift in the torque curve, or maybe getting a slight advantage in overall top speed. Maybe.

Maybe not.

Again, there's very little, if no real evidence the Yamaha header is that restrictive. It's a very short piece of pipe.

Without a before and after dyno chart to compare, the rest is just conjecture.

I dont think I ever said you said blah blah blah..

But you posted quotes with misinformation, Which is saying it indirectly. The craziest thing about you quoting people saying its smaller and flows less is that now your sayin you knew it was bigger... I think posting actual facts clearly showing its bigger and I think its safe to say flows more helps anyone else that could be misinformed by your posts.

Your saying Fmf claims 3hp, that sound feasible when you think about it being at the crank on a best case scenario.. 20% drive train loss (guessing) gives you 2.6hp which is could happen with a fmf exhaust and tuner... You don't seriously think all claimed hp is the minimum at the wheels I hope.

I quoted somebody who posted something contradictory to the general theory. I never said I agreed with what was in that quote. In fact, if you go to the thread I linked, you'll see I did not buy into what he posted.

That's neither here nor there however.

The beauty of the fmf claim is this:

They say "up to 3 hp gain".

Which can mean nothing. Zero gain.

I've still not seen a definitive dyno chart comparing a stock header to after-market header.

If anybody is interested in my experience:

When I had a 2008 WR-250X back in 2011, I did the usual mods of FMF programmer, airbox flapper removal, FMF exhaust, lower gearing, speedo recalibrator, etc.
The results felt very good, as was the case with the 2008 WR-250R I rode the year or so before.

One of the last things I added was the FMF Megabomb header pipe.
I'd already had the FMF Q4 muffler on the bike (along with the other mods mentioned) for a couple of weeks or so, and I was curious about making a back-to-back comparison between the stock header and the Megabomb header, ridden just minutes apart out on the roads I rode regularly.

Results:

Compared to the stock header with the FMF Q4 muffler, the Megabomb header and Q4 muffler gave the bike a very noticeable increase from just above idle up to about where the power starts to taper off.
I was not sure if power was actually removed from the top to get this increase at lower RPM, or if it was an illusion from the increase at lower RPM, but the revs up high on what is known as over rev (when you insist on revving past the point of where power starts to taper off) seemed a shade weaker.
If it actually was weaker, it was very slight.

My overall impression of stock vs. Megabomb header was that it was worth the money as it gave the bike more oomph at real-world, used-much-of-the-time engine RPM.
The top revs were still very much as stock, and the bike would still rev all the way to the rev limiter if you wanted to.

FMF was a big plus in power for me. Just saying

Bob