| Author | Message | ||
     Ingemar |
Would it be safe to up the rev limiter to 8500? I know the older bmw's had no problem with it, and those were strokers too. How is it done? | ||
| Brucelee |
Think about it. Do you really THINK it would be safe? 1000 over max, I wouldn't do it with my engine. If you try it, let us know! | ||
| BadS1 |
The Question to me is why???Your bike isn't making any more HP at its rev limit now.So even if you did the only thing your accomplishing is more noise. | ||
| Ingemar |
I guess I'm wondering if the limiter kicks in simply because above its dead or if reliability becomes a serious issue (or both?). A little porting and different cams will have the bike make more power higher up the revs, but if reliability becomes an issue then were does that get you? | ||
| Wyckedflesh |
Dana in the case of the 9's I am not sure about the "not making anymore power" but I know from the two dyno runs on my 12, it was definately still on the rise of the horsepower curve when the limiters stepped in and shut it down. | ||
| M1combat |
The 12 engine is still climbing VERY strong at 6800. The torque curve has started to shut down a little by 6800, but not enough to start dragging the HP down with it yet. As far as reliability... It's no less reliable if you don't USE the extra revs, so the question really becomes... How much will you use it? I would say that 1000 more might be a bit much, but I'd like to see 7500 on my 12. I very rarely ever even get to 6000 on mine though... | ||
| BadS1 |
Wycked is climbing maybe but I'd think its not making good usable HP. | ||
| Xbolt12 |
They are doing it on the Formula Extreme bikes, but I am sure those are torn down frequently (and also heavily modified) xbolt12 | ||
| BadS1 |
Very much so. | ||
| Static |
I would be concerned about the stock connecting rod life at 8500 rpm. I believe that's one of several reasons for limiting the rev's. | ||
| Slaughter |
NO NO NO NO NO --- Piston speed is too high at 8000 rpm even with the short stroke motor (XB9) to have any expectation of living more than just a few trips up to the rev limiter. I have set the redline on my racebike at 7800 and try to stay below 7500. The only reason I have 7800 is in case I get pulled up higher when drafting somebody on the track, I'll have a little in reserve for a pass. The FX guys get good power and have spare bike and maybe a motor at the track. If you have a primary bike, and a "B" bike at the ready and a spare motor in your trailer, an 8000 rpm redline might make sense. Also, if you are running something other than a stock rev-limiter with a gradual spark interruption, you can actually DAMAGE the engine just hitting a hard rev limit at that high an rpm. The short stroke motors (XB9) punched out to 1169cc (XB9 punched to 3 13/16 bore) will tolerate 7500 rpm. The strokers will DIE. If you can afford a teardown inspection monthly, you'll make good power - for a weekend. I just did my first F-USA race this weekend and got to do a lot of comparing notes but these are BIG aircooled pushrod motors - and they just don't take kindly to those kinda rpms Heavy C-Rods really don't help - you'll just blow out the bottom end instead of bending rods. If you're contemplating high rpms, talk to the guys at Hal's PA about top end and valve train modifications. They can sell you any of the stuff they put on Cicotto's FX and Bilansky's F-USA bikes if you wanted to go that far - though they can help you stay sane and NOT buy stuff you really don't need. http://www.halspa.com (Message edited by slaughter on September 20, 2004) | ||
| Ingemar |
NO NO NO NO NO OK OK OK OK OK!  Thanx for the explanation! I'm not planning on spending big bucks and certainly don't want to risk blowing up my engine. I was simply wondering about it and I can imagine Buell would keep a little reserve on the piston speed to play safe on reliability. I have set the redline on my racebike at 7800 Isn't that the default for the xb9? I *try* not to run into it too often, but I get pretty close nearly every trip I make. | ||
| Slaughter |
(I didn't mean to sound angry!! - sorry) - just that high rpms are scary for these engines. The 7800 redline gives me a hope of a long engine life as long as I try to shift by 7500. I re-set the redline for dyno runs at 8000 but set it back down to 7800 for racing. The high rpms really are hard on these motors but at 7500, you're pretty safe. My motor HP peaks about 7800 rpm and the couple times I have tried to use all the power (passing) I do so knowing that I'm taking life out of the motor. | ||
| Ingemar |
I didn't mean to sound angry!! - sorry I didn't think you did. That's why I put after my reply, but still things don't always carry as intended. Thanx again for your explanation. I appreciate it. | ||
| BadS1 |
I wouldn't go so far as to say Hal's can sell you anything thats on Cicotto's bike cause thats not gonna happen.But they will build you a very good motor that make big power.How thick is your wallet?? | ||
| Fullpower |
no way will that crank assembley live at 8500 rpm that is the simple answer, and there is no way around it. if you want to rev a v twin that high, you need to start with a different v twin. | ||
| M1combat |
What about balancing the crank we've got, and then bringing the stroke down to where the valve train is the limiting factor instead of the piston speed? This would require longer con-rods but because of that we would have a lower side loading ratio so it would make even MORE sense to use slipper pistons... We'd still only get about 8K-8500 RPMs out of that though. Isn't that the pretty much decided upon limit to the valve train? After that, we could mill the front of the case to make 50 degrees and bore it out some more... Just to get back some of that power we lost when de-stroking. This of course would require some very fun modifications to a whole bunch of neat stuff  . | ||
| Slaughter |
Well - yeah, Hal's is NOT gonna want to build you something for $25K that's going to have you facing a total rebuild every couple track hours! They did say that if I could point to something on any of their bikes, they could quote me what it'd cost - including tuning. Based on what I spent "on the cheap" - I'd have been about 6 months closer to where I am now if I'd just crated the bike and shipped it to them with my wish list - and probably not spent more money than I did doing it "my way." Yeah, makes no sense to try to get a bike built as a "Ciccotto Replica" but I was part of a small crowd that got to look at Leno's/Hals XB-1340 when it came into the shop here at Glendale and looking at the dyno results that day, he was getting about 128 HP to the ground. If he wanted to bump up the redline to where Hal's had been racing, he'd have gotten a few more ponies. At that kind of power and rpm's, it'd be a miracle if it lasted very long. Rumor has it, he paid about $25K over the purchase price for the engine/suspension/setup/spares. The bike COULD be competitive in FX. NOTE - this was a "street legal" bike (baaaarely) and I believe he bought a spare motor at the same time. By the way, the only HAL's parts I have are the swingarm chain conversion - I got everything else from Nallin. I've just spent a lot of time bugging Hal's every once in a while on setting up my motor and spent this weekend playing at being a racer and got to talk to the Hal's (Bilansky) guys, Kosco (Johnson)-crewed by our own Timbo - and was pitting with Bartels Racing's Jeff Ecklund (who qualified and finished 9th on a BONE STOCK XB9 - except for ECM, pipes and slicks!!). Of course I was there racing because SOMEBODY had to come in DFL. | ||
| BadS1 |
I (Message edited by blake on September 20, 2004) | ||
| Slaughter |
Point taken. Reflecting on my conversation with Jim Winter - it was more like "we could build you Cicotto's bike for about ($25K if I remember) - also quoted in RRW. I may have taken it too literally - this was considering I was NOT building an FX-bike but a F-USA (100-ish HP) type motor. Truly, they are constantly working out everything from intake/injection, suspension, brakes, cooling... you name it - their bikes are works-in-progress. The point I think Jim Winter was making is that I could have them pretty much build anything I'd need (not that I can afford any more of ANYTHING to the bike) and since I have the short stroke/big bore engine, it was more likely a general statement on his part. I've built a pretty mundane F-USA legal bike more like Bilansky's than Cicotto's (and at that, only in bore/stroke) but Hal's has helped me sort out the mapping and I was able to compare notes with Bilansky this weekend. To be sure, they're NOT the only game in town!! Also, none of this is to take away from the support offered by Buell Racing - Duga, Glenn Veatch, Dan Hurda were tremendously helpful when setting up and tuning my engine and suspension and then airfreighting out another chassis after a crash. All this for an old fool in his first "big" race after a 4 month layoff and the first time on the XB on a racetrack since last October's big crash at Willow Springs. It's a small community of folks silly enough to consider racing these things and Hals seemed to be the most accessible to me here in CA. By the way, I gotta meet some of the Buell faithful the next time I'm out there. Last month was just too little time (Family in Slinger, W. Bend, Bloomer) | ||
| BadS1 |
Damn right you do Steve.Maybe next year if they have Homecoming again here.Something tells me though that they will. |
