hp gaining mods?
09-07-2006, 07:06 PM
#31
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Try the pistons first. That's going to be the best mod you will make. Cams and head porting will be really limited by the stock compression. My personal opinion is that compression is one of the biggest differences between the VTR and the RC51 engines.
BTW, you can upgrade the VTR for a lot less than $3000. I think it's certainly worth putting a little effort into, you'll get a lot back out of it.
BTW, you can upgrade the VTR for a lot less than $3000. I think it's certainly worth putting a little effort into, you'll get a lot back out of it.
09-07-2006, 08:55 PM
#32
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Originally Posted by Hawk 996
I may not agree with all of your points but i most deffinitley respect the way you present your point of view.
Id like a quick retort, i dont have a racebike, nor do i particularly want a race bike, i have a street bike, id just like a little more go when i twist the throttle.
The idea of me modding my bike is just something ive been throwing around for a while (currently its bone stock) I know there are many bikes that are going to hand me my *** but im not too worried about that, I know in the long run it would prolly be cheaper and id get better performance out of an RC51, but i dont have the cash to plop down on an RC51 (or i probablly would) and im trying to stay out of debt for a while.
I could go by a CBR 929RR For about 4 grand right now, but its not what i have, nor what i want right now.
So im sticking to tinkering with my hawk, thanks for all the warning, and all the advice, i will keep everyone updated on the progress, but it might be a while before we have any significant changes...
Id like a quick retort, i dont have a racebike, nor do i particularly want a race bike, i have a street bike, id just like a little more go when i twist the throttle.
The idea of me modding my bike is just something ive been throwing around for a while (currently its bone stock) I know there are many bikes that are going to hand me my *** but im not too worried about that, I know in the long run it would prolly be cheaper and id get better performance out of an RC51, but i dont have the cash to plop down on an RC51 (or i probablly would) and im trying to stay out of debt for a while.
I could go by a CBR 929RR For about 4 grand right now, but its not what i have, nor what i want right now.
So im sticking to tinkering with my hawk, thanks for all the warning, and all the advice, i will keep everyone updated on the progress, but it might be a while before we have any significant changes...
I wasn't aware your bike was completely stock. Well, by all means, mod away! You will get some mild power increases but you'll notice the most change in the bike when you do suspension upgrades and brakes. The bike will be faster because you will be able to ride it faster. Don't expect much more on the 1/4 mile though.
09-08-2006, 08:15 AM
#33
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The VTR and RC51 engines are completely different. The RC1 has a bigger bore, shorter stroke and a bit higher compression. Not as much as you get with aftermarket pistons, but more than the dished pistons on the VTR. More compression is certainly better, but you have to get the timing right (not easy with the vtr engine). You will be fine as long as you don't go too far with it.
By far, the biggest difference is in the heads. The RC51 heads have huge intake and exhaust ports and the cam timing is more aggressive. They suffer in midrange power, even with JE pistons compared to the VTR.
I did a side by side comparison on an RC51 engine I built. I liked the VTR much better on the street. But the RC51 is a little stronger at the top end. I could still get away from Dean on the track on my VTR.
The RC51 heads are really designed as a superbike platform with a 12-13k redline. But they are extremely expensive to build to that level.
The more air you flow into the engine, the more power it makes. Ported heads and stage 1 cams will allow the engine to flow much better. We'll have to see what Ozzie thinks when he gets my heads installed.
By far, the biggest difference is in the heads. The RC51 heads have huge intake and exhaust ports and the cam timing is more aggressive. They suffer in midrange power, even with JE pistons compared to the VTR.
I did a side by side comparison on an RC51 engine I built. I liked the VTR much better on the street. But the RC51 is a little stronger at the top end. I could still get away from Dean on the track on my VTR.
The RC51 heads are really designed as a superbike platform with a 12-13k redline. But they are extremely expensive to build to that level.
The more air you flow into the engine, the more power it makes. Ported heads and stage 1 cams will allow the engine to flow much better. We'll have to see what Ozzie thinks when he gets my heads installed.
09-08-2006, 02:09 PM
#34
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They aren't completely different! You can certainly see the VTR's heritage in the RC51's engine. It's just another refinement of the ~1000cc 90° twin. Sure, bore/stroke/etc/etc are different, but the point I made was that the big twins can handle more compression and that was one of the reasons the RC51's make more power. The fact that the two engines are so similar makes this an apples-apples comparison.
09-08-2006, 02:28 PM
#35
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Join Date: Sep 2006
Location: Cherry Point NC
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Random Ignorant thought.
Not something i think id ever try, but does anyone think an engine swap between an RC51 and a Hawk is even possible?
Just something that popped into my head.
Thanks for all the advice guys, i really like the respectfull way opinions are approached, excellent forum!
Not something i think id ever try, but does anyone think an engine swap between an RC51 and a Hawk is even possible?
Just something that popped into my head.
Thanks for all the advice guys, i really like the respectfull way opinions are approached, excellent forum!
09-08-2006, 04:59 PM
#36
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Originally Posted by JamieDaugherty
the point I made was that the big twins can handle more compression and that was one of the reasons the RC51's make more power.
One reason the big twins can't handle as much compression ratio (different than cylinder pressure, which is a fuel, compression, timing thing) is that the cam timing is not as radical as an i4 engine, because they are tuned for a different RPM range. With less timing overlap and lower engine speed, the filling of the cylinders is more efficient. R1s have a 12.5:1 stock compression ratio. A stock RC51 has 10.5:1. My VTR at 12 (or so):1 detonated on pump gas. With a little less ignition advance I may have been ok. But I learned by pushing the envelope.
True the VTR and RC51 are clearly cousins. I've built both. But the RC51 heads are radically different in terms of performance envelope.
I spoke with my friend Zoran, of Twin Works Factory. He builds some of the fastest SV650s in the country. I was at the track and my bike was having some detonation on pump gas , so I switched to race gas and it went away. he asked me what I had done to the engine. When I told him, he said "No wonder it's detonating. Twins don't like a lot of compression. I build my engines with stock compression. They run on pump gas."
Good discussion.
09-08-2006, 06:25 PM
#37
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Originally Posted by RCVTR
I have to respectfully disagree. Not saying you don't know what you are talking about, just a difference in thought process.
One reason the big twins can't handle as much compression ratio (different than cylinder pressure, which is a fuel, compression, timing thing) is that the cam timing is not as radical as an i4 engine, because they are tuned for a different RPM range. With less timing overlap and lower engine speed, the filling of the cylinders is more efficient. R1s have a 12.5:1 stock compression ratio. A stock RC51 has 10.5:1. My VTR at 12 (or so):1 detonated on pump gas. With a little less ignition advance I may have been ok. But I learned by pushing the envelope.
True the VTR and RC51 are clearly cousins. I've built both. But the RC51 heads are radically different in terms of performance envelope.
I spoke with my friend Zoran, of Twin Works Factory. He builds some of the fastest SV650s in the country. I was at the track and my bike was having some detonation on pump gas , so I switched to race gas and it went away. he asked me what I had done to the engine. When I told him, he said "No wonder it's detonating. Twins don't like a lot of compression. I build my engines with stock compression. They run on pump gas."
Good discussion.
One reason the big twins can't handle as much compression ratio (different than cylinder pressure, which is a fuel, compression, timing thing) is that the cam timing is not as radical as an i4 engine, because they are tuned for a different RPM range. With less timing overlap and lower engine speed, the filling of the cylinders is more efficient. R1s have a 12.5:1 stock compression ratio. A stock RC51 has 10.5:1. My VTR at 12 (or so):1 detonated on pump gas. With a little less ignition advance I may have been ok. But I learned by pushing the envelope.
True the VTR and RC51 are clearly cousins. I've built both. But the RC51 heads are radically different in terms of performance envelope.
I spoke with my friend Zoran, of Twin Works Factory. He builds some of the fastest SV650s in the country. I was at the track and my bike was having some detonation on pump gas , so I switched to race gas and it went away. he asked me what I had done to the engine. When I told him, he said "No wonder it's detonating. Twins don't like a lot of compression. I build my engines with stock compression. They run on pump gas."
Good discussion.
Interesting...god ive learned so much, So if i bumped the stock 9:1 Compression up to say 10 or 11:1 do you think id be in danger of detonation? Or do you think a set of cams and head work is all i should do to keep my bike a daily rider/possible commuter?
09-11-2006, 02:41 AM
#39
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Another pro for modding the bike is insurance! I was going to get a GSXR1000 after sitting on every sportbike in 3 dealerships. Then I called USAA for insurance- $3100 a year! I guess every sailor in Norfolk wrecks their sporbikes around here. My VTR1000 is only $600 a year. And it's paid for.
If I wanted to go faster, I'd bore it over a little, high comp. pistons, cams, head work and be done with it. But I'm happy with it for the street- I wouldn't do it unless my engine blows up.
If I wanted to go faster, I'd bore it over a little, high comp. pistons, cams, head work and be done with it. But I'm happy with it for the street- I wouldn't do it unless my engine blows up.
09-11-2006, 08:15 AM
#40
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Moriwaki makes pistons for the VTR that have slightly less compression than the JEs. They are in stock at Big Valley Honda in Reno. The kit comes with pistons, rings, wrist pins, circlips and head gaskets. ~$500 I think. Cams are likely not in stock, but still available. Order early, so you're not waiting during riding season!
I think you'd be fine with that. But don't recommend decking the heads with pistons for the street. You may want to retard the timing a bit by slotting the ignition pickup. I was running a race ignition, which may have contributed to my problem.
I think you'd be fine with that. But don't recommend decking the heads with pistons for the street. You may want to retard the timing a bit by slotting the ignition pickup. I was running a race ignition, which may have contributed to my problem.
09-11-2006, 08:55 AM
#41
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I think twins like compression and respond well to it. Looking around at other bikes, it's apparent that many stock twins have compression ratios around 11.5:1. The SV650 and 1000 and the Ducati 999 all come stock with these ratios, so while I don't think it's true that twins and high compression don't mix, I think you're probably right that the added compression gained by decking the heads makes it more difficult, if not impossible, to run on pump gas.
I just installed JE pistons in my Hawk and it definitely has more go. I'll know exactly how much in a few hundred miles when I have it dynoed. I had what I thought was a jetting problem; the bike was running poorly and cutting out at full throttle and high rpm. I finally remembered that I had forgotten to put premium gas in the tank on my last fill up. A tankful of premium cured my "jetting" problem.
I just installed JE pistons in my Hawk and it definitely has more go. I'll know exactly how much in a few hundred miles when I have it dynoed. I had what I thought was a jetting problem; the bike was running poorly and cutting out at full throttle and high rpm. I finally remembered that I had forgotten to put premium gas in the tank on my last fill up. A tankful of premium cured my "jetting" problem.
09-11-2006, 01:28 PM
#43
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If you search the archives you'll find some threads on cams. I believe rollingalong had a custom cam profile done for him by WebCam. The grind is different from the cams they advertise on their website and is more for a performance street setup than for racing.
http://www.webcamshafts.com/
http://www.webcamshafts.com/
09-12-2006, 09:58 PM
#44
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More thoughts about timing, compression, etc.
I've had a few more thoughts going through my head about things that you may not be aware of, regarding ignition timing, cam timing, compression ratio and cylinder pressure.
A motorcycle engine is very highly tuned and is a great place to learn about race engine tuning. You can throw a bunch of parts together and see how it works. But it's much more interesting to think about how it all works together.
Starting with ignition timing: The ultimate goal with ignition timing is to get the maximum cylinder pressure to occur at about 12-15 degrees after top-center. That way, the crank has rotated past the top and the pressure can start to do work rotating the crankshaft. Before that the pressure is just putting stress on components and any pressure before top-center only creates resistance to crank rotation. So just setting timing to the point where it just stops pinging is not the best for maximum torque. Too far retarded and the volume in the cylinder is increasing so fast that the pressure doesn't get very high. The force on the top of the piston is pressure X area.
Then we come to combustion. In the absence of detonation, the fuel-air mixture burns at a controlled rate. A flame front passes through the mixture and the pemperature and pressure rise during this process. The mixture does not explode - that's detonation. This controlled burn rate is the reason that ignition occurs before top-center.
If the pressure gets too high in the cylinder for a given fuel, the mixture reaches its auto-ignition temperature and detonates, generating extremely high cylinder pressures and bending or breaking things. And the higher the cylinder pressure when you iginite the mixture, the faster it burns. So ignition timing is extremely critical in a high-performance engine. If you change the compression ratio, you should probably retard the timing. The optimum timing and advance curve can really only be ascertained through lots of dyno testing.
That was my reason for going with an HRC ignition. I don't really know much about the actual advance curve, but thought it would be better tuned for a high-compression engine than the stock box. But that gets me to my next point - cam timing.
The HRC ignition has no rev limiter. It is truly built for an advanced, high-revving, high compression race engine, built to Stage 2 specs with peak horsepower at about 12,000 RPM. A set of Stage 1 cams starts signing off at about 9500 RPM, not much higher than the stock cams. So they reach their maximum torque (cylinder pressure) at around 8,000 rpm. Whereas the Stage 2 cams peak closer to 10-11k. So the optimum ignition advance for the Stage 2 cams at 8k rpm was probably too much for running on the sweet spot for Stage 1 cams. That's where I think I got in to trouble.
But with lower compression, the mixture burns more slowly, so where does that put the ignition timing, when you bump the compression substantially? I don't know, but I would guess you'd be too far advanced again.
That's how I understand the problem anyway. Not an expert. Just an extreme inthusiast!
Good Luck all you tinkerers.
Rand
A motorcycle engine is very highly tuned and is a great place to learn about race engine tuning. You can throw a bunch of parts together and see how it works. But it's much more interesting to think about how it all works together.
Starting with ignition timing: The ultimate goal with ignition timing is to get the maximum cylinder pressure to occur at about 12-15 degrees after top-center. That way, the crank has rotated past the top and the pressure can start to do work rotating the crankshaft. Before that the pressure is just putting stress on components and any pressure before top-center only creates resistance to crank rotation. So just setting timing to the point where it just stops pinging is not the best for maximum torque. Too far retarded and the volume in the cylinder is increasing so fast that the pressure doesn't get very high. The force on the top of the piston is pressure X area.
Then we come to combustion. In the absence of detonation, the fuel-air mixture burns at a controlled rate. A flame front passes through the mixture and the pemperature and pressure rise during this process. The mixture does not explode - that's detonation. This controlled burn rate is the reason that ignition occurs before top-center.
If the pressure gets too high in the cylinder for a given fuel, the mixture reaches its auto-ignition temperature and detonates, generating extremely high cylinder pressures and bending or breaking things. And the higher the cylinder pressure when you iginite the mixture, the faster it burns. So ignition timing is extremely critical in a high-performance engine. If you change the compression ratio, you should probably retard the timing. The optimum timing and advance curve can really only be ascertained through lots of dyno testing.
That was my reason for going with an HRC ignition. I don't really know much about the actual advance curve, but thought it would be better tuned for a high-compression engine than the stock box. But that gets me to my next point - cam timing.
The HRC ignition has no rev limiter. It is truly built for an advanced, high-revving, high compression race engine, built to Stage 2 specs with peak horsepower at about 12,000 RPM. A set of Stage 1 cams starts signing off at about 9500 RPM, not much higher than the stock cams. So they reach their maximum torque (cylinder pressure) at around 8,000 rpm. Whereas the Stage 2 cams peak closer to 10-11k. So the optimum ignition advance for the Stage 2 cams at 8k rpm was probably too much for running on the sweet spot for Stage 1 cams. That's where I think I got in to trouble.
But with lower compression, the mixture burns more slowly, so where does that put the ignition timing, when you bump the compression substantially? I don't know, but I would guess you'd be too far advanced again.
That's how I understand the problem anyway. Not an expert. Just an extreme inthusiast!
Good Luck all you tinkerers.
Rand
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