Does anyone know the trans gear ratios for 6th generation VFR800? Which engine is considered better the VTEC or non-VTEC engines? Not meaning to stir up controversy looking at this engine for a specialty purpose as stated in another post. Thanks, Wade Finley :blink:
For a racing application the fifth generation would probably be best, as the valve system in the sixth generation was design for reduced noise and emissions and does not increase performance.
Busman: Thanks for the help with the gear ratio's. Now what years are considered 5th and 6th generations? Are engine parts interchangeable (except for the vtec portions)? I will be building this engine for dirt track racing in Micro-Sprints. Our rules allow up to 619cc in most parts of the nation. I will be sleeving the VFR800 down plus changing the stroke some. I have created an album of our type of race cars so everyone can see what I am trying to accomplish. Most cars are powered by R6's and CBR600R's, very high HP (105-118HP)but not a lot of Torque. We run alcohol with either FI or carbs, no limits as to modifications internally. Our tracks range in size from 1/10th to 1/5th of a mile. With the proper build I hopefully will still be close in HP to the competitors but should have a large Torque advantage. Hope some on this forum can be of help with any and all info. All info will be greatly appreciated. Thanks. Wade Finley
'BETTER' is so subjective. More costly to maintain unless you do it yourself . May not sound as good as a pre-6'th bike fur to cams, however, bike performs at 7K when VTEC kicks in. You really feel it in the seat of your pants Oh yeah - Link brakes and ABS - awsome.
Getting 619cc of V4 to produce 120hp will be a challenge. Try Dynamohumm.com, those uys do big bore kits for VFR's, so they might know a hing or two about cylinder sleeves. The main issue I see with the motor is the cams; where would you get a profile that would deliver that kind of power? Would you make them? In that case, give me a call... ported heads and fat cams sound like recipe for success...
Thanks for the info everyone. VFRMonkey, this info was provided by Richards Engine Development. He suggests I well may find that stock cams with altered timing positions (retarded intake/advanced exhaust) might offer the torque increases I am seeking at the appropriate RPM's. He suggests that I might also consider altering the VTEC system such that the "switch over" to 4 valve operation is delayed... again in the interest of bolstering low end torque off the corners. I will see how this works, if it doesn't I will try "fat Cams", from possibly Webcams. I had already planned on porting and polishing the heads. Am hoping to kick some serious R6 ass with this project. Will keep everyone updated. If anyone else would like to share their insight and expertise I would appreciate any and all advice. Wade Finley :thumbsup:
I don't think there is much parts interchangeability between the 5th and 6th gens. Besides the differences in heads due to the Vtec stuff, the 6th gen lost the gear driven cams in favor of chain drive. Good luck and keep us updated. :thumbsup:
Tyrroneous: Which would be better for my particular application then? 5th gen with gears or 6th gen with chain driven cam gears? All of this info is great and I really do appreciate everyones imput. Wade
UMSRASupporter, Apr 11 2005, 11:13 AMTyrroneous: Which would be better for my particular application then? 5th gen with gears or 6th gen with chain driven cam gears? All of this info is great and I really do appreciate everyones imput. Wade
Don't quote me on this but I believe honda dropped the gear driven cams due to weight. They had already pudged the 6th gen frame out a little bit and to keep from making the new vfr too porky, they saved some weight on the motor by going to a chain driven cam set up. Weight wise, you might be a few pounds ahead by going with the Vtec motor. But, you gain complexity at the same time. You already mentioned playing around with the Vtec engagement...so maybe this is right up your alley. If it were me, I'd probably go with the 5th gen because the valve train is so much less complex. From a racing standpoint, I don't know if chain or gear driven cams are better... but the racing forefathers of the 5th gen did have gear driven cams, so maybe that is your answer. I know, I'm not much help, am I. :unsure:
Actually you and everyone else has been a great help with the info. I really appreciate how everyone is willing to help my project along with helpful tips, etc. Thanks again. Wade :D
Yes the gear driven cams went away in 02 when the VTEC came in. There is virtually no difference in power from a 5th gen to a VTEC, just very slight changes. For that fact you might be better off with a 5th gen as its less complicated, no telling what can happen with a VTEC if its tuned polished ported then raced for an extended period.
There have been reports of cam chain tensioner failure just on every day riders. Gears are heavier though and spin up slower so there are a few things to consider. You might even want to consider a wrecked 400 and bore it out.
HispanicSlammer, Apr 11 2005, 02:59 PMYes the gear driven cams went away in 02 when the VTEC came in. There is virtually no difference in power from a 5th gen to a VTEC, just very slight changes. For that fact you might be better off with a 5th gen as its less complicated, no telling what can happen with a VTEC if its tuned polished ported then raced for an extended period.
There have been reports of cam chain tensioner failure just on every day riders. Gears are heavier though and spin up slower so there are a few things to consider. You might even want to consider a wrecked 400 and bore it out.
Slammer: I checked on doing a 400 bore out even investigated the old 500 Interceptor. Not enough meat in the cylinder walls to take it out to where I need. Thanks for the info though. This is getting to be very involved but that's what racing so fun. It is something to consider tho on the cam chain tensioner failing. Keep the info rolling in guys I really appreciate everyones insights. Wade
You've decided to sleeve the 5th gen 781cc V four? Great.. I think that's what I suggested!
Another big advantage is that the VFR800 had cylinder sleeves in it's block, so you can just machine the sleeve, and press it in! Now the stroke modification... that's a little more involved. Either welding up the crank, or turning on new centers and changing rod length. What are your plans?
What are your plans for fueling? The stock VFR800 has a nice fuel injection system, but I'm unsure what you'd have to do to get it to live with the 619cc displacement?
By the way, I understand '94 RC45 (VFR750RR) cams will fit the 5th gen engine. That should be plenty wild, as the RC45 made about 150 to 160 hp from 750 cc in full factory race tune! (which direct correlation would yeild 132 hp 619cc engine!) Although, this might not be most condusive to your goal of high torque?
WERA910, Apr 11 2005, 07:51 PMYou've decided to sleeve the 5th gen 781cc V four? Great.. I think that's what I suggested!
Another big advantage is that the VFR800 had cylinder sleeves in it's block, so you can just machine the sleeve, and press it in! Now the stroke modification... that's a little more involved. Either welding up the crank, or turning on new centers and changing rod length. What are your plans?
What are your plans for fueling? The stock VFR800 has a nice fuel injection system, but I'm unsure what you'd have to do to get it to live with the 619cc displacement?
By the way, I understand '94 RC45 (VFR750RR) cams will fit the 5th gen engine. That should be plenty wild, as the RC45 made about 150 to 160 hp from 750 cc in full factory race tune! (which direct correlation would yeild 132 hp 619cc engine!) Although, this might not be most condusive to your goal of high torque?
Michael
Michael: I haven't definitely locked into 5th gen but it is beginning to sound like way to go for what I am wanting. Checked with Carillo Rods and they can make a set of knife edge rods for me 1mm longer. I will have to take the Factory FI to the guys that change them to alcohol to get them reworked. These cars use a lot of fuel and air mixture so factory units might work well. I have already taken my hood to a fiberglass man to build a ram air induction into its snorkel. I would think with the V4 configuration that even at high HP it would still deliver more torque than a Yamaha R6 or CBR600 Honda. At least that is my understanding from everything I have read when researching this project. There was an excellent article posted on the net a while back that discussed just such an issue and it concluded that a V engine will always build more torque than an inline engine. If this engine can utilize the RC45 cam to develop more HP at the same time all the better. Should really kick some serious yamaha butt, lol. :thumbsup:
I just thought of one thing that I might be a serious issue, valve clearance after being sleeved. Anyone know how how much clearance between the valves in the stock head and stock cylinder? Certainly don't need bent valves, etc. Also has anyone heard of anyone making mechanical advancers to set timing on the intake and exhaust. Or can this be accomplished with the stock ignition or a Power Commander? I really do appreciate everyones ideas, help and guidance on this project. If I was a rich man I would buy everyone that has gotten into this discussion a cold beer. :beer: But alas, I am just a poor working man that is about to get a lot poorer I think putting this engine together, lol.
tyrroneous, Apr 12 2005, 05:20 AMDon't quote me on this but I believe honda dropped the gear driven cams due to weight.
Look - here I am quoting you! :rolleyes:
Actually, I don't believe weight savings had much to do with it.
The 5th gen VFRs had the cam drive moved outboard, and this makes the engine a LOT noisier. The more I think about it, the more it seems apparent that Honda dropped the gear-driven cams and introduced the VTEC solely for noise and emissions compliance. What else did the changes do? Might have saved a little weight, maybe some cost, but it certainly added no more power or fuel economy (the latter was achieved through the 'closed loop' on the ECU/EFI).
End of thread · 17 posts recoveredWayback Machine snapshot 17 Apr 2005