Vboost Delete pros/cons?

[lucasvonpinho]

Hello everyone, I’m new to this forum and I was recently researching some bikes when I stumbled upon the Yamaha V-max. I’m a car nerd first, but I recently started getting more into motorcycles and I cant help but wonder what the benefits are of keeping Vboost when aiming to increase horsepower.

For example, Vtec is similar in the way that it engages at a certain rpm and increases horsepower, but most high hp builds delete vtec and just add bigger cams to make more hp throughout the whole rev range.

From what I can gather most people on this forum are against deleting Vboost and I was wondering why that is?

(By “deleting Vboost” I mean to add a straight pipe in place of the valves, or just hold them open somehow.)

 

[Fire-medic]

You're not too-far north of me.

The Gen. 1 VMax/VBoost is something that made a reputation for an iconic motorcycle which was sold in that version for longer than the Ford Model T was made. 'If it ain't broke, don't fix it.' A few changes to the bike, and you can get a reliable 130 RWHP out of one. Not bad for a bike designed in the early 1980's.

No it doesn't have electronic rider aids. Not even ABS. You have to possess some sense and some skills to use it to best effect. The bike turns in the 11's in a 1/4 mile, with someone halfway decent controlling it. A good rider can make it into the 10's. Jay 'Pee-Wee' Gleason did it 0.64 seconds better, multiple times.

Speed costs money, how fast can you afford? Buy a Generation II for effortless sub-10 second e.t.'s.

A simple 4/1 exhaust and a jet kit can make the trip to triple digits more fun, and you can retain the VBoost. Many guys here like to keep the VBoost operational, though the Dynojet Stage 7 jet kit says to remove VBoost. One advantage to keeping it, you can synchronize the carburetors easier with VBoost.

I had an S2000 AP1 for years, and the VBoost is a lot of fun, when compared to VTEC. The S2000 is now in our son's possession. If I want to compare them, it's an easy trip to his home.

 

[KennyR]

Yes there is a way to bypass the v boost and have all the barrels open all the time. The bike will sound like a big block V8 and get really really bad fuel mileage. Good for trolling bike night but not much else. At least that's what I've been told!

 

[caseyjones955]

I rolled a Kerker 4-2-1 with the Morleys tuning kit and was faced with this choice, I opted to leave the Vboost intact for many of the same reasons FIre Medic mentioned. Mostly because it is a defining feature of the bike, and it does work.

I'm glad I left it intact. It was my intention to keep the bike faithful to it's roots while making other QOL upgrades like stick coils and an upgraded saddle.

 

[MaxMidnight]

I suppose it depends on how you intend to run the bike.
If you only intend to run the bike at or near full throttle then V Boost probably offers little benefit but if you want to (significantly ) increase HP you will also need to spend large amounts of dosh.
But if you intend to keep it on the road that's another matter.

Perhaps you should consider why V Boost is fitted - not to increase power (torque x revs) but to extend good levels of torque across the rev range.
You probably know this, but for those that don't....
You want high air velocity through the carb. venturi as this will give better atomisation of the fuel = more efficient combustion = more energy is turned into work (shoving the piston down).
This can be achieved this at lower revs with a (relatively) small venturi but...
As the revs increase the venturi won't allow a sufficient volume of air to satisfy the engines needs therefore the work done reduces and power is lost.
Of course you could put on carbs with larger venturi but then you would lose bottom end torque...sometimes you just can't win.

V Boost gives you the benefit of small (for the engine displacement) venturi for low down torque and as it opens allows additional air/ fuel from the other carb to help satisfy the requirement of the engine at higher revs. IMO Win - win.
That's not to say it is a perfect system as there will be losses due to various factors.

You can remove it altogether and add a link tube (look up Stage 7 conversions) but this will be at the cost of low end tractability and not being able to balance the carbs with conventional balancing gauges. You also loose the 'adrenaline' rush when V Boost kicks in.
Alternatively you can pull the plug on the V Boost module when the butterflies are open during the test phase but IMO the only benefit is that you can close them again for balancing.

 

[Sean M]

I suppose it depends on how you intend to run the bike.
If you only intend to run the bike at or near full throttle then V Boost probably offers little benefit but if you want to (significantly ) increase HP you will also need to spend large amounts of dosh.
But if you intend to keep it on the road that's another matter.

Perhaps you should consider why V Boost is fitted - not to increase power (torque x revs) but to extend good levels of torque across the rev range.
You probably know this, but for those that don't....
You want high air velocity through the carb. venturi as this will give better atomisation of the fuel = more efficient combustion = more energy is turned into work (shoving the piston down).
This can be achieved this at lower revs with a (relatively) small venturi but...
As the revs increase the venturi won't allow a sufficient volume of air to satisfy the engines needs therefore the work done reduces and power is lost.
Of course you could put on carbs with larger venturi but then you would lose bottom end torque...sometimes you just can't win.

V Boost gives you the benefit of small (for the engine displacement) venturi for low down torque and as it opens allows additional air/ fuel from the other carb to help satisfy the requirement of the engine at higher revs. IMO Win - win.
That's not to say it is a perfect system as there will be losses due to various factors.

You can remove it altogether and add a link tube (look up Stage 7 conversions) but this will be at the cost of low end tractability and not being able to balance the carbs with conventional balancing gauges. You also loose the 'adrenaline' rush when V Boost kicks in.
Alternatively you can pull the plug on the V Boost module when the butterflies are open during the test phase but IMO the only benefit is that you can close them again for balancing.

I modified my V boost to open at 3500, it provides better part throttle response at normal cruising speeds. In other words it feels more "torquey". It does make the bike slower for full throttle operation below 7000. I saw HP/Torque profile someplace years ago comparing stock vboost to always open, the always open lost about 10 ft-lb below 7000. My buddy and I tested it once. He has a stock 07 and I have a stock 01. We did a side by side 2nd gear roll on. He consistently pulled away from me. I then switched my Vboost to std operation and we did it again. I could then pull ahead by a bit. He out weighs by 30 to 50 lbs and he has a larger windscreen so me edging out makes sense.

So as others have said. What you do with Vboost depends on what you want. Go fast or make HD guys jealous.

 

[lucasvonpinho]

Thank you all for your replies!

So to be honest, I actually don’t intend on keeping the engine in the bike, but rather putting it in a smaller car (Think Miata, Mg Midget, Mg B) to create basically a street legal shifter kart. I know this is upsetting to some purists, but it’s just a project that I have been itching to do for a long time.

The V-max is super rad and I think it’s a great candidate for the swap because of the large hp potential and the driveshaft. Another top contender is the V-max’s distant relative: the Fjr1300. My dad has had one for as long as I can remember and given the paddle shifted manual and the driveshaft it would be one of the easier engines to swap. Although, it has basically no high hp support so I would have to pioneer everything myself.

Does anyone have any opinions on whether or not the V-max would be good for a swap like this? I have very little experience with carbs, but it seems to me like they would probably be easier to deal with when compared to efi.

 

[KennyR]

The FJR 1200 engines are used in the legends cars,a small race only class that look like 1930/1940s dirt trackers. I've seen a couple of Hyabusa motors in Lotus seven clones . I would think that the Vmax would work well in a tiny car,maybe with a turbo for extra fun. I could see it in a 1927 track T roadster, but my tastes are weird. Whatever you do have fun with it!

 

[Fire-medic]

Your car your bike your vision. Build it, drive it, and show us what you did.

You know the MGB got the GM-sourced all-aluminum 215 cu. in V8 in a very-sporty car. It cost less-than the XK-E and allegedly it was comparable in performance. That engine was designed in the early 1960's and it was still being used in Land Rovers into the 21st century.

A MGB-GT V8 would have a more-rigid body/frame than a convertible, It would be safer I think. Put a VMax into a MGB-GT and you have a hybrid, light in the nose, so better handling, and if it's a GT, you have better weather protection, and better safety.

You've probably seen the longitudinally-sectioned MGB with a GM LS V8 in it, if you're planning something like this. I think that's just a great example of American hot-rodding.

 

[lucasvonpinho]

The FJR 1200 engines are used in the legends cars,a small race only class that look like 1930/1940s dirt trackers. I've seen a couple of Hyabusa motors in Lotus seven clones . I would think that the Vmax would work well in a tiny car,maybe with a turbo for extra fun. I could see it in a 1927 track T roadster, but my tastes are weird. Whatever you do have fun with it!

The legends cars are one of the reason I’d want to do this build, but they actually use Fj1200 engines and I was to the Fjr1300. I’m not sure of the similarities or differences, but they are both sweet regardless.

I’m against using a hayabusa engine mainly because they are expensive and busa swaps are very overdone. I’m looking to make something super unique that has never been done before and the busa is definitely the opposite of that.

I was unfamiliar with the 1927 track T, but after looking it up I definitely agree that it would be a sick car for the swap. It would also be much easier than a Miata (or other modern car) and it would definitely match the aesthetic of the choppy and American sounding V-Max engine.

I’m glad at least somebody has an appreciation for this, because this idea was not very popular in the Fjr1300 forum lol

 

[lucasvonpinho]

Your car your bike your vision. Build it, drive it, and show us what you did.

You know the MGB got the GM-sourced all-aluminum 215 cu. in V8 in a very-sporty car. It cost less-than the XK-E and allegedly it was comparable in performance. That engine was designed in the early 1960's and it was still being used in land Rovers into the 21st century.

That’s pretty cool man, I had only ever seen MGBs with little 4 cylinders. To that end, if I end up going with an MGB or Midget I would be doubling or possibly tripling the stock horsepower, which would definitely let me get into a little trouble.

Miatas should not be underestimated though, because I have seen many under the 1,600lbs mark which would put them in the same weight class as the MGB and Midget.

 

[MaxMidnight]

I am not an expert in this type of swap but I would have thought that with the additional weight of a four wheel street vehicle you want an engine that provides a good spread of torque?
The Max engine should fit that requirement?...with V Boost!

 

[lucasvonpinho]

I am not an expert in this type of swap but I would have thought that with the additional weight of a four wheel street vehicle you want an engine that provides a good spread of torque?
The Max engine should fit that requirement?...with V Boost!

Yeah that’s exactly what I was thinking.

 

[KennyR]

A miata might be fun but I think underpowered with a Vmax. The hot swap for them seems to be a 5.0 ford in the 400hp range.
Glad you liked the track T.

 

[lucasvonpinho]

A miata might be fun but I think underpowered with a Vmax. The hot swap for them seems to be a 5.0 ford in the 400hp range.
Glad you liked the track T.

I think if I could get 115whp out of the vmax in the Miata that would be fine, but as with all motorcycle into car swaps, I will have to worry about the clutch. As I said before, you can reliably get Miata’s under 1600 pounds with all the body panels which would give this build around a 1:12 power to weight ratio, stock Miatas are around 1:20, and a stock challenger scat pack is 1:9.4. The scat pack is wicked fast by my standards and you can still have some fun in the stock Miata, so I honestly don’t see power being an issue in this swap, especially with the V-max having so much room to grow. I plan on having a 4 to 1 open header and some bigger carbs at some point and it seems like I would be able to get at least 130whp with those modifications (if it were in the bike).