Another newb question

[HDKILA]

what is the difference in tboost and vboost?

do all the vmax's have the vboost/tboost?

how come people say the 85 and 86's were the fastest?

can you mod the bike to make the vboost come in sooner?

Abe

 

[maleko89]

Vboost is a stock feature. At 6000 rpms a pair of valves open in the intake manifold that allow each cylinder to be fed by two carbs instead of just one. Tboost is a simple mod that tricks the vboost controller into opening at 3000 rpms instead.

85's being faster or powerful is just a rumor. 85's did have a bit better exhaust but were changed in '86 due to emissions. To compensate, Yamaha increased the size of the vboost by 1 mm.

 

[naughtyG]

As Mark said, T-Boost is a mod. Simple electrics really, fooling the system by looking at two coils' pulses instead of one, so the V-Boost valves open earlier. You can buy T-Boost as a kit off eBay for about $45, and some are switchable which I think is great as you can then have it on or off at will. You can also make it yourself with a soldering iron and a few components if you're so inclined - only costs a few dollars this way.

I've also read somewhere that T-Boost does nothing more than detune your engine by giving it an overly rich mixture, but that didn't make sense to me as it's fuel & air that go through. Here's some dyno data:
http://vmax.lvlhead.com/tips/tboost.htm

All stock V-Maxes come with V-Boost, but some have it removed, typically when they get fitted with Dynojet Stage 7 kits. Not exactly sure why, but I assume that with Stage 7 there so much air/fuel going through that V-Boost just doesn't make sense anymore.

In the end, if you ride a V-Max you know how mad the V-Boost surge is, and it sure is lovely, but you gotta ask yourself - do you really want that surge that much earlier? I know that I'm often leaning over or on slippery surfaces at lower revs, and I think that having that rush at 3000rpm could make me lose control quite easily in those conditions!

I'd still like to try it, but if I do I'll definitely go for the switchable version!

 

[Rayvin53]

I think those dyno runs support NOT changing the stock Vboost setup. Other than having the hp and torque kicking in at lower revs (engine lugging revs), you loose a bit of both overall...unless am I reading them incorrectly.

 

[Rusty McNeil]

Eliminating mine has never had any ill effects.....nor will I say that it made it any better...it's just gave it a reallly nasty idle that everyone digs.....It does not make the bike run rich.....I tested it when my carbs were stock.....I can easily open and close my butterflies and watch the A/F guage and A/F doesn't significantly change either way.....At WOT in the extreme upper rpms I can see where it does effect air fuel because that is the place where the engine, if not given two carbs to feed from, starts to become starved for air and manifold vaccum starts going up again due to the engine sucking harder than the carbs can feed it....

I do not have stage seven, am running smaller than stock mains, (DJ160's) and two coils out of the slide springs and stock other than that...

I've run a wideband A/F guage/monitor and can testify that it does not effect a/f ratio, anyone who says it does anywhere except at throttle openings in the higher revs I think is misguided .

A perfect carb, sized right, is going to give a consistent a/F ratio from lower revs all the way to the higher revs,

The Vmax carbs are in truth undersized for a 1200cc bike, but the give such good throttle response at lower revs because of that.

The point of Vboost is to allow both carbs to feed enough air/fuel to supply the motor at higher rpms, yet still be small enough when used individually that air velocity is quick enough to give good crisp throttle response at lower revs..

The engine is going to suck the same amount of air whether vboost or not, if no vboost is in place, and crossover tubes are in place or your butterflies are wired open like mine are, its going to be the same volume of air, moving slower, through both carbs, if vboost is in place that same volume of air is going to be moving faster through one carb when vboost isn't open yet.

The only possible way that open vboost all the time hurts performance is that off idle throttle response, and throttle response in the lower revs, is slightly effected. I won't deny that seemed to be the case on my bike, and that it seemed that I had to relearn the throttle, clutch dance when starting from a dead stop....

But the bike will stand stand straight up in a first gear power wheelie with no use of the clutch...


Did I mention the really nasty idle????:biglaugh: