Dyno fun with an 8V G.

[pete roper]

Off to the Dyno this morning.

 

 

Note that it makes more power with the dB killer in than it does with it out, even though its still very rich up the top end.

 

this was with very minor mods, (Termi pipe, drilled airbox and #68 factory map upload.) There will be more to come with a PCV/Autotune but it furels up very nicely in the midrange on part throttle and that is where most of us do our riding. I plan to book some more time when Bett isn't pushed for time and see if I can get more AFR info at partial throttle and different loadings.

 

Pete

[Skeeve]

Off to the Dyno this morning.

 

 

Note that it makes more power with the dB killer in than it does with it out, even though its still very rich up the top end.

 

 

Hey Pete: for the next run, do you think you can get them to list the horizontal axis with something useful like rpm, instead of that ridiculous "km/hr" on your graph above? Failing that, can you post which gear (I assume top) & what the conversion is [6th is a .90 overdrive, right? And what's the ratio for the CARC final drive?.. This is giving me a headache just thinking about it...]

 

Looking good there: what kind of power do you think she'll make when you can eliminate the overfueling at the top end?

[pete roper]

 

Looking good there: what kind of power do you think she'll make when you can eliminate the overfueling at the top end?

 

The dyno print-outs were done for retards who need to know how fast their bikes are. Next time I'll be booking some time to experiment with other areas besides full noise. At the moment it feels like its fuelling very well at mid-RPM/ partial throttle but I need more time to investigate.

 

When I get the PCV and AT fited to my US bike I'll be able to do some meore serious playing but without cam changes I'd think 110 to 115 should be easily achievable. It's not what I'm really interested in though, what I really want is correct fuelling in the midrange to boost torque there as that is what is useful on a ROAD bike. Especially one as heavy and which has as long a wheelbase as a Griso.

 

Pete

[DeBenGuzzi]

is it just me or does the torq curve NOT look very good, numbers aside its a roller coaster

[GuzziMoto]

is it just me or does the torq curve NOT look very good, numbers aside its a roller coaster

I think you are looking at the air/fuel ratio line. I don't think the chart has a torque curve, just hp and air/fuel.

And no, it does not look good.

[pete roper]

No, at full throttle the fueling is crap. At partial throttle and in the midrange it actually feels pretty good but I'll need to actually do some testing on that. On the road in any of the *Normal* riding areas it's very good though and now at low RPM, light throttle there is none of the horrid chattering and banging in the driveline there was before it'll just cruie on a whiff of throttle and pull from there with no problems which is really nice!!!!

 

Pete

[belfastguzzi]

No, at full throttle the fueling is crap. At partial throttle and in the midrange it actually feels pretty good but I'll need to actually do some testing on that. On the road in any of the *Normal* riding areas it's very good though and now at low RPM, light throttle there is none of the horrid chattering and banging in the driveline there was before it'll just cruie on a whiff of throttle and pull from there with no problems which is really nice!!!!

 

Pete

Swap you?

[pete roper]

Swap you?

 

Get a proper dB killer built for your pipe and I betcha after you've uploaded the #68 map made sure the TPS is set correctly, ballanced the TB's and re-set the factory parameters the thing'll run like a champ.

 

The biggest issue with yours currently is that the pipe isn't restrictive enough. I'm convinced that the restriction in the pipe is not only beneficial but neccessary as if it isn't there a goodly chunk of the fresh charge escapes into the pipe, it's another contributory factor to the awful fuel consumption you get with an open, un-baffled pipe. The camming is specifically designed to work with restrictions in the exhaust pipe, even if you stick a PCV/AT on it I'll bet you a bus load of Brazilian swimsuit models it'll still run better with a quieter, more restrictive exhaust.

 

 

There you go! Aquartet of slappery swimsuit models. One of 'em's bound to be a Brazilian

 

Pete

[Slavomir Musilek (R.I.P.)]

1200 8V Griso from Prague, BMC, open airbox, commander, exhaust

 

[mike wilson]

The second runs are a vast improvement, with almost exactly a 10% increase in peak HP. Much smoother curves, too.

[jcbooghs]

Very interesting stuff here!

Pete, at what pipe/tube diameter you think the pipe isn't restrictive enough? And although spilling fuel instead of making HP.

 

I have no idea but what is the diameter of the primary and secundary tube of the 8V?

[pete roper]

Very interesting stuff here!

Pete, at what pipe/tube diameter you think the pipe isn't restrictive enough? And although spilling fuel instead of making HP.

 

I have no idea but what is the diameter of the primary and secundary tube of the 8V?

 

 

It's the baffling in the muffler itself that is important. Pipe length and diameter, (And any taper in the overall design.) that will control the accoustic tuning of the pipe. What I'm convinced is neccesary is actually nothing more than a glorified 'Blockage' to slow down the egress of the spent gasses. "But surely," people will say "You want the gasses out?" and yes, you do but also remember that as they exit the system they are cooling rapidly and conracting so a longer time within the pipe means less volume of gas to flow. Running substantial overlap on the cams with a very narrow included valve angle means that there is a LOT of opportunity for new mixture to exit the exhaust valves on overlap and that is exactly what it will do if it is encouraged to do so. Because the speed of sound is a constant you can only rely on the percussive wave moving back from the end of the exhaust to work to this end over a quite narrow rev range. So trying to use what many describe as 'Back Pressure' but I preffer to think of as a restriction, within the entirety of the exhaust system from valve head to the end of the muffler will have a far greater ability to discourage the expulsion of fresh charge than relying on accoustics alone. Because of the amounts of gas being expelled at different RPM and loadings the restriction within the pipe will also vary due to the density of the gasses being expelled varied by heat.While I'm not certain I would think that this would mean that you could expect a more usefull result over a wider range than you would get relying on percussive tuning alone.

 

I may be completely wrong. But working on those principles the results I'm seeing make sense, to me at least. It is my belief that the engine is timed and it's ability to breathe is designed to work with a restrictive exhaust because that is what is demanded by modern emissions legislation covering both noise and pollutants. While I'm sure you can build a map to make the engine produce bulk power up top I'm convinced that to completely release its full 'Potential' it would need not only a new map but completely new valve timing to make it behave like an 'Old School' hot-rod. I'm sure that someone will, eventually, go down that path and hopefully the results will be spectacular and please them.

 

My aim in everything I do is to maximise the, if you like, 'Base' potential of the machine by exploiting its strengths and minimising its weaknesses WITHOUT embarking on a remanufacturing programme that could cost tens of thousands of dollars. I also think that in this day and age there is no reason for loud, open, antisocial pipes. Especially if we live, as most of us do, in fairly urbanized environments where our actions impact on our neigbors. You can have a bike that sounds GREAT to you, the rider, without having to deafen everybody in the next suburb and if, as in the case with this engine as it is timed now, making more noise also makes it LESS efficient?? Well, if you *have* to go down that path you're a wanker. Don't get me wrong, I love the sound of a well tuned 'Old School' motor but if I had to live with it every time I rode or, worse still, if I had some numb-nuts over the road who several times a day pulled his incredibly noisy and poorly-performing shitheap out and blasted off up the street making enough noise to wake the dead I too, like Mr & Mrs Average, would get the shits. While I'd just go over the road at 4.00AM and do the 'Dog Turd in a Burning Paper Bag' trick to the idiot in question Mr. & Mrs Average will simply vote for politicians who will enact ever more draconian legislation targeting internal combustion vehicles. None of us need that!

 

Also there is more of a challenge in getting the best out of something that has been deliberately engineered in a counter-intuitive way. Every time you have a win it's like you can give yourself an elephant stamp because you've 'Beaten the System'. I know it's puerile but I still enjoy doing that

 

Pete

[luhbo]

No, at full throttle the fueling is crap. ....

 

I'd go even further and reply "No, at full throttle the ARF readings are crap...", the more as the bike obviously behaves quite satisfying.

 

Hubert

[raz]

That's a thought. But a bad AFR reading will almost always show too lean, not too rich. Maybe it's too rich all over the map and reads leaner at lower rpm.

[pete roper]

I'd go even further and reply "No, at full throttle the ARF readings are crap...", the more as the bike obviously behaves quite satisfying.

 

Hubert

 

Yup, that is itching at the back of my mind too. But if the probe is reading lean in the midrange where it obviously is lean why would it give a false reading right at the top? I would of thought with the throughput of gas being higher a bung reading is LESS likely at the top but I'm happy to be convinced otherwise.

 

Pete