350 cylinder head air flow Part II

[smotorboy]

As promised, I've crunched the numbers for 4-valve cylinder heads on a 350's bore and the results are:

A 22% percent area increase on the Intake side and a whopping 81% area increase on the exhaust side.

This takes the valve stem areas into account, and I used four valves that will actually work on a 62mm bore.

Now, this is what it all means, more or less, is a potential power improvement of 25% to 30% over the OEM 2-valve setup IF all the other bits involved (cam, ports, exhaust & intake lengths, etc) work well with the 4-valve breathing potential. No small thing.

22% on the intake is 22% more potential power, but 81% on the exhaust side is usually only 8% or so overall flow improvement (rule of thumb) as the drive pressure is 10 times or more higher on the exhaust side of things...

One would get just as much addition power from big bore cylinders/pistons fitted to the engine with a lot better "bop-about" manners to live with... Cruising along at 35 mph in 6th and adding lots of throttle and smoothly pulling up to speed would be a thing of the past with a full-race 4-valve setup.

As I'm locked-in to using the stock bore and stroke I don't have that option available.

Robert in California

[hendre]

pfew, you got me thinking.... I just aquired the Turbo system from Brian (http://morini-riders-club.com/forum/vie ... f=4&t=1961) so I'm already thinking about changes to the system....
I guess the intake is taken care off by the Turbo charger squeezing in more mixture to compensate for the 22% lack of intake surface... So all I need is a larger outlet valve or two smaller making it a 3 valver

[smotorboy]

Yes, there can be an issue here at large flow rates... I've seen a few pictures of a custom turbo 350 and the factory 500 turbo bike. I assume you have the custom 350 bits?

For the 350, there can be a sizing issue as even the smallest turbos need a minimum exhaust volume to spin up enough to make boost. I rode a 650 Yamaha turbo years ago and it only made boost above 6000 rpm no matter what I did.

Info from the person that rode that turbo Morini would be really helpful here.

I'm quite experienced with turbos and supercharging so if I can be of help please confer with me as needed.
I think the OEM exhaust valve size will work, but it just will not be an optimized situation.

I would plan on (1) dropping the compression ratio and (2) having H2O injection as it will protect the exhaust valve from glowing red hot and will fend off the fuel detonation issues that you will have...

I'm headed down the same path and will start with the stock 2-valve setup ,,,,, Good luck to us both

Robert in California

[hendre]

yes I have the custom 350 bits, the 500 Turbo is in the Morini museum untouched

What I am planning is changing the 350 cilinders for 500's (so bore 69mm and stroke 57mm making it an 426cc) and in the process of lowering the cilinders from 64mm stroke to 57mm reducing the compression to 9:1. And I am leaning to using 500 heads with a smaller 350 intake valve (but keeping the larger 500 exhaust valve). I could keep the original intake valve too but as 500 heads are prone to rupture between the valves (there is 2mm of flesh left between the seats) I could solve this by changing the inlet to a smaller diameter so the changes of rupture are reduced much

Brian assured me the turbo system worked OK back then but ran rough because there was no plenium chamber between the carb and the inlet valves. He also mentioned that the ignition curve on a standard morini was not retarding enough but I will add a Sachse ignition system so I have plenty choises of curves

Once I get going with the build I'll add a topic to the forum so we can exchange ideas

but just a thought, the calculations you preformed, do they also apply to Heron head design? Standard Morini engines are smooth as so I can't imagine the valve calculations of mr. Lambertini were far off...

[smotorboy]

I like your idea about the smaller intake valve and keeping the larger exhaust valve... That, the extra CC's, and a plenum volume should help quite a bit...

The 4-valve calculation are for non-heron pent-roof combustion chambers.... "twist type" rocker arms would be required using a pent-roof design with pushrods........

Great idea about adding a topic,,, I'm in...

I have decided to use my little Roots blower at first, then try the turbo later on...

Good for you diving in on this project,
Robert in California

[EVguru]

What I am planning is changing the 350 cilinders for 500's (so bore 69mm and stroke 57mm making it an 426cc) and in the process of lowering the cilinders from 64mm stroke to 57mm reducing the compression to 9:1.

The 500 uses a 20mm gudeon pin, whilst the 350 uses a 16mm. You used to be able to get 500 size pistons (Sciam) with the smaller pin bore (a set changed hands via the email list recently) http://www.morinispecial.it/joomla/inde ... Itemid=109
I don't know if the 350 liner can be opened up that far, but it can certainly go to 67mm for 402cc. Special liners are available for 72mm http://www.ducati-development-dortmund.de/ or even 82mm http://www.kevinbreedonracing.co.uk/pro ... inders.asp

The 500 barrels are relatively rare and it would be better if you could use 125/250 2C or 350 barrels instead.

And I am leaning to using 500 heads with a smaller 350 intake valve (but keeping the larger 500 exhaust valve). I could keep the original intake valve too but as 500 heads are prone to rupture between the valves (there is 2mm of flesh left between the seats) I could solve this by changing the inlet to a smaller diameter so the changes of rupture are reduced much

500 heads or 501? As far as I know it's only the 501 heads that are prone to cracking because of the larger seats. Were you planning to remove both valve seats, weld up the inlet valve pocket and rebore? I'd be tempted to upgrade from the Steel seats (certainly on the exhast) anyway. Trojan from Columbia Metals seems to be the material of choice these days because of the health risks associated with Beryllium Copper.

Brian assured me the turbo system worked OK back then but ran rough because there was no plenium chamber between the carb and the inlet valves. He also mentioned that the ignition curve on a standard morini was not retarding enough but I will add a Sachse ignition system so I have plenty choises of curves

Does it have a boost linked retard capability? I didnt think it had a MAP sensor at all. Why not use a Microsquirt and get DIY programmable EFI too. There's another system I've seen, complete with all the bits to put EFI on bike from 125cc up, but I can't find the link just now.

[brianh0_4]

Lots of ideas and expense!!!
I think with Turbo charging (not so much supercharging) the power output is extremely variable, the more you spend (time and money) the more power you can get!(up to when it goes BANG )
So a target is needed for your personal application. My original target was Ducati 500 Pantah power, so not a major leap, and thus not any serious mods to the engine internals and usable on a daily basis, not just track or drag strip
If you remember the factory one hardly had any changes and was road usable.
All depends what you want!!

Brian.

[smotorboy]

Brian makes a great point. The more you modify a bike, the less usable it becomes for all-round riding.

All or nothing race bikes are miserable to deal with in traffic...

As I'm only interest in the absolute speed I can wring from this bike, I can sacrifice everything else to get that last little bit...

Robert in California

[George 350]

Good luck in dealing with all the extra heat that this power gives you. Remember every extra 10HP means an extra 15kW of heat to get rid of. I feel you would need watercooling. You could look at lopping a quarter off of a Honda CBR600 or 600 Hornet head, then you would have a high flow 4-valve watercooled head. Quite simple to make up a water jacket on the barrels, although Porsche used watercooled heads and aircooled barrels on their 12-cyl turbo endurance cars in the 70's and it is less critical than the heads for cooling.
Cam drive really shouldn't be too difficult with chain or belt from original cam. Will you install piston cooling jets? All turbo motors I've dealt with have needed them, therefore an uprated oil pump would also be required.

Below are 10 steps to making a fast bike - came off a website from the early days of internet, no idea of the source of this wisdom:
1/ Cut off all unnecessary parts from the bike to reduce weight
2/ Add a fairing
3/ Fit big carbs and a racing exhaust
4/ Go on a diet and shed all unnecesary body weight
5/ Fit a big bore kit
6/ Fit a high lift racing cam
7/ Add a supercharger
8/ Run it on Methanol
9/ Add a nitrous kit
10/ Sell it and buy a Kawasaki 1100 and you will have a really fast bike.

Have fun,
George.

[smotorboy]

George,,, you are sooooooo right on here... I laughed so hard I almost fell out on my chair...

I am doing e-v-e-r-t-h-i-n-g you have listed but #5..

Just Great !

Robert in California