Compression ratio

[Angelfire]

Anyone know the Compression ratio of the 70cc kit Double ring piston ?

[XPS1210]

it totally depends on the kit... guessing an average 12:1 or so...

what kit specific are you asking about?

[Angelfire]

MHR Replica 70cc kit one with double ringed pistion

[XPS1210]

Printing versionSPARE PART LIST
BRAND / Models
ALUMIN-CYLINDER KIT Ø47 pin Ø 10 MHR REP
code = 31 8437


IF the CRANKSHAFT HAS a PIN Ø 12 INSTALL the PISTON 34 7849



MHR REPLICA CYLINDER KIT

The MHR Replica line of cylinder was created especially for the International Scooter Trophy * 70cc Automatic Class. These cylinder kits were designed to guarantee maximum performance in this category, while at the same time assuring extremely long product life.

In order to guarantee these special characteristics, Malossi MHR Replica cylinder kit have pistons with two chrome-plated rectangular segmants and a compression ratio of 13.8:1, plus torque value of 7.35 N.m. (o.75 Kgm) at 8.000 rpm and power of 6.6 Kw (9 C.V.) at 8.500 rpm.

The MHR line is the results of Malossi's many years of experience in European and National competitions. These new cylinder kits are composed principally of cylinder- piston * ring * head.


http://malossi.com/img_prodotti/31%208437/31%208437.jpg


ask and you shall recieve....

it looks like 13.8:1

Not sure what 6.6 Kw is converted into Hp... I'll try and find that out as well...

If you looking at the MHR replica instead of the MHR cylinder... don't... it's nothing like the MHR other than the name... it's about half the power! and not as good... spend the extra cash and do it right... if you want a "race set up"...

[XPS1210]

found it... 6.6KW is equal to 8.85Hp...

this is the cylinder I was gonna get but decided on the Corsa/R as it was much higher HP for the same price...

only down side, it's a cast cylinder...

So take your pick... but like I said, if you are planning on the power... go with the MHR cylinder not the replica...


here is the info on the MHR cylinder

ALUMIN-CYLINDER KIT Ø 47,6 pin Ø 12 MHR
code = 31 8440


TECHNICAL FEATURES cylinder kits

CYLINDER
- Material: special aluminium alloy with high percentage of silicon and titanium that guarantees exceptional strain strength even at high temperatures.
- Heat treatment: special quenching and stabilizing treatment that gives the material increased toughness and strength, guaranteeing that mechanical and size specifications will remain unaltered for temperatures of up to 250 °C.
- Chip-forming machining: carried out on NC machining centres with extremely-limited size and shape tolerance (roundness, perpendicularity).
- Inner surface coating: effected using silicon carbide on a nickel matrix with heat treatment that guarantees extreme hardness (around 600 HVO, 1/5) and excellent resistance to wear.
- Internal machining of cylinder: using special machines that allow a degree of finish on the cylinder barrel walls whose roughness corresponds with the angles set at the design stage (grinding process using special stone).
- Port and exhaust diagrams: designed and manufactured especially for racing. The definition of the port and exhaust diagrams has requested considerable effort on the part of our engineers both on engine test stands and the circuits on which the trophy is held.

PISTON
- Material: special aluminium alloy with a very high percentage of silicon and titanium that guarantees both excellent heat resistance and strain strength upon temperature variation.
- External coating: graphite coating that guarantees a very low friction coefficient
- Structure: reinforced in order to offer resistance to the stress suffered by cylinder units used for top-level competition, but at the same time light enough to reduce inertial force.
- Ring: 1 mm nodular-cast-iron single ring with rectangular cross section and hard-chromium coating on outer surface.

PISTON RINGS
- Rings in very strong modular cast iron with ground, wear-resistant, hard chrome metal-spray coating on the contact surface.

HEAD
- Material: special alluminium alloy with a very high heat exchange coefficient.
- Geometry of heat exchange surfaces recalculated and increased.
- Combustion chamber completely-designed to obtain a high compression ratio (15.8:1) with a very high turbolece.
- Machining: numerically controlled machines.




Not sure why but they don't list a HP rating on this one... but the compression is 15.8:1

and single ring is better than 2 rings... or even 3....

http://malossi.com/img_prodotti/31%208440/31%208440.jpg

[Angelfire]

Well I know the Single ring is better however I do want it to last awhile me and Erich both talked about it for about a hour today and yes the single ring has higher Compression ratio because the tolorences are alot smaller and the single ring pistion. Now if the tolorences are smaller your more likly to nuke the motor that and you will probally Foul out plug like mad that and tell you the truth there really is not a big diffrence.

[XPS1210]

no... the MHR cylinder is not anywhere near 9hp... it's more in the range of 15+hp...

it's the compairable cylinder to the Evolution cylinder and it's 17Hp...

so... yes... with the higher compression and such, it can wear faster... however, if you tune it correctly it will last a while...

Erich and I spoke about the MHR and MHR replica as well... I choose to not get the MHR as I didn't want to mess with the crank at the time...

I'm VERY happy with my Corsa/R which is rated at 11.5Hp...

get my drift... I can bet you the MHR is more like 15-18 HP range... so there is a HUGE difference...

[Angelfire]

Also with the higher Compression ratio you will have to burn better then 93 oct well you could burn it but with that ratio you will probally here alot of Ping outta the motor ping is where the fuel is compressed and Detonates before the spark plug gets a chance to go off resulting in fouled plugs and you would have to run atleast 110 oct fuel which I have lots of in order for the motor to run cooler and so it did not ping.

[pinkymingeo]

8.85 is, amazing for a manufacturer, not unrealistic for a (very) well set-up MHR rep. You'd be very happy with that power. Not for 2 grand, but you'd be happy. Polini's claim of +11 for a Corsa is science fiction. The MHR Team/Speed out-of-the-box, with the right pipe, set up properly, should do in the 13-14hp range. More power is possible, but the cylinder must be tuned. A scooter with that kind of horses is very, very fast. Operating in the 13-14K range takes it's toll on components, though.

[XPS1210]

okay... I'm not gonna try and talk you out of it... but from the parts you listed before... you had a KICK BUTT set up... now you are back at everyone else's level... simply put the cylinder will be the weak link if you order everything else...

oh yeah... check with erich and make sure the MHR pipe will work in the RPM range of the MHR replica cylinder...

so you stay in the power band and don't over spin the cylinder...

[XPS1210]

Pinky... the MHR replica compaired to the Corsa/R is not even a competition...

The corsa/R has bridged port exhaust... the transfer and exhaust ports are ported from the factory...

Even if the 11.5 is on the high side... it's still going to be better than the 8.85 on the MHR replica and the costs are the same...

My point is... don't expect the MHR replica to be "gravity breaking" like the MHR or evo set ups....

[pinkymingeo]

The LC operates much better at high compression (another advantage). With milled T6 head I'm very close to MHR/Evo squish and compression. I read 160lb on the gauge. Stock T6 reads 135. I tried that kind of compression on the AC and couldn't get away with it. The engine rattled badly. The LC has no problem with it at all.

[pinkymingeo]

I agree with you that the Corsa is a much better cylinder than the Rep. It's a good cylinder, period. 11.5 is a whole lot of horses, though. Remember that stock is around 4. I know a guy with a 9.5hp (dyno) scooter that does 75mph with tall gears. I can't imagine the rush from one of those 17-18hp monsters the Europeans ride around (the block before they rebuild them).

[wideopen01]

I agree with you that the Corsa is a much better cylinder than the Rep. It's a good cylinder, period. 11.5 is a whole lot of horses, though. Remember that stock is around 4. I know a guy with a 9.5hp (dyno) scooter that does 75mph with tall gears. I can't imagine the rush from one of those 17-18hp monsters the Europeans ride around (the block before they rebuild them).

WHen u guys say 11.5 waht r u talking about...to the rear wheel or to the Motor....their is a big diffrence ya know...i am in the process of building a honda dio motor...im going to have a 72cc corsa kit that has work done to the cylinder,30mm OKO carb,Matching manifold,Polini reeds, MAllosi vair with belt,adjustable clutch,with a SEF CRANK,it should have 12-15 HP to the rear wheel,i will do dyno specs,

[Angelfire]

The Hp ratings are not what they acually put out it is just what they are rated for say if you got the cdi box and wanted to pump alot of Rpm's then yes you would want a 15 - 18 hp rated kit but if your pumping the same Rpm's you will have the same power maybe a diffrent powercurve due to the Compression but over all you will have the same HP.

As soon as I get the parts I will put it on our Dyno :) then I will give ya the specs :)

[smokin]

I agree with you that the Corsa is a much better cylinder than the Rep. It's a good cylinder, period. 11.5 is a whole lot of horses, though. Remember that stock is around 4. I know a guy with a 9.5hp (dyno) scooter that does 75mph with tall gears. I can't imagine the rush from one of those 17-18hp monsters the Europeans ride around (the block before they rebuild them).

I agree with you the corsa is better than the rep.But I have a question when they(the companys) rate these cylinders do they rate it to the rear wheel or at the crank???
And how can they rate it and say that this has this and this has that because you can have a million different setups on the same kit???

[Angelfire]

Ok I will get all my Parts next week friday or saturday. Saturday I will have it tuned and put it on the dyno then I will Call erich up and Next day air the MHR single ring And the Evo then I will try those out but the MHR rep puts out more then 8.8 spoke to erich on that one about 30 sec ago lol. And still he said there is not a huge diffrence also said going to the mhr single ring I would be replacing pistions every 20 hrs even my Dad told me single will eat up your motor no matter how well your tuned but like I said the Dyno will have this all solved between all the heads shortly

[pinkymingeo]

The #s I and the manufacturers are talking are at the crank. Subtract about 2 for the rear wheel. 30mm is a big carb. The only 13hp at the wheel scooter I've seen on the dyno is Steve's. He was running, I believe, an MK cylinder ported/C20/28mm OKO/inner rotor ignition/all the goodies. That's a whole herd of horses.

[pinkymingeo]

Single-ring doesn't have squat to do with wear. The T6 is single ring and can go 10K miles no sweat. RPM and heat have a lot to do with wear. People associate single ring with short life because it's single ring cylinders that are operating above 13K. Not many 2-ring cylinders do that.

[XPS1210]

sorry... I just have to ask.... angelfire... how old are you?

[Angelfire]

pinky ask any performance shop about single ring pistions and they will tell you about the wear factor. The only advantage of the single ring is you basically use less hp to make more hp due to the thinkness of the ring and most single ring pistons are acually oval shaped to keep the friction down. Both me and my dad run a performance shop dealing with 2 stroks Race snowmobiles, dirtbikes and drag cars and we use single ring pistons in our snowcross sleds change them every 3 races if we don't they they explode.

Still not a huge diffrence between single ring and double right very slight yes but not huge or even noticable like everyone is saying.

[Angelfire]

oh btw I am 22 years old

[Angelfire]

One last thing to add 10k miles outta a single ring piston is a slim to no change correct me if I am wrong but you would basically have to baby the hell outta the thing to get 10k outta one but on the flip side of that lets say you did get that much outta one do this assuming you did a Compression test on it when you put it on take another Compression test after 10k bet you it changes ALOT no matter how good you tune it. That and you will have a extremly noticable power loss after 2 to 3k even if you baby it due to the wear and by even 2k miles you will start to have a Harmonic in the motor which is really not good at all and a Harmonic comes from the piston ring going up and down and the ring acually boeing in and out of the exhust port bridged or not and it does it so fast it acually turns into a radio wave thus causeing Very unstable motor and basically on brink of total melt down.

PS I will take a pic of a single ring piston I took out of a motor that had a harmonic in it hehe kinda looks neat. :)

[XPS1210]

you have to do ring changes on them... but a single ring cylinder, if tuned properly will last as long as the scooter will (in some cases)...

it all depends on tuning and how you ride and maintain it... a ring change every 2500 or so miles is no big deal... at $10 or less for the ring...

It's all good... if you want 2 ring then the evo and MHR are out of the picture....

[Angelfire]

you are right Jered the whole part on How you Ride is the thing I race motocross so it is gonna be WoT most times that and I plan on doing a long ride with it about 200 or 250 miles non stop 1 way well stop for gas hehe so I kinda am wanting the whole stable motor thing regardless if I lose 1 hp outta the deal.

Now in reguards to your evo you got which is 1 ring have you done any testing with it that or have you ever had a single ring piston and testing it on open road not garage lol if not what are you basing your knowlege off of ? Please don't tell me it is off other peoples remarks because thats really not the way to go about it like erich told me it is like a Ford Chevy thing some swear by fords some by chevy wait your a dodge love I belive lol well you can swear to just at your dodge :) hehe but lets put this war to rest on a good note :)

[XPS1210]

actually I think all of the 3 brands you mentioned all have their problems...

with that being said... each type of cylinder has potental problems... 2 rings... have "ring flutter, harmonics" issues more than single ring.

I don't have an Evo, I have a 2 ring Corsa/R which I got due to not "HAVING" to change the crank... I wanted a simple install "ported" cylinder... which the corsa/R is perfect for what I wanted...

I will still eventually upgrade the crank, but it's gonna be a while... like 6-8 months or so... I have to move first then I'll worry about more mods...

Anyway, It's all a matter of what you feel comfortable with and how you plan on riding and tuning it...

IMO the Evo and MHR are fine for "high RPM" use... probably more so than the 2 ring little brother cylinders...

Spinning the corsa/R or a MHR replica at 10500 RPM's is just fine... but I'd never want to spin one at 13K like the MHR or Evo does....

[Angelfire]

hehe Finally we put this to rest thank you Jered lol

[XPS1210]

yeah.... WE DID IT! ROFLOL!

[str8dum]

I wouldnt wanna ride a race tuned scooter 200+ miles at one trip, esp if it was an AC cylinder. You'd have to stop 5-7 times for gas. And I cant imagine that 3+ hrs of riding at 10k+ rpm would have such a $$$ cylinder last very long.

Provo can get all that high end cylinders? I mean if so, why not go with a Hebo Manston and call it a day?

[wideopen01]

I wouldnt wanna ride a race tuned scooter 200+ miles at one trip, esp if it was an AC cylinder. You'd have to stop 5-7 times for gas. And I cant imagine that 3+ hrs of riding at 10k+ rpm would have such a $$$ cylinder last very long.

Provo can get all that high end cylinders? I mean if so, why not go with a Hebo Manston and call it a day?

Exactly...and you guys know about thoes hebos...they are a BEAST......but kinda pricy :naught:

[Angelfire]

hehe I am not worried about it being AC and getting to hot after 200 miles because 1 I am having a special vent made which will act as kinda like Ram air except it will be blowing on the motor.

2nd thing is I am gonna run 110 oct Leaded race gas which burns alot better and much cooler. Also if your wondering how I am gonna get 110 oct when I go on my trip lol 2 freinds are driving up cause they need to pull the campers hehe so they will be my moblie gas station that or I will fill with 93 oct and add some oct boost :) leaded oct boost.

3rd I also am putting on a ETG gauge ETG is exhaust Temp Gauge so I can see how hot it will run :)

[Lennox]

3rd I also am putting on a ETG gauge ETG is exhaust Temp Gauge so I can see how hot it will run :)


about what temp are you gonna tune to? 1100F or so?

oh, and its EGT...... here is the one I have on my waverunner http://www.racepak.com/ProdFrame.html the hottach pro!

[Aviatrixie]

I think he means an EGT (exhaust gas temperature) gauge. My jet has 3 of them... one for the left engine, one for the right engine, and one for the APU (auxiliary power unit) which is actually a small jet engine that is used to generate electricity and provide high pressure bleed air for air conditioning and engine start on the ground (and in flight in some cases).


I've never heard of an ETG gauge. ;)

Erika (being a smartypants)

[Lennox]

Erika, what the normal operating temp on the jet engines?

[Aviatrixie]

Len, the normal EGT in flight would vary, but max egt is redline, around 900 C. Max allowable start EGT is 725 C and idle is around 350 C to 400 C. We do everything in celsius so remember... 100 C is 212 F.


Erika, what the normal operating temp on the jet engines?

[pinkymingeo]

Aviatrixie is giving us a clue to the final solution. Turbine power. There are plenty of small ones that would fit the frame. Just need a 400:1 set of gears.

[Aviatrixie]

LOL Can you imagine a turbine powered scooter?!!! You could always use that tiny jet engine Jim Bede used in his homebuilt jet kit, the BD-5. Be better to use a turboprop engine tho... but I don't know of any that are small enough to use in a scoot. It would be amazing!


Aviatrixie is giving us a clue to the final solution. Turbine power. There are plenty of small ones that would fit the frame. Just need a 400:1 set of gears.

[Angelfire]

Duh lol sry EGT lol had a long day today :)

[Angelfire]

As for what I am gonna tune it for I really am not sure kinda need all the parts before I can really dial it in. That and I should get the parts next week friday or Sat I will install them as soon as I get them then tune it based on outside temp which is cold now and Humidity which is usally dry in winter.

with the EGT :) thats gonna help me figure my jet settings as well lol that or I can be a lazy ass and just go into our computer and put in motor CC carb size, bore and a bunch of other numbers and it will give me a selection of jets based on Outside Temp. But it is a pain in the butt to get all the number so I will doit the fun way Trial and error :)

[wideopen01]

Also with the higher Compression ratio you will have to burn better then 93 oct well you could burn it but with that ratio you will probally here alot of Ping outta the motor ping is where the fuel is compressed and Detonates before the spark plug gets a chance to go off resulting in fouled plugs and you would have to run atleast 110 oct fuel which I have lots of in order for the motor to run cooler and so it did not ping.


??? i think u mean knock...if ur motor pings it means that the piston is hitting the top of the head

[wideopen01]

angelfire...how r u going to make a AC engine cooler...Because im trying to keep my motor temp cool and steady like a liqued cooled motor...anybody have ideas on how to make a aircoold motor cooler

[florida derbi rocket]

wideopen.....You gotta see if you have a path between your panels for some Ram Air action..(under the Frame panels) this is exciting to me..I found a couple ways for Air to get to my 340ci Duster Mopar..you have to find some ducting that could squish under there..and make a grill..I am gonna look at my Derbi closer now...you brought back memories!!...Im sure there has to be some square 1" x 3" ducting available somewhere on the web..Damn This is what Tweaking is all about!! :D John

[pinkymingeo]

The fan moves enough air through that shroud to blow your foot sideways. When you remove the stock airbox you see how much air comes out that vent hole. There's no good way to force air into the shroud. The fan will overpower ducted air, you'll mess up your cooling flow, and the engine will overheat. If you want to run cooler, richen up or go LC.

[Aviatrixie]

Actually, "knock" and "ping" are both industry "jargon" meaning predetonation. If your piston is hitting the top of the head it's called "immediate mechanical self-destruction".


??? i think u mean knock...if ur motor pings it means that the piston is hitting the top of the head

[XPS1210]

yep... You tell em Avia...

I didn't want to get into this arguement...

This is also associated with "desieling" where a vehicle continues to "roughly run" when the vehicle is shut off... It's caused by the engine being so hot that it continues to burn the fuel in the engine until it finally cools off enough to stop...

My dad's old caprice classic did it... and the only way to get it to stop "running" after the key was off was to floor the gas... and dump excess fuel into the cylinders to cool them off....

[Angelfire]

Heh thanks for covering the ping and knock and what they are. Wow if Ping ment the piston was hitting the head lol I would have blowen alot of damn motors up :)

Now as to keeping the motors cooler you are right a ram air system would not work if it just blew right at the font of the motor due to the power of the Fan it has on it already yes it would mess the flow of the ram air up however if you run your ducting or whatever you use to the other side and acually have it blow on the oppisite side the fan is on with out blocking the exsiting fan it will run much cooler.

Let me acually take a look at my zuma once and see the best way to go about it is without messing up what is already there as well as making it look good thats another reason I did not go LC is cause it looks like complet **** after you put it on along with the extra weight and other thing like not being able to hide the cooler without blocking air flow I took a look at what that one guy did with his LC by making a peice for it and putting it up front you would think that was smart to do but you have to remember you have to be able to turn the bars so now you got a cooler on the front of your zuma with long hose so you can turn not knowing if your kinking the hose when you turn that and coolers are not sopose to really move that much as in side to side cause Cooler does not function properly will not disapate heat as well and it is harder on the pump this is why they are not on the very front of Bikes or dirtbikes.

[Angelfire]

oh Knock is when you strech a valve in the motor or your rocker arms come loose :) couple other things to

[pinkymingeo]

LC adds little if any weight. The radiator weighs ounces, the pump maybe a pound. Maybe a pound and a half of water. On the other hand, you ditch the shroud and fan. Tiny difference for lots more power.

[str8dum]

The headlights and the radiator are stationary. No kinks in my hoses when i turn the wheel.