Want to do HC pistons - is porting necessary?

[parkcrf]

I'd like to do some Pistal HC pistons soon on the Hyper. I have not been able to find anyone local that does porting. I do not want to spend $3k on red heads.

Am I OK doing 11:1 or 11:5:1 pistals running pump gas without porting the heads?

Will I still see a 10% gain in TQ and HP?

Thanks

[08hyper]

Originally Posted by parkcrf

I'd like to do some Pistal HC pistons soon on the Hyper. I have not been able to find anyone local that does porting. I do not want to spend $3k on red heads.

Am I OK doing 11:1 or 11:5:1 pistals running pump gas without porting the heads?

Will I still see a 10% gain in TQ and HP?

Thanks

Ported heads will make a difference, how much of a difference depends on who did the port job, and will work GREAT with the HC pistons.

I'm using the 100mm Pistal pistons (1123cc) at 11:1 and they work great.

When you get your heads off look at the factory porting, then you'll understand. Aloha Alex

[Shazaam]

No, you don't NEED to port. Raising the compression ratio doesn't increase the amount of air (and fuel) entering and leaving the engine so modifying the ports and headers will have little beneficial effect when you move to high compression pistons.

There are two basic ways to increase the power of an engine. One way is to increase the amount of fuel and air being burned and another is to increase the efficiency of the burn itself. Raising the compression ratio of an engine primarily increases combustion efficiency. An engine will run most efficiently when the fuel/air mixture can be compressed as much as possible. More heat, more compression and the fuel/oxygen reaction will happen more quickly and more efficiently.

The main reason that high compression engines aren't manufactured anymore for street bikes is higher exhaust emissions. The extra heat produces more oxides of nitrogen (NOx). From a design point-of-view it also decreases reliability as the engine is under greater strain. So to increase the compression ratio of an engine designed for lower internal forces may require changes beyond high compression pistons.

The additional compression also produces higher cranking loads and additional blow-by. The higher cylinder pressures bypasses the rings easier so more combustion gases get by the rings into the crankcase. So consider using the Corsa breather canister and plumbing instead of the stock setup. You need to assure that the intake properly scavenges the crankcase of the increased blow-by without sucking any oil into the intake tract.

Further, you'll need to run higher octane gas to assure reliable high compression without detonation. Gas octane availability above 92 in the US is limited to aviation and race fuels, so most modern engine designs designed for high octane gas use knock sensors and computers that adjust the ignition timing on a real-time basis, so that they can be run nearer the detonation point without being damaged.

However, chances are is that you'll be able to run a 13:1 compression ratio before exceeding the octane requirement of readily available pump gas.

Simply stated, when you raise the compression ratio you risk damaging your engine from pre-ignition. The resulting shock wave can shatter a four stroke piston. So, you first need to make sure that the ignition timing is set properly to prevent engine knock under a variety of load, fuel, and environmental conditions that affect engine knock.

There are two primary factors which govern engine ignition advance. First, the constant time to burn results in a need for a linear increase in advance as a function of RPM. Second, higher RPM and loads lead to higher turbulence and faster burn times. So, the ignition advance should initially increase with RPM and then taper off and even decrease as the engine speed increases further. As a function of load (manifold pressure for example) the timing should decrease, ultimately being limited by engine knock and exhaust temperature. Before computers and solid state ignitions came into general use, manifold vacuum hoses and centrifugal advance mechanisms on distributors were used to advance engine timing.

On Ducati superbikes the ignition system is integrated with the fuel injection system to form a combined integrated engine management system which is operated by the electronic control unit (ECU). The ECU uses inputs from various sensors to calculate the required ignition advance setting and ignition high-tension coil charging time. There is no factory provision for adjusting the ignition timing on these models.

On some models, replacing the stock chip with a FIM EPROM will allow the associated diagnostic software to download a modification to the computer's base ignition advance map. However, since there is no standard remap available from FIM for any generic or specific high compression piston modifications you'll need to locate a dyno tuner who is knowledgeable and experienced enough to create a custom map for you.

In recent years, ignition advancers have also been used to provide some adjust ability. I don't know if anyone has adapted one for Ducati use (check with K&N or FactoryPro). Ignition advancers basically change the timing of the motor so the mixture has a tiny bit more time to burn at high RPM. The trade-off is that you may not get a proper burn lower down in the RPM range because you're initiating the spark too early. So you'll very often experience a few horsepower loss in the midrange but few horsepower gain at peak RPM.

Racers have no troubles making this trade-off because they operate mainly in the high RPM range. Street riders using their seat-of-the-pants dyno also feel a difference because the motor is suddenly making more peak power, when in reality they are giving up midrange power in exchange for a much harder to use peak horsepower.

That's why a more reliable (and hence common) approach to increased power is to increase air flow (and fuel) volume into and outof an engine. Basically, engine power is air-limited (not fuel-limited). For maximum power, you need to ingest and burn efficiently as much air as possible. This is most easily accomplished by adding big-bore kits, high-lift camshafts, larger valves, larger throttle bodies, and free-flow exhaust systems.

That said, the high compression route is a very effective way to improve torque and horsepower throughout the RPM range.

[CrimsonCloak]

Ducshop does fine port work, as do several other shops on the forums.

[parkcrf]

Shazaam, thanks for the response, very well put!

Thanks to all for the responses - I may just drop in some 11:1 pistons and call it good.

Cheers

[1duckyboy]

Consider thermal barrier coatings on piston tops, combustion chambers, exhaust valves/ports. My experience is this can aid in stopping preignition and detonation, $200 well spent.

[singlefin]

awsome post shazaam!

[08hyper]

Nice post shazaam, and like you said, to get more power from a engine, you will need to get more airflow & fuel into and out if an engine, and a good port job is a very important part of that accomplishment, and thats why it works well with the HC pistons, just use your head and don't go crazy on the compression ratio, and make sure that the components you use work well together. Aloha Alex

[NYSport]

Originally Posted by parkcrf

Shazaam, thanks for the response, very well put!

Thanks to all for the responses - I may just drop in some 11:1 pistons and call it good.

Cheers

If you are going to replace pistons then you might want to have the porting done, you are half way there.

[mattcosta7]

from any efficiency level, if you are replacing pistons / rods, then you have the head off anyway. It makes no sense to pull the head off, and NOT get it done. Proper porting on Ducati heads alone makes very decent gains. When mixed with a HC piston kit, you'll be making alot more power throughout the range. I believe on the Hyper the reccomended street kit is either the 11 or pushing it the 11.5. Ducshop I believe will machine the heads to 11.25, which is the best blend of power/reliable pump compression. Any higher isn't great on the US octane levels.