Some usefull information on high compression

[chris steedman]

I thought about starting this thread based on a question that popped up on another thread earlier today.

The Pistol racing R2000 or Omega from the older 996rs (both being near identical) With approx 14.1 compression ratio dropped into standard 996 heads. Dont confuse them with the newer Omega or Pistol 1999 with deep and wide valve pockets cut for 39mm inlet valves . Those give about 12.5.1-13.1 max in stock heads depending on squish.

Using this very high compression R2000 piston as a drop in (no squish adjustment) and leaving the cams as the factory intended using 98 octane fuel, will give no problems and a very good HP boost.

Problems happen when these pistons are used with 1mm squish plus running inlet valve closing at under 60 degrees on uk spec 98 octane fuel.

This number will vary as do the quality of fuels country to country.

A few years back nearly 4 , our race bike had these installed with an inlet valve closing of 58 degrees 108/108. It returned the following year for a refresh with sand blasted pistons and parts missing near the top ring. They were replaced , but this time underload on the dyno we herd the rattle (tinkling sound) .The cams were backed off near stock specs\ remapped and half way through the season i popped the heads off for valve maintainance and the pistons were still as new.

Since then when i use R2000 pistons or the Omega versions i go no further than 67 degrees inlet closing for biposto and sps cams . If using 748R or 748RS cams retard the inlet cams from there standard closing specs of approx 60 degrees to nearer 67 . This also gives slightly more inlet piston to valve clearance meaning you can run the 748r cams without milling the piston pockets

Since then all 996 bikes that return year after year for freshen -ups still have perfect pistons

As a side note the 996 rs bikes over here (wich use the same piston and smaller chambers with nearer 14.5.1 -15.1 compression) all run fine on uk 98 fuel too. They also have approximate inlet valve closings of between 68-72 degrees. They also have large radiators wich must also help. Having had quite a bunch of 996rs engines apart i never seen one suffering from detonation or melting . Therefore i say good quality cooling , good ignition and not to much cam advance is the key

I dont confess to being an expert and there is so much more i dont know about so feel free to chime in everyone (especially Bruce M /Mark who has had many years experience with these pistons. This is just what i found works for myself , and everyone else i build engines for year in year out with reliability wich is what we all want

+1 for Pistol R2000

[G8RDuc]

So where does one find the R2000 or Omega pistons?

[chris steedman]

Originally Posted by G8RDuc

So where does one find the R2000 or Omega pistons?

You can buy from Ducshop / bruce meyers / jhp england / and from ducati for the omegas at double the price of the pistols. Omega wont sell you the piston as ducati have there patent on it but they will provide one the same but with some minor differences for about the same price as the pistols.

[Ducshop]

one set in stock at the moment.

View Product

The photo is actually of the deep pocket 1999 13:1 but this is the R2000 PN, yes only advance the cams with stock pistons or the 1999 RS Pistals.

[neno]

I'm just curious what the differences are between the different set-ups.

Whats the difference between going with the R2000 pistons with a stockish cam timing, compared to a R1999 with advanced timing. Considering same cams and same valves for each set up. They must have some distinct characteristics, just wondering what they are, or if they are significant enough to consider.

Another quick question, it may have already been answered, how deep are the valve pockets on both styles pistals compared to stock pistons?

[chris steedman]

Depending on cam and situation this is how it generally works .

With a 1999 piston you could advance say 13 degrees, get a good midrange and top end.

With a 2000 you could run stock cam settings and have equal midrange to the 1999 with advanced cams but with a better top end.

Optimal cam timing depends on a whole bunch of stuff .

Performance comes from finding sweet spots that work together - Static vs dynamic compression (some call it cranking or working cylinderpressure) its just one of those variables

So lets say a Pistol 1999 piston has a static ratio of 13.1 , but the total dynamic working compression ratio is say for arguments sake 15.1 including its advanced cams. The Pistol 2000 will have that similar estimated dynamic compression ratio on stock timing because the static compression ratio is much higher from the start.

An example

Have you ever seen the boy at the end of the road drop a hot cam , with a later inlet valve closing point into his astra and loose all his bottom and mid range power.

This is because his hot cam has given his engine less dynamic compression due to the later INL VC point . Untill he raises his static compression to compensate for the loss in dynamic pressure his engine will be a turd. His other option would be to advance his hot cam untill it closes at the same point as the stock one he removed , but there will be a limit to this and maybe a top end power loss

This was generally the case when installing a G inlet cam without bumping up the static compression .

There is much more that can be thrown in to this but this is it in its most basic form

[neno]

Thanks for the info Chris. You confirmed what I figured would happen. I was thinking that they would have very similar midrange, but just wasn't sure about the top, and if there was a notable difference.

[vij]

Originally Posted by chris steedman

Using this very high compression R2000 piston as a drop in (no squish adjustment) and leaving the cams as the factory intended using 98 octane fuel, will give no problems and a very good HP boost.

Problems happen when these pistons are used with 1mm squish plus running inlet valve closing at under 60 degrees on uk spec 98 octane fuel.

You are talking about running SPS cams now? So if I understand correct running 1,3mm squish and 119,5/107 timing will normally work out good. Maybe even 113/107 as closing of inlet will be 67 degrees.

Originally Posted by chris steedman

Since then when i use R2000 pistons or the Omega versions i go no further than 67 degrees inlet closing for biposto and sps cams . If using 748R or 748RS cams retard the inlet cams from there standard closing specs of approx 60 degrees to nearer 67 . This also gives slightly more inlet piston to valve clearance meaning you can run the 748r cams without milling the piston pockets

When I adjusted the timing and checked the P/V clearance on my SPS cammed (107/107) S4R with squish at about 0,95mm. I got the smallest P/V clearance to be 1,65mm (10 degrees after TDC). If I think logic running 748RS cams would workout like this.

This is ofcours assuming that the pistal 2000 pistons has exactly the same valve pockets as stock pistons and the cams have the same profile.

SPS timed 107 opens 26 degrees before TDC (P/V clearance 1,65mm stock pistons)
748RS timed 111 opens 25 degress before TDC and closes at 67

adding 0,3mm squish would give almost 2mm P/V clearance and still keep the closing at 67 degrees and all will be good.

Sounds like it is all system go with 748RS cams and pistal 2000 pistons.

What performance gains would you estimate using 748RS cams instead of ss cams on 996 with Pistal 2000 pistons and heads done by you?

I am thinking that it might be going a bit to far to use both 2000 pistons and 748RS cams as I think that my 45/50 "spagetti" exhaust will not be able to handle all the new power


Jocke..........

[chris steedman]

Originally Posted by vij

You are talking about running SPS cams now? So if I understand correct running 1,3mm squish and 119,5/107 timing will normally work out good. Maybe even 113/107 as closing of inlet will be 67 degrees.




When I adjusted the timing and checked the P/V clearance on my SPS cammed (107/107) S4R with squish at about 0,95mm. I got the smallest P/V clearance to be 1,65mm (10 degrees after TDC). If I think logic running 748RS cams would workout like this.

This is ofcours assuming that the pistal 2000 pistons has exactly the same valve pockets as stock pistons and the cams have the same profile.

SPS timed 107 opens 26 degrees before TDC (P/V clearance 1,65mm stock pistons)
748RS timed 111 opens 25 degress before TDC and closes at 67

adding 0,3mm squish would give almost 2mm P/V clearance and still keep the closing at 67 degrees and all will be good.

Sounds like it is all system go with 748RS cams and pistal 2000 pistons.

What performance gains would you estimate using 748RS cams instead of ss cams on 996 with Pistal 2000 pistons and heads done by you?

I am thinking that it might be going a bit to far to use both 2000 pistons and 748RS cams as I think that my 45/50 "spagetti" exhaust will not be able to handle all the new power


Jocke..........

That all sounds about right and the R2000 does have stock depth pockets.

The 748R and 748RS cams yeilds about an extra 5+ hp from about 8000 up with no loss at the bottom plus the bike will hold its power for longer if you choose to extend the rev limit. It all really depends on the final spec too (pipes , throttles ect) . As you know its about finding a combination that works.

[amullo]

So what would be the better option for an otherwise stock SPS engine with adjustable camtiming wheels?

Would a porting, larger valves and a 0.6 shaving be a better option for a non-racer trackday and road bike?

Just looking to get the most out of the engine without decreasing longevity.

//amullo

[vij]

Originally Posted by amullo

Just looking to get the most out of the engine without decreasing longevity.

//amullo

Proper tuning will not decrease the reliability on an engine. What does reduce the life is bad setup, bad balancing, high revs and so on.

Proper / professionel tuning (including balancing) will extend the life of your engine. A properly tuned engine in a road bike lives a better and easier life then a "stock untuned" engine as it will give the same power at lower RPM, vibrate less, run with proper ignition advance and have a A/F ratio that is good for the engine.

Jocke...........

[neno]

+1 for proper tuning.

Even if a engine is built. High compression pistons, aggressive cams... etc. if everything is setup, balanced and tuned properly, it really shouldn't decrease the reliability or longevity of the engine.

This has been gone over before, but the single most destructive thing in a desmo engine is revs/high rpm. Try to make power lower and your engine will love you for it.

As for power in sps, I believe that Chris and others have proven there is a lot to gain by setting cam timing and shaving heads, valves, porting... etc. None of this should decrease reliability. I think this is a good choice, if pistons are not in the mix.

[amullo]

Ofcourse.. I was thinking about value for money.. Aswell as extra stress put on bearings and such.

//amullo

[vij]

Originally Posted by amullo

Ofcourse.. I was thinking about value for money.. Aswell as extra stress put on bearings and such.

//amullo

Ahhh I see.

Well I have not tried Crist (CJS) heads yet so I can not say anything about the performance but if you compare with MBP the CJS heads are very well spent money. I payed 3300 Dollars ( 2300 pound) for a porting and bigger valves at MBP. It also took 7 months and the valves were 1mm smaller then promised.

Based on that CJS is almost for free.

For the extra stress. That depends on your right hand and how much you twist it .

Jocke..........

[TomTom]

Wow, crist works with heads, I had no clue
He answers suspiciosly fast for being son of god.
The heads go like the devil may be another problem with this illusion...

[neno]

Originally Posted by amullo

Ofcourse.. I was thinking about value for money.. Aswell as extra stress put on bearings and such.

//amullo

Hey Amullo,

Before I start I was just curious if you had a 996sps or a 916sps. And if it is a 916sps, thats just basically a stock 996 right?

So I just wanted to point out a little something on the stress issue. Any time you increase the power of the motor, you also increase the stress on the "bearings and such", no matter how this power is made.

If you increase compression, which is almost always the most cost effective way to increase power, you will ultimately put more stress on the crank/bearings etc.

Many ways to increase comp. statically and dynamically, like Chris mentioned earlier, some include pistons, cams, cam timing, and porting.

As for the pistons I believe that pistals are actually lighter than the stock set up. So if you get these and get the crank assembly balanced, my guess is that you will actually have less stress on your bearings than you had with a stock set up.

So pick your poison. I would try to get my bike set up with good cam timing, shimmed head to 1mm, a good fuel map, these are pretty much free, and if you still are not satisfied there are many options.

As far as porting I believe that Chris is considered one of the top porting experts with this particular head.

[chris steedman]

Originally Posted by vij

Ahhh I see.

Well I have not tried Crist (CJS) heads yet so I can not say anything about the performance but if you compare with MBP the CJS heads are very well spent money. I payed 3300 Dollars ( 2300 pound) for a porting and bigger valves at MBP. It also took 7 months and the valves were 1mm smaller then promised.

Based on that CJS is almost for free.

For the extra stress. That depends on your right hand and how much you twist it .

Jocke..........

2300 pounds for a 37/31 conversion- no wonder im broke !

Prices went up today

[TomTom]

Neno, all you say is relevant.
Although Amullo has a 916sps which is 996cc and has T1cams that is 996sps cams, ti rods and the whole lot, so its a 996sps engine alright.
We did the cam timing and mapping on it and it turned out pretty decent (understatement) 916SPS Camtiming.

For sure I'd like to see one of those with Chris' touch to it, and get my tuning on it!

[moperfserv]

I took a glance at this thread and it took me back to the Harley forums.

The difference is that Tom figured it out.

First, the DesmoQuatro Strada cams as well as the 916SPS cams are assymetrical. They open faster than they close.
What this means is; The 'Lobe Center' that we use to define our cam position implys that the inlet cam peak lift occurs at 119.5 degrees ATDC.

In reality the peak lift is something like 8 degrees earlier. Functionally, from the peak lift standpoint, the 'Lobe Center' is 112 ATDC.

The 'G' inlet cam closes only a couple degrees later than the Strada cams and it's lobe center is 99 degrees ATDC.
What does that tell you about the 'Lobe Center' number?

It depends!
It also tells you that inlet closing is the more important dimension. Later inle closing supports higher RPM, earlier creates more pressure at lower RPM. Increasing cranking pressure, for one and increasing the pressure everywhere below the torque peak.

In the case of the 996, and I touched on this when I did a report on cam timing 8 years ago, the ports don't support enought airflow at the higher RPM to gain much at the power peak when you use stock 'Lobe Center numbers on the Strada cams. They will pick up the torque a little.

Here's where the Harley guys come in.

Almost all of their cams use the same lobe on the exhaust as on the inlet. Why? because they get their cams from the companies that make Chevy and Ford V-8 cams. Those guys found out that school-bus engines from the junk yards respond to an inlet lobe on the exhaust side, and it stuck as a concept.
Don't get me wrong, the Chevrolet V-8 is the most developed racing engine, ever, if for no other reason that it is so numerous. (In one of the GM engine plants with more than one production line, one of their lines produced 5,000 engines per day!)

But, I digress, the push-rod V-8 racing culture, generally leaves the cams alone and changes everything else to develop performance.

The Harley culture, accepts that the V-8 cams are what they need for undersquare, slow revving engines with higher exhaust-to-inlet flow ratios than the V-8s have, and they have found out that advancing the cams creates a little more torque at 2000 RPM. Keep in mind that they are also advancing the exhaust lobes (fixed lobe centers) and that looses low speed torque and helps high RPM vol eff.

What are the H-D concerns? detonation, detonation, detonation! What else does advancing the cams get them? The power heads for the ditch after the torque peak, so they create low torque, narrow power-band engines.

The reason I'm bringing this up in this context, is that I see all of the motorcycle brand cultures picking up the Car-Guy, Harley-Guy rap that torque is preferable to power. You get it in the car mags and the bike mags. Even the guys who actually understand the difference between the two, are compelled to explain it in a culturally compatible form, in other words, torque instead of power.

Power describes the work you can accomplish.

Torque is the force.

You can multiply the torque with gearing. You can't multiply the power.

Consider two bikes. One a 600cc which makes 100 HP @ 12,000 RPM in 5th gear at 120 MPH.
The other a 1200cc bike that makes 100HP @ 6000 RPM in 5th at 120 MPH.

If both of the rear tires have the same rolling circumference, they will both have the same torque at the rear axle at that 120 MPH.
Torque X RPM / 5252

Even thought the dynojet dyno tells you that the 600 makes 1/2 the torque of the H-D (@ the crank), the gearing is numerically twice the number, which multiplies the torque, which in this case is identical to that of the H-D at the rear wheel.

The performance is proportional to the power at the rear wheel! That will mean that the torque at the rear wheel is proportional to the power but it's the power that describes the capability for work.

When ever I hear about attempts to increase the torque at low RPMs I have to ask; why are you trying to increase the torque in a zone that will get you less power and performance for your work than it will at high RPM?

Years ago, I compared dyno charts of a 900SS and an 888 in 5th gear. The internal gearing is the same, the final drive gearing was the same and the 900SS was way faster up to 6000 RPM.

I'm not saying you should exchange your Ducati Superbike for a 2V Monster, but don't try to make it into one.

I drive my 944cc 851 in the same RPM range that you'd drive an M900 but I'm not racing and I'm rarely WOT.

Back to the H-D guys. They are always saying that you don't spend much time at your peak HP area, so why not try to develop all your power below 3000 RPM.

They forget that they also don't spend much time at WOT. At low RPM you are using part throttle, your maximum isn't being used!

Every lb-ft of torque you increase at 2626 RPM will get you 1/2 HP, at 5252 RPM that same lb-ft gets you 1 HP. Do the math, one lb-ft @ 5252 is worth two @ 2626.
You are wasting your time chasing lb-ft at 1/2 your peak RPM, when you are a couple down-shifts away from real performance.

You can't make power by ignoring torque, torque is part of the equation, but power defines the performance. Power-to-weight-ratio defines acceleration, power-vs-drag defines speed.

The 'torque gets you going and power keeps you going' quote comes from 19th century locomotives. Without gearing, that is true. Steam engines produce huge torque at very low RPMs, but trains don't use gear-boxes.
What did they replace the steam engine with? DC electric motors, which produce big torque off the bottom.

And then, on top of all this, you will gain much more practical performance by having your pile tuned!!!

If you don't have a custom calibration done for every change, you may not even be able to tell if all this cam timing is doing you any good at all.


The bottom line is; where does it say that your Ducati needs the same 'Lobe Center' numbers that a GSXR600 needs?

Doug

[chris steedman]

Sweet post Doug + 1