Maximum RPM.

[imago]

Someone will have taken things to the limit (and beyond )

So my first question is, on a 16v roller bearing engine what's the maximum rpm you can got to repeatedly without it turning into an expensive grenade?

My second question is, what's needed to get there in terms of component changes/modifications to prevent disaster rather than making the RPM?

I'm looking to take it from the stock 9,000 to somewhere above 11,000 with 12,000 as an optimistic target. Assume welded crank, increased oil flow/pressure, Wiseco forged pistons, bigger valves (Kibblewhite with springs to suit), flowed/ported head and a free flowing exhaust (make TBD).

[Gixer1460]

Depends on use I guess? ie. Drag racing will probably hit 11-12k every run, maybe 4x and last a year or two? Prostock will see far higher rpm's but a new billet crank will be replaced after 15-16 passes! A race bike may not need that top end if gearing and torque allow taller gears to work, thus improving longevity. I'd guess the best people to ask are the Classic 24hr Endurance guys - they must balance power with longevity?

As its a roller bearing, excessive pressure and oil flow can actually be bad! Too much oil causes the bearings to 'skate' instead of roll and wear occurs. I'd say Suzuki knew what they were doing as used well these dinosaurs bottom ends can be bullet proof. Rotating mass is the enemy of rpm - with a cast crank, its easy to carve off weight but not so easy with a GSX? Everything else is std. higher rpm optimised for racing type mods - don't forget cams and maybe Ti spring caps - lighter so better valve float control. Pick Rupperton's brain - he's built enough to know what does and doesn't work!

[imago]

4 minutes ago, Gixer1460 said:

Depends on use I guess? ie. Drag racing will probably hit 11-12k every run, maybe 4x and last a year or two? Prostock will see far higher rpm's but a new billet crank will be replaced after 15-16 passes! A race bike may not need that top end if gearing and torque allow taller gears to work, thus improving longevity. I'd guess the best people to ask are the Classic 24hr Endurance guys - they must balance power with longevity?

As its a roller bearing, excessive pressure and oil flow can actually be bad! Too much oil causes the bearings to 'skate' instead of roll and wear occurs. I'd say Suzuki knew what they were doing as used well these dinosaurs bottom ends can be bullet proof. Rotating mass is the enemy of rpm - with a cast crank, its easy to carve off weight but not so easy with a GSX? Everything else is std. higher rpm optimised for racing type mods - don't forget cams and maybe Ti spring caps - lighter so better valve float control. Pick Rupperton's brain - he's built enough to know what does and doesn't work!

 Good shout on the endurance guys, never gave that a thought. I know just the man to ask as he built GSX endurance engines for a team using them in Harris frames. I can carve a bit of weight out of the crank and flywheel, but not much. As you say it's neither easy nor wise on these and the crank's always going to be the limiting factor.

The spring kit comes with titanium caps and spring seats. I can't decide on cams, but I don't need to just yet so I'll worry about that a bit down the line. 

[imago]

From the horse's mouth. So just a touch off where I want to be but perfectly adequate basically.  Why on earth I didn't think to ask him in the first place I don't know. Age probably. 

Quote

Hi it depended on the spec the stock cc motor would take 11k and would make power to the end of the graph no drop off but we would typically run the over size 10600 but at 10500 in the ignition box I would pull 20 degrees off to 10600 giving a very soft limit. Never had a engine fail you could run more but not sure rods your using and ptv and squish your running. With the carbs, cams pistons head work exhaust systems and setup the bigger motors would do around 160bhp at 10500.

 

[Slabbie11]

Valve train is generally the Achilles heel at high rpm for most engines unless there is a specific issue elsewhere (oiling, breathing, harmonics etc) Valve control becomes critical & as soon as you start to approach valve float the forces become massive which tends to break things very quickly. Bottom end wise just need to consider that forces increase with the square of speed so an extra 1000rpm can double the loading. Keeping mass to a minimum obviously helps this. Also need to think about why you’re planning to overrev? You’ll need enough airflow to be making power up there as otherwise it’s of little benefit unless it’s a specific scenario to get around a gearing issue? Roger is the guy to ask though.

 

Stew

[imago]

Breathing will be through Bandit 1250 36 mm throttle bodies with the secondary butterflies removed. Into ports opened up and the flow improved and exiting through 1 mm oversized valves. Valve bounce will be controlled by Kibblewhite double springs sitting on titanium seats with titanium caps.

Bottom end mass will be short skirt lightweight pistons, with a little shaving and smoothing of crank webs to lighten things up a touch there without getting silly. Perhaps also gaining a touch on resistance and a scallop out of the liner bottoms to ease some of the pumping resistance.

.9 squish, 1mm PTV on the inlet, 1.5mm on the exhaust on an 1168 overbore and we should be about where I want to be. 

[Slabbie11]

Going down in capacity rather than up would help your reciprocating mass (depending on the parts you use obv) & would also bring the airflow requirements down at a like for like RPM point…you’ll basically be making torque higher in the rpm band which multiples through into HP. Getting enough airflow (valves, ports, cam profile+lift+timing etc) to make it worthwhile is issue one & then making it all live is issue two! Either way Rog will be able to advise.
 

I did speak to him on a GS1000 engine he had on his bench & can’t remember the numbers in terms of rpm but it was a screamer & made very healthy numbers bearing in mind it was a 2V head & “down” on capacity compared with the vast majority of overbored 1100s! Like everything it’s a different compromise based upon rules in that case.

 

Stew.

[imago]

21 minutes ago, Slabbie11 said:

Going down in capacity rather than up would help your reciprocating mass (depending on the parts you use obv) & would also bring the airflow requirements down at a like for like RPM point…you’ll basically be making torque higher in the rpm band which multiples through into HP. Getting enough airflow (valves, ports, cam profile+lift+timing etc) to make it worthwhile is issue one & then making it all live is issue two! Either way Rog will be able to advise.
 

I did speak to him on a GS1000 engine he had on his bench & can’t remember the numbers in terms of rpm but it was a screamer & made very healthy numbers bearing in mind it was a 2V head & “down” on capacity compared with the vast majority of overbored 1100s! Like everything it’s a different compromise based upon rules in that case.

 

Stew.

I can go up 100cc in capacity, add 1500 rpm and end up around the 160 hp mark. What's not to like?

Roger Upperton has earned his reputation, but it's worth bearing in mind that he's not the only engine builder with experience of air cooled Suzuki engines. The approach and requirements for getting the most from a NA engine are the same no matter who's doing the work. I posted the question to see if anyone had found the upper limit for the 16v GSX in particular. @Gixer1460's post reminded that I already knew a man who could answer the question, and the answer is 11k, and then come down a touch to allow for the maximum output on an over bored engine.

[Gixer1460]

Glad to provide the memory jog - useful having contacts in obscure series!

[imago]

25 minutes ago, Gixer1460 said:

Glad to provide the memory jog - useful having contacts in obscure series!

I just never made the connection TBH which is made worse by the fact that he supplied the pistons and it's his dyno it'll be going on when it's built. 

In my defence he's all about the modern short circuit race engine building now so it was perfectly reasonable to forget. That's my defence and I'm sticking to it! 

[Arttu]

As said already here I think it highly depends on what kind lifetime you want out of it. Pro Stock engines run up to 14000 and they are 1700cc long stroke builds. But lifetime of a crank is only some tens of quarter mile runs.

I think your conclusion of 10.5-11k limit is pretty sensible if you want to keep it going any longer. And I also think that you will need quite serious work with head, cams and intake to keep power up that high any ways.

[imago]

1 hour ago, Arttu said:

I think your conclusion of 10.5-11k limit is pretty sensible if you want to keep it going any longer. And I also think that you will need quite serious work with head, cams and intake to keep power up that high any ways.

That's the plan, but we all know how they go. 

The main thing still TBD are cam profiles but I have a source for info on those, just waiting for him to get back to me. Other than that the set up before the bodies will need working out and no doubt a bit of experimenting/tweaking on the dyno.

[coombehouse]

I seem to remember that Phase One endurance had issues with crankcases cracking when they used this motor at prolonged high revs. Don't think they resolved the issue as rule changes allowed oil cooled motors so they moved on. Not 100% on the details though 

[Reinhoud]

I hear noone about the conrods... The real challenge...

 

No idea what they can handle, I'm actually also curious what the air cooled engines can take, I'm not brave enough to try it, I already had a snapped con rod in the past.

[Gixer1460]

1 hour ago, Reinhoud said:

I hear noone about the conrods... The real challenge...

No idea what they can handle, I'm actually also curious what the air cooled engines can take, I'm not brave enough to try it, I already had a snapped con rod in the past.

The '493' Katana rod is a proven high horsepower rod even if re-bushed for 20mm pins. If the application demands hours and hours of flat out running then all components are 'generally hours limited' so get replaced on cyclical basis! In my opinion its the acceleration / deceleration cycles that do the most damage, just like Nitrous is hard on pistons and rods but a turbo (hp - hp) is soft on them. I guess only by destructive testing or use, do you find definitive answers!

[Duckndive]

2 hours ago, Reinhoud said:

I hear noone about the conrods... The real challenge...

No idea what they can handle, I'm actually also curious what the air cooled engines can take, I'm not brave enough to try it, I already had a snapped con rod in the past.

As Ian said katana "493" is a well proven rod 

Rickards Funny bike went sub 6.4 over 200 mph regularly 

IMO Tune up has killed more rods than outright HP  

[imago]

5 hours ago, Reinhoud said:

I hear noone about the conrods... The real challenge...

 

No idea what they can handle, I'm actually also curious what the air cooled engines can take, I'm not brave enough to try it, I already had a snapped con rod in the past.

It's a whole package thing really, so if timing isn't advanced too far, mixture isn't too lean and oil flow is at a reasonable rate then the heat generated is at an acceptable level. Compression ratio needs to remain at or below 10:1 and piston weight is reduced from standard. That lot will then mitigate the moderate (10/12%) increase in RPM.

You also need to be starting from a good base with the components, make sure that oil ways are clear, cases and fins tidy and not under 12 layers of paint.

Upping the output from these old air cooled motors is perfectly possible, but it's an expensive time consuming process with an exponential increase in both as you climb the HP ladder. Some of the prices for special cases and cranks @Duckndiveposted for the top end of the output stuff they use in drag racing were frankly terrifying.

[Reinhoud]

Do we know that TS has 493 rods?

 

Raising the pressure is almost impossible with the roller bearing cranks, tried that multiple times, pressure goes up when the engine is cold, drops to just as low as when stock.

A restrictor in the feed line to the gearbox works slightly, a wider pump might work, in case your bike has the narrow (10mm) pump.

I'm not familiar which models have the wider (14mm) pump.

I made an wider oil pump, even that didn't raise the pressure..

[imago]

 

45 minutes ago, Reinhoud said:

Do we know that TS has 493 rods?

 

Raising the pressure is almost impossible with the roller bearing cranks, tried that multiple times, pressure goes up when the engine is cold, drops to just as low as when stock.

A restrictor in the feed line to the gearbox works slightly, a wider pump might work, in case your bike has the narrow (10mm) pump.

I'm not familiar which models have the wider (14mm) pump.

I made an wider oil pump, even that didn't raise the pressure..

With a roller bearing crank in an air cooled engine flow/volume is more important than pressure although they are a function of each other in pumping terms. So fitting 750 gears helps, but I got a set with a higher ration than 750 gears from @clairetoowhich takes it up again.

Edited October 29 by imago

[Reinhoud]

I know..

[imago]

12 minutes ago, Reinhoud said:

I know..

Might have been a good idea to mention volume instead of talking about pressure then?

[Gixer1460]

GS1000 / 1100 / 1150 cranks and rods can pretty much survive with std. oil flow / pressure as it amounts to virtual drip / splash lubrication. So increased pressure / flow only benefits the cams which is no bad thing - the increased oil also offers a degree of additional cooling - Suzuki didn't come up with the GSXR SACS system on a whim! Gearbox doesn't need an oil feed but the clutch does so unless you are drag racing when clutch gets reset every pass, its best not to restrict oil to gearbox long term!

[Reinhoud]

On 10/29/2024 at 7:10 PM, imago said:

Might have been a good idea to mention volume instead of talking about pressure then?

Read your first post back, you mention pressure

Edited October 31 by Reinhoud

[clairetoo]

I run my current old-school stocker motor to a max of 11500 , shifting at 11000 - back in the 90's I ran a star racing motor to 13000.....only crank fail I had on that motor was a cracked weld had the left end web separate and wobble a bit.....  I keep the revs lower for longer engine life , less top end maintenance , and big heavy pistons (current crank is 5 seasons old !)

I also run mild cams (G4 Cammotions) , oil resticters under the cam bearings to push more oil flow out to the rockers , thats the area that poor oil flow will damage first , also my high-ratio oil pump gears (but I also run 750 primary gears) 

But one important thing to bear in mind - my motor is only flat out and under load for 8.5 seconds at a time , so drag race motors can be a little more `fragile' , whreas a road race motor is gonna be thrashed for half an hour or more......