High RPM 4 stroke ideas

[tfaith08]

I've been into racing for a very long time. Out of that time, I've found that no matter the application, 2-stroke, 4-stroke, or rotary, N/A or FI, or any other platform, high RPM engines are the best sounding and most fun to build. Anyone can throw a V8 together and make power by parts selection, but making anything stay together at extreme RPM is another thing entirely. 2-strokes can be made to rev as well as rotary engines, but we're already in the 2-stroke mindset and not that many people have ideas on rotary engines. As a result, I'd like to encourage some intellectual conversation on building the 4-stroke breed.

So the point of this thread is this: what ideas or theories do any of you have for building a 4 stroke screamer? I've got my ideas, but I don't want to take the floor first.

I'd like to ask that everyone refrain from posting things like "upgrade the valvetrain and balance it" unless you have some insight that should be shared.

 

[Herpderplol]

Are you mainly asking what we think makes a high revving 4 stroke?

Or what to do with a 4 stroke to push power and maintain the quality/no maintenence part of 4 stroke engines

 

[rich1]

I'd like to ask that everyone refrain from posting things like "upgrade the valvetrain and balance it" unless you have some insight that should be shared.[/QUOTE]
Not sure what you mean?
Kinda hard to ignore the 2 most important factors that enable a 4 stroke to even obtain high RPM...
Lightweight components and using gears instead of cam chains ....RC 30 Honda
Balance shafts / dynamic / static balancing so the parts can live... Blaster and Banshee
Using the smallest bore motor you can to get the job done...Hondas 60s roadracers

 

[motoman159]

Are you talking about a single cylinder quad 4 stroke? 4 cylinder? V8? Turbo 2jz on 30psi? I've always wanted a 283 small block with 2 small turbos. I would spin most of my time balancing and balancing again. The reason for the 283 (GM style)
Is that they've got a really thick sidewall inbetween cylinders and iron block. Also they're not that big of a motor so you can rev one higher safely. Add the turbos and you've got a high reving nice sounding v8 that wouldn't get that bad Gas milage with efi due to the low compression that you run with turbos. It would also spool the turbos quickly in theory if you kept them small and had a motor that was pretty ballsy before boost. Sorry if I got off topic just dreaming over here.

 

[tfaith08]

Mainly what it takes to take an average 4-stroke and make it reliably rev high and produce power.

 

[motoman159]

Mainly what it takes to take an average 4-stroke and make it reliably rev high and produce power.

Well you need a good head design for one thing. That's very very important.

 

[tfaith08]

Not sure what you mean?
Kinda hard to ignore the 2 most important factors that enable a 4 stroke to even obtain high RPM...
Lightweight components and using gears instead of cam chains ....RC 30 Honda
Balance shafts / dynamic / static balancing so the parts can live... Blaster and Banshee
Using the smallest bore motor you can to get the job done...Hondas 60s roadracers

I'm targeting the generalization. Stating that all that has to be done is upgrade valvetrain and lighten the rotating assembly basically covers the topic if you generalize it. Rather, stating that certain ratios on rocker arms can add power due to higher lift but can wear the components quicker would be a better contribution. Stating things like having oil shedding coatings applied to the bottoms of the pistons AND WHY would be an even better contribution.

 

[tfaith08]

As for an application, let's go with a Ford 351W. Those are covered on every corner of the internet, but the topics exist in either parts listings or are plagued by people asking why the OP wanted to build a high revving engine.

EDIT: Hell, any application will work. I just want to spread info and learn. I know what I like to do to them, but I want to know more lol

 

[rich1]

Are you talking about a single cylinder quad 4 stroke? 4 cylinder? V8? Turbo 2jz on 30psi? I've always wanted a 283 small block with 2 small turbos. I would spin most of my time balancing and balancing again. The reason for the 283 (GM style)
Is that they've got a really thick sidewall inbetween cylinders and iron block. Also they're not that big of a motor so you can rev one higher safely. Add the turbos and you've got a high reving nice sounding v8 that wouldn't get that bad Gas milage with efi due to the low compression that you run with turbos. It would also spool the turbos quickly in theory if you kept them small and had a motor that was pretty ballsy before boost. Sorry if I got off topic just dreaming over here.

I own a 04 Mach 1 Mustang 32 valve V-8 281 CI...it revs to 7 grand but is a little weak on bottom like all double overhead cam motors are. When I need to go faster at any speed that's what the 125 hp shot of Nitrous is for !

 

[bansheedave]

my biggest issue with high revving 4 strokes is controlling valve float. for high revs, I would stay away from big bores and long rods. stick to stock length rod and piston. upgrade for reliability. may run a tall dome piston to increase compression. race gas only. I wouldn't get a higher lift cam, but get one ground for more duration. to help in the scavenging. port and polish as much as possible. chamfer the piston skirt to increase oil lubricity between the piston skirt and cylinder. also helps in reducing piston rock. port match the exhaust and intake. run stiffer springs to control valve float and upgrade valves. if possible, a 3 angle valve job. maybe even install larger valves to increase intake charge and exhaust exit rate. but that's my ideas.

 

[Blaaster]

Higher revving 4 strokes will benefit from this valve train design.

The valves are closed mechanically which alleviates valve bounce.

 

[rich1]

Teflon coated piston to reduce drag, windage tray to reduce oil turbulence. Crankshaft scraper to keep oil on crank to min. Alum block and heads to keep weight and heat down. Small

Higher revving 4 strokes will benefit from this valve train design.

The valves are closed mechanically which alleviates valve bounce.

View attachment 10715

Blaaster........Ducati is going to send the Mafia to get their picture back.

 

[rich1]

As for an application, let's go with a Ford 351W. Those are covered on every corner of the internet, but the topics exist in either parts listings or are plagued by people asking why the OP wanted to build a high revving engine.

EDIT: Hell, any application will work. I just want to spread info and learn. I know what I like to do to them, but I want to know more lol

Poor choice....The FORD 351 was a truck motor, it was never designed to rev !That was what the 302 was for.LOL !
Thats why the Ford Mod motors were made using 2 or more of the following... 281 - 302 ci.. Double overhead cam , variable valve timing , Teflon coated pistons, forged crank , forged rods, forged pistons, 3 or 4 small valves , straight port heads, 4 bolt mains , Alum block, oil lines directing oil to the bottom of the pistons
.Most important of all, a near square motor @ 90.2 x 90.0... lets it rev like crazy.

 

[tfaith08]

I picked that because no one picked and they used that platform until a few years ago in NASCAR up to nearly 11000rpm. I agree to go with a smaller engine like the 302 or 289.

As for the square bore, I've always been a fan of oversquare. The stroke seems very large to be able to rev reliably. Of course, they do, but imagine a 302 that has been de-stroked to around 60mm. 9000rpm power peak, 9800rpm shift target, anyone?

Larger stroke = higher mean piston speed, increased pumping losses, increased wear, and greater stress on the components. The upside is that reversion is rarely an issue. I would mention that a higher lift cam can be used, but that's almost a requirement to maintain the powerband.

Also with a larger stroke, you have to consider the ability of the head, valves, and cams to purge and fill the cylinder. There is quite a bit of mixture contamination that goes on with a large stroke engine. On the other hand, there is often quite a bit of mixture lost with a short stroke 4T.

Now with a large bore, short stroke, much larger valves can be used reliably (key word is reliably). Higher duration cams can be used with less taper and less lift requirement, ultimately making valve float much less prevalent. The decrease in lift requirements also reduces the chances of interference with large valve, high lift applications.

DOHC is something that I highly agree with. Unfortunately, desmodromic valvetrain is not something that I have first hand experience with. I did draw up a design for a variable timing desmodromic valvetrain and do a poor-mans patten on it .

 

[Larry's Shee]

MONEY !!​

2013 F-1 engine, 2014 suck ballz because they are V6. I don't even watch F1 because the engines don't scream like they used to, they sounded like a 2s.

The have/had interesting tech tho, selenoid opperated valves, totally variable timing, maybe lift?

 

[motoman159]

Look up the h1 v8. It's 2 Suzuki 1300 motors that share a block. It revs to 11,400rpm, n
Makes 450hp naturally aspirated and it's 2.8l That weights like 275 pounds fully dressed. Thats, a good motor.

 

[tfaith08]

Renault played with the electro-hydraulic valvetrain idea in the 80s or 90s I believe, but they abandoned it. That would have made some extreme power. As Larry stated, infinitely variable timing, lift, duration, etc.

The pneumatic valvetrain is something that I started looking at to try on a small 4T, but it requires a bit more than I planned on so I abandoned the idea before putting anything into it. It is cool that Toyota engines were claiming 19700rpm with the V10s that were used before the V8 swaps, but several sources suggest upwards of 22000rpm. Take a look a this Cosworth V8:

Then this Toyota V10:

On another note, I did look at a Kawasaki Ninja 1000 engine and found that they have no oiling jackets or passages on the center crank bearing. Nothing at all. There is a recall, but they still send parts out for the old design when ordered. When I say nothing, I mean that whatever is there when it is installed is what is there until it comes back apart. We almost called Kawasaki about it, but even the manual shows the same pictures, so we said screw it.

 

[HACK]

I know that the Yamaha Fzr 250 will redline around 19000rpm. I don't know if that helps. But it might be interesting to look and see how they get them to run as they do