What is the most extreme valve lift you've seen on a Type 4 engine?

Thanks in advance.

Is .650" possible? Where there's a wallet there's a way.

But of the 1000's of T4 heads I've prepped for every conceivable combo, that much lift was never called for, so I have never done it.

I think Jakes most radical cam (off the shelf) was barely over .500

.565" is pushing it without custom parts and/or welding.

Yep, sorry my comment above is off.
I checked my notes and I was seeing .550 Lift, but decided that was too radical for my build and went with a much less aggressive cam.

Big question is why would you want that much lift?
There are limits to a pushrod T4 engine. To me the 914 isn't a dragster, it's a sports car.

If conventional proven T4 combos aren't enough HP for you then you should consider a different powerplant. There is what I call a "money wall", the point where a /6, subie or chevy would be a more cost efficient choice.

Thanks for all the replies and help.

The extreme lift with short overlap and long duration seems to be the way to achieve the desired 100 hp /liter with a smooth idle.

But I didn't know if I was pushing the design beyond its capabilities.

I know these questions must sound silly to those who are familiar with the Type 4.

But, I do not have any reference point... hence the question.

Hang on, I'll have additional stupid questions in the future.

I would suggest you might want to ask these questions from a different angle.

What is it you are trying to achieve?
What is the goal of the car?
What will you use if for?

These pieces of information might create more real world responses of motor combos that work.

Can you get 200 HP from a type 4....yes, but it has a limited application...mainly a race car...sucks to drive around town...

Bragging rights is one thing, but usefulness is where it will get the car out of the garage and driven....

As Mark said..there may be a point where you look at all the cool things going on with other motors in these cars.

rich

The hundred hp/liter topic has comes up many times over the years.

The best chance of building a streetable T4 with 100hhp/liter is going to come from a very small displacement engine with the smallest possible bore.

I have doubts that a streetable (streetable to my I-hate-a-narrowpowerband-on-the street old man self) 100hp/liter T4 is possible.

If it is then think really small displacement, like 1500cc's, max.

I have to warn the OP that if you pursue this goal, many custom parts and challenges await before you get to the tuning phase of achieving your goal. I don't beleive that it's possible with too many off the shelf parts.

And you better be a crackerjack tuner to squeeze the max out of your parts.

At what engine speed are you trying for 100 hp/L? In my relatively limited experience short overlap usual means you shy away from the exhaust scavenging gains you'd see at higher engine speeds.

Typically you don't gain very much flow-wise when your "valve shroud area" (I mean the effective outlet flow area-just drawing a blank on the correct term) is much larger than your valve/port area. Obviously, you need some room there for discharge losses, but just doing the simple calculation for a 42mm intake valve shows:

Valve area = 42^2*PI/4 = 1385 mm^2
Flow area @ 16.5mm lift = 42*PI*16.5 = 2177 mm^2

The 1.6x difference makes it seem like you have a ton of extra lift. Do the losses through the valve warrant that kind of lift?

I'm not attacking, just curious and asking questions. Engine modeling is awesome!

Thanks -

Its an experiment for my own bone stock 914 which I am using as a daily driver. Its not for bragging - I just want to see if it can be done.

I have always been fascinated with variations of the Miller cycle, particularly in taking it to extremes... I just want to see if it can be done by taking this philosophy to extremes. I don't know how else to do it.

If I blow it up, then I go back to stock or some variation. If I learn something, I will gladly pass it along.

Nobody I am in daily contact with really has any knowledge of the Type 4 engine. They all just say "throw an LS in it", which really isn't the point.

That being said, I'll be having some more absurdities to ask questions about.

Thanks again to everybody for your opinion, input, help, and patience.

I say come up with a plan you think will work and go for it. Even if you come up short you'll learn something.

I would suggest, though, that with regard to street cars way to much emphasis is placed on hp. Because hp is the result of the torque multiplier of rpm's, the very nature of max hp/liter builds implies revs that are not practical for street use.

Perhaps consider instead a torque/liter goal for your street car project. See how much of it you can get below 3000. You'll get the same mental excercise in chasing efficiency goals, with the added benefit that even if you fall short you'll end up with a fun street car.

Just a thought.

There is also a wall for HP per iron cylinder, that's why Porsche first tried biral then moved quickly to nikasil/alusil cylinders. I can't remember the exact number but 40hp per cylinder sounds about right.
Believe me when i say that if Porsche could have gotten away with iron cylinders all these years they would have.

Can you make 50hp per cylinder with iron?
Sure you can but it will be a short lived engine and a piss poor investment.


My T4 engine in my '67 bug is 180hp, but it cost close to $10k in parts.
The 3.0 /6 long block for my 914 was only a little more than that.

modern engines that are ohc have the advantages on lighter valve train and adjust valve timing events [profiles], and state of the art engine management.

these old tech engines have old school [crude] combustion chamber designs, heavy valve train and inefficient cam timing, and crude engine management.

i would think like Ham said above to get what you would "feel" most out of an engine would be to build a smaller bore stroked out engine the would keep intake velocities up and make a very broad and flat torque band.

As the old saying goes, the only thing that beats cubic inches is cubic dollars.

With that said, in the 80s I built a series of short lived engines that made some silly horse power. But I had access to a full machine shop my dad owned. I had no experience with Type 4s and made a lot of mistakes.

But I do admire the desire to see what can be done just for the experience. I wish I still had my notes but I am sure that I never got close to 100 hp per liter. The 40 seems to be pretty close. But even at that point I broke a lot of parts!

Simple to figure out, got CAD?

Easy enough to model out one cylinder and cam shaft section.

If new to that stuff, check out Fusion 360, it's free and you can do animation/motion to play with clearances and interference. Of course that is not at operating temp or deal with mechanical stretching of components.

IIRC, the Miller cycle is all about asymmetric expansion/compression ratios. Where you get more effective expansion than compression, something like that. And it is good for efficiency in terms of power output per fuel burned, but not so great for specific power.

...I hope I'm not mixing that up with a different cycle...

--DD

Dave,

You are absolutely correct. The trick is to reduce pumping losses at high velocities.

The breathing potential at all RPM is off the chart if the pumping losses can be managed. and, it appears it can be done.

So, now I am revising the model with a maximum valve lift of 0.550"

Thanks again to everybody.

Stay tuned - more absurd questions in the not to distant future.

With .550 lift you have to run dual springs, steel shims, CrMo retainers, hardened keepers, 1.7 rockers, spacers, 8mm rocker shaft studs, 911 adjusters and manton pushrods.

I have a Raby cam and lifters BNIB with .550 valve lift.

Also, if you are looking for a free CAD package, check out OnShape.com .
It is almost identical to SolidWorks as far as the interface goes.

And if you modeled something in onshape, I could easily import it into Solidworks and I have all the simulation capabilities.

For a flat faced poppet valve, that is with a 90 degree seat angle relative to the stem centerline, once the valve is lifted 1/4 of the throat diameter, there is no increase in opening area.
Valve throat area = Pi Dsquared/4
Area of the cylinder representing the lift area= Pi D H where H i the lift
Thus when Pi Dsquared/4=PiDH then when H=D/4 lift area equals throat area.

For a standard 2L head the intake throat diameter = 1.46". So once the valve lift exceeds .365, there is no further in crease in area. Remember to also subtract the area of the stem diameter for throat area for a more exact calculation. Also, since our valves are angled seats and not flat, the arithmetic is slightly different, but you get the picture.

In actual practice, there are dynamic effects of flow entering the combustion chamber that affect filling and combustion propagation that are dependent on the valve lift, so we cannot predict actual performance at lifts greater than .365".
That's for you guys that have developed cam profiles related to actual power produced

.585" is the most we've ever ran.