The stroker engine combos are well documented on these forums.I know Jake has quite a following here and the parrots will start repeating the gospel according to Jake.I have no doubt that Jake is the most trusted engine guru in the type 4 world and his combo's are envied by all.What I would like to do here is start a thread about the alternative to the stroker engine combo's.Many members here have built engines with the stock 66 mm and 71 mm cranks with good results.Those are the ones I would like to chime in on this thread.There are many 2056 inspired builds what I want to hear is actual results using large bore cylinders and pistons.Can these combo's produce reliable power for lower cost than a stroker motor and still attain some reliability.The 66x103 combo and the 71x103 combo would be quite common where as other more rare P&C sizes exist.Dyno results would be great.With the developments in new head combos and cam selection done by Jake and some others could a larger bore engine still benifit from these improvments and still retain the stock crank and rod configuration.I have 2 engines torn down to the bare case and would like to build something a little bigger than a 2056 and optimize it with a cam and larger P&C combo.I'm thinking about the 98mm birals from AA with JE pistons.My thoughts are it's not that far from a 2056 and if optimized with cam,heads and exhaust should produce 5-10 more lb /ft of tq and 5-10 more hp.Am I nuts to believe bigger can be better if optimized properly?The cost to go to 103mm is the same but I would suspect require more machine work.The 103's would require the heads to be bored out where as the 98mm slip into the stock 1.8,2.0 head bore and the case would have to be bored 1mm of thickness.Ok fire away.

well put questions

And well on it's way to being on page 3 with no responses.

There certainly are other ways to configure these engines.. The larger stroke and smaller bore have been my personal favorites for years due to longevity, cost, output, configuration and efficiency. Those are the reasons why I have based my program from these concepts.

Bigger bores are more dependent upon cylinder head prep and exhaust selections.

Can it be done? Absolutely. The reasons why I design engines in the manner that I do would take days to explain here on these forums and words just can't do it anyway. Out of all the configurations that I have experienced it has proven hard to beat a medium displacement, smaller bored stroker combination all around.

Maybe I'll do my January Radio Show on this topic, its been a while since the comparatives of design have been a hot topic.

66 103mm turbo on STF puts out 400HP (look for Wally)
71 103 Djet puts out 165 hp , yes it does...with the right cam and carbs it would put out more....
a stroked 103 displacing 2.6 liters is also quite doable...and fun, but I think its to much strain.

With any of the large bore cast iron cylinder, expect to tear it down and re-ring it every 10-15k.
I suspect if you went with the LN cylinders, you would not have to re-ring as often...its really a heat issue.

While stroking a motor does have benefits, using the stock rod ratio also has benefits...
The higher revving short stroked 66 with 103 is what I would suggest.
Yes, you need to machine the case and heads.
Go up to 46/38 mm valves and that seems to be the sweet spot, unless you are going turbo.

RIch

Yet again, look at the entire picture.. Not just output.

I build engines up to just under 3,100ccs and they do make a lot of power, with compromises.. Those compromises are generally what the TIV enthusiast is working to avoid, so it doesn't make much sense for engines like this to be designed. My N/A record is 280HP N/A on pump gas from a street engine of 2913cc.

That said, I have the experience with medium displacement engines of smaller bore, longer stroke as well as stock stroke (or even destroked) with a larger bore.

The comparative that comes to mind first was a 2320cc engine that uses a 71mm stroke coupled to a 102mm bore. To get the desired longevity that we demand from ANY engine I only use Genuine Nickies ™ to build engines with a bore larger than 96mm, so keep that in mind.

Fact is the 2320cc combo makes less torque down low than the 2270, even when coupled to the same camshaft, same heads and same exhaust system. The 2320cc engine didn't respond to larger heads, a different exhaust or altered intake enough to warrant the added expense.

The 2320cc engine cost 3K more to build than the 2270 that makes the same power, with even more torque. The engines ran the same CHT, but even with Nickies the oil temps were harder to control than the 2270, due to the 4" bore.

I worked to develop the 2320cc combo through 2001 and continued through 2004, trying to find the sweet spot for efficiency, but wasn't ever as happy with that big picture as with the 2270.. The MPG was less with the 2320, I NEVER got the 2320 to make more torque than the 2270 below 4K and the cylinder heads and case were weakened due to material removal for the larger bore.

But thats just me, but I have went with each design theory on multiple occasions.. I'd bet that no one else reading this board has done this, don e it back to back or purposely done the comparatives. I'll close this portion of my post by stating that the ONLY way I have been able to increase efficiency with bores larger than 100mm has been to twin plug the chambers, boost dynamic CR by reducing camshaft and by adding static CR, these things can only be done when adding two flame fronts to the combustion process.

That said, my experience clearly proves that any valve larger than 44mm on the intake can't be supported by an unwelded intake port. It also quantifies that any exhaust valve larger than 36mm requires more port metarial removal than can be supported without excessive work. Larger exhaust valves lead to over-pressurization of the port leading to excess crankcase pressure and other detrimental.

Is bigger better? Seldom.

My way isn't the only way, but I'd dare say that nothing is more proven~

Well, I'll take a chance and post my results. I just finished building a 2366 cc motor to replace my 1911. I AX mostly and thought that the shorter stroke would rev quicker and accelerate faster in 2nd gear (what AX is all about). The 1911 had about 112 ft-lbs at 4300rpm and about 104 hp at 5500 rpm at the rear wheels on a pessimistic dyno. A the time the engine was dynoed, the engine was suffering from a valve float issue and probably a pretty poor cam selection. The heads were done by Ham as part of the Raby "radio special" a few years back. They didn't have any porting done. I just threw it together quickly planning on building the 2nd engine in a couple years. Occasionally at an AX people would ask me if it was a "6". It was fun to answer that it was just a little 4.

I just finished testing the 2366 on the same dyno last week. It has about 145 ft-lbs and 150 hp at the rear wheels. It has amazing torque down low but doesn't seem to breath very well on the top end. My buddy recommended the cam and I was worried it was too aggressive. Now it looks like I didn't go far enough with the cam. Also, I'm running a set of headers and muffler set I bought at from Rich at HPH. The muffler is a reverse flow unit that may be giving me a little too much back pressure. We tested with Weber 44's and 48's with no real difference between the two. I've got about 1k miles on the engine right now and got about 26 mpg braking it in with 44's. I really like this engine. This is the 2nd build as the first time I assembled the engine it suffered from soft lifter syndrome. I guess it ws a good thing as it forced me to put another cam in. the first cam was very conservative. The SCAT (298* total duration) cam I'm running now is very streetable. I think that is where Raby has the advantage on us home builders. He knows his cams and what combinations work. I know I have a lot to learn, but am having a lot of fun building my own engines. I'm going to weld up a straight thru muffler and see if it improves the upper end performance.

OK, let the flaming begin.............

Its all trial and error.. one can use simulations, programs and previous experience all day long, but practical application is what teaches the lessons. I do all of the above, but never learn as much as when I throw some off the wall combo together to see how it responds, then start the comparatives to thousands of other dyno plots.

Trial and error can be a lot of fun, as borderline is experiencing right now, but nothing is more time consuming or expensive. I'd agree that the Scat cam he is running is probably a limitation, but its not creating as much of a misconfiguration as the exhaust system/ cylinder head combo more than likely.. Without using a header with a more defined collector and more optimum primaries and then coupling that to a cylinder head of 200CFM or greater that 2366 will never have the broad powerband that it is capable of.

Not seeing a difference between the 44 and 48mm carbs is what I'd expect. We START to use a 48mm carburetor on engines larger than 2,800ccs for a very good reason and Borderline just helped me reiterate that bigger isn't better.

The bigger is better crowd is always the easiest to beat.. Big cams, big carbs, big heads and big displacement is the most difficult combination to build efficiently. Smarter ALWAYS trumps bigger.

Great thread and discussion.

I have some core engines I am thinking of assembling, just for the learning
experience. I don't expect them to be great engines but I do expect I will
learn a lot by actually doing it.

What is the optimum configuration for a responsive, turbo type IV? I am thinking
of one that is drivable (less lag) and makes lots of torque, like a good AX engine?
Clearly, this is a loaded question and there is no best answer but is longer stroke
good for turbos, not good, its not that simple, etc?

John

Keep it small.. My best Turbo configuration thus far was 78X91, made 300 usable HP at 15 PSI, with over 300 lb/ft of torque.

.........With the 103 cylinders, In engines built by others, I have found that at least ONE head stud/at the crankcase/ aluminum material of the bored out crankcase spigot is cracked completely thru/into the crankcase...crankcase replacement is manditory...Even with engines with the 5th head stud does not alleviate this problem...there is just not enough "meat" to support the cylinder....I think that a 98 mm bore is about as far as the crankcase can handle with reliability...Increasing displacement thru stroking the crank makes sense.

Jake,
Since your favorite combo is a 2270 have you done any testing with a turbo on a 2270?

Yes, the 2270 combo doesn't favor boost due to cylinder wall thickness and sealing without using thick-wall Nickies made just for the application.
I only build boosted engines with Nickies, so that not an issue.

I've never seen a TIV cylinder register crack, even after boring them to 110mm OD to fit a 107mm bore size. that could be due to the fact that I only choose certain crankcases to build engines with bores that large from due to register strength.

Thanks for the great information.Jake can you help with a cam selection for a 98mm build?I will be using some heads that were built in 1983 by Competition Engineering and boxed up,never used.They are 1.7 castings ported and bored to 2.0 and 2.0 valves,8 to 1 compression.I would have the balancing done by You as well.I found a new set of VW Porsche mains in with the heads and other engine parts but the center main only has 1 half.The center main on the engine case I'm using has a wear pattern but I think It is within spec.Can I use the other 3 and let the center go if it measures good?

Think square.

I guess my question would be why build a big 4 when you could have a six? Or better yet a Boxster!

Yep, if my valvetrain kit is bought.. "The Cam Dr." selects every cam here and thats me, based on a questionnaire that the buyer fills out.. I MUST have that entire sheet filled out and you MUST know static CR and all other pertinent info before I can choose a cam. Cam selection comes last.

Wally on STF has built a nice 400hp monster from a 66mm crank and 103 mm cylinders.
It spins up fast and he has no turbo lag as a result.

Rich

I saw Wally's Autobahn run does he have a 901 trans in that Bug?

He went right to a G50, I think he blew up the first tranny on a 2.o liter turbo...
It was a wise choice.

He has dyno pulls and drag racing videos if you find him on youtube and look at all his videos...
Some of them are really amazing.

The intercooler is the key to what he is producing for HP....it provides alot of free HP from the same motor.
Harder to locate a decent setup on a 914, but maybe if you consider side scoops like the boxster you can setup a dual system.

The header he is using is available in the states from A1 I believe...but that is for a beetle configuration.
I spoke with Chris Foley and there does not appear to be a simple off the shelf Type4 turbo header to a mid engine setup, so you would need to make one.
Chris gave sound advise on this...short tubes, get to the turbo in as short a distance as possible to reduce lag...dont worry about 4-2-1 for a turbo.

Rich

To get back on track I'm more interested in N/A engines with the larger bore P&C combos see any interesting builds on the STF or other forums?

just wondering how this turned out? hows the engine doing?

I am also curious to hear here (as I know it has been addressed elsewhere) Nickies Vs Cast iron, can you make the cast Iron work? If it is just an issue of heat, and the expansion rates do not have a significant effect (uncoupled from heat obviously causing the expansion) can you set up a better cooling system (big front mounted oil cooler, better cooling fan set up etc.) and have it work as efficiently as the aluminum cylinders, or at least damn close? Also the issue of FI tune-ability vs the Carbs, wouldn't it be better to run a standalone ECU with an FI setup for tuning, rather then webers for the best power/reliability?

All questions I am in the process of answering, but would love to hear opinions before I dig in....

Bore vs stroke. Mark could probably explain this better than me. but here goes.
Over square motor design. = larger piston size as opposed to crank stroke. The less your crank stroke is the more likely you will be able squeeze more rpm out of that motor. which is sometimes an oportunity to make more power if you can flow at the higher rpm.

A stroked design will lose some top end rpm to maximum velocity. that piston can only move so fast.

From dynoing ducati bikes i noticed that strokers usually have great lower end torque. but usually tap out pretty quick as far as top ponies go. along with a lower rpm range.

Now the super bikes in ducati world have been going down a road of reducing stroke in their motors for the last 4 superbikes. for example the 1098 has a bore and stroke of 104x64.7 where as my 996 has a 98x 66. it may seem minute. but head differences aside the 1098 revs almost a 1000 rpm higher.

Bottom line From my observations the bore vs stroke relation can be one of the big critical things that will determine what kinda beast your building.

I remember working on a monster s4 916 that had a 1128 stroker motor in it and this bike was fast made like 30 more horse than stock, but the motor ended up losing around 1500 of rpm so it wouldn't break itself.

I guess the real question is what kinda motor do you want.. a high hp higher rpm screamer, like people built for formula v racing .... or do you want a big lazy torque monster that doesn't like to rev really high. depends on what your really building your car for. Well that my excessive two cents... and to mark I wish i could have bought into the type4 scene back 8 years ago with my baja bug. your dtm shroud is so damn cool looking.

There's is no perfect engine combo. I like FI and it can add mileage,etc., but it offers no more HP than carbs. A strong engine will be the sum of the parts and work you put into it.
As Porsche /6 engines got bigger and more HP they switched to aluminum cylinders and you know they didn't do it for the novelty of it. Coolers only work to a certain point.

A street and a track engine are two different animals, you have to be totally honest with yourself as to what the car will be doing all (most) of the time.
A 914 with a type 4 for the street I'd want a 6K/rpm torque monster and stroke gives you that.