Type IV Stroke and Rod Limits?

[SuperRSi@aol.com]

We are investigating building (probably by Oliver Knuf) for a customer, an engine with 103mm cylinders, IMPRO titanium connecting rods and wrist pins, and SCAT crank. What are the learned opinions on reasonable limits to crank stroke size and rod lengths? The engine will run Air Conditioning and a Z-Engineering Supercharger and be installed in a heavily modified 79 Convertible. No you cannot drive it...

Thanks,
Randy Moore

[JohnConnolly]

don't take this the wrong way, but if you are having Oliver build you an engine, why are you asking US what to build?

Nothing bothers me more than guys that get 18 different opinions from 20 different guys, and wastes everyone's time looking for the "perfect" combination (I get this on turbo questions all the time). There is more than one way to do something "right".

If you are thinking of having Oliver build it, then ask HIM what to build. Ask some other builder the same question and you will likely get a different answer. Good engine builders have some common themes, and these are musts, but beyond that, they are just different ways of achieving the same goal.

I like to run smaller rod ratios that lots of guys do on the street, and larger on the track. Street around 1.6-1.7 rod ratio, which pulls to 8500.

[vw@micron.net]

I agree with John. I've worked with Oliver for over a year on an engine combination and I'm very impressed with his knowledge. You won't go wrong setup.
Steven Arndt

[SuperRSi@aol.com]

It took you a lot of time to write how it wastes your time to respond to this type question. Next time, save time, don't respond. I am asking a legitimate question and seeking opinions. If Oliver gets the job of building the engine, I am sure his opinions will become very important to us. If he does not get the job, I would like to be educated and informed. It is difficult to communicate with Oliver in a timely manner, and I wanted more information. If the rest of you have any opinions, I am very interested.

[GDRBO]

If you check the archives there have been type 4s built in excess of 3 liters. I don't know the limits but the practical limit is your wallet. I must say large displacement, supercharger, convertable and air conditioning does make for an interesting and dificult combination.

[JohnConnolly]

I didn't want to be accused of "not being helpful". Oliver has a good enough reputation that he knows what he's doing. Engine builders don't like getting told what to do. So, what would you end up asking him? He has his ideas of what works, and what doesn't, are you going to debate with his views?

It takes YEARS of finding out what works, and what doesn't, and you can't do "your homework" on this in a couple weeks, or even a year, to come up to speed. Find a guy to build it and TRUST HIM. The alternative is to do the engine building yourself (a very useful option).

There is tons of engine information out there on engine theory, rod ratios, etc. Fact is, I believe much of the VW "knowledge" is bullshit, and based on heresay or opinion that has no factual basis (semi-hemi, for example).

I am not trying to be argumentative at all, please understand. Asking "engine theory" questions on a place like this is likely to get more wrong information than right, plain and simple (if you are dealing with high end stuff).

My opinion. You are fully entitled to your own. I'm also pretty sure this message will be taken in the worst possible way.

[Tom Notch]

The cam to rod clearance is the limiting factor on stroke, stay at 80 or under and life is a quite a bit simpler for the builder, who (or is it whom?) ever it will be. Superchargers build torque way low in the rpms, and take HP to operate All the time. T4s were designed to produce torque, being a short rod design stock. Don't need to go long on the rods for what ever stroke you end up with, 5.5 is plenty long in a T4, I'd stay at 5.325. What is the upper rpm you want the thing to run to?

AC, hmmmmmm, in a 'vert, interesting. I'd go with a late model R 134 friendly compressor. There are ones that take minimal space and Hp, and maybe it will fit in with the fan housing conversion that you will have to use. And fitting a puffer in it. Does the customer want the deck lid to close? What are your ideas for induction? FI? Don't say Big ol Holly, please! You are asking for a whole bunch for one little ol engine compartment!

------------------
Tom Notch

[tuna]

Randy,

I must start this reply by saying that you are asking quite a lot of a convertible. Is this going to be a "show-only" car or does the customer actually intend on driving this thing? Is racing in the future for this 'vert?

Like someone else said here, 80mm is the largest of the easy to install strokes. Anything larger will require an extremely small rod journal and a small base circle grind. The small rod journals sacrifice crank strength, something I wouldn't be too keen on if I was supercharging it and installing A/C.

You stated that this car would be a "heavily modified 79 Convertible", so does this apply to the bodywork? The problem with the supercharger, a/c, and a cooling system to keep this engine at operating temperatures will not fit in the stock bodywork. Is the customer installing a 911 style decklid, with more room for these parts? One of these may work, but I have no first hand experience if it will.

Another factor to remember is that with that much heat producing, cool air demanding parts, a convertible body isn't ideal. From '72(?) up, when Karmann got the car, they'd removed the air vents below the rear window. That means that when the car is running, cooling air is only entering through the vents in the decklid. This could be a problem.

A further problem with this car being a vert occurs when driving the car with the top down. Since the Karmann tops don't retract into the body, they impede the air flowing to the vents in the decklid. Less cooling air, higher temps: not ideal.

You could probably address this by fabricating scoops on the side of the car that takes the cool air directly to the engine.

There are a definitely a lot of issues you need to attend to before a combination like this can work. Don't be discouraged by it; it just takes a bit of engineering and forethought to make it work. Be realistic about what this car is being built for and have fun.

Tuna

[SuperRSi@aol.com]

The customer who owns this car is used to not sweating in Texas driving his black cars with black leather interiors and a black conv tops, and he likes every one of his black cars cooler inside when it is 110 degrees outside. The 79 Super Beetle convertible (not Camaro or Mustang) presently has a rotary 134A compressor with a custom air delivery system that he was happy to drop $2k on to stop sweating. He spent $3K having us install the same seats as his 993TT has, and another $3K on 18" hollow spoke wheels. But now it cannot pull the skin off of rice pudding. He knows it takes horsepower to run A/C and he wants to buy some. Today! And I want the car out of my shop after all this time.
I am only trying to find someone to build an engine and get answers in less than three months. Oliver is busy, I understand. I hope he can build engines for us but I have had difficulty with the time involved for responses to our questions. Many have never been answered. John, when you ask "what would I end up asking him (Oliver)?" How about answering all of my questions the first time so I don't need to go to forums like this and take crap from bored guys on computers in rural Iowa. And in the future when you "quote" me don't paraphrase me. Your comments were "taken in the worst possible way" only because you scolded me (twice) like a school boy without finding out that I have asked Oliver these same questions and we are still waiting for answers. Do you treat the aircooled.net customers like this when they come to you for advice? Do you respond with acres of depthless prose?
And guys, I am curious where this attitude comes in with the Holly crap, 79 Mustang etc. Why respond on a forum if you only want to criticize people or your limited perception of them?
Thank you Tom Notch for suggesting 80mm is the limit on reasonable stroke and recommending rod length. As John says, you might be an idiot but I got your opinion and it was not until you got to Big Ole Holly line that you appeared to confirm John's worries about the value of opinions on forums. You were doing so well too! No Tom, Electromotive engine management with TWM 50mm throttle bodies. They are sitting on the shelves waiting for an engine.
Jacob, the customer is actually an enthusiast of 3.6L flat sixes, V-12's and his supercharged Jag V8. That just might be why he thought a supercharged type IV would be nice. His money buddy. But I am sure he would love to ride in a Camaro once, if you will take him around the block in yours. I responded to your E-mail offer to build this engine before I read your V8 Camaro bullshit on this forum. Did you want me to take you seriously now? You may be a great engine builder but you need to hire a PR person to answer forum questions for you.
Man, if you guys don't stiffle questions I guess nobody can. OK John, you are right. The most you can expect on these forums is bullshit.

[JohnConnolly]

match the rod ratio to the RPM range you want the engine to operate in. I use 1.61-1.70 in street engines up to 8500. Of course, this must be matched to the heads; bigger heads work better with higher rod ratios. 78mm stroke is the easiest "big" engine to build for a type 4 based engine; things start getting tight at 80mm and larger, meaning you have to do other stuff to fit it in. Bigger is NOT necessarily better (my 2165 T-1 would have you wetting your pants after 3 gears); if the heads can't flow it, bigger displacement does nothing cept' move the powerband down, it doesn't change the HP total one bit.

I treat my customers the best out there (by far); send me an e-mail or place an order and you would see. But, asking unanswerable questions (books have been written on your question's answer) is ridiculous, hence the misunderstanding.

There are a lot of good engine builders out there; I'm one, Jake is another, Oliver is another, FAT is another, etc....

Perhaps Oliver needs a phone call to respond; I answer my e-mail every 5 minutes, but other guys take days or weeks to reply, it just happens to be the medium they work in.

[SuperRSi@aol.com]

Thank you Tuna for your response.

I appreciate the thought and assistance.

We will probably vent the engine compartment as Remmele does his side vents and also with venting under the license plate. I have seen a photo in a Euro magazine with an rotary A/C compressor in a Beetle engine compartment and 911 type cooling on a type IV. It appears that one might be able to shoe horn in a supercharger such as the Z-Engineering units if one utilizes a serpentine belt.
This car is not a primary driver, but it could be driven any day the owner decides not to take something else. This is why he wanted A/C, and now wants more power, big wheels etc. He owns a Porsche Twin Turbo and by reading the magazine Excellence has decided maybe he wants a set of titanium connecting rods and wrist pins he saw advertised. I did not tell him he was crazy, I only said I would look into ordering them. I asked Oliver what length rods to order three months ago and have not gotten an answer yet. I do value his opinion but I am getting to the point of deciding the long distance involved and the translation difficulties are not worth it.


I would like to thank you for a helpful answer. See guys, it was not hard.

[SuperRSi@aol.com]

Thank you John

Your first paragraph of the 12/04 8:22 post tells me that I probably should have ordered an 78 or 80mm SCAT crank at SEMA last month, and 5.325 rods from IMPRO in Italy about three months ago. I will try calling Oliver on the telephone and see if I can get this thing going. I don't want to build the engine, only the car. But I cannot have it sitting inside here much longer.

Thanks

[Joseph]

Randy,
I've read your posts and it seems nobody on
this forum has been able to answer your
questions. Why don't you go elsewhere, you
are batting zero here.
Joe Locicero
Oregon Performance Products http://www.spiretech.com/~opshroud