Type 4 mechanical compression ratio, Why is the factory compression so low? Options

[Beebo Kanelle]

OK, here's a fun one for the novice to ponder and you experts to answer:

Why is the factory mechanical CR so low?

and for reference, what is the highest mechanical CR that can be physically achieved? assume no octane limitations -

I'm just looking for the design limit for the highest CR that can be / has been in a Type 4 engine using available technology.

Thanks

[Beebo Kanelle]

wow! Thanks to all for all the input.

to answer jd74914 questions: 1) initially, I just use a spiral notebook and a pen to gather info, 2) initial dynamic modeling using 'Dynomation", 3) take the data and build one... see how long it takes to blow up!

The #1 concern that pops up from the comments, after 'it can't be done', is the cylinder/head sealing - I can only assume that the Type 4 engine 'flops' around - and what about stability and flex of the crank?

That would necessitate small bore to minimize flex. But please tell me, is the head/cylinder just a registered fit under compression?

As far as air-cooling goes, does anything compare to Mr. Raby's DTM system used in conjunction with Nikasil?

Is there a book or source with all the torques, tolerances and dimensions? I know that after 40 years, there must be a lot of hard data, somewhere.

Thanks again

[Mark Henry]

wow! Thanks to all for all the input.

to answer jd74914 questions: 1) initially, I just use a spiral notebook and a pen to gather info, 2) initial dynamic modeling using 'Dynomation", 3) take the data and build one... see how long it takes to blow up!


The #1 concern that pops up from the comments, after 'it can't be done', is the cylinder/head sealing - I can only assume that the Type 4 engine 'flops' around - and what about stability and flex of the crank?

Crank has two throws per main journal thus is has RPM limitations. You can't reduce rod journal size for different rod (ie rabbit rods) already been done, too much flex. Cylinder head bolt pattern is too big, upper studs shorter than lowers, fire rings have been tried, 5th head stud has been tried....

Never said "it can't be done", just said the T4 design has it's limitations and that conventionally in most cases it will have already been tried or done.
You have to keep in mind guys have been hopping these things up since the 70's and for the type 1 since the 50's.
Many also have proven track records , proven engine building creds and/or or proven products lines. We are talking real stuff not just theories.


That would necessitate small bore to minimize flex. But please tell me, is the head/cylinder just a registered fit under compression?
It sits in a bore

As far as air-cooling goes, does anything compare to Mr. Raby's DTM system used in conjunction with Nikasil?

In a 914 I still say the DTM is a waste of money, the exception would be a full race car with the shrouding cut away.
In VW beetles, T4 upright fan conversions the DTM is the snizzle.
I built a DTM/Joe Cali/Stock T1 hybrid shroud for my '67 bug, it came out great, but in retrospect the amount of time spent on it I wish I has just bought a DTM.
A DTM can be installed in a day.

Is there a book or source with all the torques, tolerances and dimensions? I know that after 40 years, there must be a lot of hard data, somewhere.

Bentley manual (IMG:style_emoticons/default/confused24.gif) Even performance most of that stuff is still the same as stock.
The stuff that changes for performance is mostly just dimensions.

Thanks again

[DBCooper]

[b]In VW beetles, T4 upright fan conversions the DTM is the snizzle.
I built a DTM/Joe Cali/Stock T1 hybrid shroud for my '67 bug, it came out great, but in retrospect the amount of time spent on it I wish I has just bought a DTM.

You built a Cali shroud? From the time of the Usenet RAMVA groups? Man, you HAVE been around for a while, so hat's off to you. I still have an unused original Joe Locicero DTM kit in a box somewhere, before Jake took over, with Joe's own handwritten instructions. Good man.

[Mark Henry]

[b]In VW beetles, T4 upright fan conversions the DTM is the snizzle.
I built a DTM/Joe Cali/Stock T1 hybrid shroud for my '67 bug, it came out great, but in retrospect the amount of time spent on it I wish I has just bought a DTM.

You built a Cali shroud? From the time of the Usenet RAMVA groups? Man, you HAVE been around for a while, so hat's off to you. I still have an unused original Joe Locicero DTM kit in a box somewhere, before Jake took over, with Joe's own handwritten instructions. Good man.

That original DTM by Joe would an OPP (Oregon Performance products).

I've also used FAT and Sharpbuilt shrouds in the past.

My all steel shroud.
(IMG:http://www.914world.com/bbs2/uploads/post-73-1403365366.jpg)