90.5's or 94's?

[VWCOOL]

[VWCOOL]

[VWCOOL]

[75smith]

[AlteWagen]

Cool, how do you measure the cylinders for out of round? Bore gauge? Feeler gauge? Even cross hatch after hone? Compression test or leak down?

I know a few people who claim their engines never run hot but they have no instrumentation to actually monitor temps.

I know another guy that says that his thin wall 92s have been no problem in his camper for years, never runs hot and is a daily driver. What he doesnt say is the engine leaks a ton of oil from blow by, the cht sender is connected to one of the cylinder head tin screws, and his daily commute is only 100 yards from home to work if that.

Here is my own personal experience with a set of 94mm Cimas from 87 that I have put close to 100K miles myself in various engines and vehicles under my heavy teenage foot. I got them used so really have no idea how many miles they had before. My first build was in a light weight street/drag bug running high compression, NoS, external oil cooler and no gauges. I got around 40K before I tore it down to do a cam change and inspect. I then de tuned it, hone and re ring new heads and stuck it in my 63 bus/parts hauler. Another 30K or so in that application weighted down with load most of the time, again no gauges but with a stock doghouse cooling system. Another hone and re ring and a web cam and it went into a baja for 20K+ before it was retired and disassembled around 2005. In the baja it took some regular off road beatings blasting fire roads and chugging around at low rpm. Still no cht gauge but the engine seemed happy with the open engine compartment and all the cooling air.

Last year I took them out of storage and put together a "shop floor" engine. Now that Im older I run gauges in all my rides and have a bore gauge to actually measure for out of round. Guess what, all of the cylinders were just slightly out of round. Since the entire long block was going to cost less than a set of new P&C I just said fuck it and put it together and figured it for a round the town beater. After break in I performed a compression test and surprisingly the numbers were not as bad as expected and the engine ran well despite some oil leaks. Did they work? Yes. Was there blowby? Not excessive. Would an 80%r know any better? No.

What I dont know is how long the cylinders were out of round since at that time I didnt have a bore gauge. Were they wasted when I got them? Who knows.

Moral of the story...ignorance is bliss, and some are more blissful than others
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[raul arrese]

[bugninva]

[raul arrese]

Maybe cool's 94's last forever cause he doesnt make any real power and has 5 to 1 compression ?? just a thought ?

[jeff68]

Raul, buginnva, Altewagen, 75smith - You all understand what I was asking and restated what i had said, thanks. It's clear VVWCOOL didn't answer and maybe doesn't understand. Maybe his old highly used 94 pistons and cylinders are working great and to the highest level of performance possible.....but maybe they're not. Clearly from his statements / writings they are working good enough for him, and that's great for him. From what he posts he hasn't collected data, measured the parts or monitored their performance and that's fine. IMO you can tell people what you THINK works from "evidence" like this and nothing more. To really know you have to collect accurate, real measured data and performance results. Take his information for what it's worth to you and use your own jusdgement that's what I do.

[[email protected]]

VWCOOL,

you are asking (demanding) for evidence, when you are incapable of providing any of your own to counter the experience we have offered you.

I've been in this hobby for over 35 years. I've been through and seen a lot. 94s have always had a "reputation". I think a lot of it was since 92s were so bad, how in the World could 94s not be worse?

I am also commonly mis-quoted. I have always said that 94s run hotTER, I never said they run hot. I can give you conditions that will burn up a 1300 or 1600. The more displacement the easier it is to do if you are not paying attention.

There is nothing wrong with 94s, but I have always said I would not run them on

Convertibles
THINGS
Busses
Type 3s

92TWs are ideal for these applications.

That being said I run 94s for most everything else. So asking my why they "don't work" is kind of pointless, since I like them a lot.
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[VWCOOL]

[VWCOOL]

[u]

[yamaducci]

VWCool,
That was a well thought out post; however, I think that the type of evidence you are looking for is not going to be found here by ANYONE on this board. It sounds to me like you are not asking for experience or even testing done on VW's but more of a testing done on the properties of the metal or alloys used in construction of the parts. The only people who know that specifically are going to be the foundries who produce these parts and then to prove each alloy's heat transfer rates or warp-ability or whatever detail you are looking for.
Each person who has replied with their experience has not been sufficient proof and even common sense theory is not good enough to "Prove" that there is a difference. Frankly there are too many variables besides just the size of the piston and the thickness or type of material used for the parts. There is compression, Tune, cooling efficiency, cooling effects of intake charge etc, etc... So many factors.
The basics that we can all assume to be correct are:
1) More surface area equal more friction and heat.
2) More power equal more heat
3) Larger size and less fin area equal more heat retention or less heat dissipation; however you want to look at it.
4) Thicker metal heats and cools more stable and resists warp/crack more than thin metal.
5) Thicker metal has more structural integrity.
6) Wider pistons do not release heat out to the cylinders and away faster than smaller pistons therefor they increase the chances for detonation.


Here is a 94 Cylinder that was cracked due to heat and then subsequent detonation (I am assuming).

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[rockurob]

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[SBD]

There's no secret as to why Cool's engines don't run hot. He lives in Australia so his engines are always running upside down. Therefore the cylinders are always bathed in massive amounts of oil that keeps them cool.

[neil68]

[yamaducci]

It still baffles me why no company has stepped up and created 92's or 94's with more meat in the main section of the barrel and added larger fins Then simply stamped out larger Cylinder cooling Tin to match the cooling needs to keep them round for 100k miles. Seems like a no brainer for a company like CB Performance, Empi or BugPack or even AA at this point.
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[rockurob]

[yamaducci]

[Dan Ruddock]