Date:         Sat, 22 Jun 1996 12:00:24 -0700
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         DOUGLAS <douglas@bigpig.pig.net>
Subject:      Re: 2nd Oil Cooler...

Eugene C. Palmer wrote:
> 
> >>>  but I disagree that a bigger engine
> >>> will not run hotter. Increasing engine displacement without beefing up the
> >>> cooling system is a bad idea. Even if the stock and enlarged engine are
> >>> pushing the same LOAD the bigger engine is almost always going to have
> >>> poorer efficiency at the same speed (eg. gearing). This inefficiency leads
> >>> to heat production.
> >>
> >>
> >>I must disagree. Carnot's equation states that the higher the engine temp the
> >>more efficient the unit. Work is work. If I push my split with a 36 hp at
> 60mph,
> >>when I replace it with my new 1600 DP 65 hp unit, I still only draw 36 hp (if
> >>that) to push it at 60 mph. Why would a larger engine run hot pushing a lite
> >>load? The engine will coast along at 40-50% load and should run cool. If not,
> >>you got a problem beyond an oil cooler;>)
> >>
> >>> All that aside, cylinder head temperatures of enlarged VW engines seem to
> >>> be the killer, not oil temp, and the two do not increase at nearly the same
> >>
> >
> 
> OK you guys, I have to input here.  Regardless of whoevers equation, the
> 1776 will, without any shadow of a doubt, even if Gene Berg or Jim @ Bus
> Boys himself built it, run hotter.  When I first started souping up VW's I
> thought that higher HP did did neccessarily mean higher heat.  In practice,
> I was proven wrong again and again.  And efficiency over what time frame?
> Maybe for a few minutes it runs cleaner when hot, but over a longer period,
> things will definitely start to degrade.

Just because your engine CAN produce high HP does not mean it MUST produce high 
HP. If you work it within the same envelope the only HP you need is that 
required to overcome friction and air resistance. That is the same with a large 
or small engine.

 
> It is true that, when a big engine is really running well at medium to light
> loads, it has tons of vacuum and lots of headroom.  My 2 liter FI upright
> did 65 mph at 9% throttle, and held it's temps under 200.  But when that bus
> starts to climb, it generates heat, and more of it than any stock engine.
> The 90.5 has less space for air to pass through and develops more heat.  No
> way it can beat a stock engine for coolness under full load.  Plan on extra
> cooling for your big engine.
> 
> Eug,
> '71


It only runs hotter because you ask it to do more work.

Your story confirms what I say. Running the same load. you will produce the same 
heat, or less, with a bigger engine. You pull heaver loads (climb mountians 
faster), temps will go up. I thought the discussion was about a stock engine and 
the need for extra cooling. A proper *stock* engine has no need for additional 
coolers.

The cooling system is designed to work with the stock engine. Ask it to shed 
more heat than it was designed to, and you will have problems. 

Douglas