DDK - Die Deutschen Klassiker

neilbardsley wrote: ↑Wed Jan 17, 2024 10:40 am Keith isn't a compression ratio of 9.3 still quite modest on a race engine?

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I would consider 9.3 LOW...ish ... even for a road engine. Higher CR = Higher power ... simple as that. Could go 10.25 - 10.5 with little consequence , apart from more power.

Not particularly easy on a type4 head.

They have very limited capacity for fly cutting the cylinder register on the head. Instead you need to weld up the combustion chamber & rework it… or buy billet heads (££££)

A 2.7RS goes quite nicely on only 8.5:1 ……….

JW

jwhillracer wrote: ↑Wed Jan 17, 2024 4:49 pm A 2.7RS goes quite nicely on only 8.5:1 ……….

JW

They certainly do .............. and even better with an increased CR !

Yes, I have to agree!
JW

Agreed that high CR can equal higher HP, but it also leads to higher combustion temperatures, which in a VW motor is a problem. I've built 'a few' VW motors over the years, for road, rallycross, rallying and drag racing and for a road engine, around 9-9.5:1 is a sweet spot. If the car was trailered to every meeting, and wasn't expected to do the occasional 500+ mile round trip, I'd be bumping it up, but this one has to live.

KS wrote: ↑Wed Jan 17, 2024 6:00 pm Agreed that high CR can equal higher HP, but it also leads to higher combustion temperatures, which in a VW motor is a problem. I've built 'a few' VW motors over the years, for road, rallycross, rallying and drag racing and for a road engine, around 9-9.5:1 is a sweet spot. If the car was trailered to every meeting, and wasn't expected to do the occasional 500+ mile round trip, I'd be bumping it up, but this one has to live.

Sorry Keith - I'll have to complain about the "can" word ..... it DOES. Wether you want to or not .... is a totally different question.
(If necessary , I'll have to go and dig out the practical test (complete with my hand drawn graph) on a variable compression ratio engine from circa 1976 or 1977. University was a long time ago !!)

Ooh, pardon me. I'll reuse the word 'can' - higher CR will lead to higher HP, but can lead to engine destruction. Which can (or is it 'will') hurt the wallet. Back in the early 1970s, running 14:1 in a VW race motor (typically anything from 1700 to 2180cc at the time) was commonplace. Not without reason were they often referred to as grenade motors!

A problem with the VW Type 4/Porsche 914 engine is that the heads flex, a situation made worse when running high compression ratios – even stock engines can show signs of this. Adding two extra studs to each cylinder ('six studding') helps a lot but requires welding and machining of the crankcase, plus, of course, mods to the cylinders and heads themselves. Not cheap and not something I can consider on a budget.

Bruce M wrote: ↑Wed Jan 17, 2024 4:37 pm Not particularly easy on a type4 head.

They have very limited capacity for fly cutting the cylinder register on the head. Instead you need to weld up the combustion chamber & rework it… or buy billet heads (££££)

Yup! Remmele's billet parts started at around £2000 for a pair of bare heads, plus finishing porting/polishing, valves, springs etc. Looking at around £3500 for a pair of heads ready to go (plus Brexit tax...). Outta my league.

There’s a few others I’ve seen on socials. klaus for example with his extra cooling channel underneath. Walter (NL) has a 3 valve OHC prototype too. None very cheap!

It wasn’t exactly cheap to have my heads machined for bigger pistons, big valves, bronze guides, reworked, flowed and polished either!

And that was 20 years ago. I should imagine the adjusted price of that is knocking on the door of £2k now

The car looks great in its new paint Keith


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And today's good news is getting my entry accepted for the St Goueno hillclimb in Brittany. It seems all places were filled immediately, with the rest placed on a reserve list

KS wrote: ↑Thu Jan 18, 2024 4:29 pm And today's good news is getting my entry accepted for the St Goueno hillclimb in Brittany. It seems all places were filled immediately, with the rest placed on a reserve list

Nothing beats getting a few entries in to focus the mind on getting the preparation finished. Or, often in my case, getting it started!

JW

What date is the French hill climb please?

First weekend of June.