Board Logo

Whats twin port
clinker42 - October 11th, 2009 at 05:38 PM

Guys

When you refer to TP, do you mean the cyl head as two ports, one for each cyl and a Single port only has one port which turns into two runners, one feeding each cyl.

Thanks Trev

Anthiron - October 11th, 2009 at 05:40 PM

yes you are correct

bajachris88 - October 11th, 2009 at 05:41 PM

yea u got the right idea. :tu:

SP: one to two,

TP: two well... to two still...

Joel - October 11th, 2009 at 07:13 PM

;)

1500S - October 11th, 2009 at 07:34 PM

And why did VW go to twin port???

DH

clinker42 - October 12th, 2009 at 08:05 AM

I presume for torque

Increasing runner length by having the two ports in the head and splitting the runner iin the manifold increase the individual cyl runner which in turn increases torque

Bizarre - October 12th, 2009 at 08:56 AM

Dont think so

Buss motors are usually single ports for torque

I reckon it is so we can bolt IDFs, IDA,s and DRLA on :smilegrin:

1500S - October 12th, 2009 at 09:52 AM

Quote:
Originally posted by clinker42
I presume for torque

Increasing runner length by having the two ports in the head and splitting the runner iin the manifold increase the individual cyl runner which in turn increases torque


To save all the brain strain and horse power and torque views, the only reason that VW had back then when the first dual port head was made was FUEL INJECTION no doubt for polution control for the USA market!! They then made the carb manifolds for the rest of us with our less stringent needs of the time.

There was no difference in the output of the single or dual port engines with the stock carbs from the factory. With this, I must add that I only look at anything Type 3 but no doubt, the Type 1 and 2 engines with the single carb would have the same outcome with the stock carb.

DH

Carter - October 13th, 2009 at 06:27 AM

^ that's not what my Haynes manual says...

1500S - October 13th, 2009 at 06:57 AM

Quote:
Originally posted by Carter
^ that's not what my Haynes manual says...


Then Mr Haynes mustn't have been around when the first fuel injected VW engine came on the market which incidently was the Type 3 1600 and from my fading memory, the model year was 1968. The writeup of the day (VW Safer Motoring??) described how the heads had been re-engineered with 4 individual ports (two per head!!!) for the injection tubes to attach.

Back then we were all silly enough to think the engines would be much better with the heads on the carb models and changed them as soon as we could get the heads as spares here. Result was, and as VW stated, no difference in HP or torque unless fitted with the electronic fuel injection which suposedly gave a bit more torque but HP remained the same BUT resulting in better polution control.

DH

Matt Ryan - October 13th, 2009 at 09:01 AM

Yes it was all about pollution control and hanging on to the American market then.

Can anyone remember when ADR27a came into force? The Aussie cars of the time ran soooo hot! You could literally smell the heat off them when they rolled into the workshop!

Most of the manufacturers tried to achieve pollution control with tuning and kept engineering solutions to a minimum. They ran hotter plugs with bigger gaps weird advance curves and very lean jets. Engineering solutions were pretty well limited to an egr valve and a charcoal canister. The 6 cylinder Holdens had so many overheating issues that within 6 months they started to factory fit them with V8 radiators. Even then they still ran bloody hot.

VW did similar, starting with California models as Cali had the strictest laws earlier than anywhere else. (most of which we adopted for ADR27a)

It's the reason beetles got twin ports, the dog house oil cooler and vents in the deck lid. Then later, with further pollution tweaking making them run hotter again they added an extra row of vents in the deck lid as well.

In Australia we were lucky because our pollution laws got stricter later so we got all the extra cooling with minimal heat adding tweaking. When ADR27a finally came into force it virtually killed the beetle in Australia. By this time the Californians had gone even further with catalytic converters etc. and had even stricter laws in planning.

VW realised that they would not be able to comply with future pollution laws without a major (and expensive) engine re-design. Beetle sales were falling, Golf sales were picking up. In the end they let the Beetle die, played around with the flat engine and made it water cooled for the Kombi then eventually they let the flat four engine die as well.

All this at a time when Subaru was at the very beginning of starting to go great guns with their flat four water cooled. It's all such a crying shame really.

Regards,

Matt.

1500S - October 13th, 2009 at 10:16 AM

Thanks for the added support re dual port reason Matt. Boy! Do I remember those red holden motors in the Commodore with no advance until top gear!

Back to VW, maybe the best "sort of standard but breathed on" engine I had was still single port 1600 with a Bert Jones cam 18-58 running 8.5:1 CR as was the 1500S engine (back in 1968!!). That is the setup of the present engine except the cam is standard now. The single port heads allow the old bomb to sing along merrily at the motorway speed limit very reliably although that hasn't happened for a few years as I've been out of the country each time Nambucca has been on. Just a pity that it's not on the odd year rather than the even! If anyone could get me some new 1500 barrels I'd even go back to a 1500 engine for it as I have a set of dome pistons here doing nothing!

Some of these manuals don't give us the real truth about things as well as someone "thinking" that is the reason for something and two relays down the track it is an actual fact!! Very true on some of the Merkin forums.

DH