Aircooled VW South Africa

that's kak funny, I can just imagine the situation, should be on reality TV Cheers Ben

Ron&Gill wrote:I wouldn't know... I'm not one for wheel spinning and making a lot of noise at the traffic light. The only time I showed off was when I tried to scare Anakin... Hehehehe that was fun nice little sideways drift around the corner. Ithink you scared yourself a little too..

Once I dropped the clutch on Rumours in a fit of road rage and she axle-tramped so hard, the voltage reulator broke... in Upington on 31 December. 'Twas hot... 'Twas after one... 'Twas when the bottle store was already closed. 'Twas not a good idea...

Tony Z wrote:Traction isnt too much of a problem as I dont try to brake things and dont go banana's trying stupid shiv. But I do have plenty rubber on the road (215/45/17) to help and I definitely feel that I have had the front tyres in the air on a few occasions.

Except when you are snaking down the main road in George trying to keep up with The DarkSide & a Gti behind you... And lets not talk about going around corners with huge amounts of understear from those tractable 215/45 r17's that just grip and dont turn...

Yes Anniken... you keep living in your little world

But yes, you are correct, I did loose traction on york Road, nearly taking out both ANGRRR and the Darkside, as well as a GTI. Early gearchange brought that back under control.

HEHEHEHE!!!!!

Tony
Do you know what size the exhaust ports are on your engine? I'm trying to figure out what is the relation between valve size and exhaust port size...

They are not much bigger than stock. Apparently the stock exhaust port is good enough to match a 42mm inlet valve (or there abouts). I had the 38mm seat installed, cleaned up a good entrance and a smooth radius into the port, while widening it slightly around the guide and made it all flow to the original hole. Cleaning the hole up slightly.

Some people talk about 105% of the valve size... as long as the port is smaller than the exhaust tubing.

If I look at modern type multi valve engines this can be seen on most of them, but whether it will work on a 2 valve engine, I'm not sure. My engine is as the point now where I need to decide what to do with the heads before they go back on. It's 42mm intake and 37 exhaust valve with 1 7/8" exhaust system. Right now the exhaust port is around 34mm

I got a small chart which says your exhaust is too big by a long shot....
1915cc, 1 7/8" exh works from 4350rpm to 9999rpm
Will try to post the chart.

The smaller port helps keep the speed up, which after the initial blowdown pulse, should no-longer be a restriction.
Then again, 105% of the valve size... think about having a stem in the way, the 38mm valve itself only offers a hole 33mm big if you exclude the valve seat. Taking into account the valve seat being 1.5mm less in diameter than the valve (normally probably 2 to 3mm), then the seat hole for for gas to move through is 36mm with an 8mm valve stem, which equals an equivalent of a 31.1mm hole.
So your 34mm port is already 110% the size of the actual hole you are providing at the seat.

This chart was recently published in a VW magazine somewhere. It shows the "working range" of an exhaust vs rpm and engine size

Mmmm interesting....

No Anakin! Exhaust size is NOT the only limit on rpm...

WOW what an awesome bug I really envy you, if I only hd the know how on how to work on my bug...well done

thanks man....
you also need plenty patience...

And money...

And mmmm a seatcover to work out your frustrations on!!!!

Ron&Gill wrote:No Anakin! Exhaust size is NOT the only limit on rpm...

Absolutly correct Obi-Wan the limiting factor is Emperial Credits....