My bug - ANGRRR - the ongoing project

[Louisben]

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

[vader]

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...

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...

[Tony Z]

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.

[vader]

HEHEHEHE!!!!!

[4agedub]

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...

[Tony Z]

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.

[4agedub]

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

[Tony Z]

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.

[Tony Z]

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

[Grand Slam Aircooled]

Mmmm interesting....

[Ron&Gill]

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

[77 super beetle]

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

[Tony Z]

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

[vader]

And money...

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

[vader]

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

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