Mythbuster: continuing project thread of my 1303 '75

[70Turbobug]

My guess this one is going to be quite a bit more aggressive? Will you be using the same Borg Warner twin scroll or are you going with a complete new set up?

[Wally]

Originally Posted by 70Turbobug

My guess this one is going to be quite a bit more aggressive? Will you be using the same Borg Warner twin scroll or are you going with a complete new set up?

Good guess!

Yes, I will use the same twin scroll 'small' Borg turbo I still have left from the old engine.
The new engine will also be equipped with these newly developed billet heads from Thorsten Pieper. Should be done before years end

[70Turbobug]

I have heard from Thorsten's T4 head project a couple of months ago, but didn't want to spill the beans. It is top quality for sure just like the oxyboxer heads. I would think 500-550hp with the same reliability as your previous engine is really possible.

[volkdent]

Drool....

Jason

[70Turbobug]

Nice parts! What cylinders will you be using? Interesting that you chose to go to a 98mm bore, I would have thought that the heads were made for a minimum 100mm bore. I can understand wanting to minimize knock but 98 is somewhat exotic, hence the question on what cylinders you will use. It's good to see you back, always loved your projects and inspirates me to keep miy project going!

[Wally]

The yet-to-be-determined bore (98 or 100) is still up in the air, but best chance is indeed 98mm. Knock threshold isn't a consideration on that aspect, trust me. I am not convinced bore has that high a correlation with knock in our application anyways.
If it turns out to become 98mm bore, I'll tell the story behind why lateron

[70Turbobug]

Knock threshold isn't a consideration on that aspect, trust me.I am not convinced bore has that high a correlation with knock in our application anyways.

I have the same opinion on that! There are so many other factors that cause knock that you can´t just pin point it on a large bore. An engine knocks in the low rpm range,so imho usually a poor head porting/cam combo and/or tuning will be the cause.Performance wise,I don´t think 2mm more or less bore will matter anyway.

[Wally]

Originally Posted by 70Turbobug

Performance wise,I don´t think 2mm more or less bore will matter anyway.

My thoughts exactly. The 100cc difference of the 2mm bore will make only a very small difference in spool, so the better/stronger cylinder (and costs) will play a more important role

[Wally]

The new bare T4 billet heads are here!

[graham]

Wow they look amazing nice christmas prezzie ,its amazing how much aftermarket stuff is availble from china now, only joking walter, how many pairs of these exotic heads actually exist i would imagine single figure ammounts ? Very Nice

[Wally]

Cheers Graham! I believe 5 or 6 pairs have been made in this batch.

[-Alex-]

I didnt see any support on torsiontubes on your car and Humble's car, i have only seen support on mendeola oval chassis and remmele chassis.

Looks like they dont need as much support as the shock towers and framehorns.

First i wanted to have tubes from rollcage mainloop to torsiontubes, but it might be not needed from what i have heard:

[Wally]

For most tracks, these trans straps are gonna be mandatory. We just made one from 6mm steel, 4 inches wide...

[spannermanager]

Originally Posted by -Alex-

I didnt see any support on torsiontubes on your car and Humble's car, i have only seen support on mendeola oval chassis and remmele chassis.

Looks like they dont need as much support as the shock towers and framehorns.

First i wanted to have tubes from rollcage mainloop to torsiontubes, but it might be not needed from what i have heard:

Alex, you are on the right track, the factory got lazy with the later production runs, many cars came off the line without even the two t/tube too body bolts under the back seat, if these are omitted, then yes, the t/tube needs tying in somehow, fitting the bolts and re enforcing the body at the bolt head is a good start, any extra bracing into the cage is better but it may fall foul of racing regulations/scruteneering at race events, check the local ASR's.

[-Alex-]

Thats what i thought, finnish vw fellow with 300hp on a splitwindow also thought that torsionbars need support more than just body bolted to it

http://ub-52.blogspot.fi/ (The tubechassis car is a different project, i have designed that rear suspension.)

http://www.youtube.com/watch?feature...&v=QOrhwTLF3hA

I am thinking either cage tied to torsionbars or remmele style bars:


http://germanlook.net/forums/showthread.php?t=11601