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Designing your own TB's.

6K views 107 replies 29 participants last post by  Animal 
#1 ·
Designing you own TB's.

evenin' all.

Having aquired a (soon to be un-mullered) 3.0L v6, I'm having a stab at building some tapered tb's for it. Sounds ambitious? Well it would be, except for a couple of key things.

the heads are basically the same as the 1.6 16v, except for having 3 cylinders per head.
the cylinder cc is the same as the XE (bore is 86mm, stroke is 85mm)

The main problems are that there's **** all space, as you've got to try and fit 6 tb's in the space 3.5 tb's normally fit in, and that the bonnet is going to have to be extended up so that the induction system will be long enough.

The basic paramaters are:

45mm throttles (sourced from heavily chopped varijet2 carbs)
throttle plate will be approximately 200mm from the inlet valves
overall length will be 35-40cm in length
each cylinder will have 2 injectors, one in the trumpet, one in just past the throttle plate. It'll use either all XE cream injectors or bottom ones V6 upper ones XE Cream)

I'm prototyping it using plastic (white chopping boards) as it's easy to cut and very cheap. Final system will be a mixture of aluminum and fibreglass.

It'll be controlled by an emerald ecu, as it's much cheaper than the alternatives, and can do everything that's needed.

The exhaust manifolds will need to be fabricated, as the std headers are dire (the 3 exhaust ports each side are connected together with a cast iron box). Which will be fun. again, the XE and 1.6 manifold design are available, and coupled with a few informative books on exhaust design, I'll have a field day with it!

The rev limit of the v6 can be approx 7750, as the stroke is similar to the XE, and ARP rod bolts will fit.

If the 1.6 16v can make 164bhp on TB's with std cams, i should be able to get 280-300 bhp if i can get the TB design correct and the manifolds effective.

I've looked into getting some cams made for it, and i'll need to get them cut from billet as blanks aren't available, so it'll end up costing about a grand :eek: for a set of 4 cams.... still, if the 1.6 can make 190 from the 284/278 cams, then the v6 could make 320 - 330 Bhp ish with 240ish ft/lb.

Understand that these figures are very ball park, and were obtained by dividing bhp by cc, then multiplying by the new cc then taking some off, to try and take into account the valve areas (The 1.6 has much more valve area which will help it at higher rpm).

Photo's to follow..........
 
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#35 ·
Braintree said:


Thats roughly what I had planned

I'll learn one day
the main problem with that, is you'll need one mother of a bonnet vent, also you'll need a sharp kink in the airflow, and according to jenvey, you're supposed to avoid s bends, whuch is exactly what you'll get with that design.
 
#38 ·
Matt - I don't know the stats of the engine, I may be able to get contact details though.

No offence re the looks of the engine, but that one in the Mk1 will take some serious beating. I get the ompression your would look a bit more raw and functional - not meant as an insult mind. :D
 
#39 ·
they reckon 350mm for a 9000rpm system, but i'd prefer to start long, then reduce when testing on the rr.

I'm just about to go and measure, so i'll let you know.
 
#40 ·
MikeWarner said:
Matt - I don't know the stats of the engine, I may be able to get contact details though.

No offence re the looks of the engine, but that one in the Mk1 will take some serious beating. I get the ompression your would look a bit more raw and functional - not meant as an insult mind. :D
none taken, most of you know i prefer performance to masturbating over clean engine bays, but i'm in no hurry with this, so it may look half decent....
 
#42 · (Edited)
just done a bit of measuring....

inlet valves are 32mm (xe is 33mm)
exhaust are 29mm (xe is 29mm)

distance from inlet valve to end of head is 85mm ish

and after a quick bit of maths.... i've decided to aim for 400mm as opposed to 450mm


Tuned      Induction
rpm          length in mm

1000  3150
2000 1575
3000 1050
4000 788
5000 630
6000 525
7000 450
8000 394
9000 350
10000 315
11000 286
12000 263
13000 242
14000 225
15000 210
16000 197
17000 185
18000 175
19000 166
20000 158


so i'm going to be looking for an assembly that's (400 - 85 = 315mm long)
 
#43 ·
Sounds absolutely perfect to me mate!!!!

Agreed on the s-bend limitations, you need to try and get a large input angle onto the head itself. That way the s-bend will be more of a chicane!! :D

To be honest mate if you're gonna have the trumpets above the opposing banks rocker cover thats gonna take up some room and be quite awkward if I'm thinking along your lines. The reduced length now, 315 as opposed to 450, is gonna put the trumpet quite close to the centre of the banks.

Might need a rethink on positioning!!

I'll sleep on it and post any ideas I have mate. I'd love to see you get this up and running smooth as a baby's bum!!
 
#44 ·
aha, this will be going into a manta,



which has a huge engine bay.



and I've got loads of space to fit it into. if necessary, I can drop the engine slightly, and I've no qualms with cutting a hole or 2 in the bonnet......
 
#45 ·
Matt, - you're so on drugs!lmao

All sounds an interesting plan though and it takes people like you to try these things out.

My initial thoughts on this are the same as what has already been said.

Good luck and remember to keep asking whenever you need help.
 
#47 ·
#50 ·
Sounds wicked!! Keep up the work and let us all know how it comes along!

Just out of interest - anyone know the specs of the one in the picture??? Is that a Mk1 Astra??? anyone got any power figures for it??
 
#51 ·
legend has it, that it was built by a freind of dave franczak, in a text book case of "keeping up with the neighbours"

I expect based on standard 2.5 spec that it probably only had about 200-220bhp (if 2.5 cams remained)

either way, it never lived up to its spec. probably due to power to weight, and logistical problems.
 
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