Variable intake runners

[Mark Boxsell]

At 02:46 PM 23/02/96 CET, you wrote:
>Mark,
>So you have convinced me. Not that I hadn't expected this.
>But _how_ do I go about it the DIY way? Anybody done this?
>
>Hey! Where can I buy 6 cheap used trombones for hacking?
>
>Seriously, I imagine lots of problems keeping such a
>device from sucking false air in through the runner splices.

Getting a seal with the pressure of the turbo would be difficult.

>
>What about using runners tuned for say 2000 RPM, to give me
>some more shove before the turbos cut in at 2000-3000?
>Using the web page that calculate runner lengths, I found
>that they would need to be really long to do that. Would that
>have any adverse effect at higher RPM?

Yes it will kill it up high.

                     +
                 +      +     
             +               +                      Long runner, Narrow RPM
range, Stronger effect, Lower RPM.
         +                        +
     +                                +
________________________________________________
0 1000  2000  3000  4000  5000  6000    RPM



                                                         Short runner, Wider
range, Lest effect, Higher RPM.
                                   +                    
                          +                 +       
                   +                               +
           +                                               +
________________________________________________
0 1000  2000  3000  4000  5000  6000    RPM
>
>I realise I should have read the SAE paper(s), but I don't
>have them. (I'm a DIY'er you see. Not working in the automobile
>field at all.) Could you give some concentrated wisdom here?

Sorry about that comment.  It took me 20 minutes to find the bloody SAE
paper in all my books and stuff. The SAE papers are such a gold mine of info
it would be worth contacting the nearest SAE office and see if any
Universites near your have them. The Universities in Australia allow members
of the public to join their libraries maybe you can do something similar.
Although some SAE papers can be "heavy going".
The best (excellent) book that I have seen (probably the only book) is
'Understanding Automoblie Electronics'. It is a SAMS book written by William
B. Ribbens ISBN 0-672-27358-6.
As for the mechanical side of things maybe someone else can suggest a good
"all round" book.

>
>I will swap to an injected engine this spring, and next winter
>I plan on converting the current engine to injection. This
>will include making a new intake manifold to take the injectors,
>so I might as well make them the "optimal" length.

Yes, well worth the effort.

>
>I'm also "brainpicking" the Weber Marelli ignition and injection
>computers to gain some insight, and find what tables I can play
>with. Anyone here who know these units? Both the boxes have
>unused analog inputs, so it would be possible to influence them
>by hanging pots on these ports. (And modify the software to look
>at them of course.)

Can't help you much here.

>--
>einarp at ade.no  ( Maserati Biturbo Spyder )
>
>
                regards,
                                Mark Boxsell
                                MRB Design.