Well, after some searching here and about the web, I am still confused as to the right path to go.

After siknye suggested that I use longer runners that wrap over the head rather than use short runners, I am now unsure as to the best path.

As far as I know,

Short runners
ideal for high revs, and really only good higher in the rev range.

Long runners
Better for creating higher torque, but not as revvy.

Then just to confuse it all

ITBs

Seem to be better for response, but harder to tune right

Single TB eaiser to tune, but not as resposive.

A plenum chamber is a must for a turbo application, so does that mean you must use a single throttle body or can I use individual throttle bodies with a plenum chamber?


And I guess one last thing, If i have runners that wrap over the top of the head, that means that to tune the rockers, i need to take of the manifold. Is this a problem?

ruby find out where roughly where your turbos going to make power then build your plenum to that its going to take alot of maths and screwing around but the end result is an extremly good turbo motor
and if you have it go over the head you make a flange on the manifold side so the manifol splits in half

in blower applications, the plenum isn't critical on even fire engines, (Dat)
on odd fire, ie Ducati and HD v twins, the plenum needs to be at least twice the engine capacity..
a screw type compressor makes boost as it leaves the blower, where as a roots type builds pressure from the valves back..

the TQ v's HP length runners is mostly for Natro engines...

If you want to run a big laggy turbo which hits hard when it spools up, then making then runners a bit longer will improve your low down (off boost) torque. I've read that during R&D Jaguar actually acheived VE (Volumetric efficiency) of greater than 100%, (at one specific rpm) when using very long runners on an N/A enigne. If or when I ever build an injection manifold, I'd go for long runners too. Some car makers now have dual length runner maniolds too. The runner comes out and curves back around on itseslf, then the plenium has short runners coming out of the plenium back into the head with a butterfly in each one to enable the runers to go from long to short.

when i started playing around with turbos i wanted to know these very questions, lucky for me one of my oldmans mates is a mechanic and has been for about 30years so there not much he doesn't know, i just asked him. I'll try and pass on some of my knowledge to you.

A rule of thumb for naturally aspirated EFI manifolds is that long, narrow intake runners result in better low RPM tourque, while short, wide runners give top end horse power, and as A14force stated previously thats why manufacturers use multi-length runners in their performance cars.
However, there is some debate about how important it is to worry about intake runner length for turbo engines. Above the boost threshold, one argument goes,long narrow tubes simply add flow resistance and reduce VE (volumetric efficiency) of an engine. For ultimate horsepower production it is argued that short and wide is better, but of course this varies between person to person, depending on who you ask. In my opinion and expirence it doesn't matter all that much, if your going for a full blown turbo engine that is used for something like drag racing you can go with the short wide runners,but if its just to be used as a hot-steeter it doesn't matter all that much, Also seeing that the A-series isn't a cross flow head it all comes down to space, thats why it would be a good idea to have the intake run over the top of the head, this also makes it easier to hook it straight into the intercooler if needed.

As for the throttle bodies, i follow the KISS philosophy(Keep It Simple Stupid, one of my oldmans sayings!) just stick to the single TB, i have heard of people running TB's from XF falcon, Magna or camira TB's. Make it easier on yourself.

A14force- Ihave also heard about jaguar testing a VE of 100%+ i also know that NHRA pro-stock dragsters can achieve VE level as high as 115-125% within narrow rpm ranges at their tourque peak. Could you imagine an A-series acheiving a VE of !00% or greater??? my mind boggles at that thought!

if its going in a 1000 the runners will not fit over the rocker cover so that rules that out. really depends on what you are after, but if you're not trying to extract every last kw then just try to make it as long as you can, nicely tapered towards the ports, include some velocity stacks/ram tubes and make the plenum no bigger than 2 x your engines capacity with a nice sized (not big) throttle body. quads are cool but can complicate your setup a little, but if you buy some efi tb's from a bike then they have injector bosses already included. i'm making a manifold to suit some gsxr throttle bodies with sikyne's help. boofhead is doing the same as is pigdog for his l series.

there's an efi revolution building

i will also be going down the turbo efi highway soon, lagwagon i would like to know more about the motorbike throttles maybe you could start a thread? any help or info is greatly appreciated

cheers blake

i was told that plenium should be between 40-60% of engine size, so that means for a 1.5l you need a plenium thats roughly 750ml or there abouts.

There are litrally a million way that it can be done and depends on many factors one main factor is cash and the another being time.

What is this engine going to primarly used for? that'll be easier to give suggestions.

with all these EFI systems there will be some quick machines out there!

Hey Lags, did you ever finish modifing that CA plenium for an A-series? i saw a pic in the random box, how did it go?

Well the car is really planned for a quick street with the odd drag run.
It wont be a daily driver, but i expect it to get plenty of hours on the road.

Not fussed about bieng a dyno pony or a competition winner. Dont get me wrong big HP numbers are good for bragging rights, but thats about it.

i wanted to give this engine the works.
EFI (sequential injection with individual coil packs
ITBs (if reasonable)
Forced induction (turbo or S/C)
intercooler

All under the bonnet of a B10 sedan, with I think the original paint, with nothing more than a set of mags at most. Maybe some window venitians.

for boosted application runner length less important .force fed therefore no ram tuning effect(no reverse pulse).packaging is more important. shorter path results in less lag. heat management more important than everything else put together
dazza