RE: Supercharging - but seriously folks

["Mark Battley" <m.battley@domain.elided>]

Biba commented:

>While it'll never happen in my lifetime (unless that ship I've been
>waiting for actually does dock in Irwindale), has anyone done the combo:
>Supercharging (using a Real supercharger) on a Twin Spark engine, using
>a programmable EFI system?
>
>I have no experience with any of the above, but it seems that this might
>make for a very interesting engine. I know nothing about turbos but have
>driven cars with very hot cams and would find myself humping in the seat
>to help get the car off the line. Suspect turbo lag would require me to
>do the same.

I'd suggest really strongly that you find an excuse to drive a modern (or
even one of the better older) turbocharged car - I would be very, very
surprised if you feel a lack of power off the line, or find lag to be a
problem. Most relatively conservative factory installations (say 80-120
hp/litre), spool up very quickly, trading maximum power for drivability. A
properly setup turbo installation is completely different to drive than a
car with hot cams, or even the modern variable valve timing wonders that
give lots of power, but only when you reach 7000-8000rpm. Peak torque for a
turbo engine is usually at much lower rpm than a similar normally aspirated
engine, and that's how it feels to drive - the mid-range "wave" of torque is
intoxicating.... :-))

Modified, or more extreme factory turbo cars sacrifice some lower end
response for top end power, but the power you can get is phenomenal (150,
200, 300 hp/litre, or even more), so that's a sacrifice that some are
prepared to make. And with sequential turbos and ECU controlled boost the
torque band can still be quite wide.

>Really showing my ignorance, but do / did all Twin Sparks use Bosch FI?
>Apparently Zamani Zambri is in the process of making a successful
>conversion on a big honkin' 3.0 V6. This somewhat tells me if the TS's
>are Bosch, the inlet system can be converted.

Kelly McCrystle commented:
>Some TS engines came with Carbs

Which model was this used in? I know that some have been converted to carbs
when they have been put into other cars, but I didn't know that Alfa
produced the (modern, not GTA) TS engine with carbs. 

But as has been pointed out here already, any of the Bosch injected cars can
be relatively easily converted to programmable EFI, and even the SPICA
manifold can be modified to take electronic injectors. For a forced
induction car the TS Motronic plenum has the slight advantage that the
throttle-body/intake faces forward, rather than over the cam covers, which
is slightly more convenient if you want to plumb in a front air-air
intercooler.

The other question is why use the TS engine, and not the older single spark?
The TS has slightly better port design/airflow, but that matters less with
forced induction. I have been told that the TS head is less durable (more
chance of cracking with higher temperatures and pressures of forced
induction) than the old head due to having two plug holes, but I don't know
how real this issue is. I think that the TS engine also has a higher
compression ration than the 9:1 of the older engines (what is it?), so you
are likely to have to go to lower compression pistons for even low boost,
9:1 can successfully be used with relatively low boost, particularly if the
engine management/EFI system has boost controlled ignition retard, as most
do.

>Oh yeah, when you send the plans & shop manual, please include
>crankshaft pulley 'fired' ignition. The distributors on TS's leave a bit
>to be desired, aesthetic wise.

One of the appeals of the modern aftermarket engine management/EFI systems
is being able to dispose of distributors (which wear, and are often stuffed
on old engines) - on a four cylinder you only need two coils/ignitors, and
being able to integrate the control of injection and ignition (as for
Motronic, but programmable) is very useful.

It seems to me that the aftermarket engine management/EFI systems have now
reached the cost/performance level where they are a realistic option for
converting older cars. For some reason Australia seems to be the source of
quite a few good systems. As well as the Autronic there is Haltech,
Microtech (good features/$), Wolf....

I have been in contact with a few people here on this list who have already
converted cars to forced induction, if there is anyone else I haven't found
yet, please put your hand up....  Thanks!

Mark Battley
Auckland, New Zealand.

1973 Alfa Romeo 2000 GT Veloce  (needs more power...)
1989 Fiat Uno Turbo (scary already, but still want more power...)
1989 Fiat Croma (too slow, better buy another car, but what?)
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided