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Author Topic: boosting s'charger pressure  (Read 2120 times)
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« on: November 01, 2008, 04:48:54 PM »

The max operating pressure Lancia recommends for the Beta s'charger is 1.4 bar. the max capacity is 1130cc nad gear ratio 1.32 to 1.
Does any one know by what gearing ie how many less teeth on the s'charger pulley
and how many more on the crankshaft pulley can be used to get up to the safe max operating boost of the s'charger or indeed can it operate at higher than Lancia's max 1.4 bar figure? That is is it sufficiently robust to take more?

I used to run the VX in a Stratos replica. I didn't need the power steering
and an easy way to uprate the boost from the supercharger was to machine the
centre out of the pulley from the P/S pump and slip it over the crankshaft
pulley with a couple of spot welds to keep it in place. This geared up the
supercharger by 10% or more, had an appreciable effect on an already fast
car and seemed to have no ill effects on the reliability or longevity of the
engine. In the Beta application this method is a problem as there isn't
enough space for a direct drive between the crank and supercharger pulley,
you need to retain the power steering pulley to route the drive belt past
the inner wing, I know as I looked into this when I ran a VX HPE. The only
practical way of uprating the supercharger without affecting the power
steering pump was to replace the cog on the supercharger with a smaller one
and source a slightly shorter belt. And I wasn't prepared to remove this cog
on my car for fear of getting the lobes out of phase on a car that ran just
fine! When I wanted to be a hooligan I just took the Stratos out!
Unfortunately for the VX in the Stratos an overfilling of oil episode at
Aintree race circuit (in an attempt to maintain oil pressure through a
difficult chicane) resulted in a blown crankshaft oil seal whilst chasing a
250 GTO resulted in an engine swap for an Alfa V6 but it was worth it for 10
laps in the passenger seat of said Ferrari at racing speeds with LOTS of
opposite lock/four wheel drifting!


This is my understanding of the situation (which does NOT mean that it is correct)!

The VX runs with about 6-7 psi boost. That is about 0.4-0.5 bar ABOVE atmospheric. Hence the figure of 1.4 bar while being correct in an absolute sense is misleading IMO. By some quirk of fate I got a boost gauge today so I will let you know the story with my car once I find out.

The cheap and easy solution for getting more boost is to have one less tooth on the small pulley at the supercharger end. I have been advised that this is not good engineering practice and could cause problems because that pulley is already fairly small. My view is that you can probably get away with one less tooth judging by the experience of others but that is it.

It is supposed to be a better idea to make a pulley with more teeth at the crank end. That is a more difficult and more expensive proposition but there is no reason why it cannot be done. However, what concerns me about that approach is: (1) the possibility that it may cause problems with the power steering pump; (2) it involves more hassle to remove if for any reason you want to revert to the standard arrangement.

My plan is to see what boost I have now and to fit the little wheel when I change the belts. Then see what boost I have afterwards. As I see it, the main problem with running higher boost will be to avoid detonation in the absence of a knock sensor and an ECU as in modern turbo-charged cars. I'm planning to have a careful look at the boost and the mixture settings to make sure that the mixture does not become too weak. In addition, I will probably to go the HPX ignition system to ensure that there is better control over the ignition timing. A small increase in boost should be OK, I suspect that anything more is asking for trouble without other modifications.



Pace Products (Anglia) Ltd make pulleys and crank pulleys for most cars and do modifications so I might drop them a VX crank pulley to copy with instructions to ever so slightly increase the number of teeth on the supercharger cog and also make a smaller s'charger pulley. Could be interesing........hopefully could still use the standard belt length but better to imncrease to a 1 inch belt though.


Hi Andrew

I used the pulley from a Fiat 131's air-con unit (or was that a 132 ?) on
the crank, the teeth on the belt fit perfectly. The psi was increased from
6.5 to 9 and the supercharger rpm increased by 10%. There is a safety valve
on the blower, it's factory set, at 15 psi. 10% doesn't hurt anything for
normal driving, 6000rpm at the crank would equal 6600rpm for the steering
pump and blower. How often do you hit 6000rpm ?

Just be sure to put the belt on tight, I snaped two when they jumped teeth.
Got it right now though. Been running the above no problems for 12 months



Did you make any other mods to the car at the same time to deal with the extra boost?  Has it affected the steering feel at all?  Mine feels somewhat vague at the best of times so I'm concerned about the power steering making it feel even lighter with with a bigger crank pulley.


Thanks for your advices. Chris has a point. I s'pose a larger pulley could be used on the power stearing to compensate.....................where does it all stop.


Re Andrew and where does it all stop.
Andrew, I have had 24 years of playing around with Lancias, let me assure
you it NEVER stops.
A classic example. I had a HPE Volumex. Set out to change the brake pads,
thought the rotors looked " a bit thin". Marginal for machining, so why not
get a new set, right?, Why not go to Tarox and get a set of their much
procliamied calipers whilst you are at it?
So whith new calipers and rotors, the rake lines look a little shabby, so
why not replace them with some quality braided material.
Now obviously one has to renew all the amterials back to the slave cylinder,
which of course could do with an overhaul, seeing as I had all that stuff
out anyway? Right?
And where brake fluid had weeped on the firewall and the paint had lifted,
well that needed to be repaired didn't it. Now if you paint one sedtion of
the firewall it makes the rest look shabby, so as the timing belt needs
replacing and the engine could do with a clean up why not haul it out and
respray the engine bay whist you are at it?

Well with the engine out it is obviously the time to change the leaking CV
boot and whist I am at it repack the CV, flush out the radiator, replace the
overflow bottle claen up the wiring looms, cleanup the fuse block, clean up
the earths aof all those wonderful Lancia electrics, check the thermostat,
renew all the hoses, replace the supercharger belt brace two cracks in the
subframe, replace the guard liners. Oh and replace the old Carrello
headlights with new ones, touch up the stone chips on the spoiler and of
course reassemble.

It only took six months and the brakes worked a treat. After that was the
upholstrey which is another story.

So No Andrew, it never ends

PS oes anyone out there have a wiring diagram for RHD 1977 Coupe?


Infact you've hit on an idea. How did you go about fitting the Tarox discs and calipers as the Beta has a dual split system, the front calipers having dual circuits linked to the rear I think si you need I similar caliper?
I need to uprate the brakes and have been looking at the options obviously the easier options are preferred.


I have a copy of a wiring diagram from the haynes manual which is suppose to
cover all betas from 73 to 80 if thats of any use let me know



The pressure for the power steering is regulated, it's operation will not be
affected. The increase in power is there, but it won't blow your sox off,
no other mods are needed for this alone.



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