PAS Shock Horror!
Discussion
I found out last night that the power steering pump eats about 10-15bhp!!!! No wonder the new one doesn't feel as quick as my last one.
Now, the obvious solution is simply to disconnect it, however ... do the PAS 500s have a faster rack than non-PAS 500s? If they do, then it might make it impossibly heavy without the pump.
Does anyone know, or could some kindly soul with non-PAS let me know - how many turns of the wheel lock to lock? then I can test it on mine tonight and see if there is any difference.
10bhp ... Jeez
Now, the obvious solution is simply to disconnect it, however ... do the PAS 500s have a faster rack than non-PAS 500s? If they do, then it might make it impossibly heavy without the pump.
Does anyone know, or could some kindly soul with non-PAS let me know - how many turns of the wheel lock to lock? then I can test it on mine tonight and see if there is any difference.
10bhp ... Jeez
The PAS rack is faster and very heavy without the PAS.
I wouldn't worry about the PAS drain as it is variable and there are many other factors that affect power to weight... like driving with a spare wheel and a full fuel tank all the time. Don't carry passengers as they can effectively cause the car to loose another 20-30 bhp. Don't run with a fans/electrics/ICE etc as that is another power gobbler.
Lets assume 300 bhp in a 100kg car (rough approx for the maths.... )
Adding 100kg (big passenger) is an equivalent 30bhp drop.
Running full fuel tanks is another 15 bhp compared to running empty but the inconvenience of stopping at every petrol station is not to be underestimated.
Just enjoy the car. BTW I reckon the PAS cars are easier to control on the limit because of the reduced effort and faster rack which makes them quicker through the twister bits which more than makes up for the slight power loss.
I wouldn't worry about the PAS drain as it is variable and there are many other factors that affect power to weight... like driving with a spare wheel and a full fuel tank all the time. Don't carry passengers as they can effectively cause the car to loose another 20-30 bhp. Don't run with a fans/electrics/ICE etc as that is another power gobbler.
Lets assume 300 bhp in a 100kg car (rough approx for the maths.... )
Adding 100kg (big passenger) is an equivalent 30bhp drop.
Running full fuel tanks is another 15 bhp compared to running empty but the inconvenience of stopping at every petrol station is not to be underestimated.
Just enjoy the car. BTW I reckon the PAS cars are easier to control on the limit because of the reduced effort and faster rack which makes them quicker through the twister bits which more than makes up for the slight power loss.
Fair point Steve ... but, and this is the bit I forgot to mention, my cars are regularly driven at high speed and I find that with the PAS, purely theoretically of course, at 130 plus the front end feels VERY light. What it would be like at 150 I dread to think!
So, if disconnecting the PAS is going to be even heavier than the non-PAS cars, I presume there is an option to have the valves replaced with ones that give a heavier feel?
I was also chatting about the benefits of a front splitter and the point was made, quite reasonable I thought, that the front end lightness isn't due to aerodynamics, but the light steering, so there is really no need for a splitter if I can get the steering weight sorted. Does this sound reasonable?
So, if disconnecting the PAS is going to be even heavier than the non-PAS cars, I presume there is an option to have the valves replaced with ones that give a heavier feel?
I was also chatting about the benefits of a front splitter and the point was made, quite reasonable I thought, that the front end lightness isn't due to aerodynamics, but the light steering, so there is really no need for a splitter if I can get the steering weight sorted. Does this sound reasonable?
Why don't you take the car to your nearest private test road (read sunday afternoon car park) drive the car, stick it in neutral, turn the engine off, then try and go round a corner....
Think you'll not want to disconnect the pump after that.
Alternatiely replace the rack with a non PAS one and flog the PAS kit?
Think you'll not want to disconnect the pump after that.
Alternatiely replace the rack with a non PAS one and flog the PAS kit?
I disagree.... front end lightness is very much to do with aerodynamics. The car starts to lift at the front reducing the force acting on the tyres and the reduced grip is seen as lightness or like driving on a slippery surface.
Non-PAS cars also go light at speed so it is not a PAS related aspect. Not just restricted to Griffs either.
The real issue is at high speed, little things can start to have big effects such as the rake of the car, geometry settings, defective components, tyre pressures and other factors including driver input. Toe can be critical in this as it can improve turn in at the expence of stability. At low speed not necessarily a problem but at high speed it can be quite aggressive. Quite common for non PAS drivers to complain about the lightness of PAS cars because they over compensate for the different feel. It also works the other way as well with PAS owners complaining of a bit of understeer on non PAS cars as they forget to increase the steering force.
Non-PAS cars also go light at speed so it is not a PAS related aspect. Not just restricted to Griffs either.
The real issue is at high speed, little things can start to have big effects such as the rake of the car, geometry settings, defective components, tyre pressures and other factors including driver input. Toe can be critical in this as it can improve turn in at the expence of stability. At low speed not necessarily a problem but at high speed it can be quite aggressive. Quite common for non PAS drivers to complain about the lightness of PAS cars because they over compensate for the different feel. It also works the other way as well with PAS owners complaining of a bit of understeer on non PAS cars as they forget to increase the steering force.
Edited by shpub on Tuesday 13th February 09:41
Agree with SHPub totally.
If you have a light steering issue with PAS, when you remove the PAS you will also be removing the natural damping effect of the PAS (like dampers on a motorbike) and you will find high speeds even more unstable.
I put a PAS rack in my car last year and it totally transformed the car which was scary as f#ck compared to my previous non PAS Griff at high speeds. I think due to the hand built nature of these cars, its airodynamics is also effected from car to car my minor variants in body postion/trim on the chassis at the front end, I also think its the reason some cars suffer heat soak and others don't due to the air flow over the front of the car.
If you have a light steering issue with PAS, when you remove the PAS you will also be removing the natural damping effect of the PAS (like dampers on a motorbike) and you will find high speeds even more unstable.
I put a PAS rack in my car last year and it totally transformed the car which was scary as f#ck compared to my previous non PAS Griff at high speeds. I think due to the hand built nature of these cars, its airodynamics is also effected from car to car my minor variants in body postion/trim on the chassis at the front end, I also think its the reason some cars suffer heat soak and others don't due to the air flow over the front of the car.
burriana said:
...I don't want to spend a load of money uneccessarily, but the super light and jittery front end at speed is a definite concern.
Mine seems fine, but then its non PAS and only got 205/50 front tyres which make a bit nose down too. Felt good, remember following a yellow Ferrari once out of Bolton Abbey, but I got stuck behind a lorry/ van/ caravan/ tractor /milkfloat /insertrandomexcuse here and he disappeared into the distance
Would be interesting to compare, but car is rather in bits at the mo and shall be for about another two months
Got to say i think rover got there maths wrong somewhere,most japanese systems consume beetween 3 TO 6 horsepower and there generally over assisted,anyone ever drove an early accord will tell you,lets just say the feel is better suited to the american market.In saying that i will stick to my PAS system thanks.
The TVR is steering / parking is much easier than your recent Fiat model, my arms are only half the size they used to be 
Yes with PAS you can get the lock on a bit quicker ~ but a well set up car will more than outweigh any handling problems / benefits offerred by PAS/non racks. Suspect a lot of folks spout about PAS upgrade transforming their car when a simple tracking adjustment may have had similar effect.
Someone would pay you a fortune for your PAS setup ~ they always say its so the OH can drive
~ just negotiate an exchange, it should pay for some nice handling uogrades and you wont have the maintenance costs of rack rebuilds / leaks in the future....
Dave
Yes with PAS you can get the lock on a bit quicker ~ but a well set up car will more than outweigh any handling problems / benefits offerred by PAS/non racks. Suspect a lot of folks spout about PAS upgrade transforming their car when a simple tracking adjustment may have had similar effect.
Someone would pay you a fortune for your PAS setup ~ they always say its so the OH can drive
~ just negotiate an exchange, it should pay for some nice handling uogrades and you wont have the maintenance costs of rack rebuilds / leaks in the future.... Dave
RichardD said:
Felt good, remember following a yellow Ferrari once out of Bolton Abbey, but I got stuck behind a lorry/ van/ caravan/ tractor /milkfloat /insertrandomexcuse here and he disappeared into the distance
You would go and remind me what a fantastic car I used to have wouldn't you - God I miss that car!
shpub said:
Non-PAS cars also go light at speed so it is not a PAS related aspect. Not just restricted to Griffs either.
Now my non-PAS was fine at 150+. So... the general concensus seems to be to keep the PAS and find out what handling component needs adjusting to make it feel more planted at speed.
Just for the record, I'm not talking about track work here, purely high speed motorway (autobahn of course) and V.Max type driving.
I am loathed to put a splitter on as it just doesn't seem right somehow. I was talking to Seasider and he has an adjustable one fitted ... that he never needs to use ... so getting the handling set up must be possible without one.
Is there an obvious check list of what to start checking / sorting out first without resorting to £800 worth of new dampers or similar!
Thanks for all the info and suggestions so far
Anyone know the answer to my earlier question - can you have the PAS made heavier?
The effort delivered by a PAS system is determined by the stiffness of the torsion bar inside the metering head of the rack.
You turn the wheel, this twists the bar which is directly connected to the pinion, but along its length a rotary valve block is attached, which the more the bar twists opens the ports more to the assist pistons.
To change the assistance of the rack the stiffness of this bar needs to change, shorten it or increase its diameter to stiffen it and reduce the level of assistance
Simple as that
Matt
You turn the wheel, this twists the bar which is directly connected to the pinion, but along its length a rotary valve block is attached, which the more the bar twists opens the ports more to the assist pistons.
To change the assistance of the rack the stiffness of this bar needs to change, shorten it or increase its diameter to stiffen it and reduce the level of assistance
Simple as that
Matt
In answer to your question over on the darker side:
AFIK, chassis mounts are all the same, so rack is interchangeable. The track rods & steering linkage are different, hence the suggestion of an exchange with somebody wishing to the upgrade ~ they will have everything you need ~ whilst you have everything they need and you will get lots of beer tokens
Dave
AFIK, chassis mounts are all the same, so rack is interchangeable. The track rods & steering linkage are different, hence the suggestion of an exchange with somebody wishing to the upgrade ~ they will have everything you need ~ whilst you have everything they need
and you will get lots of beer tokens Dave
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