Lack Of Servo Asistance

[mos 1]

Hi

 

some of you may or may not remember a while back i posted about the problems i was having with brake servo assistance on the 2.1 s16 engine running throttle bodies that mattsav at qep built for me .

i had up to this point discounted the possibility of the engine itself not producing enough vacuum to give effective servo assistance to the brakes but after trying everything else, such as new piping, one way valves, rubber seals, both one and two takeoffs etc i still have not got to the bottom of it.

the only part i have not changed is the servo itself due to the cost of a new one and the shear pain in the backside they are to change

as a last resort before changing the servo i borrowed a vacuum gauge and measured the engine vacumm at idle on my s16. i got a reading of 180-200mmhg.

knowing bugger all about these things the only sensible thing i could think of was to take a reading on my skip brown 1.9s that runs carbs for a comparitive. i got a reading on this car of 280-300mmhg.

an increase of about 100mmhg over my 2.1 s16 or 33%

 

so my rather obvious question is 180-200mmhg too low a vacuum to create a decent suction on the servo to give decent servo assistance and has the s16 engine been the cause of my problems all along, or is this plenty and i am barking up the wrong tree (again!!!)

 

thanks

 

mark

[mos 1]

i have realised i have made a complete hash of this

as i am only reading off one cylinder rather than all 4 like you would normally do with a servo take off on a standard phelum and manifold

this would i imagine explain why the needle on the guage fluctuates wildly from about 15-20 inhg to 0

the only way i got a stable reading was to clamp the pipe somwhat by hand and thats how i got the reading i posted earlier.

guess i cant use a vacuum guage to measure the engines vacuum on a throttle boby/carb manifold with a takeoff only on one cylinder

[welshpug 1,657]

as its an S16 can you not refit the vacuum pump to the end of the cam? this will do away with the need for loads of pipes and you'll have a rock steady servo.

[mos 1]

as its an S16 can you not refit the vacuum pump to the end of the cam? this will do away with the need for loads of pipes and you'll have a rock steady servo.

 

i suppose i could but as its actually a mi 2.0ltr from a 405 and not an s16 306 i dont have all the vacuum pump bits and pieces as the 405s didnt have them.

in addition to this as i am running bodies the kms coil is mounted on a nice end plate between the two cams on the side of the head where the vac pump would sit and i am reluctant to move it if i can avoid it as i will only have to find a new home for it.

 

i have been doing my homework on the net about servos and i am becoming increasing convinced that it may well be a duff one and they can fail partially but before shelling out £100+ i wanted to double check it just wasnt a case of the engine not producing enough vacuum.

 

i may just bit the bullet and change the servo, anyone know where i can get one as euro car parts website says they are out of stock