Boost pressures

[V3 NGS]

Hi gang
could anyone tell me what the boost pressure is as standard?? I am running about 6psi boost, does that mean i have a standard pulley fitted?? But if i fitted a 15%, 17% or 19% what should the boost pressures be after????
cheers Nigel

[leeg87]

Hi gang
could anyone tell me what the boost pressure is as standard?? I am running about 6psi boost, does that mean i have a standard pulley fitted?? But if i fitted a 15%, 17% or 19% what should the boost pressures be after????
cheers Nigel

yes that means you have a standard pulley, peak boost with a stock pulley should be 8-9psi

JCW 11% ~ 13psi
15% ~ 15psi
17% ~ 17psi
19% ~ 19psi

this is not gospel and will depend on a whole lot of different things - headwork / manifold / exhaust / cat / decat / supercharger condition etc etc but as a rough guide the above is true

[V3 NGS]

could it be the by pass valve playing up.... how does it work exactly??? could i loose boost through the valve??? I do have a pulley fitted but i am only getting about 6 psi thanks again

[leeg87]

yo have a 17% pulley and are only boosting to 6psi? yes it could be the by-pass valve - it should be fully closed when under WOT, you can check it, its down the right hand side of the intercooler if your looking at the car. Could be leaking at the snoot boots etc. Get it checked out

[MartinSullivan]

As lee says it could be the snoot boots, I have a new set of GTT snoot boots looking for a new home if anyone wants them, they are designed to fit the interecooler much more snugly than the OEM ones.

It could also be the bypass valve, you can remove it and adjust the butterfly, plenty of post on mini2 about this.

[doogz__]

You guys run 19psi on standard internals, that were designed to take 6?

If you're loosing to much pressure, if you pop the bonnet, start the car, and get a mate to rev it a bit, you should be able to find the "leak" fairly easily i'd have thought.

Good luck with it.

[R32GTR]

You guys run 19psi on standard internals, that were designed to take 6?

If you're loosing to much pressure, if you pop the bonnet, start the car, and get a mate to rev it a bit, you should be able to find the "leak" fairly easily i'd have thought.

Good luck with it.

the standard internals are all forged, rods and crank and forged mhale pistons, the reason engines blow is people running them far too hot, its a fine balance if you can keep the engine cool enough you can run 19 psi, but you would probably need a high capacity front mount inter-cooler

[V3 NGS]

has anyone ever removed the s/c... is it an easy job ... i think i will need to take every thing off to find out where the problem is!!!!

[leeg87]

it isn't the easiest job in the world - radiator etc needs to come off. before you even think about that though trouble shoot the problems, any signs of a boost leak? how are you measuying boost? car feel slow?

[countdown]

removing the S/C isnt going to help..........theres no need to.


mine boosted 5-6psi (standard pulley) - it was a faulty bypass valve, very common problem. Removal is fairly easy, I would remove and check the condition and operation of it before going anywhere near removing the S/C. Also check the boost line from the fuel reg to to the intake manifold while your there. Also check the intercooler boots, i was losing 1 - 2 psi through them at one point as well. I dont think the boots are expensive, just replace them or use aftermarket ones.

[V3 NGS]

I have an update on the boost pressure
I have plugged in my machine to have a look at what is going on and the MAP sensor is telling me that at 6500rpm i have 27 psi of boost. can this be correct or is the sensor duff, when the engine is off the reading is 1 psi which i take as atmospheric pressure.
The reason i have been asking is i had the s on the dyno and with all themods i recon i should be running 250+ but heres the cruncher........ 167 at the wheels and 191.5 at the flywheel the barometric pressure at the time 994 mbar and the enviromental temp was 24.7 deg c......... there must be a problem but the engine is running sweet as a nut..... any ideas??????????????????????????????????????????

[leeg87]

I have an update on the boost pressure
I have plugged in my machine to have a look at what is going on and the MAP sensor is telling me that at 6500rpm i have 27 psi of boost. can this be correct or is the sensor duff, when the engine is off the reading is 1 psi which i take as atmospheric pressure.
The reason i have been asking is i had the s on the dyno and with all themods i recon i should be running 250+ but heres the cruncher........ 167 at the wheels and 191.5 at the flywheel the barometric pressure at the time 994 mbar and the enviromental temp was 24.7 deg c......... there must be a problem but the engine is running sweet as a nut..... any ideas??????????????????????????????????????????

take away atmospheric from that 27psi and that gives you roughly 12psi, if you are getting anything over 18psi your traction control light will come on and stay on.

With your mods maybe 250+ bhp is ambitious, with the addition of a cam + remap (and injectors if you still have 330's) then 250 might be achievable.

What intercooler do you have on? was the car dyno'd with the bonnet up or down? 24.7deg is quite a high ambient temp. and it wont be unlikely that your ECU pulled timing and started dumping in fuel if your IAT's got above 50degC. Did the RR map your Air fuel Ratio? got a print out?

[V3 NGS]

yes i do have a print out what would you need to now
0-4000 -- 13.8 to 13
4000 - 5000 --- 13 - 11.5
5000 - 6000 ---11.5 - 11.8
6000-7000 ---11.8 - 11
i have a unichip fitted .... he said that he could go a lot more on the fuel if needed so its not fuel ........... i have a GRS cooler fitted

[leeg87]

peak power at which rpm, rev limit rpm, does the graph 'dip' towards the end the climb back up?

was this done at wallace out of interest?

How much miles has your supercharger done? what year is your car? how long has the 17% been fitted?

[V3 NGS]

peak power at which rpm, rev limit rpm, does the graph 'dip' towards the end the climb back up?

was this done at wallace out of interest?

How much miles has your supercharger done? what year is your car? how long has the 17% been fitted?

max torque wheels 164.9 lbft @4059 rpm, rev limit power drops off at 6500 rpm, the graph does dip after 6500 rpm, yes the car was set up at wallace. miles 50,000 ish, 2003 mcs, well over 3 years the pulley has been fitted.