Stock Boost

Started by blitz · Nov 28, 2006 · 14postsSMF 2010–26

blitzNov 28, 2006, 4:04 am · #1

Hi guys, just wondering about the stock boost on CA18ET. my boost gauge max at 500 mmHg, which is converted to 9.67 psi. I can get only get about 450 mmHg on WOT which is equal to 8.7 psi. most thread said that the stock T2 w/ factory setup is @ ~6 psi. So what is the correct number? I have T2 w/ stock wastegate actuator and no intercooler (stock setup). the last time I got an oil change the mech said I have a leaky turbo @ exhaust side. (but that's not an issue for now). My car is 1985 turbo S12, canadian model.

So, what exasctly is the stock boost pressure on CA18ET?

KeithNov 28, 2006, 2:52 pm · #2

blitzSo, what exasctly is the stock boost pressure on CA18ET?

Stock boost on a '84 US model is 4psi, with stock exhaust, including cat, and bone stock everything else.....although March '84 Motor Trend says "max boost is 7psi @ 2300rpms"
I read 4 somewhere...maybe the owners manual....because I remember it says if your gauge went all the way to +5 to shut off the engine........and when mine was bone stock, it was just under +5 on the stock gauge.

blitzNov 28, 2006, 5:23 pm · #3

thanks keith. it just weird since I converted my 5 mmHg to psi which = 9.67 psi on the net (all other website has the same numbers). that is way over what I think stock is. still waiting for asnwer from canadian members or members with metric (non US/imperial) measurement/gauge on their car.

NamelessNov 28, 2006, 6:21 pm · #4

blitzthanks keith. it just weird since I converted my 5 mmHg to psi which = 9.67 psi on the net (all other website has the same numbers). that is way over what I think stock is. still waiting for asnwer from canadian members or members with metric (non US/imperial) measurement/gauge on their car.

Do you have have an aftermarket exhaust? That will raise boost some, and on some turbos may also cause boost creep.

IndecisiveNov 28, 2006, 8:40 pm · #5

on MY stock system, I got an 8psi spike, and it would level off at 6 or 5psi.

This was on a stock canadian MK.II turbo.

and keith, if you're saying you're at 4psi based on the stock gauge cause it was just under 5+ then that's wrong. The stock boost gauge is NOT in psi. it's not even in in.hg or bar. it's some odd unit that I can't remember off the top of my head.

at full boost, the stock boost gauge should only go up until the end of the first bar.

The reason the manual says to not run the car if you go over 5+ is because that means that you are way over boosting. It means that the wastegate isn't opening properly, and the pop up valve is obstructed and not functioning.

The stock gauge only goes to about 10psi, so it's a bad indicator of boost.

BOSSMANNov 28, 2006, 8:44 pm · #6

blitzthanks keith. it just weird since I converted my 5 mmHg to psi which = 9.67 psi on the net (all other website has the same numbers). that is way over what I think stock is. still waiting for asnwer from canadian members or members with metric (non US/imperial) measurement/gauge on their car.

Stock boost is 7 PSI. Your conversion is correct but the maximum number printed on the gauge does not mean "5 mmHg" is your maximum boost. Back in the 80's the US government put in a law to have the maximum speedometer reading on any new car to 80 MPH. Their idea is to stop people from speeding by not letting people know how fast their car can go. So even-though they are capable of doing 150 MPH top speed, all the Ferrari, Lamborghini and Mercedes had 80 MPH gauge. Oh, another thing is that your car will not top out at the maximum speed as indicated on the speedodometer panel.

KeithNov 28, 2006, 9:57 pm · #7

IndecisiveThe stock boost gauge is NOT in psi. it's not even in in.hg or bar. it's some odd unit that I can't remember off the top of my head.

Wtf ....see after all these years, I thought the stock gauge was in psi.

blitzNov 28, 2006, 11:06 pm · #8

Indecisiveon MY stock system, I got an 8psi spike, and it would level off at 6 or 5psi.

This was on a stock canadian MK.II turbo.

and keith, if you're saying you're at 4psi based on the stock gauge cause it was just under 5+ then that's wrong. The stock boost gauge is NOT in psi. it's not even in in.hg or bar. it's some odd unit that I can't remember off the top of my head.

at full boost, the stock boost gauge should only go up until the end of the first bar.

The reason the manual says to not run the car if you go over 5+ is because that means that you are way over boosting. It means that the wastegate isn't opening properly, and the pop up valve is obstructed and not functioning.

The stock gauge only goes to about 10psi, so it's a bad indicator of boost.

stock boost gauge is in mmHg

are u using aftermarket gauges? my stock boost gauge says: 5 x 100mmHg which is equal to 9.67, almost 10 psi. I can go almost full on that gauge on WOT in 5th gear, my boost indicator will be somewhere in the middle of the 2nd bar, almost touching the 5# on the gauge. my exhaust got some leaks at the muffler. my wastegate still works, I can moved the actuator arm by hand, although it's hard to do so.

BOSSMANStock boost is 7 PSI. Your conversion is correct but the maximum number printed on the gauge does not mean "5 mmHg" is your maximum boost. Back in the 80's the US government put in a law to have the maximum speedometer reading on any new car to 80 MPH. Their idea is to stop people from speeding by not letting people know how fast their car can go. So even-though they are capable of doing 150 MPH top speed, all the Ferrari, Lamborghini and Mercedes had 80 MPH gauge. Oh, another thing is that your car will not top out at the maximum speed as indicated on the speedodometer panel.

thanks bossman for the stock boost number. although that policy was a little weird... what is the top speed of the S12? the fastest I've been is 105 mph/170~ish kph. I know the speedo goes up to 125 mph/200kph

well... time to get a decent 2nd hand boost gauge

NamelessNov 28, 2006, 11:19 pm · #9

Thats the best thing to do, sotck boost guages are pretty much useless.

IndecisiveNov 29, 2006, 12:04 am · #10

you shouldn't hit that high in stock form.

There may be some issue with your wastegate. it should only go to the beginning of the 2nd bar, but not further.

as for top speed, I THINK I read it was 132mph...not sure though.

KeithNov 29, 2006, 12:09 am · #11

Indecisiveas for top speed, I THINK I read it was 132mph...not sure though.

That sounds about right....give or take. I got mine a little ways past the 125 mark a few times back in the day

BOSSMANNov 29, 2006, 8:21 pm · #12

KeithWtf ....see after all these years, I thought the stock gauge was in psi.

The unit of measurement for boost pressure is in PSI for US model, Indy is only referring to the Canadian models which use metric units, in short, maximum boost for US and Canadian is the same but one is spoken in English and the other in French.

KeithThat sounds about right....give or take. I got mine a little ways past the 125 mark a few times back in the day

I managed to hit 190 Kph (118 mph) with headlights on and the car fully loaded with 4 passenger and a trunk full of luggage. It is true that your top speed will be lower with the headlights up.

EternalSwapNov 30, 2006, 3:39 am · #13

I thought my guage only goes to 5PSI?

s-chassis_onlyNov 15, 2010, 8:39 pm · #14

so stock boost is roughly 8-9 psi then in stock form or a little less? so i can test to see if my turbo setup on my s12 that i just bought is still good or if i should swap on my sr t25