Low turbo boost

ekaftan · Unread post by **ekaftan** » 31 Jan 2009, 02:55

I just today installed a turbo boost gauge to my TurboCT (same engine as activa, normal VSX suspension) and I've never been able to get it to read over 5psi.

Somethings wrong, right? I've read it should read almost 9psi. Engine feels powerful, but not neck breaking...

No engine codes, all hoses connected. Any pointers where I should start looking?

Thanks...

XantiaMan · Unread post by **XantiaMan** » 31 Jan 2009, 08:13

What gear are you doing it in? Should be 4th or 5th gear. Boost modulates, wont sit at close to 9psi until higher revs as the ECU tries to flatten the torque curve and smooth the delivery.

ekaftan · Unread post by **ekaftan** » 31 Jan 2009, 12:54

XantiaMan583 wrote:What gear are you doing it in? Should be 4th or 5th gear. Boost modulates, wont sit at close to 9psi until higher revs as the ECU tries to flatten the torque curve and smooth the delivery.

I did it in third gear on a city street.... I will try to do it in a longer road and check....

ekaftan · Unread post by **ekaftan** » 31 Jan 2009, 23:18

ekaftan wrote:
XantiaMan583 wrote:What gear are you doing it in? Should be 4th or 5th gear. Boost modulates, wont sit at close to 9psi until higher revs as the ECU tries to flatten the torque curve and smooth the delivery.
I did it in third gear on a city street.... I will try to do it in a longer road and check....

I changed the gauge for another one (shop vaccumm/pressure) and its confirmed... I have low boost.

At idle I have 14 of vacuum (gauge says 21 is normal, but I assume a turbo car has less idle vacuum.

Then if I floor it in any gear, boost goes up smoothly until 5.5psi then holds that until around 5500 rpm then drops like a rock.

Maybe I have a different engine/ecu? This is a 97 car, in 1997 the best fuel was 93 octane in Chile.

XantiaMan · Unread post by **XantiaMan** » 01 Feb 2009, 15:16

I dont think they changed the amount of boost from age to age.

Next check, disable the boost control valve by taking the hoses off, leave the multiplug on. Join the 2 pieces together with a bit of copper tube, and then test. If boost remains the same as before, and 5.5psi sounds like actuator only pressure, then it points to a faulty valve.

If it drops even more, you could have a loose wastegate/actuator, which is common with age.

Boost build up at low revs is a good indication of whats going on, you should see boost building from 1500rpm and i would expect to see 5.5psi no later than 2000rpm.

ekaftan · Unread post by **ekaftan** » 02 Feb 2009, 23:04

XantiaMan583 wrote:I dont think they changed the amount of boost from age to age.

Next check, disable the boost control valve by taking the hoses off, leave the multiplug on. Join the 2 pieces together with a bit of copper tube, and then test. If boost remains the same as before, and 5.5psi sounds like actuator only pressure, then it points to a faulty valve.

If it drops even more, you could have a loose wastegate/actuator, which is common with age.

Boost build up at low revs is a good indication of whats going on, you should see boost building from 1500rpm and i would expect to see 5.5psi no later than 2000rpm.

Things I tested today:

-Hose from the manifold to the valve connected directly to the wastegate, git 5.5 psi
-Hose from the manifold blocked, got 5.5 psi
-Hose from the manifold to a manual wastegate valve bought off ebay, connected per the instructions, got 5.5 psi no matter what I did...
-Intentional small leak in the intake, 3psi and car run like crap (so I guess I dont have any leaks)

I am now running the car with the manual valve completly dialed in. I also only get 5.5psi, but it starts earlier and does not drop off after 5000rpm.

My diagnosis is that the wastegate is not closing completly. I got under the car to check. Everything looks good, except the valve is covered with oil. It was too hot to try and move it by hand though...

XantiaMan · Unread post by **XantiaMan** » 03 Feb 2009, 08:11

Did you have the manual valve fitted the correct way round? Its very easy to have it the wrong way!

When your underneath the car, slacken off the lock-nut first, needs plenty of WD40. The arm should be tight. I find using compressed air is a good way of testing the actuator operation and seeing that the wastegate is not seized.

If there is any sign of it being loose, there is your problem.

However i would also check all your boost hoses and the condition of the intercooler. It has plastic ends and if its ever had a minor shunt in the past, could have cracked the ends and no amount of tweaking will get the boost where it should be.

ekaftan · Unread post by **ekaftan** » 03 Feb 2009, 13:05

XantiaMan583 wrote:Did you have the manual valve fitted the correct way round? Its very easy to have it the wrong way!

When your underneath the car, slacken off the lock-nut first, needs plenty of WD40. The arm should be tight. I find using compressed air is a good way of testing the actuator operation and seeing that the wastegate is not seized.

If there is any sign of it being loose, there is your problem.

However i would also check all your boost hoses and the condition of the intercooler. It has plastic ends and if its ever had a minor shunt in the past, could have cracked the ends and no amount of tweaking will get the boost where it should be.

Will check the intercooler. The car did have a minor shunt as you said...

But, what locknut? I only saw a circlip.

XantiaMan · Unread post by **XantiaMan** » 03 Feb 2009, 20:49

ekaftan wrote:
XantiaMan583 wrote:Did you have the manual valve fitted the correct way round? Its very easy to have it the wrong way!

When your underneath the car, slacken off the lock-nut first, needs plenty of WD40. The arm should be tight. I find using compressed air is a good way of testing the actuator operation and seeing that the wastegate is not seized.

If there is any sign of it being loose, there is your problem.

However i would also check all your boost hoses and the condition of the intercooler. It has plastic ends and if its ever had a minor shunt in the past, could have cracked the ends and no amount of tweaking will get the boost where it should be.
Will check the intercooler. The car did have a minor shunt as you said...

But, what locknut? I only saw a circlip.

The circlip is at the end of the rod, on the wastegate, the actuator arm is threaded and locked in place, it may be quite rusty...

ekaftan · Unread post by **ekaftan** » 05 Feb 2009, 03:08

XantiaMan583 wrote:I dont think they changed the amount of boost from age to age.

Next check, disable the boost control valve by taking the hoses off, leave the multiplug on. Join the 2 pieces together with a bit of copper tube, and then test. If boost remains the same as before, and 5.5psi sounds like actuator only pressure, then it points to a faulty valve.

If it drops even more, you could have a loose wastegate/actuator, which is common with age.

Boost build up at low revs is a good indication of whats going on, you should see boost building from 1500rpm and i would expect to see 5.5psi no later than 2000rpm.

Which way does this wastegate work? I've been reading that there are two types: the ones that drop boost as you apply pressure to them and the ones that increase boost when you apply pressure to them.

XantiaMan · Unread post by **XantiaMan** » 05 Feb 2009, 07:11

ekaftan wrote:
XantiaMan583 wrote:I dont think they changed the amount of boost from age to age.

Next check, disable the boost control valve by taking the hoses off, leave the multiplug on. Join the 2 pieces together with a bit of copper tube, and then test. If boost remains the same as before, and 5.5psi sounds like actuator only pressure, then it points to a faulty valve.

If it drops even more, you could have a loose wastegate/actuator, which is common with age.

Boost build up at low revs is a good indication of whats going on, you should see boost building from 1500rpm and i would expect to see 5.5psi no later than 2000rpm.
Which way does this wastegate work? I've been reading that there are two types: the ones that drop boost as you apply pressure to them and the ones that increase boost when you apply pressure to them.

The actuator opens when pressure is applied. Boost builds and as it does so, pressure is gradually applied to the actuator, when it overcomes the spring pressure thats when it starts to open quickly, up to that point it starts to creep before the pre-set is reached but thats another subject...

ekaftan · Unread post by **ekaftan** » 06 Feb 2009, 21:50

Still debugging....

The wastegate diaphragm is ok. It holds 1BAR from a large syringe with out problem, but the arm does not move. Its stuck...

Tomorrow I will start applying WD40 and hitting with a small hammer and try to unstick it...

ekaftan · Unread post by **ekaftan** » 07 Feb 2009, 18:17

ekaftan wrote:Still debugging....

The wastegate diaphragm is ok. It holds 1BAR from a large syringe with out problem, but the arm does not move. Its stuck...

Tomorrow I will start applying WD40 and hitting with a small hammer and try to unstick it...

I got under the car in a pit. The arm is ok. Is does move and has full travel. I just could not see it ok from above.

It starts to move around 3psi and has full travel at 5psi.

I also now think the intercooler is leaky. I completly blocked the air filter intake, got the hose from the turbo to the intercooler to colapse but the car kept on running like nothing happened, so air must be getting in...

Brigsygtt · Unread post by **Brigsygtt** » 12 Feb 2009, 14:41

Id be pressurizing the boost circuit up with a compressor to check for leaks.

Hook a gauge up & bang 20lb into it, if there's any leaks you will find them
easily.

Im also assuming your not using a max power style boost gauge, some of the cheapo ones can be very inaccurate.

ekaftan · Unread post by **ekaftan** » 12 Feb 2009, 14:46

Brigsygtt wrote:Id be pressurizing the boost circuit up with a compressor to check for leaks.

Hook a gauge up & bang 20lb into it, if there's any leaks you will find them
easily.

Im also assuming your not using a max power style boost gauge, some of the cheapo ones can be very inaccurate.

I did buy a cheapo gauge and it was horrible. I am now using an expensive shop gauge I bought ages ago to check for vacumm leaks on carb engines. (its 4 inches in diameter and reads +-1bar)

I tried to pressurize the boost circuit. It leaks so much I never got the pressure up with my smalish compressor to pinpoint the leak, thats why I am taking the intercooler out. It must have a huge crack.