Finally i installed a turbo boost gauge just to monitor the problem of my Turbo's.

Now after checking my turbos and vacums and the gate between the 1st and 2nd turbo all looks ok and working, but when i press on the padel ther 1st turbo will open with a boost of 0.7 bar and at 5,000 RPM to 7,000RPM the boost will go down to 0.4Bar or 0.3 Bar.

My questions are:
1- IS that drop due to that the 2nd turbo is not working at all??
2- or is it working, but i need to boost it up a little bit?
3- or is it another problem??

 

Mm... you might wanna try the stickies . It might be alot of things pinched vaccum hose , hose came off or even a actuator/solenoid not working properly . Depending on the year of the car .. doing the vaccum hoses seems like a good idea ... but a headache to do .

 

check the lines from the pressure tank nearest the charge pipe, my check valve fell apart and was expierencing the same issue... super glue *rock*

 

1) The 2nd turbo is working, by my definition. Any boost at 4500rpm+ is successfully running in parallel mode. Do you get a slight dip at 4500, then .7bar again before it starts going down?
2) No, do not attempt to boost it up - the system should produce .7bar (10psi or very close) - if it is not, there is a solenoid/vacuum hose/engine airflow problem. Fix the problem, get the boost back - the stock turbo control system requires no adjustment when working properly.
3) One possibility is an exhaust restriction - a bad cat or precat. This will result in decreasing boost with increasing rpm. What exhaust parts are you running?

 

You might be right on the 3rd answer, becaus eim running a stock downpipe which ofcourse have the cat on it!! but would it make that effect???

 

Yes, it can. The stock precat and cat can begin to break down, and once the exhaust flow reaches a certain level the restriction slows the airflow over the turbines. That reduces the boost created by the compressors. Since the airflow requirements go up with rpm and boost, the restriction causes the boost to steadily decline as the rpms increase.

If you have the stock cat, I suggest keeping that and remove only the precat. Or gutting the precat (I don't know how hard it is to get aftermarket parts in SA). I'm told that you should remove it, shake it, and if stuff falls out either end, you know the element inside is breaking down and clogging.

Dave

 

i agree. it sounds like a clogged cat to me also. i had what sounds like a similar problem a while back.

the general recommendation is to run a downpipe with either a stock cat or a high flow cat and control boost to 10 psi.

 

It just occurred to me: is your car a US-Spec? Because the catalytic downpipe (US pre-cat) wasn't included on most non-US models. If so, then you're looking at a clogged main cat. In US cars, the precat fails more often than the main cat, but both could be the cause.

Just remember, if you take it to a shop and they suggest making it a straight-through exhaust, don't do it. You really should have at least one catalytic element to avoid boost level problems and I prefer keep the noise and emissions stench to a reasonable level.

Dave

 

Mine is a US Spec. actually the first owner bought it from the state.

I guess you guys are right on that, because my mechanic assured me that he have checked all lines and vacums even the door between the 1st and 2nd turbo it was not working and he fixed it.

Beside and i forgot to mention that the second turbo when we were checking this problem was having an oil leak and luckly one of my friend who has an RX-7 gave me his Original TT set as he has an extra with the engine he bought from the junk yard, so i replaced that leaking turbo and we checked and fixed as i said the vacums and others. The car improved a little bit on the second as previousley it was not having any presure at all.

 

Jed, yea def. get that downpipe as we discussed earlier. Whether it's a problem now or not, it can and prob will become a problem soon. The stock precat (located in the stock downpipe) is notorious for clogging over time. I'd only imagine the veyr hot weather in Saudi only makes such things worse. Lemme know if you need help w/ getting the DP.

 

Thanks man i will diifenetly let you know...