MclarenF1

iTrader: (1)

So yesterday I bought a '93 touring auto. It felt like it was boosting low, so today I bought a gauge and did some boost testing. At WOT in L, there is no boost until about 3000rpm, where it starts at 5-6 psi, and then builds to 7.5-8.5 psi up until about 4500rpm, when the secondary turbo is supposed to come online. At that rpm, the boost drops a few psi, and then only builds up to 5psi up until redline. The motor runs perfectly fine, although it only pulls 13 Hg of vacuum when stationary in drive.

And sometimes under WOT from 4500 to redline, a large amount of blue smoke come out of the exhaust. This also happens when I rev it to around 6000rpms in neutral 2 or 3 revs in a row.

According to the previous owner, the car still has both cats (working on getting a downpipe as we speak, hesitant on getting rid of the main cause I don't want to cause overboost), and a catback exhaust (motoria?) that is really quiet, even though I can fit my fist in the muffler.

So my guess is that there is an oil seal on the secondary turbo that is broken, causing oil to get into the engine, creating smoke at high rpms, and that the turbos might need to be replaced.

So my plan of action is to:
- quit driving it
- replace all the vacuum hoses with silicon ones
- install a downpipe
- check all the solenoids and control valves
- replace turbos (if needed)


Does anyone have any useful advice or suggestions?

Aaron Cake

iTrader: (1)

Sounds like a broken, worn out set of turbos. The primary is likely totally dead and the secondary is on it's way out.

It's not unusual for FDs to go through a set of turbos every 50K.

MclarenF1

iTrader: (1)

Yeah, I read somewhere that they are considered to be a consumable part. At now I have something to help me get acquainted with the motor . I'm just trying to decide on which set of turbos I want to get.

dgeesaman

iTrader: (7)

Turbos that smoke (bad seals) are usually quite capable of making 10psi. I expect the low boost is due to another reason. So if the smoke is reasonable you should plan on buying a new set but it's not urgent.

More immediately you should investigate for boost leaks. Start with the diagonal crossover pipe that runs overtop the belts and take off the rubber couplers at each end of it. Inspect the couplers carefully off the car and look for cracks/tears that may open up once pressurized. You will probably find your problem there.

If that's ok, check the other couplers similarly, removing the metal shroud if present.

If that's ok, poke around under the pressure chamber that's adjacent to the crossover pipe and look for loose hoses or broken check valves.

After all that and new turbos, if you still aren't getting good boost only then would I dive into hoses and solenoids.

Dave

MclarenF1

iTrader: (1)

Ok, so today I started checking under the hood. I found oil deposits where the crossover and the y-pipe meet up, along with some oil in other areas. Attached are some pictures.

On another note, I vented the factory BOV to the atmosphere. Being my first turbo car, that "pshhhh" never gets old

dgeesaman

iTrader: (7)

You're going to have oil sprayed all over that side of your engine bay.

MclarenF1

iTrader: (1)

Even if I throw a filter on it?

dgeesaman

iTrader: (7)

That'll slow it down, but it might not keep things clean. The air goes rushing out with gusto.

I've never tried it because I think the concept is pointless.

MclarenF1

iTrader: (1)

yeah, it's not as loud as I thought it would be with the hood down, so I'm going to put it back on.

I took a look down over by the actuators to see if the hoses were switched and they weren't, so that's not the issue. I'm fairly certain it's the Y-pipe and crossover coupler that is causing the issue, because there is oil deposits all over it and the y-pipe. So next week I'm going to order an Efini y-pipe, downpipe, and then later down the road a new set of turbos.

MclarenF1

iTrader: (1)

Ok, so I did some more boost testing tonight. When poking around the pressure chamber, I found that the check valve between the pressure chamber and the y-pipe was in has separated. I krazy glued glued it back together as sort of a band-aid until I get a new one. Hasn't broken yet. Anyone know where I can get some new ones?

Now, onto the results of the boost testing. The first test resulted in a good 8-9psi boost up until 4000-4500rpm, when the boost drops down to 3-4 psi, and then pitters off to 0-1psi at about 7000rpm.

In the second test, I unplugged the wastegate and turbo pre-control connectors. This resulted in 5.5-6psi up until about 4000-4500rpm, where the boost dropped to about 3psi.

In the final test, I switched the wastegate and pre-control connectors. This resulted in 8-8.5 psi of boost up until 4000-4500, where it drops to about 3-4psi, pittering off to 0-1 psi at 7000rpm.

At engine speeds over 4500, the car blows quite a bit of blue smoke out of the tailpipe. In neutral, I cannot not get it to build boost at all under WOT. It just blows a cloud of blue smoke when revved to 6500-7000.

I know I have a boost leak, but why the secondary turbo is not boosting like it should is puzzling. Any ideas?

In the mean time, I have ordered a downpipe, an Efini Y-pipe/crossover and S-pipe, and I am currently putting some money aside for new turbos.