Help! Where's my boost?

[billjam]

I posted this boost log for my K27 in another thread recently feeling quite happy that I had managed to get more driveability and earlier onset of boost compared to the old 3LDZ turbo I replaced.


As well as the K27, the engine has SC cams, head ports cleaned up, B6 intercooler, Euro headers and what looks to be a free-flow muffler (no brand).
The fuel system is still CIS with a modified fuel head (by IA), a Leask WUR and RPM solenoid.

In the "stock 3ldz upgrade" thread, Rarly and others thought I should be getting more boost earlier. Rarly suggested a boost leak might be the cause.
Since then, I have

• retightened inlet manifold nuts (new spacers fitted recently)
• checked all intercooler connections
• checked BOV is not stuck open
• checked wastegate is not stuck open

In between some of these activities I repeated the second gear run and each time I logged virtually the same results.
I've now run out of ideas and things to check, so if you have any suggestions, I am all ears ...

[scmguru]

Bill,

I had a similar problem, stock 86 930.

Replaced all the o-rings/seals from the turbo -> intercooler -> intake/throttle body.

I used o-ring safe (non-acidic) lube on all the new rings and the problem was gone.

[WERK I]

What is your wastegate boost threshold?

[billjam]

Originally Posted by WERK-I

What is your wastegate boost threshold?

Dave, I assumed 0.8 bar because that's where the boost levels out.
However I am not certain because I have a non-standard WG and I haven't been able to get any info about it. I picked it up on eBay a while back with some other used parts and when my OEM diaphragm split, I replaced the old WG with this one.



I have read of others pressure testing their engines to find leaks, but I just don't see this as being so simple. Although I guess it really only comes down to blocking the inlet (at top of CIS), the exhaust pipe and the oil tank - correct?

[billjam]

Originally Posted by scmguru

Bill,

I had a similar problem, stock 86 930.
Replaced all the o-rings/seals from the turbo -> intercooler -> intake/throttle body.
I used o-ring safe (non-acidic) lube on all the new rings and the problem was gone.

I have fitted new seals recently but I have rechecked them and they still look OK. They are a real snug fit with the IC as well, although I can't actually tell if they are leaking without pressurising the system somehow.

Despite the efforts I have gone to to check all connections and the manifold, something happened on the weekend that makes me think there's an air leak somewhere.
Went for a drive in the country on Sunday and the A/C died so wife suggested opening the roof. With roof open, every time I started to get any boost, I could hear a hissing sound coming from out the back that actually sounded quite cool, but may be an air leak.
I very rarely open the roof so I don't recall hearing this sound before so it may just be the sound of more air getting pushed through the IC.

However, it just seems odd to me that if there was an air leak somewhere that was not allowing earlier boost (when pressures are relatively low), it must be passing bucketloads of air at higher boost. I would expect this to seriously upset my AFRs under boost. I know they go low, but are they normal?

I'd be interested in some comments on the following logs.





For these 3rd and 4th gear runs, I changed the boost connection from a tee in the IC to wastegate hose to the throttle body to BOV hose. This shows vacuum readings as well as boost, but I suspect that it gives a lower boost reading than the IC connection.

Also, for the runs in higher gears, it seems that boost does actually come in at reasonably low RPMs. Unfortunately I couldn't wind it up too much (traffic), but I think it is clear that comparing the 2nd gear log in the first thread, boost definitely comes in at much lower revs in the higher gears. Is this closer to what I should be expecting?

[WERK I]

Originally Posted by billjam

.............................
Went for a drive in the country on Sunday and the A/C died so wife suggested opening the roof. With roof open, every time I started to get any boost, I could hear a hissing sound coming from out the back that actually sounded quite cool, but may be an air leak...........................

Bill,
That hissing sound you hear is normal for turbo cars. That's the turbocharger sucking your wallet dry........... It's hissing because you changed your air cleaner to the style used by Rarly8.
I really don't think you have a leak anywhere.....your AFR's would be off the chart. I would focus on areas involving ignition timing and back pressure of the muffler.

btw, does your wastegate ever open? It's looks like a Tial clone.....trying to remember what the yellow spring represents in lbs. It doesn't look like an .8 bar spring....the chart indicates your boost never gets above .6-.7 bar.

[beepbeep]

Boost curve looks pretty normal to me. Bigger turbo and bigger intake ports aren't exactly going to improve boost threshold. Neither are cams with overlap and sub 10:1 AFR's (!). That car is just blowing petrol out the tailpipe at boost.

If you had EFI you could dump ignition before boost onset to shorten the spool-up somewhat (but that would also lower the torque before boost).

Frankly, I believe people are sometimes expecting too much from their hardware. Your engine displays fairly typical ROW 930 boost curve.

[Shadetree930]

Bill,

I had a similar problem, stock 86 930. Replaced all the o-rings/seals from the turbo, intercoole, intake/throttle body. I used o-ring safe (non-acidic) lube on all the new rings and the problem was gone.

What/where can I get acid free lube?

[RarlyL8]

As Dave stated, the hiss is now audible due to the Eagle Day air cleaner assembly.
I know the 11.11 is more sluggish than the UMW 7200 but to not hit 0.85bar by 5000rpm is not right. It should be all in by at least 3500-3700 on the warmest of days.

[billjam]

Originally Posted by beepbeep

Boost curve looks pretty normal to me. Bigger turbo and bigger intake ports aren't exactly going to improve boost threshold. Neither are cams with overlap and sub 10:1 AFR's (!). That car is just blowing petrol out the tailpipe at boost.

If you had EFI you could dump ignition before boost onset to shorten the spool-up somewhat (but that would also lower the torque before boost).

Frankly, I believe people are sometimes expecting too much from their hardware. Your engine displays fairly typical ROW 930 boost curve.

Goran, actually, I am quite happy with the way the car performs. It is so much better than it was in standard form. I am not aiming for maximum power but reasonable driveability with good power because it is a daily city driver AND a weekend warrior.
Your point regarding low AFRs under boost is noted. Forget EFI (for now) - what is the easiest way to address this problem (without involving my right foot)?
I am quite happy to play with my fuel pressures, adjustable WUR and fuel solenoid valve if the answer lies there.
It also makes sense to me that if the air path into the heads is improved, less boost will be developed in getting the same amount of air into the heads.
Sort of like removing your finger from over the end of the garden hose - less pressure in the hose but more water flow.
Thanks for your time!

Originally Posted by RarlyL8

As Dave stated, the hiss is now audible due to the Eagle Day air cleaner assembly.
I know the 11.11 is more sluggish than the UMW 7200 but to not hit 0.85bar by 5000rpm is not right. It should be all in by at least 3500-3700 on the warmest of days.

I am so relieved that I don't have to spend any more time chasing down air leaks. The air cleaner theory makes sense because it is a new addition (which is why I never heard it before).
I will investigate the WG a little more deeply, even if I have to go back to my physics books and calculate its rating from the spring dimensions. I can't hear it lifting, but removing the WG muffler so I can hear it might be a good starting point for checking if it is lifting early.
With regard to the rate of boost development, I am finding that it is very different in 2nd, 3rd and 4th gears and not directly related to RPM. I guess inertia (lag) is going to have more effect in a short, quick 2nd gear run than a higher gear.
As far as the actual measurement of boost is concerned, I have also found that I get three entirely different readings at three different tapping points (at IC/WG hose, at throttle/BOV hose and at booster connection).
Where do you normally measure boost and in what gear?
Thanks for your input Brian.

[billjam]

Originally Posted by WERK-I

Bill,
That hissing sound you hear is normal for turbo cars. That's the turbocharger sucking your wallet dry........... It's hissing because you changed your air cleaner to the style used by Rarly8.
I really don't think you have a leak anywhere.....your AFR's would be off the chart. I would focus on areas involving ignition timing and back pressure of the muffler.

btw, does your wastegate ever open? It's looks like a Tial clone.....trying to remember what the yellow spring represents in lbs. It doesn't look like an .8 bar spring....the chart indicates your boost never gets above .6-.7 bar.

Yeah, right! I'm getting very familiar with that wallet sucking sound!
I am confident that ignition timing is OK. I rebuilt the dizzy a couple of months ago. It has new diaphragm unit and no thermo-valves or any other gizmos in the boost or vacuum lines. Timing is set to 26* at 4000 RPM.
When I last had the muffler off, it looked pretty open inside, but you can't really tell. It doesn't have a brand name either, which doesn't help.

In the log in the first thread, boost was going up to 0.8 bar in 2nd gear. The logs in the later thread (#5) are higher gears and lower revs. I ran out of space before I could build up more boost on those runs.

[boostfix]

Originally Posted by Shadetree930

What/where can I get acid free lube?

Dow 111 is a silicon grease that works well for O rings and for caliper rebuilds.
Check it out here:
http://www.waterfilters.net/ORing-Silicone-Lubricant_p_11-1127.html

[krasuskyp]

Originally Posted by RarlyL8

As Dave stated, the hiss is now audible due to the Eagle Day air cleaner assembly.

Very sorry for the threadjack Billjam - but - can either you or Brian PM / email me s8editor@s-cars.org about the details of your air cleaner install? Need to know which one, and more importantly what then to do with the mirad of vacuum hoses now that the airbox is gone. (Brian, this is what I'd tried to PM you on before and was asking you to email me on - as well as your rebuilt WUR source which I was hoping to tackle before I come south next month but I'm running out of time).

Tx in advance guys, much appreciated. Good luck to you Billjam on sorting out your issue.

Now back to your normally scheduled programming...

[billjam]

Originally Posted by krasuskyp

Very sorry for the threadjack Billjam - but - can either you or Brian PM / email me s8editor@s-cars.org about the details of your air cleaner install? Need to know which one, and more importantly what then to do with the mirad of vacuum hoses now that the airbox is gone. (Brian, this is what I'd tried to PM you on before and was asking you to email me on - as well as your rebuilt WUR source which I was hoping to tackle before I come south next month but I'm running out of time).

Tx in advance guys, much appreciated. Good luck to you Billjam on sorting out your issue.

Now back to your normally scheduled programming...

Paul,
What the hell, a bit of hijacking never did anyone any harm.
Don't mind at all really as a bump might get some response to my earlier Qs.

I just dug up some photos of aircleaner and plumbing. I have no idea what brand the cleaner is but it has a K&N filter. It is held in place by the same two M6 bolts that held the original cleaner.
Hose A is the original large breather hose that was connected to back side of filter housing.
Hose B is a new connecting hose from hose A to a new fitting E at the filter. A and B connected with a sleeve that was about 22mm OD from memory. I also supported the hoses at this connection to a bracket.
Hose C is from WUR. It originally went to filter housing. Now it goes to E.
Hose D is breather from turbo oil tank, also connected to E.
Fitting E is a 20mm copper elbow silver-soldered to a 20mm copper tee. There is a small (8mm?) branch welded on for the WUR hose. This fitting effectively brings all the various breather hoses together and connects then into the filter housing.

God, this looks messy - and I have chucked out heaps of plumbing already!

[sjf911]

For a 44/46mm Tial WG, a large yellow spring is 0.6 bar. A large red spring would be 0.8.

[RarlyL8]

Looks like you have an Eagle Day air cleaner. They sell for ~$300 and advertise in Pano and probably Excellence as well.
Paul I sent you an e-mail, did you not receive?