964 3.3 Turbo EFI Conversion using Syvecs (Life Racing) Engine Management

[Spenny_b]

Originally Posted by WERK I

Or, you may have an air leak between the suction end of the turbo sump pump and the turbo sump tank.

Hmm, possible. With further inspection I can see a slight oil weep coming from the aux pump area or possibly the rear cam seal in the air pump housing. It's very little, not even dripping, but maybe that -10AN fitting (a banjo using rubber lined sealing washers) is indeed something to investigate further?

Whichever way, it's getting dismantled before everything else goes back together. Tomorrow I'm hoping to pop into Think Auto and collect this weeks shopping list of plumbing items. I'm going to change that -10 from ally to steel I thing, so I can crank down a little harder without fear of shearing the fitting.

[Ken911]

every single time I've had oil anywhere in the intake it's been broken rings

[Spenny_b]

Originally Posted by Ken911

every single time I've had oil anywhere in the intake it's been broken rings

Oh t'riffic.

But...this is the first time I've seen oil puddled there; the intake pipe that feeds into the turbo has been out a few times and there's been no oil, it's also had a full week of running in the dyno cell. How likely is it that a ring would go now? (genuine question, not being contrary)

The cold compression numbers I did before Xmas were all very similar to each other (with the slight exception of one, when the battery was on it's last legs whilst spinning over then engine)

Not re-run a leakdown test since building the engine.

[Ken911]

hopefully they aren't broken. I just haven't been that lucky.

[Spenny_b]

Time for an update....

Many conversations and emails back and forth, and as always, I'm extremely grateful for having guys like Chris, Steve and Craig in "my corner", with sane, sage advice at the ready.

I borrowed a proper leakdown tester from Steve and Craig, a pukka Mac Tools item which is a known good unit (you may remember, I had a cheap and cheerful one that broke first time out, then borrowed another unit which was suspicious due to the gauge not zero'ing)

When hooked up with 100psi applied, each piston @ TDC of the compression stroke, I got the results I didn't want to see.

#1 = 11%
#2 = 2%
#3 = 3%
#4 = 18-19%
#5 = 2%
#6 = 6%

With the headers removed, I have the luxury of being able to feel for any air leaking through the exhaust valves on #1 and #4...very little. Also no immediate sign in the intake plenum....however....I can hear oil bubbling as well as a heavy exhausting or air through the main oil tank breather hose. So, that's pretty conclusive.

Time to stripdown and rebuild.

What's unclear at the moment is both the root cause and the condition of the cylinders.

It could be broken rings, but maybe also "just" a case of the rings not bedding in correctly.

During the running-in period on the dyno, we've been told that the manometer on the crankcase breather was reading well, no sign of blow-by. However, during the last day we did have electrical issues with 4 missing sparks on the 4-6 bank - perhaps this resulted in bore wash?

Det was constantly being monitored by Dave and his headset, none present (or more accurately, during the pulls, any hint of det meant we stopped and adjusted accordingly, as you do when tuning). I've also been told by another specialist, that with air-cooled engines, det is so noticeable ("sounding like a bag of spanners") that you can't miss it. I certainly havent heard any det when driving.

Overall, the engine still sounded good; even, smooth...all the usual signs, so that leads us to believe that we're maybe not looking at broken rings...maybe...who knows, this is just speculation until it's stripped.

Blow-by does also explain why the oil is looking so black and absolutely stinks of fuel/exhaust, although not necessarily why oil is sitting in the turbo intake - that appears to have been sucked up from the oil drip tank on the turbo. Why there was even oil in there, is another thing altogether, it should surely be pretty much empty all the time (less oil being fed into the GT35 than the K27, but the same capacity pump scavenging it)…is the aux pump knackered? It’ll all be checked.

Using a cheap (but not-so-cheerful) borescope, the pics I’ve got of the cylinder bores aren’t the best - limited focal length on this scope - again, best just to inspect once stripped, but I have a feeling that they’ll need redoing with Nikasil coating, if what we’re seeing is correct.

Currently, with being extremely busy at work, I've not made a lot of progress for the last week in terms of getting the drivetrain removed…too many late evening returns, feeling like groundhog day (in fact, the works Nissan slogan of “Eat Sleep Race Repeat” is apt…more like ”Eat Sleep Work Repeat”). All good fun, but not good for getting off the sofa in the evening.

The top side of the engine is disconnected with the exception of the fuel lines. The headers are still off, bumper removed, heat shields out. Need to drain the oil, remove the oil lines and everything else (clutch slave, power cables, transmission linkage, driveshafts, etc). I’m collecting the engine hoist and engine stand tomorrow morning; really hoping to have something to dismantle by end of play.

[WERK I]

^^^^ Man, that just sucks....
Sorry to hear of your blow-by issue. If there are broken rings, detonation may not be the culprit. Rings gaps too tight or ring land excessive play can quickly ruin rings. After following your build and seeing how absolutely thorough you've been, this is one for the books.
Were these cylinders replated? I could see a plating failure cause this problem.

Are you filtering the return oil from the turbocharger?

[Spenny_b]

Originally Posted by WERK I

^^^^ Man, that just sucks....
Sorry to hear of your blow-by issue. If there are broken rings, detonation may not be the culprit. Rings gaps too tight or ring land excessive play can quickly ruin rings. After following your build and seeing how absolutely thorough you've been, this is one for the books.

Cheers mate, yeah, does kinda suck...

...BUT....

....there may be a silver lining to this cloud [cue dramatic music and a dastardly "muh-hah-hah"]

Originally Posted by WERK I

Were these cylinders replated? I could see a plating failure cause this problem.

No, the cylinders were brand new 98mm LN Nickies with fire-rings channels machined into the top, so I can run Ni-Resist rings between cylinder and head.

Originally Posted by WERK I

Are you filtering the return oil from the turbocharger?

Yes, in fact the very last mod I did before we went to the dyno was to plumb-in a -8AN Mocal inline filter between the drip tank and the aux pump.

Oil drained, lines removed, WG's off, time for a cheese toastie and a cuppa, then driveshafts, throttle linkage, fuel lines.

I've retrieved the engine crane and the engine stand - no excuses now for not getting the lump out today.

[WERK I]

"Yes, in fact the very last mod I did before we went to the dyno was to plumb-in a -8AN Mocal inline filter between the drip tank and the aux pump."

************************************************** *****************
I always thought that a filtration system is more effective when it is plumbed on the pressure side of a pump, no?

[Spenny_b]

I don't know? Maybe that's the case and would then explain why I'm not seeing as much scavenging happening from the drip tank as I would expect?

I haven't got the finest filtration element in the filter, and my thinking was that putting it here would also then protect the pump from any detritus in the inbound oil.

It's easily removed, although plumbing it back into the exit side would require some -8 fittings to be swaged onto the existing rubber hose (not impossible by any stretch, just a job that needs to be remembered)

[Brainz]

I don't have a 930, but have 997 with aftermarket turbo. I had issues with a smoking turbo which I tracked down to two issues: 1) inadequate crankcase vacuum, and (maybe) 2) smallish turbo drain line. I fixed the AOS/PCV system first, which increased crankcase vaccum and not only helped pull the oil through the drainline (and hence eliminate the smoking), but also appears to have helped with blowby. Not sure if it's true, or why, but I've read that rings like a bit of crankcase vacuum to help with sealing. Also, in researching the smoking issue, on many turbo forums (not necessarily Porsche) the consensus was to have the biggest drain line/lowest restriction possible. -10 and -12 were often recommended. I switched to a -10 drain which is ~2x the cross section I had previously and it seems to work much better. Again, not a 930 expert, but I wouldn't think you'd want a filter or any other restrictions on the drain side.

Sent from my Nexus 6 using Tapatalk

[boosted79]

" Not sure if it's true, or why, but I've read that rings like a bit of crankcase vacuum to help with sealing."

Absolutely true. Early systems ran the breathers into the header collectors which helped evacuate the case to both reduce windage losses and improve ring seal. Belt driven vac pumps are now used to pull a vac on the case.

[Spenny_b]

Originally Posted by Brainz

....Also, in researching the smoking issue, on many turbo forums (not necessarily Porsche) the consensus was to have the biggest drain line/lowest restriction possible. -10 and -12 were often recommended. I switched to a -10 drain which is ~2x the cross section I had previously and it seems to work much better. Again, not a 930 expert, but I wouldn't think you'd want a filter or any other restrictions on the drain side.

Hi Brainz,

Sorry, my previous description perhaps wasn't the clearest; the turbo drain line I'm using is indeed a -10AN run, about 10" long, which runs from the turbo housing to the turbo drain (drip) tank. This tank has the capacity to hold perhaps just under a litre of oil, and has 2 further connections, both -8AN.

1) The first is a breather line, that runs back up to the air intake pipe. This line is about 2ft long with maybe 1-1.5ft of height difference (and is providing the path that the oil appears to have taken back into the turbo compressor intake)

2) The second -8 line is the one used by the auxiliary pump to pull the drained oil back from the drain tank to the main oil tank in the RH wing. Although it's a new line I've made, the original rigid line was of the same ID (but I'm unable to use it, as the turbo drain tank is one that I've fabricated, sits in a slightly different orientation and has different fittings). It follows the same path, so approx the same length but the only functional difference is that I have that inline oil filter midway along its length (which as WERK I suggested above, may not be ideal for suction strength).

Re crankcase vacuum, yup, in fact when I converted a previous engine (GM Vauxhall 2.0 XE "Red Top") from wet sump to dry sump, the dry sump pump was mounted externally to the engine and was belt driven off the crank pulley, and did indeed generate a significant vaccum, which had a secondary effect of adding a few hp. I expect that the internally mounted dry sump pump of the aircooled lumps to have the same effect w.r.t. vacuum.

[Brainz]

Thanks for the explanations, guys. I had not considered that the dry sump helps with the crankcase vacuum. I hope you get things sorted without any lengthy or expensive issues.

Sent from my Nexus 6 using Tapatalk

[boosted79]

That really s^&%$. After all of that work. It's unlikely that two bores would not seat when the others are fine? Was a leakdown done after assembly but before run in? That's a good thing to do just to give a base line.

[Spenny_b]

Originally Posted by boosted79

That really s^&%$. After all of that work. It's unlikely that two bores would not seat when the others are fine? Was a leakdown done after assembly but before run in? That's a good thing to do just to give a base line.

Yup, indeed I did. It was after I assembled the heads and had to re-lap the valves in (long story involving a supposedly reputed engine builder here in the UK...utter twat).

What I would say, is that I didn't use the same leakdown tester that I used last week (the Mac Tools one), it was a bit of a home built tester that used both spark plug holes (measured pressure of air in one, read %-age loss via the other). Although not 100% confident of the absolute numbers I got, they were at least consistent across all 6, at around 2-3% iirc.

Fear not guys, there WILL be a happy ending here....Karma will make it right, lol!

[304065]

. . . sigh. . .unlucky, just unlucky, as they used to say about my batting at Cricket.

You are getting good at engine R&R. . . I finally fixed my flywheel seal after FOUR engine drops. . . documented here: Assembling 901/05 Engine- Phase VII-- ANOTHER flywheel seal change!

It just takes TIME, which seems to be perpetually in short supply. . . persevere, and you will triumph!

At least having the jugs off will afford you the opportunity to check out the cylinder base sealing as well. It's interesting what you find when you do things over. . . what took hours of contemplation before and eight checks of the workshop manual now comes easily. Do you think you can remove the heads in banks of three so you don't have to pull the valvetrain apart?

[Spenny_b]

Originally Posted by 304065

. . . sigh. . .unlucky, just unlucky, as they used to say about my batting at Cricket.

Hi John,

Yep, completely soul destroying to tear down something that a) took a long time to build in the first place, and b) now looks dirty again and needs re-cleaning (cosmetically rather than internally).

Lol @ your cricket! No comment!

Originally Posted by 304065

At least having the jugs off will afford you the opportunity to check out the cylinder base sealing as well

Funnily enough, the leak I was seeing (which I thought was) coming from #5 cylinder base was I think, actually oil running down from the top side, due to the earlier hose popping from the chimney...which it now turns out was down to excessive crankcase pressure...which is probably also why I was seeing a few weeps here-and-there that didn't exist when we ran it on the dyno (and we were checking very thoroughly with a torch for any signs of leaks, for obvious reasons). A number of "things" now adding up.

Originally Posted by 304065

Do you think you can remove the heads in banks of three so you don't have to pull the valvetrain apart?

Yup, that's the plan, and hopefully may not have to strip the bottom end after checking stuff out.

[Spenny_b]

Progress update....

Finally got the engine and trans removed by midday on Sunday (some car storage logistics got in the way on Sat). As John mentioned, getting a little quicker at this now, but not a job I want any more practice doing...



Build-up the engine stand (it's a heavy bugger!), get the engine mounted, and it's teardown time.

Sorry Sir, I didn't quite catch that, "A complete EFI system, ready to go" you say? Well, yes indeed, it is.... Sorry, not for sale....



The usual stripdown pics....





And this is where we're at as-of midnight this evening...





Lots of careful bagging and storing. Running out of space, may need to borrow a few wallpapering tables. Hoping to get the top end for each bank off by end of play tomorrow night.

[TurboKraft]

Great job and a positive spirit, sir!

[jsveb]

Spenny, I completely missed this. I am so sorry to learn this. You don't deserve such a situation. You have been so meticulous.

I really hope something great comes out of this.