Don Terrill’s Speed-Talk

mk e wrote: ↑Sun Sep 15, 2019 5:45 pm The Porsche emblem in the center seems to fit better

There’s also this option:

That is cleaner, neater imo....less is more kind of thing. If Porsche normal would make sure the shield is on then I'd put it on, if not I''d leave it off and keep it simple, its cleaner and your eye is drawn to what you really want to say...twin turbo.

John Kuhn is running the engine at very high boost to test what will break or wiggle itself loose.

Finally, something broke yesterday. Here are the symptoms after something broke:

At idle, compared to healthy runs:
- Idle slightly high
- Less intake manifold vacuum at idle

At full power, compared to healthy runs:
- Lower boost in the intake manifold
- Lower wastegate duty cycle
- Higher turbocharger speed
- Higher exhaust manifold pressure
- Leaner AFR
- MAF signal indicating slightly more power being produced per kg/h of air mass flow

What broke? John figured it out, I was scratching my head.

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Here's the story. The intake manifold signal vacuum/boost line connector broke, from old age as much as anything. The signal vacuum/boost line opening creates a large enough air leak on its own to reduce the idle vacuum and to increase idle speed. This signal vacuum/boost line being open isn't enough to impact boost directly, though. However, the bypass valve operation uses this signal vacuum/boost to determine when the throttle is closed to open the bypass valves. At high boost and with broken vacuum connection, the pressure differential is large enough that the bypass valves open, which explains the large boost leak as the bypass valve circuit is designed to flow a lot of air. Since the bypass valve circuit operates upstream of the MAF, this itself didn't cause the MAF signal to be misleading and thus didn't impact the AFR. So why did it lean the mixture under boost? The signal vacuum/boost line also references the fuel pressure regulator to keep the fuel-rail pressure minus intake-port pressure constant. The broken vacuum/boost signal told the FPR that intake port has ambient pressure, and therefore produced a too low fuel pressure, which explains the slight leaning out of the AFR. The leaning in turn sped up the burn, increases power, but caused knocks.

A Sherlock Holmes story.

The “final” pump gas run video:

A quick video update about the “dirty” run:

From the perspective of the clutch and transmission, the next two engines will need to run much higher rpms with the same (or lower) torque. Forged turbo pistons are in. Much lower weight and compression height, 7.5mm off from compression height. Rod will get longer. Skinny rings, squirters and Nikasil required:

More piston photos:

are you removing the nikasil so you can run a ring pack of your choosing?

are your new Mahle's 2618?

bentvalves wrote: ↑Thu Jan 30, 2020 12:53 pm are you removing the nikasil so you can run a ring pack of your choosing? Are your new Mahle's 2618?

The original block is alusil. The Nikasil goes on top of the alusil. There are very good 1/1/2mm ring sets for Nikasil. Street car so Mahle equivalent of 4032. Offset wrist pin and tight piston to hire clearances, too, since it’s aluminum on aluminum setup. Lucked out with an existing forging, very little material removed from the raw forging to make these. The pin is built like a brick house.

Conrod CAD model is going to 3D printing so John can test fit it before the 18 raw forgings go to final machining. We lucked out and there’s an existing raw forging that is almost exactly the right size for us, so these will be real forged rods, not forged rods in name only.

John’s video update on pistons:

Update:

Did you guys consider gutting that block for a darton mid type installation?

englertracing wrote: ↑Sun Apr 19, 2020 6:23 pm Did you guys consider gutting that block for a darton mid type installation?

Give that we want to stay with 100mm bore, sleeves of any kind would be a huge cost and unreliability problem. Can be done in a way that lasts but it’s a huge learning curve for this block and even in the end it’ll be way, way more expensive that Nikasil plating.

ptuomov wrote: ↑Sun Apr 19, 2020 6:45 pm

englertracing wrote: ↑Sun Apr 19, 2020 6:23 pm Did you guys consider gutting that block for a darton mid type installation?

Give that we want to stay with 100mm bore, sleeves of any kind would be a huge cost and unreliability problem. Can be done in a way that lasts but it’s a huge learning curve for this block and even in the end it’ll be way, way more expensive that Nikasil plating.

Um actually the darton mid design was really a solution to open deck block related issues.