SwayBar

Question:

Did the new exhaust manifolds perform as you'd hoped/expected?

ptuomov

The cast exhaust manifolds work about the same as the hand fabricated ones, but are probably more durable and much less time consuming to make.

The plan is to drive the car for a while and run a couple of tests.

The first test I want to run is to plug the tailpipe with an insert and see how that impacts the power and sound. Right now, the tailpipe is larger than it should be and adds a little noise at normal running. During fuel-on overruns etc. when the exhaust throws a little bit of flame but doesn't pop. I have a hypothesis here why it doesn't pop and I want to confirm that.

The second test is to hook up the blowby meter to the crankcase and blow compressed air into the crankcase. I want to see how much headroom the breather system has in terms of accommodating even higher blowby gas flow volume without ejecting oil from the breathers. Right now, they are bone dry.

The third test is to test plenum spacers and flappy operation to see if I can get the flappy closed torque peak to shift to lower rpm and use that to spool the turbine earlier.

The above are gentle little measurement projects. Then when the second engine built with the same recipe is ready, turn this engine in the car to eleven and really test it’s mettle for durability.

ptuomov

The 8000 rpm engine in the car uses this windage tray/scraper/baffle system to control oil: http://www.crank-scrapers.com/Porsche_928_pictures.html. It's made by Kevin Johnson of Ishihara-Johnson Crank Scrapers.

Now, some of you may know that I've had various heated debates with Kevin Johnson over the years on various engine and oiling related topics. Before getting into details about my opinions about scraper systems, let me just say that his system currently installed in my car works extremely well, so congratulations to Kevin for the design. It's not puking oil out of the breathers in the dyno at 8000 rpm. Although I haven't driven the car in this latest configuration yet, John has driven it pretty hard, we've also observed no problems on the road.

If we were just running this engine on a stationary dyno, the only pieces that would be required for the engine to work really well are the oil-pan spacer, possibly the early 928 sump mesh cover or something analogous/functionally equivalent, and some drain-blocking pieces from Kevin's kit. Of course, we are not just running this engine on a stationary dyno. Instead, the engine is in a car and will be subject to all sorts of accelerations. The rest of the kit is helpful in keeping the oil from escaping the deep part of the sump, uncovering the pickup, and flowing into the rotating assembly.

Two concerns have been voiced about adding such general windage tray/scraper/baffling devices in the 928 crankcase.

The first is whether these devices directly hinder oil drain. This is (per my impression) the more popular concern among certain 928 enthusiasts. This concern is in my opinion mostly misguided. The oil is going to drain very quickly thru even small openings on a vibrating engine, as long as crankcase gas flows don't prevent this oil return.

The second concern is whether the scraper/windage tray devices hinder crankcase air flows between the bays. There's the generic concern that not enough gas flow area between crankcase bays will increase pumping losses and reduce power. This is not a concern to me, because we've got enough power. However, the lesser flow area between bays may force the piston pumping pulses to equalize between bays in an undesirable way. This may indirectly hinder oil return. This undesirable effect is what one should be on the lookout for when evaluating alternative windage tray/scraper/baffling systems for the 928.

We just ordered a couple more systems from Kevin to put on various engines, one of which will go to the sister engine of the current engine that will have the same 8000 rpm rotating assembly.

Thom

Does your engine still run with its original 87 heads or later reinforced heads with longer bolts? Sorry if this was mentioned before already.

ptuomov

This engine has later heads, maybe 2R? In any case, despite what the market pricing of heads says, I don’t think there’s a big difference. The next sister engine will get it’s early ‘87 heads.

bertram928

I totally agree with this concept; taking a motor optimized for low rpm NA drivability and adding large turbos to fill in the high rpm torque curve.

bertram928

Unlike 4 cylinder motors, there is no need to boost the s4 motor at low rpm’s.
Even with 2.20 rear end my stock 928s4 5-sp top gear highway acceleration is more robust than my 600+ hp 6.0 L m5

The way John has it currently set up will minimize drivetrain parts breakage or lifting of cylinder heads

I am only a 90 minute drive away, need to come visit this beast

ptuomov

I think that’s a good recipe when the base engine is large displacement for the car to start with.

What John Kuhn has done with my car is add another 1300 or so safe rpms, add almost 2000 usable rpms, and double or triple the torque at higher rpms, while keeping the car near completely stock behavior at 2300 rpm cruise and below.

There are a lot of limits that need to be observed for reliability: max peak cylinder pressure, max average cylinder pressure, max torque, max rpm, max EGT, knock probability and knock frequency at high loads, etc. The envelope is being increasingly filled up...

ptuomov

Probably the final video of this car on John’s dyno:

Rob Edwards

Groovy, when is the car coming home? Be nice to enjoy it before the air gets too dense and the traction becomes limiting.

ptuomov

Two weeks if I’m home then is the best guess. Nantucket now and I may have to fly to Finland to close on some deals.

John is building the sister engine with the same recipe now — so that I don’t have to be timid turning up the boost at 8000rpm when I get the car on a dyno in New England.

jcorenman

Tuomo, thanks for posting that. It is an amazing build, and thanks for sharing that.

Tony

Amazing. Nice to see the light at the end of the tunnel.

Looking forward to seeing how the power numbers transpose to performance on the road.

it should be a sub 4 car to 60..

Low 11s in the quarter?

passing a line of traffic would be woooooooosh.....and the jump to light speed.

ptuomov

When I had the car the last time with the smaller system, it burned rubber continuously to 120 mph running up a hill. It’s not set up to have a fast 0-60 mph time, but it will be fairly quick from 40-100 mph. The quarter mile time will be slow, too, but the trap speed should be pretty fast.

It’s a stick-shift street car. Street cars run on pump gas, have air conditioning, and run street tires. Therefore, it will never be very quick off the line. However, it should be fairly fast once it’s moving comfortably forward. So poor ET, decent MPH, that would be my drag strip prediction.

dr bob

Tuomo --

Are you guys fitting any kind of traction-control smarts? Your 'burns rubber to 120' comment sounds ominous. In my brief experiences with cars that did that, driveline problems seemed to max out when tires finally hooked up again unless there was a very specific effort to get out of the throttle to make that happen.

I know that there's a lot of discussion on Turbo Todd's build description about adding rear weight for traction, along with some active engine-management efforts. You are using the Bosch LH and EZk controllers, which at least in the later versions have a pressure-switch input to reduce power via ignition timing for auto gearbox protection in high-load upshifts. Short of a "drive-by-wire" (vs. "drive-by-cable") throttle, or some inputs to an electronic boost controller, there has to be something you can do to protect the gearbox and axles.