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According to the standard wiring diagram the clutch solenoid is disengaged at wot , obviously the factory didnt expect you to have the pedal floored constantly
thanks. Where does it get the WOT signal? EZK, LH, or directly from the switch?
According to the standard wiring diagram the clutch solenoid is disengaged at wot , obviously the factory didnt expect you to have the pedal floored constantly
TPS i believe....so that is based on a switch..not "load..rpm" etc.....so he should be fine at 8000rpm as the clutch should be disengaged well prior to that
According to the standard wiring diagram the clutch solenoid is disengaged at wot , obviously the factory didnt expect you to have the pedal floored constantly
This is not true on any stock 928 - there is no means to do this in the HVAC - it knows absolutely nothing about the engine state - not even if its actually running or not.
The LH knows if the AC is on so it can allow for the extra load at idle - that is the only connection to the engine management.
It makes more than 750hp at the crank at those rpms, so it should get there if anyone is crazy enough to ever try.
On the "drill baby drill" project, there's now round 1" diameter hole there slightly offset from the original location. I had a wooden staff on the other side pressing against the hole such that I could locate pilot slightly offset away from the turbo speed sensor hole. I deburred the hole first, then smoothed the edge with a stone on a drill briefly. You can run a finger over the edge without getting feeling it rough. The oxygen sensor now fits thru, barely but it fits. I added some rust proofing there as well on the bare metal, what looks like burrs in the photos is in fact just the rust proofing substance. ...
Well that does it! The car's no longer original. Resale value is shot!
More seriously (anything would be more serious than that prior paragraph), I've really enjoyed following this build. Please thank John for stretching out our enjoyment for so many months...
Well that does it! The car's no longer original. Resale value is shot!
More seriously (anything would be more serious than that prior paragraph), I've really enjoyed following this build. Please thank John for stretching out our enjoyment for so many months...
If I know Tuomo right he has more in his pants pockets.
This project is not yet completed, it is more to come. Please enlighten us, Tuomo.
Åke
I was able to drive the car for almost a thousand miles last (this?) week. I'm getting more confidence in it every time I step in.
In my opinion, the ability to rev the engine to 8000 rpm completely changes the driving experience of the 928. The mental states of gentlemanly cruising and hard driving are completely different, in one case you're under 3000 rpm and in another case you're over 5000 rpm. The car does not drive like a turbo car, probably because of the 5L displacement. There's no lag even though the turbos are only "fully on" once you're out of the 3000 rpm cruising range. So if you want to go fast immediately, you downshift, just like with a normally aspirated car. But once you're in the hard-driving operating rpm range, there's no lag. The power is there to spin the wheels nearly instantly. And as we speculated earlier, it goes to about 60mph on the first gear and to about 95 mph on the second gear. If you drive about 75 mph on third gear, and recall now the engine rpm is in the power band, it accelerates really fast while burning rubber in the process even at the lowest boost setting.
The exhaust note is a little "blah" under 2000 rpm, but at 3000 rpm and above it sounds like the Flight of the Valkyries or the Stuka divebomber with Jericho sirens, or something in between, depending on the load and whether you're sitting in the driver's seat or riding shotgun:
On other news, there's a permanent install WBO2 sensor and controller semi-permanently installed now. No gauge or anything, but I can log with sharktuner without it being a project.
In terms of tuning, I've been cleaning up the maps from the data logs. With batch fired 80 lbs injectors and two 044 pumps running pump gas 93 octane E10, it's not going to ever be modern car precise in terms of exact low-load fueling. But it drives very smoothly and nicely. I've been trying to abuse the system as much as I can to test its limits. For example, I idled it on a warm day for many hours, and then started up again trying to overheat the fuel and cause a vapor lock. I believe that you can get it to pump some vapor bubbles right after such abuse and then you can maybe get those to separate a little bit in the rails at idle, so I can see about 1.5 AFR points leaner idle for the first minute or so after a very hot restart. It won't affect drivability, but the car would only pass idle emissions when running closed loop. (I don't get tested, and even if I would get tested I'd probably be able to somehow "Volkswagen" it to pass.)
Another thing that I may do is to move the flappy opening rpm level to 5500 rpm to reduce torque. You may ask why reduce torque? I need as much torque (or rather cylinder filling) I can at 3100 rpm to spool the turbos, so the first, flappy-closed torque peak is essential for me. However, the second, flappy-open torque peak at 4200 rpm is unnecessary because the turbos have already spooled. In fact, I am thinking that it may be counterproductive because it causes the wheelspin to start. I could eliminate that 4200 rpm torque peak by moving the flappy opening point to 5500 rpm which would allow me to run more boost and torque on average without losing traction. Now, why open the flappy at all? I think that the throttle body element of S4 doesn't distribute high density air completely equally, so opening the flappy will give me some air distribution insurance above 5500 rpm.
Another change that I plan to make is to really turn up the boost with rpms above that 5800 rpm. Also in the name of keeping the torque as flat as possible 4000-8000 rpm and car as fast as possible, without unnecessary tire smoke.
Tuomo, good to hear you're happy with the car. Over here normally at this time of year you can not handle the car the way you do due to ice and snow on the roads. But this year we are happy to have got an improved warmer climate thanks to the green guys so we are still able to drive our 928 cars at the end of November.
For those who do not know, Stuka is a short for "Sturzkampfflugzeug" which in English means something like "Dive fighter aircraft".
Åke
It's like driving on snow with data logs looking like this, notice I'm not even WOT but feathering the throttle on the way from 15mph to 95mph on the first two gears and the lowest boost setting:
Originally Posted by Strosek Ultra
Tuomo, good to hear you're happy with the car. Over here normally at this time of year you can not handle the car the way you do due to ice and snow on the roads. But this year we are happy to have got an improved warmer climate thanks to the green guys so we are still able to drive our 928 cars at the end of November.
For those who do not know, Stuka is a short for "Sturzkampfflugzeug" which in English means something like "Dive fighter aircraft".
Åke
I broke another transmission. Full load second gear acceleration (you know what that means on city street), pop, and it popped off the gear. The first four gears are gone, the fifth still engages. Case may be split, given how quickly it drained the gear oil after the shutdown. Going up for damage assessment this weekend.
How many trannies are needed to accept the fact that the 928 manual transmission can’t hold 770 lbf-ft torque?
I have two rebuilt spare trannies and two cores but what’s the long term solution?
How many trannies are needed to accept the fact that the 928 manual transmission can’t hold 770 lbf-ft torque?
Is this the first one that has died in the line of service? Can't recall. But whether it's the 1st or the 2nd it sounds like it's time time to consider something more stout, and throwing additional G28.13s on the fire isn't such a great idea.
How 'bout a Rogerbox? (Who had me advocating for an automatic on their 2020 Bingo card?)
Is this the first one that has died in the line of service? Can't recall. But whether it's the 1st or the 2nd it sounds like it's time time to consider something more stout, and throwing additional G28.13s on the fire isn't such a great idea.
How 'bout a Rogerbox? (Who had me advocating for an automatic on their 2020 Bingo card?)
The second G28.13 box to die under straight load and not because of a proximate cause of operator error (other than the 770 lbf-ft torque...). Two rebuilt ones waiting and two cores waiting to be rebuilt.
Something other than a G28.13. Maybe it's time for a billet case so the layshaft can't spread apart from the mainshaft and start eating teeth? Or it's Corvette transaxle time.
Something other than a G28.13. Maybe it's time for a billet case so the layshaft can't spread apart from the mainshaft and start eating teeth? Or it's Corvette transaxle time.
Has anyone gotten the “corvette” racing transmission geometry exactly right in a 929 chassis?
We need to contemplate that option.
In the meanwhile, I’ll dispose of some surgical face masks and G28.13 transmissions. Looks like they have about 200-400 full load acceleration pulls in them, them transmissions.
Tuomo, sorry to hear this, you need to take drastic actions like installing a Corvette transmission.
If you install another G28 transmission you have to reduce boost. Less fun but less problems.
Åke https://928motorsports.com/parts/tra...pgrade_kit.php
Last edited by Strosek Ultra; 12-05-2020 at 04:15 AM.
11-14-2020, 03:50 PM
