xschop's 928 LS1 build...repost from frenemylist

My donor engine, harness and ECM is from a 99 Camaro SS

The wiring will take some time and I'll post the 928 diagram which will be modified from the 948 diagram. I will get rid of any Porsche fuse relay that runs the GM ECM, Fuel pump, or fans, just as I did here....

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The 928 Driver's side firewall has a RED vacuum entering engine bay and that tube stays under vacuum to close the valve at all times until the heater control on center console releases vacuum and opens heater valve....

Heater Valve Solution is plumbed in....

FOUR SEASONS 74781 Heater Control Valve
Also remains OPEN under Non-vacuum and cycles the block coolant back to the LS water pump ports ¾” In, 5/8” out.
The ports on the 928 heater core are both 5/8”, so I used a ¾ to 5/8 hose line reducer (Gates 28611) to install the two way heater valve (74781)

Last piece of the plumbing mystery I still haven't found....Upper radiator hose.

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The lower radiator hose is Gates 21717 and fits perfect. (For the Northern aftermarket radiator)

Ok. Dayco part # 71132 will fit and Dayco 71085 will fit with a 32mm (1.25") water port adapter spliced in for the LS steam vent line that comes from the front driver's side head.....

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Wow, impressive progress, always had a soft spot for the 928, what year is yours? I'm digging all the red too!

This one is a '79 silver OB "Old Bastard" as the 928 community implies. The front hood, fenders, and doors are all-aluminum and lightweight. I can pic the hood up with one hand easily. This one is even more rare as it came from factory with no rub-strips, no passenger side mirror, and no sunroof, so it's one of the lightest. The LS1 implant looses another 150lbs off the front as the 928 engine is HUGE. I'm about to do the wiring which will take some time, other than that and exhaust it's about ready to fire up.

XS, looking great! Something you may want to consider if your car has axles with ABS rings, you can use them for your speed signal, you just need to have the PPM tweaked when you get your computer flashed.

Mark

Does anyone understand the German electrical schematic lol?

The only factory relay I would like to keep is the fuel pump relay # XVII so I don't have to drill a hole thru the firewall . It's main wire is Green/red from the plug.

I'm also trying to determine on the 14pin connector which port needs to go to the starter and which wire from the key is (+) when key is ON....

Green/Red (per Google) is Grün / Rot

I gave my set of 928 FSMs to a buddy last year...dunno if he still has them...I'll check

Watching this, here and on the List.......as, I am sure, is the Resident Hack....
All that room left in the engine bay makes the SBC look silly, right?
Would love to see the 8.1L in my Suburban under that hood with a few mods!
What a great GT you will have!

xschop wrote:Does anyone understand the German electrical schematic lol?

The only factory relay I would like to keep is the fuel pump relay # XVII so I don't have to drill a hole thru the firewall . It's main wire is Green/red from the plug.

I'm also trying to determine on the 14pin connector which port needs to go to the starter and which wire from the key is (+) when key is ON....

I downloaded the file you linked on the other forum...928 electrics_1978_cfd[1].pdf

Look at Current Flow Diagram 97-3 (a page or two above this page defines what G6; G23; N9;N21 are).

At the top right is the relay J17. The horizontal lines at the top of the page should be:

30 = +12 Volts from battery unswitched "30" (on 944 it's RD)
15 = +12 Volts from key "Run" position ignition switch "15" (on 944 it's BK)
X = +12 Volts from key "Accy" position ignition switch "X" (on 944 it's BK/YE)
31 = Ground from chassis unswitched "31" (on 944 it's BN)
50 = +12 Volts from key "Start" position ignition switch "50" (on 944 it's RD/BK)
btw...I don't see any:
P = +12 Volts from key "Off" position ignition switch "P" (on 944 it's GN)

87 on the FP relay is obviously the output to the fuel pump(s)..and also to N9 & N21 no longer needed/present.

One of the "31" (ground) inputs comes from N41 the Transistor Ignition Unit. Maybe it sends a ground only if the ignition is firing...a type of safety fuel shutoff I'm guessing.

The starter circuit at the lower left of the same page looks simple now that 50; 15; 30 etc are explained.

Now look at Current Flow Diagram 97-25 where the starter circuit is diagramed for the automatic since it is more complicated than the stick.

J50 relay at the top is the Starter Interlock Relay and its terminal 85 gets a ground when the Starter Interlock Switch on the shifter mount is in Park or Neutral. The starter (B) itself is missing a few obvious wires...e.g. the huge black cable from the battery (positive) to terminal 30.

The XVII relay terminal 87 goes directly to the fuel pump and terminal #7 on the 14-pin connector. The problem is the wire to the 14 pin is a smaller wire and I don't think it would be a good idea to use it as the (+) lead from the in-bay fuze panel after removing the factory relay. I may just wind up drilling a small hole thru the firewall and take a larger wire from the new relay directly to the #87 pin terminal after removing the relay and #22 factory fuze....gets rid of the $100 Factory relay....Whatcha think?

Pep Boys and the 6-pak of wire barrels from Autozone and not a damn one fit the LS throttle cam, so I had to spend more time at the shop churning one of these out.....

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I’ve always thought the wire gauges used on these cars were pathetic…and probably why these folks loved relays but still pathetic. I agree with you and would go with a heavier gauge.

Nice work Rob. T

Rob,
The folks that make the nice oil dipstick and throttle cable (Lokar?) sell the item you made, I called them and they supplied the correct size to fit the LS1 TB.

Throttle cable is done. I used one I got from Eric. It is about 36" and did the trick. The 928 Pedal clevis is easy to insert the cable in and reuse at the pedal....

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Shot of the Vette fuel filter and lines...

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Shot of the heater valve (TPC carries these valves too) and coolant lines at LS water pump...

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Upper and lower radiator hoses that I posted part#'s for. The 32mm a steam port adapter worked perfect.....

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I ported the oil filter adapter with a dremel before installing it. The influent side is always restrictive the way they are machined from factory....

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You'll need 2ea 4.0" x 1/4-20 bolts and screws to easily mount the adapter by drilling 1/4" holes thru the frame and bolting on the bracket....

Again , the adapters use M20 x 1.5 filter bosses and I went with Wix #51324 just as I did on the 948 swap....

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You'll need 4 Ft. of -10an oil/fuel hose. I used Push-Lok -10an fittings (2ea 90 Degree & 2ea straight)...

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Also in the pic above is the High pressure side of the PS rack that I posted part#'s for earlier. The return line stays put and even fits the GM PS reservoir perfectly (I added a billet filter in-line)...

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excellent work(as always) 'chop!

Hmm, interesting.
You should see if you can do a 928 -> 944 swap, that would be an awesome upgrade!

Porch, are you talking 928 engine or trans in 944...or both?
The 928 trans will fit in the 944 as I've stated before. The TT flange to axle lengths are almost identical. The Early 944's have outer stub axles that can easily be changed to 930 cv's which would make the axle swap alot easier. I've built a few custom axle sets to install the Vette trans in the 928 and that's what will be going in this ride eventually. Dinsdale built a simple, but effective transmember to get the C5 6-speed in his 928. I plan on cutting some of the sheetmetal and being able to install the vette trans from top....no need for custom transmember either

Started adding relays to my fuze-block....

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"no need for a custom crossmember"
tell me more!
i like the previous custom "cage" for the vette rear.
also not afraid to cut sheetmetal...

The entire LS/Vette drivetrain will fit with the motor mounts I designed as they can set the drivetrain back another 2" which is what is needed for the Vette rear differential to clear the factory 928 transmember. The axles are a done deal and I can make them on demand easily as I just modify 930 axles because the inboard vette CV's are splined same as 930 Cv's

Sub, where are pics of your hybrid?

I was saying you should get rid of that ugly 928 body and swap for a 944...

Agreed, I do like the 944 lines, but I'll have REAL V8 gearing and a double wishbone suspension with weissach toe-correcting suspension......and can change the sparks plugs too with this engine bay, not to mention the factory vacuum booster stays put . It'll be getting the Corvette brake master mod soon:P