Dennis Wilson

How is your turbo plumbed into the intake circuit? If on the inlet side of the lower plenum/fuel distributor, the higher boost will adversely affect the piston in the fuel distributor and cause an overly rich A/F mixture (reduced control pressure). The factory design on CIS cars always has the turbo installed between the fuel distributor and the throttle plate for this reason.

Dennis

Fabio421

I don't think there is anything special about the coil. You should be able to buy a good strong coil for alot less money than that.

Imo000

That’s not so. I’ve replaced the coil on my ’83 with an Accell (sp?) super coil, just to see if there is an improvement and the car misfired like crazy. Then put the original Bosch back in and it ran fine.

Oz Chuck

Thanks to all who replied. I have it sorted now.
I spent the last couple of days swapping bits from other cars trying to sort it.
The other night at work I changed the vac advance just in case and then the car would not run at all. Swapped back and still the same. Got it started by advancing way past the end of the slot and limped home hardly able to do 100 (60mph). To make things better while trying for 1 st gear to struggle up a hill near home the rear gear change coupling bush fell apart and fell out leaving me with rev,2nd and 4th.
Figured the only thing left was the dizzy itself (pickup) so swapped it and voila. All good. The idle is also much better now as is cold starting.
Dennis the turbo draws through the fuel distributor so it is not under pressure.
Now today I had some detonation coming in at 4500rpm which is around 9 psi. It was 35 degC , (95F) and I am also getting a good puff of oil smoke on the gear change which may or not be related.
Chuck

Fabio421

Interesting. Any idea what the difference was?


At 9psi you will need to pull more timing than 4 degrees. The mod we were talking about earlier in the thread was focused on the vacuum advance. Think of it this way, under vacuum the diaphram moves in one direction, under boost it moves in the oposite direction which retards the timing. Do the dual distributors have the diaphrams with two vacuum ports? If so, you should disconnect the one for the vacuum retard. Use a small pump ( bicycle pump ) to put pressure to the distributor while the car is running. Have a timing light hooked up so you can see how much timing is pulled. I am interested to see how much timing is pulled without grinding the arm.

Please post some pics of your build.

Dennis Wilson

Chuck,

Have you modified the crankcase ventilation system for the turbo? The smoke and detonation could be caused by excessive blowby getting into the combustion chamber.

Dennis

Imo000

I never looked into it but the Accel coil was good as I used it on my turbo dodge before the 928 and on the shop truck a couple years later. However it wasn't good enough to run the 928. I was really suprised to see that.

Roy928tt

I'm no car electrics guru, but when I was messing atround with the coil in the porsche I found the voltages very strange, when I finally tracked down an experienced hand with Bosch electrics he confirmed that what I was measuring, was as it should be. So I refitted the coil and have never touched it since, therefore I'm less suprised that the coil is expensive/unique.

Chuck, are you running a wastegate on your car? I just ask because you mentioned "4500rpm which is around 9 psi"

If I remember correctly 7 psi on the reverse side of the vacuum advance took out 7 degrees of timing.

Cheers Roy

Oz Chuck

Roy
Yes the car is wastegated at 10psi but does not usually get there til about 3000rpm. I am still coming to terms with watching anything other than the road while on boost and not driving full pedal yet while sorting.
Dennis.
Crankcase is vented out on the ground under the front of the car.
Fabio
I will get the timing light this afternoon. I have a standard dual port vac unit and I will try and see what advance change there is then mod it.

As for the build the car is a 81 4.5 high compression CIS with the 'S brakes. Now it has 79 internals and is dry sumped, turbo-intercooled, nitrided crank and modified oiling to the 2-6 bearing.
I have removed spoilers, headlight squirters, rear wiper and have 245 rear tyres on 944 8" phonedials with 31mm spacers and Toyo RA-1's all round.
Turbocharger modification is legally approved hence the blue plate to the left of the bonnet catch.
It is about 3/4 put back together after 3 years of " I'll just do that as well".

Oz Chuck

The engine runs from the standard oil pump which draws through a filter from a 5 l drysump tank in the front left guard in front of the tyre. The tank has a clear hose level tube up the side to check the oil and it has a drain bung on the rear. Oil is recovered by a 3 stage peterson pump, 2 from the sump and 1 from the bottom of the turbo as it is quite low under the lhs head. I still have ps and air but the air pump must have fallen off somewhere.
The turbo draws through the cis head through a 3" tube down the lhs of the motor then feeds out into the left guard above the left tyre, round under the head light into the intercooler, then out the other side round under the rhs headlight back through the guard and into the front of the plenum which I cut and shut to have the inlet at the front.
It is quite responsive even with all that length of pipe.
The exhaust manifolds are hand made from steam pipe bits. The right side comes out level with the head at the rear then runs over the clutch cover under the air cleaner and joins into the left where the turbo mounts. The joiner pipe between the two sides has large ball joint type self aligning screw together steam pipe joiners and is easily removable. It is heat wrapped and hasn't cooked anything yet. The turbo has to have the intake housing removed in place to get it out due to its size.
I have also cut 3" off the front of the rails to get the intercooler pipes past each side.
As for the oiling I welded the gallery where it feeds the 2-6 bearing and drilled below the weld into the very bottom of the oil channel in the vain hope that any of the aerated oil would be at the top and miss the crank and go into the head feed.
Chuck

Roy928tt

Great stuff ! I love it, another incantation of the turbo 928. It's a great challenge to take up, isn't it, so rewarding when it all starts to come together.

Best wishes, Cheers Roy

toofast928

Very nice It must be a fun ride.

Iwanna928

So many of you guy's are so talented! The things you do and your knowledge always blows me away. I spent way to much time on a tennis court.

I tried to put my door panel on my car the other night and it took me FOREVER. I finally got her on but it was a good thing my little ones were sleeping as my fowl language was at an all time high! All I was dealing w/ was a few screws and putting one a bunch of clips. It felt good when it was done but then I read about this turbo project and all the other things the guy's have done on the boards and I realize I am an idiot!

Post some dyno numbers when you do it and a video of it would be way cool. Would love to hear it under WOT!

Stephen

Imo000

Do you have any pics? Sounds interesting.