928 Twin Turbo article from 1984
#4
Three Wheelin'
Thread Starter
#5
Nordschleife Master
Nice article. I think these turbo systems were rated with a certain boost pressure and then there was an expectation that wastegate and boost controller “adjustments” would be made by the user...
#6
Former Vendor
Try to keep in mind how crude fueling waa and what "tools" were available to change said fueling (if you weren't Bosch,) at that time.
That factor, alone, was very limiting, for everyone.
There wasn't very much "micro" in a Callaway micro fueler.. Better than a 5 gallon pail of fuel, sitting on the hood. with a hose running to the intake, but not by a whole bunch.
#7
Nordschleife Master
Long before my time, I admit! ;-). Still, human nature remains the same and it’s not possible for a live red blooded human to not turn that screw up until the ring lands give up.
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#8
Former Vendor
#9
Nordschleife Master
The three counterpoints to this are: First, as already mentioned, the S4 rotating assembly overall really isn't built for high rpms in many ways. Second, if one lets the engine to overheat then some problem will surface at some point. Third, no piston, forged or cast or whatever, can withstand extended periods of high-load detonation. S4 pistons will give up for sure if you throw any amount of boost at them _and_ allow the engine to detonate either because ignition timing or fueling are not set correctly. But so would a forged piston, too.
A lot of people automatically assume that forced induction engines are the ones that require forged pistons. By my thinking, the reality is 90-degrees different. I think that it’s high rpm engines that need forged pistons, whether they are forced induction or normally aspirated. Forged pistons are stronger _per gram_. They aren’t automatically stronger than heavier cast pistons. In a low rpm engine, you can just make your cast pistons a little heavier and they’ll last for a long time. In a high rpm engine, you can’ti make the pistons a little heavier because weight itself causes the whole rotating assembly to be less reliable.
Last edited by ptuomov; 10-31-2017 at 09:56 PM.
#11
Three Wheelin'
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#12
The Parts Whisperer
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Many many years ago i had a customer with a 1982 Calloway 928 and after his second engine he came to me looking for options. I installed a 1989 gt motor in it and he swore it was faster than the turbo ever was. Installing that engine back then was a huge undertaking for me. We also stuffed 315 rear tires on it with some custom Gotti wheels.
#13
Banned
I agree fuel was a limiting factor back then. You should have seen the black mystery boxes that came off the Devore car that he adapted to trim the fuel curves with. It was state of the art back then, but that isn't saying much.
#14
Three Wheelin'
Thread Starter
The Microfueler is a pretty interesting box, and can control one or two additional injectors. I believe it depends on the version of the MF box.
Anyways, I know someone who changed their MF to a "modern" system and the car did run even better, but no surprise, as the "brains" of the controller have gotten better. Like a Commodore 64 v. Macbook Pro. Anyways, the MF was simple and worked. But as agreed (I think), time marches on and even better auxiliary injector controllers exist.
Heck, I remember something for Turbo Buicks (parts released) in the 90s which was very crude, especially compared to the MF.
#15
Nordschleife Master
Many many years ago i had a customer with a 1982 Calloway 928 and after his second engine he came to me looking for options. I installed a 1989 gt motor in it and he swore it was faster than the turbo ever was. Installing that engine back then was a huge undertaking for me. We also stuffed 315 rear tires on it with some custom Gotti wheels.
The 89GT engine in a 1982 chassis is a legitimately fast combo, especially if the exhaust isn't completely stock.