BC

No Issue. Its still an important idea. I went with a very large head unit.

tveltman

Brendan, did you modify your block to accomodate boost or are you running stock CR, etc? Also, if unmodded, how much boost are you running?

BC

The first engine I will run is a sort of test bed for all the changes. It is a 4.5L bottom end and will have 80 Euro S heads and 78 cams with a welded intake manifold. If it blows up, hopefully it will do so in the quest for learning. It is a test bed because I will be boosting it to hopefully 30psi and running E85. And an aftermarket EFI. I have all the supercharger parts, Air-Air intercooler, but I have yet to construct the intake, though I do have many of the pieces. The stock compression ratio is almost too low for the ethanol.

I have already built another engine, an S4 engine with coated pistons, head studs, MLS gasket, modified cams, and it will have a modified intake. It also have use Mike Simard's Girdle support/pan spacer, and it has a crank scraper as well. The crank is drilled, and the rods have arp rod bolts.

I would call that the "expensive" engine that I will run once I have more than a few thousand miles on the 4.5L engine and have learned enough to not break anything. But its not expensive if you think about what people like Greg Brown make, or Todd in Green Bay.

tveltman

It is interesting that you say you are using a 4.5 block. I pulled a 4.5 out of a junkyard as a just-in-case-it-was-useful sort of thing, and I have it all disassembled ready to be rebuilt. I am considering putting a modest pair of turbos in place of (hopefully) the intermediate mufflers on my S4, but I was wondering what you did to run the boost. My goal is to design something that could be used by anyone looking to cheaply "bolt-on" some power without having to rebuild the engine. This, of course, would necessitate relatively low boost, but if it could be truly junkyard-scavenged, then it would be entirely worth the "cost". At this point, it's all in my head. I think it's a pretty solid plan, but there are still kinks to be worked out, not least of which is plumbing two turbos to the middle of the car and back. I'd be very interested to see how your test bed turns out, and good call blowing up the 4.5L unit before the nice engine. good luck!

BC

The boost is a large Centrifugal supercharger, so it will be a bit easier on the engine than a turbo, but the losses will be greater at the higher power levels.

tveltman

Assuming you could reach intake temperatures of the NA engine, how much pressure do you think an unmodified S4 engine would accomodate? The one advantage of rear mounted turbos is the fact that all the piping from the turbo to the intake acts as an extra intercooler, so with an actual intercooler, you might be able to reach standard intake temperatures. The CR on the S4 engine is 11:1 I think.

BC

CR on S4 engines is more like 9.5:1. (9.7: 1 sometimes).

Its supposed to be 10, but its not, really.

My intercooler is 24x12x4, air to air, upfront. From results by another gentleman with 30psi, I can say that the intake temp gets very near ambient even without the intercooler sprayer.

My key, however, is the ethanol. It will defeat any sort of intake temp spikes, or heat soak issues coming from the prolonged use of boost.