Djwade

So my curiosity (and the presence of a good deal) got the better of me and I'll be dabbling in S/C for a little while before picking up a TSE turbo kit.

I just got my MS3x put together and will be putting it into the car once the engine is assembled and reinstalled and running N/A for a bit to familiarize myself with tuning and TunerStudio.

In the meantime, I wanted to start gathering all the necessary information in order to run the S/C smoothly and safely once installed. I know S/C IATs tend to run quite a bit hotter than Turbos, and so I know I'll be running a bit richer for detonation prevention, though I've also taken measures in the engine build to keep knock at bay.

Some relevant details:

BP-4W engine, 8.25:1 CR, Forged Long Rods
S/C kit will be Moss MP62 Hotside with TDR Intercooler
Starting Boost will be ~6-8psi or so, upped to ~14psi after I feel the need/desire.
E85 planned, but not running for the next few months till i upgrade fuel lines/flex fuel

I know at the lower boost I won't need to be as aggressive with the richness, but as things get closer to 14psi, I'll want to make sure I'm keeping the engine happy.

There's a good chance that my google-fu isn't as good as it could be, but the best discussion I could find relevant to this was patsmx5's discussion on running at high boost on pump gas (LinkyLinky). His table (shown below) was used for some very high S/C boost (21+ PSI), and higher compression than I'm running (9-9.5:1) but on better pump gas (93 vs. California 91).

Given all of this, Is this a decent place to start given all of the variables? Is it safe to lean out the cruising area, even with a S/C? Should the Target AFR scale linearly along the RPM axis given that a S/C's boost scales (mostly) linearly with RPM?

Any help greatly appreciated.

Best,

Dan

Djwade

And if this is better off in the supercharger forum, someone with the capabilities to do so, feel free to move it. I have just been thinking about it from a MS point of view, which is why I posted here.

jstck

Is there any reason why the target AFR map would be any different for supercharger vs turbocharger (or for that matter NA, for 100kPa and below)? IATs could be different, but that would vary a lot between different setups of the "same kind" (different intercooler sizes and intakes and whatnot). And how much would "reasonable AFR" vary with charge air temperature anyway?

Stockish

See I was thinking the same thing. One would think under 100kPa it should be similar or the same. The only weird thought is they were having tip in issueand not addressing them in tip in.

Djwade

To the best of my understanding, if both systems were perfectly efficient, they would have the same target AFRs (assuming identical intake/cooling, because the compressor outlet temp. would be identical for compression. However, not all compressors are made equal, and the MP62, due to compressor design, should produce more heat because of its lower efficiency, as compared to a turbo of any make (assuming it's sized properly, and not something the size of a thimble spinning at 1*10^14 RPM).

And while you're correct, different set-ups will have an impact on IATs, I'm going to be using a very common Supercharger and Intercooler combo (Moss MP62 + Trackdog Racing Intercooler), so I'm operating under the hope that there's enough experience with it to guide the discussion on target AFR for midrange supercharger boost (~14PSI)