9.4:1 turbo 6 port base ignition map comparison
 

Hey Everyone,

I've been working on comparing some turbo 9.4:1 base map data I've collected from a couple valuable members. I know turbo 9.4:1 is generally frowned upon, but for those of us crazy enough to try, I wanted to record some good info.

First off, I did not make these maps, Arghx and Bumpstart did. Thank you both for all your great contributions to my rotary research. Without your shared knowledge, I would be lost.

The three following maps are all slightly different, particularly in the upper vacuum range. The boost cells, and rotary split maps are also different. (I translated all maps into Haltech format with the same axis for ease of comparison. They are all based on standard -5deg base timing.) I have dyno tested Arghx and Bumpstart's ignition maps on my stock port 6 port turbo (gt4088 journal bearing) and made just over 300hp @ 12psi. That is pretty great for a base map in my opinion. Obviously more power to be had with proper tuning and a good set of knock ears.

Questions I have about these maps are:
- Any reason not to get into the 40's for advance there?
- Does the 13b make marginal power beyond mid 30's in vacuum?
- Could negative split be implemented on the vacuum idle and cruise areas?

Maybe someone can answer those questions. I will be doing more dyno testing hope to report back soon.

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This is Arghx's map, from here.
https://cimg9.ibsrv.net/gimg/www.rx7...01fe693597.png
https://cimg8.ibsrv.net/gimg/www.rx7...c4ad5bfe12.png

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This is Bumpstart's map from here.
https://cimg5.ibsrv.net/gimg/www.rx7...719d4a50dd.png
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This is Haltech's S4 base map from here.
https://cimg5.ibsrv.net/gimg/www.rx7...b626eaf865.png
https://cimg6.ibsrv.net/gimg/www.rx7...b7c2594c88.png
(search keywords: 6 port turbo base map, 9.4 base map, 9.4 timing, 9.4 ignition, 9.4 ign)

the 13B makes best power @WOT at 18-24BTDC, at cruise it'll get into the 30's, but 40 is probably too much. if you had a dyno where you can hold rpm and vary load (like a mustang), then you can try it.

the Rx8 uses negative split, but its only at idle/very low loads, it goes away very fast with any kind of throttle input, again try it at zero throttle, and any more than that you want something that can hold rpm

Thanks j9fd3s, that helps me understand why bumpstarts map is more in the 30s. I'll give it a try on the dyno and play with the cruise area to see what the results are.

will give it a try around idle. I've read it's pretty hard to hurt the engine while in vacuum, and that negative split can help achieve a leaner and colder idle.

I run quite a bit of negative split in all vacuum cells on my 9.4:1 rotors. From -30 vac, I taper from negative 25 split to 0 split at atmospheric, then from atmospheric taper to 15 positive split at 10 psi+. This is across the entire rpm range. this puts me at around -16 split at cruise and idle. When I remove this split, the engine runs noticeably worse.

I run 30 degrees leading at cruise with this split and at ~60-65mph I see ~26mpg highway with my large street ports and 285/30/18 160 tread-wear Advan Neovas. With that said I have not messed much with these settings to see if can do even better. This is at 16 AFR. I was able to cruise at 17 AFR with my old setup with these split settings, but my new Ballenger Motorsports wideband only reads to 16, so beyond that I have no reference (I should have bought the wide range version).

As for tuning theory, cruising at 30 leading and -16 trailing is effectively 46 degrees of advance as negative split is really advancing the timing. Actually -and this is just a theory- I think pulling some lead timing to make the trailing fire at 30-35 degrees may actually result in more efficient use of the combustion gasses in this case, as it's possible with 46 degrees advance the combustion is working against itself slightly. for example maybe lead timing should be 19 degrees advance and trailing should be -16 = 35 degrees total advance at the trailing plugs. I haven't had time to experiment with this as its been raining for pretty much 3 months straight here in Indiana.

Would you mind posting your full ignition timing maps like above? Really dig this...