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Need help indentify crank fuel maps
Hi all,
A bit of background first. A year ago, I blew my engine up following a catalyst melt down. Looks like a piece of catalyst brick was swallowed by the exhaust port (under heavy decel???). I took the opportunity of the rebuild to request a pretty aggressive porting. Note that my RX-8 is now essentially a track day car that I sometimes drive on the road as well when I feel like it. The engine breathes much better at high RPM, with performance to match. Unfortunately, the aggressive porting resulted in very high overlap between intake and exhaust, which means a big loss of low end torque, but also very difficult starts. The crank fuel is too lean to start with, and starting under cold conditions require 2 - 3 goes. But warm, or hot, the situation gets worse. The base crank fuel is alrady too lean, but on top of that, the crank fuel decay is very sharp and it gets under ignitability well before the engine has had the time to start. This decay is a lot slower under cold start conditions. I wonder if some very informed owner on this forum could give me the exact data that are in the following tables so I can identify them in my PCM reclaibration tool (Hymee Pro Tuner). I'm looking at the following tables (probably 2-dims) : - The table(s) giving the initial crank fuel pulsewidth as a function of ECT - The table(s) giving the crank fuel decay (usually as a function of engine cycles) I did a search, and browse dozens of threads without finding what I'm looking for. Your help would be much appreciated to render my RX-8 the perfect track day car! Thanks, Fabrice A belgian owner. Bonus : my RX-8 at Spa https://scontent-a-ams.xx.fbcdn.net/...56576237_n.jpg |
Even with aggressive porting your throttle body should limit the amount of air intake at cranking. When cold it should run very rich . I would suspect you have a bad sensor somewhere.
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Originally Posted by logalinipoo
(Post 4583223)
Even with aggressive porting your throttle body should limit the amount of air intake at cranking. When cold it should run very rich . I would suspect you have a bad sensor somewhere.
By the way, I did not mention, it, but I'm an ex-Ford engine management engineer. I know what to do to improve things, but I need some info first. Fab |
Porting does affect start up and some tuning is required to battle the effects of the porting on start up and idle. What helped mine greatly was bumping up the idle speed slightly and installing a 2009+ RX-8 starter. That starter was probably the best investment I have made on my turbocharged street port RX-8. It has never started so fast, even when it was new. Oh, and get rid of that Hymee crap and get a Cobb or Mazdaedit.
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Well if you were an engine management engineer then Mazdaedit is probably your best bet.
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Thanks for your advice.
I have the upgraded 2kW starter. Is the 2009+ even more powerful? Idle is already set to 1000 RPM. I don't see how idle speed can affect crank fuel. It really is the crank fuel and crank to run fuelling that's the issue here. The Mazdaedit looks nice indeed. But as I already have a tool and access to all the maps. I just need to identify the relevant ones, and modify them. If nobody can help, I might look into puchasing the Mazdaedit. However, I can't believe nobody has this information on this forum and is ready to share it. Fab |
Yes the 2009+ starter is an entirely different design.
http://www.flickr.com/photos/9krpmrx8/8682848877/ Series 1 starter. http://www.nopistons.com/attachments...ps74524631-jpg |
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Bump!
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I still haven't got round to get any info on the crank fuel maps. I thought, based on the knowledge and experience usually displayed on tjis forum, that my questions would be easily replied to.
I'm still in e-mail discussion with the Epifan guys to see if they can update their mazdaEdit database to include the crank fuel maps, but I can't see how they would do it unless they can get inside info from a Mazda or Denso engineer, or if they use some kind of interface to check which addresses are used during cranking. Anyway, thinking of a Plan B, what do you think about swapping my 4-port red primary injectors by 6-port yellow secondary injectors. As I believe crank fuel is PW based, it will lead to extra fuel during cranking, as I need, but the fuelling would then be compensated by the injector scaling in "run" conditions. Your thoughts or experiences with primary injector swaps? Cheers, Fabrice |
Ok I'll take a stab at it,
If for nothing else than hopefully just to generate activity and keep your thread bumped. Unfortunately I think have more questions than answers ... 1) I have Yellows in the P1 injector location, it's not a 4 port AT but a 6 port MT. You'll need the Injector Latency Table as well if you do this, which won't be hard to get. - My question would be is that, how do you know that changing the "Run Time" scaling of the P1 injectors wouldn't also effect the crank conditions scaling? Thus defeating what your are trying to accomplish. <shrug> Clearly there's very little to no information on our Crank condition parameters out so, ya, who knows? EDIT: Just saw your post over in Stinksause's thread. Follow up question: What is your source for believing the PCM doesn't use the Injector Scaling during cranking?
Originally Posted by Rasputin
(Post 4583971)
Hi Stinksause,
I'm a bit puzzled by your issue. It seems to me that : - both 4-port and 6-ports engines use the same size red injectors as primaries - crank fuel is only delivered by the primary injectors So unless the crank fuel needed by the 4-port is a lot different than the 6-port, i.e. leaner, your 4-port should start the same as the 6-port. Unless there is indeed a difference, then your issue must come from a different crank fuel mapping. Also, can you confirm that scaling the primaries did not solve your issue? My understanding of the RX-8 PCM strategy is that crank fuel is not affected by the parameter for primary injector scaling, as the tables directly use injector pulse widths. Which is not the case with the "run" fuelling, which is LAMBDA based. 2) You mention in your first post that you already know the crank fuel map is too lean? How do you know it's too lean at crank? Where are you getting this information from? Can you post the Map for us to see? 3) What are the actual AFR's during crank and the RPM? Maybe a log file during cranking might generate some more feedback? (just a suggestion) 4) I don't want to be a negative nelly however as you indicated in your first post the aggressive porting has it's pro's and cons. Maybe you'll just have to live with poor starting. 5) The way out there idea. Perhaps you could use some sort of modified Meth kit to add fuel during cranking (sound dangerous tho and I don't know what the track rules are you run). Anyways, lastly: Bump and sub'd |
Originally Posted by wcs
(Post 4585375)
Ok I'll take a stab at it,
If for nothing else than hopefully just to generate activity and keep your thread bumped.
Originally Posted by wcs
(Post 4585375)
Unfortunately I think have more questions than answers ...
1) I have Yellows in the P1 injector location, it's not a 4 port AT but a 6 port MT. You'll need the Injector Latency Table as well if you do this, which won't be hard to get. - My question would be is that, how do you know that changing the "Run Time" scaling of the P1 injectors wouldn't also effect the crank conditions scaling? Thus defeating what your are trying to accomplish. <shrug> Clearly there's very little to no information on our Crank condition parameters out so, ya, who knows? EDIT: Just saw your post over in Stinksause's thread. Follow up question: What is your source for believing the PCM doesn't use the Injector Scaling during cranking? At this stage, I'm still not 100% sure crank fuel is independent to injector scaling. But that's my general understanding of crank fuel strategy in general and also by experience with the RX-8 PCM as I already tried to cheat on the primary injector scaling to let believe the PCM the injectors were smaller, and thus it needed to inject longer to get the required crank fueling. I could not see any change in the logged data.
Originally Posted by wcs
(Post 4585375)
2) You mention in your first post that you already know the crank fuel map is too lean? How do you know it's too lean at crank? Where are you getting this information from? Can you post the Map for us to see?
3) What are the actual AFR's during crank and the RPM? Maybe a log file during cranking might generate some more feedback? (just a suggestion) 4) I don't want to be a negative nelly however as you indicated in your first post the aggressive porting has it's pro's and cons. Maybe you'll just have to live with poor starting. I have no AFR data to show you as it is very unreliable at cranking speeds (by the way, myu starter cranks at 300 - 350 rpm), and does not segregate between burnt and unburned fuel.
Originally Posted by wcs
(Post 4585375)
5) The way out there idea. Perhaps you could use some sort of modified Meth kit to add fuel during cranking (sound dangerous tho and I don't know what the track rules are you run).
Anyways, lastly: Bump and sub'd Cheers for you help! Fabrice |
I haven't found any OEM cranking tables but my Adaptronic has one as well as short term and long term decay settings :)
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Adaptronic is a piggy back, isn't it?
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Test to see if injector scaling is used during startup fuelling.
Change your injector scaling with current injectors and see if it helps start up. Will obviously run like shit once idling, but it should be enough to get a conclusion. Try raising idle for this test if it won't idle initially. Also probably do the test while engine is warm so it doesn't flood. |
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