stinksause

iTrader: (5)

I've recently found myself in the peculiar situation of getting a 4 port into a 6 port car.

The set-up is as follows: 4 port keg. 6 port im, 2 reds, 4 yellow injectors.

The 4 port has smaller primaries but bigger secondaries. The exhaust ports are smaller too from what I've read.

On start-up the car floods, BUT I can get it started by introducing a vacuum leak (brake booster hose). After start up the car will remain running once hose is reconnected. I have the feeling that I can get away with a smaller "leak"

Anyway the car has a cobb ap - but I can't find start up fueling tables.

What are the options?

1. Ghetto: boost control solenoid that takes cranking signal to pop it open and introduce vac leak
2. Less Ghetto: Smaller primary injectors
3. Pricy but proper: different tuning solution. Car has to be obd2 compliant. What are my options? MAZDAEDIT? Epifan? I have e turd blue as well.

Rasputin

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.

Lats but not least, as all you need is a bit more air to start leaner, can't you just open the throttle a wee tad to bring that extra air, instead of inducing an air leak?

Cheers,

Fabrice (trying to solve starting issues by PCM recalibration too )

stinksause

iTrader: (5)

Rasputin,

The issue is that the engines are different. The primary ports are smaller, the secondary ports are larger. There are not 6th ports.

All of the exhaust ports are smaller as well. In fact 4 Port guys use and 6 Port center iron as an upgrade due to the larger exhaust and intake area on the 6 port.

I believe that crank fueling is a programmed value rather than something derived from sensor inputs.

I was able to get it to work by modifying the idle fuel table in cobb.

Stock it was set to something between 11 and 12. I brought it up to 14.7

Hope this helps! Good luck!

Rasputin

Thanks stinksause,

I realise now that when you mentionned primaries and secondaries, you referred to the ports, not the injectors! My mistake. Makes more sense now!

So you manage to improve cranking fuelling by altering the idle fuel! So your initial issue was in the crank-to-run area more than just crank fuel?

Cheers,

Fabrice

stinksause

iTrader: (5)

I am not sure I understand your question. I leaned out the idle afr and I believe that reduced the amount of fuel injected at cranking. It sounds like you need to do the opposite - make it richer to account for more port area.

Opening the tb a bit more would also be helpful in my situation, however outside of building another circuit to do so, or messing with the throttle table, I am not sure how to do that. I think my solution is probably better.

What tuning solution as you using?

Rasputin

Your reply is useful enough, thanks!

For PCM reprogs, I've been using Hymee ProTuner from the very start. I actually received one of the first pre-series bricks years ago. Mark "Hymee" Pickering is acutally a personnal friend of mine. We even met once at the Nurburgring during one of his trips. I really value what he's done, well before any other proper tool was available.
I don't think the idle fuel table is identified in ProTuner. If you could post the original values of this table stating input, output et values, that'd be great as I could try to enrich on mine the same way you leaned out on yours!

Fabrice

GRX832

Hi does anyone know where i can get the mazda rx8 2004 workshop engine removal/ & entire teardown manual, help much appreciated

thanks

stinksause

iTrader: (5)

I think mazdamaniac has pdf's on his site.

I'll have to look I think stock it was 11.08 or something like that