Hotstart
 

JUst sounding out peoples theories...

Originally i've had my cranking settings on CLT only, It started okay 90% of the time, I then switched to CLT/IAT and that improved it marginally.

Lately I've been honing the cold starts and they're getting much better, but hotstarts have been a issue. They were fine if say the car stalled and re-started straight away, but a 5 min wait, say at the petrol station was sometimes hard work to get started.

I've since read that whilst an engine block takes quite some time to cool off the air in the cylinders cools off much faster....

Taking this into account I changed to IAT only and so far my hotstarts are a non-issue.

Obviously this is working well for me, but how is everyone else dealing with hotstarts and the like? One thing I have noticed is i'm adding a lot more fuel than everyone else...

Also, i noticed that i've managed to hit a duty cycle of 85% my car is bone stock, that can't be right can it?

85% duty is fine.

Check "More Cranking Stuff" play with First Start Enrichment %. Just squirted a jeep and it wouldn't start hot or cold with less then 50%. I set the jeep to 50% and I could probably pull start the thing. It's crazy how fast it catches!

85% duty cycle is certainly NOT fine on a stock Miata. Rich, check your injectors (have them cleaned and measured for flow rate) and your fuel pump/fuel pressure regulator. There is certainly a problem somewhere in your fuel delivery system.

I have a feeling my fuel pump is on it's way out. There's another 5 on the UK on an EMB that hits 80%+ dutycycle on his stock car and his pump is dying.

If I got a more powerful pump I'll have to re-tune won't I :)

Yes, a 5 minutes work. You could just scale down your table in Megatune and then just autotune when you get a WB.

On a 1.6 85% is fine, mazda used very small injectors in the 90-97 cars. The only reason people have been able to use them to turbo their cars is by running crazy high fuel pressue. You can't apply 99+ knowledge to a 90-97
as the fuel system is returnless. 85% at WOT is fine.

If you get a low presure 190 punp the tune should be close as it won't out flow the stock FPR.

I've got a 1.8 tho... does that change everything?

Not really because the injectors are only 25cc bigger and the motor displacement is 200cc bigger.
1.6 = 205cc Fuel Req Per Cyl 13ms
1.8 = 230cc Fuel Req Per Cyl 13ms

If you use the engine constants in Mega tune
it gives the same ratio 13ms for the 1.6 and 1.8

So, as long as your only get 85% around WOT you are fine.

err sometimes it goes a tinsey bit higher, I've got 90 once....

I definately need to change the fuel filter because as far as I am aware it've never been changed.

What confuses me though is a guy on the UK forum has a FM built 1.9l with a LINK and stock injectors running n/a and the max duty cycle he sees is 58%?

What does you VE Table look like? Mazda didn't leave alot of headroom in the injectors
because as far as they were concerned the car would never be changed. It sounds like your running very rich up top.

Do you have a wideband?

58% seems really low.

I've attached my msq, for the VE table, my webspace is down so I can't host a picture of it :(

Not got a WB unfortunately, it's going to be bought by the end of the month though, i'm finding tuning really frustrating atm.

I've heard the 1.8 injectors are good for 200bhp, If i'm already over the limit in terms of dutycycle I don't see how! ;)

They may be good turbo'd with a rising rate fpr but I doubt they can suppy that much NA.

I sent Keith from FM an pm see what he thinks.

Your 1.8 MAP looks alot like mine. My map is pretty rich at WOT so it may be running pretty
rich up top. Having almost no feed back the MS has no idea if your filter is clogged or pump
is crapping out. Even if you replace them the MS will still fire them the same. But if your filter
is old changing it would be a good idea.

cool thanks kingof!

I figured if the filter was really badly blocked it'd rob the pump of pressure, which in turn would require me to leave the injectors open for longer in order to supply the correct amount of fuel.

I'm not actually that rich at WOT, tho i can't be 100% sure cos of the NB sensor, but it looks like it's around 14:1 at WOT

Ok survey says that 85% is high but not crazy so. The goal would be to get into the 70's. You can do this by increasing the number of injections per cycle. Personally, I'd leave it alone until you get a wideband or a map of someone who used a wideband. Maybe a trip to the dyno and do a tuning session. IMO it's better to run rich then lean.

While you sensor is reporting 14.1:1, which is pretty lean at WOT even for an NA. I'm think your map is based on mine which has been show to be in the 12:1 range. Best power will be around 12.75:1 - 13.00:1. So, I don't believe it's running as lean as you think. Just so you know when a 02 sensor gets fouled from age or fuel, they read lean. Also has you know narrow band isn't really very accurate out side of the 14.7 range.

Okay, thanks Kingof, I was kind of hoping this issue and this issue http://www.msefi.com/viewtopic.php?t=23210 would be related!

I definately can't really resolve anything till I either become a tuning Genius overnight or get a WB :D

You don`t get a duty cycle as high as 85% on a NA car using standard injectors.
60-65% is quite normal for a normal aspirated 1.9 NA. 85% would be pig rich.

hrm well we'll see when I get the WB :D