High Hydrocarbon readings

General Chat About Exhaust, Cylinder Heads, Fuel Systems And Intake

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ChrisJC
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Post by ChrisJC » Sat Oct 08, 2011 3:45 pm

Without thinking too hard, presumably if the wires are reversed, the signal will be detected on the wrong side of the tooth, adjusting timing by the width of the tooth?

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stevieturbo
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Post by stevieturbo » Sat Oct 08, 2011 4:05 pm

The trigger generally recognises a pulse as the voltage passes across the zero line from high to low. ie the falling edge.

On the front side, ie rising edge this can be less precise. And if the ecu is looking for one style, then the actual timing of it may change slightly as rpm rises if it is the wrong way.

Although much better descriptions here. ( second link )

http://www.motec.com.au/webinars/webinararchive/

https://motec.adobeconnect.com/_a947097261/p37781647/
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Eliot
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Post by Eliot » Sat Oct 08, 2011 6:10 pm

Cant answer. But i can tell you the rpn signal is clean all the way up to red line now.

The engine seems to hunt around a little bit when idling and doesn't like idling slowly. It has a noticble idle - so we wonder if thats a charactistic of that 285.

There's a good table here showing that cam and that suggests bad idle too.
http://www.g33.co.uk/tuning.htm

Jon the owner really doesn't want something that will be a pain around town. So once our 5 gas turns up, if we cant tune around it - we will replace it with something mild.
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daxtojeiro
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Post by daxtojeiro » Sun Oct 09, 2011 7:11 pm

Eliott,
you should be able to get a nice smooth idle, it may need tuning in TPS rather than MAP, its more responsive for starters, but there are a few tricks to getting a good idle.

Start with setting the advance at 15-17deg at the 4 boxes around the idle RPM and load and set the VE table with the same value in the 4 boxes around idle, so that the fueling doesnt change at all. Then adjust all 4 boxes together in the fuel table to get a strong idle.
cheers,
Phil
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Eliot
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Re: High Hydrocarbon readings

Post by Eliot » Sun Jan 28, 2018 9:50 am

6 Years later - time for an update.
Yep, Seriosly - this car has been parked up that long since failing it's IVA - due to the owner having house moves etc.
Had time to get the engine running up to temperature and adjust the fueling to around 14.0afr - where it idles the best, any leaner and it seems to hunt around a bit.
We put the snap-on gas analyser on it and it was blowing about 5-600 at 900rpm and dropped down to 200-300 at around 1800rpm - Both figures are an easy IVA pass (1200PPM for pre-cat engine). Unfortunately a minute after putting the analyser on, one of the oil hoses blew off the cooler and flooded the garage with oil - so nosecone needs to come of yet again.

So whilst i think the cam is a bit racy, It should pass an IVA with a modest tune on it.
Eliot Mansfield
5.7 Dakar 4x4, 4.6 P38 & BMW 750i
www.mez.co.uk / www.hptuners.co.uk

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