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injector duty

2K views 92 replies 7 participants last post by  Brian_S 
#1 ·
oh dear



:rolleyes: here we go again!!!
put the fuel pressure down to around 46psi on gauge and went hooning round the country roads. i am happy with the fuel the engine is getting, but i am really running out of injector duty (do those 2 things even make sense?? i dont think i am underfuelling or tremendously overfuelling is what i mean) is this an injector size issue you think? or a mapping issue...i am trying the standard fuel map at the top end
would ideally like to top out at 85-90% at the limit, but as i watched the gauge go into the red i backed off lol
it hit 94% at 7300 which isnt ideal

(ordered that dave walker fuelling book for answers, but theres a 4 week wait for some reason :()
anyone got any pearls of wisdom/obviousness?
 
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#79 ·
i once set my FPR to 75psi to see if it would stop the tinkling noise i could hear. it didnt stop the noise but it did stop the popping on coastdown. i'll be f-cked if i'm turning my pressure back up to where it was at day 1, i was getting 150 odd miles to a tank if i was lucky.
 
#80 ·
thats pretty bad lmao
i get 220 or so, dont really run the tank dry tho

you have to knock the fuel map down by 5% (thats what i dropped mine by anyway) to even out the fuelling for the higher flow rate, but its sooo much smoother its almost driveable!!! :eek: ;)
no flames either, which is nice
 
#81 ·
i managed about 250 last weekend, all motorway. plugs are nice misty buff, thats good enough for me.

cold start is now fixed, replaced the coolant sensor and screwed the stop in a bit.

that 183 i got on the rollers was with cold engine, it popped up onto blue bar just as i pulled into the rollers bay.
 
#82 ·
enginedamagetastic :eek:
i finetuned the cold start this evening too, but do you find that when you stop for say 5 mins and restart it idles lower and isnt smooth till you drive for a minute? i guess its cos its sucking in the hot air (even in these cold temps my running temp is 28 and it went up to 40 when i switched the engine off and popped into safeway)
scoop gonna have to be done next year :rolleyes: :(
 
#83 ·
fear not, duh duh duuuuuh, magnetec to the rescue.

i reckon if it was up to running temp it would have made much more power, better seal on the rings maybe.

ive noticed that low idle thing. ive noticed also if i get the engine very hot it will idle high and revs will hang at 2k between gearchanges. it didnt do this when cold start was fooked.
 
#86 ·
whyzat? i have adjusted my fuelling map to suit the new pressure, you lot just crank it up and hope :p. steve thinks my engine isnt as standard as the one that was used to map the fuelling on their dyno :rolleyes:
cant change injectors anymore i am afraid :( as i would need a widerange lambda sensor to create the adaptive map which would reduce the fuelling map...sensor & controller is 300 quid or so and isnt ready to be used yet (steve uses ones costing 800-1000 quid :eek: )
 
#88 ·
16vastra said:
(steve uses ones costing 800-1000 quid :eek: )
:rolleyes:

So you can't just pop in a new fuel pressure or injector size in the MBE software then? bummer. (Emerald seems pretty good with both of them)

hmm, they be the saab jobby reds do they? If Rob really doesn't want them then ;) PM me a price RDS, I may well take those off your hands.
 
#90 ·
yeah Brian, thinking about it, i could work out the % decrease in the map that emerald does then apply it to my map, but i am STILL putting my map into the emerald software cos it wont let me copy&paste :mad:
reds are too big tho, i was chatting to the bosch tech people and they have the LET yellows listed at a whopping 346cc/min @ 3 bar (creams are 214 @ 2.5 bar)
 
#91 ·
The trouble is Rob that the 346cc is @ 100% duty cycle and you never want to run your injectors at this rate. so 20% less (ie 80% max duty cycle) =277cc min and again lower duty is still better TBH if you can get away with it.
 
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