givemethebighammer
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| posted on 25/3/06 at 10:41 PM |
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AFR Richer after fitting fast road cams ?
Is it normal to have to come down a few jet sizes when fitting sports cams. Or do I just need to adjust the ignition timing to sort this out.
I fitted a pair of Kent fast road cams to my 2.0 zetec the other week. Spent ages with three dial ages making sure they were timed correctly. The car
is running much richer now (too rich)
basically I have gone from standard ford 2.L zetec cams:
240 deg duration
7 mm lift
(info from Kent cams)
to
Kent fz2001
262 deg duration
Inlet 10.41 mm lift
Exhaust 9.52 mm lift
The car was running a little rich before but the cams have definitely made it much worse (11 AFR at idle !, not much better at wide open throttle). I
have attached the post cam install log (20 drive mixture of lanes and fast dual carriageway from a wide band unit (opens with logworks - free
download from http://www.innovatemotorsports.com/support/downloads/LogWorks2-setup.exe)
It should be easy to fix now I have an LC-1 wide band unit to help me. It was just surprising how much the cams messed the fueling up.
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DIY Si
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| posted on 25/3/06 at 11:18 PM |
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If I've got this right, the exhaust is coming out rich? If so, it may be because of the bigger overlap on the cams. As such, more of the intake
charge goes basically straight out of the exhaust thus making it richer. But at high(er) engine speeds, this should go the other way due to a
hopefully higher VE. Either way, it should need re-jetting.
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givemethebighammer
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| posted on 25/3/06 at 11:27 PM |
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Yes, the extra overlap could explain the exhaust richness, but not the wide open throttle richness. I was expecting to have to fit bigger main jets
after fitting the cams, but at the moment it looks like I'll be going smaller ? It may be that the jets were a little too large to begin with (I
didn't have the wideband unit to test it before the cam upgrade). Like I said the car was running rich before the upgrade, but I thought that
the richness would have been improved by higher lift cams. Seems to have got worse though.
?
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DIY Si
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| posted on 26/3/06 at 08:53 AM |
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Have you changed anything else recently, such as your airfilter, exhaust etc? Anything could affect it really. Another possibility is that is has
actually become less rich. If you couldn't really measure before, it makes comparsion difficult. Personally, I just get it on a dyno and let the
pros see what to do.
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rusty nuts
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| posted on 26/3/06 at 09:41 AM |
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Unburnt intake charge going straight out of the exhaust would result in an increase in hydrocarbons not not C.O. You would need a four gas analyser to
check though. Suspect the best way to sort it out and get the best from your new cams would be a rolling road session. Was fitting the new cams worth
any more power?
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givemethebighammer
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| posted on 26/3/06 at 06:20 PM |
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The dyno is where it is going, but I intend to use the wideband unit to get the car 90% of the way there before I go. That way I save some money,
learn more about tuning the car and also have a better understanding of what the dyno bloke is doing.
More power ?, supposed to give me about 12-17 bhp, at the moment it's running worse !
All part of the fun I guess, no such thing as a straight bolt on upgrade.
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givemethebighammer
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| posted on 27/3/06 at 02:46 PM |
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Next log file 160m.log
Running 160 mains, 42 pilots (three turns out on air screw). Previous log (pre work.log) was 170 mains, 42 pilots (one turn out on air screw).
Both logs blackbird dynojet needles with clip in position one (top)
I think I may be about there 160 mains are better than 170's. I'm going to try:
1. 165 mains
2. Raising the needle 1 clip position (to richen acceleration, it leans out a bit under snap throttle)
3. Changing the pilot jets for 40's then 38's
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NS Dev
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| posted on 27/3/06 at 03:12 PM |
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Hi!
good to see you got the cams in, sorry I was of no assistance in the end, but sounds like you got em sorted ok, it's ok when you think about
what you are actually trying to achieve isn't it!
Re. fuelling, yep normal to have a touch of overfuelling at lower REVS, remember that it's these that are relevant not just throttle opening,
it's gas speed in/out of the engine that's the critical factor, and this is set by revs.
You will need to alter the fuel slope, from less fuel at low revs to hopefully a tad more at peak power revs (6500 ish??)
I am a know nowt when it comes to jetting though so can't help you there, grown up with fuel injection where you just adjust the numbers!!!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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givemethebighammer
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| posted on 27/3/06 at 05:59 PM |
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Thanks NS, It took me ages to get the cams in (ordered another two cheap dial gauges) but got there in the end. Neighbours weren't too pleased
when I ran them in though .
Since I got the LC-1 AF unit, it been strangely enjoyable tuning the carbs ?
Change something on the carbs, plug the laptop in, go for a blat, come home, look at the log and see what difference it has made, change something
else.................
Or am I just using it as an excuse to drive the car more ?
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