Skirrow
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| posted on 4/3/13 at 11:54 AM |
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AFR Meter vs Rolling Road
I'm about to fit a Megajolt and bike carbs to my pinto.
Rather than rolling road it when it's done, is fitting a wideband Lamda sensor and an AFR meter, and then tuning it myself a realistic
alternative?
I imagine the sensor and meter will cost the same as the rolling road first time round, but if it's a reasonable alternative then it can be used
over and over each time I make any changes.
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Ben_Copeland
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| posted on 4/3/13 at 12:10 PM |
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It's difficult to tune on the road, not impossible but tricky as you need to turn it at every stage of the throttle. Must be difficult to watch
the afr at full throttle on a public road!
Ben
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Alfa145
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| posted on 4/3/13 at 12:10 PM |
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On bike carbs I'd get it setup by someone with a rollingroad and that knows what they are doing with bike carbs on a car engine. Once setup will
probably never need touching again.
Then if you do make changes you have a very good base to build from
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mark chandler
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| posted on 4/3/13 at 12:21 PM |
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The problem I found was catching the points, if you have a long hill nearby then it becomes much easier as you can log to different loads and throttle
positions without the car getting away from you.
With megasquirt I found auto tune worked quite well, once I turbo'd the speeds and acceleration made it impossible ( for me anyway) including
trying to log and adjust even at Cadwell, although a good day was had a rolling road session a month later found another 30bhp so in hindsight should
have RR'd first.
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Paul Turner
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| posted on 4/3/13 at 12:39 PM |
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I fine tuned the fueling on my 2 litre zetec on MBE injection using an Innovate LM1 and their Logworks software. The LM1 logs the AFR and with the
addition of the RPI box the revs and TPS position. You just drive normally or do WOT runs and download it all later. It worked a treat once I became
familiar with it but I would estimate it took in excess of 20 hours on the road (and a similar amount of time at the PC) before the AFR readings were
exactly what I wanted. I took it very carefully making only small changes. If I were to do it again I would feel confident enough to believe what the
machine is telling me and make larger adjustments.
Its easy with injection, its only numbers in a map but with carbs it would be near impossible unless you have a huge supply of jets available.
Take it to a rolling road.
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coyoteboy
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| posted on 4/3/13 at 01:04 PM |
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+1 for Paul Turner's response, almost exactly.
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Skirrow
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| posted on 4/3/13 at 01:14 PM |
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Cheers fellas, I suspected the general opinion would be to rolling road it. With that in mind does anyone know roughly how much I would pay for having
the carbs set up and the megajolt mapped at a decent place?
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ChrisW
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| posted on 4/3/13 at 01:16 PM |
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quote:
Originally posted by coyoteboy
+1 for Paul Turner's response, almost exactly.
Same from me. Megasquirt can be done this way. Just set a sensible REQ_FUEL and then take the car out and drive it normally. Take it easy to start
with in case there are any huge lean spots, and build up the power as you get the map more defined.
If after a few hundred miles of logging, tweaking, etc you havn't driven at a particular load site the chances are you won't ever do it.
Just take an educated guess based on the adjacent numbers 'just in case'.
The only caveat I would point out is that a chap I know tried to do this on a turbo engine but instead of taking it easy just started nailing it right
from the outset. Turns out his base REQ_FUEL was crazy lean and he destroyed the engine. Just don't be a moron, apply common sense, and
you'll be ok!
Chris
My gaff my rules
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froggy
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| posted on 4/3/13 at 01:32 PM |
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bogg brothers will be a good place to do this
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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whitestu
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| posted on 4/3/13 at 01:35 PM |
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I did mine with a wideband. I didn't need to change the jets once I had initially drilled them to 1.6mm, but did play around with the needle
height. It's probably running a little rich, but not much as MPG is good and plugs are the right colour.
I'm sure an RR would be better, but I didn't have the time to spend during the week to do it.
Stu
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perksy
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| posted on 4/3/13 at 02:22 PM |
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Just curious
The lads using Megasquirt or Mapped Ignition and doing this on the road, How do you check for it Knocking ? Are you using a Knock sensor or ??
Obviously the fueling can be looked with the Afr meter etc, but just curious how you advance the Ignition to make the ultimate Torque figure without
it knocking ?
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coyoteboy
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| posted on 4/3/13 at 06:59 PM |
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I wired the knock sensor through my sound system (through some protection) and whacked up the volume and filtered out everything but the stuff around
the knock frequency for the engine (around 6khz IIRC). But ultimately I started very conservative and built up to the point where I got the occasional
unpleasant knock, then knocked it back a few degrees. Then did a number of load runs to try to get it to repeat.
What I did note is that the transient knock conditions are totally different from the static. I could hold full throttle at 2500 rpm (just before
boost) without knock but full throttle THROUGH it (same MAP values) sees knock initiation that then cascades through boost. This means I have to knock
back the advance in that area to prevent it initiating it, then bring it back in (relatively speaking) as the turbo brings the boost up (ok,
it's actually lower advance as the boost comes up but the rate of decay is changed).
It's a 3S-GTE with 18psi of boost. I'm working on adding EGT currently as I'm a bit worried I'm being over-cautious on the
advance. Even in stock form it made the manifold translucent after half an hour on the motorway though 
[Edited on 4/3/13 by coyoteboy]
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