Exhaust pops
26 November 2003, 07:57 AM
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I had a Link ECU fitted this summer and mapped by BR which is magic. Lately i have noticed that the car sometimes pops between gear changes as it would if it was overfueling slightly.
Can anyone shed any light as to why this might be happening?
Can anyone shed any light as to why this might be happening?
26 November 2003, 08:12 AM
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Driving harder (hotter exhaust system), change of the fuel mix (I imagine we're into the winter stuff now!). This is assuming it's a decat? In which case, it's not that common to not get pops every so often 
i.e., there's nothing wierd going on...
i.e., there's nothing wierd going on...
26 November 2003, 08:33 AM
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Tripple are coming to the LADS meet on Sunday ?
Details are in East Lancs Subaru thread - Northern section - posted by Trev.
Chris
P.s. You in work today ? Might have a walk over (If its not raining
)
Details are in East Lancs Subaru thread - Northern section - posted by Trev.
Chris
P.s. You in work today ? Might have a walk over (If its not raining
)
26 November 2003, 10:20 AM
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Cheers.
It usually happens when accelerating at a slow rate before changing gear and not necessarily when hot which had me confused. It also never did it when first mapped in the blazing summer days we had.
Full decat, HKS induction, forge d/valve, uprated fuel pump/reg.
Ive emailed Bob so should be wiser when i get a reply.
Towers, first ive heard of it, let me have a look and i'll let you know, fancy another meet though.
It usually happens when accelerating at a slow rate before changing gear and not necessarily when hot which had me confused. It also never did it when first mapped in the blazing summer days we had.
Full decat, HKS induction, forge d/valve, uprated fuel pump/reg.
Ive emailed Bob so should be wiser when i get a reply.
Towers, first ive heard of it, let me have a look and i'll let you know, fancy another meet though.
26 November 2003, 10:56 AM
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Forg DV (if atmos. version) will cause overfuelling after dumping, extra petrol that is not combusted will get onto your exhaust and cause pops n bangs (if very hot even flames).
Dont worry about it, everybody wants it!
Dont worry about it, everybody wants it!
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26 November 2003, 11:01 AM
#8
Not sure about the overfueling because of the BOV.... he has a Link ecu so doesn't use the MAF for fueling (please don't get me started on BOV and overfueling..... less air not more fuel etc).
Is the car set up for half lambda closed loop fueling or is it set for open loop?
Tony.
Is the car set up for half lambda closed loop fueling or is it set for open loop?
Tony.
26 November 2003, 12:35 PM
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If it's tuned by Bob, it'll be 100% open loop (never looks at the lambda, it'll be entirely map look-up based), but a DTA BOV will still cause wierdness.
I'd say that the pops would be expected, except it hasn't done it before. Has anything been changed since Bob did the map?
I'd say that the pops would be expected, except it hasn't done it before. Has anything been changed since Bob did the map?
26 November 2003, 12:39 PM
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Forge d/v is recirc, and like Loc says the Link does away with the MAF so nothing down that line.
I assume you mean is it using the Lambda readings (when not WOT) to have an input on fueling as opposed to giving a set amount of fuel for certain revs and throttle position, if so then im pretty sure it is "half lambda closed loop".
Correct me if im wrong please as id like to have an understanding of it.
Andy, if you have the template then yeah that would be great. I was looking at the shield the other day when i was servicing the car but didnt get round to it.
EDITED BECAUSE I CANT SPELL QOUTE WHOOPS QUOTE
[Edited by Triple X - 11/26/2003 12:42:52 PM]
[Edited by Triple X - 11/26/2003 12:45:14 PM]
[Edited by Triple X - 11/26/2003 12:49:55 PM]
Is the car set up for half lambda closed loop fueling or is it set for open loop?
Correct me if im wrong please as id like to have an understanding of it.
Andy, if you have the template then yeah that would be great. I was looking at the shield the other day when i was servicing the car but didnt get round to it.
EDITED BECAUSE I CANT SPELL QOUTE WHOOPS QUOTE
[Edited by Triple X - 11/26/2003 12:42:52 PM]
[Edited by Triple X - 11/26/2003 12:45:14 PM]
[Edited by Triple X - 11/26/2003 12:49:55 PM]
26 November 2003, 01:50 PM
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Unless Bob has changed his methods recently, I suspect it's permanently open loop (ie never uses the lambda at any point) as the Link smapling rate is a bit, erm, iffy, to put it nicely
But - for understandings sake, closed loop is using the lambda to read information on the mixture so the ECU adjusts the mixture to hit stoich, etc. etc. It will switch off above a certain MAP & go to closed loop (look-up tables) because the gases will have been long-gone so the sampling won't help, unless you like exploding engines. The Link won't use closed loop above a certain point AFAIK, but I can't remember what point that is... but most people don't map the Link as anything other than open loop anyway!
Not sure if that helps, or we're any further on in answering your original question, though
But - for understandings sake, closed loop is using the lambda to read information on the mixture so the ECU adjusts the mixture to hit stoich, etc. etc. It will switch off above a certain MAP & go to closed loop (look-up tables) because the gases will have been long-gone so the sampling won't help, unless you like exploding engines. The Link won't use closed loop above a certain point AFAIK, but I can't remember what point that is... but most people don't map the Link as anything other than open loop anyway!
Not sure if that helps, or we're any further on in answering your original question, though
26 November 2003, 02:43 PM
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Dont you mean it will go open loop above a certain MAP (look up tables)?
Your probably right in that Bob will map open loop, which means the only job for the Lambda sensor is to give a visual aid via the Lambda Link?
[Edited by Triple X - 11/26/2003 2:47:42 PM]
Your probably right in that Bob will map open loop, which means the only job for the Lambda sensor is to give a visual aid via the Lambda Link?
[Edited by Triple X - 11/26/2003 2:47:42 PM]
26 November 2003, 03:12 PM
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The Link half-lambda switches from closed loop to open loop fuelling at 110kPa (0.1bar boost).
I run half-lambda and once calibrated with a wideband I find it pretty good, especially for running slightly lean on cruise (row 3 in a 6 row Link), for closed loop purposes the Link AFR sample rate changes with RPM, ie the faster the engine is running the quicker the ECU is adapting the fuelling.
I also often get pops between gearchanges, although this only really started once I changed the uppipe and turbo.
Andrew...
[edit to say I cross posted with Tony]
[Edited by AndrewC - 11/26/2003 3:14:38 PM]
I run half-lambda and once calibrated with a wideband I find it pretty good, especially for running slightly lean on cruise (row 3 in a 6 row Link), for closed loop purposes the Link AFR sample rate changes with RPM, ie the faster the engine is running the quicker the ECU is adapting the fuelling.
I also often get pops between gearchanges, although this only really started once I changed the uppipe and turbo.
Andrew...
[edit to say I cross posted with Tony]
[Edited by AndrewC - 11/26/2003 3:14:38 PM]
26 November 2003, 04:29 PM
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Triple X,
I use Link as well and got exhaust pops between gear change usually between 4500-5500rpm.Below and above that range,no pops.Pops usually occurs after gearchange and accelerator being stepped on.
I was thinking of changing my dumpvalve atmos type to recir type but since you just mention that you have recir type and you still have pops,maybe now I shouldnt change it.
I too want to get rid of the exhaust pops and retain Link,anyone has any idea,lower fuelling and advance timing?I used to love the exhaust popping away but now with kids around and probably getting older,looking at ways to unpop it.
Chan
I use Link as well and got exhaust pops between gear change usually between 4500-5500rpm.Below and above that range,no pops.Pops usually occurs after gearchange and accelerator being stepped on.
I was thinking of changing my dumpvalve atmos type to recir type but since you just mention that you have recir type and you still have pops,maybe now I shouldnt change it.
I too want to get rid of the exhaust pops and retain Link,anyone has any idea,lower fuelling and advance timing?I used to love the exhaust popping away but now with kids around and probably getting older,looking at ways to unpop it.
Chan
26 November 2003, 07:11 PM
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a leak in the exhaust might make it pop crackle etc as it drags in fresh air when you come off the gas !
mine goes goes closed loop around 2400rpm on the way back down the revs (thinks back, it's been a while since I drove it properly.)
Andy
mine goes goes closed loop around 2400rpm on the way back down the revs (thinks back, it's been a while since I drove it properly.
)Andy
26 November 2003, 09:25 PM
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Isn't that just the switch at 2250 from 'unfueled' to 'fueled'? I think it may well be, because it's cack on mine (so much for 'home-tuning' ) & the thing stops 'engine breaking' & seems to start 'engine accelerating' all by itself 
.
[Edited by nom - 11/26/2003 9:25:46 PM]
) & the thing stops 'engine breaking' & seems to start 'engine accelerating' all by itself .[Edited by nom - 11/26/2003 9:25:46 PM]
27 November 2003, 07:52 AM
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nom,
There is also a point on overrun where the ECU start to try to maintain revs using the ISCV which can cause the car to do the same thing, The Link goes into 'idle mode' ie. maintaining revs using the ISCV below 2100RPM (and other conditions) and can be a real pain when crawling in traffic as the effect is worse in lower gears. I had it cracked by fiddling with the default ISCV duty cycle and the clamp value to make a smooth transition into idle mode but now the weather is colder it seems to have come back.
Andrew...
There is also a point on overrun where the ECU start to try to maintain revs using the ISCV which can cause the car to do the same thing, The Link goes into 'idle mode' ie. maintaining revs using the ISCV below 2100RPM (and other conditions) and can be a real pain when crawling in traffic as the effect is worse in lower gears. I had it cracked by fiddling with the default ISCV duty cycle and the clamp value to make a smooth transition into idle mode but now the weather is colder it seems to have come back.
Andrew...
27 November 2003, 12:11 PM
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Tripple - bring your electrical testing thingymebob with you on Sunday.
My MPG's droping faster than the wifes nickers at a westlife concert.
We might have time to have a quick Lambda voltage test, unless we / you can "do it" one lunchtime ?
Chris
My MPG's droping faster than the wifes nickers at a westlife concert.
We might have time to have a quick Lambda voltage test, unless we / you can "do it" one lunchtime ?
Chris
27 November 2003, 12:36 PM
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Will bring it on sunday, if you can get your footwell ready. Going to treat myself to some finger licking good stuff tommorrow dinner.
And no that doesnt include anyone dropping there knickers!
And no that doesnt include anyone dropping there knickers!
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