Ian C Posted June 6, 2005 Share Posted June 6, 2005 So, as a point of interest, a discussion on AFrs vs boost vs turbo type/size vs rpms. Airflow fudgers fight the stock sequential map between 3000 and 4000rpm as it does some pretty fruity things during the spoolup and transition phases. However, I've noticed on stocker dyno plots of the AFRs that Toyota seemed happy with 14:1 or thereabouts AFRs until the second turbo came online at 4000rpm Another reason it's a tad tricky to bludgeon 12:1's out of it with a single turbo and an airflow fudger So I was wondering - do you not need 12:1 AFRs under say 4000rpm? Is the ideal forced induction AFR of 12:1 considered overkill at lower revs? Could you run 14:1?! Maybe 13.5:1 is perfectly acceptable? If you have a fast spooling T61 say, and it can kick out 1.2bar of boost before 3500rpm, surely you'd need the rich AFRs as it's not a dinky stock turbo - or is this not the case as it's low-ish rpms? Or is it a factor of turbo size vs rpms, the smaller the turbo, the less fuel you need until you get up the rev range...? Toyota cleaned up the transition hugely with the VVTi, it's got it's own idiosyncrasies for airflow mapping but not as bad as the non-VVTi. The AFRs hit 12's early and don't wig out between 3500 and 4000. I don't know why they changed the behaviour as no MkIV's before the VVTi blew up from underfuelling because of the stock map... Any thoughts? -Ian Link to comment Share on other sites More sharing options...
TLicense Posted June 6, 2005 Share Posted June 6, 2005 Hell Ian, I'm finding it hard enough to get anyone to tell me what kind of AFR's I should be mapping for, let alone having a discussion about them! Link to comment Share on other sites More sharing options...
Ian C Posted June 6, 2005 Author Share Posted June 6, 2005 I aim for 11.8 I think 12.5s are good for power but too scary close to running lean if anything goes odd. Anything under 11.4 I consider too rich. I'll allow 13's at real low boost like 0.1 to 0.3, but shoot for the 11.8s above that. And I try and do it at any rpm site. -Ian Link to comment Share on other sites More sharing options...
JohnA Posted June 7, 2005 Share Posted June 7, 2005 There are many factors involved when calculating the ideal AFR. For example, maximum power on my calibra I would get at 14:1 When running 5 extra psi (everything else the same) I would get it at 12.5:1. You see intercooling/ignition advance were perfect in the first case, but not in the second one. By reshuffling water/methanol injection I would end up with max power at 13.5:1 in the latter case. So there is no absolute ideal for everyone, but the better the balance inside the cylinders, the closer you'll be to stoich. Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 Right have found the following: Car idles much better on 13.5 cruise between 14.5 I have her set to 11.5 upto 18 psi where she gradually will drop to 11.3 depending on the amount of boost IMHO I would want it slightly richer than 11.8 for long motorway or high speed runs. Link to comment Share on other sites More sharing options...
TLicense Posted June 7, 2005 Share Posted June 7, 2005 So what kind of AFR's are you guys idling at? Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 Tony like I said, my car likes 13.5 much more than Stoich Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 There are many factors involved when calculating the ideal AFR. For example, maximum power on my calibra I would get at 14:1 When running 5 extra psi (everything else the same) I would get it at 12.5:1. You see intercooling/ignition advance were perfect in the first case, but not in the second one. By reshuffling water/methanol injection I would end up with max power at 13.5:1 in the latter case. So there is no absolute ideal for everyone, but the better the balance inside the cylinders, the closer you'll be to stoich. Are you saying you were running the car on boost for max power @ 14:1? & that you leaned here out from 12.5:1 to 13.5:1 on boost ! Link to comment Share on other sites More sharing options...
Ian C Posted June 7, 2005 Author Share Posted June 7, 2005 Mine is still controlled pretty much by the stock ECU so it idles at 15:1. I can't fool it as it always uses closed loop to pull the AFRs back to that even if I feed it more airflow and therefore more fuel. It's not smooth - big injectors and wide cams make sure of that. Terry - do you target those AFRs no matter what RPMs you are running? If you hit 1 bar at 3000rpm you are still aiming for 11.5? -Ian Link to comment Share on other sites More sharing options...
TLicense Posted June 7, 2005 Share Posted June 7, 2005 Oh sorry Terry, missed that. OK so I'm about right at idle, and IIRC, running reasonably lean, as I think has been mentioned before at WOT. So if you've got say 13.5 at the bottom left, and 11.5 at the top right, do you just interpolate between the two to fill in the rest of the table? Off boost are you worrying much about the AFR's as they don't really have much effect? Also last question, when tuning for accel fuel, do you only add enough fuel to stop the AFR's dropping as TPS increases. Link to comment Share on other sites More sharing options...
Alex Posted June 7, 2005 Share Posted June 7, 2005 Hmmm...I've never tried to get mine to idle rich...thought that was bad. (I know it's not massively rich). My CLC seems to sort itself out what ever I do I might look at richening it slightly as this will help some idle conditions. Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 No it ramps up dependant upon the boost Chis, Difficult to say at 1 bar but probably around 11.8. BTW new test for Alex, the car is in positive boost now at 1600 rpm, and makes 3psi by 2000 rpm, top gear. Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 Hmmm...I've never tried to get mine to idle rich...thought that was bad. (I know it's not massively rich). My CLC seems to sort itself out what ever I do I might look at richening it slightly as this will help some idle conditions. I am not sure you will be able to richen her up with the stock CLC still controlling things, but the engine sounds much happier slightly richer at idle. I am still aiming at stoich on cruise Link to comment Share on other sites More sharing options...
Ian C Posted June 7, 2005 Author Share Posted June 7, 2005 No it ramps up dependant upon the boost Chis, Difficult to say at 1 bar but probably around 11.8. Righto so you increase fuelling depending on boost, fair enough I do that myself but I've got 11's by the time it's at 0.5bar. You don't make it rev dependant though - good That's also what I've been doing I think I shall continue to avoid 14:1 AFRs when on boost like the plague... BTW new test for Alex, the car is in positive boost now at 1600 rpm, and makes 3psi by 2000 rpm, top gear. I reckon you've put a diesel engine in -Ian Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 Oh sorry Terry, missed that. OK so I'm about right at idle, and IIRC, running reasonably lean, as I think has been mentioned before at WOT. So if you've got say 13.5 at the bottom left, and 11.5 at the top right, do you just interpolate between the two to fill in the rest of the table? Off boost are you worrying much about the AFR's as they don't really have much effect? Also last question, when tuning for accel fuel, do you only add enough fuel to stop the AFR's dropping as TPS increases. Tony I have no working knowledge of the AEM mate. 11.5 or slightly below should be your on boost target, slightly leaner up to say 10 psi, at cruise you want approx. stoich. This is really simplified but you get the jist. Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 I reckon you've put a diesel engine in -Ian Ah you got me now.... LOL I am sure running 14:1 at WOT will make great power for 2-3 seconds, but I wont be trying it anytime soon Link to comment Share on other sites More sharing options...
Alex Posted June 7, 2005 Share Posted June 7, 2005 In top gear...No probs....timing advance to the rescue Ian grab the det cans - we have a challenge There will be a point at which the CLC can't cope (I would have thought) need to find that point. Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 BTW Chis, the target is based upon REVS & BOOST. Imagine your 256 cell fuel table, vacuum to boost, I have target AFR's set in every cell Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 In top gear...No probs....timing advance to the rescue Ian grab the det cans - we have a challenge There will be a point at which the CLC can't cope (I would have thought) need to find that point. Enjoy ..... Alex yeah if the fuelling is too rich the CLC cant cope, but if yours acts anything like mine did with the MAP ECU its the sublime to the ridiculous, and the VVTi CLC works VERY well over a very wide range. Be very interested if you can stop her going into CLC at idle and get a stable idle in the mid 13's Link to comment Share on other sites More sharing options...
Ian C Posted June 7, 2005 Author Share Posted June 7, 2005 BTW Chis, the target is based upon REVS & BOOST. Imagine your 256 cell fuel table, vacuum to boost, I have target AFR's set in every cell OK, but for 1 bar of boost you target about 11.5:1 even at 2500rpm? I'm just trying to understand why Toyota ran such 'lean' AFRs on the first turbo and during the transition point. And got away with it -Ian Link to comment Share on other sites More sharing options...
Guest Terry S Posted June 7, 2005 Share Posted June 7, 2005 That is the way mine is set up from memory, but will need to check now you PITA, I cant access the target AFR maps so need to go testing. I know that on light boost say 3 psi she is still in the very high 12's Link to comment Share on other sites More sharing options...
JohnA Posted June 7, 2005 Share Posted June 7, 2005 Are you saying you were running the car on boost for max power @ 14:1? & that you leaned here out from 12.5:1 to 13.5:1 on boost ! Yes, theory and practice can be at odds sometimes, can't they? Depending on VE, charge temps and ignition mapping, the 'ideal' AFR can vary a lot. (It's the max torque AFR I'm talking about) Link to comment Share on other sites More sharing options...
Dave S Posted June 7, 2005 Share Posted June 7, 2005 struggling ATM to lean out above 4500 rpm, reading 10.5 afr ,running out of adjustment on emanage map...am I right in thinking that I may have to resort to using the global injector adjust to give me enough control.... Terry..hi m8 can you suggest a 'test track ' cant get much above 5500 wot round here before someone gets in the way!! cheeers Dave S Link to comment Share on other sites More sharing options...
Alex Posted June 7, 2005 Share Posted June 7, 2005 Dave, how big are your injectors? What's the rest of your setup? Link to comment Share on other sites More sharing options...
Dave S Posted June 7, 2005 Share Posted June 7, 2005 Alex...800's ,aeromotive fpr , walbro , T61 , Blitz ecu ( could be the culprit! ), emanage/E01, ...... Link to comment Share on other sites More sharing options...
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