AFR Readings and RPM signal for HKS VI

Hi All

So I am nearing the end of my full BPU and engine rebuild and have hit a couple of snags maybe more knowledgeable people than me can help with:

1) I have my AEM AFR all installed now but with a half bpu car at 1bar (Restrictor and CW FCD installed now) it seems to be running at about 16.25 on idle which I think is lean does it need a set up or is that ok? When on WOT once I lift off the gauge goes to 4 minus symbols for a couple of seconds then starts reading again, is this normal too, I guess the difference between WOT and none is so rapid the gauge cant keep up for a couple of seconds? It was installed by a tuning company so i am figuring it is tickety boo install wise.

2) The final stage of my BPU is the HKS EVC 6 IR Boost Controller. This is mostly installed (and off) but my mechanic says it needs an rpm point and he cant find one stable enough, he says he can go into the back of the rev counter if he has to but doesnt want to and is currently waiting on another tuner to come back to him witht he best way forward, have eny of you experienced this and where is the best stable rpm signal on a TT Auto to plumb into? I think once this is done it will be full BPU but cant quite jump that last hurdle without help from you guys on here hopefully!

Not my area, but some info here to start with......

http://www.mkivsupra.net/vbb/showthread.php?210243-Safe-margins-for-EGT-and-AFR

When you lift off, the ECU will cut fuel to injectors whilst you are in over run until you next re-apply throttle. Hence why your gauge reads --- (super lean), as there is no fuel being supplied. This is normal behavior.

If you are experiencing rich or lean spots when coming off the throttle or when going on throttle sharply, then this can also be considered somewhat normal. It usually takes 1-2 seconds for a gauge to stabilize after a sharp change in throttle. 4 seconds seems strange however.

16.25 on idle seems a tad high. IIRC you recently had bigger pistons and cams? put in, this will affect your engine's VE and change fuel requirements, so the fuel that the computer is expecting to put in may not be 100% suitable for your new setup. 16 on idle won't be the end of the world though. So long as you aren't reading lean on boost then shouldn't be an issue.

Fuel cut defenders can also mess around with AFR's depending on how they fudge the map signal.

Some wideband sensors require free air calibration before installation. Could also be a calibration issue throwing off AFR's.

RPM point for your boost controller can be tapped into from the ECU using either pins IGT or IGF depending on what signal the controller needs.

When you lift off, the ECU will cut fuel to injectors whilst you are in over run until you next re-apply throttle. Hence why your gauge reads --- (super lean), as there is no fuel being supplied. This is normal behavior.

 

If you are experiencing rich or lean spots when coming off the throttle or when going on throttle sharply, then this can also be considered somewhat normal. It usually takes 1-2 seconds for a gauge to stabilize after a sharp change in throttle. 4 seconds seems strange however.

 

16.25 on idle seems a tad high. IIRC you recently had bigger pistons and cams? put in, this will affect your engine's VE and change fuel requirements, so the fuel that the computer is expecting to put in may not be 100% suitable for your new setup. 16 on idle won't be the end of the world though. So long as you aren't reading lean on boost then shouldn't be an issue.

 

Fuel cut defenders can also mess around with AFR's depending on how they fudge the map signal.

 

Some wideband sensors require free air calibration before installation. Could also be a calibration issue throwing off AFR's.

 

RPM point for your boost controller can be tapped into from the ECU using either pins IGT or IGF depending on what signal the controller needs.

Thanks this is superb info, so I would imagine the gauge is right but the mixture is lean, I guess a tuning company can remap it to 14.7 is that how it works or (excuse my constant ignorance) is there a manual way of doing this myself? I did indeed have UK cams and plus 1 forged pistons etc put in and to my knowledge the mapping etc is stock. I guess making it slightly richer will increase power surely?

UK Cams and forged pistons with a stock map? Is the car running on a stock ECU or aftermarket/piggyback??

UK Cams and forged pistons with a stock map? Is the car running on a stock ECU or aftermarket/piggyback??

Long story short engine had black death so needed pistons reboring making plus half ones the only way to go so thought I may as well go forged whilst I am doing it as they are better, stronger and fit the plus half. UK cams and JDM cams are almost identical according to my mechanic and many people on here and JDM cams are almost impossible to get now. It was a choice of one and here we are. Its a stock ECU as I'm only going BPU I dont want to go any higher so getting into ECUs is surely unnecessary, just maybe needs a remap?

Why are you concerned about the uK cams T2 with forged pistons, have I missed something? I tok a lot of advice on this and everyone said it was the way to go?

There is no such thing as a "remap" on the Supra, like you would on say a modern BMW. There are a few ways around this however:

Back in the day there were a select few Japanese tuning companies that could ROM tune the factory ECU, which required certain equipment that is no longer in circulation these days. No one in the UK 25 years later can replicate this service either as far as I'm aware. So no go there, the factory ECU is untouchable in that sense.

Typically if you want to make small adjustments to the factory ECU, such as fueling, your best bet would be to wire in a piggyback controller which alters the signals that the ECU sees. This technology is getting on in age now as well, but is proven to work.

The other option is to get a standalone ECU, which in my opinion is by far the best solution. The freedom it gives is great, not having to guess what the factory ECU is up to.

That said if you have absolutely no intention of ever going for more power, then perhaps piggyback is the best solution. Some piggybacks you can look into Greddy eManage, AEM FIC, EMU DET3, Apexi SAFC.

Although the changes to displacement are minor when going to one size up pistons, mixed with camshafts that are slightly more aggressive than what the JSPEC ecu is programmed to deal with, you can potentially run into the situation you are in now.

All of the above may be overkill anyway. I'd get your tuner to check that engine is not knocking whilst boosting, and if car drives around fine then you should be good to go.

He's took it out and at 1 bar says its fine - to me it feels like so much power is going through it but strong you can almost feel the boost now throughout and especially after when its venting afterwards, similarly to an audible response on the BOV I had in my previous MkIV. Only feels good. So I need to watch out for it going lean on WOT that assumedly is a sign of damage in some capacity or faulty setup? I'll pass on the RPM data and get him to do that, he said it could be done form the rev counter but preferred another way for some reason.

The reason I am not going for more power is twofold, most people who go beyond BPU seem to say they regret it the car is less nice to drive day to day and becomes jerky apparently, and I have driven a big single and see what they mean albeit it is more powerful, but the big deal is the autobox, I want to stay auto and I've been told 550 is about the limit it can run so much beyond BPU is pretty much out of my handsanyway I guess? Has anyone dropped a different autobox in a JDM to go higher power?

There is no such thing as a "remap" on the Supra, like you would on say a modern BMW. There are a few ways around this however:

 

Back in the day there were a select few Japanese tuning companies that could ROM tune the factory ECU, which required certain equipment that is no longer in circulation these days. No one in the UK 25 years later can replicate this service either as far as I'm aware. So no go there, the factory ECU is untouchable in that sense.

 

Typically if you want to make small adjustments to the factory ECU, such as fueling, your best bet would be to wire in a piggyback controller which alters the signals that the ECU sees. This technology is getting on in age now as well, but is proven to work.

 

The other option is to get a standalone ECU, which in my opinion is by far the best solution. The freedom it gives is great, not having to guess what the factory ECU is up to.

 

That said if you have absolutely no intention of ever going for more power, then perhaps piggyback is the best solution. Some piggybacks you can look into Greddy eManage, AEM FIC, EMU DET3, Apexi SAFC.

 

Although the changes to displacement are minor when going to one size up pistons, mixed with camshafts that are slightly more aggressive than what the JSPEC ecu is programmed to deal with, you can potentially run into the situation you are in now.

 

All of the above may be overkill anyway. I'd get your tuner to check that engine is not knocking whilst boosting, and if car drives around fine then you should be good to go.

Well I personally think you need to sack your mechanic as there is a big difference between JDM and UK intake cams as per below (if you have changed just the exhaust cam then thats ok then). A change this big with the difference in forged piston would almost definatly need custom mapping, I would be taking the car through the rev range and making note of the AFRs you see then do the same at low revs coming onto boost. I would anticipate its running lean and will only be a matter of time before you have another engine issue!

J-spec Cam Specs

Intake Cam - 224°, 7.88mm lift

Exhaust Cam - 233°, 8.4mm lift

UK Cam Spec

Intake Cam - 233°, 8.25mm lift

Exhaust Cam - 233°, 8.4mm lift

So how about it guys is T2 right. Swampy and many others have said they are almost identical so who is right here?

I just did a search and a couple of sources have the UK and JDM intake cam as being different. Prob best to ask your mechanic which Cams he has changed, intake, exhaust or both?

I bought both cams but the general consensus here was the difference is so minimal it's fine. The mechanic also looked into tolerances eye and said it was too. The forged parts are bigger for plus half but have the same other dimensions so surely should be fine? The rev problem looks to be achievable thanks to that info received on here so after that it's just figuring out if the FAR figures are within acceptable parameters at 1.2

As soon as you start changing internals for different parts no matter how small the margins with a Stock ECU its not going to be able to adjust the fueling enough to accommodate as it expects set parameters and whilst it can adjust based on the O2 sensors its only small amounts.

The different size and shape of the forged pistons will change the cc in each chamber and having intake cam with more lift and at different degrees will put more or less fuel/air in the Cyl.

As your in the 16 AFR at idle id say its made a difference and needs mapping, at idle thats not really that much of a risk but if you are also lean on throttle and into boost that is an issue and is potentially risking the engine.

Exactly what T2 has said.

It's likely you've altered the compression ratio and duration of air/fuel entering the chamber. Your ECU won't know this and has no way of compensating. Surely the easiest fix is a standalone and a remap?

I'd more question why he's doing power runs on a newly built engine. Most builders recommend a 1000mile off boost run in

I'd more question why he's doing power runs on a newly built engine. Most builders recommend a 1000mile off boost run in

Hi Ric, already done 1200 miles off boost run in. I'm stupid but even I'm not that stupid. Engine compression is perfect we tested all the normal things very recently as part of the final inspection after the run in period ended and its had a new fuel pump, all filters, fuel lines and even the turbos had been removed and checked. Fortunately I'd spent a fortune on it before the engine went so it was pretty obvious the car itself was healthy now and it was setup or settings. I had a bit of a brainwave after I went on here and got all the good advice though that the petrol in it had been sat there for 5 months whilst all the rebuild etc went on so I took out all that I could and totally filled it with new V Power and now the AFR is reading in the 14s at idle which is perfect it seems?

I took it for one quick blat up the bypass after it was warm this morning and it never went lean on first or second turbo and returned immediately to 14s at the next junction in idle and at worst only goes early 15s now on idle it seems. I think its obvious I understand very little of how this all works but whether it was coincidence or the petrol had just gone down in 'power' I dont know. Maybe tomorrow it will all be wrong again but it seems to be perfect. Feel free to comment on this ridiculous situation.

As a final question to all you good people before I hopefully go off to some sensible and reliable Supra motoring (I wont be flooring it everywhere dont worry for my car this was just a test period) just before I set off for my fact finding mission to see if it had all worked I had the 'genius idea' (please dont judge me too harshly) that I could test it in situ without moving by flooring it and at WOT with no load at all it did go high lean, I assume it just confused the hell out of the ECU and this just happens so is this ok on an AFR? As I say, straight after when driving on WOT it showed nothing but perfect readings but I thought I would just ask you whilst i have you all gathered and having a good chortle at my incompetent bumbling.

I don't thing we can comment any more until we know exactly what AFR is at idle, say 2k, 4k and 6k static, AFR will bounce around as you come on and off throttle thats normal.

then the same coming onto boost but not full boost as I dont want to be seeing the next post as my engine went bang. Suspect its running lean - AFRs on boost at WOT should be the mid to low 11s. going into the 10s is too rich and backing into the high 12s is too lean. Its on load (as you are coming on boost and WOT) thats really important that it gradually increases the fuel and the AFRs come down. If as you put more load on and up the boost and get close to WOT and the AFRs are not getting into the 11s then Stop.

I cant remember from the syvecs target tables what mid load targets where but suspect they are in the 12s

The only one I can remember is WOT which was 11 point something so it sounds like its bang on hopefully I rang one of my brothers mates who does all this too and he said it could go late nines at WOT eventually if you keep it open but shouldnt be able to go any higher, sound about right?

The only one I can remember is WOT which was 11 point something so it sounds like its bang on hopefully I rang one of my brothers mates who does all this too and he said it could go late nines at WOT eventually if you keep it open but shouldnt be able to go any higher, sound about right?

Mine used to misfire badly if it got into the 10s so 9s I doubt it would run properly

Yes I think with everyone's help on here I may have cracked it, thanks so much T2 and everyone, I'll report back if I get any other issues.