VVTi BPU AFR question

Had BPU bits fitted today, garage reported AFR of 13 at around 1 bar for a second or so before backing off. We dont yet know what max boost is, as the chap backed off PDQ. I picked her up and took it easy on the way home. My question is simply this, how do you find out if it is running lean at WOT without actually running it at WOT... what might the process be ?

Stock engine / stock intake / running on V-Power

Double de-cat with 1.2 bar restrictor ring

10 year old smic at present

Walbro fuel pump

NGK platinum race plugs

GGreddy FCD

AEM wideband AFR gauge

Boost gauge

Just had service, fuel filter fine.

AFR at idle sits 'tween 14.6 / 15

AFR at cruise same

Any advice appreciated.

Odd, the VVTis normally run very rich after decat. I'm basically the same setup as you except for the fuel pump...I wonder if it's supply enough fuel?

Hmmmm.

Please tell me AFR at 14 / 15 is ok for off-boost commuting in the meantime ? I know thats near enough stoich, but I'm a little nervous right now.

Might be worth changing the fuel filter,or even go as far as having the injectors cleaned and flow tested, does seem a Little odd, normal fuel map is silly rich,what was being used to measure AFRs? sorry should have been paying more attention:innocent: are you sure its calibrated right? although the idle and cruse seem to bare that out, don't panic as the knock sensors should have done there job if there was knock present.

They checked fuel filter, almost new.

AFR's taken from new AEM wideband, I'll ask them about calibration tomorrow.

So far, questions I have to answer...

Question over fuel delivery from pump ?

Question over fuel filter ?

AEM calibrated correctly ?

Injectors flowing equally / correctly ?

Knock sensors working ?

Is it worth giving the ECU a reset?

Is it worth giving the ECU a reset?

From where I'm sitting, it cant hurt

From where I'm sitting, it cant hurt

Can you reach? If not, then it probably will hurt with all that stretching

Hmmmm.

Please tell me AFR at 14 / 15 is ok for off-boost commuting in the meantime ? I know thats near enough stoich, but I'm a little nervous right now.

14.7 is spot on isn't it? I'd say the gauge is working ok.

It should be rich on startup then settle down to idle around 14.5 and flick to lean when coming off the throttle.

With your foot firmly planted it should be 10- (basically rich off the gauge)

14.7 is spot on isn't it? I'd say the gauge is working ok.

It should be rich on startup then settle down to idle around 14.5 and flick to lean when coming off the throttle.

With your foot firmly planted it should be 10- (basically rich off the gauge)

Engine was warm when picked up, I'll look at start up AFR tomorrow.

Idles fine(ish), it cycles between 14.6 up to 15.

It goes off the scale lean on overrun.

I wont try WOT just yet.....

From what I've read, yes it is. It runs lean off the scale on over-run, but I've read that is normal too.

Perfectly normal Ewen.

When it's idling it'll fluctuate between 14.0 and 15.5 (normally swinging up and down as the ecu is constantly tqeaking the fueling

On partial throttle and light boost, it'll normally run around 13.0, but as boost and rpm rise you should be seeing around 11.0 (normally much lower as they run rich on WOT and high rpm).

The point to watch it is when it's in the building boost on the 2nd turbo on high load (say 4th gear upwards around th 4k to 5k rpm point, this is where they normally get a nasty lean spot above 1.1 bar.

Thanks so far guys....

Before I see for myself what happens on WOT, anything else that could cause lean running that the garage could look at for me ?

They were worried about the FCD...not sure if it was because it was an unknown to them or just that they didnt like it...but as CW told me, it would be pretty hard to get wrong...wouldnt it ?

The Greddy one isn't the type that clamps the signal rather than linearly increase fuel?

The Greddy one isn't the type that clamps the signal rather than linearly increase fuel?

As the VVTI is MAF based I wonder how it differs from the MAP based cars? BPU works okay on the MAP cars because the sensor can't read above 1.1bar so in terms of fueling it makes no odds whether it's clamped or not. The only drawback of the greddy is that it completely removes any boost cut and has no safety margin if it overboosts

The Greddy one isn't the type that clamps the signal rather than linearly increase fuel?

That I wouldn't know, but its from CW, so I'm assuming its a safe bet. I'll get the garage to confirm the wiring.

It was the HKS that was the bad one I was thinking about.

Greddy seems cool. See http://www.mkiv.com/techarticles/bcc/bcc_install/bcc_intro.htm it mentions turning a screw.

It was the HKS that was the bad one I was thinking about.

Greddy seems cool. See http://www.mkiv.com/techarticles/bcc/bcc_install/bcc_intro.htm it mentions turning a screw.

Thanks Pete...I'll pass this on.

Greddy definitely still has a cut, it's the one that caps the signal and is adjustable via the screw that Pete mentions, and a multimeter IIRC?

All your findings sound pretty much spot on so far, the reason for the silly lean on overrun is that the injectors shut off and your engine is just pumping air. Not sure what the AEM gauges show, but my Innovate (which seems to have a much broader range) switches from Lambda to % Oxygen in the air at that point.

This is why, contrary to popular opinion, coasting down a hill in gear is much better for your fuel economy than coasting with the engine idling

Although mine is not stock ecu I won't see lower afr until it really bites. At .8-1.0 bar on a T67 I see 11.6 and it only bites to 10.6 when you are really pulling at lower revs on high boost.

Cruise I see 14-15, and super lean over -run

your vvti has det sensors and fbw throttle so if it even thinks something bad is going to happen it will shut the throttle way faster than you can, and the fbw is pretty sensitive from my experience.

When my ecu re-learns on new turbos I try to ease the mapping in, but constantly saw high afr's as I wasn't pushing - soon as I push down they go. So I don't think that you have a problem, other than too much information!

injectors flow tested...? good idea in any car, but they would all have to be nailed to significantly alter fuelling, and that's unlikely.

are you seeing high afr on for a long period on hard bite (more than 1-2 seconds)?

think yourself lucky to have fbw and det detection because in theory you car is unexplodable!

VVTi's run very rich as stock, to stop the cats melting. You should have plenty of ceiling de catted. Try nailing it in 4th and see what the mixture is. Not wanting to open a can of worms but some AEM meters don't tally at all with my NTK sensored Motec PLM, and I know which I believe...

So I don't think that you have a problem, other than too much information!

 

injectors flow tested...? good idea in any car, but they would all have to be nailed to significantly alter fuelling, and that's unlikely.

 

are you seeing high afr on for a long period on hard bite (more than 1-2 seconds)?

 

think yourself lucky to have fbw and det detection because in theory you car is unexplodable!

Thanks Mike and the others....

I understand all thats been posted....No, I havent pushed the car up to full boost at all, the chap at the garage did briefly and backed off as a precaution. He has just warned me that in his opinion it was running too lean at high boost. I havent tried it myself, as I cant get my head round the issue of seeing if its going to det at full boost by actually risking det to prove the point.

A question... is the det detection set up on a VVTi easy to test to make sure its working ?

Chris, have you had much experience of comparing the Innovate widebands? When I researched in to getting one, the information I found certainly favoured the Innovate over the AEM, but I doubt it's accuracy compared to the more exotic equipment?

The Toyota map runs the first turbo pretty lean as stock, 13:1 AFRS until 4000rpm are normal. How far up the rev range did the guy take it? This is for non-vvti, not sure if it was changed for that model or not.

You can see the FBW shutting the throttle but only by datalogging the voltage on the TPS.

-Ian

Sorry, never compared those. Most AEM's seem quite accurate, it's just the odd ones that give daft readings. Could be sensor or gauge, don't know. Picked up my PLM for sensible money, so I tend to stick with it as it interfaces with the Motec stuff on the race car and my Skyline.

Mine isn't VVTI but this is what my AFR's tend to do:

http://www.mkivsupra.net/vbb/showthread.php?t=142146&highlight=afr