4AGE ST -What elements control air/fuel mixture? 20HP+ down from stock. 12.5 - 10.5:1

[Patryn999]

I have a stock Silvertop 20V (AE101 Levin) and I recently had it dyno'd at a poor 75kW (101HP). Looking at other people's results at stock I have lost a good 20HP+, the thing is the mixture starts out at about 12.5:1 and decreases to about 10.8:1 at 7000RPM.

I thought maybe it was the AFM, so I got a stock one and it was even worse (I have a simple mixture guage connected to a new standard o2 sensor in exhaust) and I had to adjust it a 1/4 turn just to get it to run semi ok! (about 15-20 clicks). The part numbers and everything checks out, and I checked it with another just in case, does the same thing. Thing is it still blows out to past the sensor's ability to read when I put my foot down, but I cannot change any further or else it stalls idling. (Yes I do have the factory setting marked, so can move it back).

I checked the TPS using the Blacktop manual (I'm hoping is the same) and it meets specs so I don't think its that. The plugs are new and gapped right and the part numbers on the ECU check out to be right (manual AE101).

Additional Info:

• I've checked the timing, which sits at about 10deg BTDC in diag mode.

• VVT wasn't working previously, replaced a burnt out resistor in ECU and now gets voltage. timing mark disappears when you hit 4.5kRPM so i think it works.

• The oxygen sensor's only about 10,000 km old.

• System shows no error code, and seems to run in closed loop mode while cruising.

• Temp sensor is within specs (just).

I remember the previous owner saying he replaced the injectors with the blacktop ones as they are more reliable, however when I looked up part numbers they are the same? Is there anyway you can accidenatlly goober a swap-in replacement? (anythings possible!).


I'm out of ideas, can anyone help please?

Cheers,
Carl.

[YLD-16L]

Most stock ecu controlled Toyotas dive into the low 11 high 10 afr on WOT at full load, nothing unusual there.

75kw at the treads for a silver tops not an unexpected result either. You have to remember there is variation between dynos everywhere so just looking at what others have achieved on some dyno somewhere and yours not matching up is nothing to worry about.

The stock Toyota factory power claim for the 20V is on the optimisitic side too.

Unless you can run back to back against another stock silver top on the same dyno I wouldn't be comparing to anyone else.

[Patryn999]

Yeah, had one there that got 89kW at the wheel, with pretty similar setup. He still had stock exhausts, but otherwise standard with pod intake with shield.

He seemed to be running at 14 - 12.5/13:1 for the whole range, but maybe his has been altered in some way he doesn't know about.

Cheers

[YLD-16L]

You'll definitely pick up that power you are after with mixtures in the mid 12's to 13 flat, I've not seen a stock Toyota though that didn't run pig rich at WOT so your's is more the norm than the other example you noted.

Good luck with it.

[Hiro]

And of course there's the possibility that you've just got a dog. I've seen _plenty_ of 20v conversions that have mysteriously lost a lot of power in the swap, plus even "low km" ones have often not been looked after in Jap-land and thus could use a full rebuild. A good sign of how well it has been looked after is to take the cam covers off - a well serviced engine should be relatively clean, but a lot of them are blacker than a BBQ after Christmas lunch.

[gixer]

My completely stock AE111 which I've had for a number of years now runs around 12.8:1 on our Mainline dyno. I dynoed when I first got years ago with about 60K on clock and now with nearly 100K's on clock still same power and same A/F.

[Patryn999]

The part number on the injector I just removed says : 23250-16140

I get the feeling that this ain't the right injector for the AE101 4age.. The part numbers don't check out with what's on this site, however if anyone's good at part lookups could you check that they're not just compatable replacements before I get too one-sided?

Thanks heaps.
Carl.

Further investigation seems to suggest so. Places rate the injector I took out as 310cc/min to 340cc/min. And documents say that ST should be 295cc/min. Maybe I'm barking up the wrong tree here but do you peeps think this difference would affect it much?

[Patryn999]

Also if someone knows, when you hit WOT the ECU moves into a open-loop control. What sensors does it still use to calculate mixture? i.e. it could just get away with using the TPS and rev count with internal mappings.

Wondering if the AFM is still actually utilized in WOT or if only used under normal/cruise conditions.

I'm considering making some sort of micro-based intermediate to fake the signaling to ECU in order to correct at high revs.

[shelldrake]

What has been said previously regarding variances in dynos is probably fair. Plus the unknown factor of the specific engine you have. You have no real reference unless you know someone with an identical setup, similar kms, who can run their car on the same day, with the same engine configuration, when the ambient temperature is about the same. Also, a tune up and service of both motors prior to maintain the accuracy of the test. There's probably more things to consider....But the point is, don't stress about 80ish KW. It's just a number. If you want something that reads 150kw on a dyno, tell the dyno operator.

Seriously though, if you want a performance figure, build a performance package with a known quantity for a range of power you would be happy with.

On a slight tangent - I'm researching target A/F ratios for my 20v at the moment. I'm told these motor love to run lean... Anyone have first hand experience in tuning these motors and have results of what's been successful?

[gixer]

On a slight tangent - I'm researching target A/F ratios for my 20v at the moment. I'm told these motor love to run lean... Anyone have first hand experience in tuning these motors and have results of what's been successful?

Ok, what I have noticed doing both ST and BT, the ST's get max power at about 13.0:1 and the BT's like it richer.

[shelldrake]

Under full throttle all the way through?

[Patryn999]

Under WOT, if its cruising the ECU tracks back to a good air/fuel mixture. I can see its working nicely in closed loop.

Alternately if the AFMs back to factory settings it wont enter closed loop mode (as i suspect the mixtures too far out with the different injectors). But once you reduce this to compensate it'll work fine until you put the boot down.

Thinking the fuel-pressure might also be out. Planning on getting a rising rate fuel pressure regulator (1:1) which would seem to match the vacuum i just measured at manifold to the idle/WOT fuel pressure in BT manual. Also should be able to compensate for the oversize injectors (flow is linearly proportional to pressure) and is the same price.