silvertop or blacktop?? what the?? 4age experts help pls!

[deltathing]

Indulge me people and see if you can help me solve this problem.
i have recently purchased an ae92 with an apparent "hybrid" 20v 4ag with a blacktop head and silvertop bottom end. herein begins the confusion. i have determined that indeed it is an ae111 blacktop ecu, however the timing map does not seem to suit the engine. obviously it is running a map sensor and not afm, however when the vvt solenoid is connected the motor struggles to rev over 4000rpm.
Is it possible that the previous owner, or myself, was told a fib in regards to the engine configuration and indeed that it is an entire *silvertop* motor running on a *blacktop* ecu? without the vvt solenoid connected the motor will run quite smoothly however in the range of 2-4krpm it is fairly retarded. Mechanially the motor sounds perfect, almost like an unopened motor, not a hybrid of different components put together by a shonky mechanic.
Another interesting fact is that the rev limiter comes in at 7,800rpm, which is silvertop specification if i'm not mistaken. Is this limit controller by the ECU or a sensor on the motor? I am quite confused. I have a suspicion that this motor is in fact a silvertop with all blacktop sensors and ecu. Is it possible to shed some light on my rather confused subject?? Any advice much appreciated.
Cheers

[deltathing]

anyone??

I'm really trying to solve this problem, even if i have to put an airbox, afm and silvertop ecu on the motor to get it to run as factory.

Another note is the ecu is not throwing up any diagnostic errors and is not in diagnostic mode.

thankyou.

[gixer]

If you are trying to see if it's a BT motor, check the BT motor differences, such as;
hydraulic tensioner vs ST spring
take off air box and measure throttle bodies, BT are larger
have a look at cams, BT have a 'waisted' base circle
BT has larger exhaust ports
If possible use borescope to check out piston tops, ST has defined '5th valve' cut out.

This should be enough to determine if BT or ST

[Mr Revhead]

the black top ecu will run a slivertop no problem if wired properly
the 7800 limit sounds like its not wired correctly.
the VVT issue sounds odd. if VVT is activated too low they idle rough. have not heard of a VVT issue that stops it revving though..... is the cam timing correct?? maybe in doing the "hybrid" they mixed up the cam belt bits and its a bit screwy?

so, first thing to do would be see if you can do as the above poster mentioned
also run it on the best fuel you can, 98 is a good idea on these.

[deltathing]

thanks for the reply!

If this motor is indeed a "hybrid" what are the tell signs its a ST block/bottom end without having to pull it apart..

Also i've read posts on here that a hybrid bt/st would be quite difficult to put together. however if this was the case would that explain the strange performance? incorrect fuel/timing map due to a different compression ratio or other incompatibilities?

thanks again..

[Mr Revhead]

its not hard at all

heres a good run down of the diffeences between the two
http://forums.toyspeed.org.nz/viewto...50ca3c56b4bed5

[deltathing]

Its been run on 98 octane only since i've had it, its definitely some kind of timing issue with the VVT connected the motor is smooth from idle to 2.5k then starts to sound like a lawn mower as it moves between 3-4k. with the solenoid disconnected it seems fairly retarded at lower revs, however up high it still runs fairly well.

I've verified alot of the wiring, injectors, igniter, TPS, VVT, idle up, CAS etc are all wired properly and it is not in the "engine check" mode, however if i disconnect say the TPS the motor will go into this mode.

[-GT-]

I reckon it's a silvertop running blacktop ecu+map etc, with possibly a faulty vvt action, you say it runs quite smoothly, but what do you mean 'retarded' between 2-4k? Just really sluggish, no power, then comes good?

vvt switches at 4400 or so, and it'll still run fine without vvt activating, might be worth checking for a dodgy earth off the solenoid?

[deltathing]

by retarded i mean its timing isn't correct at that rev range and it struggles to rev freely with the VVT connected.

thanks again for the replies ppl.

[deltathing]

another quick question...what issue could be causing the 7,800rpm rev limiter if the ecu is an ae111 blacktop unit?? as mentioned previously i've checked alot of the sensor wiring and verified it to be correct and the motor is not in "safe" mode.

[JP]

how is the map sensor connected?

Got a pic? That should tell you if it's an AE111 quad throttle setup.

To check if it's an AE111 bottom end, pull the splash guard off and look for the hydraulic cam belt tensioner ram that bolts in to the left of the crank pulley.

Is this motor in a green seca by any chance? If it is, then it's indeed an AE101 bottom end with AE111 head. Original motor threw a leg out of bed and the bottom end was replaced with an AE101 setup.

7800rpm cut most likely caused by an incorrectly wired speed sensor from the back of the dash cluster to the ECU (violet wire with white stripe), if the ECU's not receiving it's 4 pulse per revolution speed sensor signal then it will reduce the revlimit.

Any fault codes logged by the ECU?

Have also seen a faulty VVT pulley cause a blacktop to run like a complete bag of crap over 3000-4000rpm.

[mr2gze]

Is this motor in a green seca by any chance? If it is, then it's indeed an AE101 bottom end with AE111 head. Original motor threw a leg out of bed and the bottom end was replaced with an AE101 setup.

Yeh I suspected the same car.

Here http://www.twincam.info/index.php?sh...=17380&hl=seca
and here http://www.twincam.info/index.php?sh...=15920&hl=seca

[deltathing]

That is indeed the culprit. My brother bought it from arch. and it runs like shit with the VVT connected. From my experience when the ecu isnt getting a speed sensor signal it still throws up a check engine lamp, however this is not the case with this car, it doesn't have any diagnostic error codes. It just won't rev over 7800rpm. w t f.

[MRMOPARMAN]

has the check engine light even been connected to the new ecu? it should come on for a few seconds when the ignition is turned on.

also some engine problems dont throw codes. im not familiar with this type of problem but maybe having it disconnected wont throw a code?

[Talasas]

Anything I would have suggested has been said already but I would definitely start by following the speed sensor signal wire to make sure it's wired up.