Why is it so

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Q

Quadcob

Member
My car has a 1uzfe(crown) with a R154 gearbox, 4.11 diff ratio and weighs about 1100kgs and gets up and goes well. It just has what I would describe as bit of a nuisence problem(?) in first gear. When I stretch its legs in first gear, at 6000rpm it breaks down, into to second and it revs 6500rpm plus with no trouble. First I thought it was a rev limiter, but as it dosn't do it in second gear that can't be the problem. I haven't tried to take it to 6000 + in third gear yet, but I don't think it would be a problem.
I don't know if it is a fuel delivery problem, but I have a fuel pump from a factory car that has has a LS2 Chev motor so I wouldn't think so. It has all new iridium spark plugs, spark plug leads, distributer caps and rotors.

Any ideas as what the problem could be.

Warren
 
i would imagine you would use less fuel at 6k in 1st then 6k in 2nd. due to the increased load of the higher gear, so a fuel problem would become more apprent in higher gears not lower gears.

this is a streach but is it possable in 1st the ecu thinks the car is being free reved and cutting it off early in an effort to save the motor. where is in 2nd theres enough load for the ecu to realize its accually pulling somthing along?
 
I'm thinking along the lines of Jake, but its still quite odd.

Try hooking up the speed input, even if its way off (make sure the input is less than the speed you are doing, not more), it may still work.

If the R154 has a sensor at the rear of the box as well as the speedo output, then this may be what you need to connect.
 
As the crown uses a separate ecu for the auto I thought that the motor ECU did not need any signals from the gearbox to function in a stand alone situation.
The second speed sensor fon the r154 is for the abs from the donor car. The motor ecu dosn't have any input from the gearbox.
It has been suggested that it could be what Jake has suggested. I will try building the revs up slower in first gear to see if I can get above 6000revs. The slower build up of revs should overcome the free reving effect.
 
Well Jake and Peewee just as you thought. It appears that the speed the motor revs up when I accelerate hard in first gear must in the parameters of the what the ECU thinks is free reving an unloaded motor. When I drove of and built the revs slowly the tacho climbed up to 6500 rpm without a hesitation. It is not a problem that I can't go over 6000rpm in 1st gear when accelerating quickly, but I will try to see if I can get a speed signal to the ecu to overcome this hiccup.

Thanks
Warren
 
maybe your tacho is slow

when u rev it fast in 1st your tacho might be afew 100 rpm out
ive seen it afew times especially on the big wanky autometer ones

when yr in 2nd or 3rd the engine wont rev as fast so your tacho can keep up

get an electronic digital tacho and see what it goes to

i dont think its a problem

ive wired up over 50 1uzs and most are manual and dont have probs when spd signals are missing

if u had probs it would be limiting the rpms to below 4000

and i dont see y when slowly reving it to 6500 is ok

but when u hit it hard it revs to 6000

anyway i think its a tacho problem
 
Sideshow,
The tacho is a VDO. Checked the speedo against the tacho to 6000rpm going slowly and quickly. The speedo reads about the same for both tests. As Muzza suggested the power drops going to these revs so there no benefit achieved going to 6500rpm. Just curious why it does it.

Warren
 
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