Rb25 Conversion

[Raki_King]

Hey Guys and Girls

I am just about ready to scrap my whole project as no one has any idea how to fix my problem.

I have an R34 GT Sedan which was 2L Non turbo auto..Which I have replaced with a RB25DET Neo out of a Stagea and converted to manual. We have have used the ECU from the stagea and have re wired the loom and basically the car is drivable.

The car is drivable with a "Normal" driving style eg..normal gear changes and normal accelleration. The problem arises when we plant foot. at about 3500rpm with the turbo at 8psi the car loses all power and dies untill the revs drop abit then all power returns and its drivable again. With the same thing happening if you plant foot again.

We have plugged some equipment into the consult port and basically the story is that at the exact point that the power cuts the afm is maxed out and the injector cycle cuts...

We have used the afm from my RB20DE out of my r34 and it is pink sticker(Same as GTT) so thinking that it may be a faulty afm we tried one from an R34 GTT and an R33 25DET and same story(Maxed out)...We have checked for boost leaks and nothing. checked the voltages at the afms in both my car and a GTT at idle and 2000rpm and both readings are exactally the same so why is it maxing out when the turbo spools up?

Im really hoping someone can help me out as this problem is stopping me getting the conversion certified and having my car back which has been close to 5 months.

Please help me...I really want my car back running as it should be.

Cheers.

[paulr33]

if the AFM is maxing out what do you expect the ECU to do?

of course its going to panic and dump all the timing etc, its a standard protection mechanism

it would seem unrealistic that you would max out a stock ER34 GTT AFM

are you sure its reaching 5v and flat lines? does it ramp up linear or instant ramp to 5v?

maybe something else is wrong with the AFM control circuit?

with key to ON but engine not running AFM should be sub 0.5v and at idle it should be 1.1v

a bog stock ER34 GTT with a stock ER34 AFM Will not max out, so something is fundamentaly wrong

either your AFM is mangled, the wiring is mangled, your ECU is mangled or you are looking at incorrectly

[Raki_King]

The diagnostics are telling us that it is building voltage as it should when accellerating but the minute you plant foot it hits 5v and it cuts out. We have compared voltages and everything to the gtt that we had with us yesterday and everything is identical....

[Don Dada]

I'm taking it the Stagea was auto trans right???

Maybe has something to do with the auto ecu u are using as the engine and trans computer are built in that one unit with the Neos

I know in the R33 the auto ecu will run with the manual conversion done but not sure about the in the R34

Should try a manual ecu

[paulr33]

and are you sure you are using a GTT AFM and not an ER34 N/a AFM ?

what boost control are you using ? what is your boost set to?

do you have the factory map sensors connected (there are two)

[Duncan]

you're sure its the right afm right?

anyway....the stagea ecus have a really narrow band of tolerance to mods, and when you are off that they pull heaps of timing and richen up like crazy. first time I hit it I honestly thought I had blown a cooler pipe off it was so bad.

ubfortunately there is no easy way to swap an aftermarket ecu in there to check though, there were differences between r34 and stagea pin outs so you would need to find one pre-modified to the same ecu model that you have.

[MBS206]

If you use say 75% throttle, does it do the same, 90% throttle?

If no, there's a wiring issue, and it sounds like something is crossing up with the TPS sensor.

Edit: Simple test, with key switched to on, engine off, put the accelerator flat to the floor, does the AFM read 5V?

Edit: Just checked the wiring diagram, and there is the variable TPS read out, and there is an idle/WOT switch also.

I'd be guessing the WOT switch could be connected over to the AFM by accident if the above test yields a "yes, it reads 5V at WOT engine off"

[battery]

so you have checked for ecu errors??

knock sensor error will do something similar...

[Raki_King]

Thanks for the help guys I really appreciate it but we have found the issue...Im not exactally sure what the problem was but I am told that it had to do with the speed cut.

basically they sed that the ecu was thinking that the car was travelling a lot faster then it actually was eg.. 190kph so....long story short, a wire was chopped and the car is now fixed...

Thanks Again,

[GTScotT]

im assuming the wrong speedo sensor was used in the conversion. perhaps your mechanic swapped the speedo sensor from your auto over not considering the ecu was changing also.

OR

maybe the manual parts came from another car and ur stagea motor was originally auto?

make sure you fill us in with this info for future search value.