First Time Turbo User Questions (rb25)

[Pantera999]

Hey guys,

I am a member of the r31skyline club, but haven't gotten as much response as i would have hoped to, all the turbo nerds seem not to reply .

Anywho,

I have a stock rb25det, series 1, in my r31 skyline. Stock sidemount, 33 ecu, rah rah rah.

I will post up the topic i did on the r31 club, to save re writing, and will also post up some answers from the people that replied, just to see if anyone agrees/disagrees/can extend on further.

they are basically all boosting/turbo problems

anywho

1st. When boost comes on... it feels, weird, like it will jutter, its a weird feeling, hard to explain, it feels like when your almost about to stall a manual car. I ahevnt mucked around with the dual stage boost control enough, butit seems to do it more on 9psi than on 6.

I was watching the gauge when i had it on 9.. it would start off, looked like itd stop to around 6, then itd slam to about 12, in a quick sudden move, and the car will well jutter again as id change gear everytime it happened, is that boost spike??? IT feels really unsmooth... i think the turbo may be a bit gone, as there is no turbo timer and the engine has been in for 3 years without one, and when i went for a drive with the previous owner, he had boosted it fairly often and just switched it off.

2nd. I think its an ecu/tuning problem, it is running off standered 33 ecu, is there supposed to be a cut out on the 33 ecu? I had read that the 25 makes peak power around 6400, and it feels like its cutting off at around 5000 (according to tacho), itll keep reving past there but no power will be made, its like hitting a block wall. Is that normal or will mr aftermarket ecu fix it??

But yeah, the boost problem is the weirdest, im thinking maybe the sidemount is a bit to small, or maybe the gearbox ratios? as its running the standered 30 gearbox...

I want to take it to a turbo specialist, but i dont wnat to get charged a million dollars for them to say oh it just needs a tune.

Thanks heaps

Todd.

SOME OF THE ANSWERS/size]

Lysdexia

for your first q, yeh thats boost spike when it hits 12 then comes back down. the way it hesitates as it comes onto boost could be a few things, but spark would be the first thing i'd look at. turbo cars for the most parrt need to have the plugs gapped down to .7 or .8, or even smaller. if this downt help then it may be a fuel issue, which could be caused by any number of things, afm would possibly be the first suspect though.

second question. the only cut you should be experiencing is a rev cut, and thats at liek 7500rpm on the 33 ecu.

to me it sounds like you may have a fairly common problem there, as if i recall you're still running the stock airbox. if so, and you have a soft rubber turbo intake pipe, theres a high chance your intake pipe is sucking itself closed. you can diagnose this easy, tae your airbox lid off and the filter out, go for a run. if it still does it then, then there's your culprit.

Angry

common for some r33 ecus to have a "big hole" .. in the rev range .. at around 5k ... then pick up marginlly after that .....can be tuend out thru SAFC or try your luck getting another stock ecu..

The stock fuel pump for the 31 was also suggested to be of cause as well, I am looking at getting a 040, that will last a while for future mods as well.

And yes i do have the stock rubber intake Lysdexia was on about.

What do you guys with experiance with 25s/33's think???

Cheers, Todd.

[RB30-POWER]

If you have it running more then stock boost then its probably hitting the ignition cut and rich fuel zones, otherwise known on here as "rich and retard mode".

Solution is to run standard boost or get a PowerFC or Apexi SAFC system to overide the AFM signal.

You can't just boost these cars up like people did with late 80's jap imports as the ecu has protection built in.

[mad082]

well there could be a few things. i doubt that you are hitting rich and reatrd mode, especially with a side mount at 9psi. we need a few more details.

for the first problem, what plugs are you running, and what are they gapped at? i recommend copper ngk's (bcpr6es i think the code is). iridiums are a waste of money. gap them to 0.8mm instead of the stock setting of 1.1mm. secondly the problem could be the coilpacks shorting out. the easy way to fix that is to tape them up with some good quality electrical tape.

for the second problem of it not reving up high, what mods do you have? what air filter and exhaust setup do you have? if you are running stock or semi stock exhaust and stock air filter then that will be part of the problem. they are rather restricting. when i got my r33 it was stock as a rock (except for 80mm front pipe) it would get high in the revs and just choke. and getting it to redline was hard as it just couldn't flow enough air.

and if you are running the sr31 fuel pump i'd probably suggest going ahead with the upgrade.

another option is to stick it on a dyno and see what the afr's are like, to make sure it isn't leaning out too much.

[Pantera999]

Hey, thanks bud, yeah its a 2.5 inch exhaust, filter gear bar a pod. I am getting a front mount in a few weeks (not installing for a bit but), and a power fc once tax back comes. I'll check what plugs are on tomorrow.

Cheers, Todd.

[RANDY]

The flat spot that those other guys were talking about is commonly due to a faulty coil.

As far as the boost jumping up quickly and shuddering to get to 6... maybe try rigging the piping back up to a stock R33 boost actuator? Or buy the $35 boost controller that everyone here loves, it should eliminate the EBC being at fault.

I'm guessing that you're running the stock R33 wastegate and BOV too? Each time you change gear, the BOV should be venting the air back into the system. Well, every time you change gear, you will be building boost again, which is where you are having the shudders. I really think the EBC should be bypassed as a troubleshooting thing.

Failing that, check knock, timing, and fuelling?