R33 Rb25det - Cutting Out On Boost

[prawln]

Hey guys,

I recently put a RB25det engine into my partners R33 Rb25de car, Got it going etc etc. Im running the boost off the standard 5psi actuator. Its running ok but to be honest it doesnt feel like its really pulling. So ive just got a 10psi actuator and now when its boosting it cuts out at around 8psi when giving the car some stick.

In first gear it seems to be fine without cutting.

When i take it up hill it in 3rd gear it starts cutting at like 5 psi. I have taken videos that i have attached below.

Alittle about the car, Everything on it is standard but a pod filter and front mount intercooler. It has a RB25det fuel pump in it also.

I have put a fuel pressure gauge in also and the fuel pressure at idle is at around 40psi (alittle below) and when giving the car stick it gets up to around 60psi. Which to me seems fine with no issues there (im not very good with skylines, have only really work on my rx7)

Anyways i hope ive given good info about the issues.

Going up hill in 3rd gear, you can hear it cut/die then come back then cut/die again then come back.

Going down the street with foot flat. Car dies then when i pull foot off accel alittle it comes back.

Also i have replaced all spark plugs but still seems to be doing it!

Ive been doing some searching and have seen some people talk about AFM cut? what is that and how can it be fixed?

Its running a stock ecu also and the AFM is the one that was used for the RB25DE engine but is the pink kind so thought it would be ok.. Do i need to buy a different AFM?

Any help would be good!!

Edited September 8, 2010 by prawln

[tridentt150v]

r+r = rich and retard, you have maxed out the std ecu, you will need a bender eg SAFC or ecu eg Vipec etc

[Randon_I_Am]

thats very low boost to be r+r though. unless of course it's not a stock turbo?

could be coil packs maybe, doing the standard cut out at 4-5k revs.

[prawln]

Turbo is stock standard series 2 turbo. It does seem odd that its cutting out at like 5 psi but then it didnt seem to have issues on the 5psi actuator but i will have to replace it back to the 5psi and test it out again!

I think it was roughly between 4 - 5k revs when it was cutting but seemed to be fine in first gear.

Whats the best way to check if the coil packs are the issue?

[tridentt150v]

front mount intercooler, pod and 10psi actuator but what is your real boost, did you use an AM gauge? because you could be running with more boost than you think.

[prawln]

thats very true! yeah im using one of the autometer stepper motors types. wondering if the gauge is under reading!

I might try put the 5psi actuator back on and get a boost tap/controller and try turn the boost up alittle.

I always thought that the ecu would be able to handle 10 psi as the rb20dets have the 10 psi actuator. Even if its a 10 psi actuator can it still jump over 10psi? i read somewhere that nissan say it may do more then 10psi is running on spring pressure?

[Randon_I_Am]

It may get up over 10psi. I've never experienced R&R so i can't really comment on that.

one way to check if it's the coil packs is to put (if you're not running them already) 0.8mm gapped spark plugs in. In a lot of cases this temporarily fixes the problem.

[prawln]

cheers guys! ill give it ago!! im thinking it could be coils as if going up hill and and i slowly make it build boost (foot not fully on accel) when it got to about 5psi and 4 - 5k rpm it started cutting out, but not just jerking but fully dieing (not stalling but just doesnt accel but the engines still running) but yet if i plant my foot then it gets to about 8psi and 4 - 5k rpm and does the same with dieing

So if i change the gapping to .8mm gapping and it fixs the issue its the coils that need replacing?

Edited September 8, 2010 by prawln

[Rolls]

Probably a combination of RR making it run rich as hell and crappy old coils/plugs giving a weak spark making it missfire. Replacing the coils might fix it if they are bad but you will still be running too rich, a remap or safc, nistune etc will more than likely fix your issue and if it isn't the issue it is still a great upgrade, more power, better fuel economy etc providing you get someone who knows what they are doing to tune it.

A boost leak will cause issues like this as well though, check all your piping and hose clamps.

If you have an exhaust and pod etc you can easily run over 10psi, I've seen up to 12psi with no boost controller and a free flowing exhaust before.

Edited September 8, 2010 by Rolls

[prawln]

cheers mate! one issue i have with exhaust wise is its the standard 25DE non turbo exhaust with the old cat converter in it. I just got a 25det turbo front pipe and connected it straight up to the old small exhaust, would this cause issues aswell? not being flowing enough

[Rolls]

if it is really restrictive it will sap lots of power but I don't think it would cause missing etc.

[prawln]

sweet will keep you guys posted! i might remove the cat tomorrow and just weld a pipe in place and see what happens, time for bed now lol 1 am and the missus is giving me evil looks haha, will let you know what happens tomorrow! Cheers again guys!

[tridentt150v]

So if i change the gapping to .8mm gapping and it fixs the issue its the coils that need replacing?

No, if you are running with more boost say >10psi then you have to reduce your gap to 0.8mm anyway. the extra boost is blowing out the spark across the arc. By lowering the gap it gives the charge a better chance of sparking.

0.8mm may fix it and you'll not need anything else - I run with 0.8mm gap, heaps of ppl here do it.

[prawln]

Cheers guys, you guys are really helpful and awsome, im not so good with these engines as ive only work properly on my rotary and thats a whole another ball game haha.

Anyways going to remove the Cat and change the gap and will report back!

[prawln]

ok so ive removed the Cat converter to try free it up but still no change, ive changed the spark plug gaps to 0.8mm. Still seems to be cutting out. I T join connected the boost gauge to the line that i have that goes from the intercooler piping (have a nipple tapped into the piping straight after the turbo elbow) and goes to the actuator. Interesting enough this time when the car dies under boost, the boost acully drops where as before when it was connected to the manifold it was saying the psi wasnt dropping. I can hold it at 5psi perfect and it doesnt die but if go above it feels like the car starts to bog down then about 7psi it dies.

Would this be R&R? im about to go change back to the 5psi actuator and see if it dies at all!

[prawln]

Hey guys so have put the 5psi actuator back on and car didnt die at all woop woop! BUT when giving it balls it doesnt seem to get over 5k - 5.5k rpm, its completly screaming by then. Also in the transition from 0 - 5psi it feels like the cars holding back then gets a burst of power then holds back then gets a burst of power etc.

I put the new spark plugs in yesterday and took for a little drive then pulled them back out again today and they were sootty black and had white on the tip. What does this mean? rich?

Help!!!! im so confused!

[Rolls]

Means it is running very rich, is it possible you have a boost leak as 5psi is way too low for RR to be kicking in, unless of course you have a faulty AFM or something making it think it is reading more air than it actually is.

Can you get a diagnostic plug and check for error codes?

[prawln]

Ive just cleaned the afm just waiting to dry it out, did a error code check, it gave off the code 55 which is no malfunction. im stumped! I tried reving it out of gear just sitting there and it only gets to about 5.5k rpm and wont go higer. is that coils im guessing?

[Rolls]

For it to miss even in neutral means they must be pretty damn stuffed, I would pull them out and check for arcing etc, there is loads of threads on diagnosing and repairing them, definitely worth a shot before forking out $500 for new ones.

Personally I still think that the car is out of tune for whatever reason and the rich afr is the main cause of your problem, a rich mixture will blow out the spark below 9:1 most the time no matter how good the ignition setup is.

Edited September 9, 2010 by Rolls

[prawln]

i taped up the coils and flushed out the afm with degreser ( i saw another thread that said to try that.) the car now when it hits about 3-4 psi it dies!! it has to be the AFM! as i dont think putting insalution tape around coils would do that!

Another thing i checked was the flints on the coils... theres like... no flint there! Would this be the issue?

The timing ive done i put it at 15 degrees advanced which should be ok.