Jump to content
SAU Community

Rb25 Engine Troubles

sd9k

By sd9k,
in Engines & Forced Induction

 Share

Recommended Posts

sd9k Apprentice

sd9k

Posted
Posted (edited)

hi i drive this

skyline-1.jpg

so i got my car tuned last week and have been having nothing but problems

and the dyno is whacked looking

dyno2.jpg

current mods are: safc neo, custom t3 (stock compressor housing bored out with a bigger wheel, t3 exhuast housing), sard fpr, greddy fmic, 3inch straight pipe

can anyone tell me why there is a huge "dip" in the powerband?

Edited by sd9k
Link to comment
https://www.sau.com.au/forums/topic/236635-rb25-engine-troubles/
Share on other sites
sd9k Apprentice

sd9k

Posted
  • Author
Posted
need ecu

meh alot of money went out this past month so it will have to wait

which baffles me is that my car has run perfectly fine in the past with about the same amount of hp

any other ideas?

PM-R33 Grand Master

PM-R33

Posted
Posted (edited)

AFM maxing out by the looks of it and hitting airflow cut. How you managed even that power on the stock AFM is interesting....

Also, you aren't running the standard injectors and fuel pump are you?

Edited by PM-R33
sd9k Apprentice

sd9k

Posted
  • Author
Posted

ya stock injectors and fuel pump

prolly back the hp down to around 230-250 or so

i've ran that power before with nps

but i think it's just way too lean

takin git back to the dyno friday

so hopefully everything will be sorted by then

or it rather be

ha

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
Yep AFRs are horrible, knock sensor is probably going nutso

huh?

AFR's look fine to me, sitting on 12:8 - 13:1 quite consitently. Dosn't seem anything wrong there

Gets a slight leanout as the RPM goes up, but that looks to be totally controlled by the tune as its not sharp, its slight, even and linear.

270rwhp is 200rwkw, which is what is probably the limit of the stock turbo.

And as your the aftermarket turbo, its likely reaching the AFM limit as stated. Every car is different with the AFM. Some are fine, some dont like it. Just how each seem to be really.

I'd be looking to

1. Change the fuel pump (do it regardless)

2. Upgrading the AFM

In the short term to get it driving nice, smooth and so on. Retune required there.

3. As i'd roughly say the turbo should make 340rwhp or so (hard to tell but thats what id be expecting), injectors might not be a bad investment at some point depending on how 1 & 2 go.

Cheers

Guilt-Toy Grand Master

Guilt-Toy

Posted
Posted

remember ppl US power is about 20 to 40 % more then Aussie power. We work on true HP figures not the fairy HP that gets quoted on the other side of the globe.

that AFR is too lean. i would not let any car off the dyno with a AFR like that unless the owner knows it needs to be fixed. IMHO

Lithium Grand Master

Lithium

Posted
Posted
remember ppl US power is about 20 to 40 % more then Aussie power. We work on true HP figures not the fairy HP that gets quoted on the other side of the globe.

Couldn't disagree with this more - so bored of hearing Aussies say that. If any dynos could be said to read "untrue", its Aussie dynos. Low reading doesn't mean more true.

that AFR is too lean. i would not let any car off the dyno with a AFR like that unless the owner knows it needs to be fixed. IMHO

Very much agreeing with that - not sure why sd9k is asking for advice and then basically ignoring it. Sd9k - you are LUCKY that you haven't blown your engine up running that kind of setup, the ECU is obviously trying to save it and with no help from the S-AFC.

A Neo by no stretch of the imagination gives you a decent proper tune, and you shouldn't be running a bigger turbo like that with stock AFM/injectors/pump. I am pretty damn sure anything else you try at this stage will not work, a proper ECU and associated fuelling changes are the first things you should be considering. Really - you should have done that before changing the turbo if limited funds are an issue.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
remember ppl US power is about 20 to 40 % more then Aussie power. We work on true HP figures not the fairy HP that gets quoted on the other side of the globe.

that AFR is too lean. i would not let any car off the dyno with a AFR like that unless the owner knows it needs to be fixed. IMHO

Haven't people been tuning around that a lot lately?

More higher end tuners etc.

I cant remember exactly ;)

Guilt-Toy Grand Master

Guilt-Toy

Posted
Posted

Okay so your saying aussie dyno's read low compared to the ones used in the US ? that would explain a few things.

and yes that car needs some serious attention. if you drive it hard like that it will blow in a matter of time. Take the advice given by these guys, computer, injectors and fuel pump is a MUST for this car or you will destroy the engine, have to buy a replacement and then still be where you started from.

Lithium Grand Master

Lithium

Posted
Posted
Okay so your saying aussie dyno's read low compared to the ones used in the US ? that would explain a few things.

Dyno Dynamics are pretty much the lowest reading dynos used anywhere. Again, that doesn't mean they are more or less accurate - they just put smaller numbers out.

  • 2 weeks later...
sd9k Apprentice

sd9k

Posted
  • Author
Posted
Couldn't disagree with this more - so bored of hearing Aussies say that. If any dynos could be said to read "untrue", its Aussie dynos. Low reading doesn't mean more true.

Very much agreeing with that - not sure why sd9k is asking for advice and then basically ignoring it. Sd9k - you are LUCKY that you haven't blown your engine up running that kind of setup, the ECU is obviously trying to save it and with no help from the S-AFC.

A Neo by no stretch of the imagination gives you a decent proper tune, and you shouldn't be running a bigger turbo like that with stock AFM/injectors/pump. I am pretty damn sure anything else you try at this stage will not work, a proper ECU and associated fuelling changes are the first things you should be considering. Really - you should have done that before changing the turbo if limited funds are an issue.

i'm not ignoring advice at all man

i just don't come on here that much

but as far as the car is concerned right now

the guy who was supposed to retune the car never returned my calls

so i said f**k it and returned the boost back down to stock

and all of the corrections on the safc back down to 0 and the car runs fine like it did

and as far as the turbo on the car, it came like that when i bought it so i didn't really have a choice in the matter

but thankfully i'm coming into some moeny here next week like 1k bucks

so i'm pretty hyped

going to buy 550cc injectors, GTR fuel pump, and a z32 maf

is an ecu reflash a good idea or should i just wait to get a PFC

i've heard nothing but good things about PFC so i'm assuming that's the standard esp for RB's

but i'm open to other options as well

thank you all for the support and advice :cool:

Cheers.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Murray_Calavera
      Stock rb25det neo questions

      By Murray_Calavera · Posted

      Pretty much what you'd expect at that power level. Hypergear turbo, long list of supporting mods, full Haltech catalogue, etc.  I'd say this goes for most drivers, suspension is still a dark art for most people. And it's really hard to convince someone how much better their setup could be...  
    • GTSBoy
      Stock rb25det neo questions

      By GTSBoy · Posted

      They are what I will be installing. 640s for me.
    • GTSBoy
      Stock rb25det neo questions

      By GTSBoy · Posted

      Hmm... From my experience you get about 0.25° camber change per mm of RUCA length change. So, to correct from -2.5 up to less than -1° (or, more than -1° if you look at the world as a mathematician does) then you'd be making 6-8mm of length change on the RUCA. From a stock length of 308mm, that's 2-2.5% difference in RUCA length. My RUCAs are currently very close to stock length - certainly only 2-3mm different from stock. I had to adjust my tension arms by 6mm to minimise the bump steer. That's 6mm out of 210, which is 2.8%. That's a 2.8% change on those, compared to a <1% change on the RUCAs. So the stock geometry already has worse bump steer than is possible - you can improve it even if you don't change the RUCA length. If you lengthen the RUCAs at all, then you will definitely be adding bump steer. Again, with my car, I recently had an unpleasant amount of bump steer, stemming from a number of things that happened one after another without me having an opportunity to correct for them. I only had to change the tension arm lengths by 1mm to minimise the resulting bump steer. (Granted, I also had to dial out a lot of extra toe-in in the rear, and excessive rear toe-in will make bump steer behaviour worse). Relatively tiny little adjustments having been made - the car is now completely different. Was horrifying how much it wanted to steer from the rear on any significant single wheel bump/dip. And it was even bad on expansion joints on long sweepers on freeway entry/exits, which are notionally hitting both rear wheels at the same time. My point is, the crappy Nissan multilink is quite sensitive to these things (unlike the very nice Toyota suspension!). And I think 99.75% of Skyline owners are blissfully ignorant of what they are driving around on. Sadly, it is a non-trivial exercise to set up to measure and correct bump steer. I am happy to show my rig, which involves nasty chunks of wood bolted to the hub, mirrors, lasers, graph paper targets and other horrors. Just in case anyone wants to see how it is done. I'll just have to set it up to take the photos.
    • Wazmond
      Stock rb25det neo questions

      By Wazmond · Posted

      What do you have in that bad boy ? Ill go with the 725cc since I'll be going with Nistune ( would definitely like more engine protection but Haltech is too far out of reach at the moment... plus, Ill probably have a pretty safe tune as its a daily, not gonna be chasing peak power 24/7 ahahah ). Are Xspurt a safe choice?  Pete's great. He didnt mention anything about traction arm length so I reckon it may be good. When I get some new wheels/tire later down the road I'll ask him about it and get his opinion on em. I heard from Gary that you've got the bilsteins too, are you running the sway bars too? and what other suspension goodies do you have installed or would recommend?
    • Dose Pipe Sutututu
      NC MX5

      By Dose Pipe Sutututu · Posted

      In true Gregging style...  
×
×
  • Create New...