Jump to content
SAU Community

Recommended Posts

Hi all,

Im stumped, and so is my mechanic / tuner... I need some good advice please. :)

Here's the story:

I have an R32 Gtst which I put an R33 S1 RB25DET into a while ago and I have been building it up for about 12 months to try and get some serious power, I have put all of the goodies on it that I know I will need to make the power but after spending over 4 hours tuning on the dyno we have only managed to get 233rwkw and 550nm from it, its running a consistent 11.7 - 1 AFR and pretty solid boost = 17 - 18psi at the manifold.

Im not happy because I know that there is so much more power waiting to be unlocked, it should make around 260 - 270rwkw but it just wont...

Im not a mechanic and I dont know how to tune a car either but I am fairly good with a spanner and I know enough to get me by, but my local tuner said to me that he couldnt get anymore power from my car even running 21psi!

The modifications include:

*Power FC

*Splitfire DI ignition coils (NGK iridium plugs, gapped to 0.8mm)

*SARD 550cc injectors

*Bosch 040 fuel pump

*3 inch mandrel dump pipe - full 3 inch mandrel Tannabe exhaust system with 3.5 inch high flow "metal cat"

*Large front mount intercooler (300x600x75mm), Turbosmart supersonic BOV

*GCG Garret GT30/71R ball bearing turbo

*Turbotech manual boost controller

I have checked to see if the cat is blocked and it isnt and the O2 sensor seems to be working fine, however I dont know if one or both mufflers are partially blocked in the exhaust.

What could possibly be keeping my engine from making peak power?

Can anyone help?

Edited by Bullet32
Link to comment
https://www.sau.com.au/forums/topic/183787-underpowered-rb25det/
Share on other sites

  • Replies 40
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

heya bullet32 :)

if you are making no more power at 21psi than 18 psi you are suffering from Valve float.

not really that much of a drama, you will need to pull off the cam covers, cam gears, cams, lifters, retainers, collets and then replace the springs. A good set will cost you $300 form performance springs.

the drama will be the labor bill for the work. most workshops would charge 8 hours to do it and its not really something you can do yourself.

I had to make a special tool to replace the springs in my head and it is still a pain in the ass. and this is with the head is off my car.

It definitely does sound as though there *could* be a restriction somewhere in the exhaust...

Id simply try swapping over to a complete different exhaust temporarily if possible, just for one or two dyno runs, to check if it alleviates the problem.

Also perhaps check simple things like if your air filter is blocked?

If it is valve float and it is borderline then cam gears can also help by reducing overlap but it sounds like the more boost = no more power at all. was this done at Autotech?

if so get Pete to print out one of your runs at 17psi and one at 21psi and post em up so we can have a look at what is happening.

Cheers!

Yeah it was at Autotech.

Ed did the tuning not Pete, and he said that he thought that it was a blocked cat but like I said, I checked it and its fine so I think you might be right that it could be the valves...

Could a blocked exhaust restrict the power that much?

Oh and there seems to be heaps of inlet reversion now even though Ive backed the BOV right off.

Edited by Bullet32

Ive e-mailed GCG and asked for exact specs but as far as I know its a 450hp rated turbo and its peak efficiency is between 18 - 24 psi, so that should be plenty for the power I want (260 - 270 rwkw).

it's not not unusual for an rb25 to valve float at around that boost level. it's not common but not unusual.

also not much else will cause a "no power increase" with more boost added.

I am speculating without seeing the car but my money would be on valve float :P

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



  • Similar Content

  • Latest Posts

    • I would just put EBC back on the "I would not use their stuff" pile and move on.
    • Can I suggest you try EBC directly again and link them to as many competitor catalogues as you can to show their listing is incorrect, eg https://dba.com.au/product/front-4000-series-hd-brake-rotor-dba42304/ If you have access to an R33 GTST VIN and your VIN, you could also use a Nissan Parts lookup like Amayama to show them the part number is different between 33 GTST and 34 GTT which may get their attention
    • So i got reply from EBC and they just this site where you can clearly see those 296mm fronts on R34 GTT. I send them photos and "quotes" that 296mm are not for 34 GTT and they are too small. But it will be very hard to return them cuz nobody here knows 100% and they just copy those EBC catalogue :-D https://ebcbrakesdirect.com/automotive/nissan/skyline-r34
    • Hi, is the HKS  Tower Bar still available ? negotiable ? 🤔
    • From there, it is really just test and assemble. Plug the adapter cables from the unit into the back of the screen, then the other side to the car harness. Don't forget all the other plugs too! Run the cables behind the unit and screw it back into place (4 screws) and you should now have 3 cables to run from the top screen to the android unit. I ran them along the DS of the other AV units in the gap between their backets and the console, and used some corrugated tubing on the sharp edges of the bracket so the wires were safe. Plug the centre console and lower screen in temporarily and turn the car to ACC, the AV should fire up as normal. Hold the back button for 3 sec and Android should appear on the top screen. You need to set the input to Aux for audio (more on that later). I put the unit under the AC duct in the centre console, with the wifi antenna on top of the AC duct near the shifter, the bluetooth antenna on the AC duct under the centre console The GPS unit on top of the DS to AC duct; they all seem to work OK there are are out of the way. Neat cable routing is a pain. For the drive recorder I mounted it near the rear view mirror and run the cable in the headlining, across the a pillar and then down the inside of the a pillar seal to the DS lower dash. From there it goes across and to one USB input for the unit. The second USB input is attached to the ECUtec OBD dongle and the 3rd goes to the USB bulkhead connected I added in the centre console. This is how the centre console looks "tidied" up Note I didn't install the provided speaker, didn't use the 2.5mm IPod in line or the piggyback loom for the Ipod or change any DIP switches; they seem to only be required if you need to use the Ipod input rather than the AUX input. That's it, install done, I'll follow up with a separate post on how the unit works, but in summary it retains all factory functions and inputs (so I still use my phone to the car for calls), reverse still works like factory etc.
×
×
  • Create New...