Jump to content
SAU Community

R33 GTS-T revs go up and down with contant throttle

fried_bride

By fried_bride,
in General Maintenance

 Share

Recommended Posts

fried_bride Rookie

fried_bride

Posted
Posted

Hey guys,

I've recently installed a greddy style front facing plenum, FMIC, 80mm throttle body and oil cooler. I started the car up and it idles normally... good start.

Unfortunately, when I gave it some throttle, the revs build then drop and build then drop. Not good. I'm getting fault code 55 "ALL OK". Could anyone shed some light on what I should look at to get this sorted?

fried_bride Rookie

fried_bride

Posted
  • Author
Posted
On 03/11/2021 at 4:11 PM, GTSBoy said:

What does your ECU tell you that it is doing?

Please tell me that you're not trying to run this on a stock ECU.

Yeah I am running this on a stock ECU. The way I was looking at it is that the stock ECU would be able to cope with the difference in airflow being that everything else is stock.

Do you reckon this is the culprit?

GTSBoy Grand Master

GTSBoy

Posted
Posted

The reason I wanted to know you weren't trying it on a stock ECU is that changing to a really big TB is something that requires that you have a good handle on the mechanical and electrical condition of all the other things that matter, like the idle control motor. If you're doing it on a stock ECU, like everyone else who has ever done that before and had troubles (which is a massive percentage of all such examples) then you're flying blind, because you don't even know if your idle control system was workin before and you sure as hell don't know now and unless you have a decent Consult device or Nistune in the ECU (which you would have already used to find out what was going on if you did) you have no way of looking inside to see what it is doing.

Whereas, if you had an aftermarket ECU, even if it was Nistune in the stocker, you would know whether everything was working or not because you would have put the effort into making it work when the ECU was set up. And you'd be able to look inside and see what was happenign with the idle control.

The fact that pulling the TPS steadied the idle means that the ECU is now no longer using timing to try to control the the idle speed, which suggests that the idle control valve is not properly functional. You've quite possibly also got a large vacuum leak somewhere, or maybe the large TB is not closed enough to give the IACV enough scope to slow the idle.

  • Like 1
fried_bride Rookie

fried_bride

Posted
  • Author
Posted
On 03/11/2021 at 10:07 PM, GTSBoy said:

The reason I wanted to know you weren't trying it on a stock ECU is that changing to a really big TB is something that requires that you have a good handle on the mechanical and electrical condition of all the other things that matter, like the idle control motor. If you're doing it on a stock ECU, like everyone else who has ever done that before and had troubles (which is a massive percentage of all such examples) then you're flying blind, because you don't even know if your idle control system was workin before and you sure as hell don't know now and unless you have a decent Consult device or Nistune in the ECU (which you would have already used to find out what was going on if you did) you have no way of looking inside to see what it is doing.

Whereas, if you had an aftermarket ECU, even if it was Nistune in the stocker, you would know whether everything was working or not because you would have put the effort into making it work when the ECU was set up. And you'd be able to look inside and see what was happenign with the idle control.

The fact that pulling the TPS steadied the idle means that the ECU is now no longer using timing to try to control the the idle speed, which suggests that the idle control valve is not properly functional. You've quite possibly also got a large vacuum leak somewhere, or maybe the large TB is not closed enough to give the IACV enough scope to slow the idle.

Copy that mate! You are 100% correct. I ordered a Consult connector yesterday because I realised that I can't get very far if I don't have any way to query what the engine is doing.

Did you watch the video I posted? The idle was fine. I was getting issues when the throttle was open. Do you think that could have been due to the ECU doing a calc on fuel based on the volume of air expected through the stock throttle body using the TPS; and now that I have a bigger TB the calc would be off and result in running lean? I don't know if that is how it works but it was just the idea I had before disconnecting the TPS.

GTSBoy Grand Master

GTSBoy

Posted
Posted
On 11/4/2021 at 6:07 AM, fried_bride said:

Did you watch the video I posted?

No. It won't load.

On 11/4/2021 at 6:07 AM, fried_bride said:

Do you think that could have been due to the ECU doing a calc on fuel based on the volume of air expected through the stock throttle body using the TPS; and now that I have a bigger TB the calc would be off and result in running lean?

No, the ECU doesn't give a stuff about the TB. The air flow meter is at the other end of the inlet tract, and that's where the air flow is measured.

If you're having trouble with the throttle open, it's starting to sound like the TPS isn't right.

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted

Many issues there, some I can see:

  • Stock ECU
  • AFM & pod filter
  • Reversion from intake pipe
  • Stock BOV deleted & using a AFM

Easiest fix, throw the stock ECU and AFM into the bin, install a proper speed density ECU.

fried_bride Rookie

fried_bride

Posted
  • Author
Posted
On 04/11/2021 at 9:01 AM, GTSBoy said:

No. It won't load.

No, the ECU doesn't give a stuff about the TB. The air flow meter is at the other end of the inlet tract, and that's where the air flow is measured.

If you're having trouble with the throttle open, it's starting to sound like the TPS isn't right.

Fair enough haha she was a beefy sized vid.

 

Thanks for the help mate!

fried_bride Rookie

fried_bride

Posted
  • Author
Posted
On 04/11/2021 at 9:20 AM, Dose Pipe Sutututu said:

Many issues there, some I can see:

  • Stock ECU
  • AFM & pod filter
  • Reversion from intake pipe
  • Stock BOV deleted & using a AFM

Easiest fix, throw the stock ECU and AFM into the bin, install a proper speed density ECU.

Copy! Any suggestions on an ECU? Been looking at a Power FC or one of those Haltec Plug and Play bad boys, but this is my first time doing all this stuff so I am very unsure.

Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted

It's 2021 lol... please do not install a PowerFC, also you'll still need the AFM with the PowerFC and the way you've set everything up, a PowerFC will still give you you idle and stalling issues.

Just get a Haltech Platinum Pro Plug-in used if you can, great value and provides all the features you would need. If you have money and decide that one day you'll go tits out then get a better ECU that supports DBW, strain gauge input, etc.

  • Like 1
fried_bride Rookie

fried_bride

Posted
  • Author
Posted
On 04/11/2021 at 9:59 AM, Dose Pipe Sutututu said:

It's 2021 lol... please do not install a PowerFC, also you'll still need the AFM with the PowerFC and the way you've set everything up, a PowerFC will still give you you idle and stalling issues.

Just get a Haltech Platinum Pro Plug-in used if you can, great value and provides all the features you would need. If you have money and decide that one day you'll go tits out then get a better ECU that supports DBW, strain gauge input, etc.

You're a legend mate. Thank you very much for the advice.

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

    • Kapr
      RB20DE NEO smallbox clutch.

      By Kapr · Posted

      For once a good news  It needed to be adjusted by that one nut and it is ok  At least something was easy But thank you very much for help. But a small issue is now(gearbox) that when the car is stationary you can hear "clinking" from gearbox so some of the bearing is 100% not that happy... It goes away once you push clutch so it is 100% gearbox. Just if you know...what that bearing could be? It sounding like "spun bearing" but it is louder.
    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      Yeah, that's fine**. But the numbers you came up with are just wrong. Try it for yourself. Put in any voltage from the possible range and see what result you get. You get nonsense. ** When I say "fine", I mean, it's still shit. The very simple linear formula (slope & intercept) is shit for a sensor with a non-linear response. This is the curve, from your data above. Look at the CURVE! It's only really linear between about 30 and 90 °C. And if you used only that range to define a curve, it would be great. But you would go more and more wrong as you went to higher temps. And that is why the slope & intercept found when you use 50 and 150 as the end points is so bad halfway between those points. The real curve is a long way below the linear curve which just zips straight between the end points, like this one. You could probably use the same slope and a lower intercept, to move that straight line down, and spread the error out. But you would 5-10°C off in a lot of places. You'd need to say what temperature range you really wanted to be most right - say, 100 to 130, and plop the line closest to teh real curve in that region, which would make it quite wrong down at the lower temperatures. Let me just say that HPTuners are not being realistic in only allowing for a simple linear curve. 
    • Kinkstaah
      Mistakes were made, my R34 Story

      By Kinkstaah · Posted

      I feel I should re-iterate. The above picture is the only option available in the software and the blurb from HP Tuners I quoted earlier is the only way to add data to it and that's the description they offer as to how to figure it out. The only fields available is the blank box after (Input/ ) and the box right before = Output. Those are the only numbers that can be entered.
    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      No, your formula is arse backwards. Mine is totally different to yours, and is the one I said was bang on at 50 and 150. I'll put your data into Excel (actually it already is, chart it and fit a linear fit to it, aiming to make it evenly wrong across the whole span. But not now. Other things to do first.
    • Kinkstaah
      Mistakes were made, my R34 Story

      By Kinkstaah · Posted

      God damnit. The only option I actually have in the software is the one that is screenshotted. I am glad that I at least got it right... for those two points. Would it actually change anything if I chose/used 80C and 120C as the two points instead? My brain wants to imagine the formula put into HPtuners would be the same equation, otherwise none of this makes sense to me, unless: 1) The formula you put into VCM Scanner/HPTuners is always linear 2) The two points/input pairs are only arbitrary to choose (as the documentation implies) IF the actual scaling of the sensor is linear. then 3) If the scaling is not linear, the two points you choose matter a great deal, because the formula will draw a line between those two points only.
×
×
  • Create New...