Help please, RB25DET runs better on 1/2 throttle!

[robbo_rb180]

Calm ya tits mate.....
Now everyone has given good advice on how to diagnose this issue. Take a look at who is giving advice by actually looking at their profiles & posts. Most of the people trying to help have been around for a long time. I'm guessing you are in the US so not many people have experience with these cars.

Check fuel pressure after the filter- will be blocked filter or dead fuel pump(I have seen a lot of walbro failures even with newish pumps). I have had a factory fuel reg fail only found it as had a guage & the tuner had swapped pumps.
you have the tools there- guages & wideband may as well spend the time to check it properly. 
If issue is still there after this  would just wait until you can book in to see a mechanic who has experience with skylines/rb cars.

[Dose Pipe Sutututu]

Needs more HKS SSQV, instant fix for any American. Go team Trump, last I heard he said there were 40 million people in Seoul, South Korea.

Maybe you should take the advice of people replying, might actually help you with your problem(s). Looks like fuel pressure and/or FPR being the aids.

[Tonyr33gtst]

Well I do appreciate your help lads, I have thanked everyone for their help numerous times. I will defo look at fuel pressure as that is what I thought it was in the first place. And thanks for the psi info on that. The ecu was done by a proper tuning company over here that tune many skylines. His opinion was to bring it in which I'd love to do but 300 miles from me and we can't go out. He suggested checking ecu and engine timing as may be in an anti lag situation. This car has an after market oil pressure gauge fitted. I could use that on the fuel couldn't I? Should give me some idea. Will put everything back in place and try and T in the fuel line after the filter to check it later today. 

I am still asking for help as the key question is why is the boost so high as im on actuator pressure which should be 5psi according to a previous post. My thought is if I get that to a normal place the car runs fine at that level of boost. 

As an aside, do stock ecus compensate fuel and timing up to 10psi or so if people use a boost controller? As if so mine dose not run well above 7psi so it would point to fuel pressure even more.

Plus I will not 'keep my hair on' as im bald! 

[KiwiRS4T]

25 minutes ago, Tonyr33gtst said:

Well I do appreciate your help lads, I have thanked everyone for their help numerous times. I will defo look at fuel pressure as that is what I thought it was in the first place. And thanks for the psi info on that. The ecu was done by a proper tuning company over here that tune many skylines. His opinion was to bring it in which I'd love to do but 300 miles from me and we can't go out. He suggested checking ecu and engine timing as may be in an anti lag situation. This car has an after market oil pressure gauge fitted. I could use that on the fuel couldn't I? Should give me some idea. Will put everything back in place and try and T in the fuel line after the filter to check it later today. 

I am still asking for help as the key question is why is the boost so high as im on actuator pressure which should be 5psi according to a previous post. My thought is if I get that to a normal place the car runs fine at that level of boost. 

As an aside, do stock ecus compensate fuel and timing up to 10psi or so if people use a boost controller? As if so mine dose not run well above 7psi so it would point to fuel pressure even more.

Plus I will not 'keep my hair on' as im bald! 

Stock ecu should be able to handle up to 12 psi but no telling what it has been tuned for. Check the timing and the fuel pressure and then start looking for boost leaks  etc etc.

[GTSBoy]

1 hour ago, Tonyr33gtst said:

As an aside, do stock ecus compensate fuel and timing up to 10psi or so if people use a boost controller? As if so mine dose not run well above 7psi so it would point to fuel pressure even more.

 

33 minutes ago, KiwiRS4T said:

Stock ecu should be able to handle up to 12 psi but no telling what it has been tuned for.

I'll have to argue against Kiwi's psi value. Stock 25 ECUs start getting real cranky after 10 psi. By 12 psi they are heavily into R&R, drinking fuel and making less power than they do at 11, and more often than not hammering the "boost cut" which is not a real boost cut, it works off the AFM signal.

But yes, there should be enough fuel available in the ECU mapping at 12 psi to keep the black smoke flowing while the engine chokes on 10:1 AFR.

You very likely have 2 problems. The first appears to be a shot fuel pump. You must diagnose and fix that first, because it will destroy your engine faster than the wastegate problem. The wastegate problem is less likely to be the actuator than the wastegate itself being stuck/worn/damaged in some way. But this is very easy to test. You just have to put some compressed air onto the actuator with a pressure gauge teed in to see how much pressure it takes to make it move. It should be fully open by 5 psi. You can dive deeper in and disconnect the actuator from the rod and see how freely the flapper moves. You'll be taking a lot of crap apart to get there, but it will be worth it for you to experience what you have to do to troubleshoot this stuff yourself.

[Tonyr33gtst]

3 hours ago, GTSBoy said:

 

I'll have to argue against Kiwi's psi value. Stock 25 ECUs start getting real cranky after 10 psi. By 12 psi they are heavily into R&R, drinking fuel and making less power than they do at 11, and more often than not hammering the "boost cut" which is not a real boost cut, it works off the AFM signal.

But yes, there should be enough fuel available in the ECU mapping at 12 psi to keep the black smoke flowing while the engine chokes on 10:1 AFR.

You very likely have 2 problems. The first appears to be a shot fuel pump. You must diagnose and fix that first, because it will destroy your engine faster than the wastegate problem. The wastegate problem is less likely to be the actuator than the wastegate itself being stuck/worn/damaged in some way. But this is very easy to test. You just have to put some compressed air onto the actuator with a pressure gauge teed in to see how much pressure it takes to make it move. It should be fully open by 5 psi. You can dive deeper in and disconnect the actuator from the rod and see how freely the flapper moves. You'll be taking a lot of crap apart to get there, but it will be worth it for you to experience what you have to do to troubleshoot this stuff yourself.

Awesome GTSBoy, thanks. I agree that it seems that it could be both lack of fuel and over boosting for some reason. Maybe its not a stock actuator on it as the car has been messed with in the past. It is an Auto so I have read that they are set to 20 deg timing not 15 like manual. Any truth in that?

Kiwi you mention check for boost leak but my problem is I have too much boost! Hence I wonder if its too retarded and making the turbo work like anti lag.

Im half tempted to advance it a little and do a quick test now everything has been cleaned and put back as I keep coming back to what the previous tuner said that he has expieriance of this and too retarded will cause white plugs and poor performance. He even suggested I try advancing a little to see.....I think I know what others will say but if I hear any detonation I will obv. stop straight away.

I don't have a timing light or obd1 consort reader. Do the cheap consort 14 pin readers work on ebay to see ecu timing? There seems to be no sensor I can use to adapt the oil electronic pressure gauge I have in the car which seems a shame as I am sure others would like to use one as a fuel pressure gauge. Any suggestions how I do this? A cheap pressure gauge may read rubbish anyway like a cheap engine compression tester I once bought.

I think I may just install my AEM wide band into this car as that should show me if fuel pressure is ok, Agree?????

Just looked into that and its far too much work to put the wideband in as I need to put another mount in the exhaust for it, I thought I could just swap it in place of the ordinary o2 sensor, Doh!

Edited April 8, 2020 by Tonyr33gtst

[GTSBoy]

54 minutes ago, Tonyr33gtst said:

Kiwi you mention check for boost leak but my problem is I have too much boost! Hence I wonder if its too retarded and making the turbo work like anti lag.

Un possible.

55 minutes ago, Tonyr33gtst said:

Im half tempted to advance it a little and do a quick test now everything has been cleaned and put back as I keep coming back to what the previous tuner said that he has expieriance of this and too retarded will cause white plugs and poor performance. He even suggested I try advancing a little to see.....I think I know what others will say but if I hear any detonation I will obv. stop straight away.

 

55 minutes ago, Tonyr33gtst said:

I don't have a timing light

The second quote is why you do not do what you plan in the 1st quote. Don't f**k with the timing blind. Just don't.

As to the 15° for manual and 20° for auto. I know that to be true for RB20. I don't know it to be true for 25s, but it could well be. The numbers are freely findable in the manual though......

57 minutes ago, Tonyr33gtst said:

Do the cheap consort 14 pin readers work on ebay to see ecu timing?

You CANNOT see the real timing at the ECU. That's why timing lights exist.

[Tonyr33gtst]

But you have to match what the ecu sees timing to cars actual one.

And un possible to be too retarded? This is how anti lag works. It also makes the plugs white as causes lots of heat. So does no one think this could be the case?

Edited April 8, 2020 by Tonyr33gtst

[KiwiRS4T]

You can't guess at timing - you need to set it at the CAS before you start tuning. From the R33 workshop manual:

[GTSBoy]

7 hours ago, Tonyr33gtst said:

And un possible to be too retarded?

Yes, given the range of physical adjustment available at the CAS.

Retarded means "Very f**king Retarded" when it comes to anti-lag. Which is actually a good description of it also.

[Ben C34]

Why all the guessing going on?

You have the ability to measure feul pressure. Timing lights are cheap as. A wideband is a sensible investment.

 

What are you expecting here? You can't guess this shit

[Tonyr33gtst]

Thanks, I will not guess at it, I will borrow/buy a timing light and check it properly. I need to work out a way to monitor the fuel pressure under load while driving as can't use a dyno at the moment. 

I can't fit my AEM wideband in it simply anywhere can I? If I replace the std o2 sensor I guess that throw the car into a limp style mode as ecu wont see the o2 signal? If the car will work I'd like to do that to see the afr as boost is fed in. If lower than say 12.5 to 11.5 then I doubt fuel pressure would be the issue.

Edited April 9, 2020 by Tonyr33gtst

[Dose Pipe Sutututu]

8 hours ago, Ben C34 said:

What are you expecting here? You can't guess this shit

To turn a few screws on the Holley Carb and fire a few shot guns into the air

[Dose Pipe Sutututu]

17 minutes ago, Tonyr33gtst said:

I can't fit my AEM wideband in it simply anywhere can I? If I replace the std o2 sensor I guess that throw the car into a limp style mode as ecu wont see the o2 signal?

You "can" however you'll reduce the sensor's life dramatically.

If you disconnect the stock O2, it won't throw anything into limp mode. You'll simply just lose your short term & long term fuel trims and it will peg rich on cruise.

[Tonyr33gtst]

46 minutes ago, Dose Pipe Sutututu said:

You "can" however you'll reduce the sensor's life dramatically.

If you disconnect the stock O2, it won't throw anything into limp mode. You'll simply just lose your short term & long term fuel trims and it will peg rich on cruise.

Cheers Dose Pipe, I guess that will defeat the object a bit as ecu will rich it up so will mess with afr reading anyway. On boost it may not matter though, as if not enough fuel it will still show up lean? 

[KiwiRS4T]

2 hours ago, Tonyr33gtst said:

Cheers Dose Pipe, I guess that will defeat the object a bit as ecu will rich it up so will mess with afr reading anyway. On boost it may not matter though, as if not enough fuel it will still show up lean? 

Yes.  Do it. Only your idle and cruise will be affected and its full throttle that you want to check. And the odds are your O2 sensor has never been changed anyway.

[Tonyr33gtst]

I guess the Marks are on my balancer pulley not cover. Which one indicates tdc and which one full advance? Looks like it goes 0,5,10,15,20,25,30 to me but left to right or right to left?

 

 

Edited April 9, 2020 by Tonyr33gtst

[Tonyr33gtst]

Found the answer online looks like left is tdc and they go up to 30degrees on the last right one. My car appears to be about 26-27 degrees! I'll try and adjust it down. It bounces around 2 degrees. I need to remove the TPS but it has 2 plugs which one should I remove please?

[Tonyr33gtst]

Well it's defo made it quicker and feels alot lot better as you would expect being over 10 degrees too advanced at near 27 deg I am pleased it was so far out and now it is much better drive. Timing strobe bounced about quite a lot like 2-3 degrees so I could be 13-17 degrees (I aimednfor the middle) so maybe getting it more exact may make it even better. Boosts to 10psi now as before I was seeing 14! It has a stage 1 ecu. Guess the advanced timing did something to the turbo boost.

It may have ok fuel pressure after all, but I intend to get that checked. When I can get it to a dyno. Hopefully this summer if we can get clear of this damn virus! 

Thanks all for your comments. It maybe we barked up the wrong tree with the fuel but I learnt stuff all the same. Should have checked timing first like the ecu tuner suggested after I managed to get a response from him. But by that time it was all fuel talk ?.

Pulled a plug and looks way better to me.

Edited April 9, 2020 by Tonyr33gtst

[GTSBoy]

It was probably pinging its tits off.

It is probably still lean. You have been warned.