boost increase = big flat spot + hesitation

[nick_w]

I have wound up the boost in my GTST R33 to 10psi with a turbosmart manual boost control valve and now it has a big flat spot and sometimes hesitates.

I have changed the plugs to 0.8 gap ones and have tried resetting the ecu. The ecu reset sometimes makes a big difference but only for that run and goes back to running like a dog when i turn it back off and on.

Any suggestions?

cheers

nick

96 GTST r33

cat back exhaust

sports panel filter

and stuff.

[Jay95R33]

You've encounted the flatspot that everyone hates

From what people have found is that it's the ECU either retarding the timing heaps for some reason, or the AFM is maxing out for a spit second.

I know what your feeling, and it's damn frustrating. From what I've read a S-AFC helps with the problem. Not much else can be done sadly :D

Otherwise it's a replacement ECU.

[Cubes]

Take some timing out of it..

Maybe some one previous has advanced the timing.

[Black33]

do many people encounter this?

cos I am going to increase boost to 10psi and I didn't want this to occur

[R34]

Everyone will encounter this characteristic unfortunately.

It's S-AFC or PFC etc to get rid of it and also increase power by leaning out the mixtures at the top end as the std ecu richens the fuel when it detects a boost increase.

Cheers

[rs73]

does the factory ECU actually richen the mixture when it detects increased boost at the top end/high rpm only or does it richen the mixture evenly across the rpm from the moment turbo spolls up?

[Cubes]

Try a few little things..

Make sure You are running 98 RON Fuel.. Ultimate 98 or Mobile Synergy 8000

..

Slap a bottle of Octane Boost... Nulon Pro Strength.. 7 Points.. for around $20 or $16.95 at KMart.

[Black33]

is this flat spot that bad and does everyone encounter it - I was about to install a blled valve next week to take it to 10psi but now.......????

Should I if it means I will have a big flat spot??? Will installing the bleed give me an increase in performance???

thanks guys

[rev210]

Originally posted by -Joel-

Slap a bottle of Octane Boost... Nulon Pro Strength.. 7 Points.. for around $20 or $16.95 at KMart.

Joel, don't waste the money on the 'so-called octane boosters' when they say upto 7 points they reffer to an octane increase maximum of 0.7 RON based on the lowest octane unleaded fuel it's boost is less on ultimate 98 and others. Toluene is a real octane booster:D

[Jay95R33]

Originally posted by Black33

is this flat spot that bad and does everyone encounter it - I was about to install a blled valve next week to take it to 10psi but now.......????  

Should I if it means I will have a big flat spot??? Will installing the bleed give me an increase in performance???

thanks guys

Most people will encounter some sort of flat spot when the boost is increased.

But believe me - the flat spot isn't really that bad compared to the increase in performace you get :uh-huh: :uh-huh: :burnout:

[Cubes]

Mine Doesn't..

But thats because its an R32.

What are the differences between the RB20DET's ecu and the RB25DET's ecu to make the RB25det's take out so much timing and over fuel so much.. I really can't understand this.

Or is it because of the crappy fuel in Aus and the RB25det's higher comp ratio doesn't run as well as the RB20det's.

[Jay95R33]

Joel,

I'm really not sure about that one. I know that the R32 ECU has bad ignition maps (for the RB20det), I'd say this is partly becuase of the lower quality fuel we use here. And the R33 ECU has bad ignition and fuel maps (for the RB25det), again, partly becuase of the fuel we use.

But I also read somewhere that Nissan made the maps to overfuel while on full boost to keep everything cool (piston tops etc.) So maybe it is due to the factory maps and us using lower RON fuel just makes it worse???

Not sure

J

[Cubes]

Easy Cheaper Fix.

The Z32 ECU is able to be remapped and apparently for the R33 you need to get the Z32 ECU that has the VCT capability.

Lots of loadpoints etc.. good fuel economy and no police hassles.

[Jay95R33]

Hay Joel,

Do you know if the Z32 ECU is a direct plugin for the R33's, or do you have to rewire it to suit??

[Cubes]

Yes you have to re-write it to suit obviously.

You can do the same with the RB20DET ECU for the R33 but you also have to make up a circuit to read the rpm and switch the solanoid on/off for the vct.

There was a discussion either here or on SDU about it.

I think it was in a Microtech discussion. Freebaggin was discussing (hehe) with the bloke.. Can't remember his alias but.

[Jay95R33]

Originally posted by -Joel-

Yes you have to re-write it to suit obviously.

You can do the same with the RB20DET ECU for the R33 but you also have to make up a circuit to read the rpm and switch the solanoid on/off for the vct.

There was a discussion either here or on SDU about it.

I think it was in a Microtech discussion. Freebaggin was discussing (hehe) with the bloke.. Can't remember his alias but.

Yepp - I understand that it needs rewriting. But what about the wiring??? Any ideas if the plugs and pinouts the same??

Thanks

J

[Cubes]

You would have to ask Tilbrooks that one..

[rs73]

I also intend to increase boost to 10 or 11psi but my exhaust is limiting so can't go more than 9psi at the moment. Secondly my boost bleed valve setup was not very correct. Nigel from ICE told me I had to block off the solenoid(?? is it correct) so that it's somewhat isolated from the new system, otherwise the ECU will keep hesitating.

However I've just got the HKS dragger back exhaust now, and next do I have to get a hi-flow cat to attach it? Here's a info phrase from Taka-kaira "They are designed to integrate into the factory exhaust system by bolting up to the factory b-pipe".

What's this b-pipe? Is it the section with resonator after the cat?

[Zer0]

Originally posted by Black33

is this flat spot that bad and does everyone encounter it - I was about to install a blled valve next week to take it to 10psi but now.......????  

Should I if it means I will have a big flat spot??? Will installing the bleed give me an increase in performance???

thanks guys

I wouldn't worry about it, I have a bleed on mine set to 10 PSI and it goes great. I have not noticed any flat spot at all and the performance increase at 10PSI is well worth it.

[Merli]

My post in the other thread addressed this problem...

Perhaps you should read it:

http://forums.skylinesaustralia.com/showth...t&threadid=3999