uppped boost problems

[xr8eater]

the story is like this my r33 gts-t s-2 orignaly had a problem of mis fireing at 5000 rpm i gapped the plugs down and eliminated the problem. irecently baught a single stage boost controller and upped the boost to approx 10 psi the orignal problem is back with slight stammering at 5000rpm onwards if i gapp the plugs in more will this solve the problem or is this a cause of the fuel thining out to much and need to decrese the boost

i need some constructive imput guys

[PTR33]

Mine has been running at 10PSI for about 8 months without as much as a hiccough. AFR at peak power is still down below 11/1 so fuel is unlikely to be a problem.

[Fly_With_Sky]

if youve now got your plugs at a smaller gap my only conclusion is that you are hitting boost cut. this leaves you with a few options

1. buy a fuel cut defender

2. buy and aftermarket ecu

3. put the thing on a dyno and find out whats wrong and then go from there

[riggaP]

if youve now got your plugs at a smaller gap my only conclusion is that you are hitting boost cut. this leaves you with a few options

1. buy a fuel cut defender

2. buy and aftermarket ecu

3. put the thing on a dyno and find out whats wrong and then go from there

:werd:

Definitely the boost cut. Piggy back ECU is probably the best option.

[croat]

i have the same problem. There should not be a boost cut at 10psi on an r33 series 1. My mate runs 12 everyday no problems and no other mods but exhaust and fmic...

[xr8eater]

true there should not be a fuel cut or a boost limter at 10 psi i have an after market air filter and a cat back exaust would this have any efect to other systems to cause this problem

thanks for your replys guys keep them coming

[JaFF]

I have the same problem. when i flick to 10 psi it stammers at like 5000rpm

I have sparks gapped to .8 but no good. When running stock it is pretty much fine.

I think i'll get a SAFCII to fix the problem.

[Guest Robo's]

Sounds like its overfueling when you increase boost which is a typical problem. Get a cheap SAFC and that will fix it all and give you some nice extra power.

[superspit]

PLUGS!! at these pressures (8-13 psi), everything should still be able to cope well!!

Mine is stock, accept for what I've posted on avatar.

Mine went to over 12psi for 3 months with no issues. Now back to 10.5psi and safer.

My point is those bloody spark plug gaps should never be taken for granted!!!

Mine had to go down to .7mm before those embarrassing 'shudders and spits' left the building. Been going for 3 months at that .7 setting now, ...still ace. (Miss my boost control though!!) PLUGS!!!

[xr8eater]

where can i find a cheep safc robo realy where can i find one ? Ill try gapping them down again to .70 see what happens

[Guest Robo's]

SAFC's are about $300, try the gap problem first but your best bet would be the SAFC and it should help with some extra power too.

[Zahos]

Sounds like its overfueling when you increase boost which is a typical problem. Get a cheap SAFC and that will fix it all and give you some nice extra power.

:werd:

I have read "it's probably boost cut" about 1,000,000 times, but have never read 1 case where that WAS the problem....

I once tuned my boost controller too far and got boost cut, or my AFM maxing out.. whatever you wanna call it, but it was off the guage (over 1.5 bar! (> 21 psi) How much over, I have no idea b/c that's all my guage goes up to)

If a SAFC doesn't fix the problem, (it will definately make it much better), then you have faulty and/or cracked coils.

If the coils are cracked, but not faulty (which it sounds to be the case, otherwise it would run like a dog constantly), then it's an easy fix, just get the cracks plastic welded.

Once your coils are sorted and your A/F ratio's are sorted, then you could re-gap them to 0.8mm (bigger gap, bigger spark / smaller gap, stronger spark - but there has to be a tradeoff)

I got a SAFC and it cured my problem....

then it came back....

So I taped my coils up as described in another thread, but the tape shrunk, and the cracks appeared again....

SO

I used a soldering iron to melt some plastic over the cracks in my coils and it runs soooo smooth now.... I don't know how long it will last, but I'm guessing not that long as melting plastic like that does not fuse the 2 together properly. Plastic welding the cracks would be a much better alternative.

Good luck sorting it all out. The scenarios I have listed are the most common causes of these symptoms as discovered by people when they sorted it out. Boost cut is the most common answer you will get from keyboard tuners.

Zahos

[riggaP]

Zahos, I think the terms "boost cut" and "over boost protection" are being confused. You are right. The term is not "boost cut", its "over boost protection". Also, how could users of this, or any other performance forum be anything but "keyboard tuners"?

My car had the same problem. Anything over about 10psi would cause misfire around 5000rpm. It was previously worse (miss @ stock psi) before the plugs were regapped to 0.8. I got a hold of a chipped ECU and this solved the problem. Now I'm running 13psi without any dramas.

[JaFF]

meh! where can i get a chipped ecu? also how much is a chipped ecu? would u be better off getting a SAFC anyway?

[GunMetalR33]

Where on your coil packs did you find the cracks? were they easy to spot?

crack

:werd:

 

 I have read "it's probably boost cut" about 1,000,000 times, but have never read 1 case where that WAS the problem....

I once tuned my boost controller too far and got boost cut, or my AFM maxing out.. whatever you wanna call it, but it was off the guage (over 1.5 bar! (> 21 psi) How much over, I have no idea b/c that's all my guage goes up to)

 

 If a SAFC doesn't fix the problem, (it will definately make it much better), then you have faulty and/or cracked coils.

If the coils are cracked, but not faulty (which it sounds to be the case, otherwise it would run like a dog constantly), then it's an easy fix, just get the cracks plastic welded.

 

Once your coils are sorted and your A/F ratio's are sorted, then you could re-gap them to 0.8mm (bigger gap, bigger spark / smaller gap, stronger spark - but there has to be a tradeoff)

 

 I got a SAFC and it cured my problem....

 then it came back....

 So I taped my coils up as described in another thread, but the tape shrunk, and the cracks appeared again....

 

 SO

 

I used a soldering iron to melt some plastic over the cracks in my coils and it runs soooo smooth now.... I don't know how long it will last, but I'm guessing not that long as melting plastic like that does not fuse the 2 together properly. Plastic welding the cracks would be a much better alternative.

 

Good luck sorting it all out. The scenarios I have listed are the most common causes of these symptoms as discovered by people when they sorted it out. Boost cut is the most common answer you will get from keyboard tuners.

 

 Zahos

[600hp]

grab some splitfire coil packs that should fix any ignition problems.

i've seen them for 500 bucks. maybe nengun?

[riggaP]

meh! where can i get a chipped ecu? also how much is a chipped ecu? would u be better off getting a SAFC anyway?

Not really worth getting the stock ECU chipped. You could get a PFC for a little bit more now. I got mine 2nd hand for $150 An AFC would be your best bet.

[Zahos]

Where on your coil packs did you find the cracks? were they easy to spot?

 crack

Check this picture out. It shows where they crack.

On 4 of my coil packs, i had to hold them a certain angle in the sunlight to see the crack b/c it was so thin. On most of the ones I bought, I could see it quite easily.

I would be getting all 6 plastic welded, even the ones that aren't cracked. They crack because of fatigue in the plastic. A cracked cover on a coil does not mean that the coil has anything else wrong... it usually still functions, but poorly.

The ones that aren't cracked are almost certain to do so, whether it be in the near or distant future....

Zahos

[GunMetalR33]

Zahos:

Thanks for the info mate!!!!

[Sydneykid]

Hi XR8eater, "Over boost protection" is what it is know as, but it is really "excessive airflow protection". The ecu makes this decision based on what the AFM is telling it. So boost really has nothing to do with it. The fix is an SAFC, voltage clamp, Boost Cut Defeater or better still replace the std ecu with a Power FC. Full fuel cut is the next step in engine protection programming in the ECU, but you get "retard" and "rich" first.

Here is a post I prepared earlier that may help

.................................................. .................................................. ...

Hi guys, a quick, simplistic explanation of how an SAFC works might help...

As the airflow into the engine increase, the AFM records this as increased voltage that the ECU sees. What an SAFC does is sit in between the AFM and the ECU and take the voltages from the AFM and either increase or decrease them depending on what you have programmed the SAFC to do. By increasing the voltage, this tricks the ecu into pumping in more fuel, you do this when the engine is running lean. By decreasing the voltage, this tricks the ecu into pumping in less fuel, you do this when the engine is running rich.

The next bit is hard to understand unless you remember that the standard ecu does not supply fuel in direct proportion to the afm voltage ie; 4 volts is not twice as much fuel as 2 volts. Engine rpm, boost and throttle position also help the ecu determine how much fuel to add.

It has been my experience that RB25's run a little lean down low in the rpm range (Nissan do this for fuel economy and emissions) and a lot rich up high (Nissan do this to protect the engine). So I have to increase the voltage (using the SAFC) up to around 3,000 rpm and decrease the voltage over 5,000 rpm.

The real problem is in the 3,000 to 5,000 rpm range as the engine comes on boost. They really need lots of fuel very quickly in this area. This can mean that you need to increase the voltage (that the ecu sees) over 5.1 volts to get the right A/F ratios. The ecu then goes into engine protection mode, rich and retarded (sounds like a girl I knew once). Past that rpm you can start leaning it out as it runs too rich, so the voltage needs to be turned down under 5.1 volts. The ecu sees this as the engine not needing protection mode any more, no more rich and retarded.

So you get good performance up to 3,000 rpm, then sluggish from 3,000 rpm to 5,000 rpm and then good performance from 5,000 rpm and over. The SAFC may not help this, in fact as explained above, it can in fact make it worse if the tuner is not switched on to this stuff.

With bent afm voltages, the ecu (tricked by the SAFC) also fires the ignition to suite the airflow it THINKS the engine is getting. This is not a good thing as you generally end up with ignition that is too far advanced in some rpm ranges.

The poor tuner has to juggle the SAFC settings, so that the A/F ratios are OK, the ecu doesn't get into rich and retard (engine protection) mode and the ignition timing is not too far advanced so as to cause detonation. My experience (I am not a good tuner) has been that this is full of compromises, sometimes you just can't win and have to reduce the boost level a bit to get even a reasonable compromise.

Keep in mind that this explanation is very simplified to make it fit in a reasonable space, the rpm's used are rough guides only and every car is different.

Hope it helps (and makes some sense).