Quiet Screamer Pipe

[**RB2530**]

How do you get around the air flow cut ? is the ecu remapped at all? like one of those jap ones?

good work... will you do mine for $150 ?

I have an interesting theory on the air flow cut...That is that the air flow cut only operates at around 4000rpm...so if the airflow is under the threshold at 4000 rpm (or whatever the rpm setpoint is), but then increases after that, the ECU doesn't react. ie the airflow cut is only actively monitoring airflow at one point in the rev range...

So if you had a boost vs rpm curve where the boost is under the airflow cut limit at 4000 rpm but then increases after 4000 rpm you effectively bypass the airflow cut...I discovered this accidently one time when I had a boost spiking problem. I was using a cheapshit chinese t3/t4 and the hole in the turbine housing for the WG was too small...This was causing the boost to keep increasing becuase the WG could not bleed off enough exhaust...(Now I use a genuine Garrett GT3076R)

Now what I found was that when the boost would spike up to about 1.3 bar in the 6000-7000 rpm range and I would still not hit airflow cut??...When I fixed the boost spike problem and ended up with a lot flatter boost control I would hit airflow cut quite severley (at about 4000rpm lose 100% power) even at 1.1 bar...As soon as dropped off the boost to 0.9bar there was no problem at 4000rpm or any other rpm point.

In thinking about the airflow cut and what it is meant to achieve, I thought this makes sense...The standard ECU is designed with safety feartures to protect against detonating the engine due to bad fuel and or other component failures...A very common mode of failure is WG actuator failing to open due to disconnection of hose, damage to the hose or WG jamming closed...With standard turbo setup full boost is achieved at say 3000rpm and can really spike up to high boosts very quickly. The air flow cut 'I think' is designed to protect the engine should this factory boost control fail. I dont think it is a protection against people putting doing heaps of mods...As soon as obvious mods are done the factory warranty is voided and it is no longer Nissans problem...

So based on this a smaller turbo is more likely to create an airflow cut problem than a bigger turbo would. Ie Turbo lag from large turbo helps you get past or underneath the airflow cut at 4000rpm... ie smaller turbos make peak boost right at the point where air flow is active and large turbos dont...

Now what I have done is use about 4deg retard on exhaust to change the spool characteric of the turbo...ie taken out a bit of mid range efficiency so that the airflow at 4000rpm doesn;t exceed the airflow cut parameter. Then above 4000rpm it all starts to work..

[**RB2530**]

just a quick question, where abouts do you buy them steel straps that u use to hold your heat wrap on?

The straps are called Panduit straps...They are the same straps that they use for CV boots sometimes.... Not that you would but they would be nearly good enough for IC piping..I have a tool that tensions them as well...Tool is worth about $300 though...

They are awesome and I have never had one let go...

[govich]

So based on this a smaller turbo is more likely to create an airflow cut problem than a bigger turbo would. Ie Turbo lag from large turbo helps you get past or underneath the airflow cut at 4000rpm... ie smaller turbos make peak boost right at the point where air flow is active and large turbos dont...

Boost pressure and airflow are not necessarily directly related. There are a lot of other factors including the compressor size that will have a large impact on how much air will pass through the AFM. A smaller compressor will have lesser flow capability, all else constant, than a larger compressor. So assuming the AFM measures air flow, and Nissan's ECU is programmed to not like high flow values, the bigger turbo will create more problems.

The ECU actively monitors the voltage output from the AFM throughout the operating range of the engine and uses it to ...well..run the engine. It doesn't guess how much fuel is needed to get programmed air fuel ratios.

Edited March 6, 2008 by govich

[full house]

good work dude! Just a little confusing about the pics, is it upside down?

[sh@un]

that is so damn bollocksing coool man!!! i been thinking about doing a mod like this for years now, except i was going to run a cat on it and run it all the way to the rear of the car to try and make it legal.

'cept, if you weren't on the gate a whole heap, the cat wouldn't get up to temperature and work properly anyway

[**RB2530**]

Boost pressure and airflow are not necessarily directly related. There are a lot of other factors including the compressor size that will have a large impact on how much air will pass through the AFM. A smaller compressor will have lesser flow capability, all else constant, than a larger compressor. So assuming the AFM measures air flow, and Nissan's ECU is programmed to not like high flow values, the bigger turbo will create more problems.

The ECU actively monitors the voltage output from the AFM throughout the operating range of the engine and uses it to ...well..run the engine. It doesn't guess how much fuel is needed to get programmed air fuel ratios.

At constant boost presssure, air flow into the engine will increase with increasing engine rpm...The reason I refer to boost pressure is that the control regime for the turbo is based on boost pressure and not airflow..ie a boost pressure feedback regime is used as opposed to airflow feedback to control WG

Anyway what I am saying is that Nissan's ECU airflow cut is only active at around 4000rpm... It is definitely not active above 6500rpm because this is the region where I get a constant 5.12V airflow signal right up to rev limit...I am actually saturating the air flow input (more commonly referred to by some as maxing out)...5.12V corresponds to the maximum voltage that the Nissan ECU's A-D convertor will register....Now at this point in time the ECU is on its air flow upper limit but the engine is still pulling hard...ie no ignition cut or anything...Therefore airflow cut in the 6500-7000rpm range is not active and my guess is that it is active around 4000rpm only...

All that said I look forward to the day I dont have to play tricks and games with the stock ECU and make some real kW

[R31Nismoid]

good work dude! Just a little confusing about the pics, is it upside down?

Pics 1 & 2 are from the passenger side, UNDER the car.

Pic 3 is from the drivers side, UNDER again

So none are upside down

[govich]

Anyway what I am saying is that Nissan's ECU airflow cut is only active at around 4000rpm... It is definitely not active above 6500rpm because this is the region where I get a constant 5.12V airflow signal right up to rev limit...I am actually saturating the air flow input (more commonly referred to by some as maxing out)...5.12V corresponds to the maximum voltage that the Nissan ECU's A-D convertor will register....Now at this point in time the ECU is on its air flow upper limit but the engine is still pulling hard...ie no ignition cut or anything...Therefore airflow cut in the 6500-7000rpm range is not active and my guess is that it is active around 4000rpm only..

Fair enough.

Perhaps it's got something to do with NVCS? The ECU could be programmed to limit the amount of airflow into the engine with the advanced timing on the inlet cam. NVCS is active until 4500rpm i believe. Purely speculating but it could make sense.. That or it maps timing vs airflow or similar and doesn't like going past whatever value.

Edited March 6, 2008 by govich

[GeeTR]

yer it is good guess

Have my moments

[Guilt-Toy]

yeah i did notice that it only happens at 4000rpm... that must be a massive lag monster you have there

But still thats good that you have gotten around the problem.

Not interested in plumbing up my screamer? I love the work you did to yours.. that is awesome

Edited March 7, 2008 by Guilt-Toy

[**RB2530**]

yeah i did notice that it only happens at 4000rpm... that must be a massive lag monster you have there

But still thats good that you have gotten around the problem.

Not interested in plumbing up my screamer? I love the work you did to yours.. that is awesome

Nah I wouldn't say that my car is laggy at all. When I got it was stock and yes it is laggy compared to stock..The boost starts to come on relatively early (say 3000 rpm) but does not acheive its set point until above 4000rpm. Dont forget I said earlier that I retard the exhaust cam timing by about 4deg...This makes the engine less efficient in the mid rpm range and more efficient in the upper rpm range...If I run stock cam timing I can hit airflow cut easier even at lower boost so I am cheating in way. I am effectively detuning the car around 4000 rpm to get under the air flow cut... I cant wait to get aftermarket ECU so I dont have to do this...I already have some 660cc Siemens injectors and a fuel rail made up...Also have brand spankin new Z32 afm sitting on the shelf right to go...Even has the spare plug...

As far as plumbing up your screamer I would be happy to do it but then my gf would then start screaming at me...I've spent so much time on my own car at the moment and not with her... I spent 10 hours doing my one.

I actually got the muffler from Wallsend muffler service..He sortof knows me and knew what I was doing so if you go in there I am sure he would help you out...Just tell him the guy with the Black Skyline sent you...He also has some 2nd hand mandrel bends and heaps of other bit and pieces pretty cheap. I always go to him first for stuff..Use my photos if you want..

Btw I think I know a mate of yours...Grant with the silver GTSt 4 door. He had a drive of my car at this party we went to..He is related to my neighbour...small world...

[stolen_s15]

Two comments.

You have far too much time on your hands.

&

That is so cool!

[Guilt-Toy]

yeah grants a good mate of mine, i tuned his car for him a few times..

I am hireing a Dyno in newcastle tomorrow so if you wanted to come along I can do some power runs for you for $40...

Send me a PM if i dont get back to you get a hold of grant, he can give you my details.

Nah I wouldn't say that my car is laggy at all. When I got it was stock and yes it is laggy compared to stock..The boost starts to come on relatively early (say 3000 rpm) but does not acheive its set point until above 4000rpm. Dont forget I said earlier that I retard the exhaust cam timing by about 4deg...This makes the engine less efficient in the mid rpm range and more efficient in the upper rpm range...If I run stock cam timing I can hit airflow cut easier even at lower boost so I am cheating in way. I am effectively detuning the car around 4000 rpm to get under the air flow cut... I cant wait to get aftermarket ECU so I dont have to do this...I already have some 660cc Siemens injectors and a fuel rail made up...Also have brand spankin new Z32 afm sitting on the shelf right to go...Even has the spare plug...

As far as plumbing up your screamer I would be happy to do it but then my gf would then start screaming at me...I've spent so much time on my own car at the moment and not with her... I spent 10 hours doing my one.

I actually got the muffler from Wallsend muffler service..He sortof knows me and knew what I was doing so if you go in there I am sure he would help you out...Just tell him the guy with the Black Skyline sent you...He also has some 2nd hand mandrel bends and heaps of other bit and pieces pretty cheap. I always go to him first for stuff..Use my photos if you want..

Btw I think I know a mate of yours...Grant with the silver GTSt 4 door. He had a drive of my car at this party we went to..He is related to my neighbour...small world...

[**RB2530**]

For those interested in what the Std ECU can do, Guilt-Toy did some Dyno power runs for me today and results are as follows:

Dyno Dynamics Dynamometer at TurboTechnics Cardiff...

Run 1. 230rwkW at 9psi with AFR = 12.1

Run 2. 265rwkW at 11psi with AFR = 12.2

Run 3. 278 rwkW at 13 psi with AFR = 12.5

Didnt attempt any more boost...I was already happy enough!!

On Run 2 and Run 3 there was a little bit of ignition breakdown due to stock plug gap (didn't have time to regap plugs) but apart from that it was all cool...No sign of airflow cut or anything else scary

And also no-one heard the screamer pipe!!!

Will post up charts once scanned as well as Nissan Consult data...

Thanks Guilt-toy!!! Power FC master!!! and soon to be Std ECU master!!!

[govich]

Are you sure the ECU is internally standard? I'm a bit skeptical because noone seems to have come across this before..

[R338OY]

Hmmm, maybe i won't bother buying a PFC...

[**RB2530**]

Are you sure the ECU is internally standard? I'm a bit skeptical because noone seems to have come across this before..

Well I will check it but I doubt it has been modified...car was very stock and I mean very stock when I got it...in fact it had no mods at all...and no sign of mods that had been put back to stock..

[govich]

Well I will check it but I doubt it has been modified...car was very stock and I mean very stock when I got it...in fact it had no mods at all...and no sign of mods that had been put back to stock..

Nice. I guess it just shows how little we really know about nissan's ecu.. It'll be interesting to see the printouts

[MR 33]

You'd be surprised what the Japs get up to! My car was dead stock off the boat and reeled off 156rwkw. Upon installing the pfc i came across the Mines ecu that was hiding away in the kick panel!

[**RB2530**]

You'd be surprised what the Japs get up to! My car was dead stock off the boat and reeled off 156rwkw. Upon installing the pfc i came across the Mines ecu that was hiding away in the kick panel!

Well when I first got the car I did all the standard basic mods and found the air flow cut very quickly...the ECU is definately Nissan because I use the Nissan consult software...I don't think other ECUs would work with the software....

AND..Please read my previous posts carefully...the airflow cut is still there but in knowing a little bit about how it works, I have gotten around it...