Rb25Det Unique Problem

[SECURITY]

the effects of heat are minimal in comparison.

its because of the larger turbine drawing in and compressing the air, the larger compressor housing allowing larger masses of air to move as well as the larger exhaust housing that allows more air to exit the engine. its the same reason you get an increase in boost when installing a larger sports exhaust.

its like if somehow you fit a to4 turbine into a standard rb25 turbo housing (like a hiflow). you'd be able to hit 30psi of boost easily, but the efficiency range of the turbo will be at a much lower point then if it was in a larger housing, you probably wouldnt make any more power above 15psi, because the housing would be at 'max capacity', there would be no point in adding more pressure as the flow would still be the same.

[GTScotT]

so you honestly believe that this guys motor is a ticking time bomb at 10psi?

200cfm @ 10psi or 500cfm @ 10psi? See a problem here?

The standard AFM should be maxed long before the T04Z makes 10psi.... And it is anybodies guess how much actual airflow the T04Z is pushing @ 10psi.

Here are solid facts, flow = power. Psi does not = flow. There is a direct relationship between CFM and KW, that being said you can push what out of the stock injectors @ 100% duty? 220rwkw? That means there is 220kw of flow to be had out of them, exceed this and you MUST be leaning the motor out. Simple science.

Now a question; is it possible that the 450rwkw capable T04Z is pushing more than 220rwkw worth of flow @ 10psi? My answer is: highly likely. Next question is, is the ecu capable of retarding timing enough to bring it back to a safe level? My answer is: highly unlikely.

Next thing to note is that the WOT mixture is only a small percentage of the issue. Cruise and spool mixtures would be suffering badly due to the drastically increased airflow and the motor could be suffering from fuel wash (fuel destroying the oil providing the protective coat on cylinder bores) which would be burning rings. Get bad enough wash and you will contaminate the oil, risking your bearings while your at it. Fuel contamination is a major issue. Also, a motor can ping when rich and retarded, it depends how poor the tune is. In this case, VERY POOR.

[blind_elk]

... it is running quite rich i might add, i always thought if your not detonating, and running ruch, damage is near impossible

I believe that as well as detonating at lean mixtures, sometimes if the mixture is too rich will also cause detonation. Don't ask me why / how, I'm not an engineer, just heard somewhere.

One solution to the immediate problem is to not drive the car like a maniac.

[Legionnaire]

I think what JonnoHR31 is trying to say is that AFM will be maxed well before factory injectors reach anything like 100%, and on a fully standard ECU air overflowing countermeasures will be activated well before AFM is maxed out. So dude is constantly hitting airflow limiter. Feels like crap, but unlikely kills an engine.

There is no direct relationship between CFM and KW, but there is a relationship between lb/min (or KG/sec) and SFC/AFRs and KW.

So equations look like this: power = mass flow, mass flow through AFM = certain voltage output, any voltage above 4 volts (a whole good volt to go to maxing AFM out) or so = fuel cut, fuel cut = no fuel, no fuel = no power to drive turbine = no mass flow.

To OP: crappy and poorly thought out engine setups are hardly a unique problem. Read as much as you can on the subject, SAU is invaluable source of this kind of info and has examples for almost any king of setup you can think of, and get yourself at least some tuneable ECU, as mentioned above, MAP-based ECUs are preferred if you're going to keep that T04Z for a 2.5 litre engine.

Edited February 8, 2011 by Legionnaire

[SLYDA]

Hey mate, I get the impression you are being serious... So I will give you as best a response as I can.

The above guys are actually correct. Your problem is your ECU. The ECU is not able to cope with the change to the new turbo.

To put it simply, pressure (boost) and volume (actual amount) are not relevant to each other. That means that 10psi from the stock turbo will be far less compressed air (power to be made) than 10psi from the T04Z.

Your car is literally a ticking time bomb, and I can assure you that if you persist you will blow the motor very soon.

You will need the following items ASAP:

700cc+ injectors

A good fuel pump (if you dont have already)

A map based ECU (running a Z32 AFM wont cut the mustard for a T04Z)

To all experienced forum members, can you please simply +1 my post if you agree. I believe the guy is being honest and is not long off wasting 3 years of hard work on his car and motor.

GL

+1, I'd love to see the condition of the internals of that engine, even at 10PSI with a GT2835, Standard injectors and a PowerFC running its base map my injectors were maxing 100% injector duty, this was back when i was a noob years and years ago, way to hardcore lean out your engine.

Incredibly stupid to spend all that money and forget the MOST important part of your build that should have been done IMMEDIATELY upon changing the turbo, hes also right about the Z32.. the resolution of a Z32 AFM will be shit with a turbo that big you need something like a Microtech that uses a MAP sensor not a MAF sensor.

[wolverine]

^^ no one "needs" a Microtech

[Beer Baron]

I think what is trying to be said here is that a bigger turbo will flow more air for a given pressure, hence being a "bigger" turbo.

A small turbo such as your stock one will flow considerably LESS at 10psi than a big turbo such as the T04Z (800hp turbo?) at 10psi.

Our stock ECU's read air FLOW, not pressure.

My guess as to what is happening is that the T04Z is pushing so much air that your stock ECU is throwing a fit, you've also most definitely maxed your airflow meter.

this post summed it up. the problem is this. PSI is just a pressure rating. it's a measure of restriction in the intake as such. it's not a measure of AIRFLOW. what does your standard ECU use to determine fuelling? AIRFLOW. a small turbo at 10psi will be flowing much less air than a larger turbo at 10psi. the boos pressure is not relevant. if they all flowed the same amount of air at any given psi then we'd all be running the smallest possible turbo and running it at 30psi. it's simply not the case. your problem now is your T04Z flows too much air even at 10psi for the standard ECU to handle. you need an aftermarket ecu.

since you have an auto it limits your options a little bit, but speak to a workshop who has some experience tuning R34 GTTs with auto boxes. you will also need a fuel system that is capable of providing enough fuel for the amount of air this turbo can flow.

my advice, stop driving the car, or at worst drive it slowly and carefully to a workshop and get it sorted out. it's going to need a decent tune to go with that new ecu anyway.

[bubba]

this post summed it up. the problem is this. PSI is just a pressure rating. it's a measure of restriction in the intake as such. it's not a measure of AIRFLOW. what does your standard ECU use to determine fuelling? AIRFLOW. a small turbo at 10psi will be flowing much less air than a larger turbo at 10psi. the boos pressure is not relevant. if they all flowed the same amount of air at any given psi then we'd all be running the smallest possible turbo and running it at 30psi. it's simply not the case. your problem now is your T04Z flows too much air even at 10psi for the standard ECU to handle. you need an aftermarket ecu.

since you have an auto it limits your options a little bit, but speak to a workshop who has some experience tuning R34 GTTs with auto boxes. you will also need a fuel system that is capable of providing enough fuel for the amount of air this turbo can flow.

my advice, stop driving the car, or at worst drive it slowly and carefully to a workshop and get it sorted out. it's going to need a decent tune to go with that new ecu anyway.

Oh it's a 34GTT auto?? Best solution is NIStune (I have one for my auto Neo'd Stagea).

[jrm]

Oh it's a 34GTT auto?? Best solution is NIStune (I have one for my auto Neo'd Stagea).

Original posts say R33 auto, think someone got confused.

R33 will probably mean conversion R32 ECU or Z32 ECU (to retain VCT) + nistune .. straight forward enough for most workshops.

[d1_drifter]

What is an un-tuned 25 with a T04Z even like to drive, let alone being auto?

A powerband of 1k, taking a year to spool and being hosed by stockers. Do not want.

Edited February 8, 2011 by d1_drifter

[DVS JEZ]

before i knew any better i was running my old GTR with T04z with stock ecu and injectors etc for 3 months & 1500k's was running it in, normal driving was fine, boosted up hard and was running 10psi with a 50mm external gate.

now that i know better i would not recommend this to anyone however, and due to the above point i will jump on the band wagon and say that the stock ecu MAY be able to handle it for a little while.

the post about fuel wash i think isnt correct, no matter what turbo is on the car, the TP on the stock ecu(load point) when cruising is run on the load table of the ecu, the load point selected by the ecu is governed alot by the airflow meter signal,

eg

3000rpm with stock turbo will be ramping hard onto boost and on a fairly high load point (TP).

3000rpm with a T04Z will be starting to spool and will be on a lower load point (TP)

so cruising with a T04Z will be fine.

[senilykSkylines]

Honestly confused.

How does 10psi with different turbos differ?

I can understand the explanation of different temperatures. 10psi of cold air will have more oxygen than 10psi of warmer air... hence why I want to get a front mount one day

Regarding more air FLOW is what is confusing me. Does what determines it, is where the psi is recorded from? The engine will only take in as much as it takes in at 10psi hot or cold. How can you have more air flow with the same pressurised condensed air from different turbos.... bar differences in temperature (Which determines how much oxygen is present in that pressurised air).

cheers,

[SECURITY]

you've got to be fucking troll right? you cant be serious.

[Randon_I_Am]

Think about this.

The exhaust housing of a smaller turbo can only let so much exhaust gas/air out of the engine before it gets choked up.

chuck on a bugger turbo, bigger exhaust housing can let a lot more exhaust gas/air out of the engine, meaning a lot more air has to be going into the engine to create the same level of restriction/intake resistance (psi).

So for the two different turbos there is a huge difference in FLOW eg, amount of air going into the engine, for a given PSI.

[wolverine]

Imagine you blow as hard as you into a plastic bottle. The pressure inside the bottle will be high. Airflow = zero

Poke a 5mm hole in the bottom and blow again. The pressure will drop but airflow has now increased.

Poke a 20mm hole in the bottom and the pressure inside drops again but airflow goes up.

Cut the bottom off the bottle and now the pressure is very low inside the bottle but airflow is at its highest.

Beerbaron covered it nicely, re-read what he wrote.

[GTScotT]

Ever done any diving? The deeper you go the more pressure there is right? Yet one cubic meter of water is still one cubic meter of water...

How about flying? Do you know the reason turbos were created? It is so that old school (non jet) plane engines would not stall when they hit high altitudes.. Why? Because there is lower pressure up that high.. Standard atmospheric pressure is 1 bar, yes you are breathing one bar of atmospheric pressure right now. The planes turbo kept the motor running at atmospheric pressure so it could breathe. Again, one meter squared 30,000ft in the sky is still one meter squared on the ground...

Consider flow to be volume. As stated, it has no direct relationship with pressure.

As wolverine said... Take a 600ml coke bottle... It holds 600ml of... Coke? Whatever, its capacity is 600ml end of story. Leave it open at atmo pressure, it will hold 600ml.. Put your mouth over it and blow pressure into it... How much will it hold once theres some form of above atmospheric pressure? 600ml right? Right.

One more word to take into consideration. Density.

Once you start reading into turbos WAY more, you will end up having to calculate the density of air that is being pushed (mass). Calculating air in GRAMS will really throw you off

[onboostR33]

hey dude these guys are right the bigger turbo will push more air out of it just look at the inlet size of your to4 copared to the stock one it is the volume of air PSI is pounds per square inch there fore this is the force the air has not the volume of air your ecu is probally retarding the timming at this rev range and you air flow meter cann not read the amount of air that is being pushed througt it im running a gt 35/40 turbo with a micro tech lt10s ecu with a map sensor that is better than an air flow meter map sensor reads the manifold absolutte pressure no need for air flow meter INVEST in a good ECU this will make or brake your engine all these mods are a waste of time if you are not controlling your fuel / spark properly!!

[SargeRX8]

It's the difference between breathing through a star and breathing through your nose. Try t. Through a straw you will flow a small amount of air and suffocate your self and will create a high amount of pressure trying to suck air in. But if you breathe through your mouth or a really big straw you can suck in just as hard bu get alot more air in.

Back to op. Ecu is the biggie. It's the backbone of the car. It's the brain. It's the control. I plan to mod my car and have my ecu on the way. Luckily it's tuned for a stock turbo and what not but boosted up to 10psi. But again I won't be smashing it often until I get it checked out with my car.

[senilykSkylines]

Thanks for your replies guys, I'll get my head around it one day. Still what I am confused about is that my boost gauge lead is taking the boost pressure right at the intake just before it goes into the engine. So both turbos are having to move 10psi of air through the same size (volume) intake pipe all the way to the boost gage sensor as it enters the engine.

If I get a bigger turbo do I get a bigger pipe? In that case it will be running more flow of air at 10 psi because of a bigger intake pipe.

I UNDERSTAND that a Bigger turbo is capable of moving more air.

With the illustrations of the bottle I am guessing that your mouth is the turbo and the bottle is the intake pipe? Whether bigger or smaller lungs, if they hold the bottle at 10psi and leak out of a little hole... how is it different.

I know I am missing something somewhere.

[simpletool]

OK ECU is obviously the problem. He should use Nistune and a much larger AFM (Ford lightning or custom housing around a Z32 element).

But....Nobody has asked why he has a T04z. I mean sure..it's a nice turbo...but do you REALLY need one that big?

Can the stock auto even handle 600Nm + ?