Attn:SK some ideas to help keep the 25ECU out of "Rich and Retard Mode"

[RB30-POWER]

SK or others that could offer some real advice can you offer some ideas or suggestions on the following.

I have just completed an RB25/30 running factory managment so far, now I only have a small stocker type turbo on it at the moment.

Now before i boost it up to much, knowing that the ecu will pull the timing (RICH AND RETARD) if i trip the 5.1V mark on the AFM, I done some measurements.

At around 4500 it peaks at around 4.7V @ 4-5PSI boost pressure.

I gather that this is the point of greatest VE, hence it breathing most Air.

Now what i want to know is how much more boost do you think it would take to trip the 5.1V mark. (I guess only a few PSI extra and a cold night will allow it to measure that sort of voltage)

What is the best work around for the time being?

Should I work the boost curve so that it drops a few PSI at that point keeping it all below 5.1V

or

Should i get an interceptor and just lower the Voltage from the AFM that the ECU sees. (I guess it will get lean preety quick, or is the mapping preety rich anyway at that point, that i could drop it under the 5.1V and still have ok mixtures?

Now lastly, even if i got a PowerFC, with this small turbo and more boost its going to measure way over 5.1V, so the only way around it will be to get a bigger Air Flow Meter correct, one that reads less voltage for the given air flow.

Im thinking i may also be able to fool the 25 AFM a bit by removing the mesh elements/screens, allowing a tiny bit (maybe 10%, i've heard) more flow through the meter, without the meter measuring it.

Also one other thing, on the AFM i have an adapter and pod, but the adapter steps from 80mm to 70mm, do you think this could be causing the meter to measure a bit high as well, or it shouldn't effect it to much?

Thankyou for any ideas, sorry about the long post, but i feel i should give all details.

Mick

[Skyrine-Dave]

buy a Q45 AFM ?

[Bl4cK32]

I had similar issues with my afm maxing out when it went for its first tune. (rb25/30)

The pod filter i had had some wierd adaptor (smaller than the 80mm inlet to the afm.) I replaced it with a 90mm Q45 afm (as Dave said above ) and new adaptor, and all is fine now.

id be more worried of the injectors running out of sqirt too as i found out (had to replace with 550's and a 044 pump).

removing the screens off the afm is bad too, as it can result in an unstable idle most times (Q45 afm only has mesh on the front from factory)

[Cubes]

My stock ecu was pulling ignition timing and dumping fuel in well before the 5v mark.

It was also running very lean over 6psi. So be very carefull, get it on the dyno and check it out.

Over 6-7psi @ WOT my ecu was cutting fuel around 3000rpm.

I have since learnt the AFM was not maxed out and the injectors were not maxed out either. Just before the cut afr's were 14:1. Very dangerous.

I am not 100% sure why it was fuel cutting. I assume the ecu was freaking out as the airflow was too high for the rpm.

Mine on 11psi was hitting around 4.98v. (PowerFC)

The Z32 now reads 4v.

This was on the RB20DET ecu so no doubt the R33 ECU will allow a little more head room. Still be very carefull.

To max the stock AFM out you generally make up around 220rwkw.

If its the stock small turbo I doubt you will be making 220rwkw.

The AFM voltage is not linear. Even though you are hitting 4.7v you may still have quite a bit left in it. Well enough that your turbo won't max it out.

[RB30-POWER]

Whats a Z32 90mm?, So its up to 4V and your pushing stuff all boost through it as well, maybe i should get a bigger one again?

With a Q45 meter its 100mm?, will i lose resolution down low in the maps that will effect drivability.

Surely I don't need that unless im making massive power?

Im just suprised to see such high voltage with stuff all boost, maybe another 5psi or so won't push it over the 5.1V mark, as you say they aren't really a full linear scale.

Its deffinately not near 200rwkw, i would estimate maybe 150rwkw.

On another note, how do i tell if the VCT is working, i cant see/feel any difference with it on or off. Also if i supply 12V to the solonoid on idle, the sound/idle doesn't change in anyway what so ever?

Shouldn't i be seeing something with the extra 10deg advance on the inlet cam, or will 10deg be neglible on the 3L.

I mean honestly they are tractor motors, they haul arse with timing or without, the capacity is great.

I will measure injector duty cycle as well, just to see whats going on.

Why is it my VLT can make over 200rwkw on the stock 250cc injectors while the 340-370cc on the 25 can only make similar power, is it something to do with the suqential/batch mode injection difference, with how the ecu actually use the injectors.

I mean i dont really want to upgrade the factory injectors just to make a little over 200 at the treads, i know 250cc can do it on a rb30et. And they say the twin cam is more efficient, I wonder, more fuel and less power, but maybe i missed something.

[Bl4cK32]

Whats a Z32 90mm?, So its up to 4V and your pushing stuff all boost through it as well, maybe i should get a bigger one again?

With a Q45 meter its 100mm?, will i lose resolution down low in the maps that will effect drivability.

Surely I don't need that unless im making massive power?

.

The z32 measures the same size (80mm) as the rb20 and 25 afm, its the resloution that changes. However the Q45 afm is 90mm id, and has no mesh on the rear side.

Ive only got 0.8 bar max running with the rb20det turbo (due to restrictive muffler) on a shitty tune, so its making sfa power atm and its running the q45 afm.

There were slight idle issues, but the tuner has done a damn good job and all is well till it gets tuned properly.

[Sydneykid]

Some interesting stuff in this thread....

Let's start with injectors sizes, how many RPM does the RB30ET make 200 rkw? Bet it is lower than the rpm that the RB25DET makes 200 rwkw. Lower rpm means the injectors can be open longer for each stroke. So you get more power from the same size injector. I have seen over 400 bhp (230 rwkw) out of an RB31DET using 370 cc per minute injectors running at standard fuel pressure. I can get that out of an RB31DET because it does it at 5,000 rpm and the RB25DET needs 6,000 rpm. That's 20% "longer" for the injector to squirt.

A RB20/25 AFM is 80mm (that's OD), same as a Z32 AFM, while the Q45 is 90mm. The Z32 has resolution left at higher airflows because the hot wire is calibrated differently to the RB20/25 hot wire. The Q45 also has this higher hot wire calibration, plus the extra diameter slows the airflow. Removing the screens makes stuff all difference.

The standard mapping is very rich, as the airflow goes up, it just gets richer. Usually if it goes lean that means the fuel pump or the injectors are out of flow. You could use and SAFC or a DFA. If you want to know more, have a read of the Jaycar DFA and IEBC thread in the Stagea section. It explains most things.

That's enough for now, have an intercooler to clean:cheers:

[RB30-POWER]

Ok i understand about the injector time that more is needed at higher rpm if that where the maximum VE and power points occur.

I think i should do well over 200 at the wheels on the stock injectors as long as i leave the stock cams in the head, if i go bigger cams it will move the max VE and power points higher in the rev range requiring more injector "on time" with less time between cycles so to speak.

Now, does the 25ECU pull timing when it sees 5.1V (or is that complete fuel cut?) or does it see AFM voltage/load vs RPM being off the map and retards the timing.

Like if the standard map only has good timing values up to a certain AFM voltage/load point at each RPM point and if you add more boost/more air at the same rpm point it will go to a higher map point where the ECU has a lower timing value, because the factory ecu knows that a standard motor would never be at that higher value air flow at that rpm.

Or is the timing just 5.1V related?

Also SK, after looking at numerous dyno charts from other factory ecu engines, the ecu doesn't actually seem to dump more fuel in, it just pulls the timing. You may measure more richer on the O2 simply because of the retarted timing isn't allowing the motor to burn the fuel that goes in.

Also with regards to the AFM mesh thing, i've read and beleive from experience on other motors that it does effect the AFM readings and leans the mixtures from the extra air that gets passed without being measured from the lower restriction. I will test this myself and see what results i get.

I don't see how it can effect idle as on idle the static timing is set and the ecu uses closed loop mode and keeps the air fuel right. So it should be just as solid idle as with the mesh.

I'll ask more questions later

Regards

Mick

[Sydneykid]

Ok i understand about the injector time that more is needed at higher rpm if that where the maximum VE and power points occur.

I think i should do well over 200 at the wheels on the stock injectors as long as i leave the stock cams in the head, if i go bigger cams it will move the max VE and power points higher in the rev range requiring more injector "on time" with less time between cycles so to speak.

Now, does the 25ECU pull timing when it sees 5.1V (or is that complete fuel cut?) or does it see AFM voltage/load vs RPM being off the map and retards the timing.

Like if the standard map only has good timing values up to a certain AFM voltage/load point at each RPM point and if you add more boost/more air at the same rpm point it will go to a higher map point where the ECU has a lower timing value, because the factory ecu knows that a standard motor would never be at that higher value air flow at that rpm.

Or is the timing just 5.1V related?

Also SK, after looking at numerous dyno charts from other factory ecu engines, the ecu doesn't actually seem to dump more fuel in, it just pulls the timing. You may measure more richer on the O2 simply because of the retarted timing isn't allowing the motor to burn the fuel that goes in.

Also with regards to the AFM mesh thing, i've read and beleive from experience on other motors that it does effect the AFM readings and leans the mixtures from the extra air that gets passed without being measured from the lower restriction. I will test this myself and see what results i get.

I don't see how it can effect idle as on idle the static timing is set and the ecu uses closed loop mode and keeps the air fuel right. So it should be just as solid idle as with the mesh.

I'll ask more questions later

Regards

Mick

Hi Mick, some more suggestions;

I have tested removing the mesh on the flow bench, I have read the flows and the recorded voltages, IT MAKES STUFF ALL DIFFERENCE.

Idle problems mostly seem to come from exposed PODs, sucking hot air. I have recorded over 75 degree air going into a POD while idling in traffic. Add that to a little bit of oil off the filter element on the hot wire and its any wonder they idle at all.

Rish and retard, I have read the maps on the standard ECU. As the air flow increases and moves further and further outside the factory parameters, the ECU adds more and more fuel and retards the ignition in ever increasing amounts. It's not linear either, 10% too much airflow doesn't mean 10% more fuel and 1 degree ignition retard, it's more like 15% and 3 degrees. Then 20% more airflow doesn't equal 30% more fuel, more like 45% with 10 degrees retard. etc Eventually, when you get too far from the factory airflow, the standard ECU interupts the ignition to save the engine from whatever it is that is wrong.

Earlier Skyline ECU's didn't seem to do much comparision between parameters. Later on the ECU's get faster processors and more prgramming, so they start comparing stuff like throttle position, airflow, rpm, road speed and gear. When the parameters don't line up with each other, the ecu starts the usual rich and retard strategy. So they have moved up from "save the engine from whatever it is that is wrong" to "someone is playing with my sensors".

You see this in R33's where there is a dip (or flattening) in the power band as the engine gets onto boost and very quickly exceeds the factory levels of airflow. In Stagea S1's (hybrid R33/R34 ECU) it can by quite swoopy, rather than just a dip. R34's and Stagea S2's are even more sophisticated, they have 3 dimensional mapping.

Cams and VE, longer duration and higher lift camshafts would hopefully increase the VE. They may move it higher in the rpm range. But the VE itself may still be higher at the same rpm. So you will get more power at the same RPM. You can then lower the boost a little at the higher rpm so as not to exceed the airflow parameters. The higher VE will still give you more power even at the lower boost.

Bottom line, it's all in the tuning and taking the time to understand what is going on. Then tuning around it, but until you replace the ECU, it's an ever more complex set of compromises.

[Cubes]

RB-30 Power,

When you do decide to look at an ECU seriously consider the PowerFC.

I am damn impressed with how well it controls idle, cold starts, warm starts and the general smoothness. It actually feels smooth than the stock ecu.

[mr_rbman]

sorry to be a little off topic but why do some people call this conversion an RB31DET and others call it a RB30DET?

[Cubes]

Oversized pistons.

[RB30-POWER]

Thankyou for the response SK, appreciate your time to share some knowledge.

Cheers!

It sounds like what i already know, im going to be fighting an uphill battle with the stock ecu.

I have set myself a target of atleast 200rwkw with the stocker setup, which im sure it should do with some persaverance. Will just try to minimise the dips in the power curve as much as possible.

As for managment Cubes, I will be getting PowerFC without a doubt, I love the accuracy of AFM tunes, the PowerFC logic, and its plug and play ability, plus having a base map will help alot more again, if i have a go myself with the Wideband Lamda, but if i can acheive 200rw without the extra cost of the PowerFc, it will keep me out of trouble in the mean time.

While i built the motor, just to serve my own curiosity about the benefits of twin cam, if you asked me again would i do it, I would say no, for the money involved it could be invested into the SOHC and have way more bang for my buck. But hey, maybe once i get further down the track and have the major bolt on goodies it will offer benefits.

Ill get some injector duty cycle measurements up here soon, and also see how much extra boost until i trip the 5V mark.

Once im happy with it, i will throw it onto the dyno and just see what it is making at the treads.

[Sydneykid]

While i built the motor, just to serve my own curiosity about the benefits of twin cam, if you asked me again would i do it, I would say no, for the money involved it could be invested into the SOHC and have way more bang for my buck. But hey, maybe once i get further down the track and have the major bolt on goodies it will offer benefits..

My 20 cents;

The first time we did a RB30 DOHC 4 valve was almost 10 years ago, in a VL. The RB30ET was making a solid 305 rwhp using an old T04, and that was considered to be a lot of power back then. We used to wave the dyno sheet around the V8 boys just to peeee them off. It had some good stuff, a Motec (an old black one), a CDI, 6 Bosch coils, RX7S5T injectors, mandrel bent mild steel exhaust manifold, Wade cam, Cosworth pistons, Carrillo rods etc. We couldn't see a way to get more power out of it. We could have put a larger tubo on it and turned the boost up, but it was already as laggy as hell. Plus it had 2 defects for running Avgas on the steeet and there was no premium unleaded available then.

So we spent a lot of time learning what to do to make the DOHC cylinder head bolt up as not many people had done it. Then 5 of us did it in one day with the bottom end still in the car. Without changing anything else, on the same dyno, it picked up 25 rwhp at 2 psi lower boost, running unleaded. It had more power everywhere and it didn't ping when we slipped an extra 2 degrees of timing into it and made another 8 rwhp. A month or so later we did a solid camshaft conversion and picked up another 15 rwhp. To drive it was a revelation, it reved so easiiy, didn't knock it's head off on hot days and you could change gear without dropping off boost, wow.

Since that day I have never built another SOHC RB30:cheers:

[mr_rbman]

Oversized pistons.

thats what i thought!

[RB30-POWER]

Well i have come to the conclusion that the VCT is not working.

Im going to remove the restrictor and see if there is any change.

If not i will upgrade the diameter of the oil supply line as well.

Its difficult to tell if it works because the 3L has so much torque as it is.

Maybe im expecting to see to much from it, I mean its not VTEC after all.

I can't see/hear feel any difference off idle when it engages or when it disengages at 4500rpm, so i think it has a problem.

[Sydneykid]

Well i have come to the conclusion that the VCT is not working.

Im going to remove the restrictor and see if there is any change.

If not i will upgrade the diameter of the oil supply line as well.

Its difficult to tell if it works because the 3L has so much torque as it is.

Maybe im expecting to see to much from it, I mean its not VTEC after all.

I can't see/hear feel any difference off idle when it engages or when it disengages at 4500rpm, so i think it has a problem.

If I rmeber rightly the VVT is engaged at idle and up to around 1,500 rpm, then it is dissengaed until 4,500 rpm when it is engaged again. You need to test around 1,500 rpm not idle.

[RB30-POWER]

On another note, if i remove the factory O2 sensor to fit a Wide Band while i setup the jaycar interceptor.

Will this throw the ecu into any limp home modes, or will it just run open loop maps under light load instead of closed loop.

What i mean is it will not effect the high load open loop fuel maps, while i trim them up a bit with the interceptor?

It will save me welding an extra thread nut into the pipe, if i can jam it into the factory location just while tuning.

I don't think that tuning with the Wideband in the tailpipe after the Cat will give accurate figures will it?

[Sydneykid]

On another note, if i remove the factory O2 sensor to fit a Wide Band while i setup the jaycar interceptor.

Will this throw the ecu into any limp home modes, or will it just run open loop maps under light load instead of closed loop.

What i mean is it will not effect the high load open loop fuel maps, while i trim them up a bit with the interceptor?

It will save me welding an extra thread nut into the pipe, if i can jam it into the factory location just while tuning.

I don't think that tuning with the Wideband in the tailpipe after the Cat will give accurate figures will it?

You can replace the S&N lambda sensor with a F&W no problems. It makes it easier to tune as you get faster response. There is no problem with sticking it up the tailpipe though, it is THE most common position. You use one of these;