Running Without A Boost Gauge...

[colourclassic]

Hey guys, I've just bought a TurboTech MBC as I'd like to erase the stock 2-stage solenoid in anticipation of a high-flow turbo and Nistune later down the track. For now I'll only be running 10psi through the stock turbo and R34 GT-T SMIC.

I've heard good things about the TurboTech controller holding and sustaining steady levels of boost, and have bought a VDO 25PSI mechanical boost gauge in order to set the correct level of boost. VDO are apparently pretty accurate and reliable gauges, and I obviously wouldn't trust the factory dash ornament with my engine's health.

My question is, once I have set the controller to my desired boost level, can I safely remove the VDO boost gauge and set it aside for tuning purposes, knowing the controller will safely hold my desired boost. I don't want to mount gauges in the cabin as it attracts unwanted attention and looks tacky. I guess the real question is, are MBC's generally 'set and forget' or over time will boost wander and stray from the original setting?

[Dose Pipe Sutututu]

usually set and forget, and the factory boost gauge isn't that bad.. it's pretty accurate..

also note if your car spikes over 0.7 bar the ECU will drop timing & dump in fuel so even if the MBC fails you still have some sort of fail safe

[colourclassic]

Yea I thought so. I hope once I get my turbo high-flowed it will be a similar story: set and forget. CBF with gauge-pollution cluttering my dash.

Cheers dude.

[Dose Pipe Sutututu]

no dramas

keep her under 0.7 bar, anymore and on a cold night you'll just hit a brick wall.

I don't have gauges either, only got a wideband in the cabin.

[colourclassic]

Yea I don't intend to run over .7 bar for now.

With a Nistune tune, are the R&R parameters increased to a higher value, allowing more airflow, or is R&R scrapped all together?

[Dose Pipe Sutututu]

you can set the TP Load Index Limit (known as R&R to most) to whatever you want

[GTSBoy]

Actually, R&R isn't a single number. The TP limit is the simple hard cut you get when the load is simply too high. R&R is effectively nothing more than ridiculously rich and ridiculously retarded values in the top right corners of the fuel and timing tables. The fuelling numbers are well over 100% duty cycle (stock injectors of course) for example.

[Blackkers]

Sounds like you've got a good plan but I just want to add something about the TurboTech MBC.

I used one on a turbo honda prelude about 2 years ago and I had trouble with consistency, even running external gate low boost (10psi). The adjuster bolt can be locked using the supplied lock-nut however it would come loose after 10 or so days and it was the gauge that told me. I tried tightening it however it was cheaply made and broke in my hands.

Having said that, the ball & spring type MBC's are generally well liked as they provide the best response compared to simple bleed valves. I wouldn't buy a TT MBC again.

just my 2c, good luck with it

edit: Just also want to say that running a modified turbocharged car you probably should have some sort of boost monitoring equipment in the cabin. If you don't like gauges there are digital options too

Edited December 23, 2013 by Blackkers

[Missileman]

Actually, R&R isn't a single number. The TP limit is the simple hard cut you get when the load is simply too high. R&R is effectively nothing more than ridiculously rich and ridiculously retarded values in the top right corners of the fuel and timing tables. The fuelling numbers are well over 100% duty cycle (stock injectors of course) for example.

I'm having a little trouble running into the knock maps at the moment, only slight knock detected by the sensors but no knock I can hear with my knock ears?

I've backed off the timing and fuel maps to stock, whilst keeping the boost up to 13-14 psi on the stock rb20 turbo. Are these the two tables I need to adjust? and any tips on how to approach it?

[Dose Pipe Sutututu]

the 2nd table is the TP limit I was referring to, i.e. when you exceed an amount of boost it cuts (feels like you've hit a brick wall).. as for the first table you've opened I don't recall ever seeing it/using it.

In terms of the knock table, I don't believe there's a sensitivity table to adjust when it falls into the knock table. I believe Matt from Nistune was still working on that (last time I read somewhere)

[colourclassic]

I think one way to combat the adjuster being close to maxed out (ie screwed nearly all the way out) would be removing any line restrictions in the signal pipe. This would allow a higher pressure to reach the boost controller and necessitating a few more turns of the adjusting screw clockwise to achieve the same wastegate pressure. Ill sus that out when I receive it though.

Cheers on the explanation of the ECU's R&R/TP load index, helpful to know.

[V28VX37]

Sounds like you've got a good plan but I just want to add something about the TurboTech MBC.

I used one on a turbo honda prelude about 2 years ago and I had trouble with consistency, even running external gate low boost (10psi). The adjuster bolt can be locked using the supplied lock-nut however it would come loose after 10 or so days and it was the gauge that told me. I tried tightening it however it was cheaply made and broke in my hands.

Having said that, the ball & spring type MBC's are generally well liked as they provide the best response compared to simple bleed valves. I wouldn't buy a TT MBC again.

just my 2c, good luck with it

edit: Just also want to say that running a modified turbocharged car you probably should have some sort of boost monitoring equipment in the cabin. If you don't like gauges there are digital options too

Interesting. I am running TurboTech V2 MBC and originally bought it as several articles suggested that the ball & spring design is better than a bleed valve. However, both times the car has been tuned (originally 199rwkw @ ~11psi, now 257 @ ~17psi) my tuner has commented that they had some trouble tuning with it, and recommended a basic TurboSmart one instead if I want to stay with a MBC. Perhaps I should go electronic...

More on topic, I have never had a boost gauge as my GTT came with the navi unit instead of the triple gauge cluster. It would be good to have a reading but I don't want a big gauge either - can anyone recommend an accurate but affordable digital one?

[GTSBoy]

When I tuned my RB20 I made the knock maps the same as the main maps and just took 1-2 degrees and added a tiny bit of fuel in the areas most likely to knock....just for a little paranoid safety. I did this because the RB20 knock sensors seem to like detecting knock even when no-one else can hear it. Either that or they hear nothing when it's pinging its tits off. Either way, at least half of them are useless.

As to the TTP max and TP limit tables, just a correction. TP limit is the "boost" cut. That is the table that will cut the ECU when AFM calculated load exceeds the max in the table. If you're tuning a modified engine simply raise it to 255 all over and forget about it. If you want to keep it, raise it to the highest TP values you ever see at any rpm + 15% or so.

The TTPmax values are the maximum actual injector pulswidth allowable at any give rpm. This table places a limit on how much fuel you can inject because sometimes you get a few different tables and other scalars all contributing to enrichment and if they all had their way you'd inject too much juice. So if they sum to more than the TTPmax, then the result gets clipped at TTPmax. TTPmax and TTPmin may need to be changed if you change AFM/injectors because they don't necessarily scale properly. TP limit needs to be changed if you do AFM/injectors also but it scales properly and so Nistune (can) do it for you.

RB20 R&R is actually different to what I said in my first post. My first post was relatively RB25 specific. Thje RB25 scheme seems to have been intended to prevent anyone ever actually approaching the point where the engine might get hurt, by dumping in huge amounts of fuel and no timing in the main maps once you get past the stock boosted region. The scheme in the RB20s seemed to be much less a built in R&R in the maps, much more sensible fuel and timing munber in the main maps, followed by more conservative values in the knock maps. If you manage to get it to ping, it'll change maps. If it still pings then the RB20 ECU seems to be able to pull a further amount of timing out. I assume the RB25 ECU is able to do the same, but no-one ever really gets there.

[Missileman]

Thanks gtsboy,

So what I have got to answer is why its changing to the knock maps, and it seems by your answer the only thing that will do it is the knock sensors. I was hoping that it may have been the TP load limit not coping with the extra boost.

If the sensors do flip it over to the knock maps, shouldn't this register as a #34 fault code? I've checked after a run and I just get the same 55 all clear?

It was only when I changed the knock timing to 5 deg and recorded a run in tuner mode that it became obvious it was swapping maps, yet in stream mode nistune would never light up the knock maps to indicate which map it was reading, it would only ever have the main maps shaded green. I'll have to get on to Matt about that.

Cheers Mike.

[GTSBoy]

I had a similar thing going on, although that was a few years (and therefore a few versions of Nistune) ago. We saw my (RB20) ECU switch over to knock maps whilst dyno tuning, even though we couldn't hear any knock and the tune was near stock (and mixtures were fine). That's why I ended up doing what I did with the knock maps. But on another version of Nistune at some other time I couldn't see it changing under the same circumstances.

I've never seen knock maps activated raise a DTC flag. Doesn't mean it doesn't happen, but I haven't seen it.

[Missileman]

Yeah it might only flag the 34 code if the sensor is off line.

[Rolls]

Yea I don't intend to run over .7 bar for now.

With a Nistune tune, are the R&R parameters increased to a higher value, allowing more airflow, or is R&R scrapped all together?

R&R isn't really a thing as much as a zone in the tune, there is a max airflow limit which will cut the engine out but R&R is just the upper end of the revs at high load, eg it is very rich and retarded, a retune will fix this as they will put appropriate values in those cells.

[Rolls]

I use an eboost street boost controller which has a digital guage but I hide it in the car, so I can look at it if tuning or troubleshoot but no point having a big tacky LOOK MR POLICEMAN gauge in your car imo.

I'm having a little trouble running into the knock maps at the moment, only slight knock detected by the sensors but no knock I can hear with my knock ears?

I've backed off the timing and fuel maps to stock, whilst keeping the boost up to 13-14 psi on the stock rb20 turbo. Are these the two tables I need to adjust? and any tips on how to approach it?

Ignore the knock maps, they aren't reliable enough to be trusted, nissan only detect knock at low rpm as well, at high rpm there is too much mechanical noise so they are ignored. Sometimes they will pick up knock that isn't real knock and sometimes they will miss real knock. You could put -2 degrees in the entire map and copy it to the knock maps, at least you will know when they are being used.

the 2nd table is the TP limit I was referring to, i.e. when you exceed an amount of boost it cuts (feels like you've hit a brick wall).. as for the first table you've opened I don't recall ever seeing it/using it.

In terms of the knock table, I don't believe there's a sensitivity table to adjust when it falls into the knock table. I believe Matt from Nistune was still working on that (last time I read somewhere)

I would personally use the TPLimit and not nuke it completely, add 10% to the max you ever see in top gear, that way if you blow your boost control line off and run infinite boost you are less likely to pop the motor.

Edited December 26, 2013 by Rolls