RB26 Speed Governor?

[Kip]

I put my Stagea 260RS on a dyno today (Results in the Stagea Forum). Not a bad result. It gives me a baseline. Getting some pulsing when it makes power. The guy running the dyno thinks it could be plugs, wastegates, or cats. Going to start with the easy one and change out the plugs.

Regardless, an interesting thing popped up on the two pulls. Speed topped out at 101 mph (163 kph). That seems low for the power it's producing. Is there a speed governor/limiter on this car? Did Nissan find some way to cap top speed on this car or engine?

-Kip

Edited March 7, 2024 by Kip
typo

[joshuaho96]

1 hour ago, Kip said:

I put my Stagea 260RS on a dyno today (Results in the Stagea Forum). Not a bad result. It gives me a baseline. Getting some pulsing when it makes power. The guy running the dyno thinks it could be plugs, wastegates, or cats. Going to start with the easy one and change out the plugs.

Regardless, an interesting thing popped up on the two pulls. Speed topped out at 101 mph (163 kph). That seems low for the power it's producing. Is there a speed governor/limiter on this car? Did Nissan find some way to cap top speed on this car or engine?

-Kip

Are you sure it’s not slipping on the rollers? All Japanese market cars have a 180 kph limiter from the factory. 

[GTSBoy]

^this.

The wonky dyno reading is wheel spin, fo' sho'.

[Dose Pipe Sutututu]

What gear was it run in?

Looks like the car may have been run in 3rd.

[Kip]

The shop owner ran it, so I don't know what gear he ran it in. That said, I've used this shop before to test a modified 911 that was supposed to put out 475 hp at the crank. He was able to confirm that.

Interesting thought on wheel spin. Given the time of year, I ran the pulls with my winter tires on the car (stock size, Blizzaks). I asked before we started if that would be a problem and I was told it wouldn't. There was a high pitched squeal when the car was at full tilt. Maybe that's what I was hearing.

-Kip

[Kip]

1 hour ago, joshuaho96 said:

Are you sure it’s not slipping on the rollers? All Japanese market cars have a 180 kph limiter from the factory. 

180 kph limiter? Thanks. I didn't know that. 180kph would be about where it topped out (topped at 162 kph). How does one get around the limiter? Some sort of EFI or is there a mechanical solution?

-Kip

[GTSBoy]

24 minutes ago, Kip said:

180kph would be about where it topped out (topped at 162 kph).

That's either a severe speed error in whatever was saying 162, or not the speed limiter causing it.

The ECU gets its speed signal from the speedo in the car. Unless someone has changed the ECU's speed limiter setting (downward, which is possible, but stupid and very unlikely) there is no way that there is going to be a ~18 km/h gap between what the speedo says and what the ECU thinks the speed is. Well, maybe there is one way. The speedo can get full of grease if the seal at the gearbox speed sender leaks and allows grease to flow up the cable drive. But....you almost certainly do not have a cable drive on a car of this vintage, so forget about that possibility.

The "fact" that it did the full pull up to ~160 was the reason Dose asked if it was done in 3rd gear. 4th gear will not run out of revs until much higher speed than that. The dyno run went to over 7500 rpm, which would be >180km/h in 4th.

[Kip]

I'll ping the shop. See if they recall. It was only a couple hours ago, so the odds should be pretty good. If not, they took video of the runs for their website (Stagea's are rare in the States). If it's not edited too much, maybe it will give some indication of the gear they used.

-Kip

[TurboTapin]

Was the speed taken on the dyno or your cluster? As I also have to deal with seasonal tire changes, I'm presuming you have smaller winter tires like most? If so, it causes a difference between cluster and actual road speed.

Cluster was at 180kmh limit but you were reading 163kmh on the dyno. 

 

Edited March 8, 2024 by TurboTapin

[joshuaho96]

23 hours ago, Kip said:

180 kph limiter? Thanks. I didn't know that. 180kph would be about where it topped out (topped at 162 kph). How does one get around the limiter? Some sort of EFI or is there a mechanical solution?

-Kip

If it is the ECU speed limiter you can chip the ECU to get rid of it. 

[r32-25t]

10 minutes ago, joshuaho96 said:

If it is the ECU speed limiter you can chip the ECU to get rid of it. 

No you can’t, only on a 32 

aftermarket ecu is the solution 

[Kip]

6 hours ago, TurboTapin said:

Was the speed taken on the dyno or your cluster? As I also have to deal with seasonal tire changes, I'm presuming you have smaller winter tires like most? If so, it causes a difference between cluster and actual road speed.

Cluster was at 180kmh limit but you were reading 163kmh on the dyno. 

 

I'm quoting the speed from the dyno. It's what's printed on the readout.

My winter tires are 245/45r17. Stock size is 255/50r17. An online calculator tells me my tires are 5mm shorter than stock and requires 3 more revolutions per KM. I think your point is valid. The same calculator confirms that it introduces some error to the speedo. When my speedo reads 150kph, I'm actually doing 148.9kph. It doesn't make up the whole difference, but accounts for some of it.

Speedometers can be impacted by so many different tire variables: amount of wear, tire pressure, size, etc. On most every car/van/truck I've owned, I have found that speedos read 2-3 mph (4.4 - 6.6 kph) higher than actual speed. Now knowing that the speed limiter is reading off the cluster, I have no doubt the clusters inaccuracy comes into play here. To @GTSBoy's point, It doesn't account for all of the "missing" 18 kph.

[joshuaho96]

2 hours ago, r32-25t said:

No you can’t, only on a 32 

aftermarket ecu is the solution 

There’s a bunch of Japanese ROM solutions around. It may be built into the MCU but the advantage of japan still living in the stone ages for this stuff is you absolutely can ask them to give you a ROM chip that is stock but with the limiter removed. 

[GTSBoy]

1 hour ago, Kip said:

Stock size is 255/50r17

Really? I find that very hard to believe. That is a simply massive tyre in terms of both width and sidewall height for a stock Nissan. Typically on a 17, Nissan were using 235/45.

I must ask, are you sure?

[joshuaho96]

5 minutes ago, GTSBoy said:

Really? I find that very hard to believe. That is a simply massive tyre in terms of both width and sidewall height for a stock Nissan. Typically on a 17, Nissan were using 235/45.

I must ask, are you sure?

Factory wheel is a 17x7J supposedly so 225/50R17 is probably the actual tire size.

[r32-25t]

4 hours ago, joshuaho96 said:

There’s a bunch of Japanese ROM solutions around. It may be built into the MCU but the advantage of japan still living in the stone ages for this stuff is you absolutely can ask them to give you a ROM chip that is stock but with the limiter removed. 

The rom chips can only be done on 32 ECUs not on 33 or later which includes stagea  

[joshuaho96]

36 minutes ago, r32-25t said:

The rom chips can only be done on 32 ECUs not on 33 or later which includes stagea  

http://www.mines-wave.com/english/CATALOG/ECU/VX-ROM_NISSAN.htm#SKYLINE

Stagea 260RS says it can be done on a trade-in basis. I guess you're right in that there is no separate ROM chip and doing the rework will suck but sourcing the right Hitachi H8, programming the onboard flash storage, and soldering on a new one with the speed limit set to whatever you want it to be is entirely possible.

The only question in my mind is whether you can even still buy programmable H8s in the right formfactor/automotive grade/etc. A lot of the tuners in Japan absolutely still have all the hardware necessary to do the programming otherwise you wouldn't see companies like Nismo still hawking remapped stock ECUs with their engines. Techtom was the same thing. 

Only reason to bother with this is if you have no plans to change anything. Stock tune, stock car, etc. Otherwise I agree, skip all this nonsense and go straight to Elite 2500/G4X/KV8/etc. But from personal experience truly achieving 100% stock equivalency on a standalone ECU is very, very difficult and I don't think any tuner out there actually cares either.

[Kip]

16 hours ago, GTSBoy said:

Really? I find that very hard to believe. That is a simply massive tyre in terms of both width and sidewall height for a stock Nissan. Typically on a 17, Nissan were using 235/45.

I must ask, are you sure?

Sorry. Typo. It's a 225/50r17. @joshuaho96 called it right. My bad.

Edited March 9, 2024 by Kip
Additional content

[Kip]

11 hours ago, joshuaho96 said:

Only reason to bother with this is if you have no plans to change anything. Stock tune, stock car, etc. Otherwise I agree, skip all this nonsense and go straight to Elite 2500/G4X/KV8/etc. But from personal experience truly achieving 100% stock equivalency on a standalone ECU is very, very difficult and I don't think any tuner out there actually cares either.

Based on the dyno results, the car already has some modifications (~269 kw at the crank). I need to find out to what extent, but assume some sort of ECU adjustment has been made previously. I'll have to check that out too.

I will be changing out some of the exhaust (still running the cats, but blew out the fiberglass packing on the dyno), so I'm leaning towards a Haltech PnP approach. That's all dependent on what I find though.

[Dose Pipe Sutututu]

On 09/03/2024 at 4:06 PM, r32-25t said:

not on 33 or later which includes stagea  

Can be done, @Toshi does them (no idea if he's still around).

He was flashing R33 RB25DET ECUs back in the day.