RB25DET queries

[WalkyHR31]

Guys, a couple of things please

1. TPS voltage has been at 0.36v for years (have ECU Talk readout) as could not get at it to adjust it and tuner said not a problem. Engine runs fine but now have front of engine apart and have reset to 0.44v closed and it reads 3.76v fully open. Is this about right? What is consequence of either low or high voltage when closed?
2. Took opportunity to install adj ex cam gear. What is the go here? Currently run a TD06-25G, which is a bit laggy but once on full boost (20 psi) around 4000 RPM really gets going and holds boost through to 7800! Am led to understand retarding cam gives better turbo response as I would like it to come on a bit earlier. Is this correct? If so, approx how many degrees?

Thanks

[Dose Pipe Sutututu]

You should have left it as is! Your tuner would have already calibrated the voltage range in your ECU.

If you play around with it your ECU won't know what a WOT and idle condition is anymore. Since you've played with it, you will need to recalibrate your TPS in your ECU (I recall you're using a Haltech) - not a hard task, but you've essentially just undone his/her work.

Try ret4rd it by 3~5 degrees however you'll need to take some timing out in your peak load area - best to be done on a dyno to load hold and knock detection.

[WalkyHR31]

On 28/04/2022 at 4:57 PM, Dose Pipe Sutututu said:

You should have left it as is! Your tuner would have already calibrated the voltage range in your ECU.

If you play around with it your ECU won't know what a WOT and idle condition is anymore. Since you've played with it, you will need to recalibrate your TPS in your ECU (I recall you're using a Haltech) - not a hard task, but you've essentially just undone his/her work.

Try ret4rd it by 3~5 degrees however you'll need to take some timing out in your peak load area - best to be done on a dyno to load hold and knock detection.

OK thank you. WOT? I'll give it a try and can always reset back to original voltage. I think the voltage has changed as bit since it was tuned 8 years ago so that's why I reset it. Its a Z32 ECU with Nistune board. Yes understand re the adj cam gear and that I will need to check timing after adjusting. Mate David Zilm has a private Dyno Dynamics I can use.

[Dose Pipe Sutututu]

WOT is wide open throttle, Nistune allows you to adjust the minimum voltage before the idle strategy is enabled.

Easier to leave it how it was before as the TPS calibration in Nistune isn't as straight forward as a modern ECU.

[WalkyHR31]

OK thanks for all that info, however, what you are saying is that the voltage is not that important at tuning but I constantly see posts here saying TPS voltage should be between 0.45 and 0.5 v. 

Re the ex cam gear are you saying that 3-5 degrees boofhead will improve turbo response, which I assume means boost will come on at lower RPM. Any idea by how much lower? I guess one tooth is about 8 degrees hence the need for a vernier gear.

[Dose Pipe Sutututu]

On 29/04/2022 at 11:53 AM, WalkyHR31 said:

I constantly see posts here saying TPS voltage should be between 0.45 and 0.5 v. 

Yes, if you're using a PowerFC door stopper or a stock ECU  

If you're using a configurable one, you can set whatever voltage is the floor for the the ECU to you know you're at 0% throttle to enable the idle strategy and/or decel fuel cut.

Really hard to say, best way is to incrementally ret4rd it on the dyno and graph the differences between runs.

[WalkyHR31]

OK thanks that all makes sense and I now understand the difference. Will reset voltage back to original value.

Again makes sense so i'll try that on the dyno. Assume as cam is retarded CAS needs to be advanced the same amount to maintain correct static timing?

[Dose Pipe Sutututu]

Theoretically you shouldn't move it, because if you do your TDC will be offset.

By ret4rding the cam gear, you're just ret4rding the exhaust cam and it's unfortunate the CAS is running off the exhaust cam.

If you resync it, then your entire timing map will be off.

 

Those are my thoughts, happy to be corrected by someone at least 3x smarter than me @GTSBoy lolol

[BK]

Cam timing is not ignition timing - completely different things.

Regardless of where adjustable cam gears are set you still set up the crank angle sensor as normal with a timing light to get correct engine position against the crank - It's the whole point of adjustable cam gears so the outside cam gear teeth don't move from the factory position relative to the crank to change cam lobe location.

Ignition timing is relative to where the crank and therefore pistons are (engine position), not relative to cam lobe positioning.

[Dose Pipe Sutututu]

I think I need a diagram to visualise this lol

[GTSBoy]

On 4/29/2022 at 10:37 AM, WalkyHR31 said:

Assume as cam is retarded CAS needs to be advanced the same amount to maintain correct static timing?

I think this, because

(actually, not because of this)

On 4/29/2022 at 11:02 AM, Dose Pipe Sutututu said:

Theoretically you shouldn't move it, because if you do your TDC will be offset.

because that's not true. He's adjusting the cam gear, not the crank gear.

But also I disagree with Ben, because

On 4/29/2022 at 11:38 AM, BK said:

Regardless of where adjustable cam gears are set you still set up the crank angle sensor as normal with a timing light to get correct engine position against the crank - It's the whole point of adjustable cam gears so the outside cam gear teeth don't move from the factory position relative to the crank to change cam lobe location.

This is not true. The CAS is driven off the centre of the end of the camshaft. Therefore the CAS is in time with the camshaft. The gear remains in fixed relationship with the crank, but the adjustable bit of the gear moves the cam foreward/backward wrt the gear, and the CAS goes with it. So, advance or boofhead the cam by 2° and you have to boofhead or advance the CAS to compensate.

Whatever the case, you don't just twist it back..... you do use a timing light to get it set right, in which I do agree with Ben.

There. I hope I haven't ruffled too many feathers.

[Dose Pipe Sutututu]

@GTSBoy always good to get your technical perspective, hence the tag  

 

[BK]

On 29/04/2022 at 3:09 PM, GTSBoy said:

I think this, because

(actually, not because of this)

because that's not true. He's adjusting the cam gear, not the crank gear.

But also I disagree with Ben, because

This is not true. The CAS is driven off the centre of the end of the camshaft. Therefore the CAS is in time with the camshaft. The gear remains in fixed relationship with the crank, but the adjustable bit of the gear moves the cam foreward/backward wrt the gear, and the CAS goes with it. So, advance or boofhead the cam by 2° and you have to boofhead or advance the CAS to compensate.

Whatever the case, you don't just twist it back..... you do use a timing light to get it set right, in which I do agree with Ben.

There. I hope I haven't ruffled too many feathers.

Maybe I didn't explain it in detail enough to be clear as yes the CAS is off the camshaft, but the point of it is to reference the CRANKSHAFT, not camshaft position. CAS = CRANK (not cam) angle sensor. Yes if you adjust the the inside of a cam gear the CAS will end up in a slightly different position, but the different position is referenced relative to the crankshaft for engine position.

At the end of the day we do actually mean the same thing 👍, as the ignition timing is in reference to the crankshaft, not the cam position

[Dose Pipe Sutututu]

There we go, I was wrong  

Happy to admit it too, unlike Facebook - where most will argue they're right even if they're wrong!

[BK]

On 29/04/2022 at 4:22 PM, Dose Pipe Sutututu said:

There we go, I was wrong  

Happy to admit it too, unlike Facebook - where most will argue they're right even if they're wrong!

As long as everyone's on the same page about what's going on, that's all that really matters 👍

[WalkyHR31]

Thanks Guys, appreciate the input and understand what I need to do. If I boofhead will reset timing with timing light.

[Duncan]

I can't take it any more. Autoreplace for retard has been removed. No idea why it was ever there.

[The Bogan]

Test

Turkey

Nope auto correct seems dead

[Duncan]

sorry mate. fixed that a while back. there is still a list though

[soviet_merlin]

On 30/04/2022 at 12:43 PM, Duncan said:

I can't take it any more. Autoreplace for retard has been removed. No idea why it was ever there.

Oooh man! It took me way too long to work out what you were talking about. I had never heard of the term boofhead before reading this thread. I just went along with it and assumed it was a special way of adjusting things. Because people used it so confidently and GTSBoy is always so educated on everything.

It would have been pretty funny if I ended up asking my mechanic about boofhead timing adjustments