n00b NVRAM tuning a Rover V8

[antus]

Check your basic configuration is ok, look at the data list view, make sure after its started its saying the right number of cylinders. Check all your sensors, so with ignition on but engine not running check you see close to 100kpa on the MAP sensor, check you see the throttle move when you press the throttle. Check intake air temp and water temp are believable. If its cold both should be close to ambient temperature in the room. If you've put some heat in to the engine the coolant temp will be higher.

look at stage 1 and stage 2 cranking tables, they are injector opening time in miliseconds, so the injection at cranking doesnt change when you change the injector rate. Compare the rate of the injectors you have and the factory injectors for the tune you started with, and change those tables by the same percentage difference. For example if factory flow is 19lb/s and new one is 38lb/s thats twice the flow, so multiply those tables by 200%, which is 2.00. You can select all the cells in the table and use the multiply tool with 2 to get this. But use a multiplier to suit your use case.

Then probably tweak the injflow rate by small steps to get the fueling close enough it starts and idles. check your timing with a timing light. Ground the diag mode pin to get a static 10 degrees timing, and then verify you are getting 10 degrees with a timing light. Then let it warm up and start tuning your VE table. Don't change anything else unless you have a good reason to. You should be able to get it running ok with just those things. Sanity check the spark map does not look too advanced for your engine also. Listen for ping when you start moving it under its own power until you are comfortable that the timing map is OK for that engine.

[spoon]

Thanks antus! Very helpful tips! I have checked a few of these points previously but will go over them again to ensure I didn’t miss anything. The stage 1 and 2 tables - what are the difference between them? I’m sure this is where I will see the most gains so look forward to checking them out.

Thanks again!

[antus]

I think its 0-200 rpm, and 200-400 rpm, then it uses normal fueling above that, also with cold start enrichments applied. The stock shape of the tables is fine, just you need to account for injector size changes as described. It also doesn't need to be perfectly accurate to get the engine up to normal running speed, but typically when changing injector rate people often change by over 100% of flow and those kinds of difference are more of a problem.

[spoon]

I had a fiddle today, after a few setbacks I did a clean install of the bin back to ose$12, reinstalled the nvram and made only a few changes to the fuel flow scalar (back to 0.0399) and ensured the fan switched on to keep temps ok while I idled.

I adjusted the cranking tables by the same amount (divided tables by approx 3) and now seem to be a little closer to where I need to be now.

Startup still requires a constant cracked throttle until warm and idle is pretty rough but stays running after that.

I have tried adjust the injector rate in small increments but wide band values seem to jump around a lot. I managed to get it to keep close to around 12:1 for a while, but then it shifts to lean after a few minutes with no other changes to the tune.

I’m going to get some more petrol in the car in case old fuel is causing some of the issues before I make more changes.

On a side note, I tried adjusting the VE table for closed throttle at idle, but this didn’t seem to make any impact on the engine running (performed in real time with bubble tracing) - is this expected? Just seeming to not get the feedback from the changes that I would expect at this stage! This is just at idle with closed throttle. Don’t really want to drive the car until I’m sure I know what I’m doing!

Thanks again!

[antus]

Good news. The going lean sounds like cold start enrichment timing out and you go back to normal fueling. So next you probably want to dial in the injector rate with it warm, and assuming you turn up the flow, then turn down the cold enrichment a bit until its happyer cold.
Note that idle can be the hardest part of the tune to get right, because delivering small amounts of fuel tends to be the least accurate part of the injection. You can turn on bubble tracing and see which cells its sitting between at idle and adjust them all together to try and get it right, otherwise it can drift between multiple cells and make wild changes to the fueling. Once you have the region right, and then the regions next to them, you can smooth out the difference between them. Also note that quality injectors will idle better because of more constant flow, and you need to get the injector opening times right to get this part of the map stable too. In general, you just need this area good enough, then you can move on to the rest of the map, then come back to it when you have more confidence in what you're doing and the rest of the VE table.

[spoon]

So i had another go today, i seem to have solved the issue with the wideband jumping around too much, by installing a noise suppressor to the wideband supply power as it is powered off the fuel pump relay (to prevent the wideband heating when engine isnt running). The signal is a lot more stable now. This seems to have a follow on effect of making the engine run a bit smoother - i assume the tune was/is correcting itself based on the (erratic) wideband data?

On that note, im going to recalibrate the wideband to be sure its reading correctly, as the engine seems to run better when afrs are showing around 10:1 at idle which doesnt seem right.

will see what data i come back with once ive done the recal.
thanks again for your help, im slowly getting there

[antus]

You'll find timing has a lot to do with it too. You absolutely need to make sure you're wideband is reading accurate. I prefer the ones with a physical gauge, because then you can check that what you are seeing in tunerpro matches. You might need to set Wideband 0v AFR and Wideband 5v AFR scalars to suit your equipment.

By default it doesn't use wideband for fueling, its just for diagnostic data for the calibrator. I think its 12p? not sure, but does have an option to tune from wideband, but in practice we've found its not accurate/fast enough and tends to make things worse rather than better, so is not recommended to use that feature. Just use the data from the wideband to make sain and reasonably smooth corrections yourself.

[brindo]

Were you intending to fit an IAC at some stage? Would save you a fair bit of grief if you can. Should be able to set a start position and it will do the rest.

Cool project. Keen to see some more photos.

[spoon]

So this is what i am planning to rectify now - i didnt initially set it up as the Rover IAC Valve is on the back of the Plenum which interferes with a cowling, whereas the GM IAC valves arent remote mountable...
To address this, i cut up an old VS throttle body to remove the IAC plumbing and IAC Valve, in this way I can tap in some airline fittings and plumb up to a separate vacuum port on the plenum via some tubing.
I have almost finished this now, and actually turned out a lot neater than i was expecting (will post some pics soon).
I expect this will solve my warmup issues at the very least!

[spoon]

Pic of modified IAC fitting and engine bay pic.

Just need the air line fittings and some hose now to plumb up then reconnect the iac sensor wires