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DIY Fuel injection thread.


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Just now, Roman said:

No IACV sucks a bit, but you can work around it by pulling ignition timing out of your hot idle so the rpm drops. Then adjusting the throttle stop so you reach your hot idle rpm goal with more air. So now you can have the extra air you need for cold start with more ign timing.

That 6ms value is incredibly arbitrary it just rescales your whole map up or down. So it doesnt have to be an exact value, its just so you get good resolution of the numbers in the table.

6 or 6.7 isnt going to be a big deal

 

Thats an awesome idea... if my hot timing is ~12deg, knock this back to 8-10 might be enough?  Asuming I keep the relevent cells out of this a bit higher shouldnt cause any off idle accel issues?

Yes, know REQ_Fuel is just a scaler, just cautious since this early megasquirt version swaps between raw and % tables (compared to later models) that I dont mess certain parts up. 

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Yeah something like that, youll just need to see how far you can drop it with just timing. 

Might be sensitive to it or might not. Can maybe rich or lean it out to drop the idle a bit too. A lean mix needs more ign advance as it burns slower. So you might be able to exaggerate the effect by running a little lean too.

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Map looks horrible.  I would suggest disconnecting  the shaft between the engine and jet unit if possible.  So you can run the engine while out of water. Tune as much of map as possible  free revving it and getting all the idle stuff right  .  Then yeah from that guess the rest of the tune. A stock engine without cams will have a fairly smooth map with highest numbers being at max torque.    Once in the water, as you say will only be able to tune certain part of the map, the way the jet unit loads the motor.  I would  do   part throttle runs. Once get that right . Repeat at higher throttle.  Right up to full throttle.   Then  use trend from the points you tuned to guess rest of map.  Need to sort the main tune before bothering with any of the compensation 

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Buy differential, make super long driveshaft, strap down, dyno tune, profit? 

EDIT BELOW... to add something possibly useful or not. 

You will have to make a bit of a compromise on the idle I reckon, probably to the point where it'll need maybe 30 seconds or more of no load idle / warmup before being able to be happy.  I reckon the cold start fuel decay is more about air density change with manifold heat soak and wetting of the head / manifold on start than genuine running of the engine vs coolant and block temp. 

My 1ggte KP runs nothing in the way of an iacv, (or tps for that matter) and for a track machine built nearly 20 years ago it is a reasonable setup, with decent idle stability once its been running for a minute. Sure this you wouldn't put up with for a road car though. 

 

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12 hours ago, BlownCorona said:

thats pretty cool! 

are they reliable and can you still buy them? super interested in acquiring one, over the planned diy knock ears. 

Heard a few good things, and Andre has mentioned them on HP academy before. Its just a guage will  hook it up and report back once the cars going

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I know I've banged on about this same topic for a zillion years, but noticed something interesting with cam timing. 

At peak cylinder filling RPM, which in my case is approx 6500rpm. It almost doesnt matter what the cam timing is, it stuffs heaps of air into the motor in any case. Then at a lower rpm than this, advancing the cam helps increase cylinder fill, and after this retarding the cam helps increase cylinder fill. So that's nothing too out of the ordinary.

But I've always also had this big hole at approx 3000rpm area. It's the same but opposite situation.
This is the only other place where adjusting the cam timing makes the least amount of difference.
But here you get the worst cylinder fill... And it happens at what seems like half the RPM of the area where you get peak cylinder fill with minimal cam timing effect.
So out of interest, if I divide the RPM scale by 3250 its interesting to note that "1" is at roughly worst cylinder fill, and "2" is at peak cylinder fill.
I wonder if this is actually beneficial from a fuel economy point of view, in that you get a natural dethrottling situation happening right at the RPM where you cruise on the motorway. Which might be why the regular dethrottling strategies have never seemed to make a difference to fuel economy on this motor. As it's already doing it.


graph.png.2659ee6b3d2d5ecc5c20efe40daac24b.png

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14 hours ago, kpr said:

Map looks horrible.  I would suggest disconnecting  the shaft between the engine and jet unit if possible.  So you can run the engine while out of water. Tune as much of map as possible  free revving it and getting all the idle stuff right  .  Then yeah from that guess the rest of the tune. A stock engine without cams will have a fairly smooth map with highest numbers being at max torque.    Once in the water, as you say will only be able to tune certain part of the map, the way the jet unit loads the motor.  I would  do   part throttle runs. Once get that right . Repeat at higher throttle.  Right up to full throttle.   Then  use trend from the points you tuned to guess rest of map.  Need to sort the main tune before bothering with any of the compensation 

Cheers, aligns with my strategy on this.

Some more googling and found what could be a better starting point that what I have.  Need to do some conversions as not all corrections in MS1 are % based.

https://www.clublexus.com/forums/build-threads/771816-rob-s-sc400-pnp-megasquirt-project.html

From the mods I had to do to the throttle, fully expecting the TPS isnt calibrated correctly and need to check the base timing (I see 4 Deg trim already)

Not sure I've I'll get to much testing on it this weekend, started trying to hunt down 1UZ log exhausts to rig up the O2.

Aim it to get at least 'running right' prior to spring.  I need to pull the engine at some point (probably next year) and will likely go through and re-wire alot of the connectors, built a proper fuse and relay bank, perhaps upgrade to a microsquirt and mount in a different location.  Who know what the years of heat/vibration has done on this MS1 and its expected reliability....

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there is a pretty good base map in the link software,  one we used would have been in the older g3 or g4 pclink.      that  only needed a few tweaks to get right,  on a mates 1uz years ago.     maybe worth a look just to get the trend  of the fuel map.   plus some ideas for the ignition map.    compare to old mates one you found

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Just now, kpr said:

there is a pretty good base map in the link software,  one we used would have been in the older g3 or g4 pclink.      that  only needed a few tweaks to get right,  on a mates 1uz years ago.     maybe worth a look just to get the trend  of the fuel map.   plus some ideas for the ignition map.    compare to old mates one you found

More good ideas....

Some quick googling finds some partial screenshots which looks somewhat similar....

Another question I have... doing some more research, with the 'constant load' aspect of the jet unit, the map area at which you are at 'cruise' has a higher MAP value than in a vehicle.  Would it be ok in the AFR map to move the lean values into that area to correctly tune for those situations?

Need to do the logging to properly see what I need to do but something I was thinking of. 

image.png.6bc477103fd5e9112e976ddc08771166.pngSome quick googling to find a partial screen

 

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You still want to richen it up as load increases.   if stay lean with too much load will run into heat and knock issues.   will basically end up same as what you would use in a car.  its more what the motor wants than what its in.   will depend on the whole setup as to how much load is on engine at "boat cruise" .    from memory the supercharged mang machine i tuned, once got up on the plane and backed off wasn't a silly amount of load on engine.  so the afr could be fairly lean at that point  

the link map i was thinking of must be in the g3 software.  g4 has vvti  version.   dont have it installed on this pc at the moment

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On 19/06/2020 at 11:39, kpr said:

You still want to richen it up as load increases.   if stay lean with too much load will run into heat and knock issues.   will basically end up same as what you would use in a car.  its more what the motor wants than what its in.   will depend on the whole setup as to how much load is on engine at "boat cruise" .    from memory the supercharged mang machine i tuned, once got up on the plane and backed off wasn't a silly amount of load on engine.  so the afr could be fairly lean at that point  

the link map i was thinking of must be in the g3 software.  g4 has vvti  version.   dont have it installed on this pc at the moment

Got it, makes sense.

Found the link base tune by doing a screen shot from a video by 'CarTuneNZ' - great source for anything 1UZ.  Looks a pretty good starting point, I also transcribed some accel settings from a decent source.  Planning to get on the water this weekend.  Will report back...

image.png.577f366c1b96629e84992851ed8a51d2.png

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  • 3 weeks later...

Hey all keen to validate some thoughts

Had to drive a mates BF XR6T modded Falcon from impound back to his house the other day, has been tuned/reflashed (factory ecu) by a local guy and tbh it drives like a sack of shit

All the low rpm/load doesn't feel right to me

Anything under 3000rpm and low load it stumbled and struggled so from a 4L I was very surprised, drove it when he first got it and it drove a lot better, my old rb25det (r34) powered r32 drove better off boost, hell anything N/A ive driven drove better

I suspect all the low load/idle off boost area is tuned wrong as it drinks fuel, smells rich and is really doughy, really need to up the revs to get it off in 1st and more then what a heavy duty clutch would need in my mind

At low throttle load in 2nd under 2500/3000 rpm it really stumbled, had to drop it down to 1st a few times just to keep it going, cant run aircon as it just wants to die

At 100km putting it into 5th and 6th it just had nothing there to pull away from the lower rpm

80km had to be at 4th or 3rd to keep it going

Normally on a 6speed I would still be at 4th gear for 60km and I was having to sit on 3rd or 2nd to keep it going

I suspect the tuner has re-scaled the tune to suit on boost and load and not left enough resolution at lower RPM/lower load to maintain drivablity or not adjusted it at all to suit the new inter-cooler/piping/exhaust

Anyone have any ideas if I am on the right track? car makes 280kw

 

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If it drove like that straight after  it was "tuned",  yep sounds like the dude has done a shit job.      If was fine after the tune for awhile then started playing up, might be a bad sensor  or the likes rather than tune

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Some of those factory ECUs for the Barra motors use a really fucked up fuel model, it's really tricky to understand compared to a normal aftermarket ECUs logic. 

If someone hasnt tuned one before, or not many, it may very well run like a complete sack of shit for no good reason.
 

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Just now, kpr said:

If it drove like that straight after  it was "tuned",  yep sounds like the dude has done a shit job.      If was fine after the tune for awhile then started playing up, might be a bad sensor  or the likes rather than tune

Fair point, didn't drive it after it was tuned but mate had commented about having issues driving it slow, which based on how it drives atm doesn't surprise me. At the time I wrote it off as he has a heavy foot

Think he may have also changed intercooler/piping since he got it tuned now I think about it as well so that won't help either

Might need to look into getting a HP tuner licence and a cable so I can have a look at the maps/logs

Any guesses on what sensor it could be, I don't know Barras well enough to guess or know what commonly fails

Pretty sure they run a narrowband from factory so perhaps thats died and/or its stuck in open loop

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Haven't had anything to do with stock ecu tunes or barras, so of no help there.  but  kinda sound more like a tune issue, if your mate complained about it after it was tuned.    changing the cooler piping generally wont mess with the tune that much.    
probably worth taking it to someone who knows there shit for retune,  if has some kinda weird fuel model wizardry as roman says.   possibly also more cost effective to go that way to diagnose a potential issue than buying the hp tuners stuff  and/or throwing parts parts at it 

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From memory the fuel model on the Barra engine uses a principle of "Minimum MAP" at each rpm point 
As in, if you are at 3000rpm, you might have zero airflow coming into the engine and the motor will be able to generate vacuum at a maximum 45kpa absolute pressure in the intake manifold. But if you are at 6000rpm throttle shut, it might get down to say 20kpa

Based on this part of the map here:

Capture.thumb.PNG.60f568c507e44ad94c67896c4faa57d5.PNG

Then it uses some extrapolation weird shit wizardry to model the airflow on both sides of the throttle body to work out a mass flow number. based on a combination of these numbers and actual MAP value. So its like an incredibly complicated way to give the same result that a MAF does. 
I'm not sure if all of the barra motors are like this, Dan was trying to explain it to me once and I couldnt quite get my head around it. So my explanation above might not be quite on the money. But I believe it's something weird like that. 
If you fuck with some of the tables to bodge your fuel throttle values to be correct, then you absolutely screw yourself in low load areas where the calculations end up way wrong.

I think some of them do just have normal MAP based tables though, in which case, yeah probably just has a shit tune on it!

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