Jump to content

DIY Fuel injection thread.


yoeddynz

Recommended Posts

ive got some big (in comparison to stock) 450cc injectors from an evo or a gsr or something like that, i forget exactly, they were cleaned and flowed and on trademe, so who knows if they actually were, but they looked tidy. 

ive banged it back to 4 squirts as it is WAY nicer. on 2 squirts it behaves the same crappy way as 1 squirt. it would probably run better once warm but its still an utter dog to start. crank the engine and itll fire and die after a couple cylinders fire, do this 20 times and maybe youll get the engine started, but more than likley youll just run the battery dead and have to wait for the battery charger. 4 squirts fires right up, throttle blips are super snappy and AFR (the small portion thats tuned at this stage) is steady.

i was probably a bit harsh saying the map was 4 times too rich, its probably closer to 2 times too rich, but autotune (to answer that question yes i do have a full version of tuner studio) has brought the idle back in check nicely and i see no reason why it wont bring the rest back. i was worried about requesting such a small ms at idle with 4 squirts but it seems to behave. 

ill hopefully get out for a few late night runs around the block to get the base tune right before i get it on the track and start working through it. untill i blow it up and take the S4 out for a hoon :D 

  • Like 1
Link to comment
Share on other sites

  • Replies 2.4k
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

From what i remember of tuning my car, you shouldnt be relying on auto tune to tune the idle. Do that manually, and then block out auto tune from touching that area.

If you havent already, it would be worth you going over the MS manuals, as they have some really good information on setup and tuning.

  • Like 2
Link to comment
Share on other sites

i read them ages ago when i first setup the map but have probably forgotten it all, will give it another read now. but i hadn't really got a good chance to drive the car other than some worried late night runs as the thing is totally illegal. i really just want to get it running nice enough and reliable so it can go for cert without getting stranded in the middle of the workshop. 

will sus the idle (its pretty good) and lock it out. one slightly worrying thing is that at idle my VE numbers are looking very low. single digit low. i assume this is something to do with the dead time and running 4 squirt as it used to be around 35. but also, it works, and im not too inclined to change something that works just because its not showing up right. the rest of the map, under load is only looking to be about 20 - 30% too rich the more i get into it. it was just idle that was wildly different. 

anyway off for another 10 minute worried run. 

Link to comment
Share on other sites

that is 100% what i assumed is happening, the last map was band aid fixing the issue it had. 

in other megasquirt news. today at work we got our v12 mercedes sl600 AMG race car up and running on ms3x. i put together the start up tune and it fired up first pop once we got the crank trigger sorted. so i was very proud and super stoked. 

the exhaust it pretty open and it sounds fucking ruthless. same engine as the first Pagani Zonda. hopefully we can get it finished and out to the trackday on wednesday and get some tune into that too, 

  • Like 6
Link to comment
Share on other sites

3 hours ago, yoeddynz said:

Oh and congrats for what appears to be landing on your feet with a new job. Sounds good and I'm imagining you're having fun! 

cheers!

I keep meaning to put a post in the depression thread, but every time i read it people are having a way tougher time than i was. but the advice given there was invaluable. focused on the shit job being temporary and kept looking for a new good opportunity and backed myself hard when going for it. 

after my entire professional career being fixing things i got pretty sick of it, and now i professionally break things :compress:cars, trucks buses at high way speeds into roadside barriers. 

hard work, but shit its satisfying, and then at lunch we play with company race cars, which is a seen as a learning and development exercise for all those interested. 

  • Like 6
Link to comment
Share on other sites

Tuning went well today untill i snapped off half the secondary header pipe, which meant any 02 sensor reading would be incorrect. 

 

got an excellent amout of time for autotune to spend on the map. as seen by how dark green the cell weighting panel is getting. clearly i need to extending the tuning further into the rev range but that will come with time, same goes for higher up in the boost, once i fit a new pulley.  (by no means a completed map, the car is still fixing itself after that fueling setting correction) however it was performing very well, with some flat spots. i also need to rescale the map because im not sure why i ran it out to 8000, itll never see that. 

image.png.d9a21ade89a3f83b0bfa057b9333af70.png

 

Link to comment
Share on other sites

I've always battled with idle hunting a bit, even when its dialled in nicely it would always fluctuate "a bit".
Put it down to having a light flywheel and being a bit ambitious with trying to get a low idle speed. 

One thing thats annoying about using MAP as a load axis is that when you are first cranking, it reads 101kpa so dumps a shitload of fuel in when you really only want the amount of fuel for say 35kpa or whatever. MAF does weird shit too where it spikes the air per cyl reading. So it takes a while to crank in either case.

Today I setup a TPS a based idle fuel map, thats only active below 5% throttle and 1300rpm.
Now it starts out with a more sensible fuel amount and cranks a bit quicker, with less of a zing up to a higher than idle rpm.
A 50 deg coldish start reached 1krpm in less than a second. Will be interesting to see if that initial richness has been the problem all along!

Now have a 700rpm idle that is more stable than ever. sweet. Now that this is more stable, I can probably make it smoother again by readjusting the idle ignition trim values. 

My previous scheme of having a higher idle when the car is moving, and then dropping to 700 when the car is stationary is working awesomely too. 

Capture.PNG.026b709e59c64c8ccb322e450af45bca.PNG

  • Like 5
Link to comment
Share on other sites

I've tried a whole bunch of different goal AFRs for idle and somewhere around there works best for me. I have checked the calibration of the sensor and it's correct.

The benefit of having a lean idle is that when you run lean you make less power, so you need more air to make the car idle.

Which is good because as soon as you come off idle you can have your normal fuel map run a lot richer so you get a torque bump which helps the car get off the line a lot easier. And the overall fuel consumption is lower.

I dont quite trust the O2 sensor reading at idle conditions though, I dont think it's quite that lean.
It's possible I have a tiny exhaust leak which only really affects idle, but 16.2 uses the least amount of fuel that gives a stable idle at low rpm.

  • Like 1
Link to comment
Share on other sites

2 hours ago, BobbyBreeze said:

Good work Roman! Crank that idle speed though **think of the cams**

Do you mean, a low idle will increase lobe wear due to less lubrication or something? It still has good oil pressure as the vvti have a big oil pump to account for vvti bleeding oil volume from the system when it operates, and also to account for the oil squirters under the pistons.

Link to comment
Share on other sites

2 hours ago, Roman said:

Do you mean, a low idle will increase lobe wear due to less lubrication or something?

Yep. Love me a high idle. The peak stress over the nose of the cam occurs at idle speed, combined with lowest oil flow equals worn cams/buckets. Worn lifters / cams on flat tappets is so common though I always tell people to high idle even on stock stuff.  It gets so much worse with proper cam profiles and high rate valve springs too. 

  • Like 3
Link to comment
Share on other sites

44 minutes ago, nzed said:

fair call, but is it REALLY going to make a measureable amount of difference in wear on something thats drivn the way our cars are.. like not daily duties, etc etc. i would have thought it would be the high rpm from skidz/drag/dyno runs  that are actually going too create the most problems over idle speed.

 

Don't make me go all DaveScience™ on you can get out some graphs of lobe stress.  But yeah unlikely to be an issue on stock shit that's not daily driven and gets good oil changes. Its just good practice in my mind, so I mentioned it. 

The higher the rpm the peak stress reduces on the nose and increases on the flanks..until you start to loft the valve and there is no stress on the nose.. But the stress on the flanks are a lot less as the radius of curvature is greater. High rpm is actually a lot easier on the cam as long as the valve doesn't overcome the spring. 

 

  • Like 2
Link to comment
Share on other sites

6 hours ago, nzed said:

dave you mentioned that running lean creates makes less power.  can you elobrate on that for me please? compared to say lambda? or what?  i ahd the mindset that if you're running 10% too lean, then you'll make more power than 10% too fat.  but obviously the detrimental reliabilty effects will negate the power increase.  
Just curious to hear your findings on your claim is all?

or is that more specific to your actual setup? is that more due to your specific VE at idle or something else? 

 

To achieve a completely uniform burn, you would need 1 molecule of fuel surrounded perfectly by 14.7 molecules of air. 
But in real life it never mixes that well, so when you run rich, you are ensuring that there is more than enough fuel for every oxygen molecule even if its not quite mixed properly.
Because the limiting factor of making peak power is always how much oxygen there is, since fuel is so much denser than air its a lot easier to spray more fuel in than it is to cram more air in.
As per above it seems that 12.6:1 is that sweet spot of ensuring a good burn and also the cooling benefits of running slightly richer. And also you're only ever reading the average taken across 4 cylinders, and even if it was one cylinder you dont necessarily get a uniform burn anyway. 

When you run lean, 100% of the fuel is consumed but it doesnt generate as much combustion pressure.
But as per above there is that sweet spot for best economy before it all turns to shit.

I've seen some people use the "lots of air" idle method, but then retarding the ignition timing a lot to bring it to the correct idle speed - So that when you come off idle you get a big torque bump from the timing increase.
But my car becomes very noisy when it doesnt have enough ignition timing, my car is *considerably* quieter when I am running 20+ degrees at idle.

But this means the engine is already making near its peak torque capability (of what can be acheived with ignition timing) so running the engine leaner is an alternative method to bring idle speed back down and give some torque in reserve.

  • Like 2
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...