yoeddynz

DIY Fuel injection thread.

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Sooooooooo my favourite mystery topic. 
Part throttle Variable cam tuning.

I did some tests tonight to try find out what cam angle might be "best" at a given throttle angle. By best I mean max airflow as read by the MAF.
I used E-throttle to limit throttle angle to 30% max and did some pulls through the rev range, logging the MAF and MAP values as I increment through the intake cam angles in 5 degree steps.

As expected, both the MAF and MAP values change as you advance the cam. But what was interesting is that there is loosely a correlation between achieving the strongest vacuum, and highest MAF reading.

At 4000rpm with 0 degrees cam advance we are losing 11kpa and have 0.406 grams per cyl. 
At 45 degrees advance we are losing 16kpa and have 0.488 grams per cylinder of airflow. 
So 45% more vaccum and 20% more airflow.

At 5000rpm with 0 degrees cam advance we are losing 20kpa and have 0.416 grams per cylinder.

With 35 degrees cam advance we are losing 24kpa and have 0.456 grams per cylinder. 20% more vacuum and 9% more air.

So whats interesting about this is you dont always have a MAF available for cam angle tuning but it loosely correlates to MAP.
As a general rule from my testing it seems if you can get 10% more vacuum you'll get 5% more airflow.

Similar to ignition timing though it looks like it ramps up quickly to best values then plateaus over a cam timing spread. 
I'll post something better later on once I've had a chance at figuring out how to format this mess of data.

But seems like there's a fairly clear correlation which makes sense, if you are improving VE via cam timing then you are increasing the air demand... which the throttle restricts hence extra vacuum.

I'll do some more tests at lower throttle with higher vacuum too and see if I'm getting similar results.

Something else thats really interesting is that the best cam angle settings even at this low throttle angle are much higher than I would have expected. Based on absolutely no evidence I've just been slowly ramping the timing down towards zero throttle. It looks like past maybe 10-15% throttle it's just going to be the cam in a position very close to WOT for max airflow.

It will be interesting to see if we see the same trends with much stronger vacuum. Will do some more tests through the week!

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guessing it depends what you are shooting for?    economy or power  or just science?    will assume science. 
but if economy.  would it not be better to go the other way to a point,  less advance and higher throttle opening to get the same airflow. which would reduce pumping loss?

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Are the camshaft actuators designed to be used so much? They seem like the sort of thing that would wear out quickly if used 10x as often as OEM. 

 

/Chinese oxy sensor is still working 

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They move constantly. If you've ever watched the live data on a VVTi car, they dance around all over the show.

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16 hours ago, kpr said:

guessing it depends what you are shooting for?    economy or power  or just science?    will assume science. 
but if economy.  would it not be better to go the other way to a point,  less advance and higher throttle opening to get the same airflow. which would reduce pumping loss?

Yes so this is why part throttle stuff is so complex/interesting.
As you say, what is the point of part throttle... You're obviously not trying to make max power or max airflow.

So yes for me economy is the primary consideration, but also trying to get a good understanding of why things are beneficial while I've still got a good suite of sensors attached.
As I want to come up with a good methodology for finding best cam angle when only MAP or TPS available as a reliable load axis. (ie quads)
At the moment I can observe the effects and see why changes are beneficial but I honestly have no idea exactly why they are.
Seeing the map signal change how it does in relation to MAF was an interesting thing.

Sooooo I think I've found what I'm after.

It only happens in the higher rpm of my test because 30% throttle doesnt pull enough vaccum to make it happen at lower rpm.

But generally you see the MAF signal increase as the manifold pressure goes down because of increased VE. 
Buuutttt when intake manifold pressure gets low enough and there is enough overlap you start getting exhaust gas pulled back into the cylinder.
When this happens map signal goes up and maf signal goes down.
You can see here it only starts to happen right at 45+ degrees cam advance, the trend reverses:
(Sorry havent labelled axes cos I'm a cretin but that's cam advance on horizontal and arbitrary rescaled numbers on the vertical)
Capture.PNG.de5edf134bc6919abd9be82253a55d8b.PNG


I think the 45 deg mark is the critical point where you start getting EGR effect happening. So thats whats relevant for economy, finding that point at each load/rpm combo.
So I would expect if I run this test again at lower rpm with the same vacuum level I will start to see those converging lines start to happen at a much lower cam advance angle.
As at half the rpm you have twice as long for a given amount of overlap to start pulling air back in from the exhaust.
These tests even at 5500rpm are still at 75kpa give or take, so not much vacuum generated! 

Will try again later tonight and try get some ~2500ish rpm results at maybe 40-50kpa hopefully.

I think when I swap to a dual VVTI engine and can adjust the exhaust side too. You will be able to make convergence happen sooner without the VE increase that comes from advancing intake cam.
So can set the intake cam angle for worst VE / best pumping losses and exhaust cam for best EGR effect.
I hope it works out as clearly as it seems it might! 

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Doing the test again at 10% throttle was pretty painful haha. 

But some graphs from each rpm range. The horizontal scale is cam advance degrees and the vertical scale is map pressure drop from atmospheric (divided by 2)

2500rpm.PNG.bec454efdfb780361c184ec0d1d1508e.PNG

 

3000rpm.PNG.7e65489f6b67caf37e64c7b61e481138.PNG

 

3500rpm.PNG.79501dac1e8af7db677112e3ca833f5d.PNG

 

3750rpm.PNG.91fd455d55cc4f2d6842d2715fa2667f.PNG


Conclusion: No idea to be honest. The MAF reading seems to be much more resilient to cam timing changes than expected. 
MAP is swinging around all over the show but it seems to cause very little resistance to fresh air coming in. Which maybe makes sense.

I can say this though, once I got to around 40 degrees advance the car felt like it lost heaps of power.... Took a long time to get to 60kph in third haha.
So perhaps that is the EGR effect at work. Probably needs heaps more ignition timing.

Ultimately though this hasnt shown me anything as insightful as I was hoping and I'm not sure what the conclusion is here. 

Thanks for reading / sorry for pointless post / etc

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Okay I think looking at the data in megalog viewer gives some more sane results / actual labelled axes etc 

52989893_651250925329889_5102338997808529408_n.jpg.ee0fa74e5f15a9e6b9626dc835bf06f2.jpg

If we look at the cam timing angles which give the maximum vacuum then the results sanity check quite well against my full throttle cam timing. 

If you aim for minimum vacuum then it basically just says bang in 50 deg advance everywhere haha. 

So this is ramping up my cam advance much more aggressively than before but it's settling on around 20-30 degrees at 30% throttle which seems reasonable. 

It also sanity checks against the toyota documentation where it says "advance cam about half way" for medium load conditions.

Will have to take it for some nangs though and see what its like now / maybe do same thing again at a few more throttle iterations. 

If this works well then I'll have a MAFless method for doing the same with quad throttles which is excellent news! 

 

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So I got a new wideband and setup the fuel nicely for the new cam angles, and went for a bit of a drive out of town. 
I also had my new dash setup with a realtime economy gauge so you could see what's happening and adjust your behaviour to suit. 
Results from a ~2 hour drive from Auckland to Morrinsville:

Capture.PNG.1f5661e100c10609de0ace4f7c793b97.PNG

Pretty stoked with that! One of my goals has been to get it into the 6l/100 range but I thought I'd need the dual VVTI engine and the revised 6th gear ratio to acheive that.
The mean cam angle value for the trip was just a shade under 20 degrees, when it was previously around 10.
It's hard to say whether improvements came down to having the economy gauge of the cam angle changes but good results.
So either way thats a win. Felt nice to drive in any case.
Having that realtime gauge was great though, in some situations where you think you're better off going straight to 6th to keep the revs low you cut the fuel consumption in half by staying in 4th or whatever. 
Other situations the opposite. Seemed really counter intuitive but I think that'll stay on my dash screen for sure! 

One suprise is that the car is actually quite economical just trundling around the 50kph mark.

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does bumper to bumper takanini friday afternoon traffic help due to lower wind resistance/drafting effect?

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Starlet is finally running ECU controlled ignition timing.

Runs well, will throw it on the dyno on wednesday probably and give it a good ignition map.

Just need to resolve the sync loss issues during cranking. It looks like there is interference from the new starter motor. I might try making it just skip a few more pulses before attempting to sync.

Running 35 mm diameter 20-1 wheel with VR pickup at cam speed. I guess 35 mm diameter is a bit small, but OEM does it like this quite often so it shouldn't be too bad.

 

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It might help to set the arming threshold/voltage for your VR a bit higher if there's a table for that in your ECU

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@ajg193 Got a 'scope trace of it? (can loan you one, or you could use an old android phone).

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1 hour ago, h4nd said:

@ajg193 Got a 'scope trace of it? (can loan you one, or you could use an old android phone).

It was fine on the scope, just too low voltage at cranking speeds to be of any good.

 

Instead I've made this to pick up a signal from outside (goes up and over) the vr sensor (59 mm vs 35 mm diameter). Should give significantly higher cranking voltage and the teeth are more evenly spaced compared to the worn out gear. This one is 30-1 teeth. I've also modified the pickup so it can read from the outside.

15532255312413379310582465864189.thumb.jpg.700432b18e62c483bc09e0946ad9f107.jpg

 

Hopefully the steel going over the vr sensor won't interfere with the signal. I'll throw it on the oscilloscope as soon as I weld it to the distributor shaft

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According to oscilloscope it gets slightly over 0.5v peak to peak at approx cranking rpm (400 rpm).

I managed to break my rotor so will need to buy one in the morning before testing it. 

20190322_182436.thumb.jpg.7f2fe4494e82ed53080ca6730c6f62f7.jpg

with all this effort I could have just gone crank trigger with coil on plug wasted spark, but I'm known for going to insane lengths to make something that looks factory.

 

I still need to make a cover for the igniter so it isn't blatant

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Had same issue using stock  toyota triggers with ms back in the day.   my half assed solution was to run super tight clearance between  trigger wheel and vr sensor. to get voltage up when cranking

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Not much room for my stock carb... 1504724551_2019-03-2309_23_21.thumb.jpg.187f508f563a35a606a2ce9656adcaf8.jpg1792699875_2019-03-2309_23_33.thumb.jpg.4d574df76f8b0c29e703b106e433a2fe.jpg

 

Bugger. But heaps of room for sidedraft! I guess I'll just have to make some itbs and go injection :-)

 

In the future. When my money tree has grown more leaves. 

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I saw an injection turbo manifold for an A series the other day.

Sounds like it would be the most economical. Plus Italians love tiny turbos

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Turns out I wasted all my time and too much $ on the ignition setup. A 30-1 wheel at cam speed on a 4 cylinder doesn't work with the math used by a microsquirt.

 

Straight back to fuel only.

:'(

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Yeah a turbo would be ace. However.. I can most likely sneak injection past my wof guy but certainly not a hairdryer. 

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