DIY Fuel injection thread.

[Roman]

Yeah the redtop engine was just a normal cam gear on the exhaust side. 

Never bothered fitting an adjustable one on it, as going to dual VVTI was always on the cards. 

[japawagons]

Just now, Roman said:

Yeah the redtop engine was just a normal cam gear on the exhaust side. 

Never bothered fitting an adjustable one on it, as going to dual VVTI was always on the cards. 

Would the Standard exhaust Cam be relatively limited in the overlap that can be produced then? So unless the difference between the 2x exhaust manifolds is significant in regards to the clearance of exhausts gas on the exhaust stroke, then your unlikely to be able to measure a significant change in MAF.

If the designs were conducive to creating scavenging then you'd require Dual VVTi to generate Overlap and aid your dip??

Might be waaay off. Likely waaaay off.
 

[Spencer]

Your MAF graph looks like my variable cam fuel tables in 2D /ling

[Yowzer]

Just now, ajg193 said:

Other than that you really can't say too much without an accurate dyno.

That's not true at all. You can very effectively tune an engine based on its own data. Most top motorsport does their final tuning on the track / strip based on datalogs.

For example if you want a comparative result of power to gauge changes, a differential calculation of the engine rpm will give you an incredibly accurate power curve. It won't tell you exactly what the power is without a bit of extra math, but it is sufficient for tuning purposes. I use this method all the time at work to spot dodgy cylinders / blown head gaskets etc

[ajg193]

Accurate to detect the half a percent changes that Roman is looking for?

/I know dynos aren't that repeatable or accurate either

I concede. You are 100% right about everything

[japawagons]

Just now, Yowzer said:

That's not true at all. You can very effectively tune an engine based on its own data. Most top motorsport does their final tuning on the track / strip based on datalogs.

For example if you want a comparative result of power to gauge changes, a differential calculation of the engine rpm will give you an incredibly accurate power curve. It won't tell you exactly what the power is without a bit of extra math, but it is sufficient for tuning purposes. I use this method all the time at work to spot dodgy cylinders / blown head gaskets etc

I absolutely agree, but please explain method. 

Fuck I have been away from interesting shit on cars for too long, my brain don't work no more. Ex Mechanic Decline is real and fuck it's quick.

[Yowzer]

The dyno measures a change in acceleration at the wheels, but you can measure the exact same change at the engine directly. You just have less control over the variables on a road.

Unless you have a braked dyno which is a different story, that is far better for tuning fuel efficiency since you can hold the engine at a constant RPM while playing with numbers, which much harder to do on a road tune due to running out of road.

[ajg193]

Just now, Yowzer said:

The dyno measures a change in acceleration at the wheels, but you can measure the exact same change at the engine directly. You just have less control over the variables on a road.

Unless you have a braked dyno which is a different story, that is far better for tuning fuel efficiency since you can hold the engine at a constant RPM while playing with numbers. 

I'm assuming a braked dyno such as a dynapack.

Inertia dynos are practically obsolete for these sorts of applications as far as I am aware.

[Yowzer]

Just now, japawagons said:

I absolutely agree, but please explain method. 

Fuck I have been away from interesting shit on cars for too long, my brain don't work no more. Ex Mechanic Decline is real and fuck it's quick.

Record RPM, chuck car in 3rd and pin it until redline. A differential on the RPM graph will give you engine acceleration over time, which should directly match engine torque. Chuck another little bit of math on top and you'll have a representation of power (slightly inaccurate due to wind resistance at higher speeds, but fine for comparative purposes)

This won't give any torque or power figures, it'll just give you the plot.

[Spencer]

I can plug my data logs into virtual dyno, seems to work pretty well.

[ajg193]

Have you had a play with virtual dyno? (exactly what you describe above)

It's in reasonably close agreement with the curves produced by a real dyno but there is a fair bit of noise in the data. I've used it and it made me sad about how low my power was.

Real dyno just confirmed it.

[ajg193]

You can do like 5 pulls in a row with virtual dyno and they will all be different though.

[Yowzer]

If you're looking for 10/10ths you can probably justify the $200hr for 10 hours of dyno time. In Romans case, chasing a massive torque hole will still be visible with a % or two of inaccuracies.

[Roman]

Just now, ajg193 said:

You can do like 5 pulls in a row with virtual dyno and they will all be different though.

Funny story about this. 
I came to same conclusion, so thought the best test would be somewhere that minimizes all of the possible variables in road etc. 
So I took it to the drags, go gently through first and second, pin it in third from 2000rpm to redline. 

Then I had switches on my dash where I could add different combinations of ignition advance or retard, try same thing again. 

I compared all of the logs and they looked exactly the same. I became dismayed and decided it wasnt accurate enough.

Then I went to an actual dyno and the car did exactly the same thing. As it's got a fairly broad plateau of effective ignition timing so isnt very sensitive to it. 
So it turns out virtual dyno was actually correct, I just didnt want to believe the results.

[Yowzer]

Back on the subject of improving efficiency, has anyone considered converting to Miller cycle?

https://www.researchgate.net/publication/322864331_Effects_of_applying_a_Miller_cycle_with_split_injection_on_engine_performance_and_knock_resistance_in_a_downsized_gasoline_engine

[ajg193]

Heaps of nice flat empty roads available at the moment.

It's a shame my car is boxed in by flat mate and I'd go to jail for hooning around. /it doesn't need any more tuning anyway.

 

Seeing how you can get a measureable change with virtual dyno, why not just use that instead of MAF or are you just trying to see what you can glean from different methods?

[Roman]

52 minutes ago, ajg193 said:

Accurate to detect the half a percent changes that Roman is looking for?

/I know dynos aren't that repeatable or accurate either

I concede. You are 100% right about everything

I'd not bother chasing half a percent... 

Keep in mind that 0.647 grams of air is 100% VE.

Here's an example at 4600rpm

At 35 degrees inlet cam advance I get  0.636 g per cylinder
At 5 degrees inlet cam advance I get   0.505 g per cylinder

That's 25% more airflow.

At 8000rpm 

At 10 degrees inlet cam advance I get  0.631 g per cylinder

At 35 degrees inlet cam advance I get  0.549 g per cylinder

So thats 15% more airflow by optimizing the cam angle.

And notice you cant have your cake and eat it with a fixed cam, as the numbers are near opposite.

[Roman]

Just now, ajg193 said:

Heaps of nice flat empty roads available at the moment.

It's a shame my car is boxed in by flat mate and I'd go to jail for hooning around. /it doesn't need any more tuning anyway.

 

Seeing how you can get a measureable change with virtual dyno, why not just use that instead of MAF or are you just trying to see what you can glean from different methods?

Because MAF is the most accurate and repeatable tool available for assessing airflow.

Once the airflow is correct, then you can get your AFR correct with a wideband, then you can get your ignition timing correct with virtual dyno, a real dyno, or whatever.

Ignition timing was what I was hoping a dyno would be the silver bullet for, as there's no other methodology that felt accurate enough. 

But it turns out my sluggy engine just isnt that responsive to timing for whatever reason. 
Possibly due to a long dwell at TDC because of rod/stroke ratio or something.

[Yowzer]

You need a longer rod m8

And more komprezzions

[ajg193]

I'm not trying to attack you or criticise your method. Please don't take it like that.

But if it's power you're chasing why not just optimise for power? When you're adjusting cam timings and exhaust manifolds it's not just air flow that's important - as you've already stated.

 

Isn't air flow mainly just used for calculating the fuel input in OEM applications? I would have thought that other settings (cam angle, ignition advance etc) are determined based on other sensors (TPS, temperature etc) and calculations, I genuinely don't know anything about modern cars though so I could well be wrong.