Audi v8 with ITBs

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SlowRiot
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Audi v8 with ITBs

Post by SlowRiot »

Hello folks, I'm new so introducing myself here. I'm located in the South East of England.

I'm building a mid-engined sports car of my own design, with a TIG welded tubular steel spaceframe chassis, VARTM moulded carbon fibre bodywork, pushrod actuated suspension, and moderate aero. Styling will follow function - overall it'll be reminiscent of late 80s / early 90s Le Mans prototypes.

This is to be powered by an Audi 4.2 litre 40 valve V8 (engine code AVP). This 5-valve-per-cylinder engine has variable valve timing on the intake cams. I'll be replacing the triple-stage variable length intake and electronic throttle with cable-driven individual throttle bodies. This is mated to a 6-speed manual Getrag transmission from a Porsche 987. The engine makes ~360bhp in stock form, I think I can get this up to around 430 with the ITBs and a good tune.
image.png
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I've just received my Proteus v0.4 (thanks to Andrey for the very fast shipping!) which will do the hard work, and I've already begun tinkering with the firmware. In my other life I'm an experienced C++ developer, so I'm not afraid to get my hands dirty with the code. However, this is my first full car build from scratch, and my first custom EFI project - I've never even used TunerStudio before - so I'll be learning a lot along the way.

I'll update this thread with any interesting milestones relevant to RusEFI. The first step will be to create a test loom and get the injectors spraying and coils sparking - but before that, I'll need to add my firing order to the code!
mck1117
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Re: Audi v8 with ITBs

Post by mck1117 »

Welcome to the project!
SlowRiot wrote:
Fri Mar 05, 2021 7:27 pm
I'm an experienced C++ developer, so I'm not afraid to get my hands dirty with the code.
we're excited about this part :D
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Re: Audi v8 with ITBs

Post by AndreyB »

SlowRiot wrote:
Fri Mar 05, 2021 7:27 pm
I'm an experienced C++ developer, so I'm not afraid to get my hands dirty with the code
That sounds very promising!

I've already implemented some code on the way towards two cams X two banks but do not remember where exactly I've got distracted with real life.

I assume you've discovered the magic of https://github.com/rusefi/rusefi/tree/master/unit_tests it might have some coverage for dual cam decoding but probably no coverage for dual bank PID control for the same cam.

Orange instead of yellow on the valve covers would be +2 extra HP.
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Re: Audi v8 with ITBs

Post by AndreyB »

Is it this 4.2?

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Re: Audi v8 with ITBs

Post by SlowRiot »

Haha, fortunately not that engine, no. Some variants do suffer from a propensity to timing failures, but those tend to be the chain-driven engines. The AVP that I have is a hybrid chain/belt design - it has a timing belt for the exhaust cams which has proved to be very reliable, and short chains connecting the intake VVT sprocket and the exhaust cam sprocket. Those have hydraulic tensioners, as long as they're looked after you don't get any failures.

I'll have a look at the unit tests when I'm closer to the part of the project where I can try to get the VVT working - it's very early days yet, I'll consider it a major breakthrough once I just have the engine idling.

I'm building pretty much everything from scratch, so I can't just test the engine in an otherwise running car - for example, I have no fuel system as of yet, nor any proper power distribution - so I can't just plug in and start playing. I'm building an engine test stand for this engine so I don't have to complete the rest of my car just to get it running - that has its own radiator, battery, fuel pump and filters, and electronic throttle control. I know RusEFI supports electronic throttle, but I won't be using the electronic throttle in the final project, so I built a simple arduino-based standalone unit.

The idea is to get the engine running reliably with the stock intake first of all, and only then replace the intake with ITBs, so I'm not changing too many variables at once. But before that, I'll be happy once I just see fuel spraying and sparks sparking in the right order!
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Re: Audi v8 with ITBs

Post by AndreyB »

SlowRiot wrote:
Fri Mar 05, 2021 8:05 pm
but I won't be using the electronic throttle in the final project, so I built a simple arduino-based standalone unit.
is not that too much extra effort? why not start with rusEFI ETB as separate wires and depin those later?
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Re: Audi v8 with ITBs

Post by JRD McLAREN »

SlowRiot wrote:
Fri Mar 05, 2021 8:05 pm
Haha, fortunately not that engine, no. Some variants do suffer from a propensity to timing failures, but those tend to be the chain-driven engines. The AVP that I have is a hybrid chain/belt design - it has a timing belt for the exhaust cams which has proved to be very reliable, and short chains connecting the intake VVT sprocket and the exhaust cam sprocket. Those have hydraulic tensioners, as long as they're looked after you don't get any failures.
This is the same system as 1.8T 20V 132kW I4 version. (Leon Cupra)
Tensioners changes valve overlap on both cams.

Do you have CAM Sensor on intake side ..? One or Two ..??
.. some Proteus and microRusEFI for sale in Europe ..
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Re: Audi v8 with ITBs

Post by SlowRiot »

AndreyB wrote:
Fri Mar 05, 2021 8:19 pm
SlowRiot wrote:
Fri Mar 05, 2021 8:05 pm
but I won't be using the electronic throttle in the final project, so I built a simple arduino-based standalone unit.
is not that too much extra effort? why not start with rusEFI ETB as separate wires and depin those later?
I already built it while I was waiting for the Proteus :) Very simple PID based controller, has a bit of overshoot but it doesn't matter for this application.

JRD McLAREN wrote:
Fri Mar 05, 2021 8:42 pm
This is the same system as 1.8T 20V 132kW I4 version. (Leon Cupra)
Tensioners changes valve overlap on both cams.

Do you have CAM Sensor on intake side ..? One or Two ..??
There's one cam sensor per bank, on the intake cam - two cam sensors in total, plus the crankshaft trigger wheel sensor (60 / 2 missing tooth trigger wheel). All hall effect sensors.
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Re: Audi v8 with ITBs

Post by mck1117 »

IIRC your VVT is actually just on-off, not continuously variable. At least it is on the Audi 2.7T, where the two actuators are wired in parallel, so you don't get any per-cam fine control.
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Re: Audi v8 with ITBs

Post by JRD McLAREN »

mck1117 you are fastest then me ... :)

SlowRiot: would you can post the engine code ..??
I will send you any data from Elsa, if you wish ...
.. some Proteus and microRusEFI for sale in Europe ..
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Re: Audi v8 with ITBs

Post by mck1117 »

JRD McLAREN wrote:
Fri Mar 05, 2021 9:20 pm
SlowRiot: would you can post the engine code ..??
AVP
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Re: Audi v8 with ITBs

Post by SlowRiot »

I've now raised a merge request to add the AVP's firing order (1-5-4-8-6-3-7-2). I'll add a whole engine definition eventually, when I make a bit more progress.
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Re: Audi v8 with ITBs

Post by Simon@FutureProof »

It may be helpful to you that I am based on the eastern end of the south west of england.
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Re: Audi v8 with ITBs

Post by AndreyB »

Hold on, what is the original donor vehicle? Any chance that this 8 cylinder engine would work with the https://github.com/rusefi/hellen121vag ECU we are trying to finish _soon_?
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Re: Audi v8 with ITBs

Post by Simon@FutureProof »

265 kW (360 PS; 355 bhp) at 7,000 rpm; 430 N⋅m (317 lbf⋅ft) at 3,400 rpm — AQH, AVP, AYS, BCS
applications
Audi D2 S8 (AQH: 05/99-02/01, AVP: 09/00-09/02, {Japan only – BCS: 09/00-02/01, AYS: 02/01-09/02}) "ID and data from ETKA".

https://en.wikipedia.org/wiki/Audi_A8#S8
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Re: Audi v8 with ITBs

Post by SlowRiot »

AndreyB wrote:
Sat Mar 06, 2021 2:43 pm
Hold on, what is the original donor vehicle? Any chance that this 8 cylinder engine would work with the https://github.com/rusefi/hellen121vag ECU we are trying to finish _soon_?
As OrchardPerformance says, the donor was a 2002 Audi S8. Other variants of the 40 valve 4.2 v8 appeared in the following cars: D2 A8, D2 S8, C4 V8, C4 S4, C4 S6, C5 A6, C4 S6 Plus, C5 S6, D2 S8, C5 A6, RS6, D2 A8, C5 S6, C5 RS6, C5 RS6 Plus

Although the engine codes are different for all of those cars, the specific configuration required to run the engine should be very similar between them all.

I still have the donor's ECUs and the remains of the labelled and cut harness. If it would be helpful to the VAG compatibility project, I can upload some photos of those for your reference.
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Re: Audi v8 with ITBs

Post by Simon@FutureProof »

That would be great, longer term we could probably add some of that to the wiki.
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Re: Audi v8 with ITBs

Post by AndreyB »

SlowRiot wrote:
Sun Mar 07, 2021 5:06 pm
cut harness
was accounting for 2003 4.2 sounds like yours would work?

Have you already cut the connector off on your harness? What's the probability of you getting another harness with connector still in place?

Hellen121vag needs a 30 second promotional run on a v8 that would be huge for Hellen and rusEFI marketing :)
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Re: Audi v8 with ITBs

Post by AndreyB »

sexy stuff :)
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SlowRiot
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Re: Audi v8 with ITBs

Post by SlowRiot »

AndreyB wrote:
Sun Mar 07, 2021 5:18 pm
Have you already cut the connector off on your harness? What's the probability of you getting another harness with connector still in place?

Hellen121vag needs a 30 second promotional run on a v8 that would be huge for Hellen and rusEFI marketing :)
Would love to help, but I don't know if my engine would be a good candidate for a stock compatibility demonstration. I have stripped the harness entirely - I didn't just cut the connector, I've removed the whole thing - I don't intend to use any of the stock harness, I'm replacing it with a set of proper motorsport-grade custom harnesses.

Additionally, I have some significant differences from the stock car:
  • Intake manifold, fuel rail and electronic throttle already removed to replace with a cable driven ITB assembly.
  • Non-standard injectors
  • Vacuum system removed entirely, won't need vacuum in my car. The stock engine uses vacuum actuation for the variable length intake manifolds and the exhaust air injection system.
  • Exhaust air injection system deleted (not really important for an aftermarket ECU but a difference from stock).
  • PCV system deleted (again, not really a problem).
  • Non-standard accessory belt configuration, aircon and power steering delete (ditto).
  • Custom flywheel with timing ring in a different place to the stock engine, non-standard flywheel sensor position (this was mounted on the automatic transmission in the engine donor, but the Porsche transaxle I'm using expects a sensor on the engine side - needs to be modified to mount it).
Most of my changes are reversible, and I have all parts of the (cut and labelled) harness, and could splice it back together without much trouble if needed. But even then the crank signal would still be different from stock because of the flywheel / transmission change - it wouldn't really be a demonstration of a VAG-compatible system anymore, which is why I don't think it would be too much use for you.

Still, if you want to send over a unit to test, we could probably adapt it to my engine without too much work, if all that matters is getting a V8 running with the Helena. In fact I could switch my plans to use the Helena board instead of the Proteus I've already started with - do you think there would be a benefit in doing that?
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Re: Audi v8 with ITBs

Post by SlowRiot »

AndreyB wrote:
Sun Mar 07, 2021 5:50 pm
sexy stuff :)
You found my insta :) Just a simple arduino setup to physically verify that all injector outputs fire, and in the expected order - will need to make something similar for the ignition coils next. I'll share the sketch once I've tidied it up a bit.
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Re: Audi v8 with ITBs

Post by Simon@FutureProof »

There is a desire to build a whole ECU stimulator like the Jimstim for rusEFI.

Blundar on here is heading up the task and I am sure he would appreciate the help from an additional skilled coder.
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Re: Audi v8 with ITBs

Post by mck1117 »

SlowRiot wrote:
Sun Mar 07, 2021 5:57 pm
Most of my changes are reversible, and I have all parts of the (cut and labelled) harness, and could splice it back together without much trouble if needed. But even then the crank signal would still be different from stock because of the flywheel / transmission change - it wouldn't really be a demonstration of a VAG-compatible system anymore, which is why I don't think it would be too much use for you.

Still, if you want to send over a unit to test, we could probably adapt it to my engine without too much work, if all that matters is getting a V8 running with the Helena. In fact I could switch my plans to use the Helena board instead of the Proteus I've already started with - do you think there would be a benefit in doing that?
With the changes you've made it's probably not worth trying to run a PnP - not really a benefit to PnP when you're building a harness from scratch.
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Re: Audi v8 with ITBs

Post by SlowRiot »

SlowRiot wrote:
Sun Mar 07, 2021 6:06 pm
... I'll share the sketch once I've tidied it up a bit.


Each column of LEDs corresponds to a cylinder of the engine. The first LED of the column will flash white while the injector is commanded to open, and then change colour depending on firing order. If this was the correct cylinder in the firing order, it turns green, otherwise it turns red, and highlights the correct cylinder (that should have fired) in yellow. The rest of the LEDs in the column provide a timeline, scrolling one step along for each new pulse that's received.

Here's the sketch: https://github.com/slowriot/arduino_efi_monitor

In the video, I've adjusted self-stimulation idle to just over 100RPM for visual clarity. By the way, is there a command to adjust the RPM at runtime without recompiling the car definition? EDIT: turns out you can do it with `rpm 7200` etc.
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Re: Audi v8 with ITBs

Post by JRD McLAREN »

short wiring diagram for this ..??
(I have one free arduino nano)
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Re: Audi v8 with ITBs

Post by SlowRiot »

JRD McLAREN wrote:
Mon Mar 08, 2021 8:18 am
short wiring diagram for this ..??
(I have one free arduino nano)
It's literally just what you see in the video - choose any digital pin to drive the LED display, choose any other digital or analogue pins (and assign them in the sketch at the top) to wire to each injector output. I chose the first 8 analogue pins in a row, and that's what the sketch uses by default. There's no other wiring or any other components besides what's visible in the video thumbnail image.
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Re: Audi v8 with ITBs

Post by SlowRiot »

Cam sensors

For future reference, some detailed information on how the cam sensors behave on the Audi 40v 4.2 AVP V8; apparently this is the same in the 5-valve V6 engines too. Pages are in German, but it has the very helpful waveform illustrations:
image.png
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image.png
image.png (207.94 KiB) Viewed 17072 times
In summary, they cam sensors are used primarily to facilitate the fast start feature, which is also augmented by the factory ECU remembering the halt position of the engine. Two cam sensors are used for redundancy only. There's no mention of VVT here - as the VVT actuators are simply on/off, there's no need for closed loop feedback.

Can anyone see any benefit in even connecting up these cam sensors other than to try fast starting?
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Re: Audi v8 with ITBs

Post by mck1117 »

That cam pattern is indeed the "Bosch Fast Start" pattern that's extremely common, even on cars to this day.

The "real" benefit you'd get from connecting at least one cam sensor is that you can run full sequential, instead of wasted spark.
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Re: Audi v8 with ITBs

Post by SlowRiot »

mck1117 wrote:
Thu Mar 11, 2021 4:13 am
The "real" benefit you'd get from connecting at least one cam sensor is that you can run full sequential, instead of wasted spark.
Forgive the EFI-newbie question, but why couldn't I do that with just the crank signal?
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Re: Audi v8 with ITBs

Post by mck1117 »

SlowRiot wrote:
Thu Mar 11, 2021 8:22 pm
Forgive the EFI-newbie question, but why couldn't I do that with just the crank signal?
A 4 stroke engine completes a full cycle in 720 degrees (2 revs) of the crankshaft. Every cylinder fires every other revolution because it takes two cycles up/down of the piston in the cylinder to operate a 4 stroke engine. The crank sensor can only tell you where you are within a particular revolution, not "which one" it is in the larger 720 degree cycle. But the cams spin at half speed! So if we put a sensor there, we can resolve the engine's position in the 720 degree cycle.

Consider the simpler case of an inline 4: cylinders 1 and 4 move together, and cylinders 2 and 3 move together. Firing order 1-3-4-2.

0 degrees -> cyl 1
180 degrees -> cyl 3
360 degrees -> cyl 4
540 degrees -> cyl 2
720 degrees = 0 degrees -> cyl 1 again

Without a cam sensor, the best we can do is:

0 degrees -> cyl 1 or 4
180 degrees -> cyl 2 or 3
360 degrees = 0 degrees -> cyl 1 or 4 again

NOTE: "fully sequential" gets touted as some holy glorious ideal of EFI, but it's not really required. You'll get better idle emissions and slightly better fuel economy, but at high load/rpm, you're not going to notice a difference. The only potential real difference is that since you know only when a pair of cylinders is firing, you have to fire the ignition system twice as often (hence "wasted" spark), so that can put more heat in to the coils.
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