Raceboy

I think I can answer that.
I have tuned the base map by myself on stock 964, that was the 1st that I installed VEMS on, it was the first PnP unit (all is different than 964 compared to Audi unit, 964 ECU controls DME relay differently also, Audi has 3 triggers, different sensors etc).
It does not have stock ignition table but conservatively tuned one and makes a bit more power than stock Motronic, even with old cat converter.

alexjc4

lol, yeah I know, I have lots of questions, as Peep knows only too well now

EDIT - overlapped with post above:
Peep has installed this on 964s previous (both NA and FI) and I understand he has access to a car to test the install before sending it to me, obviously my car other than the cam is fairly standard. This means the base map should account for the injector size and deadtime, the engine displacement, and sensor configurations and ISV operation, cold start etc. From there, you can rely on the fuel requirement calculations, and with speed density, let the VE map and "autotune" to take care of the rest.

Dwell is handled slightly differently in VEMS compared to DME - VEMS uses a simple "map scale" which is a single "gain" setting for how the dwell is effected by map, for boosted application you want MAP compensation for dwell really, the DME uses a 3d table RPM vs VBATT iirc (there's a link to an image of the std dwell table on the first page of this thread) but the important thing is the curve is ok and doesn't cook the coils and the spark doesn't break down under load.

This manual is slightly hard to find in the mess of ten years worth other VEMS documentation on the internet, but it appears to be the most current.

http://www.vems.us/downloads/V3insta...etupmanual.pdf

alexjc4

In terms of mapping I'm happy to do the fueling myself, logging data on the road/track and updating the VE table (of course with guidance from Peep)

Ignition needs to be mapped on a dyno, and I have checked with the guys that look after my Skylines that they are happy to map the VEMS on their 4WD hub dyno. Though of course it's less fraught mapping ignition on a NA car, I am informed that the M64 is still knock limited in some areas (i.e you don't just go to MBT and back off a couple of degrees - you look for start of knock instead).

robt964

Awesome - looks like all the complicated bits are sorted then. Being supplied with a largly complete map that will start and run the engine is a massive leg-up.
I want one, but it makes sense to delay until the guinea pig has finished his test

alexjc4

I'm trying to learn about the injector firing pattern on the standard DME.

I guess it will be something like:
Cranking: Simultaneous injection (all 6 every 360deg crank)
Normal (light/mid load): Timed Sequential injection (onto the "next" closed intake valve)
High load: either bank injection (left bank/right bank alternating 360deg crank) or simultaneous injection

Anyone know more on this?

My understanding is that when you get to 50% duty cycle you may as run bank injection as they will be open half the time anyway and >75% you may as well use simultaneous injection if only to give the injectors an easier life.

With the standard injectors 300-310 seems the maximum "honest" flywheel hp you are going to get and then with some very high duty cycles. They are ~250cc/min at 3 bar and they run at 3.8bar as standard. (Edit:see below 194cc @3bar or 218cc @3.8bar which is what they run at on the car.) To go beyond that, you can either increase the fuel pressure or replace the injectors.

What are the options for aftermarket fuel pressure regulators?

And another question I've been mulling; Is their value in having an EGT sensor when tuning aircooled motors - something in the back of my mind is saying it's actually fairly important. The VEMS has EGT controller(s) built in so I'd guess it would be easily retrofit-able.

Any experts have a view on that? Is the answer is yes, what are the target EGTs?

fuch

Alex do you want me to get my buddy at ecutek to look over this & put you in touch with him for any of this alien talk you speak on this, he may be able to help out a bit ?

Great stuff guys I just wish a had a clue what your going on about

alexjc4

That would be cool! If only to point out any considerations I've missed. He will laugh at me for being a total noob though

PhatPhlatSix

Yes, you're pretty much right on the timed vs sequential. Sequential adds the overhead of start of injection, or end of injection timing, i.e. what values to use. So as you're on low % injection time, i.e. not full power, what do you vary the angle against - emissions? The only time I have found varying the EOI was useful was at a 'trough' point of the torque curve in one particular engine, where it just would not run clean without the right injection angle. If you went for bigger injectors or higher fuel pressure, sequential could make a difference.

Regarding mapping, you could get away with just wide-band lambda. If your lambda is right, then your exhaust temps will be ok and the engine will be fine. With a turbo it would be better to keep an eye on EGT....

fuch

He's going to have a look on Monday at this thread and help where he can...

ras62

Alex, I think the standard injectors are rated 195cc/mim @ 3Bar or approx 215 @ 3.8 Bar.

alexjc4

Yeah Bosch p/n 0-280-150-731 193.9cc/min @ 3bar 16ohm.

Where do you get the 215 from? Why wouldn't the flow be more proportional to pressure?

ras62

Its not that simple Alex. Bernouli's theorem explains the technicalities but the 215 figure isn't far off. I intalled a set of 'red devil" uprated injectors but it ran way rich at low revs and idle so I put the standard injectors back in. Will use the uprated ones come rebuild time...

Edit..figure at 3.8Bar is 220cc/min http://www.witchhunter.com/injectorcalc1.php

alexjc4

Good call, I'll go back and update the first page.

I found a calculator tool:
http://www.witchhunter.com/injectorcalc1.php
(Edit: you found the same one ras, great minds google a like)

Looks like a rule of thumb would be that you need to 4x pressure to double the flow. So estimate +25% pressure gives +12.5% flow. Which gives 218cc/min. I can buy that as some cigarette packet maths but that's tiny injector. Surprising how many claim to have seen 300bhp on them.

PS your "red devils" will run rich if the DME wasn't mapped account for the flow, the required fuel calculation (add probably latency) will be well off.

alexjc4

More on fuel injectors, the standard fit Bosch part no is listed for the 964 here:
http://www.cannell.co.uk/Bosch_Techn...rservparts.pdf
Interestingly same p/n also listed for the Ferrari 348 and Mondial

In terms of the power supported by the tiny standard 194cc injectors, no lesser authority than Geoffrey suggests ~300 and I'd take his word for it.

From the thread I referenced on the first page;
Although I also derived the 250cc/min at 3.8bar from that thread, again Geoffrey, and this looks iffy.
In terms of upgrades; Is the 993 injector a possibility? p/n 0-280-150-786 22.15# or 232.8cc/min @43.5psi/3bar

Can low impedance injectors be used with an appropriate resistor? I have low impedance Jecs 440cc and high impedance Bosch 550cc on the shelf, and high impedance Jecs 270cc I'm about to remove from a car (all are top feed). What are the physical requirements for an injector to be compatible? Edit: answered my own question I think, with the Jecs/Denso style ones, whilst the body and dimensions are basically bosch EV1 style, the sealing rings are different, so they won't work unfortunately. I've not seen them in the flesh but I assume the standard injectors are "Type C"

alexjc4

In terms of standard ignition maps, looking at http://www.911chips.com/ignition.htm it seems there is a 3D load vs rpm map for part throttle and a 2D map for WOT, is that right?

PhatPhlatSix - I have standard, steve wong and redtek chips at my disposal, I don't suppose we could load those into your copy of Pro2DME and compare the maps. Obviously the VEMS will use a proper single 3D map for ignition but it might be useful reference.