944 Turbo VEMS Installation and Setup

[944Turbo]

Nice write up, thanks!

 

[blade7]

The lambda based tuning does pose a question about how close the Lindsey/Rogue/Vitesse maps are ? I'd expect they have to be on the rich side on boost for safety. What's the target AFR on boost with VEMS ?

Yup - that was a key point for me, every other MAF setup just said "Let's look at what's going in, reference that to the internal map and do whatever corresponds to that input" - the VEMS unit also looks at what's going out via the lambda probe and is smart enough to change its parameters to suit.

My injectors are rated 55lb at 3.0bar - if my adjustable FPR is set to 3.1 bar I would be overfuelling with a different aftermarket setup, the VEMS software knows that I'm not hitting my lambda target and running too rich and compensates accordingly - clever penguins!

Here's the Lambda Table:

As you can see here that at 220kpa and above (17.4psi) the lambda is 0.77 which equates to about 11.5 AFR using the following table:

However, if you wanted to play you just click a cell and edit it (don't forget to Burn it though) - you can change the pressures on the X axis and the rpm on the Y axis by selecting them and editing them in the same fashion too:

Did you consider adding a EGT sensor too ?

 

[944 man]

I was going to suggest his to you, as a gauge to keep. EGT is something to keep your eye on but Im not sure that the ECU can act on the value supplied? Massive retardation over a preset would be handy though.

Ive been meaning to ask you David: does it have a 'Knock-Link'-like feature whereby a warning tell-tale can be illuminated when detonation is detected?

 

[PhilKent]

Excellent write up David. I've not started on mine as yet, but hoping to this week... I'll let you know how I get on, but I'll be re-reading this as I get on with it...

 

[Eldavo]

I've now enabled boost control so am working through that, also tweaked req_fuel settings ever so slightly and seeing a rock solid idle now With the right cold start enrichment.

Will update this week.

 

[blade7]

I've now enabled boost control so am working through that, also tweaked req_fuel settings ever so slightly and seeing a rock solid idle now With the right cold start enrichment.

Will update this week.

Obviously VEMS boost control is much more efficient, but how long would it take to turn the boost down on a boiling hot day ? A MBC is crude but it's takes a couple of seconds to twist that MBC knob.

 

[Eldavo]

Why would I want to turn the boost down on a boiling hot day when the chances are that it's slightly down due to air temps anyway?

The VEMS boost control is an active feedback loop system, if the usual duty cycle isn't hitting the target boost due to warmer weather then it will adjust the duty cycle automatically until it is at target. Whilst keeping overboost protection in the form of a fuel cut.

 

[blade7]

Why would I want to turn the boost down on a boiling hot day when the chances are that it's slightly down due to air temps anyway?

Because in my 30 odd years of running modified turbo cars I've found inlet air temp to be a factor in how much boost I could run safely. A hot summer day and a heat soaked intercooler is a different prospect to the open road on cold winter mornings. I'd like to turn boost down if I ever used my car in slippery conditions too.

 

[Eldavo]

There is a setting in the boost control menu for reducing boost by a given amount for rising IATs over a certain threshold along with an overboost fuel cut setting.

 

[blade7]

Thanks for the update.

 

[Eldavo]

I had hoped to be further along with the on-road tuning but the incessant rain and foot to the floor 18psi boosting don't make for happy bedfellows.

Might be on the Dyno this Saturday morning with a bit of luck.

 

[blade7]

Might be on the Dyno this Saturday morning

You seem to have a good understanding for setting it up using the Autotune on the road, will there be any benefit from putting it on the rollers ?

 

[Eldavo]

Fun and games, nice to get some numbers and curves.

May also be putting some of the boost control into play - I have it so that the Apexi and the VEMS are Boost installed, just swap two hoses and click a couple of buttons to go from one to the other.

 

[blade7]

Will be interesting to see how the VEMS and Apexi boost control compare.

 

[TonyKart]

great write up, following with interest

 

[Eldavo]

I was going to suggest his to you, as a gauge to keep. EGT is something to keep your eye on but Im not sure that the ECU can act on the value supplied? Massive retardation over a preset would be handy though.

Ive been meaning to ask you David: does it have a 'Knock-Link'-like feature whereby a warning tell-tale can be illuminated when detonation is detected?

I believe that a knock sensor and an EGT sensor are available- there are settings in the software for ITTT with regards to EGT inputs.

 

[Eldavo]

Will be interesting to see how the VEMS and Apexi boost control compare.

I never enabled the feedback function on the Apexi, I just set duty by rpm and tweaked it to maintain a consistent 1.25 kg/cm3. The VEMS has the ability to enter defined numbers for P, I and D so that boost control should be far mor intelligent and consistent.

I was was having a sensor error above 5k rpm on the dyno but have picked up a genuine Bosch sensor today rather than an OEM one so should hopefully sort that out. Jamie at Evotune in Durham was fantastic, looked over all the maps and tables that Peep had populated and nodded sagely while saying things that I didn't fully understand. The upshot was that he was happy with the tuning side, especially the fuelling and lambda tables - this was born out by the limited time we spent on the dyno, comparing the results with previous runs. We spent quite a lot of time ogling his Nissan GTR too, road legal (with a change of wheels and tyres), with full dashboard and aircon as well as the small matter of 1350 bhp (IIRC) and the current European 1/4 mile holder at a smidge over 8secs!!!

Running an MBC saw AFRs like this (wheel horsepower):

A switch to the Apexi produced the following (annoyingly the scale is different):

I didn't get the printout from the weekend as we couldn't complete a run BUT AFRs were rock solid at 11.7 under full load and boost was coming in slightly earlier. Whilst we didn't do a peak power run the data was overlaid with the previous visit's runs and there was a noticeable improvement on the graph.

Interstingly, my friend's 944 Turbo Cab with 100k less miles on the clock, with Lindsey MBC, DPW, chips and 3bar FPR - produced a graph almost identical to my 2013 one - albeit 25bhp down on my crank HP With the same mods. He's going to fit a Lindsey adjustable FPR and have it leaned out a little on the dyno as it is obvious that the Lindsey/Promax chips run very rich for safety.

The only thing that Jamie wanted to change slightly was a little more spark advance at higher rpm/loads. He was very happy with the results of the Autotune feature although did admit that he could make a few tweaks but nothing major and not worth doing unless I was going there anyway. Given I seem to go back there every 2 years he suggested I fit a new Turbo over winter 2018 and then drop back in 2019 for my biannual tuning

 

[blade7]

I think you're pissing into the wind without a bigger Turbo....

 

[Eldavo]

I think you're ****ing into the wind without a bigger Turbo....

I agree - that brings a whole host of other questions/issues/specifications and hiding the box from the wife too!

 

[PhilKent]

Luckily the turbo is so well hidden in the car she'll never see it! You've got everything else sorted, just make sure you get the 3" downpipe while you're at it. 400HP here we come! (Obviously not a patch on an S2, but we can dream can't we).