E38 VVE Setup Guide

[swingtan]

I can see a few big issues with not setting up B1213 in a stock tune. Basically, just driving around in summer, the IAT's will get very warm, leaning out the mixture and causing the O2's to tell the ECM to add more fuel. This of course will increase the LTFT amounts to match. But when you give it a bit of a run on the open road and hit PE, the LTFT will add that fuel to the commanded and you'll end up with a very, very rich mixture. Maybe this is one reason why the stock tune end up so rich ( in addition to the VE table and MAF settings ).

The reason for correcting the AFR drift is really more to do with consistency rather than out right performance. For example, imagine you set up the VVE on a cold day with lots of open road driving. Then after setting it all up, a few weeks later the temp rises and you get caught in traffic, heat soaking the intake and the IAT's rise. If you were to "give it a boot full", the mixtures may be significantly leaner than commanded and the timing too great for that mixture. You'll end up with KR where previously you had none.

You could probably tune the KR out with the IAT timing table, but you would then be running much less timing than you could be, if the mixtures were correct.

Simon

[gmh308]

I can see a few big issues with not setting up B1213 in a stock tune. Basically, just driving around in summer, the IAT's will get very warm, leaning out the mixture and causing the O2's to tell the ECM to add more fuel. This of course will increase the LTFT amounts to match. But when you give it a bit of a run on the open road and hit PE, the LTFT will add that fuel to the commanded and you'll end up with a very, very rich mixture. Maybe this is one reason why the stock tune end up so rich ( in addition to the VE table and MAF settings ).

The reason for correcting the AFR drift is really more to do with consistency rather than out right performance. For example, imagine you set up the VVE on a cold day with lots of open road driving. Then after setting it all up, a few weeks later the temp rises and you get caught in traffic, heat soaking the intake and the IAT's rise. If you were to "give it a boot full", the mixtures may be significantly leaner than commanded and the timing too great for that mixture. You'll end up with KR where previously you had none.

You could probably tune the KR out with the IAT timing table, but you would then be running much less timing than you could be, if the mixtures were correct.

Simon

Great reasoning on that one Simon. Getting IAT AFR correct may also be helpful in preventing a tendency for thermal runaway on high temp days as the combustion temp gets higher and higher as the AFR rises, then some KR occurs as you point out and temps continue to rise....

mmmmm.....

[macca_779]

Hi Guys,

Thanks for the kind words and I'm glad a few are finding this useful. I've made another update to the guide......

To help with dialing in the VVE, there is now a section on calibrating the base injector flow rate with IAT. Many will know that as IAT goes up, the AFR's can tend to lean out, so you need to add more fuel to correct for this. the new section describes one method to help set up B1213, resulting in stable AFR's for all IAT's.

Simon.

Interesting method your using for the IAT factor Simon.. I never thought of doing it that way.

My method encompasses getting VE sorted at one temp average. I then perform the Auto VE process at a different time of day but don't apply it rather take an average of all the BEN's and the logged IATs in Excel. The averaged BEN's become the correction factor (invert it if its an E38) and the averaged IAT's are where the factor goes. The rest is linear filled to the original Auto VE average temp. I do it this way because I find heatsoak to give alternate results to actual temperature change which up here can be huge in the space of 24hrs.

[gmh308]

Interesting method your using for the IAT factor Simon.. I never thought of doing it that way.

My method encompasses getting VE sorted at one temp average. I then perform the Auto VE process at a different time of day but don't apply it rather take an average of all the BEN's and the logged IATs in Excel. The averaged BEN's become the correction factor (invert it if its an E38) and the averaged IAT's are where the factor goes. The rest is linear filled to the original Auto VE average temp. I do it this way because I find heatsoak to give alternate results to actual temperature change which up here can be huge in the space of 24hrs.

Macca, what IAT temps do you see up there with heatsoak in the red centre?

[swingtan]

Hey Macca, that's an interesting way of doing it as well. I can see your reasoning and this would work well with the IAT - VE table for the LS1. With the E38, we only really get the INJ vs IAT table to help in this area so have to work with what we have. I had 2 main reasons for doing the correction in this particular way...

• By leaving the car idling and allowing the heat soak to increase IAT, nearly all other engine factors that can alter AFR are kept constant. This means any AFR drift is most likely to be caused by IAT and from other things like throttle transitions etc.
• It is very quick and very accurate. Using this technique you can dial in the INJ vs IAT table in a single session lasting 30 min.

Of course, it doesn't make up for real world driving data, but is probably not far off in the end result.

Simon.

[macca_779]

Macca, what IAT temps do you see up there with heatsoak in the red centre?

Highest I've seen is in the high 60c range on my car sitting idleing for an extended time. While driving approx 5c above ambient is normal so 50s aren't uncommon. I have an OTRCAI that does return back to realistic values quite quickly. On a Magnacharger LS1 I tuned I would see in the high 90's while WOT. The crappy water to air intercooler that PWR supplies is the main culprit there though.

[GMPX]

Simon, could you please add in to your tutorial to make sure the MAP units in the VVE tables and the Zone set up tables are the same units, i.e kPa or PSI, not a mix. Probably somewhere on page 7 would be great.

Thanks,
Ross

[swingtan]

Hi Ross,

I've added that in and placed it on P10, where I first describe altering the zone boundaries. I thought that as people would be looking at the table then, it would be a good place to get them to check. I used a different PDF converter which increased the size a little, but it's still well under 1MB.

Download here -
http://download.efilive.com/Tutorial...20Tutorial.pdf

Simon

[alian]

Highest I've seen is in the high 60c range on my car sitting idleing for an extended time. While driving approx 5c above ambient is normal so 50s aren't uncommon. I have an OTRCAI that does return back to realistic values quite quickly. On a Magnacharger LS1 I tuned I would see in the high 90's while WOT. The crappy water to air intercooler that PWR supplies is the main culprit there though.

Macca. Bit new to this but cant you run an intercooler as well as the heat exchange set up they come with.Not sure about the PWR but was looking at a Harrop the other day.
Cheers Ian

[macca_779]

Macca. Bit new to this but cant you run an intercooler as well as the heat exchange set up they come with.Not sure about the PWR but was looking at a Harrop the other day.
Cheers Ian

Don't think so mate. Due to them being a top mount Blower your forced to use a remote water heat exchanger setup. Perhaps a larger front mount and a better pump than the crappy electric one supplied would improve the efficiency but there isn't much I imagine you can do about the blower side of things.
If I was going down the FI route I'd go Turbo's or perhaps a Procharger. The temp increase over ambient is bugger all with a good Air/Air Intercooler