delkat

iTrader: (2)

I'm running E85 on DW1300s. The car runs great in open loop with stable AFRs but when cruising in any gear under light or no load I can feel the car surging like someone's pulling lightly on the e-brake. When I feel the surge and look at the AFRs they are going very lean (19-21) for a second or two and then rich (11-12) for a second and then back to stoic. This pattern sporadically repeats every 5-7 seconds.

When I come to a stop sign the idle jumps around between 1000-1300rpm before gradually (5 seconds) settling down to 800.

Any ideas what's causing this?

Thanks

Golden

iTrader: (1)

Not sure. Logs would be helpful. Log everthing that has to do with injectors.

A miss fire can cause a quick very lean reading on an AFR gauge.

DeatschWerks

iTrader: (2)

Scaling could be a little off, and the ECU is fighting the injectors to maintain the AFRs in closed loop?

delkat

iTrader: (2)

I just got a new laptop (old one died) so I need to figure out how to re-load Evoscan.

Scaling is set at 713. Do you have any feedback on scaling from other users?

Golden

iTrader: (1)

You might want to post your latencies too.

delkat

iTrader: (2)

4.69 - 4.008
7.04 - 3.192
9.38 - 2.592
11.73 - 2.112
14.08 - 1.800
16.42 - 1.656
18.77 - 1.392

tephra

iTrader: (6)

what are your fuel trims telling you?

delkat

iTrader: (2)

Just got Evoscan re-loaded. I'm not up to speed on the LTFT and STFT tuning so I'll do some homework over the weekend. I did a search and there's a lot of material on the subject to sort through. Let me know if anyone has a favorite thread on the basics for this subject.

Thanks

tephra

iTrader: (6)

just post up your LTFT-Idle and LTFT-Cruise

if they are more than 5% (- or +) then you need to rescale/relatency your injectors

WHICH WILL ALSO MEAN YOU NEED TO RETUNE YOUR FUEL MAP

delkat

iTrader: (2)

So I did a couple of logs:

Idle -5.078, Cruise +8.593

Then drove around the block and logged while cruising:

Idle -2.343, Cruise +11.718

After a little research, I believe this means the ECU wants to add fuel at cruise and take away fuel at idle, right? I understand that adjusting latency values higher will give me longer pulsewidths effectively adding more fuel. Doing this will also increase the idle fuel more than the cruise fuel since the incremental IPW increase as a percentage of the IPW will be larger at idle. So the result of this would be to bring down my cruise trim but increase the negative idle trim by a larger amount.

I can also increase fuel by reducing the scaling so the ECU thinks the injectors are smaller and increases the IPWs accordingly. Does scaling compensate for the IPWs at different RPMs such that idle doesn't get a larger change by percentage as described above?

What to do when the trims are in opposite directions??

Mojito

iTrader: (1)

You need to drive for about 20 minutes with a constant speed to get correct cruise speed.


Is this also true if trims for WOT are disabled?

EVOlution561

iTrader: (13)

I would think the fuel trims are slightly off.

delkat

iTrader: (2)

My guess would be yes since you are globally changing IPWs with latency and scaling independent of any ECU trim compensation.

tephra

iTrader: (6)

mojito - yes its also true

delkat - yeah your fuel trims are off a bit - I would do the proper rescaling technique posted a few times here...

have you got a wideband to be able to retune your fuel map?

delkat

iTrader: (2)

Tephra,

Did you mean to post a linky??

I've read the techniques and they're not clear on how to handle a situation where you have the trims split negative idle and positive cruise. That's why I posted the questions above. I can understand that increasing latency and then adjusting scaling can solve a problem with positive idle and negative cruise since the latency will effect the idle more. But I'm assuming changing scaling effects both idle and cruise by the same percentage.

With this assumption, to fix my - idle and + cruise, I could do the opposite; decrease latency which would decrease idle more than the cruise and then increase scaling to bring the global fueling up for both idle and cruise.

I really don't like to follow "techniques" blindly without understanding what I'm doing.