Stroked LS2 SDOL tune T56 car E40 pcm - bog on hard shift at redline log attached

Hi all.

I have an inconsistent lean bog on hard shifts since I switched over to SD OL.

If I shift 2-3 or 3-4 hard up near red line I dump the clutch back out and mash the gas pedal and it feels like I mucked up the gear change. It feels like the gas pedal does nothing and then the car jumps back to life. It is not a long delay, but enough that feels like my feet were totally out of sync on the gear change.

Other times I bang the gear and it hits hard and keeps pulling.

I managed to FINALLY catch this on a log. It appears there is a significant delay for the injectors to begin spraying fuel again despite the gas pedal going to WOT, the throttle body going to WOT, and MAP showing WOT pressures.

I'm pretty unsure where to go from here. VE isn't perfect and I'm running a bit fat, but nothing is too awful I don't think.

The bog happens at 11:07 in the attached log.

Attachment 65416Attachment 65417

Second question - since going SDOL I haven't been able to make the idle change off 800. I have it commanding 675 rpm when warmed up but it never deviates from 800. What's the deal with that? When closed loop it idled wherever I set it.

When looking at the bog issue the injector pulse width is very telling. There is about 3/10 of a second of delay on the bad shift from when I began going back on the trottle to when it shows it actually delivering the proper amount of fuel.

For speed density you do need the 3 MAF dtc's set to first error, just uncheck the SES box. I'd also change the fail high to 2hz and the low fail to 1hz, sometimes they don't like 0hz. Remove all your MAF related channels when tuning SD, they could mess with the data you are trying to gather.

I'd be curious if the ETC TPS MAX table in "TM" is a cause for the delay, that table does have a roll in how much throttle can be given.

I will try 2 and 1 hz on the maf. 0 0 is what the common SD guide says to do. It has always perplexed me that even after failing the maf it does read. My IAT sensor is in my maf but soon I will be removing it all together. The scanner confirms that it is in open loop.

I do have the DTCs enabled but set to no light.

I'm not sure about the throttle pedal I'll have to read into that some. I recall that trying to tune the gas pedal curve is a good way to muck things up royally.

ETC TPS MAX only is referenced when traction control is on - which I don't have. The car is a swapped RX7 with no BCM.

Quote:

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Originally Posted by dankmac

ETC TPS MAX only is referenced when traction control is on - which I don't have. The car is a swapped RX7 with no BCM.

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Then you might want to kill all traction control in the tune, so it doesn't try to cause any other underlying problems...

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Well I've figured out how to reliably make it bog. I need to lift all the way off the gas between shifts.

Attached is a log with 3 pulls. The last two bogged hard. It shows about 4 tenths of a second of delay before the injectors really catch up with WOT.

I leaned out the VE upstairs since I was 11.0-11.5 above 5k. I didn't realize I had it so rich. It made no difference on the bog issue.

I really am a little stumped here...

Quote:

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Originally Posted by GHuggins

Then you might want to kill all traction control in the tune, so it doesn't try to cause any other underlying problems...

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Sure I'll do that. I thought I had tbh but I just updated to the 3.4 suite vs my older 2.x setup and I think some things changed.

Transient Fueling - Evap and Impact - Multiply the 80kpa row by 1.1 / Multiply the 90kpa row by 1.15 / Multiply the 100kpa row by 1.2

See if it changes at all - with it only happening when you completely let your foot off the gas pedal then get back into it is pointing to transient fueling...

Yep, transient fueling issue I'd bet. Mine used to do almost the same thing, it was worst on fast hard shifts

If you speed up the narrowband O2 sensors I bet you'll see it on those pretty easily

Quote:

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Originally Posted by GHuggins

Transient Fueling - Evap and Impact - Multiply the 80kpa row by 1.1 / Multiply the 90kpa row by 1.15 / Multiply the 100kpa row by 1.2

See if it changes at all - with it only happening when you completely let your foot off the gas pedal then get back into it is pointing to transient fueling...

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Thanks for the help. This all makes sense I just never knew how to tune transient fuel.

I have not touched transient fuel in the tune. It is the same as a stock '06 GTO.

My engine is a 404 cube LS2, stock LS3 top end, 226/242 cam, and exhaust manifolds makes about 465/450 rwhp/tq.

Should the transient fuel be increased across the board since the engine is bigger?

Having it in SD screws with how some of the transient fueling stuff is calculated, or at least that's what my research on it a year or so ago came up with.

I have a chuggle with the MAF because of a mixture of my cam causing reversion and my intake tube is being very far from optimal. It is super short with the TB and a curve right next to the MAF in a 4" diameter. I opted to just ditch the MAF and go SD and have been very happy except this one thing.

I also much prefer the driving feel of speed density the gas pedal is much more responsive not having to wait for signal from the MAF.

Is there any way to dial it in properly or do you just keep fudging until the car drives well?

I will soon have access to a load bearing dyno to get my VE dialed in - so that will at least allow me to isolate the VE table from being an issue.

Pretty much fudge until it drives well. On E38's there is a "manifold volume" value that you can change that makes it easier, but we don't have that on E40's. I requested access to it and HPT told me it didn't exist on E40's.

Give what Greg said to do a try and see if it changes anything.. worse case you might have to go even more than he recommended

To me it appears like the car is late adding fuel on the shift. Not that it isn't adding enough fuel, but that it is lagging. In some cases it is 4 tenths of a second late to getting back to WOT levels of injector flow. Other times it is adding fuel as I'm going back down on the throttle and gets back to full flow quickly and doesn't bog.

I just did about an hour of reading on transient fuel tuning and tbh I'm not really looking forward to it hah!

I think I need to just live with the issue happening here and there until I take the time to get my VE table really close and not just safe close...then start messing with transient fuel stuff.

Or maybe I just shouldn't lift on my shifts :p

Transient fueling isn't hard or bad to dial in - just make the rough adjustments and see how it goes... Don't adjust the whole table as it will mess with idle and cruise afr's - adjust the kpa rows - do not adjust individual cells or ivt columns independently... That will save you lots of headaches... Transient fueling is how quickly it gets added back in just to help simplify it for you... There are also pe tables for this, but if yours is open loop - I don't think they'll make much difference...

Thanks. The changes you suggested to transient fuel still show a bog but it may require even more of a change. When I can I'll throw some more at it.

Still show a bog, but is it any better?

It was a minor change if any. It still does it consistently.

When I had a chance I was going to make another large change as you recommended last time. At some point I'd expect to see the change show something.