Ideas for Tunage

[aaron ford]

Okay guys I have a question. Could a tune be written to reduce the white smoke on cold startup? (It is an old truck and some of it's issues are developing issues of their own, but it's my toy.) The reason I ask this is that one morning I forgot to plug in my ICP after doing some other repair. To my amazement, the truck did not smoke at all. Not sure why and I have not tried to repeat it, but could a file be written so that idle is picked up and fuel is turned down?

A second thought I had is what about an 7 speed file? 1st, 1st lock, 2nd, 2nd lock, 3rd, 3rd lock, OD. Properly done this would keep the engine right in the sweet spot. Or would it?

Just thinking out loud,

Aaron

[cleatus12r]

I'm going to sit here for a while and decide how I want to write out a response to these two questions. I just woke up and my mind isn't exactly sharp just yet but I have great ideas running through my head.

Stay tuned.

[Power Hungry]

Since Cody hasn't apparently "sharpened up" yet... ... I'll give this a stab.

First, it's very easy to eliminate much of the cold-start smoke associated with older trucks. A mild increase in ICP and an additional 1-2 degrees of timing in the colder oil temps will usually clear that nonsense right up, especially the timing although, as you've seen, ICP can certainly help that issue out as well.

In regards to the shifting, what you described would be an ideal setup. The problem is that it's not terribly feasible because the transmission would be shifting in and out of gears and locking/unlocking the converter every time you so much as breathe on the throttle.

Years ago I worked on a calibration set that took all the converter lock functions out of the equation, making it basically a 4 speed, open converter transmission. I got the shift points lined up where I thought the felt good (having to overshoot a little considering where I'd intended to be bringing in the converter lockup) and then brought the converter strategies back in. I will tell you, it shifted like crap. With the converter unlocking between each gear it, would cause all sorts of crazy RPM fluctuations that just didn't feel right. It always had that feeling of not knowing what gear it wanted to be in.

Believe it or not, Ford actually did something that was not too far off from ideal with their '01 strategies. At light throttle, the converter doesn't lock until 3rd or 4th gear depending on how much throttle you're giving. At heavy throttle, the converter will lock in 2nd and stay locked through 4th in order to provide more direct power to the transmission and reduce heat buildup and ballooning of the converter. This is actually one of the more ideal setups. Later strategies ended up busying up the transmission and really made the shifting horrible.

Shifting is always a hard function to get nailed down because of the number of factors to take into consideration, including customer preferences. We do the best that we can but sometimes you just have to accept the limitations and settle for some middle ground.

[cleatus12r]

I have a good excuse for not replying earlier .



The torque converter used in the Powerstroke is designed simply to "save the transmission". In other words, it has a high stall speed and a very low torque multiplication factor. This allows the engine RPM to rise very high in relation to the actual input shaft speed. If you factor in the transmission gear ratios (which are absolutely stupid and useless in a 4-speed automatic) of 1st (2.71:1), 2nd (1.54:1), and 3rd (1:1), then it becomes apparent that the act of going from 1st locked to 2nd unlocked will actually cause an INCREASE of engine RPM during a shift....and a shift that causes a near absolute loss of drive wheel torque. The same would happen (and even moreso) during a 2nd locked to 3rd unlocked transition. The limited and closely spaced gear ratios in the E4OD and 4R100 make this a very undesirable mode of operation and once the torque converter is locked, it makes sense to keep it there.

The biggest problem I have noticed, especially when using the stock PMT2 calibration that my truck came with, is that the torque converter unlocks for a full 2.5-3 seconds during a 4-3 downshift while under load either forced or after a TCS (OD off button) push. It's ridiculous how much rear wheel torque is lost during this short time....and it's extremely annoying. The problem is compounded by an instant jump to 3200 RPM at 73 MPH....if you look at a dyno graph for a 7.3L, you'll see that 3200 RPM is useless. Good thing there are ways around it with different PCM codes and programming techniques.

I would be VERY hard to get the shift timing right while attempting to tune what you are describing. This is mostly due to the variable shift points that are encountered depending on acceleration rate and different accelerator pedal positions.

On the white smoke issue, my thoughts are that of Bill's. I would also assume that it is due to the slightly higher commanded injection pressure combined with the added cold start of injection that cleared up the white smoke. I will also point out that white smoke on startup can also be caused by low compression or an inoperative glow plug or two. But since it didn't smoke when the ICP sensor was unplugged, I don't think I'd blame any mechanical issues. The PCM will default to 725 (calculated by Injection Pressure Regulator duty cycle) at idle when the ICP sensor is unplugged. This is a bit higher than the 485 or so PSI that is commanded when the ICP sensor is functional.

[Power Hungry]

Originally Posted by cleatus12r

I have a good excuse for not replying earlier .

Yeah, yeah, yeah...

[cleatus12r]

Seriously. I was dismantling a '91 E-350 van for a donor engine, transmission, and wiring harness. I'll tell you now that pulling an engine and transmission out of a van in one piece is a mutha!

It's a 460 and E4OD for my '73 F-100. Turbo project? Probably.

I'll probably need an MDF for that one too.