7427 install, first impressions

[JeepsAndGuns]

Well did some more tweaking today and had some good results, so I figured I would just go ahead and keep adding to this thread.

I touched on this a little bit when I got my vss working and dfco started working. When it would come out of dfco, it would jolt the engine when it cut the fuel back on. Basicly it would be like you just lightly bliped the throttle. At first it wasnt annoying, but it kept on untill it did! After a little while it became VERY annoying. Would do it at about 1500 rpm, and I had not gotten to the point when I downshit. (remember, I am running a manual trans)
Well I find this parameter in scalers under "AE parameters" called "post DFCO AE pulse" with the discription that it provides a AE pulse when exiting dfco if no tps increase. I thought that kinda odd. Why would it want to add more fuel when kicking the fuel back on if the throttle did not get re opened. I did drop it straight to zero right away, I took it in steps. The jolt got lighter the lower I went untill i eventually set it to zero. Now it simply cut the fuel back on post dfco, but didnt add any extra AE. The jolt was a lot less that it was, but there was still a jolt (like you bliped the throttle) when it turned the fuel back on.
Now just to keep from confusion, there is still a parameter for a AE pule when exiting dfco if you DO open the throttle. I forgot exactly where it is. But that one makes sense. Your in dfco slowing down and then need to accel again (like slowing down for another car making a turn, then you take off again) I left that setting stock, as it does just fine if I hit the gas again when in dfco.
Now back to the jolt when it kicks the fuel back on. I thought about it and where it kicks it back on at 1500 rpm, it would be nicer if it did it at a lower rpm. I did a little more carefull looking at all the avalable parameters in my xdf, and found something I thought would be usefull. Its under tables and is under dfco parameters and is labeled " minimum dfco rpm vs. temp. In a nutshell its basicly what I was looking for! Its what rpm it cuts the fuel back on post dfco, and it splits it up into diffrent tepatures. I changed it to 1000 rpm for most closed loop temps, and a little highr for colder temps. Saved it, burnt a chip and took it for a drive. Sucess! I now no longer have the jolt when in dfco, because now it doesnt cut the fuel back on while I am still slowing down! It now does the jolt/blip when I push in the clutch to downshift. I watched the rpms and it doesnt drop lower than it should, the fuel cutting back on catches it, and it still does that blip. I now like it, because its like your bliping the throttle in between downshifts. I actually can kinda time it just right and use that blip when double clutching and not even have to touch the throttle. Kinda a added bonus...lol
BUT not all was well. Because I lowered the min rpm, I now made it to where if I was at parking lot/driveway speeds, it will go into dfco! Say like you pull out, drive a few yards while still in first gear and let off again, it went into dfco real quick and then the jolt of cutting the fuel back on, made a interesting combanation, and not a good one. It was like hitting the brakes and the gas real quick.
So some more digging around in the xdf, I find the parameters in scalers under "dfco parameters" and found the two parameters "minimum MPH to enter dfco" and "MPH to disable dfco"
The first one was set to 10 mph. I doubled it to 20 mph. I figured there was no need to go into dfco under 20. I then changed the disable dfco from 7 mph to 15 mph. That way, I have to be going 20 mph or faster for dfco to come on, and under 15mph, dfco is completely disabled.
Saved, burnt a chip and test drive. I now have full sucess! I now have no more jolt when slowing down, have a nice blip in the throttle between downshifts I can use when double clutching (that was completely unexpected, and just kinda a added bonus side effect), and no more dfco at too slow of a speed.

Hopefully all these little updates may help another manual trans 7427 user one day.

[one92rs]

not to add a pointless post to this thread. but i posted needing info on a 746 to 427 swap in my camaro and a 60e swap from the 700. i cannot tune it myself so i will get a chip. but i needed to know all the info in this thread. now i will be watching closely how all this goes. also can someone in here tell me where to get new plugs for the 4127 ecm.

[dave w]

not to add a pointless post to this thread. but i posted needing info on a 746 to 427 swap in my camaro and a 60e swap from the 700. i cannot tune it myself so i will get a chip. but i needed to know all the info in this thread. now i will be watching closely how all this goes. also can someone in here tell me where to get new plugs for the 4127 ecm.

Mouser Electronics is where I get my ECM connectors from.

http://www.mouser.com/Search/Product...ey829-12110115

http://www.mouser.com/Search/Product...ey829-12110113

dave w

[one92rs]

thank you very much. i will get those ordered.

[1leg]

For TH400 applications that had 1228747 ECM's, I've installed 1973 ~ 1986 TH400 kick down switches on the accelerator pedal, that are wired to supply Ground to the kick down relay. dave w

Dave do you have part numbers and pictures you could share on this. I'm might have a 427 soon to start a swap on the suburban.

[1project2many]

The DFCO pulses are helpful to prevent a "bump" when going from DFCO to normal fuel mode due to the manifold drying out and the delay time to get fuel from the injector to the chamber.

Now that you've tried DFCO that would enable even at minor coastdown, you might appreciate the idea of using brake switch input to force DFCO at any speed. It would save fuel and help save the brakes if driving in traffic.

[93V8S10]

Now that you've tried DFCO that would enable even at minor coastdown, you might appreciate the idea of using brake switch input to force DFCO at any speed. It would save fuel and help save the brakes if driving in traffic.

Got me interested!

[dave w]

Dave do you have part numbers and pictures you could share on this. I'm might have a 427 soon to start a swap on the suburban.

The Ebay auction has the part number and pictures.

http://www.ebay.com/itm/Corvette-NOS...item2c622d86f2

I made a 3/8" cylindrical sleeve to go around plunger, because the gas pedal arm does not push the plunger far enough.

dave w

[EagleMark]

Darn that's an expensive switch. Wonder if a regular brake switch used for 700R4 to unlock converter would be chaeper? Anything would be cheaper than NOS Corvette parts...

Jeepsandguns that bin was superceded, so what your tuning may have been the issue they changed it. The other 7.4L manual bin 93V8S10 has may be better? It was not superceded.

Gregscam (can you post that bin) is also getting me a 5.7L Manual bin from a 16197427 but I think it runs $31. I may redo this one for my kids truck or at least compare them all.

93V8S10 can you post up that bin?

[gregs78cam]

I posted it in my for sale thread, but sure here ya go. It shows at L4008 as $0D.

[EagleMark]

BCC result page!



BCC used in 1995. (Scroll down for more info)






BCC= BPRW0651

Scan id= 0505

Part number= 16220651



Release date= 02/04/95

Engine size= 5.7

Trans Type= all/no listing



ECM/PCM: ECM #16156930


Used in trucks:


GMC

Possibly used in:


G20 VAN,2WD,3/4 TON

G25 VAN,2WD,3/4 TON





Options:



With GT4 AXLE, REAR, 3.73 RATIO




With L05 5.7L GAS 8 CYL (5.7K) V8 TBI




With NA5 FEDERAL REQUIREMENTS

[JeepsAndGuns]

Jeepsandguns that bin was superceded, so what your tuning may have been the issue they changed it. The other 7.4L manual bin 93V8S10 has may be better? It was not superceded.

What was it superceded to? BHDC?
I have changed so many things, it will be hard to transfer everything over. But I may try it one day when I am bored.


I thought the brake switch was just for the TCC?
I disabled DFCO below 20mph, its not really needed at speeds slower than that, and like mentioned above, had very bad parking lot manners. The way I have it set now, it pretty much comes on anytime I let off the gas, and works great! I dont really see the need for the brake switch, unless theres more to it.

[EagleMark]

What was it superceded to? BHDC?
I have changed so many things, it will be hard to transfer everything over. But I may try it one day when I am bored.


I thought the brake switch was just for the TCC?
I disabled DFCO below 20mph, its not really needed at speeds slower than that, and like mentioned above, had very bad parking lot manners. The way I have it set now, it pretty much comes on anytime I let off the gas, and works great! I dont really see the need for the brake switch, unless theres more to it.

The bin we started with BMHK when checked on CalData was superceded to BPRJ a bin no one has...

Brake switch was just a sugestion to daves commnet, it was a hijack of your thread, your right it's to disengage TCC.

[dave w]

What was it superceded to? BHDC?
I have changed so many things, it will be hard to transfer everything over. But I may try it one day when I am bored.


I thought the brake switch was just for the TCC?
I disabled DFCO below 20mph, its not really needed at speeds slower than that, and like mentioned above, had very bad parking lot manners. The way I have it set now, it pretty much comes on anytime I let off the gas, and works great! I dont really see the need for the brake switch, unless theres more to it.

Brake Switch? I was thinking the question was for a TH400 Kick Down Switch?

dave w

[EagleMark]

I was suggesting useing a TCC brake switch (cheap) to a NOS corvette part (expensive), it's just a switch... $75?