Trying to get my recent turbo/MSPNP project on the road, and I'm enjoying learning the secrets of megasquirt.
Right now, I'm trying to figure out dead time. I've got new green Bosch 42's, which the internet says have a dead time of .7628
I'm working off the MSPNP Mustang base tune from DIYAutotune, with an updated req. fuel set at 9.4, and .763 set for the dead time under injector characteristics.
I've adjusted the VE table at idle and it idles beautifully at 900 rpm, 14.7 AFR, and a pulsewidth of 1.5, but I had a suspicion that I was using an incorrect dead time. To check this, while the motor was idling, I changed from four squirts to two squirts, and the AFR instantly went pig rich (below 10), the pulsewidth jumped to over 4 and the engine ran like crap. Changed back to 4 squirts and she purrs again.
So my dead time appears to be way off, and I'm a little mixed up about which way to move it and how much. Anyone care to lend some advice?
As I understand it, the AFR and p/w shouldn't change when I change from 4 squirts to 2, IF the dead time is set correctly?
__________________
Trying to get a good dead time for Bosch 42's and MSPNP
Moderators: jsmcortina, muythaibxr
Trying to get a good dead time for Bosch 42's and MSPNP
1991 Volvo 740 wagon, 306 C.I. Windsor V8/5 speed T5, twin Comp CT2 5062 turbos, twin 39mm Precision gates, Tial BOV, Garrett IC, 42 lb Bosch injectors, Walbro 255, AEM wideband, MSPNP from DIYAutotune
Re: Trying to get a good dead time for Bosch 42's and MSPNP
P/W will always change going from 4 to 2, but afr shouldn't change.
On another note did you cycle the ignition between the change of 4 to 2? If you didn't then the test is invalid. If you don't restart the MS between the switch, the fuel calculations get screwed up and it will do weird things.
On another note did you cycle the ignition between the change of 4 to 2? If you didn't then the test is invalid. If you don't restart the MS between the switch, the fuel calculations get screwed up and it will do weird things.
MS3+X on 73 Karmann Ghia ignition only with LS2 truck coils firing in sequential, fuel next.
2333(103*70) Type 4 with DTM also sitting in living room just need exhaust.
2333(103*70) Type 4 with DTM also sitting in living room just need exhaust.
-
mr_minnis
- Experienced MS/Extra'er
- Posts: 162
- Joined: Thu Mar 28, 2013 12:05 pm
- Location: Near Wichita Kansas
Re: Trying to get a good dead time for Bosch 42's and MSPNP
The best way to get the most accurate dead time is by following this thread: This takes into account the wring and the ecu circuits.
http://www.msextra.com/forums/viewtopic ... 34&t=54260
However I wasn't able to do this on the engine. I have an efi ford 302. Various injectors kept popping out from the rail. It was frustrating watching gas roll off the intake and onto the garage floor.
The next way would do what you are doing. alternating between 4 and 2 squirts, watching the AFR. The value you found online is a good starting point. Keep in mind that some of these don't include the closing time. Be sure to not test when MAT and CLT corrections are in effect. It will mess testing up.
The next way would be send and injector in to get it tested. Some injector shops can test the injector and get you the values. However, it won't be the same on your wiring. There is a shop in Oklahoma that can do it. They quoted me $70.00. Not a bad deal if you can't find any information online.
The last way would be purchase the injectors from a vendor who can supply the dead time value.
Personally I would rather test the ones I have because it is cheaper.
Some other things to keep in mind:
The default value (.9 to 1) isn't to far off all things considered.
The nice thing about the VE table is it brings everything together. If your values are a little low for dead time the ve table will be bigger. You want to be as close as you reasonably can, just don't stress out over being 100%.
If you are running large injectors for the engine size, dead time is crucial to get the small pulsewidths you may need.
http://www.msextra.com/forums/viewtopic ... 34&t=54260
However I wasn't able to do this on the engine. I have an efi ford 302. Various injectors kept popping out from the rail. It was frustrating watching gas roll off the intake and onto the garage floor.
The next way would do what you are doing. alternating between 4 and 2 squirts, watching the AFR. The value you found online is a good starting point. Keep in mind that some of these don't include the closing time. Be sure to not test when MAT and CLT corrections are in effect. It will mess testing up.
The next way would be send and injector in to get it tested. Some injector shops can test the injector and get you the values. However, it won't be the same on your wiring. There is a shop in Oklahoma that can do it. They quoted me $70.00. Not a bad deal if you can't find any information online.
The last way would be purchase the injectors from a vendor who can supply the dead time value.
Personally I would rather test the ones I have because it is cheaper.
Some other things to keep in mind:
The default value (.9 to 1) isn't to far off all things considered.
The nice thing about the VE table is it brings everything together. If your values are a little low for dead time the ve table will be bigger. You want to be as close as you reasonably can, just don't stress out over being 100%.
If you are running large injectors for the engine size, dead time is crucial to get the small pulsewidths you may need.
88 Stang LX Vert. 3.73s and MS3x, D585 Coils AEM EPM
Re: Trying to get a good dead time for Bosch 42's and MSPNP
What is the name of the shop in Oklahoma you are talking about???
Re: Trying to get a good dead time for Bosch 42's and MSPNP
FWIW my first tests with MS2 gave a dead time of .570 at 13.2V with the Bosch 558's (or Ford MS green tops)