Hello All,
I have just finished the instalation of a TPI system/MS V2.2 on my 72 Chevelle, but i keep struggeling with it stalling out when I shift from Park or Neutral to Drive or Reverse. The engine has a fairly bumpy cam (Comp 270) and ported heads and headers, and has good compression on all cylinders. With the quadrajet, this never occured.
I checked out the datalog file (attached), and could not identify what is causing the problem. The only indication is a drop in RPM from 1100 to 200. Any suggestions at this point would be helpful. Thanks in advance,
David
Stalls when shifting to drive/reverse
Forum rules
Forum rules
Read the manual to see if your question is answered there before posting. If you have questions about MS1/Extra or MS2/Extra or other non-B&G code configuration or tuning, please post them at http://www.msextra.com The full forum rules are here: Forum Rules, be sure to read them all regularly.
Forum rules
Read the manual to see if your question is answered there before posting. If you have questions about MS1/Extra or MS2/Extra or other non-B&G code configuration or tuning, please post them at http://www.msextra.com The full forum rules are here: Forum Rules, be sure to read them all regularly.
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Bernard Fife
- Super Squirter
- Posts: 1009
- Joined: Mon Feb 16, 2004 3:15 pm
notop46,
I wasn't able to open your datalog. However, some general comments are:
- stalling when shifting to drive is fairly common at first when tuning an auto car,
- the stalling is usually caused by the engine speed dropping and the MAP rising as the transmission slips into gear,
- this means your operating point on the VE table (and spark ttable, if applicable) moves as well, so you need to:
* tune that spot as well as possible. You should tune the engine in drive (not just park/neutral) while sitting in the driveway to get that point as efficient as possible (aim to get the minimum MAP kPa at your chosen 'in-gear' idle speed),
* if you are also controlling ignition timing, add a few degrees of advance at engine speeds below idle - this helps stabilize the idle quite a bit,
* make sure the surrounding spots on the VE table are relatively smooth, and there's a smooth transition in the VE entries from the 'in-gear' and 'neutral' idle kPa/rpm,
* make sure that the accel enrichment is not being invoked by any MAPdot accel enrichment you have enabled (you might have to raise the MAPdot threshold),
* while sorting this out, it often helps to raise the idle rpm by about 200 rpm adjusting the throttle stop on the throttle body. As you get the tune optimized, you can reduce the idle speed.
Lance.
I wasn't able to open your datalog. However, some general comments are:
- stalling when shifting to drive is fairly common at first when tuning an auto car,
- the stalling is usually caused by the engine speed dropping and the MAP rising as the transmission slips into gear,
- this means your operating point on the VE table (and spark ttable, if applicable) moves as well, so you need to:
* tune that spot as well as possible. You should tune the engine in drive (not just park/neutral) while sitting in the driveway to get that point as efficient as possible (aim to get the minimum MAP kPa at your chosen 'in-gear' idle speed),
* if you are also controlling ignition timing, add a few degrees of advance at engine speeds below idle - this helps stabilize the idle quite a bit,
* make sure the surrounding spots on the VE table are relatively smooth, and there's a smooth transition in the VE entries from the 'in-gear' and 'neutral' idle kPa/rpm,
* make sure that the accel enrichment is not being invoked by any MAPdot accel enrichment you have enabled (you might have to raise the MAPdot threshold),
* while sorting this out, it often helps to raise the idle rpm by about 200 rpm adjusting the throttle stop on the throttle body. As you get the tune optimized, you can reduce the idle speed.
Lance.
I had a similar problem with my 383 TBI setup, it has cam that never liked to idle bellow 900 RPMs. Even with the idle high it would stall going from park to drive. I ended up richening up the low rpm, high load (upper left) area of the VE table quite a bit. I also tuned the low RPM parts of the table by loading the torque convertor. By holding the brake and giving it a little bit of throttle while tuning the fuel table.
Jeff in San Diego
What is MAPdot accel enrichment
Lance,
Thank you for the reply. Next chance I get, I will try the suggestions that you recommended. One that I do not yet understand is the MAPdot accel enrichment. Where can I find this enrichment and how does it function?
Thank you again,
David
Thank you for the reply. Next chance I get, I will try the suggestions that you recommended. One that I do not yet understand is the MAPdot accel enrichment. Where can I find this enrichment and how does it function?
Thank you again,
David
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Bernard Fife
- Super Squirter
- Posts: 1009
- Joined: Mon Feb 16, 2004 3:15 pm
David,
MAPdot accel enrichment is accel enrichment that is based on the change in manifold vacuum (aka. pressure). When you stomp the throttle, the TPS goes from 0 to 100%, but the MAP also goes from somewhere around 40 kPa to 100kPa. So either can be used for accel enrichment. However, for many engines, there are low speeds during which the increase in throttle doesn't increase the MAP and so accel enrichment is not needed.
For example, on my engine, at 2000 rpm, the MAP reaches 100 kPa at just 20% throttle. So if I'm already at 20% throttle, and opening it the remaining 80% causes no additional air to flow, and so the TPS accel enrichment is a bit 'bogus'. The MAPdot accel is not as easily fooled by this situation.
On the other hand, the MAP signal may have more variation in it than TPS, and as a result the threshold may have to be too high at slower throttle openings, so TPSdot accel enrichment is helpful in that siutuation. In my car I use 66% MAPdot/33% TPSdot accel enrich.
MAPdot accel enrichment is not implemented in the standard MS-I code, but it is available in both MSnS-E code and MS-II.
Lance.
MAPdot accel enrichment is accel enrichment that is based on the change in manifold vacuum (aka. pressure). When you stomp the throttle, the TPS goes from 0 to 100%, but the MAP also goes from somewhere around 40 kPa to 100kPa. So either can be used for accel enrichment. However, for many engines, there are low speeds during which the increase in throttle doesn't increase the MAP and so accel enrichment is not needed.
For example, on my engine, at 2000 rpm, the MAP reaches 100 kPa at just 20% throttle. So if I'm already at 20% throttle, and opening it the remaining 80% causes no additional air to flow, and so the TPS accel enrichment is a bit 'bogus'. The MAPdot accel is not as easily fooled by this situation.
On the other hand, the MAP signal may have more variation in it than TPS, and as a result the threshold may have to be too high at slower throttle openings, so TPSdot accel enrichment is helpful in that siutuation. In my car I use 66% MAPdot/33% TPSdot accel enrich.
MAPdot accel enrichment is not implemented in the standard MS-I code, but it is available in both MSnS-E code and MS-II.
Lance.
Still stalling
Lance and Jeff,
I tried again to adjust the VE table to keep it from stalling. I tried to make it 10% richer (sometimes more) and still had the problem. This problem seems to have gotten worse as I have retarded the timing (to avoid the pings and rattles under heavy acceleration. On the possitive side, my legs are getting stronger pushing the old chevy into the garage (uphill of course).
Any suggestions on where on a TPI setup should I connect the vacuum advance for the HEI distributor?
Is it possible that I have the idle RPM too high (~1200 RPM) and the torque converter is locking up an stalling the engine?
Additionally, I think that the O2 data is lagging several log points behind due to the distance from the combustion chambers to the sensor (in the header collector). Any suggestions for setting the EGO values to accomidate this distance?
I tried again to adjust the VE table to keep it from stalling. I tried to make it 10% richer (sometimes more) and still had the problem. This problem seems to have gotten worse as I have retarded the timing (to avoid the pings and rattles under heavy acceleration. On the possitive side, my legs are getting stronger pushing the old chevy into the garage (uphill of course).
Any suggestions on where on a TPI setup should I connect the vacuum advance for the HEI distributor?
Is it possible that I have the idle RPM too high (~1200 RPM) and the torque converter is locking up an stalling the engine?
Additionally, I think that the O2 data is lagging several log points behind due to the distance from the combustion chambers to the sensor (in the header collector). Any suggestions for setting the EGO values to accomidate this distance?
I looked at your MSQ file. Since you are using MegaSquirt 1, the MAPdot does not apply for your acceleration enrichment. Try going from 2 squirts to 4 squirts. Four squirts seems to work better in most V8s. Also set, your EGO correction limit to around 1500 RPMs. Most engines I have tuned like the idle air fuel ratio around 12.5-13.5 to 1. If the EGO correction is on, it will try to lean it to 14.7 to 1. I was surprised how your VE table starts at 44% and goes to 209%. My Chevy VE table is very flat.
The EGO sensor at the collector should not be a problem. It should be a 3 or 4 wire heated type. Also make sure you have no exhaust leaks before the sensor or you will get a false lean signal from the sensor.
I am not sure what tee on the TPI throttle body will work for the vacuum advance. Hook a vacuum gauge to each one. The one that has little vacuum when the throttle is closed, and lots of vacuum when the throttle is just opened up is the one to use.
The EGO sensor at the collector should not be a problem. It should be a 3 or 4 wire heated type. Also make sure you have no exhaust leaks before the sensor or you will get a false lean signal from the sensor.
I am not sure what tee on the TPI throttle body will work for the vacuum advance. Hook a vacuum gauge to each one. The one that has little vacuum when the throttle is closed, and lots of vacuum when the throttle is just opened up is the one to use.
Jeff in San Diego
Is it possible to run the newer software with the hardware I have (68HC908 processor and MPX4250AP MAP sensor)? how difficult is it to reload if it is? I am an mechanical engineer by trade and seem to get lucky once in a while when it comes to this 10011100 stuff.
I am running a heated 4 wire Bosch O2 sensor and believe that I have all the exhaust connections sealed tightly.
I have been running the EGO at 0% because of the feedback loop problems I have had and because I am in the table all the time.
As fot the table values, I was trying to dial in the upper end of the table while getting the timing adjusted. Since I have not had much luck getting out of the garage, I have not messed with that part recently. I am running 35 lb/hr injectors (a little on the big side) with the regulator backed all the way out (3 bar), and estimate that I am in the 350+ HP range (ported heads, headers, cam....).
Thanks for the help thus far. Keep sending suggestions, and I'll keep trying them.
David in South Carolina
I am running a heated 4 wire Bosch O2 sensor and believe that I have all the exhaust connections sealed tightly.
I have been running the EGO at 0% because of the feedback loop problems I have had and because I am in the table all the time.
As fot the table values, I was trying to dial in the upper end of the table while getting the timing adjusted. Since I have not had much luck getting out of the garage, I have not messed with that part recently. I am running 35 lb/hr injectors (a little on the big side) with the regulator backed all the way out (3 bar), and estimate that I am in the 350+ HP range (ported heads, headers, cam....).
Thanks for the help thus far. Keep sending suggestions, and I'll keep trying them.
David in South Carolina