Slight Bogging Down (Lag) After Accelerating from Stop

[lazabby]

I got my car to a dyno shop a couple of days ago. The car runs better but I think I need to do some tweaks. One issue the dyno shop couldn't quite eliminate was a slight lag when pressing the gas pedal from a stop. I have an automatic and there is the tendency to bog down briefly when pressing the gas pedal after a stop. I don't have a TPS. Has anyone with an automatic been able to overcome that?

[AdmiralSenn]

I had the same issue on my manual, and never solved it until I added a TPS. You could try playing with the vacuum line coming off the manifold, I've seen people recommend any of a slight restriction, an accumulator/chamber, or a check valve. None of those worked for me.

Could also try bumping up your low end ignition advance slightly if you're running spark control. I noticed it didn't seem to happen to me as much when I advanced the distributor.

[dn010]

I had to adjust acceleration enrichment & timing (if you're using a MS ECU) otherwise I had a huge pause after hitting the pedal until the engine responded from a stop. However, I too have a manual transmission and TPS.

[Spittybug]

Shannon, without the TPS you are relying on the vacuum signal to tell the MS unit that you are accelerating. That has a delay on it since the vacuum must "travel" (backwards I know) to the MS unit via the hose and then be detected. No way around the physics of that other than to make the hose as short as possible. The electrics of a TPS are virtually instantaneous in comparison. I suppose it might be possible to use the stock microswitch in some way, but the more reliable way would be to use a modern car's pedal-based TPS system. I know little to nothing about them, but IIRC, Dave M. posted something about them once upon a time. Worth looking into......

Ian sent me his MS tune after he dyno'd and I'm digesting it. I also drove his car and the acceleration is nice. I suspect changes to my timing curve and acceleration enhancement are in order.

[dn010]

It must be a potentiometer based TPS to use with the MS unit that will read the travel of the throttle throughout the entire range closed to full.

I tried to use a switched based (stock Volvo Bertone 780 TPS) and it did not work for me, the manual even states not to use a switch based TPS unfortunately I read this after the fact. I guess it only tells the ECU when the throttle is closed and wide open and does not tell you what percentage the throttle is open.

I am now using a newer Bosch potentiometer type TPS that are found in a wide variety of cars.

Cheers,
Dan B.

[lazabby]

It must be a potentiometer based TPS to use with the MS unit that will read the travel of the throttle throughout the entire range closed to full.

I tried to use a switched based (stock Volvo Bertone 780 TPS) and it did not work for me, the manual even states not to use a switch based TPS unfortunately I read this after the fact. I guess it only tells the ECU when the throttle is closed and wide open and does not tell you what percentage the throttle is open.

I am now using a newer Bosch potentiometer type TPS that are found in a wide variety of cars.

Cheers,
Dan B.

Is this working with Megasquirt? Where and how did you install it?