When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I was probably using the wrong term to describe it. It appears to be batting, like you would stuff in a speaker enclosure to eliminate reflective surfaces and related unwanted noises, not a baffle. A baffle is pretty close in concept, though.
This is interesting-- a description of what a "dashpot" is supposed to do. The same post was primarily an answer to how DBW throttle systems tend to "rev hang" when your revs fall between manual transmission shifts.
From a Ford Fiesta 1.0L ecoboost sub-forum, post #7 on page 1 of this thread:
"...and a device called a dashpot has been used as an aid to fuel economy since the 70's. A dashpot in its first iteration was controlled by vacuum to keep the carburetor throttle shaft from closing when the pedal was depressed. Into the late 80's and 90's it was updated to a 12v solenoid until MPFI became standard and full computer control over the engine was used to perform the duty. The steadier you can keep your rpm's, the better fuel economy you'll see."
So it appears the "dashpot" is a common fuel economy device with a long history.
That's weird, but it might explain why the description of the SC's dashpot is all over the board. Ours doesn't appear to have any vacuum or electrical input... I don't see how this version could have any bearing on fuel economy.
The term 'dashpot' reminded me of analog modeling course I took many years ago and more information can be found here https://en.wikipedia.org/wiki/Dashpot.
For car enthusiasts, the equivalent is a shock absorber .. which comes into play when there is quick change ... when throttle is punched or let go. The pin makes it unidirectional ... you can punch with nothing to hold it back, but when you let go, the pin holds it throttle from shutting completely. The damping effect is by the air in the chamber (air filter needs to be clean for the dashpot to work as designed).
Based on the above, we should leave this part alone and only give it attention when the engine stalls when you let off the gas instantly from say 1/3~1/2 throttle.
I did a lot of research on the dashpot (*edit mixed up dashopt and throttle opener, see edit below) when I was using the ls400 throttle body.
*there are 2 components that are on the throttle body, the throttle opener and the dashpot
*the throttle opener helps with emissions and stabilizes the idle when you let off the throttle very quickly by allowing in a little extra air. it doesn't affect economy but it has an effect on emissions.
*normally it has a vacuum line going to it from a ported port on the throttle body (its ported to only get vacuum on quick decel, dont ask me how but if you let off the throttle slowly it wont get vac, let of quick and it gets vacuum), and so when you have a rapid decel, the ported vac port on the throttle body picks up enough vacuum to extend the throttle opener, which holds the throttle plate open for like 1 second or less and then it slowly retracts and the throttle plate closes. you can see it extend by revving it up via the throttle lever on the throtle body and suddenly letting go so it shuts. try it again but this time let off slowly and you will see it does not extend.
*The dashpot is the other one with the removable cap (sponge/filter inside) and a plunger looking thing, and it basically is set to act a shock absorber when the throttle closes so it doesn't slam shut.
*Salimshah described it above correctly.
that being said, I have run quite a few throttle bodies without them on na-t and it hasn't been an issue, but every once in a while if you let the throttle snap shut fast it will give you a little pop in the exhaust from the fuel. the dashpot normally gets rid of that basically along with stabilizing the idle a little bit on decel but you dont notice the second part much really you can always bump up the base idle a hair to compensate via the throttle screw.
I did a lot of research on the dashpot when I was using the ls400 throttle body...
Are you sure the LS400 dashpot is the same? (And am I sure that the SC300 and SC400 version are the same...?) That's one of the points of confusion I've seen in my own research, with the LS400 supposedly having a vacuum connection. Unless my SC400 dashpot has been inexplicably modified and a vacuum port has vanished, I don't see how that's possible on ours. Also, mine has a spring in the plunger, which wouldn't make much sense if it's vacuum operated.
you are right I had a brain fart there, I was confused between the throttle opener and dashpot. the throttle opener is vacuum operated to let in more air as described above, the dashpot just softens the snapping of the throttle from closing too fast and has the sponge thing on the bottom no vacuum line (its been a while since I have looked at a stock throttle body). I want to say most of the older throttle bodies have the opener and the dashpot. mine had both on the stock sc300 and also the ls400 but I removed the dashpot on the ls400 one to make more space.
here you can see both the dashpot (top left with cap) and throttle opener (bottom left with vac line).
you are right I had a brain fart there, I was confused between the throttle opener and dashpot...
That makes more sense. I always wondered what that second contraption is I've seen on the LS throttle bodies. I wouldn't be surprised if other people have mixed the two up and that's why there's so much contradictory info to be found.
I was at a local Toyota dealer and went to order one of these little dashpot filter cartridges for a '93-'97 Supra NA.
According to them, Toyota only sells the entire dashpot assembly. I'm not even sure if this is the correct part but when I asked them to look for "dashpot" this is what they came up with:
In their exploded diagram it did look like the little assembly with the cap on top of it but the angle it was displayed in was wrong. At the time I assumed this was because the angle of the throttle body in the diagram obscured the location of the dashpot (the rear of the TB was facing the viewer). So my *guess* was that the "dashpot" assembly was pictured separately for this reason.
However, assuming that is the correct part number for it, it's crazy that a simple replacement filter supposedly isn't offered.
Can anyone confirm this?
It gets weirder because when I pulled up the same part number from Lexus South Atlanta Parts I got the same "22202" sub-number in a location on the other side of the throttle body where it is a familiar but completely different part with no filter assembly:
However, assuming that is the correct part number for it, it's crazy that a simple replacement filter supposedly isn't offered.
Not crazy at all, as I'm of the belief that it's just a baffle, not a filter, and they saw no reason to replace it. The crazy part is making such a fragile cap for it. Although, even that is consistent with the craptastic plastic throughout the car. Having just pulled three dashes and seen how light and durable they all are, I can't help but wish that that level of plastic quality had been used on all the interior panels and engine bay parts.
whats wrong with your dashpot? they pretty much don't go bad normally the cap pops off.
you can just find a new cap off another throttle body, and the sponge is just a sponge, you can cut a small one and stick it in there I think its just to keep debris out/ slow down how fast the air gets out.
I completed an NA-T on my SC300 this past fall. Recently I noticed that on my vacuum gauge the boost was not holding stable but would start dropping off after holding the throttle for a few seconds. I figured I had a leak in my system. I did a pressure test and found one large leak where a vacuum line had come off all together. But I also found that the dashpot on the back side of the throttle body and the EGR vacuum modulator were leaking. I figure I could do an EGR delete to handle the modulator but what do you think about how I should handle the leaking dashpot? The part (22202-46060) is no longer available from any dealer.
Thanks,
Bruce
Originally Posted by Ali SC3
I did a lot of research on the dashpot when I was using the ls400 throttle body, it just helps with emissions and stabilizes the idle when you let off the throttle very quickly by allowing in a little extra air. it doesn't affect economy but it has an effect on emissions.
that black cap and sponge thing under it is just a place for it to vent or bleed off the excess vacuum/pressure so it can open and close again.
normally it has a vacuum line going to it from a ported port on the throttle body (its ported to only get vacuum on quick decel, dont ask me how but if you let off the throttle slowly it wont get vac, let of quick and it gets vacuum), and so when you have a rapid decel, the ported vac port on the throttle body picks up enough vacuum to extend the dash pot, which holds the throttle plate open for like 1 second or less and then it slowly retracts and the throttle plate closes. you can see it extend by revving it up via the throttle lever on the throtle body and suddenly letting go so it shuts. try it again but this time let off slowly and you will see it does not extend.
it basically keeps it from snapping shut cause even though you have fuel injection versus old carbs, it doesn't adjust quite fast enough when the throttle snaps closed and extra fuel is left in the cylinder (usually results in a small pop from the exhaust). it was thought to be more important on manual trans cars and autos have them but dont need them as much.
that being said, I have run quite a few throttle bodies without it and its never been an issue, but every once in a while if you let the throttle snap shut fast it will give you a little pop in the exhaust from the fuel. the dashpot normally gets rid of that basically along with stabilizing the idle a little bit on decel but you dont notice the second part much really you can always bump up the base idle a hair to compensate via the throttle screw.
Had them mixed up in the first post but the dashpot is the one without a vacuum line so that wouldn't be the one leaking.
I think you are talking about the throttle opener then, you could remove it on a na-t if it is giving issues, your bov will probably react better also since the throttle wont hang open on rapid decel.
leave the dashpot (one without the vac line) if using the OEM throttle body doesn't really hurt anything.
OK. I will check the throttle opener. I will have to take off the intake to do the EGR delete and will check it all out.
Thanks for the reply,
Bruce
Originally Posted by Ali SC3
Had them mixed up in the first post but the dashpot is the one without a vacuum line so that wouldn't be the one leaking.
I think you are talking about the throttle opener then, you could remove it on a na-t if it is giving issues, your bov will probably react better also since the throttle wont hang open on rapid decel.
leave the dashpot (one without the vac line) if using the OEM throttle body doesn't really hurt anything.
12-30-15, 01:20 AM
Having just pulled three dashes and seen how light and durable they all are, I can't help but wish that that level of plastic quality had been used on all the interior panels and engine bay parts.
