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Dashpot vacuum line connection on turbo engine

Joined
20 January 2008
Messages
704
Location
France
My LoveFab turboed NSX has been stalling frequently since I installed the turbo system.
At first, I tought the AFR needed some fine tuning but allthough the engine would die a little less often, it still occured especially driving around town.
I quickly learned to apply the heel and toe technique when slowing down for redlights:cool:
What happens is that when you lift your foot of the accelerator to get to a halt, the engine would go down to maybe 4 to 500 revs before eventually catching up ...or dying!
I decided the problem had to be electromechanical given the time constant involved.
Looking through the NSX factory manual, I discovered that there was a "dashpot" that basically slows down the closing of the throttle:wink:
After locating the device in the engine bay, I discovered that the vacuum line that should connect it to the engine air intake was not connected!!!
Given that this pick up point is not available in the LoveFab kit, where do I connect it?
Do I splice any line to connect it or do I plug it through a hole in the new intake???
I've asked Cody but he's busy at Pikes Peak I believe?
As usual, the devil is in the detail...
 
Can you take a pic? I'm too tired to figure out which line you are talking about.
 
Here are two pictures: the current set-up with the dashpot not connected and the OEM air filter assy with the dashpot vacuum line in place.
048275a9.jpg

f2f3c9e7.jpg
 
That's a good question. I've done the same as LF to date. Looks like there is a one way check valve in OEM config, so it should be OK to use even with boost vs. an NA setup(assuming this activates under vacuum when decelerating). With that, you should be able to T into any vacuum line that fits and it should work?
 
Actually I believe that is a filter and not a check valve, The dashpot diaphragm operates by "venturi" vacuum in the intake - I have run Hondas (including the NSX) without it for years (like over 15) without issue, it is designed to slow the closing of the throttle body for emissions purposes, not to prevent stalling.

- I'd look elsewhere for the stalling issues
 
Actually I believe that is a filter and not a check valve, The dashpot diaphragm operates by "venturi" vacuum in the intake - I have run Hondas (including the NSX) without it for years (like over 15) without issue, it is designed to slow the closing of the throttle body for emissions purposes, not to prevent stalling.

- I'd look elsewhere for the stalling issues
I've blown in the check valve and indeed it acts a one way valve so using it with a turbo system should be OK?
From a function standpoint, the NSX factory manual says: " The dashpot is employed to slow the closing of the throttle valve during gear shifting or deceleration".
That's what I mimick through my heel and toe to prevent stalling...
Maybe this can be done through the AEM box in conjunction with the EACV?
 
That's a good question. I've done the same as LF to date. Looks like there is a one way check valve in OEM config, so it should be OK to use even with boost vs. an NA setup(assuming this activates under vacuum when decelerating). With that, you should be able to T into any vacuum line that fits and it should work?

What's your exact configuration with respect to the dashpot vacuum line?
I had the LF turbo installed with very little direction as I'm located in France...
 
The dashpot diaphragm operates by "venturi" vacuum in the intake - I have run Hondas (including the NSX) without it for years (like over 15) without issue, it is designed to slow the closing of the throttle body for emissions purposes, not to prevent stalling.

- I'd look elsewhere for the stalling issues

+1. I removed mine a long time ago on the NSX with no ill side effects I could tell.

BUT, when I changed to an AEM ECU I had to play around with the idle trims and "RPM Offset vs TPS" to keep my engine from dying after I suddenly closed the throttle. This is a common thing to play around with. I had to search the internet to get some ideas on what to change. Now it works perfectly.

I'm guessing you installed the AEM at the same time as the turbo - therefore, your AEM calibration may be another place to check.

Dave
 
I too have this problem but the car rarely dies. I also have the AEM EMS Series II, and the light throttle responce is not that great. It stumbles just a tick at just off idle. And when running at very light throttle, like coasting, the engine want to add fuel or not add any. So I get this bucking. It's like rodeo sex.

The tuner tells me that the NA2 throttle body has a control in it that slowly closes the throttle plate (emission related) and the that there is no way to tune around it. Maybe the new AEM (Infinity?) system will because it is programmed to control DBW.

Anyone else have this issue. Sorry for jacking the thread but I thought this might be applicable here.
 
+1. I removed mine a long time ago on the NSX with no ill side effects I could tell.

BUT, when I changed to an AEM ECU I had to play around with the idle trims and "RPM Offset vs TPS" to keep my engine from dying after I suddenly closed the throttle. This is a common thing to play around with. I had to search the internet to get some ideas on what to change. Now it works perfectly.

I'm guessing you installed the AEM at the same time as the turbo - therefore, your AEM calibration may be another place to check.

Dave
Great, I'll go into the AEM programming and look at the "RPM Offset vs TPS"!
Are we having fun yet?
 
My 91 with apx turbo kit and aem ems series 1 version 2. I run without it for 3 years no problem. I think it's all in tuning to get it right. I remember when the tuner came to my house set up the aem ems then we went to street tune it first, after that we have to drive 1 hour to his shop to get it tune on Dyno.

On the way there he would call me every 15 minutes and ask how the car run and anything feel weird. And I told him everything runs smooth but only problem was when I stop at the light or put it on neutral it goes down to 900 rpm then jump Up to around 1300 or 1400 rpm then goes back down to 900 rpm and stay there and he told me he means to did that for oil pressure or something like that I forgot what he told me.

When we got to his shop, put it on Dyno and he did magic. first pull the car makes 372 at 5.5 psi, 9 pull later the car makes 380 at 5.5 psi. Then we went back on the street to do more street tune, at this time the car run, drive and idle pretty much like stock from the factory. Then we turn the boost up to 7 psi and keep it there ( still run stock clutch don't wanna burn it up yet). Fast forward 3 years later the car still run the same tune without any problem even cold start. So I would think good tuner can fix it for u. Good tuner with wideband gauge will help a lot with drivability of ur car. Gl
 
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When I used the original modified AEM (Autowave), same issues and difficulty starting. When I switched to the FIC which was tuned by Lovefab, no issues with stalling and easy start. I now have the modified AEM Series 2 (SOS) and again have similar stalling issues and difficulty starting. Because of Pikes Peak, the road test tuning has yet to be completed although the car drives like stock except for the starting and the stalling. All with a turbo setup.
 
What's your exact configuration with respect to the dashpot vacuum line?
I had the LF turbo installed with very little direction as I'm located in France...

No configuration. Similar to your pic, or removed completely. Been able to tune around it for the most part. But on Tim's/Jorligan's car, it was always an issue. Probably worse on TBW cars.
 
Unfortunately for both you (Jc I'm referring to you) it's all the tune. The tune controls how much fuel at each point. For ex when Bisi tuned it, I told him at first start it was almost perfect. He wanted perfection and retuned it but that time made it worse. Start, rev to 1700' drop to 500 back up the down a few times then level out. Sine a third tune with new o2 sensors, the car now makes a pop after I shift. He said he got my a/f spot on ( he did, much closer to 14.7) but now pops when I shift ( guess its normal since a/f was closer now than before so I live with it). More back on point for a case and point, when Shawn church tuned it, he said all done, I got in, gave gas and it almost died when I let off. He had to lean it out a few cells since it was over fueling it. So point is, it is, as you say, electronic. But in the tune not car itself. My .2, just adding my real world exp.
 
Agree that it is the tune. Cody stopped by on the way home from Pikes Peak and road tuned my car while I was at work. Drove the car today, it starts easier, no change in highway or street manners as compared to stock, no pops or hiccups with hard acceleration even when breaking traction even in third gear, no problems with accelerating the car in 3rd gear from 10 mph up to redline and most importantly not a single stall with deceleration. Don't know what he did but definitely better.
 
I had the same problem but it was caused by my sos clutch flywheel. The engine decels too fast to catch itself. When it got hot it'd die pulling up to stops. I raised the idle speed in the ems and it hasnt done it since and I've been driving it all week. I messed with lots of settings and none of it helped except raising the idle.
 
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