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Cheap DIY way to reduce lag

  #1  
Old 10-19-2018, 10:49 AM
'88 E-350
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Cheap DIY way to reduce lag

I removed the EBP sensor and installed a hose barb fitting in its place. I put a piece of 1/4" fuel hose from that fitting to the MAP sensor. I plugged the hose that originally went to the MAP sensor with a 1/4" screw. I tucked the EBP sensor back next to the fuel bowl. I theorized that it would bump accelerator response and it did, quite a bit. If I keep this set-up I'm going to install a fuel filter in the hose to help keep soot from reaching the MAP sensor and a T fitting so I can re-connect the EBP sensor.

I'd previously played with a friend's Superchips 1705 and loved the instant response. This comes close, but without the touchy pedal that the tuner gave it. The first 1/4 pedal or so feels about the same, then as I get further into it it comes alive quickly. I only took a short drive and the engine wasn't fully warmed up, I did get some exhaust smoke. This won't do everything a tuner does, but it's a cheap & easy way to greatly reduce lag.

My original plan to fool the MAP was going to be to install a resistor in the wires to make it read higher than true boost. I couldn't find which wires to jump or what resistor to use so I went the mechanical way. Now that I see how well fooling it works I'll probably try to figure out a resistor set-up, if anyone knows please let me know.


For those who don't know: The ECU waits to see boost before adding much fuel. Waiting for enough air before adding too much fuel keeps the emissions clean. Since the exhaust pressure rises quicker than boost this fools the computer into thinking there's enough air to add more fuel without running rich. The extra fuel earlier makes more power instantly and also spools the turbo up quicker. I think that putting a resistor between the power wire and sensor wire of the MAP should do about the same, fool the computer into thinking there's more boost. Mine only makes about 15lbs boost . The computer will reduce fueling around 23lbs boost so if you're running close to that this trick isn't for you.
 
  #2  
Old 10-19-2018, 04:47 PM
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Purdy cool 88'...heck, my ride with redline blocked, only makes 16#, 11# with it hooked up lol...the MAP wire that people tapped was the GREEN. Take it to ground.
Tugly had a hellofatime with that scenerio years ago, tryn to dialing something in...
edit...what about the exhaust heat feeding both, sensor and fuel line? Its only plastic n rubber.
 
  #3  
Old 10-19-2018, 05:55 PM
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That's what I was wondering.....You know that tube comes directly off of the exhaust manifold Right?
 
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Old 10-19-2018, 11:01 PM
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Mine makes 15ish with or without the red line connected to the wastegate actuator. With a tuner and/or the muffler disconnected it makes a little more, but not much.

Tapping into the signal line and connecting it to ground I think is to fool the computer into thinking there's less boost than actual. This is for those who have mods that make the boost go over the de-fueling threshold of around 23. I don't know for sure what the threshold is, but have read it's around 23. My new boost signal, which is actually exhaust pressure, gets right to that so it may be de-fueling or real close to it. I'm ok with that because I wasn't looking to make mega power, just wanted to reduce the lag. In theory, the EGTs shouldn't go crazy with this mod since it should only over-fuel briefly when you initially push the go pedal.

As for heat and the hose & MAP sensor, there's no exhaust flow though the EBP sensor tube so it's only gonna get as hot as anything else under the hood. It'll push a minute amount of exhaust in & out as pressure varies, but there's no flow to push any real exhaust heat through. It's also right up front where air is blowing across it. I drove a couple hours and played with the new found power without issues.

I got to drive it more today. When I smack the go pedal I get about a second of visible smoke, then it clears as soon as the boost comes on. If I roll into it instead of slamming it it'll accelerate with authority without making any smoke. When the engine isn't fully warmed up it seems to smoke some any time the pedal is pushed near full. I've seen a little of this in totally stock trim too, there's only so much cold diesel fuel you can cleanly burn.
 
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Old 10-19-2018, 11:15 PM
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Epb tube dont have exhaust running thru it???? What am i missing here..what epb tube you talk'n about, Willis.
 
  #6  
Old 10-20-2018, 05:23 AM
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I think he's saying that it's a dead end, so it doesn't get a constant flow of exhaust. It just gets pressurized. Which I agree with I just think there is still going to be to much heat for the MAP.

His experience seems to say otherwise though.
"In theory there is no difference between theory and practice. In practice there is"

Either way it's an interesting experiment.
 
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Old 10-20-2018, 09:10 AM
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It is an interesting experiment and when I think of it I'll shoot my EBP tube with my IR thermometer at the sensor and see how hot it is there. I wouldn't expect my heat to make it up there though, it is a dead end.
 
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Old 10-20-2018, 09:59 AM
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Being connected to the exhaust manifold should make little difference. Stainless doesn't transfer heat very well and the sensor end of the tube is pretty far from the manifold. As for getting that heat to the MAP sensor, it's gonna have to travel up a couple feet of rubber fuel hose to get there. If there was exhaust flow through the sensor then it would likely get baked, as would the rubber hose. I'm guessing the end of the fuel hose connected to the tube would be the first place to have a problem if there's much heat coming up the tube.
 
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Old 10-20-2018, 10:32 AM
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Originally Posted by '88 E-350 View Post
Being connected to the exhaust manifold should make little difference. Stainless doesn't transfer heat very well and the sensor end of the tube is pretty far from the manifold. As for getting that heat to the MAP sensor, it's gonna have to travel up a couple feet of rubber fuel hose to get there. If there was exhaust flow through the sensor then it would likely get baked, as would the rubber hose. I'm guessing the end of the fuel hose connected to the tube would be the first place to have a problem if there's much heat coming up the tube.
ill buy that.

You have before/after monitoring or just SOTP conclusion? Im down for this adventure on the 99. 02's behaving as of now(knock on wood)
 
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Old 10-20-2018, 02:17 PM
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I have Torgue Pro on a tablet for monitoring/'gauges', but nothing that measures performance nor any other gauges. SOTP feel is a night & day difference as far as lag. Don't know if peak power changed, it seems like it came up, but it might just be because of the massive reduction in lag.

Before: stomp on it from a stand-still and it would roll out slowly building power 'till about 2K RPM then it would really go. Now: stomp it and within about 1/2 second it's pulling strong. I used to be able to floor it going into a turn with nothing spectacular happening, now the inside tire slips. Not radically spinning/roasting it, but it's slipping & fighting for traction. If it were a PU it might actually spin it up. It feels close to when I was running a tuner, but less jumpy. Driving casually it doesn't seem obviously different, past 1/4 throttle or so I can feel the difference.
 
  #11  
Old 10-20-2018, 02:34 PM
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Correct me if I am wrong, but you are saying that creating a vacuum to the MAP sensor through the EBPS port has reduced your turbo lag and given you a much better throttle response? If so, why not just plumb your vacuum reservoir into the MAP sensor and then you would have a constant and clean source of vacuum to the MAP sensor.

This is not for me in any way, but I think it is interesting.
 
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Old 10-20-2018, 02:54 PM
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Originally Posted by Sous View Post
Correct me if I am wrong, but you are saying that creating a vacuum to the MAP sensor through the EBPS port has reduced your turbo lag and given you a much better throttle response? If so, why not just plumb your vacuum reservoir into the MAP sensor and then you would have a constant and clean source of vacuum to the MAP sensor.

This is not for me in any way, but I think it is interesting.
My understanding (and I might have it wrong) is that by piping the EBP tube to the MAP sensor it misleads the MAP sensor to believe that boost is up and then permits earlier fueling.
 
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Old 10-20-2018, 03:06 PM
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Mark, I am seeing his experiment the same way. That is why I was thinking perhaps the vacuum reservoir off the the pump might be a better to source to "fool" the MAP sensor into believing the boost is up. Although, if you get to the nuts and bolts about it, if the MAP sees over 25 lbs of boost, it will de-fuel so in that respect the vacuum reservoir might be a bad idea. Unless of course the vacuum from the reservoir is less than ~23 lbs, then it might be a viable source to fool the MAP.

This gets confusing quickly.
 
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Old 10-20-2018, 03:18 PM
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Originally Posted by Sous View Post
Mark, I am seeing his experiment the same way. That is why I was thinking perhaps the vacuum reservoir off the the pump might be a better to source to "fool" the MAP sensor into believing the boost is up. Although, if you get to the nuts and bolts about it, if the MAP sees over 25 lbs of boost, it will de-fuel so in that respect the vacuum reservoir might be a bad idea. Unless of course the vacuum from the reservoir is less than ~23 lbs, then it might be a viable source to fool the MAP.

This gets confusing quickly.
The vacuum tank doesn't have positive pressure it in, it has negative pressure. .
 
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Old 10-20-2018, 03:38 PM
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Where you coming up with your analogy, Sousaholic...been pop'n grandpa's cough syrup since this morning..
 

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