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Post by curlyteeth on Feb 23, 2017 14:00:18 GMT
Hi - I recently fitted a Supercharger on my Eunos 1.8 and I'm generally very happy with it.
One issue I have is when driving on the Motorway at around 70mph and the boost keeps coming in and dropping out, every time you gently touch the accelerator. I understand that the Rev's are high and the there is load so the boost will come in, but you get quite jerky movements when you only want to speed up a little.
Has anyone else has this issue and is there a common fix?
Curlyteeth |
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Post by atlex on Feb 23, 2017 14:47:46 GMT
First thought.. over-tensioned throttle cables.
Adjust them to have a little play (2-3mm side to side)...
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Post by curlyteeth on Feb 23, 2017 20:50:59 GMT
First thought.. over-tensioned throttle cables. Adjust them to have a little play (2-3mm side to side)... Not sure why that would make any difference - wouldn't that mean you got some play in the pedal before it engaged the throttle - after the play was taken up the result would be the same?
I noticed that this question has a lot of views but only one reply is that because no one else has the problem or because they don't know the answer??
Nil responses appreciated.....
Curlyteeth
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Post by myothercarsa2cv on Feb 23, 2017 23:59:01 GMT
I've been pondering this all evening. I also have a supercharged 5 but haven't encountered this problem. Couple of questions...
What set up do you have? Dual or single throttle body? Intercooler or crossover pipe?
Have you checked the bypass valve is operating correctly?
I'm not an expert but I'll have a crack. My hypothesis is that the bypass valve isn't bypassing, which means on partial throttle the air being pushed by the charger has nowhere to go but the plenum, generating boost. The vacuum in the plenum should open the bypass valve, its default position is shut. Hopefully it's as simple as a split or incorrectly plumbed vacuum hose. Do you have pics of the install?
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Post by curlyteeth on Feb 24, 2017 9:03:46 GMT
I've been pondering this all evening. I also have a supercharged 5 but haven't encountered this problem. Couple of questions... What set up do you have? Dual or single throttle body? Intercooler or crossover pipe? Have you checked the bypass valve is operating correctly? I'm not an expert but I'll have a crack. My hypothesis is that the bypass valve isn't bypassing, which means on partial throttle the air being pushed by the charger has nowhere to go but the plenum, generating boost. The vacuum in the plenum should open the bypass valve, its default position is shut. Hopefully it's as simple as a split or incorrectly plumbed vacuum hose. Do you have pics of the install?
My setup is different to most (if not all) -
Eaton 45 (mini Cooper) S/C (standard pulley) through an old school (9years old) Flyin Miata intercooler into the air intake via the throttle body in its stock position... that's the only Throttle - I know about the alleged need to move it to intake side of the S/C due to pressure that builds up when the throttle is closed which tries to force its way back through the S/C, causing it to stall and give belt slip etc. but I alleviate the back pressure into the S/C with a Dump valve just before the throttle body....
I think running it like this gives more power - I used a GTECH to measure 6.37sec 0-60 on a standard Pulley from the 45 charger with standard clutch (before I fitted the intercooler!) and there's not idle droop etc. the car purrs on tic over....
I can hear the bypass working fine - I have no issues at lower speeds I can accelerate gently without the boost coming in but when I'm at about 70- 80mph (circa 3.5 - 4k revs) and holding a steady speed is fine and the bypass is open, but as soon as I touch the accelerator the bypass closes (because of the revs and the load I guess) and you get a kick of acceleration rather than a gentle progression - similarly when I let off... the boost drops out (by-pass opens) and the car lunges - so very choppy for M-way driving...
Curlyteeth
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Post by myothercarsa2cv on Feb 24, 2017 14:29:46 GMT
Interesting... I'm out of ideas then! Maybe you need an elliptical throttle pulley?
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Post by AutotestAddict on Feb 24, 2017 15:40:09 GMT
Might be a tuning issue? I know my tuner chap fiddled with some settings to stop an initial lurch when going from closed or barely closed throttle to wide open throttle.
Maybe some play in the throttle body? The boost trying to force the body shut, small inputs just tense up the cable/body/butterfly until eventually it reaches enough tension to open, reliving the boost, opening further to relieve the accumulated tension - thereby giving a large throttle input for little perceived foot movement?
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Post by curlyteeth on Feb 24, 2017 20:45:47 GMT
Thanks for the answers!
Food for thought....
Curlyteeth |
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Post by martiny on Feb 27, 2017 22:07:39 GMT
I think it's got to be your single post-blower throttle that's the cause. I've driven 60 or 70 thousand supercharged miles and never felt this effect - the transition into boost is seamless.
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Post by curlyteeth on Feb 28, 2017 12:46:40 GMT
I think it's got to be your single post-blower throttle that's the cause. I've driven 60 or 70 thousand supercharged miles and never felt this effect - the transition into boost is seamless.
You may well be right - I have done a lot surfing the net to research the issue since I posted this thread
I was going to go for the dual TB solution but I have read that if you keep both you will get similar issues - albeit reduced... so I have come to the conclusion that there is a clear choice to make between instant throttle response (with probably a bit more power/speed) and a smoother (and probably much quieter) ride....
I have decided to leave the TB in the stock position (Blow though set up as I have found its called - as used on certain Mercs apparently) and I'm going to install a solenoid on the Bypass so I can effectively switch off the boost for Mways and "traffic / tootling" - I'm also going to change the Blow Off Valve for an adjustable one so it releases quicker to protect the charger and the engine when I'm giving it boot.... The BOV should open faster than the by-pass (that would be under pressure without it).
Thanks for your comments
Curlyteeth
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le sigh