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View Full Version : Bypass airflow restrictor

mx5jmcb
10-02-2007, 03:39 PM
Hey guys,

Tom sent me a bypass valve which did not have the restrictor on the end of the diaphragm and after installing it, seems like the response is considerably improved. Im quite happy with the free upgrade :P...you can remove the restrictor by the way with a set of pliers. You can see the way it moves at idle that it responds much quicker to throttle inputs.

Whats the restrictor used for? Is it for smoothing out transitions between vacuum and boost?...because it actually feels smoother since it kicks in right away.
Tom @ Fast Forward
10-02-2007, 04:26 PM
The restrictor is simply there to slow the transition from vacuum to boost. It is there to try and give the ECU a chance to react. If it runs OK, leave it off. I prefer it on as I think it just smooths out the transitions a little better.
mx5jmcb
10-02-2007, 07:13 PM
It definately works fine for me, ecu seems to react very good to it since AF's are in the zone right when i floor it....makes a BIG difference in on/off boost response.

I didnt really like the transition that i fealt from the bypass i had on/off boost, kinda of felt like a small turbo spooling up and kicking shortly after flooring it but now its much better, more blower like. People should try this and see the difference, some year miata's might respond better, who knows.
jacky1982
10-03-2007, 01:02 AM
Thanks for this valuable thread!

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ThomS
10-03-2007, 04:54 AM
The restrictor is simply there to slow the transition from vacuum to boost. It is there to try and give the ECU a chance to react. If it runs OK, leave it off. I prefer it on as I think it just smooths out the transitions a little better.

Tom Can you tell me what this restrictor looks like and where it is?
Do I have it you know my car better thatn I do?
mx5jmcb
10-03-2007, 07:09 AM
Tom Can you tell me what this restrictor looks like and where it is?
Do I have it you know my car better thatn I do?

Here's a pic of a bypass similar to ours. The arrow indicates were its fitted, its a metallic piece fitted at the end of the bypass tube which restricts air flow.

http://img299.imageshack.us/my.php?image=eatonbypassvalveoi9.jpg
99mx5
10-03-2007, 10:23 AM
I remember reading that the restrictor keeps the actuator diaphram from breaking by damping the transitions.
mx5jmcb
10-03-2007, 10:57 AM
Does magnussen put the restrictor from factory?
99mx5
10-03-2007, 02:22 PM
Yes they do.
Tom @ Fast Forward
10-03-2007, 02:30 PM
Thom,

Yes you do have it. It is brass and stuck in the nipple on the bypass valve. All kits I have shipped since day one (as FFS) have it. BRP used to pull them out so the early Coldsides sold through them are sans restrictor.

Tom Can you tell me what this restrictor looks like and where it is?
Do I have it you know my car better thatn I do?
Tom @ Fast Forward
10-03-2007, 02:32 PM
I did not notice that the last batch of replacement bypass valves didn't have it. However, you can send me an email and I will send you one (I have a batch of them someplace) or, if you got a replacement bypass actuator without one, you can pull the one out of the defective bypass and put it in the new one.
Kyp J
10-03-2007, 03:37 PM
Thom,

Yes you do have it. It is brass and stuck in the nipple on the bypass valve. All kits I have shipped since day one (as FFS) have it. BRP used to pull them out so the early Coldsides sold through them are sans restrictor.

Would I fall in that category? You sent me the kit but I don't know who supplied the parts to you at that time (Just after Ari got his.)

I actually have extra restriction in that line with my valet mod so it doesn't matter probably.
bogey
10-03-2007, 05:09 PM
I took a look at the original actuator I have with the broken rod and it has the restrictor, but the replacement actuator I picked up in July was missing it. That was the one that blew out the diaphram after 3 days. I believe the replacement you recently sent has the restrictor, but I am not sure. I really don't feel like pulling it off to check it...
Tom @ Fast Forward
10-03-2007, 05:46 PM
Bogey, All you have to pull is the 1/4" hose off the bypass barb. If you need one, I can send it. With the Coldside, we DO have very abrupt changes from boost to vacuum and vacuum to boost.

Kyp, I would guess you probably don't have it.
bogey
10-04-2007, 04:22 AM
I will get around to checking for it. I still have the original bypass with a restrictor should I need it.