Venturi Vacuum on a 2.5 N/A

[Trouble]

I’m thinking about eliminating the Venturi Vacuum “Y” connector on my 944 N/A, I’ve seen kits on Lindsey Racing’s website with all the correct prebent hoses for the 944 Turbos but nothing for the N/A cars. Is this just something to clean up the engine bay or are there any positive results for doing this…

[PSU_Crash]

I bought this kit for the vacuum lines https://944online.com/vacuum-hose-kit-s ... 6-87-924s/
With this kit the venturi wasn't going to work out, even though it is supposed to, so I deleted it. No ill effect that I'm aware of with a few hundred miles down.
page 6 of my thread you can see what I ran into
viewtopic.php?t=3956&start=50

[spacecad3t]

I also deleted the venturi and Y pipe on my '87 NA while refreshing the hoses I kept with silicone. Driven 1800 miles since, nothing noticeable.

I do however think that the system makes sense as a loop with the venturi restriction, it likely helps provide some dampening to the idle stabilization when the brakes are applied at WOT.

[dr bob]

On my car anyway, the venturi is needed for situations with long periods of full-throttle or at least low-manifold-vacuum conditions. It offers consistent vacuum to the brakes and the vacuum-operated accessories when there's that extended high load, when manifold vacuum isn't available. Decide carefully if power assist for brakes will ever be that critical, for instance.

[PSU_Crash]

On my car anyway, the venturi is needed for situations with long periods of full-throttle or at least low-manifold-vacuum conditions. It offers consistent vacuum to the brakes and the vacuum-operated accessories when there's that extended high load, when manifold vacuum isn't available. Decide carefully if power assist for brakes will ever be that critical, for instance.

That's interesting. I noticed recently that my HVAC controls loose vaccuum under extended WOT. I did not notice any difference in brake feel though.

[spacecad3t]

On my car anyway, the venturi is needed for situations with long periods of full-throttle or at least low-manifold-vacuum conditions. It offers consistent vacuum to the brakes and the vacuum-operated accessories when there's that extended high load, when manifold vacuum isn't available. Decide carefully if power assist for brakes will ever be that critical, for instance.

Yeah... basically what I meant with:

it likely helps provide some dampening to the idle stabilization when the brakes are applied at WOT.

I have tested the brakes at highway speeds and it isn't noticeable to me... however my engine has nearly no consumers... if you car has power steering, and is running say Heat or AC, lights, etc. You may notice weaker braking, but I would think only on the first press.

I actually plan to put the venturi and Y pipe back and run it for another 500-1000 miles to see which config is better for me.

[dr bob]

duplicate

[dr bob]

That's interesting. I noticed recently that my HVAC controls loose vaccuum under extended WOT. I did not notice any difference in brake feel though.

The brake booster has its own check valve, and the volume in the booster is usually enough for two, maybe three assisted brake applications. One might reliably think that every at extended full load operation would include lifting throttle in parallel with the two brake applications. But that's not an actual 'always' rule or guarantee. If it isn't "always" it's "never", and if it isn't "never" it's the same as "aways", at least as far as deciding if some colloquial assumption is actually reliable enough to risk your car and maybe your life.

The HVAC and cruise control are fringe functions relative to brakes, but... If I'm going to go from a brake issue, I want the AC to be working and the cruise control to be maintaining my set speed as I careen inevitable towards what ever is drawing the car closer. Like a bridge abutment.

I'm leaning towards keeping the venturi, the HVAC, cruise, and yes even the brakes, working as designed.

---

Separate but related, a long ago class in manufacturing included a reminder from an engineer at GM. The lesson was that a part that isn't included doesn't need to be designed, purchased, delivered, carried to an assembly line, tested, QC'd and function tested, installed, inspected, then inventoried and maintained in dealer stock, warrantied, and maintained available for 20 years since last used. Or the inverse, any part we can leave out saves us.... Porsche wouldn't have put the part in the car if there wasn't a really really good reason.

Should we decide that something could just come out, because the engine bay "looks a little busy"? Think back to how much the factory could have saved if they had done the work for us, cleaning up the engine bay of those useless parts. Heck yes, what did those folks really about the cars they designed? I'm a lot better at this stuff!

[PSU_Crash]

Should we decide that something could just come out, because the engine bay "looks a little busy"? Think back to how much the factory could have saved if they had done the work for us, cleaning up the engine bay of those useless parts. Heck yes, what did those folks really about the cars they designed? I'm a lot better at this stuff!

I couldn't agree more and I'm all for safety first. Those engineers did it for a reason. Bringing this car back to OEM as intended has been the goal. The only reason I deleted mine was because it wasn't going to work with the vacuum line kit from LR. I ordered the right kit, but the venturi didn't allow my lines to reach where needed. I documented that in the the My New 944 and it's issues thread. I'm definitely not ruling out install error. Perhaps I'll re-visit that this winter.
It's my understanding the late model 944s did not have the venturi. Is there something else different in the late design to make up for it?

[Tom]

Porsche deleted the Venturi itself on the later models. I've never made a study of it, but I bet there are more 951's without the venturi and with it. I took mine off decades ago and replace it with the later-year (88?) parts and have never noticed a downside. Fallacy of the masses perhaps, but with so many people deleting the Venturi and updating to the later factory set up, you'd think any real-world downside would have been discovered by now.

Edit: just realized this thread is about the n/a. I'm way less familiar with that set up, so can't really speak to that motor's Venturi...