Looking to see if anyone has changed this spring or can advise where a lesser tension spring can be purchased. I have the rotary works throttle body and I'm not a fan of tight the pedal is. The OEM throttle was so much smoother. I came to the conclusion that if I change the spring on the RW it would be closer to the factory feel.

 

Question: Is it smooth and progressive, but just too much force, or does it feel like friction? I.e., does it take a lot less pressure to hold it during release than it took to press it down (friction)? These scenarios take different solutions.

 

The initial force that I apply to the gas pedal is met with resistance. Kind of like a sticking point. I disconnected the throttle cable and the pedal was floppy. I moved the throttle plate by hand and I can feel a very slight sticking point so I took off the plate and ever so slightly adjusted the clearance to against the side walls. That took away the sticking point but it is still present when pressing the pedal so that leads be to believe the torsion spring on the throttle body has to much resistance. So I wanted to see if changing that spring to something softer that it would reflect on the pedal feel.

 

Does it stick (a lot of force initially and then less once it moves) and then move smoothly? That would be friction. If it moves off of closed and as it does, the force keeps linearly increasing, that's spring resistance. The fact that the sticking point at the throttle plates was gone, but then it shows up when pressing the throttle means there may be too much friction in the cable or less likely, the pedal pivot.

Now, having said that, a too stiff return spring would, as you were thinking, make everything worse.

 

I would say it's spring resistance because the tension increases the further it rotates.
Now that you mention the throttle cable, it could have resistance with the sleeve as it 30 years old but the pedal does have a good amount of resistance when pushed.

 

So when you rotate the plates, how stiff does it feel? Is it reasonable to do, or does it take a lot of effort?
When you press the pedal, is the pressing force a lot more than the release force? If so that's likely friction in the cable.
You definitely want enough spring tension to make sure it always closes when you let off the pedal.

 

Rotating the plates takes some effort. Definitely it's a strong spring. With the pedal also takes more effort that when released. For some reason I feel that it's to much tension on that spring. It could definitely be at least 10% softer. Unfortunately I don't have a factory TB to compare to when moving by hand. I did drive a friend's car with the stock TB and it was smoother.

 

Got it. I agree.

 

Since this is an aftermarket throttle (RW?), have you reached out to them to ask about the spring tension? The high spring tension is most likely intentional by design - as an aftermarket parts maker, they took the engineering trade-off with a stiff spring that results in the safest failure mode (i.e., throttle snaps shut) to reduce their liability risk exposure.

Think about it, unless they are selling you a TB and a complete new cable/pedal assembly for installation, they have zero control over the latter parts. So basically there's nothing stopping you or a 3rd party builder from slapping that RW TB on a car that may have a 30+ year old sticky, maladjusted & dysfunctional throttle cable/pedal assembly. And lets say your throttle sticks open for some reason, you crash and then sue them, they could at least show the courts that they did their due diligence in designing a product designed to fail safe.

 

You make a great point.
I'll try to find out more from them on the spring tension. Last I spoke with them they said that they don't have any spare parts for these TB. Unfortunately this TB wasn't my choice so I'm going to have to make the best of it. (find a solution)

 

The 1st thing I'd try is a new throttle cable. That will confirm or disprove whether the spring is too stiff. Like you said, it's 30 years old, and worn spots in its Teflon interior lining can create a lot of friction which would be more obvious with a stiff return spring. If the cable does not fix the issue, THEN look for the less stiff spring.

 

Your right. That's what I'm going to try first. Then make my life miserable finding a softer spring.... 😜

 

This part is really tailored for full throttle race applications. Easy drivability wasn't on the radar with the design. I'm hoping you can find a solution but I wouldn't bet on it.

Dale

 

Thanks Dale. Yes I am finding this out NOW... 🤦

 

I don't know if this would be possible, but a different shaped throttle-cable throttle-body pulley with a larger radius at initial opening tapering to what it is now or smaller would improve low-throttle feel and progressiveness. This, IMO, would improve streetability a bunch.

 

If you think it's catching a bit in the throat, when all performance throttle bodies plates were virtually hand made in jigs like this -

often, fine scotchbrite polishing of the throttle plates on the pivot axis and careful attention to the fixing screw positions helped......those TBs didn't have a great reputation for airtightness when new, so you probably can't make it much worse! If you wanted to persist with it rather than source a stocker, I'd expect Alibaba or McMaster might have a torsion spring to suit.

Also looking at it, there doesn't appear to be a secondary spring other than in the TPS, to close the throttle like the OEM unit, which is a bit of a worry. Particularly back in the days of carbs, to enter competitive events over here, it was a safety requirement to install a secondary spring......usually a simple coiled tension spring with hooks.

 

Here, most, if not all, racing bodies also require that - all my racecars have had at least 2 throttle-return springs.

 

The throttle plate definitely has enough force to close back up. I guess that's why they put such a strong spring.

 

In racing, the 2nd spring is for safety to make sure you're not caught with a wide-open throttle in case the primary one breaks or comes loose.

 

You can relax a multi coil spring like that by letting it unwind 1 wind as you put it on.

I did the opposite, more winds on the stock FD TB on my FC because it was too flim flam.

I either had to up the tps dead band in the tune and put up with crap throttle response or wind the spring tighter, because it would get crazy throttle inputs from the weight of my foot/leg over bumps ehen racing (found it in the data logs).

Thats a responsive/torque set-up issue though not a big power/lag issue.

 

I'll take all the suggestions and try to improve the situation. In the event I'm chasing a rabbit hole with this TB can someone comment on whether or not the stock TB is capable of flowing enough air for 450hp?

 

Yes, it can flow enough for 450hp. So can stock ports. You just need the right turbo.

Go back to stock.

 

Good to know.... Since I don't have the stock TB anymore, I found a source for torsion springs. Going to order a few that are 5/10% less tension to see what improvements I see.
Worst case I'll have to find someone who has a spare to sell.

 

You may be able to get rid of that issue with a heel rest like we use in dedicated racecars so your heel won't move over bumps. I don't know if that's practical in an FD. If you can it'll be much more controllable with your heel planted and flexing your ankle/foot for throttle pedal movement.

 

Thank you, that is a good tip.

It was an issue in my FC.

In my FD I have race seats, harnesses, decent shock damping and no power- so its not an issue yet.

But I like the idea of the "heal-up" plate as Japanese say.