Hillclimb - Throttle double spring requirement

[swsambler]

I am intending to enter my Roadsport 175, (Duratec 2.0l, 2010 self build), into a number of hillclimbs this year and in preparing the car have read that I may need two throttle return springs.

 

Can any one confirm this?

 

And if so are there any component /supplier recomendations and or instructions on where on the throttle linkage it might fit?

 

Simon

Roadsport 175 SV

[robmar]

Swsambler - I don't know much about duratecs what induction is the 175 runnng is it throttle boddies or a single one + plenum

 

rob

[Shaun_E]

The requirement is not for 2 springs but is for each throttle to have it's own spring.

5.4.2. Be equipped with a positive method of throttle closing by means of external spring/springs so that in the event of failure of any part of the throttle linkage the throttle(s) are sprung closed.

The requirement stems from things like twin webers where the linkage could break leaving one carb on wide open throttle. I think that the 175 Duratec has a single throttle body on a plenum and therefrore needs no modification from standard.

If you have separate throttle bodies for each cylinder then each throttle body needs a spring. If you have 2 paired throttle bodies then each pair needs a spring.

 

Yellow SL #32 - member of Drowned Rat Racing

[skydragon]

Mmmmm.....

 

Shaun, i agree totally with your MSA regs not mentioning the need for two springs per throttle...however many (most?) competition regs stipulate that each throttle must have two return springs, to prevent the throttle remaining wide open, should one spring fail.

 

Most scrutineers at the events i've attended specifically check for this...and whether it is in the regs for the specific event or not, it's not worth the hassle not having them.

 

The good news is that (i think) most throttle assemblies on caterhams come as std with a pair of springs. Eg. K-series std plenum throttle has a pair of coil springs. My jenvey TB's have a pair of springs fwiw.

 

As background the HIllclimb and sprint association says

If you want to use a road going car, be that your weekend toy or everyday road car, and many people do, then you will need it to satisfy a number of safety and competition requirements:

Have a sticker on the ignition key or cut out switch indicating which way to turn it off

Have stickers indicating the location of the extinguisher toggle (if fitted) and tow points

Have a yellow battery earth cable (yellow tape works wonders here)

Have your race number on the sides of the car (magnetic door squares are available or stick some numbers on a white background in the rear windows)

A timing splitter

Secure seats

Two throttle return springs

A generally good-condition car

If you are entering a roadgoing class then the car must have a valid MOT, road tax disk and insurance.

---

 

HTH

 

 

[skydragon]

To answer your other question

And if so are there any component /supplier recomendations and or instructions on where on the throttle linkage it might fit?

most seem to parallel up with the exising spring, as backup...however, if your current throttle only has one spring and you need to add a second, be very careful that this doesn't foul the linkage and cause the throttle to actually jam. I've seen a car where the second (retrofitted) spring had jammed against a casting lug on the TB and had caused the throttle to jam wide open ( kind of defeated the whole reason for fitting!)

[Rattie]

Ummmm... Unless I'm mistaken (possible) the single TB on the 175bhp Duratec plenum does have a double spring, interleaved.

 

pic showing the double spring on the 175 plenum (I think)

 

Martyn

 

Martyn

^_R300GRR

[Nigel Fox]

Sean's explanation is correct. I think the requirement for additional springs arises on some Webers for example, where the manufacturer's springs are internal, and therefore not visible for the scrutineer to check.

 

Full time class 4 Zetec

[skydragon]

I disagree Nigel

 

Most scrutineers when doing their checkover will specifically look for two sets of return springs on each throttle linkage...nothing to do with webers, or hidden springs.

 

All they are interested in, is knowing that if one spring fails, the other will close the throttle.

 

Many (all?) sevens have this as standard (??) but it is well worth double checking to avoid problems. Both with scrutineering and with a wide open throttle.

 

If you doubt me, I'm happy to wager a bacon butty, that at Harewood in August if you remove one of your throttle springs you won't get past scrutineering

 

 

 

[Nigel Fox]

I ran for many years with a pair of Dellorto carbs with one spring per carb, rarely was it questioned and it always passed when I explained the rule to the scrutineer! 😳 Not sure what's on the Jenveys, too cold to look.

The rule quoted by Sean seems pretty clear.

See you at Harewood if not before.

 

 

Full time class 4 Zetec

[skydragon]

Rattie - it's hard to tell 100% from the angle of the photo, but it looks like the single TB you show has a twin coil spring arrangement as standard, the same as a Rover k-series single TB. So all ok.

 

Nigel - agreed that the MSA rule is clear and doesn't specify twin return springs, but I wouldn't want the Original poster to end up not being able to compete at his first competition, or have hassle/stress of rejection for the sake of a quick check and (if necessary) cheap addition.

 

jenveys have twin springs as standard.

 

 

[Shaun_E]

I've just had a look at my Jenvey's and they have one spring on each paired throttle body. So yes there are 2 springs but only one per TB.

As we all know, scrutineers are human and their understanding or interpretation of the regulations varies.

 

Yellow SL #32 - member of Drowned Rat Racing

[Lee Fowler]

Quote from 2011 Blue Book, 5.4.2 Be equipped with a positive method of throttle closing by means of external spring/springs so that in the event of failure of any part of the throttle linkage the throttle(s) are sprung shut.

 

Lee

 

A7 VXC

[Stuart Miller 7]

and it doesn't matter how many springs you have on your TB's if there's a bit of grit or dirt in there. Both springs bind up on the shaft and the butterflies remain wide open - so that's 8000 something RPM, more than likely when you don't want it!

 

Certainly worth a check over if it's not been done for a while and maybe the application of a little graphite based lubricant. I check the throttle linkage and operation everytime I drive the car now.

 

I Pick up the car from Arch on Tuesday

 

Stuart

 

 

[swsambler]

Thank you for all the replies.

The photograph of the single throttle and plenum arrangement is as per my Duratec 175. I will check that the axial spring, as shown in the photo, is in fact two coiled together.

With a bit of luck the BARC Harewood practice day on 27th March and a trip to the Harewood school on 7th April should clear everything up before I turn wheels in anger.

 

Simon

Roadsport 175 SV

[skydragon]

BARC Harewood practice day on 27th March

have a good day at the practice session, there is normally a good turnout and a good day by all.

 

My only advice is, put a second layer of underwear on...then a third layer...then an extra jumper.... some gloves...a scarf... 😬 😬

 

Hint - it will be soooooo cold !!