R20 or R21

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Swimpster
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R20 or R21

Post by Swimpster » Sat Dec 18, 2010 11:29 pm

Hi All

I am looking to do circuit racing in my Clan in 2011 and I have built up a reasonable amount of competition components, engines, gearbox carbs etc. I am fitting a 998 unit with big valve head (1.4 and 1.125 valves) coupled to a competition gearbox, build by Dave Weedon, with raised 1st, lowered 3rd and 4th. I am going to use Weber 40's on a stainless combined inlet and outlet manifold.
I have a choice of cams to fit, but with it being my entry into motorsport, I will probably steer clear of the wildest cams (R22 & R23 etc) for a season. The decision I have to make is whether to use the R20 or the R21 cam. From what I can gather, the R21 can be a bit awkward for power delivery, where the R20 is more predictable. Is this the case, or would the R21 be a better proposition? Any feedback would be appreciated.
I would also like to know what the best solution for the exhaust would be, is an across the back silencer the only real option to go for and where would the best place be to get one from?

Cheers

Tim
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Re: R20 or R21

Post by KiwiHusky » Sun Dec 19, 2010 12:13 am

Hi Tim, I use an R20 in my G15 for a combo of road, track and hillclimb and find it to be very flexible and forgiving as well as giving good performance. Andy Dawson who wrote "Dawsons Dodges" for the CCC magazine, always preferred it as the best all-round camshaft option for performance. I hope this is of help.

Cheers, Simon.
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Re: R20 or R21

Post by apeximp » Sun Dec 19, 2010 8:27 am

Hi Tim , just to muddy the waters I used a fraser b cam this year in my 998 Fraser imp replica while doing two events at silverstone , this i am told is between a R20 & R21 and was very balanced cam and I was able to driver the car on the road without to much problems and get it up to 8.5k revs on track !
Gone 1040 R23 now though , ultimate power required ! :D
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Re: R20 or R21

Post by pimpdriver » Sun Dec 19, 2010 11:33 am

I've run an R21 for years in my road Clan, done a few trackdays with it, and the engine went in the hillclimb car a few times. I've found it a brilliant cam, more power than an R20 with no real downsides. I would say if you are using a standard box, use the r20, but you are using a close ratio box, so go for the R21.

Eric
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Re: R20 or R21

Post by Swimpster » Sun Dec 19, 2010 4:33 pm

Thanks Gentlemen
I suppose the question I was asking was if the R21 would be a step up from the R20 without any drawbacks. Most people seem to go from the R20 to R22 or R23 and I was wondering if there was a reason for it?
The car is mainly going to be used on the track, it will be road legal, but with it having lowered top end ratios, I don't intend to have many long jouneys up and down the M6 in it. So, with that in mind I'm going to go with Eric's suggestion and put the R21 in.
With regard to the exhaust system, which would be the best to go for, across the back with a bike box, or a Janspeed or something similar in the conventional position? Is there any type out there which members of the forum would go for and where would be the best place to get one from?

Cheers

Tim
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Re: R20 or R21

Post by benwick3 » Sun Dec 19, 2010 5:10 pm

Based on my 25+ years of circuit racing I'd suggest that you start with the R20. This will allow you to make those little mistakes without losing too much time. Once you've got experience then move to the R22 or Fraser B, virtually the same cam according to Ian Carter. Stick with this if you are restricted to dizzy ignition and the changed ratio's in a basically standard box. Don't go to a R23, you will be slower due to the additional number of gear changes required to keep it in the power band.

If you are able to use programmed ignition then it is advantageous to fit either the R23 or GE3 as you retain the tractability of the R22/Fraser B with the additional top end power of these cams.

As regards silencing you will likely require a considerably large across the back silencer to keep below circuit noise limits. In my experience bike cans are inadequate for circuit noise limits. A custom built re-packable silencer works best using basalt packing which lasts considerably longer that the normal glassfibre type.

What series are you going to be racing in?

Pete Richards
Last edited by benwick3 on Sun Dec 19, 2010 8:18 pm, edited 1 time in total.
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Re: R20 or R21

Post by Swimpster » Sun Dec 19, 2010 7:16 pm

Hi Peter, we have met. I bought a lightweight bonnet and spoiler off you at last year's National. I hope you are keeping well?
I'm looking at the BARC North West Sports/Saloon Car Championship with some of the HTS boys.
I will not be using mapped ignition initially, but will probably look at that for the following season when I go for a wilder cam. Just want to get a first season under my belt to gain experience.
Merlin do 6" diameter packable exhausts and I was thinking of putting one of these accross the back, but I'm not sure if I would need a preliminary silencer in the normal position. Or if it will still be too loud?

Cheers

Tim
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Re: R20 or R21

Post by apeximp » Sun Dec 19, 2010 7:21 pm

I have been running a bike re packable can on the end of my combined manifold but sure I was over the noise limit in my two races at silverstone and just lucky !
Am going to have a link pipe fitted to larger exhaust can for next year.
The link pipe is from moose from the forum , I think he makes them to order ?
So where you going to race ?
Jim
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Re: R20 or R21

Post by cov_climax » Sun Dec 19, 2010 7:36 pm

i was going to sugggest t-logic race exhausts for your silencer, their website seems to be down , but they did any diameter and length in stainless to your sizes for around the £100 mark, they are re-packable as well. they if memory serves they're near northampton, Eric mentioned them to me a while ago and may still have the contact details.
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Re: R20 or R21

Post by Swimpster » Sun Dec 19, 2010 8:25 pm

Hi Jim
The series takes in Oulton Park, Mallory, Anglesey and possibly Donnington, if available. I'm probably looking at five races initially, the tracks are not a million miles away from me, so it suits me fine. Where do you race Jim?
With regards to T logic exhaust Cov, I'll have a look at their website when it's up, to see what they offer.
Thanks for the help guys.
Cheers

Tim
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Re: R20 or R21

Post by benwick3 » Sun Dec 19, 2010 8:25 pm

Tim,

I'm fine. Not finally decided in respect of next year but I have several options under consideration

[quote="Swimpster"]
I'm looking at the BARC North West Sports/Saloon Car Championship with some of the HTS boys. ]

Best of luck with that and a brave decision. Too great a speed differential for my liking.

Pete Richards
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Re: R20 or R21

Post by Swimpster » Sun Dec 19, 2010 8:38 pm

Hi Pete
I see what you mean with regards to the competition, may just have to throw a grappling hook out to catch one of the big boys for a tow.
Just giving it a try really, to see if we can get a group of us together to take the HTS further and see how things develop.

Cheers

Tim
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Re: R20 or R21

Post by apeximp » Sun Dec 19, 2010 8:49 pm

Like you Tim this year was my first in Motorsport so I was just focusing on silverstone that is my local to try and iron out the faults with my car (see Fraser imp in motorspot) sadly got a major gearbox fault so gave up in June this year to up grade car with new weedon box and bigger engine , car is with Impspeed at moment and expect it home in jan ready for the new season with the hscc , will try and do as many races as I can this time.
Jim
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Re: R20 or R21

Post by Mike Hanna » Sun Dec 19, 2010 10:12 pm

Hi. In the late 70s early 80s I rallied an Imp and used the R22 because the lobe is nicely rounded and very kind to the valve gear. It gives very good torque and happily reved to over 10000 rpm . I remember doing 9300 in 5th gear in a forest. It would have gone more but I was chicken!! More recently I used the same crabs, manifold, head,cam, valves and springs to win the HSCC Touring car championship. The next year I fitted an R23 without any other alterations. I found no drop in torque, just a little more top end power, And so docile you could use it for shopping! I would advise the R22 any day. Cheers and a merry xmas all. Mike
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Re: R20 or R21

Post by ibbo » Mon Dec 20, 2010 11:57 am

i loved my r22 made my davrian fly pulled well out of the twisty bits shame i snapped it in 3 at loton park would be an excellent cam for circuit use and still docile enough to drive on road in a clan
mark ibbotson
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Re: R20 or R21

Post by SimonBenoy » Mon Dec 20, 2010 10:36 pm

Tim

I have used a Yamaha R1 silencer very effectively on my race Imp and previously on my 1120cc spaceframe hillclimb car. They are readily available from ebay around £40 for a good one. They keep a 1000cc 4 cylinder bike quiet and I have never failed a noise test since I have used it - our limit is 105db.

If you have any experience of racing or keeping an engine in the power band, then you should be fine with an R21 and don't be put off from using an R23 once you have the car running reliably and you have some confidence.

Best of luck - Simon
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Re: R20 or R21

Post by Lotus-e-Clan » Mon Dec 20, 2010 10:55 pm

c
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Re: R20 or R21

Post by Swimpster » Tue Dec 21, 2010 8:03 am

Thanks lads.
I think that I'll give the R21 a go. Simon, reference the R1 silencer, would you use it on it's own, or is it best to fit another box in the conventional position and then link a pipe to it?

Regards

Tim
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Re: R20 or R21

Post by speeddemon » Tue Dec 21, 2010 10:05 am

get the biggest and most powerfull slotted in and stop being a nancy hahahahah. You aint going anywhere with 35hp hahahahah. Can you imagine Mannion saying should we use a 20.21 22, hed be saying get me the quickest and most hairiest engine to beat that BDA hahahahahah.

Have a good xmas pal catch you soon.

Mick
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Re: R20 or R21

Post by SimonBenoy » Tue Dec 21, 2010 12:40 pm

Tim

I just use the R1 with a link pipe from the manifold - the pipe that is part of the R1 silencer has some slightly odd angles, so you would need to work out how to get the 2 to join up OK. I can send some pics if it helps.

Cheers - Simon
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Re: R20 or R21

Post by benwick3 » Tue Dec 21, 2010 12:54 pm

Simon,

I'd agree about not being put off using a R23 if you are adept at keeping the engine in the power band. Not too much of a problem if you have a JK box, particularly a 5 speed, and can chose the ratios to suit. However, with a lowered third and top box, albeit with a raised 1st, the additional gear changes necessary will result in a slower lap time than that achievable with a R22, even in a lightweight Clan.

Pete Richards
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Re: R20 or R21

Post by ChrisBenoy » Tue Dec 21, 2010 1:24 pm

Swimpster wrote:Thanks lads.
I think that I'll give the R21 a go. Simon, reference the R1 silencer, would you use it on it's own, or is it best to fit another box in the conventional position and then link a pipe to it?

Regards

Tim
On the race car just the R1 silencer is used. The link pipe runs from the manifold to the back of the car followed by the silencer. Keeps it quiet and it sounds nice.
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Re: R20 or R21

Post by Swimpster » Tue Dec 21, 2010 1:40 pm

Hi Chris
Thanks for that, just to let you know I'm Tim with the white Imp, we met at Curborough, great day, hope all's well with you.

Cheers

Tim
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Re: R20 or R21

Post by ChrisBenoy » Tue Dec 21, 2010 1:54 pm

Yeah i'd guessed that it was you Tim, glad to hear the clan is coming along. Let me know when/where you are going racing and I might come along for a spot of spectating. 8)
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Re: R20 or R21

Post by Lotus-e-Clan » Tue Dec 21, 2010 2:51 pm

c
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Re: R20 or R21

Post by Swimpster » Tue Dec 21, 2010 8:23 pm

Hi Mick
I didn't realise that I 'd even GET 35bhp out of it!!!!!! I might pull two plug leads off to slow it down a bit :wink: Have a good Christmas yourself mate, speak in the new year.
Hi Pete (Lotus E Clan), yea tis I, hope you're okay mate? Glad to see that with a bit of luck, you'll be doing a some next year too. Yep, the same melted tyres will be shodding the Clan, at least the shine's been taken off them so they should stick a bit.
Chris, I've still got some way to go, but I think everything should be ready come the end of March/April, I'm giving it a real push now. I'll let you know when things start moving on the race scene, it would be good to see you again.
Simon, I'd love to see a few pictures of your exhaust set up, I've noticed the funny kink on the R1 exhausts, I've also seen couple on Ebay that have just the back box only and a seperate pipe that clamps to it, but I'll probably go for the one we're talking about and make a link pipe to fit that.
Thanks to all of you for your comments and encouragement it's really appreciated. I'll have to get some pics up so you can see how things are going.

Cheers

Tim
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