CAMSHAFTS

[M100]

"to finish first, first you must finish

....and in the case of a Lotus fall into bits as you cross the line

[s4elan]

Some good information regarding TwinCam cams can be found at Elgin cams web site: http://www.elgincams.com/

I am using the 78-14 in my twincam. It produces 175hp@8500, 130 ft lb torque@6500. 1,625.1,375 valves. This is with a lowly 11.2 cr. I have just upped the cr to 12.2 and expect an additional 10-15 hp.

45 DCOE Jetting: 140 mains, 185 airs, 36 chokes, F11 tubes, 40 acc pumps, 45f8 idles. I will go up to 38 chokes and perhaps 145 mains to support the increased CR. I also tested F16 and F9 tubes on the dyno and peak hp/torque didn't vary much. Of course this is a race motor and the tubes will have more significant effects on street motor drivability.

I have found that increasing the acc pump may fix some flat spots but generally it is overdone. I have a 6cyl BMW with 3x40's and had a similar flat spot that I eventually corrected by changing to an emulsion tube with a smaller diameter (F2). This allows more fuel in the well for that initial acceleration. I tried many jet combinations to no avail.

I have a Weber parts list that has all the dimensions of the various tuning parts that has been indispensible to me. It also has some little tidbits of information that is helpful, and sometimes dizzying. I will post a copy if anyone is interested.


Pete

[rgh0]

Pete

Great to have another serious twin cam racer posting. A couple of comments on your proposed mods.

Based on my simulation program I would expect about 5 to 7 hp more from the compression ratio increase you plan, about half the 10 to 15 you quoted.

I recently did some back to back tests on 2 otherwise identical race engines one running 45DCOE's with 38 mm chokes and one running 36mm chokes and had no difference in maximum power output. I would only consider going to 38mm if you have a very light car (seven or open wheeler) as the risk of low speed response loss possibly balances any potential for top end gain.

Do you have a dyno curve for your engine? I would like to add to my collection to help improve the calibration of my simulation program.
One of the interesting things the simulation program shows and McCoy has demonstrated on the dyno is that durations beyond about 290 to maybe 300 max degrees only generate marginal extra hp and you loose a lot in narrower torque band and higher revs for peak power. I suspect going beyond 290 to 300 degrees is really only useful with a Hart style head and .49 lift cam with very light open wheeler where you are matching gear ratios to every circuit.


Rohan

[paros]

Hi Pete

Glad to see your comments, I certainly agree with you on pump jets and reckon they are guilty of washing oil off bores more than accelerating! I have gone back to 40 as the 45 pumps did nothing.
The Road Dyno I use for tuning is u/s so can't comment if this is imagination but genuinly I think no effect to be honest.
Anyway your Elgin cams, I had looked at last year - in fact the engine builder in the Uk who gets some rather high REAL power outputs uses their ZL1.
It is amazing all the differnt combinations Uk tuners opt for with their engines.
With standard size sprint valves for FIA regs Burton suggest F1 inlet and BD3 exhaust.
The traditional tuners who have been doing twin cams for years favour Phase 5 and 4 [ can't remember which for inlet and which for exhaust ] and others stay with Phase 4 for inlet and exhaust. Again with standard size sprint valves for FIA.
QED, have their 450 cam [ .44 valve lift and 298 of valve opening ] which on throttle bodies gives 167 bhp at 7100 and 138 ft lb at 5900 - I suspect the 45s give the same but less tractability. By the way they suggest 38 mm chokes for 45 Webers and 155 main and 180 air using F16. I would agree with Rohan about 38 mm chokes!
It is really a pain to have to stick with the sprint size valves, but I got very involved in 3 of the FIA Ford Escorts being disqualified for illegal suspensions and engines last year, so decided it might be wise to ensure the car was 110% legal! Anyway next year who knows!

Richard

[paros]

Anyone out there used the QED 450 cam with sprint sized valves please?
I am using this combo and the usual timing is 102/104 HOWEVER when I set it at 100/106 it seemed more cammy but better above 7000. Sadly no rolling road over on a Greek island so hence the question. I am told the cams have poor volumetric efficiency and need loads of advance [ 36/38 degrees ].

Any commenst welcome as the cams seem pretty good so far and ceratinly keep the engine breathing above 7000

Richard

[Dag-Henning]

Richard, - just found your thread while searching for opinions on cams. I have been racing with 450 cams and FIA sized valves this season. On our tracks, I have found the engine to be so torquey, that I actually believe I can sacrifice some in favour of some more power on top. On what is regarded as a "true" dyno, it gives 160 bhp at 7100, and 17,2 kgm at 4770. ( - almost like a taxi...!!) Timing is 102 - 104.
Geoff Richardson i the UK, - famous for his FJ and DFV engines-, suggests using DA19 in and 1016 out, which will add a little in duration. ( - from 296 to 304 deg. )
I am generally happy with the 450 cams, but on the track you really do not need an engine that pulls as a horse from 4000. A powerband from 5 - 8 would be quite ok !

Dag

[rgh0]

Hi Dag

I dont have specs for the DA19 and 1016 cams you referenced. Who is the manufactuer of these profiles and do you have lift and duration and recommended timing details. I would be interested to see what they look like on my engine simulation versus the QED 450 and the McCoy 450 cams I run.

One of the interesting things I have found with the simulations and actual dyno work I have done is that longer duration cams with more overlap while "feeling" like they have more HP at the top end in practice dont really have much if any more. They just feel that way because of less power and torque at lower revs!

As you increase seat to seat duration above 280 degrees you start developing a hole in the torque curve in the 4000 rpm area but you dont seem to gain much in top end power even at durations up around 320 seat to seat duration. A 280 degree seat to seat cam will give good power up to 7500 rpm. A 320 degree cam will develop a few more hp at 8000 plus rpm and "feels" much better on the track at the top end as the power comes in more suddenly but area under the torque and power curve is substantially less and lap times worse on most tracks.

regards
Rohan

[steveww]

BHP sells cars, Torque wins races

[paros]

My QED 450 cams with 45 carbs gave 164 at 7100 to 7300 and a pretty flat torque curve. Stopped dyno testing at 7400 as lack of time - may have been a bit more higher up as I have the larger inlet valves including 1.4 exhaust. This was on a believable dyno near Carmarthen. The torque is peaking at 5300 and is 170 Nm [ what happened to ft lbs ]. Even at 6800 the torque is still 164 Nm. This emulates a printout of a QED dyno run very accurately, albeit on throttle bodies.
I tried the DA19 some years ago and rubbish! I then found that they were a fad with an builder in the UK who claimed a lot of power from them - they are a DFV exhaust profile. About 450 of lift and similar duration to the QED cam.
As plenty of people have seen that torque at the start makes my heavy Elan go like a bat out of hell at the start

Richard

[garyeanderson]

170 Nm = 125.38 lb/ft
http://www.convert-me.com/en/convert/torque#poundfft
or
http://www.unitconversion.org/unit_conv ... orque.html

the basic unit of 1 Nm = .737562121 LB/ft

per google search on Newton meter

Gary

[Midlife]

My second "Sprint" in a +2 got a 3rd place out of 8 runners in class. The car was quicker than some 2 litre cars, on a standard twink... I think torque, quality tyres and handling wins races, you can have too much bhp. (I want to loose more weight in the car now!!).

Very interesting reading this thread.

Cheers

Doug

[paros]

Hi Doug

I agree that tyres, set up, weight and driving are the real answers - bhp can hide failings in all these features. One of the bigger advantages I found in going for an 8000 rpm cam was that I can stay ion one gear longer than where I had to change at 7400 previously.
Last month I did a sprint [ first ever ] and used hard race slicks and won against all sorts of opposition. This was not down to bhp per ton but to the excellence of the Elan chassis and set up.
I think people enjoy boasting about bhp, the macho bit, whereas suspension tweaks are considered boring!

Best of luck
Richard

[steveww]

One of my favourite quotes has always been "tune the nut behind the wheel first"

A racing driver friend of mine has always maintained that he could spend a day with a club racer and shave 3 secs a lap of their time. How BHP is that

[Dag-Henning]

- I am sorry guys, but racing is not either/or, for me it is about the best mix of all the important factors ; - skills, handling, tyres, suspension,weight, set-up etc,etc,etc,etc, and BHP ! Do not fool yourselves to believe otherwise! I must agree though, that when you are getting close to the limits of your engine, I would not sacrifize torque and driveability for the last two or three BHPs obtainable......!

Dag

[rgh0]

Dag
I fully agree that you need to get everything in balance. No good having a top motor if the handling is hopeless the brakes dont work, the driver useless, and it breaks down before you finish.

People tend to focus first on the engine as thats the macho bit you can talk about around the bar. How many people measure their brake temperatures ?

If searching for a quick lap time the cheapest place to find it is almost always just track time for the driver for us amateurs. I have developed my car substantially over the last few years but I am not much quicker because I just dont get the track time I did 10 years ago. I could believe that with a couple of days time on the track and help from a coach I could go 3 seconds quicker but I would loose it again in a couple of weeks unless i raced almost every weekend. I see that at every race meeting - my quickest times are invariably in the 3rd race on Sunday afternoon after a day of practice, qualifying and 2 previous races.

My order of developing a car for competiton would be:

0. reliability ( make sure what you have will finish)
1. tyres ( sticky ones that work)
2. suspension ( make the good tyres work properly)
3. brakes ( now you got it going make sure it stops)
4. driver ( now it goes and stops learn how to do it properly)
5. Engine ( now work on making it go quicker still while not forgetting to keep working on 0 to 4 also)

cheers
Rohan