More power from a BDR

[Bilbo]

Hi All and Thorpep in particular

 

This was on the for sale site posted by thorpep but was getting well off subject! So I moved it to here. Hope know one minds but other may with to contribute that may not have read it on the Forsale list.

 

Thorpep wrote

 

>I have a 1990 1700 BDR, it has done 27,000 miles. The engine is original and unmodified. I have been thinking of having it converted to unleaded and whilst the head is off have some further upgrade work done, i.e. steel rods and crank etc. I would like to get between 200BHP and 210BHP. This is expensive work (£8,000 ish), is it worth it on a 12 year old Cosworth? I would love to hear from people who have had this done. What is your experience? where is the best place to go to get the work done?<

 

Well I had mine done last year at say 46,000 miles its now over 50,000 and I am WELL pleased with the result, its still on the original carbs and has Weber Alpha ignition. The engine rebuild was done by Roger King. At the first 7ns list RR day at Dave Walkers it hit 201 bhp and a 137 ft lbs. Well for a reason of debate on different RR accuracy it went back the following week and made 198 bhp and 146 ft lbs. The difference in the Torque reading is that the first time where was 3 of us of about 18 stone sitting on the back. Others said that the tyres looked like rubber bands.

 

As to the spec well its all steel with Doug Kiddie Crank shaft see http://www.racecar.co.uk/dkecrankshafts/centre.htm

 

This is a great bit of engineering and well worth the little extra it costs. I had a new L1 Cosworth inlet cam and the old BDR exhaust cam reprofiled to L2.

I have forgotten the valve sizes but they are quite a bit bigger. The porting on the head is a work of art but then what else would you expect from Roger King. New AP clutch assembly and lighten steel fly wheel. The top power is at 7750 rpm and loves getting there with a change at 8300.

 

On the DW day the power had not quite peaked at 8000. But the revisit showed MY rev counter was 200 rpm out. This was important as DW use to use the rev counter at 60 mph as a set point for the cost down he now does it from a HT lead reading. The original run up gave a different power curve from the RR Roger uses that had been just recalibrated well the two after this gave very similar results at the wheels.

 

All RR will give different results the factor of air pressure on a day affects the readings anyway. Still lets not get on that debate again there a LOT about it on the 7ns list archive Well what can I say seeing is believing!

 

Actually Roger was a little disappointed in the BHP he has had 209 off one car but that was fuel injected. The carbs were fully overhauled and re-jetted. I changed the silencer for a bigger re-packable Techcraft one, no wadding left in the old one anyway Still not a lot of difference and I was well pleased with the torque think this is slightly higher than the 208 bhp one. But 146 ft lbs off 1700 cc is mega well compatible with a tuned 2.2 litre and better than some 2 litre ones.

 

As to the cost well there is nothing like a Cosworth BD on full chat for sheer sound er better than a fuel injected car and on the RR a few comments on this.

 

One other 7ns list listener had one done afterwards to a slightly different spec and achieved higher outputs. Best have a word with him on that spec... Keith Diggle keith.diggle@uk.gases.boc.com.

 

You can get a lot more see http://www.race-cars.com/utility/coswrthr.htm and look at the Hart engine. Then again you can go for F1 cams and push past 230 bhp but personally I like to drive the car on the road both these specs are really race track only and far too peaky for the road.

 

Well as you said it costs a few bob but you do end up with a virtually new engine. I also fitted a header tank and moved the oil filter to below the carbs.

 

As to the cost well that depends on the condition of you car now one things for sure you will not buy a new one for that price in the same spec at that price. I had another quote very similar to Rogers but his spec and partially the lightened crank was a lot better.

 

Well by going this route you do save on the add on's for say a K series one its still on carbs a very big saving, same engine mounts, rad, Starter motor, alternator etc. Actually I chose to have a new rad the old one was past its sell by date and a bit blocked.

 

Then again its the same down pipes and exhaust ( well mines a bigger now but has the same down pipes and a modified collector box). I think if I did it again I would have gone for a Dave Walker ECU. Then again it took a bit of time to decide that I could not afford the Alli bell housing and NEW alli block. But I would say if you want a Alli block the R500 engine might get very tempting or the VX in full tune. I WOULD like to have a Alli bell housing if anyone has one for sale! Not that it will be fitted until the engine is out again.

 

I also had a Quaife internals fitted in the old 5 speed box, as I was fed up with it. A 3.62 diff would be nice for track days but is only a desired extra. In fact I have still not decided if I really need it. The old one is fine every where except Cadwell Park.

 

If you would like I have spread sheet of all the cars on both the Dave walker RR days that I could e-mail you.

 

One thing I would add is that you would not buy a new BD in this spec for £8000 I take it that includes that nasty VAT. Then again (lots will hate this) but in comparison the K series on fuel injection just sounds ........ best not say it. Well its a very subjective thing anyway.

 

One other thing I did was have BM wheels and A032 fitted the old wheels and tyres were just not up to it. I also went for slotted front disks and green pads. The rears are as original. The BM's are not the same as the R500 in the fact that the inner and outer rims are different to suit the year of the car. The new 22% quick rack soon followed for track days. I already have the Vauxhall race suspension thats been on the car for some time now. At the same time I had the Brookland permanently fitted with a new scuttle the heater was dumped it was leaking a bit and the battery moved to the same location.

 

Oh the car was already dry sumped a Caterham one as an after fit in 1990 but I added a oil thermostat bypass to the cooling coil. This was not related to the revised engine power just use in winter.

 

Well I think that about cover the last 18 months!

 

You do not have to do all that I have done most of the extras is really related to the power and not the particular engine. If I had gone for another engine the same additional mods would have been carried out.

 

As to where to have the work done well its got to be Roger King in my book. If you have comparison quotes as I did make sure they have done it before and the specs the same in the finer details. Mine were not and just a tad more expensive.

 

Oh one forgot its now is unleaded and runs on Super Unleaded. Its really a choice you make on the ECU mapping. If I can not get Super Unleaded I use LPR petrol as it has no Cat. It hates normal Unleaded and should not be used. You could go for just unleaded mapping or LPR the choice is up to you. In my case what was the preferred every day car and was used all year now is more the fun car! Change in how I work caused this.

 

Osborn's put the premium up a bit but not that much if it was fuel injected it would have been more expensive. Silly same top output but more expensive!

 

Well thats about it other than I am really pleased with it, not cheap but more power never is!! Lots of things I have done are not compulsory but just get the best from the car/engine! Its a little peaky but not that much and only shows up now and then on 10/10th on the track. Well 10/10th for me I not saying that I am that fast and at a meagre 19 stone with one of my sons in the car on track days well it lowers the BHP per Ton!! Its seen 135 mph on the old pilots and 14 rims, but that depends on the accuracy of the Speedo. 0-60 well its good but never measured must be about say 4 seconds. The new 13" BM on the rear and 205/60/13 are slightly bigger in diameter so the same should be true.

 

Well if you, like me, LOVE the sound of a Cosworth BD on full chat go for it you do end up with what amounts to a all new engine! Then again.....Quaife seem to have a supercharge one mentioned a couple of moths back in thier News Letter must be the Lard Arse 7n.... might suit me!

 

Oh I am only ever on the lists in the evening and at weekends never have the time at work... what's a lunch hour!!

 

Regards

 

Bill

 

200 bhp, 146 ft lbs, 1700cc Cosworth BDX in a 1988 Caterham with Brooklands, clam wings, Quaife 5 speed box, A032's on non standard BM wheels, 22% quick rack etc etc.

Q 979 CGY

 

 

 

 

 

 

 

[don_g]

Interesting... I'm also building a BDA and would appreciate more info. The head has 1.360" inlets and 1.14" exhausts and, although pretty well used, has been beautifully flowed. I've a new Farndon (where Doug Kidde used to work) narrow journal steel crank and 5.230" rods, on a new AX block.

 

Cam choice sounds pretty wild!!! I need to drive mine on the road (Le Sept etc.) and had thought of L2 inlet and BD3 exhaust on '45's. Ignition will probably be standard lumenition as the whole plot must be interchangeable with the 1600BDR installed in the car at present.

 

I'd appreciate details of your flywheel and clutch... is the flywheel the really skinny 'slotted' one at around 4.2kg and which AP 7 1/4" clutch did you use? As I say, it has to be useable on the road.

 

Any info appreciated - here or on ddongray@compuserve.com

[oilyhands]

Many years ago I ran a BDD, initially with F1 cams which were a little extreme and latterly with an L1/BD3 combination which proved ideal for the road, I run the same combination in my YBB at the moment and find the engine very tractable.

 

Oily

[Simos]

I use L1/L2 cams and am very happy with them. It is proably as far as I'd like to go for a road car but pulls away fine, any probs I have pulling away are invariably carb related. When keeping a low profile in town I go through the gears changing at 2,000 rpm just before the carbs start to complain. I don't claim it's docile or doesn't take any work but within the context of a specialist car of the 7's nature I feel it is acceptable.

 

The upside for that extra bit of work is that at 4,500 it starts to go bananas and at 5,000 it IS bananas until you chicken.

 

I've toured to Scotland, Cornwall and France with them (ok France was Le Mans and it was nuts but hey it was fine going to the supermarche to buy beer...).

 

Cheers, Simon.

[keith d]

Well here's another option. I use L1 inlet and DA10 exhaust cams and find the car much as Simon describes. I use AP Racing 7.25 inch twin plate paddle clutch on a Titan skeleton flywheel and find it OK on the road once you're used to it.

 

Regards

 

Keith

[Bilbo]

My blocks an AX as well. I cracked the first one 711M at Cadwell Park when an engine mount went rather the bar sheared just before it bolts to the block. Not the lightest but elegedly stronger than the 711M and new 711M were hard to get hold of then. A nice alli one would have been a better choice but an expensive one. I stayed with 1700cc with the last rebuild as it still has the original Cosworth pistons.

 

As to the clutch well its not slotted, off hand can not remember AP reference but its a twin plate race clutch.

 

L1/L2 is still fine in town I have a 2.39 1st gear and 3.9 diff changing the later to 3.62 may be an option much later this year.

 

Keith,s, I sure he will not mind this, is more suited to the track. Then again I think that was why he chose it. As I live in the sprawl of suburbia a really in or out clutch would not suit me. If I lived in a more rural are I may have chosen the same as Keith

 

F1 cams thats very peaky but more bhp now I wonder what other combinations there are F1/L1?

 

but in reality going more tham L1 would make it very peaky as Simos may agree?

 

 

 

Bill Ayre

 

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BDX with Brooklands Q 979 CGY

 

[Simos]

Completely agree. I had no problems with L1/L2 driving into sarfeast laahhndan occassionally nor in living in M3/M4 corridor. Obviously it takes more work, but, adds to the charm of the beast I think.

 

I now live in 't country though and tend to do more track than town driving so "if" I changed again it would be something more radical like F1's

 

Cheers, Simon.

[edmandsd]

HT Racing have spent a lot of time testing different cam profiles on BD (and other 2lt 16v engines). They found the BLF17/ Hart 420R profile to be far better than an F1 cam re high output applications - particularly on the inlet side.

[Bilbo]

I your interested Burton have a site that lists a range of cams for the BD's no plug they just happen to a site.

BD3 Fast Road power range 2K - 7K

L2 F/Road,Rally power range 2.5K - 7.5K

L1 Rally/Race power range 3.5K - 7.5K

BLF4 Rally/Race power range 3.5K - 8K

BLF42 Race/Sprint power range 3.5K - 8K

F1 Full Race power range 4.5K - 9K

BLF17 Full Race power range 4.5K - 9K

BLF1/16 Ultimate Race power range 5.5K - 9.5K

 

Looking at these you can see the big jump at the lower end. The trouble is all the references tell you is the power range not the power developed!

 

Well BDR3 is 170 bhp, L1/L2 can get 200bhp, F1 is 220 bhp so what does BLF17/ Hart 420R give you or that never to be used daily on the road BLF1/16 with a mega 12.5 mm of valve lift! off a modest 1700cc? Must be over 240 bhp. The later must sound like the ends have gone until it hits 5000 rpm. Oh I understand you need different pistons to the original BDR ones at over L1 or F1. in fact if you look at thier site all the BLF have a higher lift.

 

Just daydreaming of a 1700cc that gives a R500 a run for its money! Still the cams are only a part of the overall story total waste of time unless its has the valves and gas flowing to suit. Then its BHP verses Torque etc etc.

 

Bill Ayre

 

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BDX with Brooklands Q 979 CGY

 

[edmandsd]

Apparently there exists a genuine 275bhp 1600cc BDA that revs to 11,000 rpm and is fitted in a single seater circuit racer - needs frequent rebuilds so I've heard !

[Bilbo]

275bhp OH GOD 1600cc thats over a 170 bhp/litre and I thought mine was good at pushing 118 bhp/litre

 

So is that at 11,000 rpm is more than the Extreme Race cams on Burtons site! or is that extreme racing or just EXTREME?

 

Well as to the rebuilds there was an article on reliability verses power in CCC a long while back a little gem about an 1100 cc built by Renault, which produced about 1000 bhp lasted 30 short laps of a track. Then it was totally worn out everywhere! (Bit of De Ja Vu here... posted similar to this recently on the 7ns list!)

 

Basically a publicity stunt and was a few years before the article (this may be a bit off in detail it was back in 1988). It must have been hell to get moving! Then again so must 275 bhp off 1600cc... drop cluch at 7000 rpm ?

 

What the artical was saying from memory that over 120 bhp per litre = unreliable but....

 

275 bhp !!

 

 

 

Bill Ayre

 

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BDX with Brooklands Q 979 CGY

 

[oilyhands]

According to some basic maths and taking into account torque delivery it would need to *peak* at a minimum of 11,000RPM to deliver that sort of power from a 1600..

 

Oily

[edmandsd]

Looks more believable if you compare it with the 252bhp, 1500cc Hyabusa engine in the radical that peaks at 9,800 rpm.

 

 

[oilyhands]

I dont doubt that that sort of output is possible but peaking at 11,000 is a tall order.

 

Oily

[Simos]

275 ! Hells donkeys !

 

Oily, I would have thought that 11k per se is very achievable with the right timing (valves and electrics) but that keeping it in one piece is the difficulty.

 

Bikes do it all the time but with lower mass of all the parts... F1 engines turn 15-18k for a couple of hours (or less) although they make their conrods from diamond.

 

At what point (engine sizewise) does the obvious ease of the Yami's and Kwackers to turn 11k+, turn into the difficulty of keeping that 1600 BDA in one piece ?

 

Cheers, Simon

 

On re-reading that sounds pedantic - it isn't mean't to be smile.gif

[edmandsd]

My point Oily was 'Why does the BD need 1200 more rpm to achive an extra 4 bhp per litre' over the 1500cc Hyabusa engine ?

In all reality I'm sceptical about both claims although I don't realistically see any BD giving peak power at 11,000 rpm. Some of HT Racing's 2lt engines are now revving to over 10,000rpm in Portugal but peak power is never much over 9,000 rpm.

[oilyhands]

Dave, I dont know the exact specs of either particularly the valve area.. if you do the torque calculation on the 'busa it shows 135 ft/lb at *peak* which is pretty high, that's not at peak torque but at peak power which is normally at around 90-92% of peak torque, that would make peak torque around 150ft/lb, 100ft/lb per litre... a bold claim.

 

Similarly the BD at 275BHP, if its peaking at 11,000 (which it surely cant be) the torque shows as around 130ft/lb, with peak torque estimated at 145ft/lb, a more believable 91ft/lb per litre. Even so maintaining the torque at that level of RPM given the bore and stroke of the BD must be extremely difficult.

 

Oily

[Paul Turner]

I remember reading a short article in a mag several years ago (may have been Dave Walker in CCC) discussing the ficticious torque and power claims from engine tuners. If I remember correctly there was a simple formula to calculate BMEP (brake mean effective pressure?). There were certain figures given that a 2 valve, 4 valve and full race type engine could realistically achieve together with fairy tale figures being used as examples. I put the figures I had from a realistic power plot of my x-flow and the formula seemed to indicate I had a pretty good engine using the quoted figures.

 

If the above is correct could it prove or disprove the preceeding claims.

 

Paul

[oilyhands]

Paul,

 

I've got a spreadsheet here which uses torque (BMEP and torque are closely related) to predict the RPM requirement for a particular power output given the engine capacity for 2 and 4 valve engines, or to predict a particular output at any given RPM, it gives the *best* that can be acheived and is useful for debunking power claims. The torque per litre for both 2 and 4 valve engines can be set and the spreadsheet will do the rest..

 

Oily

[Peter Carmichael]

Paul,

 

Yup. Torque is the thing you cannot fake with a natasp engine. Torque potential is determined by engine capacity and valve configuration (four valve pent roof etc.). Big power figures can be generated from a small capacity engine by sustaining the torque to higher revs.

 

ISTR that a 4 valve pent roof combustion chamber engine cannot really get beyond 96 lbft per litre. For 2 valve configurations I think the figure is 86lbft per litre.

 

Having done the sums that Oily suggests, I can see it being possible that a 1600 BD could make a 275 bhp peak at or above 10600 - not below that. 10,600 gives torque at power peak as 89% of 96lbft/litre. It would probably be a fairly peaky delivery with a sharp fall off, so you would not expect the limit to be many rpm above the power peak, especially with the risks associated with running up in the stratosphere.

 

The Hayabusa doesn't look right. 252bhp at 9800 would be 94% of 96lbft/litre. 94% is a little suspect. A 252bhp power peak in the range 10,200 - 10,400 looks more believable.

 

Just to be scrupulously fair, my engine is getting its peak of 250bhp at 8700, which gives 88% of 96lbft/litre. it first makes 249bhp @ 8400, which is 91%. This merely suggests that the numbers never stray that far from this rule of thumb when you are in the realms of very well developed natasps.

[Paul Turner]

Peter

 

Thanks, that's made lunchtime more interesting. Using your methodology my x-flow worked out at 78% of 86 lbft per litre, the Zetec I have just fitted using a realistic expected power output works out at 78% of 96 lbft per litre, not much of an improvement there then.

 

A sprinting friend of mine used a 1600 BD? in his Caterham that was sourced from a Formula Pacific car (short stroke with F1 cams). For several years it was pretty entertaining watching him and his father wrestle with the car as it came suddenly on cam at extreemly high revs on road tyres. Personally I felt that a change to softer cams would make the car ultimately faster by making it far easier to drive and eventually they did this, probably more out of necessity rather than choice as a rebuild was due. Afterwards their times fell and ultimately so did class records, if I remember correctly they lost probably 40 hp. The revs/gearing combination necessary to exploit the wafer thin power band were not possible to achieve in a Seven even with their 4.40 diff.

 

Paul

[don_g]

Thanks for the info, on cams in particular, and I guess it's a toss-up between L1/BD3 or L1/L2 with, as ever, the choice being between oomph and driveability.

 

I've a couple of BD3's lying around anyway... so price also enters into the equation!

 

Clutch choice - twin plate or single plate 71/4 AP. Twin plate appears to be the favourite, and seems to be more of most things... more weight, more cost, and more wear. Single plate CP4111A ORAnge is used by many and offers 205'lb with a high release load of 222daN; Twin plate CP4112A GREen offers 197'lb and a less knee-trembling release load of 154daN. I'd value your advice, and also on the merits of three, four or six paddle driven plates. And as for release bearings...

 

Your assembled wisdom eagerly awaited...

 

 

[Roger King]

You can probably reprofile your BD3 to an L2. This is what we did with both Bilbo and Simos, but you won't be able to do the same to get an L1 so you will have to buy a new cam there. The repro job is much cheaper.

 

Go for the twin plate. Although the specification on a twin plate of this type only permits half as much wear before replacement as on a single plate, the actual wear rate is generally only about 1/4 of that experienced with a single plate.

 

 

I should clarify that - the total permitted wear is the same as for a single plate clutch. Therefore each plate is allowed only half as much wear.

 

Personally, I'd go for a 4 paddle cerametallic if road use is envisaged, but this is more expensive and a bit heavier than the sintered type.

 

Edited by - roger king on 7 Feb 2002 22:38:35

[Bilbo]

Hi all

 

Well I have to say I would hate to drive my car with a 4.4 diff its not that a tight rev band to drive but a change from the 3.9 to 3.62 would make a difference. This would let me keep more on the cam for a given speed.

 

This really only applies to when the cars 2 up on a track with hills (Cadwell), with my meagre 19 stone and my sons 11.5 stone in the car. The other option is to lower the cars overall weight so far its dumped 7 lbs and with a little luck it will get rid of another 28 lbs by the end of this summer... I am on a diet! Cheaper than a diff change!

 

The cars hit over 130 mph, still with a bit to go, on the Speedo not claiming its accurate, so a 3.62 diff would lower than a bit but even on a track how many can get over 120 mph on 200 bhp you need a long straight after a fast bend. Tracks like Cadwell are so much more fun.......... go as often as I can.

 

As to the clutch well I am happy with the twin plate, RK explained the choice when the engine was rebuilt. Its not all in or all out which is great on the road. Having a close ratio box with the 2.39 first is much more drivable than the standard box with the 3.39 first and big rpm drop into second (think 3.39 correct?).

 

As to the difference between the 170 bhp to 200 bhp well a lots been written on the claim of 170 bhp. Mine had a dyno when built which showed 172 bhp. However the difference when driving the car would make question that reading. One thing in standard spec the Caterham 7 BDR spec gas flowing is poor I had mine redone a tad but it was minor in comparison to the amount done now.

 

Oh anyone want a BD3 inlet cam or valves?

 

Bill Ayre

 

1988 200 bhp, 146 ft lbs, 1700cc Cosworth BDX with Brooklands Q 979 CGY