Cossflow versus BDA

[eric]

Hi everybody,

 

Who knows the differences between 150 HP in a crossflow

and 150 HP in a 1600 BDA ?

 

Behind the wheel I mean, not from the point of view of your

bank account manager

 

thanks to all point of view

[Roger King]

From behind the wheel there isn't a lot of difference. Assuming that both the power outputs are real, the BDA is likely to have a slightly higher torque figure (assuming that they have the same capacity). If the Crossflow is of larger capacity, it will probably have the superior torque figure.

 

The real difference lies in the potential for further tuning. The BDA is in a different league for this and can be taken well into the 200s.

 

Edited by - roger king on 10 Nov 2001 15:02:10

[EFA]

The main difference is the power the BDA has in terms of wallet emptying.

 

With 200bhp easily obtained from a std VX with a few bolt on goodies (repalcement cost £600) is it sound finacial sense to go the BDA/BDR route and buy an engine where a bottom end failure could easily cost multiple 000,s

 

 

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

[Simos]

"Heritage" is (relatively) expensive as the Westy brigade keep telling us... and you rightly defend.

 

Although I don't believe an all steel BDA bottom end is more expensive than an all steel Vaux although I concede a head will be. Please lets not go down that road again smile.gif

[EFA]

You dont have to have a steel bottom end in a VX to get 250bhp though......

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

[elie boone]

I agree that a BDR is not sensible ( i know all about it )but it whas a teenagers dream to have one. If you buy one i think it is all about the myth that these engines have. If i say that i have a BDR in my seven, everybody that new the old rally Escorts will say "must be fast" but its only has 170bhp.Compaired with a 220 or even 250bhp it is a slug.( for the same weight )

[hugh]

financially a BDA/G etc makes no sense but do they sound the dogs! my mate races a HSR chevette with a BDG all steel internals, and alloy block , its self built, expensive +£10000 it goes like a train and anyone who hears it loves the sound, its nearly as light as a K series and easily as powerfull,i reckon you pays your money and you makes your choice, but you can,t beat the bark of a BDA/G,though not an engine for the faint of wallet.

[oilyhands]

I'm told that Leonardo Da-Vinci could have made a better study of The Mona Lisa had he used a modern SLR camera with correct lighting and speed of film. Somehow I think I prefer the original hand produced fragile original complete with all it's frailties and foibles.

 

Same could be said for the BD and the Vx.. :-)

 

Oily

 

Edited by - oilyhands on 12 Nov 2001 23:09:00

[Roger King]

Actually, tuning a BDR isn't really any more expensive than any other 16v engine. The real killer cost is in the purchase of the original engine. Once you've got this, components such as cam followers, cam regrinds, valves, pistons, etc are of similar price.

 

The real exception to this is that the standard BDR crankshaft will not stand for big outputs, so it is necessary to go to steel bits.

[elie boone]

I still have the std. crank sad.gif but maybe in the future get some steel biggrin.gif

[Simos]

Ellie,

I had the std crank for 8 or so years and 20,000 miles+. All were great fun and twas always a good performer. Lately I changed to steel and changed the cams (L1&2). It now does stupid revs, sounds fantastic and keeps up with most things on a trackday (many supposed 2xxhp HPC's have been embarrassed to not overtake the H plate 1700 Supersprint in front of them teeth.gif or indeed stay with it...)

 

Not cheap but as Roger says, not much different to Steel-ing, camming and followering any other engine. What premium for heritage ?

 

How much is a Minister 230hp K anyway... is it really a "cheap" engine ? I don't know, I doubt it else why is an R500 35k?

 

How much is a 230hp Swindon Vaux from Swindon ?

[elie boone]

Simos, What chassis do you have and how much BHP ? some pic. ?

[Barry H]

Forgive my ignorance but in this thread BDA, BDR and BDG seem to be used interchangeably or am I misunderstanding it?

 

Secondly, given that the BDA was based on the X-flow block, are any bits still common to both?

 

Thirdly, what is the difference in weight between say, a k series and a BDA?

 

And finally, what modifications would be required to fit a BDA in place of a X-flow?

 

Barry

[Dave H]

For some good stuff about how/where/when etc BD? see here

[Roger King]

The BD series of engines are all related. The first version was called the 'A', hence BDA - Belt Driven A-series (not in any way related to the mini engine and there is some arguement that the A stands for Anglia).

 

All subsequent versions has different suffixes to denote the different version. In some cases this is logical, as in R for Road, in some cases they just seem to have used the next available letter.

 

Usually, when people refer to a BDA, they are using it as a generic term to cover any one of the variations, although strictly speaking it means the original 1600ccm version.

 

There have been all sorts of variations - changed capacity, turbocharged, different valve sizes, aluminium block, etc, etc. At this point you will probably expect me to reel off all the different suffixes and what they mean - you must be joking! I do have this information somewhere, but I don't carry it all in my head.

 

some of the better known ones are:-

BDR, as used by Caterham

BDT, turbocharged rally group B engine

BDG, naturally aspirated rally engine

 

Contrary to popular legend the BDG does not have an aluminium block. It was a special cast iron block, but Brian Hart developed an aluminium version for his own purposes and this was adopted for the works rally cars - to most people this is what they mean when they say BDG.

 

All of these engines are based on the Crossflow bottom end, but to a greater or lesser degree this has been changed to suit the use. The top end engines are effectively purpose made competition units.

 

To swap a Crossflow for a BDR, you would need a new exhaust, some plumbing and a few other odds and sods (I just know that someone will mention something major that I have forgotten). Engine mounts, oil system, bellhousing, etc all remain essentially the same. You can even convert your original Crossflow into a BDR with the correct parts - it'll cost you though.

 

[oilyhands]

Try this for an almost complete/correct definitive listing from FVAs to YBs here.

 

Oily

[ross]

i agree with simos' comments:

 

"What premium for heritage ?

How much is a Minister 230hp K anyway... is it really a "cheap" engine ? I don't know, I doubt it else why is an R500 35k?

How much is a 230hp Swindon Vaux from Swindon ?"

 

which car n/a engines exist which have the potential to 150+bhp per litre are cheap??

i have an alloy block bdg?/2.0 alloy bda powered car which i do not use as much as i would like - but i have not had to do anything to the engine since i bought the car from this forum in july 2000 (i hope i am not tempting fate here) - also a good spec bd (steelcrank etc) car seems to hold value - i paid the same for my car as the previous 2 owners - and i could sell the car today for what i paid - which is irrelevant but refutes claims that high spec bd's are a money pit - i'm sure dave edmunds could recover his build costs on his bdx powered "R700" if he wanted to

 

re:150bhp x/flow or 150 bhp bd - i had a 150 bhp x/flow - as my first 7 and really enjoyed it - but sound of a bd which can rev due to steel crank/decent cams etc is worth the additional cost for the noise alone! goes well too..cost differential is justified by your emotive perception of heritage/severity of your addiction to power outputs which are irrelevant on the road/relevant for trackdays/very quiet roads! - in real terms i do not get more enjoyment from my bd than i got from the crossflow - you pay your money and you take your choice - my neighbours prefered the x/flow - i was less cautious/spent less time warming engine up in morning - and it was quieter..

[Barry H]

Dave, Roger & Oily

 

Thanks, that was a tremendous response - and has certainly given me something to think about.

 

Expect more questions shortly!!!

 

Barry

[Roger King]

Bugger!

[Graham Perry]

Barry H, Surely you are not thinking about moving up a class at Curborough ? The next class up is even more competitive (read expensive) than class 2.

[Simos]

Elie,

I don't have any web-able pictures at present partly through sloth most ly 'cos it's nothing spesh to look at. When I bought mine there was only a supersprint to choose from with the Vaux HPC waiting in the wings.

 

I generally call it a SuperHeavy (600kg maybe) 'cos of all the cast iron, heater (wife won't ride without) etc etc.

 

It's not in anyway a fancy car as some are on this forum but it has over 30k miles on the clock.

 

I second Ross' comments on costs, I've had mine over 10 years and have only fixed minor things and only when other works were done.

 

I've upgraded only once (steel internals) if you don't count unleadeding which was due to the chancellor/EU.

 

If you discount the upgrade as it was my choice then it's cost me virtually nothing and done 30k miles/10 years... nuff said.

 

And it still splats most things on a trackday teeth.gif

 

Drive and live, Cheers, Simon.

[elie boone]

Simos, 600 kg this must be a joke, i hope to see less than 480 kg. Only the engine is cast iron all the rest is ali. and no de-dion but a live axle.

[TimNeill]

Eric

 

Don't be put off by people who talk about 'fragile' BD engines. If it's been built right, you'll be fine. My 7 had a BDM 1700 all steel engine with an aluminium block, built by Geoff Richardson - he is absolutely the best BD builder, bar none.

 

The engine produced 200 bhp at 8,200 (146 ft/lbs torque) and was an absolute kitten to drive. It survived goodness knows how many violent and brainless standing starts at speed events, and some not at speed events, and never missed a beat. I have had 1700 crossflow Sevens up to 150 bhp and there was no comparison - the Cosworth was two creatures: a docile mini in town and a banshee over 7,000.

 

I have droven several Sevens with 240+ bhp and whereas they were awesome in brute strength they have all felt like tractors to me (sorry Arnie and Alex). My car was 462Kg and the steering was wonderfully light in comparison.

 

The major difference of course between a hot crossflow and a BDA/R/M engine is one of options: you could if you wanted take the Cosworth to 2 litre and 250 bhp plus and with that light weight. And so you can with a Rover engine too.

 

But after all that there is this magical, nostalgic element too . . . the looks, the sound, the link with the past. I suppose it's the same unscientific, sentimental value judgements we make about Zippo lighters, Nikon cameras, Primus stoves, vinyl records over CDs etc. In my case, ironically the expensive bit was the ancillaries which Caterham provided: 3 fuel pumps, 2 alternators, 2 starter motors, 2 batteries, 2 gearboxes.

 

Finished rambling. Buy a Cosworth engined Seven and good luck!

 

Tim Neill

Temporarily without a Seven and obviously very sad

 

 

 

 

[Barry H]

Graham

 

Just thinking and looking at the alternatives.

 

You never know, one might suddenly appear in the For Sale section and I have to ready for that eventuality!!!!!!

 

Seriously though, if I can re-use my present steel crank and rods and if a BD? will fit easily into the hole left by a departing X-flow, it does have to be considered.

 

Moreover, I understand that alloy blocks (new) are available for the BDG and can be brought back to 1700 BDR spec. (if you are very rich)

 

From what I hear, parts are likely to be available for years to come ,not least because of the growing interest in historic racing.

 

I wish I were as good a salesman to others as I am to myself!

 

Barry

[Casbar]

Are the BD engined cars usually running with a De axle or a live axle. Thinking about it, I suppose all that power would be too much for a live axle (Ital)