30 replies to this topic

[mab01uk]

Which book is that photo taken from?

 

 

The A-Series Engine - Its First Sixty Years
by Graham Robson
Published 20/10/2011 by Haynes

"Built from 1951 to 2000, BMC's A-Series engine was a remarkably successful, versatile and invaluable power unit that far outlived its original projected life. Not only did it power road cars as varied as the Austin A30, the Mini and the MG Midget, but it also found use in world-class race and rally cars, record-breaking special machines, light commercial vehicles and even tractors. This fascinating illustrated book chronicles the full history and achievements of this remarkable engine."

Edited by mab01uk, 30 August 2020 - 02:23 PM.

[Mite]

The A-Series did well to eventually achieve 1275cc displacement in production bearing in mind it originally started life in 1952 as 803cc......but the high cost of the development of the A+ for the Metro (Total cost of A+ development and retooling programme: £30 million) has made little sense to me over the years for what was achieved, when the money spent could easily have produced a 5-speed gearbox upgrade for the Mini and Metro which were to be in production for many more years and with motorway driving by then an essential part of most drivers motoring needs.

Engines : A-Series:-

https://www.aronline...gines-a-series/

 

Interesting extract below from an AROnline 'Mini Development in the 1970's' article about BL's research into the OHC A-Series engine:-

"In April 1982 the Mini was given higher gearing to make it more economical, but this did nothing for acceleration, and the car lost a little of its buzzbox characteristics. The fact that the ancient A-Series engine could cope with up-gearing was a tribute to its remarkable torque characteristics, even in its tamest form.
And that brings us to the subject of why the A-Series engine was never radically re-engineered to modern standards. Was it a matter of cost or were there other reasons?
Back in the 1970s BL had embarked on projects to develop overhead camshaft versions of both the A- and B-Series engines. The reason for this was that MG used both engines and as they exported to the USA where stringent anti-emissions legislation was in force, it was paramount that BL’s existing engines were made more efficient to enable them to remain both legal and competitive by using the more efficient emissions friendly overhead cam layout.

In the end the OHC B-Series evolved into the O-Series engine first seen in 1978, while converting the A-Series to the overhead cam layout proved to be a technical cul-de-sac. The immediate problem of continuing to sell the MG Midget in the USA was solved by replacing the 1275cc A-Series engine with the 1493cc Triumph engine also used in the rival Spitfire. But an OHC A-Series could be used in the ADO88 and other BL cars. In the event eleven prototype overhead cam A-Series engines were built in 1975 using Cooper S blocks in capacities of 970cc, 1097cc and 1275cc. The engines used aluminium cylinder heads.

The engineers obtained the following performance figures for OHC Minis:

970cc: OHC 59bhp @ 6750rpm, 51lb ft @ 5250rpm
1097cc: OHC 72bhp @ 6500rpm, 64lb ft @ 5000rpm
1275cc: OHC 84bhp @ 6750rpm, 80lb ft @ 4500rpm

The above figures look very impressive, and a bluff-fronted Mini Clubman fitted with the OHC 1275cc engine and twin HS6 SU carburettors could reach 100mph. It would be easy to accuse BL of another missed opportunity. But a look at the comparative figures for the existing overhead valve engines reveal another story. For a direct comparison first we will use the three Cooper S engines and then the standard tune single carburettor engines seen in the mainstream production Minis.

Standard OHV Mini engines:

970cc: OHV 65bhp @ 6500rpm, 55lb ft @ 3500rpm
1071cc: OHV 70bhp @ 6000rpm, 62lb ft @ 4500rpm
1275cc: OHV 76bhp @ 5800rpm, 80lb ft @ 3000rpm
998cc: OHV 38bhp @ 5250rpm, 52lb ft @ 2700rpm
1098cc: OHV 45bhp @ 5250rpm, 56lb ft @ 2700rpm
1275cc: OHV 54bhp @ 5250rpm, 67lb ft @ 2500rpm

Converting the A-Series engine to overhead camshaft simply pushed the peak torque further up the rev range and actually caused more problems than it solved. One of the great virtues of driving a Mini is its remarkable ability to pull top gear at low revs, something that was exploited by Austin Rover and later Rover when the car was up geared.
An overhead cam A-Series engine would have been torque shy where it mattered in everyday driving and that was indeed the case with the 100mph OHC Mini Clubman. The modern solution for the lack of torque where it matters would be to add more gear ratios, but BL’s engineers decided that a reliable revised transmission in sump gearbox was not feasible. Therefore the decision was taken to opt for the A+ programme. BL had already burnt its fingers with the OHC E-Series engine. The E-Series had been intended to supplant the B-Series, but its lack of torque resulted in the old B-Series going into the Marina and Princess, and even the O-Series was a disappointment. BL would not make the same mistake again."
http://www.aronline....history-part-2/

 

Let's operate from the premise the Mini, Metro and others did merit a 5-speed gearbox to better take advantage of the production A-OHC engine, either via the Issigonis in-sump layout (by way of Jack Knight's work on the experimental 5-speed being approved - plus 5-speed AP Automatic project between Jack Knight and Keith Gerrard of Bushey) or the now universal end-on layout.

 

A 1372-1380cc version of the 84 hp 1275cc A-OHC would approximately put out about 90 hp.

 

Where things get a bit confusing would be how to extrapolate how much more a hypothetical 1372-1380cc A-OHC was capable of putting out above 90 hp in naturally aspirated form against the following:

 

- The 1275cc MPi engine with factory-approved 1999 Si pack (Tpi) by John Cooper was putting out 90 hp

 

- The 1275 A+ Turbo about 94 hp (allegedly detuned from 120-130 hp to preserve gearbox in MG Metro Turbo)

 

- An MG-badged Authi Victoria ADO16 prototype featuring a 1275cc twin-carb engine putting out 83 hp or only a shade short of the 84 hp in the 1275 A-OHC 

 

With the existing in-sump gearbox it is possible a 1372-1380cc A-Plus or A-OHC would remove the need for turbocharging in more potent versions of both the Mini and Metro, even if some modification and de-tuning would still likely be needed.

 

With a 5-speed gearbox (be it an in-sump or end-on layout), would roughly guesstimate turbocharged versions of the 1372-1380cc A-Plus or A-OHC being a match for the 118 hp Renault 5 1.4 GT Turbo and 118 hp Fiat Uno 1.4 Turbo. Which IIRC is said to be about the limit of the standard 1275cc naturally aspirated engine before further modification is needed (seen others put figure between 110-115 hp and 130 hp) despite reading of experimental MG Metro Turbos reaching 130 hp (unless the Metro Turbo engine was significantly strengthened compared to the existing 1275cc engine for the 120 hp limit to be less of an issue).

 

Outside of the Mini and Metro it is inevitable the 1372-1380cc in whatever iteration would be detuned in order to not encroach on the territory of bigger engines in other models such as the 1.7 O Series. 1.5 E Series (itself capable of 83 hp via Downton tuning) and 1.6 R / S Series, putting out anywhere from above 60-64 hp to below 76-80 hp depending on the model in question.

Edited by Mite, 30 August 2020 - 07:14 PM.

[hazpalmer14]

Making more power in the metro turbo is simply a case of removing the ecu that limited the boost to 4psi unit 4k rpm and then it was 7psi. You could wind up the boost a little if the fueling and ignition timing are suitable without the need to change much else. That's probably where those figures come from, but like you say they want things to last for warranty reasons. That's why boost was limited until 4k rpm to help ease the amount of torque put through the gearbox.

[Mite]

Making more power in the metro turbo is simply a case of removing the ecu that limited the boost to 4psi unit 4k rpm and then it was 7psi. You could wind up the boost a little if the fueling and ignition timing are suitable without the need to change much else. That's probably where those figures come from, but like you say they want things to last for warranty reasons. That's why boost was limited until 4k rpm to help ease the amount of torque put through the gearbox.

 

Understand, so both the MG Metro Turbo and ERA Mini Turbo would have been easily capable of reliably achieving an output closer to the 120-130 hp figure for the turbocharged A-Series engines had a suitable gearbox been available?

 

Am also assuming a hypothetical 1372-1380cc Turbo would have put out similar figures to what an unrestricted 1275cc Turbo was capable of reaching with improvements elsewhere, roughly in line with what other rivals featuring similarly sized engines were doing. Since the 140+ hp figure of a hypothetical 1372-1380cc Turbo would have been too excessive in the road-going Mini / Metro outside of say a mid-engined 1.4 turbo MG Metro rally car challenger (below the 6R4) to the mid-engined Renault 5 Turbo or some RV8 inspired equivalent of the MG Midget.  

Edited by Mite, 31 August 2020 - 10:52 AM.

[hazpalmer14]

Making more power in the metro turbo is simply a case of removing the ecu that limited the boost to 4psi unit 4k rpm and then it was 7psi. You could wind up the boost a little if the fueling and ignition timing are suitable without the need to change much else. That's probably where those figures come from, but like you say they want things to last for warranty reasons. That's why boost was limited until 4k rpm to help ease the amount of torque put through the gearbox.

Understand, so both the MG Metro Turbo and ERA Mini Turbo would have been easily capable of reliably achieving an output closer to the 120-130 hp figure for the turbocharged A-Series engines had a suitable gearbox been available?

Am also assuming a hypothetical 1372-1380cc Turbo would have put out similar figures to what an unrestricted 1275cc Turbo was capable of reaching with improvements elsewhere, roughly in line with what other rivals featuring similarly sized engines were doing. Since the 140+ hp figure of a hypothetical 1372-1380cc Turbo would have been too excessive in the road-going Mini / Metro outside of say a mid-engined 1.4 turbo MG Metro rally car challenger (below the 6R4) to the mid-engined Renault 5 Turbo or some RV8 inspired equivalent of the MG Midget.

I'm not sure on those figures. I think you could push 110hp on a standard metro turbo set up. You would have to check on the turbo minis forum. Most people when they start to creep the boost up a little will want to add an intercooler etc so that then changed the whole set up, and it also gives you that saftey margin.

[Mite]

 

 

Making more power in the metro turbo is simply a case of removing the ecu that limited the boost to 4psi unit 4k rpm and then it was 7psi. You could wind up the boost a little if the fueling and ignition timing are suitable without the need to change much else. That's probably where those figures come from, but like you say they want things to last for warranty reasons. That's why boost was limited until 4k rpm to help ease the amount of torque put through the gearbox.

Understand, so both the MG Metro Turbo and ERA Mini Turbo would have been easily capable of reliably achieving an output closer to the 120-130 hp figure for the turbocharged A-Series engines had a suitable gearbox been available?

Am also assuming a hypothetical 1372-1380cc Turbo would have put out similar figures to what an unrestricted 1275cc Turbo was capable of reaching with improvements elsewhere, roughly in line with what other rivals featuring similarly sized engines were doing. Since the 140+ hp figure of a hypothetical 1372-1380cc Turbo would have been too excessive in the road-going Mini / Metro outside of say a mid-engined 1.4 turbo MG Metro rally car challenger (below the 6R4) to the mid-engined Renault 5 Turbo or some RV8 inspired equivalent of the MG Midget.

I'm not sure on those figures. I think you could push 110hp on a standard metro turbo set up. You would have to check on the turbo minis forum. Most people when they start to creep the boost up a little will want to add an intercooler etc so that then changed the whole set up, and it also gives you that saftey margin.

 

 

A feasible reliable 110 hp in turbocharged form does not sound too bad considering it is without an intercooler yet not that much considering the limit of the naturally aspirated 1275cc is said to be about the same up to 120 hp at most, which makes one question whether a hypothetical uprated production A-OHC (with suitable 5-speed gearbox) in 1275cc or 1372-1380cc form would almost negate the need for a turbocharger.

Edited by Mite, 09 September 2020 - 12:19 AM.

[Mite]

Recently discovered the the Cooper 1400 conversion mentioned both here and here from around 1992, which put out 115 hp for the carb models and 108 bhp for injected models.To what extent would hypothetical production 1372-1380cc A-Series engines have been able to put out similar figures at a significantly lower cost compared to the 1400 Cooper conversion that was said to have entailed a new block (along with other mods) and cost about as much as the car itself?

 

Is it known what the exact displacement of the 1400 Cooper conversion was?

 

 

[Curley]

I suspect 1400 is a loose suggestion of CC. The 1275 was called a 1.3 so why wouldn't a 1380 be called 1400? I very much doubt JC was making custom cranks - happy to be shown wrong - It might be possible to gain the extra 20cc from custom 73.5mm pistons on a 81.3 stroke. But that would also mess with compression.

 

[Mite]

Thought as such on the displacement not being literal.

 

From the PDF link the modifications and components of the 1400cc conversion include rebore to 1400cc (likely non literal), forged racing pistons, a new Stage III cylinder head, new specially designed camshaft, twin 1.5inch SU carburetors, a new large-bore exhaust manifold and system, new 3.44.1 final drive, a set of high-lift roller rockers, oil cooler and more.

 

A 1372-1380cc version of the factory-approved 90 hp 1275cc MPi in the 1999 SI pack (Tpi) would roughly equate to around 97 hp, which is not completely far off the 108 hp injected 1400 Cooper conversion (even if a bit more work would be needed to come close to the 115 hp carb 1400 Cooper conversion). 

[mab01uk]

Mini Super Power - CCC - David Vizard:-

http://www.theminifo...c-david-vizard/

Edited by mab01uk, 20 September 2020 - 03:13 PM.

[Spider]

These '1400' engines are interesting for sure, especially those from John Cooper Garages, however, if I can just mention here, these I feel have strayed some way from the original 'proposal' of what could have been done in production. These weren't complete cars, but kits offered for fitting to your car and so the warranty, if any, would have rested with Coopers in this case.

 

The factory's chosen route for higher powered engines wasn't to go to a bigger unit, but to Turbo it, and I'd say, potential warranty claims would have factored in highly in that decision as well as the ability to mass produce them, where a complete power unit would have been assembled in 4 to 6 hours as opposed to engines that have been bored closer to their outer limits, that would need several days to assemble and with a higher reject rate and I dare say, likely a high warranty claim rate.

[Mite]

Mini Super Power - CCC - David Vizard:-

http://www.theminifo...c-david-vizard/

 

While 1430 engines are a thing, have doubts it could be productionised unlike the 1372-1380cc engines which were relatively more feasible had the A-Series production line been updated and modernized earlier on.

 

The 1442cc Simca Poissy and 1438cc Fiat 124 OHV / Twin-Cam as well as motorsport focused 1430-1440cc Renault Cleon-Fonte engines are what immediately come to mind in terms of closest comparisons, yet a 1430 A-Series (likely a 1428cc in practice) would have only been useful in the Group B segment for turbocharged displacing 1428cc or below with a weight limit of 820kg (like the Renault 5 Turbo). 

 

Do not get me wrong. Would have personally preferred a viable enlargement to 1485-1596cc as brought up in Vizard's book though realise it was simply not possible if 1372-1380cc was likely the absolute limit the production A-Series was capable of in better circumstances and with modernized production line earlier on. Concede it would have been best left to a linear successor of similar size (albeit significantly lighter) that largely carries over the bore / stroke of the A-Series with scope for further enlargement to desired limit as well as other useful applications.

 

These '1400' engines are interesting for sure, especially those from John Cooper Garages, however, if I can just mention here, these I feel have strayed some way from the original 'proposal' of what could have been done in production. These weren't complete cars, but kits offered for fitting to your car and so the warranty, if any, would have rested with Coopers in this case.

 

The factory's chosen route for higher powered engines wasn't to go to a bigger unit, but to Turbo it, and I'd say, potential warranty claims would have factored in highly in that decision as well as the ability to mass produce them, where a complete power unit would have been assembled in 4 to 6 hours as opposed to engines that have been bored closer to their outer limits, that would need several days to assemble and with a higher reject rate and I dare say, likely a high warranty claim rate.

 

Would have to agree regarding the John Cooper 1400 conversions, at the same time there must be something valuable that could be drawn from the conversion to be potentially carried over to hypothetical productionised 1372-1380cc A-Series engines. 

 

The biggest question mark would have to be the tuning potential of a production 84 hp 1275cc A-OHC engine in tandem with earlier 1372-1380cc enlargement, compared to what was already achieved with the factory-approved 90 hp 1275cc MPi in the 1999 SI pack (Tpi). Maybe the former in 1372-1380cc naturally-aspirated form could have had much easier time of breaking the 100 hp barrier (towards 108 hp 1400 Cooper conversion levels) unlike the latter (that would likely only produce about 97 hp in 1372-1380cc form), though could still see the latter together with turbocharged versions being viewed as a preferable solution over the A-OHC option even if sticking with OHVs would have been viewed as increasingly unfashionable from the 1980s onwards (however the A-Series was not unique in that respect when one considers the Renault Cleon-Fonte, Simca Poissy and even Ford Kent-derived engines, etc).

Edited by Mite, 20 September 2020 - 09:41 PM.

[Curley]

Everyday is a school day 73.64mm piston on a 84mm stroke

 

Mini Super Power - CCC - David Vizard:-

http://www.theminifo...c-david-vizard/

[Mite]

 

Everyday is a school day 73.64mm piston on a 84mm stroke

 

Mini Super Power - CCC - David Vizard:-

http://www.theminifo...c-david-vizard/

 

 

An 86mm stroke would have pushed displacement out to about 1465cc, yet David Vizard also said in his book that were cost no object a 1480 engine via a 74mm bore x 86mm stroke would have offered the best compromise between a 1400 and a 1600 (via a 74.7mm bore x 91mm stroke) engine for rallycross (being more than a match against the 1600 engine with a well-built 1400 in turn being only marginally slower and considerably cheaper then the 1480).

[paulrockliffe]

The hypotheticals are interesting for sure, but I do think the engine development that was done was really the limit of what made sense at the time, and certainly if the accountants got involved.  I can't imagine MPI buyers that really wanted an extra 10-20bhp were anything other than a minority at the time and with the age of the design, it would have been a very significant investment.  I would guess it was firmly in 'put a different engine in' territory by then.