When is enough bhp enough?

[vincereynard]

Or buy a Porsche Cayman?

[Spyder fan]

Or buy a Porsche Cayman?

Wouldn't you prefer a Boxster Spyder?


http://www.porsche.com/microsite/boxste ... /uk.aspx#/


Regards from
The Phantom Raspberry Blower of Old London Town

[poppy]

Any time when you get less than 10 pounds per horse power, you will be getting serious performance. An Elan with 175 hp, even with a 180 lb driver is approaching that number.

Interesting formula, and thanx's . Every response has given me something to think about..and thank you all. I certainly do not wish to own a "hot rod" or would not be looking at an plus 2 in the first place. Nor do I want to miss- direct my budget. By that I mean... reality is that I will buy a plus two, it will come with a twin cam, that needs a refresh in the engine department amongst many other areas to be within my total project budget ( circa golf r with sensible options). Assuming the head is o.k. a slight power increase might make sense at the time of re-build or go down the duratec conversion route and sellon the twin cam. Which although less pure I am the first to admit , might be more cost effective. I am at this stage sounding out all options. With decisions, yet to be be made.

So using your interesting formula of "<10 lbs / 1 bhp is fun", driver weight excluded, kerb weight only , have come up with this.... (source carfolio.com. ) This is only one side of the coin, as tractive force, by the plus 2 s tire size or lack of is another, like wise torque etc. Which is why I mentioned traction in my O.P. Values in brackets are the bhp that a plus 2 would "theoretically have to produce to be equivalent".

So.....

LOTUS

lbs / bhp
Elan Plus 2 s 130 15.11....... 1905 lbs / 126 bhp...
Elise ( 2010) 14.40 (135)
Esprit (1975) 12.40 (153.62)
Elan Sprint ( 1971) 12.02 (158.48)
Exige S (2011) 0 6.90 (276.08) bhp.


Period Correct Others

E Type 4.2. 2+2 (1966) 10.35 (184)
M.G.B. roadster GT V 8 (1973) 17.44 (109.23)bhp

Newer Things...

Morgan Plus 4 (2012) 13.52 (140)
Golf Gti ( 2017) 14.67 (129.85)
Cayman 718 s ( 2017) 8.65 (220.23)
Reliant Robin 850 (1981) 24.44 (77.94) bhp


I am sure the likes of John Wilcox et al could take a twin cam with a serviceable head to (1975)Esprit levels at a modest cost, but cost of down engineering to Robin levels successfully would be another matter.

[vincereynard]

Wouldn't you prefer a Boxster Spyder?

http://www.porsche.com/microsite/boxste ... /uk.aspx#/

As long as its a Stuttgart Spyder, that would be fine.

A Peterborough Spyder would have a trailer hook attached, probably by pop rivets and sticky tape. Give you somewhere to put all the bits that fall off.

[Grizzly]

I agree with Alan, Peak HP is a waste of time unless your racing (staying high up the power band) the trick to getting the best road car is to get as much area under the curve as possible (aim for as much low / mid range power as you can and forget peak to a degree) this is often difficult with an NA engine as most who tune are doing it for Racing so Big valve heads and high lift cams often rob low end to increase high end.

So be careful what you wish for.

[rgh0]

Certainly 190 to 200 hp from a 1600 twin cam will be a high revving engine with most of its torque and power in a narrow band above 6000 rpm. But it is possible to build a 160hp 1600 twin cam with great flat torque curve and a usable power band for the road. A 1700 twin cam will be even better

cheers
Rohan

[elan66]

Hi Rohan's forgotten more than i will ever know about tuning twin cams,but i do know that building a high power twin cam is not cheap and they need to be revved more than a zetec to get the power.If you go the zetec route (duratec not really that feasible as exhaust/induction wrong way round) it will work out dearer than doing a rebuild to the twin cam unless you can get 2nd hand items fabricate bits yourself, get a few bargains etc.
List for zetec; engine silvertop (mondeo) or later blacktop(focus)
1.8 ltr flywheel ,pinto clutch pressure plate
granada starter motor
alternator and brackets( and idler puley and belts blacktop)
throttle bodies or webers(can use originals but new with 5 hole progressions better)
inlet manifold
different sump
ECU
water rail kit
various water hoses
cams
engine mounts
cut out to chassis
If you start adding it up someone like craig beck will build a great engine for the cost of that lot BUT if the engine goes bang it will cost a lot less to replace a zetec if you have allready done the conversion and the zetec will take a lot more abuse than a twin cam (9 times out of 10) At the end of the day it is down to personal choice,i havegone down the zetec route and having had a race prepped elan the extra grunt of the zetec should replicate the expeirience but with more reliability when i do track days.If you can get a ride in a zetec powered elan it may make it easier to decide,all i know is the zetec owners i know would not rush back to a twin cam
ps the car didn't come with twin cam
good luck

[vincereynard]

The down side of a Zetec conversion is that the car is no longer a Lotus. Not really! No more than a Jag E type would be real is someone dropped a 80's XJS engine in one. Or a Triumph Stag.
A fragile engine which many replaced with a Rover V8 in the day. A worthy conversion, with a superior lump, but worth little these days.

So if you decide to go Zetec, buy one already converted, it should save you time and money.

Spyder's customers have done much of the final R & D by now (ride height / steering ratio / special exhaust manifold etc ). Spyderfan's the chap to talk to.

[jono]

My Plus 2 is lightly modded and is great to drive.

Sometimes I think a bit more power would be nice but not very often.

It's full of character and quicker than many modern cars and handles and rides beautifully. If I wanted something faster I would buy an Elise.

Dyno curve for my car attached - pretty much the sweet spot for me. I just need to sort out the oil leaks!

That said I have a tall block engine sitting in the corner of my office which I keep looking at and thinking....mmm

Jon

[rgh0]

,but i do know that building a high power twin cam is not cheap and they need to be revved more than a zetec to get the power............
good luck

Yes I agree building a quality, high torque, high power twin cam is not cheap and a standard larger capacity Zetec makes more power and torque and comes cheaper out of the box but costs a bit more once fitted and you loose some market value in the process ( if that matters)

I have had the opportunity recently to look a little at modern 4 valve performance engines since my son got a 2004 Golf R32. At 3.2 litres its twice the capacity of a standard big valve twin cam and its output is almost exactly twice the torque and power, despite 4 valves, knock sensors, higher compression ratio and fuel injection and 50 years of development. The naturally aspirated engine world does not appears to have progressed in specific output much except for the fact it does not leak oil and its emissions are less! The story is the same for a Lotus 9xx engine in my Esprit.

The biggest difference in driving terms with a modern engine is the drive ability from cold and from low revs that modern fuel injection and electronic control of fuel and ignition offers and that Keith is trying to replicate from Weber's with his jetting modifications

cheers
Rohan

[prezoom]

Following the engine change comment, then installing a crossflow derived block from a Cortina, Escort, or adding a BDA cylinder head, also would make it a non-Lotus, sort of like being a little bit pregnant. My conversion was strictly economic, along with a little bit of desire for a bit more punch. Oh, the deceased engine that was in the car when I bought it was a tall block, along with a Weber modified Stromberg head, thus it was already a non-Lotus.

My conversion costs were less than trying to rebuild the melted lump that came with the car, and that included the cost of an 11,000 mile engine that was shipped across the US. I don't count my time doing the conversion, because that would be like counting the time when one plays golf. For me, my time in the garage, thinking, constructing, and assembling is the cheapest therapy I can get. Besides, when I retired, the saying: "I married you for better or worse, but not for lunch", became a reality for both parties.

[poppy]

,but i do know that building a high power twin cam is not cheap and they need to be revved more than a zetec to get the power............
good luck

Yes I agree building a quality, high torque, high power twin cam is not cheap and a standard larger capacity Zetec makes more power and torque and comes cheaper out of the box but costs a bit more once fitted and you loose some market value in the process ( if that matters)

I have had the opportunity recently to look a little at modern 4 valve performance engines since my son got a 2004 Golf R32. At 3.2 litres its twice the capacity of a standard big valve twin cam and its output is almost exactly twice the torque and power, despite 4 valves, knock sensors, higher compression ratio and fuel injection and 50 years of development. The naturally aspirated engine world does not appears to have progressed in specific output much except for the fact it does not leak oil and its emissions are less! The story is the same for a Lotus 9xx engine in my Esprit.

The biggest difference in driving terms with a modern engine is the drive ability from cold and from low revs that modern fuel injection and electronic control of fuel and ignition offers and that Keith is trying to replicate from Weber's with his jetting modifications

cheers
Rohan

Thanks for that, I am beginning to feel that a re- build on a twin cam is starting to make sense in many ways... originality, cost comparison / conversion to zetec etc. 150/160 bhp by many experienced owners seems to be a nice place to be.
Which would be the wiser choice. Staying at original capacity and more tuning or moving the engine upto 1700
'ish cc at time of re-build in terms of driveability, reliability and cost, all things being equal?

regards

[Elanintheforest]

My Plus 2 is one person?s solution to the old problem of how much power is enough. It was converted to run a Cosworth BDA in 1971, in part to showcase the Lotus Twincam and BDA race engine builder?s capability (and the owner ran the race engine business) and partially because the owner wanted a bit more get up and go in his Plus 2.

The BDA will run well over 200bhp, although at the top end it becomes pretty intractable and no fun for driving in traffic. Many permutations were tried with my car in the early 70s, but a fairly mild tune of 170 bhp with 140 lb/ft torque was decided upon as the best balance for a fast road Elan. The engine was built with big valves, ported and polished head and inlet manifolds, with tuftrided crank and rods, built into a modestly overbored AX (thick wall) block taken out to 1700cc. It also uses the standard BDA Weber 40DCOE48 carbs tweaked for the BD3 cams and big valves.

The AX is the strongest block you can get, and with the tudrided crank and rods, and everything very finely balanced, it will run happily to 8500rpm, with is approximately where the dynamo warning light is on the tacho! But the car starts and ticks over like a standard twincam, maybe a bit more lumpy, and was used to commute around Northern London and for a few holidays in Southern France and Spain.

I only used the car for a few months when I bought it, but it was a very impressive machine to drive, and had a great balance between power and usability. Once off the line, its mid-range is just superb, with a soundtrack that is spine-tingling, especially at the higher end of the rev range. It can get a bit loud!

As the engine is built, it would take only a morning to swap over a pair of hotter cams and pop on a pair of 45s suitably matched to the cams and the car would be converted to a screaming racer. I am slowly re-commissioning the car currently, in it's 'normal' road going specification.

Installing a BDA or BDG is certainly another approach to consider.
Mark Kempson

[rgh0]

The AX is the strongest block you can get, and with the tudrided crank and rods, and everything very finely balanced, it will run happily to 8500rpm, with is approximately where the dynamo warning light is on the tacho!
Mark Kempson

All ford 1500 and 1600 blocks if built properly will run to 9000+ rpm though the vibrations get pretty fierce above 8500 rpm. However i would not run a tuftrided cast iron crank above 7000 rpm unless you like rebuilding the destroyed engine regularly.

cheers
Rohan

[Elanintheforest]

This one had done around 50,000 miles before being rebuild Rohan,and was used to demonstrate one of the engine's features; it's ability to keep on revving! No vibration at all at generator warning light rpm, and the car was driven and held at 8000 rpm / 140 mph in Spain back in the day just to see what it would do. His missus was asleep in the passenger seat apparently whilst this testing was going on!!