Lotus Elan

BHP versus ?s or $s

PostPost by: jimj » Sun Mar 23, 2014 10:08 am

A couple of things this week had me musing: Firstly, like all of us, I imagine, I like the Elan to be running at its optimum, like many I have a big valve engine in my S3. Secondly, I can well appreciate the enormous satisfaction to be had from building up a really special engine. I only wish I had the ability. But......it does seem that once you`re looking for 140bhp+ there`s a big cost involved and I wonder at the actual value, in every sense, to the owner of a road car.
It`s not often I`m maxing the revs. on the road, very rarely I`m thinking, yet these higher outputs are produced at even higher engine speeds, requiring a big expenditure to cope with the higher revs, and often at the expense of torque which seems a poor exchange.
There was in interesting comparison in Autocar this week comparing the 3 different (predominantly) engine options in the F type. The V6 and V6s produce the same torque at the same revs. and maximum power at the same revs. Both weigh about the same, about twice as much as an Elan. The V6s has 40bhp more and is 0.2 seconds quicker 0-60. Can anyone tell the difference? Power to weight it`s equivalent to a 20bhp increase in an Elan. Does that fifth of a second make it any more fun to drive.
There are plenty of more powerful sports cars around for much less money than an Elan but I doubt they are more fun to drive, which is really what it`s all about, isn`t it?
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PostPost by: rgh0 » Sun Mar 23, 2014 11:04 am

Hi Jim
Without spending big money or much more than a good quality rebuild to standard specification, you can get maybe 150 hp from a 1558 to 1600 cc standard bottom end twink. That power will come at about the same 6500 rpm rev limit as the standard engine. The torque curve will be better and you can certainly feel the performance increase through the rev range on the road. Rebuilding with a 1600 cc crank and special pistons will cost a little more and get you 1700cc and get you a little more torque and max power. I agree building a 8000 rpm 180+ hp full race engine is a waste of time and a lot of money for a road car. There is an intermediate step where you get 160 to 170 hp in a road useable engine at about 7500 rpm but its an expensive step as it requires building a competition bottom end for that extra 10 or 20 hp above the 150 hp you can get without it

Does a little more hp make an Elan more fun to drive? That's ultimately in the eye of the beholder but I certainly think it does :D

Last edited by rgh0 on Sun Mar 23, 2014 10:13 pm, edited 1 time in total.
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PostPost by: trw99 » Sun Mar 23, 2014 4:09 pm

I remember how back in the 1970's magazines the talk was often about 'blueprinting' your engine - as often as not a Mini Cooper unit in Car and Car Conversions.

It's not a term one hears about so often now. I guess modern engines are made to far finer tolerances. Nonetheless, any TC would benefit from a good blueprint I would have thought, enough to notice a spritely and crisper response on the road.

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PostPost by: oldchieft » Sun Mar 23, 2014 8:29 pm

When I was a small part of a drag racing team, the saying was. "There is no substitute for cubic inches."

When we were massively out-spent by other teams it changed.

"There is no substitute for cubic bucks."

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PostPost by: holywood3645 » Sun Mar 23, 2014 9:33 pm

Jim, I think the QED 1700cc Super Sprint 'Spec' engine is the perfect combination for a road going elan, Good HP and torque. You can build most of it to that SS420 spec' yourself without breaking the bank. It produces 145-155bhp with real nice torque. It pulls nice from 2000 rpm in any gear. That combined with a modern electronic ignition, and well setup 40DCOE151 is a pleasure to drive. I think it?s about the upper range of HP needed for a stock elan.
There is lots of information available for the spec, If you?re in the UK sourcing the bits is pretty easy to source. The tall 711M block is a bit of an issue in the US, (unless you can buy new at approx. 1600USD) but a Lotus L block will work just as well with a little fewer cc's.

I have the QED420 spec motor in my S4, and now I?m really looking into suspension & gearing performance upgrades to take advantage and utilize the power the motor produces. It?s just on the edge of being 'hairy' but a better dialled in suspension will make a huge difference

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PostPost by: Pistacchio sprint 72 » Wed Mar 26, 2014 1:39 pm

Well you have the raw bhp discussion but there is also the accelleration feeling. How fast is the engine taking its revs...?
By lightening the flywheel you can get a feeling of having a faster car for little money.
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PostPost by: adigra » Fri Mar 28, 2014 1:03 pm

When I had my engine rebuilt (S3 S/E engine, but quite tired, so I'd guess it had lost many of its 115 horses at that point), the cost of rebuilding it to standard spec. wasn't much different to building it to, what eventually ended up being, 145bhp. Standard block, but big valves, 420 cams, flowed, etc.. All in, I think the biggest difference was the added cost of new cams.

As I said, I think the car was already quite a bit down on power, but the difference between before and after was stunning. We have a Sprint in the family with a "150bhp" QED engine, and even though there were two people in my S3 (with a 3.55 diff) and only the driver in the Sprint (3.77), there was nothing at all between us in rolling start race.
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