Lotus Elan

My Vegantune is Vaguely Tuned!

PostPost by: RichardS » Fri Sep 25, 2009 8:51 pm

Having done a couple of hundred miles since getting my Sprint back on the road I went for a rolling road tune up yesterday which was interesting. I had a bit of luck as on googling for a rolling road I found one within a couple of miles of home. They mainly tune Subarus [400 to 500 bhp!] but seemed quite familiar with Webers and Twincams - there was a TR6 sitting beside the rolling road.

I spent a happy couple of hours watching as the carbs were balanced and twiddled with. He set the timing at 8 deg static which advanced to 26 deg. The original spec for the engine [more of this below] was 18 deg static but the tuning guy said that if it was set to this advance with modern unleaded then the engine would self destruct! I am no expert on these matters but took his word for it.

Back in the 1980s I had the engine rebuilt by Vegantune to their G3 spec. The spec included Vegantune cams, blueprinted engine etc and a stated 150bhp. I was a little disappointed with what the rolling road showed yesterday - 105bhp at the flywheel and 82bhp at the wheels - the 150bhp seems to have evaporated over the years!! The engine has only done a few thousand miles since the rebuild.

Having said that a quick blast after the tune up and the engine is running very nicely and probably plenty powerful enough for me these day!

I found the bill for the last rolling road tune up in 1985 - this showed "120bhp at 70mph" and cost me ?25. The one yesterday cost ?85 which I thought pretty reasonable. The tuning guy told me the bhp readings back in the 1980s were notoriously inaccurate and involved a lot of guesswork.

I did read somewhere on the forum that Vegantune were also known as Vaguely Tuned so I wonder what exactly is inside my Twin Cam. Will perhaps investigate one day but at the moment am having too much fun driving!

Richard
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PostPost by: handi_andi » Fri Sep 25, 2009 9:31 pm

Well given Lotus kinda mis-laid the truth with the S130 given it only produces 126BHP, and I be surprised if many of them acutally did when they left the factory, your results would seem to be quite appropriate :D

Am looking forward to taking my S130 to the rolling road once its mini-rebuild is complete to see jsut what the engine is actually producing.

Cheers

Andy
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PostPost by: 1964 S1 » Sat Sep 26, 2009 12:16 am

Hello Richard, a good little story. I know very little about Vegantune. ( today is hug a vegetarian day! )
I think your comment about having too much fun driving says it all. I subscribe to ignorance is bliss when it comes to having fun.
I've been reading about rolling roads here for years and always wonder, do we have them in the USA? What the heck does one look like? The only "rolling" road I've tested on stayed still, it was a dragstrip. Ran two stock Elans and a +2 in the quarter mile. Best time was 15.75 sec. The +2 was less than two seconds slower, BUT, I got beat by a Woman in a Miata!

If it feels fast and is fun HP means nothing in my book. (my first car was a Fiat 600 so my book is very thin)

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PostPost by: CBUEB1771 » Sat Sep 26, 2009 12:43 am

1964 S1 wrote:I've been reading about rolling roads here for years and always wonder, do we have them in the USA? What the heck does one look like?


Eric,
Chassis dynamometers (rolling roads) are not difficult to find in the US. The following link is to one in my area:
http://www.ktrmotorsports.com/service/dynamometer.htm
There is no substitute for setting up and running in a new engine on an engine dynamometer. However subsequent tunings are relatively easy on a chassis dyno because you don't remove the engine from the chassis.
Last edited by CBUEB1771 on Sat Sep 26, 2009 10:59 am, edited 1 time in total.
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PostPost by: 1964 S1 » Sat Sep 26, 2009 12:47 am

Thank You Russ
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PostPost by: RichardS » Sat Sep 26, 2009 8:10 am

1964 S1 wrote:What the heck does one look like?

Eric


Eric - here is the link to the place I went which has pics of the rolling road http://www.dynodemon.co.uk/home.php?/Home

Vegantune were quite a big name in Lotus Twincams during the 60s and 70s and are mentioned quite extensively on Miles Wilkins bible on the Lotus Twin Can engine.

When I bought my Sprint in 1982 it turned out that it had a mongrel of an engine with a Lotus cam cover on it. Vegantune were still one of the "big names" and I sent it down to them for rebuilding to their supposed 150bhp spec. I have the invoice for ?1511 for the "fully bench tested and run in engine". The garage I bought the car from did contribute something to the cost in recognition of the dodgy original engine!

I've attached the original spec sheet from their advert and the spec sheet for my engine.

Am off to sunnier climes for a week this morning and am looking forward to picking up a few classic car magazines at the airport to peruse by the pool with a cool beer or two!!

Richard
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spec2.jpg and
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PostPost by: JJDraper » Sat Sep 26, 2009 9:07 am

Don't you just love the small print at the end of the Vegantune spec sheet!

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PostPost by: bcmc33 » Sat Sep 26, 2009 9:52 am

I had my car on a rolling road local to me to set-up the fuel injection conversion. As per Richard?s comment, I was a little disappointed with the end result of 128 bhp even though the tuner said ?you have a very nice standard engine?. When I ?complained? that this did not seem that good when the big-valve engine was always reported to be 126 bhp ? I received a smiling shake of the head to be told that the average standard big-valve returns 110 bhp.

I did ask the question to a well known racing Twink engine builder who confirmed the 110 bhp figure.
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PostPost by: elancoupe » Sat Sep 26, 2009 10:37 am

CBUEB1771 wrote:
1964 S1 wrote:I've been reading about rolling roads here for years and always wonder, do we have them in the USA? What the heck does one look like?


Eric,
Chassis dynamometers (rolling roads) are not difficult too find in the US. The following link is to one in my area:
http://www.ktrmotorsports.com/service/dynamometer.htm
There is no substitute for setting up and running in a new engine on an engine dynamometer. However subsequent tunings are relatively easy on a chassis dyno because you don't remove the engine from the chassis.



+1

I thought I had my car fairly well dialed in, then I took it to a chassis dyno in Cleveland. Simple jetting and timing changes produced an additional 8HP, the $90 spent was a pretty good bang for the buck.
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PostPost by: rgh0 » Sat Sep 26, 2009 11:11 am

Love the vagueness of the Vegantune spec sheets - certainly live up to vaguely tuned nick name.

150 hp from a 1558 twink at less than 7000 rpm and 10.3:1 comp ratio is possible - just - but requires a top quality porting job and big valves and high lift ( above .41) short duration cam (around 280 seat to seat ) and valve gear to suit the lift plus big carb chokes and big exhaust.

The Vegantune sheet would have certainly said all this if they actually did it

cheers
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PostPost by: tdafforn » Sat Sep 26, 2009 3:11 pm

Hi Guys,
Got my V. tired (60K miles) +2 bigvalve chassis dynoed before I rebuilt the engine. Gave 108 BHP
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PostPost by: john.p.clegg » Sat Sep 26, 2009 4:27 pm

......and after????

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PostPost by: rocket » Sat Sep 26, 2009 7:51 pm

Would the 130bhp claimed by Lotus not be measured at the crank rather than the wheels?


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PostPost by: bcmc33 » Sat Sep 26, 2009 9:59 pm

From what I've been told by two rolling road tuners - 130 bhp at the flywheel will result in 100 bhp at the rear wheels.

The readout from my set-up shows 99 bhp at the rear wheels and a resultant 128 bhp at the flywheel.
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PostPost by: RichardS » Mon Jan 29, 2018 7:17 pm

My engine is out as I needed to remove the gearbox for repair.

You will see from the original thread that my Vegantune rebuilt twin cam is nowhere near the 150bhp stated in the build sheet. So seeing the engine out I wonder if now might be the time to address the issue (could be expensive thoughts!).

I had a rolling road assessment 6 months ago. This shows a similar bhp to the last time (different venue) and perhaps if we had taken the revs to 6750 might be approaching 90 bhp at the wheels? Looking back through the posts Rohan has said 90 to 110bhp for a big valve is to be expected. This time I have a graph with bhp and torque which I have attached.

How does this look? Is the torque about right for a big valve engine?

I guess if the figures approximate a standard big valve then I will leave be but if significantly below expected then perhaps will consider a rebuild to improve performance. The engine has only done about 15000 miles since the rebuild in 1982.

Any opinions appreciated

Richard
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