Rolling road today

[SADLOTUS]

I've had a niggly missfire that's gradually been getting worse over the last few weeks. Happens between 1500 and 3500 rpm, ticks over fine and all clear over that 3500 threshold. Changed the rotor arm, distributor cap and the plugs. had the tops off the carbs and blown through all the jets. Listening through the mechanics stethoscope (bit of hosepipe) at each of the chokes I could hear the missfire on the back two. Possibly out of balance, possibly an out of adjustment float.
Decided to take it to Sanspeed in Bexleyheath (South London), it's been there before very early in its life. Peter San, quietly twiddled this and that, adjusted screws and checked experience against the various digital readouts.
Yes my carbs were out of balance - the locknut on the balancing bar was loose, the timing was out - 38 against 33degrees, ten minutes on the rolling road at the beginning and at the end - probably wasn't necessary - but reassuring.
Just over an hour later all back to normal.
Very pleased. No connection, other than a recommendation all those years ago.

http://www.youtube.com/watch?v=ltWwhmHhaus

[peterako]

I'm jealous!!

[dusty]

Very alarming noise from the rolling road on overrun!!

Engine sounds nice though.

[alaric]

Good for you; might take my car there once it's on the road. Thanks for the referal.

Sean.

[billwill]

Those things and even the MOT brake test rollers frighten the life out of me

If the roller bearings seize up or something jams in its gears, your car will go straight through the workbench in front of it.

[SADLOTUS]

Bizzarre how these things happen....
Looking for something else I found these sheets from the last time I went to Sanspeed, almost 12 years ago to the day.
Comparing the two curves a few things show up.

Assuming the Road was rolling at the same speed, my car wasn't very fast!...120km/h max....75mph! mmm, did I have that 4:44 anglia diff in there?
Oh dear, 52kW...er what's that? 52 divided by 0.735 = 67bhp
...and a sticking valve on No3.
Distributer on points
94000 miles vs 10000... there's been a new speedo in the last twelve years...and a new engine.
Plus a bit of inflation - ?58 vs ?140

Interesting tho.
Dont really understand the reverse of the Performance Test sheet (labelled: BOSCH)
Talking of which my brother thinks the main graph axis should be labelled: TIME and COST

[GrUmPyBoDgEr]

An enjoyable Clip, thanks!
That's one meaty Road Twincam Engine
A couple of questions, if I may?
1. What size & make of Tyres & Wheels are fitted; they look good?
2. Where can I get some Spinners like yours; 26R'ish I think? Expensive? (OK 3 Questions )

Cheers
John

[SADLOTUS]

Hi John

Wheels and spinners are TTR 26R 13" with Falken tyres....ahem...185/60 and 205/60 F/R
expensive? er..yes thank you.

I believe bigvalvehead Dave was selling similar spinners that fit the standard threads... I think so.

[rgh0]

Nice to see a dyno shop that does not over inflate the difference between the measured rear wheel power and the estimated flywheel power - if anything its even a little under done.

What specification is your engine?

cheers
Rohan

[rgh0]

The performance test sheet is a graphical way of adjusting the test horse power at test atmospheric pressure and temperiature back to a standard horseppower at standard atmospheric temperature and pressure and then a chart on the right to give a 5% tolerance range on that horsepower.

cheers
Rohan

[bcmc33]

Nice to see a dyno shop that does not over inflate the difference between the measured rear wheel power and the estimated flywheel power - if anything its even a little under done.

My rolling road 'expert' uses a transmission loss figure of 23.5% and the Sadlotus figures indicate 13.7%. I well remember that the losses used for my old S2 were set at 25% - but this was 40 years ago.

What should the real figure be for the Elan?

Do the figures vary between different rolling road equipment?

[rgh0]

Losses vary with car and rolling and how both are set up and maintained. Things like oils used and tyre pressures can make a big difference.

For my Elan when tested in third gear on a rolling road I estimate a loss of 4.0 kw per 1000 rpm. i believe this gives the best correlation between engine and rolling road dynos. This approach best matches the theory around losses as i understand it and simulates the lower peak rpm you see on a rolling road dyno as the constant increase in losses versus the flattening engine hp curve will lower the peak hp point measured.

Puma Race Engines (pumaracing.co.uk) who are very passionate on this topic say for a 100 to 200 hp engine add 10hp to the wheel result and then divide by .88 for a rear wheel drive car. This matches well my estimated losses for a 150 hp Elan engine at around 6000 rpm so we do not disagree in absolute terms I think.

regards
Rohan