Lotus Elan

Disappointing Dyno results

PostPost by: ROADRUNNER » Tue Mar 03, 2020 7:08 pm

]I finally got an opportunity to have my S2 dynoed this week, and I'm interested to hear views on the results.

Given the engine spec, I'm disappointed !

Probably best to firstly summarise the engine. It was built by Neil Myers, and has probably done not much more than 5,000 miles since.

Cosworth steel crankshaft, L14 cams, gas-flowed ports / head, big valves, TTR fast-road exhaust and manifold.

The result of all this ? A lowly 82bhp at the wheels at 6500 rpm (approx 120 at the flywheel). Not much more than my standard S3 SE produced at the same dyno.

Very much looking forward to hearing your thoughts.I'll try and answer your questions to the best of my ability (based mainly on the spec sheet provided by Neil at the time) but I'm afraid I'm not very technical.

The attached pic shows both cars compared.

[attachment=0]Resized_20200303_142422.jpg[/attachment
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PostPost by: nmauduit » Tue Mar 03, 2020 9:18 pm

Here's my 2c to get the ball rolling, no doubt more in depths views will be expressed later.

it does not look so bad to me... did you fine tune the carburetion (and possibly the advance) on that occasion ? if not you may gain 5-10HP just doing that (or more, ymmv etc etc). I see the power increases till about 5k, and decreases above 6.5k so unless therichness is wrong high up or spark advance insufficient the use of the steel crank is a bit of waste, which I would feel a pity also. Then to make the most of high end power one needs more lift, more overlap ... so a less streetable engine : the actual rationale of the build is the result of the discussion with your builder I understand. L14 has about .41 lift 282° duration, comparable to QED Q420 profile, I would assume they also have relatively quick acceleration ramps... do you have the stock round air filter (or was it dynoed without)? what is the actual engine capacity and compression ratio ? all these little things add up...

Then was the S3 dynoed recently and with the same calibration? maybe this was a bit optimistic...
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PostPost by: collins_dan » Tue Mar 03, 2020 9:25 pm

I had a similar experience. I checked compression and it was lower on the first piston, so I need to sort that out. So my suggestion is to do a quick compression check. Dan
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PostPost by: ROADRUNNER » Tue Mar 03, 2020 9:28 pm

nmauduit wrote:Here's my 2c to get the ball rolling, no doubt more in depths views will be expressed later.

it does not look so bad to me... did you fine tune the carburetion (and possibly the advance) on that occasion ? if not you may gain 5-10HP just doing that (or more, ymmv etc etc). I see the power increases till about 5k, and decreases above 6.5k so unless therichness is wrong high up or spark advance insufficient the use of the steel crank is a bit of waste, which I would feel a pity also. Then to make the most of high end power one needs more lift, more overlap ... so a less streetable engine : the actual rationale of the build is the result of the discussion with your builder I understand. L14 has about .41 lift 282° duration, comparable to QED Q420 profile, I would assume they also have relatively quick acceleration ramps... do you have the stock round air filter (or was it dynoed without)? what is the actual engine capacity and compression ratio ? all these little things add up...

Then was the S3 dynoed recently and with the same calibration? maybe this was a bit optimistic...


The 'brief' to the engine builder was to deliver a 'streetable' engine, ie not cammy. Thats certainly what it has. However, Neil was clear at the time that the anticipated power output should be in the region of 140. What I appear to have is an engine that is only a little more powerful than my S3 SE. This power figure was without the air filter. Standard engine capacity. I'm afraid I don't have any info on compression ratio.
Last edited by ROADRUNNER on Tue Mar 03, 2020 11:20 pm, edited 1 time in total.
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PostPost by: nmauduit » Tue Mar 03, 2020 9:41 pm

ROADRUNNER wrote:However, Neil was clear at the time that the anticipated power output should be in the region of 140. What I appear to have is an engine that is only a little more powerful than my S3 SE. This power figure was without the air filter. Standard engine capacity. I'm afraid I don't have any info on compression ratio.


assuming all else is on the button (valve timing of course, compression etc. spark quality from good coil, fuel pressure...) unless thorough jetting swaps have been attempted during the dyno session I would investigate spark advance (unless max advance is already 34° or so) and carb tuning (esp. main / air but also idle as they still play a role after the main kick in), preferably with the help of a wideband sensor to see rapidly if you get the target AFR or not. This can be a bit tedious ... and depending on your build risk of pinging increase when you lean out at high revs to squeeze out the last HP, so be careful (can be a bit piston top dependent).
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PostPost by: ROADRUNNER » Tue Mar 03, 2020 10:03 pm

What I’d like to establish is whether my hopes for power from this spec are optimistic. Given the low power figure, I need to let the dyno operator know that we’ve still got a long way to go Interne of experimenting with jetting and ignition timing !
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PostPost by: collins_dan » Tue Mar 03, 2020 10:55 pm

Valve timing is a good thought. That's what I thought my problem was, but it was spot on. My valve clearances were off a bit here and there, which is frustrating, but probably not a big contributor. Dan
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PostPost by: Craven » Tue Mar 03, 2020 11:20 pm

Plot 3 on this graph is for an engine with same head mods & FL14 cams, same as L14. This shows peak 135 bhp. Apparently this cam profile gives best results with a higher C/R.
P1030154.JPG and
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PostPost by: ROADRUNNER » Tue Mar 03, 2020 11:38 pm

Craven wrote:Plot 3 on this graph is for an engine with same head mods & FL14 cams, same as L14. This shows peak 135 bhp. Apparently this cam profile gives best results with a higher C/R.
P1030154.JPG


Is this the engine spec in your car ? Very interesting info, confirms what I thought about being way down on power. What’s the C/R on this ?
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PostPost by: 1owner69Elan » Wed Mar 04, 2020 12:12 am

When you say "big valves" do you mean Sprint spec?
'69 Elan S4 SE
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PostPost by: Famous Frank » Wed Mar 04, 2020 4:32 am

Roadrunner,

I feel your pain. You spent a bunch of hard earned money, and it would make you feel better if the numbers were higher. All I can add is what happened to me many years ago.

I purchased a used 66 Elan S2 SE from a friend of mine. I knew he had recently rebuilt the engine. He spent a bunch on it also, ....... right down t a dry sump system. When I purchased the car it started immediately, idled good, and drove okay. It too had headers, aftermarket cams, porting work, etc. But when you really stoood on it, it didn't really pull hard at all. It was no faster than my other Elan that I owned, .... a 65 with a 105 hp motor. Just sort of disappointing. Then one day, the throw out bearing started squealing like crazy and I knew I'd have to pull the motor to repair it. Additionally my wife hated having the dry sump tank taking up foot room, so I was going to go back to a normal sump.

When I pulled the motor, I decided to spend some more dollars and brought it my friend and premiere engine builder, Barry Sales of PHP Race Engines in Wauconda, Illionois. First thing we did was to pull the dry sump oil pan and installed a standard oil pan. PLEASE NOTE: WE FOUND SOMETHING THAT WE SHOULD ALL LOOK FOR. WE PULLED A ROD CAP OFF TO LOOK AT THE BEARINGS AND THE STOCK ROD BOLTS WERE ONLY JUST A LITTLE MORE THAN FINGER TIGHT. STOCK ROD BOLTS STRETCH AT HIGH RPM.
WE INSTALLED NEW ARP ROD BOLTS WHICH ARE MUCH SAFER THEN STOCK TIRED ROD BOLTS. WE PROBABLY SAVED THE ENGINE AT LEAST ONCE BY DOING THAT. Before we too it apart, we put it on his engine dyno. It made 93 hp. Pretty sad. Good compression, no missing but no power. We started checking things. First thing we checked was timing. It was right on the money. Next we checked the cam timing. All the timing marks lines up as they should have. BUT, But, But, when Barry check the cam timing using tools such as a dial indicator at top dead center, etc. it became obvious the cams were not REALLY TIMED! Barry went to degree the cams and it turned out the intake cam was 7 degrees retarded and the exhaust cam was 3 degrees retarded. He degree'd the cams using offset dowels to get things in spec. We fired up the engine. Throttle Response was immediately improved and the first dyno pull netted 114 hp. From that point he changed the distributor curve, the Weber Carb chokes and the jetting. After another two hours on the dyno we ended up with 139 hp. What a huge difference!!! It pulled like a banshee!!! And the only parts changed were the dowels in the cams. Well worth the $650 of dyno time.

Best of luck and good luck in your search for more power.

Frank
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PostPost by: ROADRUNNER » Wed Mar 04, 2020 8:39 am

1owner69Elan wrote:When you say "big valves" do you mean Sprint spec?


Yes
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PostPost by: rgh0 » Thu Mar 05, 2020 12:00 am

Yes around 140 hp at the flywheel is a reasonable target for your engine assuming all the details are correct and people have mentioned a range of areas to check. The other issue is that can have a significant effect on rolling road dynos is how the car is sat on the rollers and tied down as this has a significant effect on measured wheel HP.

A friend of mine who races both a Twin cam Europa and a S4 7 was getting about 20 HP difference on identical engine builds. He went to the extent of swapping the engines and the measured HP for the same engine in the Europa was still 20 HP less than for the same engine in the 7.

He finally realised that due to suspension and clearance differences the tie down and roller locations were different and this was the cause of the extra apparent less HP for the Europa less than the Seven.

cheers
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PostPost by: ROADRUNNER » Thu Mar 05, 2020 10:53 am

All very interesting points - thank you all.

The car has been booked in to Max in Guildford to check cam timings etc. I'll revert back with findings !
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PostPost by: My72Sprint » Thu Mar 05, 2020 2:32 pm

Frank,
My McCoy 1950 was dyno'd and tuned @ PHP Race Engines in Wauconda, Ill.also.
Initial Hp 180 with HP 192.9 @ 7000 , Torque 160.7 @ 5600 when furnished
Why?
They keep their dyno calibrated and have performed a large number of Twin Cam dyno session's for comparison.
$'s well spend maximizing performance.
Tim
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