Twin Cam Dyno Results

[2766R]

In response to weight, I had the Europa on scales years ago.  IIRC, it came in within a couple of pounds of 1500#.  When I ran this test, no spare or tools were aboard as when it was originally weighed.  I entered my weight of 170# and entered 35% fuel load.  The 110# payload listed is, I believe, not part of the equation as I cannot edit it in the app to zero.  BTW, I only saw 7000 RPM on the tach;  I assumed the app extrapolated!?  I really need to install the Pertonix dizzy and converted tach (Smiths RVI 1432/01 with Spiyda RVC conversion).  The original tach (RVI 1432/00) is suspect!  It reads about 2900 RPM @ 60 MPH in 5th gear though. Unless I have some other parameter wrong, IE gearing?  I still would like to make a couple of more runs in this configuration to establish consistent data.  The problem is the only good stretch of road has a speed limit of 35 MPH.  Jones Beach Ocean Pkwy, billiard table smooth and straight.  The federallies will certainly not be happy with me!  Not likely to be confuse with any other vehicles!!! 

[Pfreen]

I know.  It is difficult to find a place to do the test.  I went through the program and it calculates total weight by adding curb weight (full tanks) plus passenger weight, plus added weight, minus fuel weight if less than 100%.  So, your 110 lb is your weight minus the fuel which I guess was around 1/3 full.  If the 1500lb you measured was with full tanks, then your weights appear to be correct.
The program calculates rpm from speed, the gear ratio and the tire diameter so if you didn't take it to 8200rpm, then something isn't right.
Do you have a 5 speed?

[BDA]

... I really need to install the Pertonix dizzy...

I don't have an opinion one way or the other and I don't have a Pertronix dizzy (I do have the Ignitor II module in my Lucas 23D dizzy) but you might be interested in a discussion about the Pertronix dizzy here: (https://vintagetechnologygarage.groups.io/g/cars/topic/123_distributor/83808952?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,83808952). It starts off with a discussion about 123 dizzies but on June 28th, Keith Frank gives his take on Pertronix dizzies.

If you don't know Keith, he is knowledgeable (especially about Webers) and as you might guess from his posts, is very opinionated. I don't think his comments should be discounted. As you will see from the posts, not everyone shared his view on the Pertronix dizzy but I thought you might want to hear what other users said about them.

If you decide to get the Pertronix distributor or even an Ignitor module, you might want to consider if it will allow you to statically time your motor. The Ignitor I will burn up if you leave the ignition on for too long. The Ignitor II is protected from that.  When I upgraded from an Ignitor I to an Ignitor II, I went to statically time the motor and no plugs would fire. I called Pertronix tech support (they are very responsive and helpful - don't be shy if you have a question or problem) and the tech guy said that it was not expected to allow you to statically time and he promised me that it would work. It did. I suspect that the no-burn-up feature precluded the statically time capability. I wasn't too happy about that but I was happy about the fact that I couldn't burn up my module. I mentioned this on Keith's sidedraft groups.io list and he basically said I was an idiot. He swore that he used his Pertronix dizzy to statically time his engine. Neither of us had any explanation for this divergent experience. All this is to reinforce my suggestion to check about some details with the Pertronix guy to make sure you are getting what you want.

[2766R]

Pfreen: IIRC, the scale measurement was done with 1/4 or less of fuel.  Yes, 5 speed; originally 4 speed (352), now 365.

BDA: I have in my possession a Pertronix III.  I also have spoken with a Pertronix tech, RE: advance curve.  Was not to happy with the answer.  20° all in by 3500 RPM.  I’ve had it apart and saw the advance limit plate stamped 10° which equals 20° at the crank.  I’m thinking of trying to order extra weights and machining them to half thickness (except pivot bosses) to delay full advance to 7000RPM.

Comments/thoughts?  Appreciate any and all…

[2766R]

Correction: Pertronix III limit plate stamped 12°, not 10°.  Therefore 24° at the crank.
BTW, the current  dizzy is a 23D4 #41195 with a limiting plate stamped 10° = 20 at the crank and all in by 4000 RPM.  I have it set to 14° static, 34° total.

[jbcollier]

34° is high for a twin cam.  If you just poodle about, maybe a stoplight grand prix now and then, you'll be ok.  If you drive hard for extended periods, that's too much advance.  IIRC, 28° is the recommended max advance.  You can welded/brazed up slots to reduce total advance.  All in at 4K is fine.  All in at 7K will be too retarded in the mid-range.

[literarymadness]

2766R (Gerry): My engine is now bored and stroked like yours and also with a Billet Steel Crank, so a 7000 rpm redline no problem.  The crank could handles more but the powerband of my cam is 2000-7000 rpms and then falls off rapidly. I am running 12 degrees static with 19 degrees advance at 2500 rpm (31 total advance)and 22 degrees advance at 8000 rpm (34 total advance) where the limiter is set (Bluetooth 123 Ignition). Of course I never actually run the rpms past 7000.  Those numbers were recommended by Steve Smith at Twin Cam Racing who did my engine rebuild. He races both a Ginetta G12 with a Lotus TC engine and an Elan Coupe with his TC bored and stroked to 1815 cc. I would not recommend those numbers to anyone with a stock TC engine.

[2766R]

OK-I'll take both of your advice and retard back a few degrees.  I don't drive hard most of the time these days.  I do take it up through 3rd occasionally for fun though.  It just seems happy at the current setting.  I might take one more run using Perf-Expert  before changing.  In a perfect world, a few passes on a chassis dyno with A/F measurements would put things right.

[jbcollier]

I do some long trips which involve mountain passes.  I can spend 20 minutes, or more, flat out.  I set my timing carefully.

[Pfreen]

Gerry,

There is much info on ignition timing on the Lotus Elan site.  This exchange seems pertinent to the discussion.  https://lotuselan.net/forums/viewtopic.php?f=19&t=41666

Fyi, I run 14 deg at at 1000 RPM, 31 at 3000, and 33 at 7000 RPM.
I have 10.25:1 compression ratio, headers, Stromberg head, and the Kent cams L14 cam.  I did find the L14 cam wanted more advance at idle than the sprint cam I had previously.  I do have electronic, crankshaft triggered distributorless ignition, which does make it more accurate than a distributor.   I have never experienced detonation in my tc and before I fitted a cold air intake, the air inlet was measured at 130 degrees in the Florida summer heat.

This another interesting article on the accuracy of different distributors. 

https://classicmotorsports.com/articles/distributors-dyno/

The accuracy of your distributor may affect how advanced to go.

[MRN I J]

and the Kent cams L14 cam.  I did find the L14 cam wanted more advance at idle than the sprint cam I had previously.  I do have electronic, crankshaft triggered distributorless ignition, which does make it more accurate than a distributor.   

How do you find the L14 cams, what did you time them up to (mop or valve travel @ tdc ?)
they are an extremely versatile cam

[Pfreen]

I did a lot of performance modeling and determined 106/106 was the best compromise of high end hp and low end torque.  That is what Kent cams recommended as well.

[europa88]

Just to compare. Mine is a UK spec BV on Dellortos, CR10.5-1 L14 cams 1.625 inlets and 1.4 exhausts. MBE Wasted spark distributor less ignition. Type 47 copy (ish) exhaust with silencer. NG1 transaxle. Standard cast crank. Soft cut at 7050 rpm hard cut at 7100 rpm.
I could spend a lot of money on Dyno time to dial in my AFR better, but for now it will have to do. Unless I decide to go an all steel bottom end and change the cams for McCoy's or similar.

[Pfreen]

Europa88,
I assume your dyno numbers were on an engine dyno, not a rolling road?

If that is correct, my numbers are similar.  However, I only have chassis dyno numbers.
On a chassis dyno, they measured 130 hp at 6250 Rpm.  Peak torque was 115 ft-lbs at 5500 RPM.  This is more than I expected so I am not totally confident in the numbers.

[europa88]

Europa88,
I assume your dyno numbers were on an engine dyno, not a rolling road?

If that is correct, my numbers are similar.  However, I only have chassis dyno numbers.
On a chassis dyno, they measured 130 hp at 6250 Rpm.  Peak torque was 115 ft-lbs at 5500 RPM.  This is more than I expected so I am not totally confident in the numbers.

Ahh no! They were measured on a rolling road and adjusted using the manufactures algorithm. 125BHP at the wheels. I do have a well ported and gas flowed head too.