Stock engine lean with B2AR needles

[JohnCh]

I could use a little advice after a dyno session today to dial in my ignition advance. The engine is a '68 with Strombergs that has been converted to non-Federal specs (Euro-style intake manifold and B2AR adjustable needles), it also has a 123 Ignition and RD Enterprises tubular exhaust manifold. As far as I know, the rest of the engine is stock and it runs great.

To our surprise, the wide band O2 sensor showed the engine was extremely lean, particularly on top. An adjustment to the needle height improved things at lower rpms, but they are still wildly lean over 3500rpm, averaging about 15.5:1, Based on what I've read in the archives, I wouldn't expect the B2AR needle to be this lean on a stock engine. Has anyone else seen this behavior on the dyno? Is there anything I should check, or do I simply install richer needles and try again?

Thanks,
John

[Billmack]

Is the engine in a car? If so it's possible that fuel system is not delivering enough from the tank for some reason. I'm assuming you have already done the obvious stuff ie vacuum leaks bad diaphragms etc

[JohnCh]

Yes, engine is in the car, and absent the A/F data, I'd say it runs great. Starts right up, idles fine, good throttle response, not flat spots, etc. Diaphragms were examined at the shop when checking the needles and they looked in good shape. No other behavior that would indicate a vacuum leak. Before I started looking for a problem that might not be there, I wanted a sanity check that a stock engine shouldn't have such lean A/F readings with those needles.

On the first run, power was still building as the engine approached redline, so it didn't seem like it was a fuel flow issue, but I suppose that's a possibility. I'll take a look this weekend and will also measure the needles to make sure they match the specs. Any other ideas or opinions?

Thanks,
John

[rgh0]

How was the air fuel ratio measured? Sticking a sensor up the tail pipe can sometimes result in a lean measurement due to exhaust pressure pulses drawing air in back down to the sensor diluting the exhaust gases.

cheers
Rohan

[JohnCh]

The sensor was up the tail pipe. Unfortunately I never got a look at it so I'm not sure how far up it extended. Here is a video of the second run that shows the sensor location.

https://www.youtube.com/watch?v=RjVKKfBNU0g

Thanks,
John

[Craven]

Could always fall back on the old plug cut colour check for weak mixture.

[Billmack]

Very tempting to just leave it alone and have fun. Possible that the measurement is somehow inaccurate.

[JohnCh]

Craven, someone else mentioned that. Sadly we didn't' question the readings and didn't think to check the plugs after a dyno run when it would have been easy. I'll try to do that today if I can find a good spot to do it properly and safely.

Billmack, given I've been driving the car like I stole it for 4000 miles and there have been no other indicators that something is amiss, I'm tempted to do that, but it's hard to forget the readings. If I can perform a proper plug cut, and they look perfect, then I may do just that.

Thanks,
John

[Billmack]

Maybe put a different car with similar exhaust and see if it looks lean also. Just to see if the science holds up. Was HP rating looking ok?

[JohnCh]

Unfortunately finding another local owner with the same exhaust manifold who is also willing to go to that shop for a dyno run will be a bit of a challenge

The baseline run up to redline showed 90hp at the rear wheels on the Dynojet, and revs for both hp and torque peaks were consistent with the non Federal numbers published in period. Based on what I've read elsewhere, I expected hp would be in low-mid 90 range, so maybe a little low, but it would be good to compare to results others have seen.

Thanks,
John

[bdea]

Hi John,

I have the same setup as yours.

Please review my details about the B2AR vs. B1CE Mod that I did.

I did try to use the B1BT: Did not run with the needles flush. With needles rich (withdrawn 2 1/3 turns rich) it barely idled, had to play with the throttle! Would hesitate upon reving to 2.5k rpm, then was OK. Did not try to drive with this needles installed b/c I Didn't think it would run under load! Went back to the B1CE...RUNNING LIKE A CHARM! Hope this helps!

I did a few mods since the last post to rectify the off idle, stumble and surging issues:
Repaired possible electrical items:
Replaced the ignition switch
Replaced my kill switch (bad) separate power to Pertronix Ignitor III
Checked all wiring behind Dash and to modified fusebox (4 fuses)... loose
terminal connectors!
New Pertronix Flame Thrower 3.0 ohm coil
Timing reset to 8.5 btdc... poor fuel.... Pinging! Costco top tier premium gas!

Car now runs fine except it can't rev above 5.5k rpm as indicated on the Smith's tach!
It was calibrated to 6k via Spyida circuit board 200 hz instructions.

ANY SUGGESTIONS?


Can't figure out why the Pertronix Ignitor III still runs like crap compared to the points/condenser, it misses at idle, surges and stumbles. This is the 3rd unit!

Enjoy, Brad

viewtopic.php?f=40&t=46826&p=337424#p3374


Stromberg 175 CD-2 B1BT/B2AR Adj Needles to Enlightenment
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2 posts • Page 1 of 1
PostPost by: bdea » 29 May 2020 03:42 pm

20200523_150449.jpg and


Could I please ask for a favor from the Lotus Elan.net Forum members?

Does anyone have pairs of B1BT and/or B2AR Adjustable Needles that I could borrow to test against my current installed B1CE adjustables?

My current needles are B1CE that are filed down to 50% diameter at positions 7-13.

The current setup was done when I dynoed my defederalised 1969 SE4 Coupe.

The modifications at that time was the removal of all the emissions equipment, capping off butterfly shafts and emission ports and the replacement of the Distributor to 43D.

The Stock motor was modified when Dynoed by Charlie Rockwell in 1990 and has traveled 22k miles since.
It has slept for 7 years after I retired and was motivated to awaken via my good friend Mike Ostrov of Elite fame! We have been trying to resolve a bogging off the line issue ever since it was dynoed in 1990.

Here are some of the specifics of my Build and dilemmas:

Original Setup:
Stock 0.40 over motor
Balanced (no sizzle at directly connected lever w/o rubber bush)
Dave Bean modified head to Big Valve Head Specs w slight porting, blunted nosed siamesed intake tracts
Pertronix Ignitor w MSD 6A Multi Spark Ignition, love that staccato sound! in a 43D Distributor w Blaster coil
Now: Pertronix III auto dwell w rev limiter set at 6.2k rpm, SHOULD I RAISE IT TO ? Max RPM?
Stromberg 175 CD 2S ( Jaguar XJ 1971-2 ) with filed down B1CE that are filed down to 50% diameter at positions 7-13
SS header with Sprint Muffler that I carried on the plane in 1985!

115 HP at the flywheel and 100 at the wheels.

Tried B2AR needles at the time but too rich at part throttle and too lean at Full throttle. Opposite of what you want! Filed B1CE needles!

Ignition Timing: 15 degrees BTDC, 30 degrees max at 5-5.5k rpm. Not sure which Distributor was used at that time:
25D, max to 30 total advance at 5.5k rpm, 15 degrees static or
new 43D to 25-27 max at 3k rpm, 10 degrees Static

Cam timing: Exhaust 108.5 degrees BTDC, Intake 111 ATDC

No test for detonation

Current Issues:

Bogging at start off, have to rev off 975 rpm idle to 1.2k rpm to prevent stumble! Bucks every Time!
Idle was erratic, held steady then dropped 100 rpm and go back up by itself! Could be additive fouled spark plugs!

Corrections with Mike:
Balanced Carbs, Vacuum steady at 19, spark energy at high tension wires at 5k volts
Cleaned spark plugs NGK BPR6ES of Current Premium Costco California Gas additive build up, look at pics!
Resistive NGK ignition spark plug wires checked for spark voltage = 5K volts
Timing at 10 degrees BTDC w 25-27 total Advance
Car runs better, but still looking the ultimate performance!

Thanks to you All!

Brad Dea

PS: I will be attending the San Francisco Bay Area GGLC Meet BBQ / Parts Swap Meet at Mike Ostrov's Shop in El Sobrante, CA. Saturday June 14,2020 to swap stories and possibly help others in our pursuit of Lotus evana? Nirvana
Spent last 4 hours editing after loosing the post on the cell phone and half asleep!
Attachments
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Last edited by bdea on 30 May 2020 03:36 am, edited 3 times in total.
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PostPost by: bdea » 29 May 2020 03:52 pm

Also review my other post on Bog and Hesitation:

viewtopic.php?f=40&t=46826

[JohnCh]

Thanks Brad, that's helpful. Do you happen to know what the A/F ratios were with the B2ARs? I spoke with the shop this morning. He thought about it over the weekend and came to the same conclusion as Rohan regarding exhaust pulses. As he put it, it doesn't make sense given how well the engine was running, even at idle. They will install a port for a WBO2 sensor in the next couple of weeks and try again. If the results are the same, then at least I know there is an issue somewhere. If not, then I won't spend a lot of time chasing a red herring. I'll report back after it's done, but in the meantime, I will confirm there are no intake leaks and will attempt a plug cut.

Thanks,
John

[bdea]

John,
here are my notes on the dyno test results and needle charts. Hopefully it isn't TMI Too Much Info! First/Last two pages may help. In REVERSE ORDER: 9,8,7...

Brad

[bdea]

Here are the last 5 Notes in REVERSE ORDER:14,13,12...

[JohnCh]

Thanks Brad, it is a lot of information, but I'm a data junkie, so I'm looking forward to digging through it all. If you don't mind, I'll circle back with you via PM if I have any questions.

Thanks,
John