Twin Cam Dyno Results

[jbcollier]

http://www.lotuseuropa.org/images/WorkshopManual/Carb1.pdf
http://www.lotuseuropa.org/images/WorkshopManual/Carb2.pdf
http://www.lotuseuropa.org/images/WorkshopManual/Carb3.pdf

[surfguitar58]

  Fitting modern flat-slide, smooth-bore motorcycle carbs will make a huge difference.  It wouldn't look that out-of-place either.

Bike carbs are an intriguing idea. Am I right that retrofitting a Stromberg manifold car with 2 bike carbs would require something like carbs designed for a 1600cc V-twin? These for instance?

https://www.maxairengineering.com/mm5/merchant.mvc?Screen=PROD&Store_Code=ME&Product_Code=MAX_HSR_42&Category_Code=ROADSTAR

I'd be interested to hear if anyone has tried this and what the benefits and pitfalls are. Seems like a more reliable solution than those godawful Strombergs.

Tom

[jbcollier]

There is nothing wrong with the Strombergs except they wear and were set-up to solve pollution issues not to perform.  You can set them up to run well and reliably — I posted a long article on this previously.

However, all that said, they are still restrictive while modern bike carbs are not.  There is literally no restriction at WOT.  Weber’s/Dells still have lots in the way at WOT.

I would size the carbs based on the intake bore.  Probably 45mm  carbs would fit the bill.

[Sherman Kaplan]

I found the articles on this forum

It is 3 pages, here are the links:

http://www.lotuseuropa.org/images/WorkshopManual/Carb1.pdf
http://www.lotuseuropa.org/images/WorkshopManual/Carb2.pdf
http://www.lotuseuropa.org/images/WorkshopManual/Carb3.pdf

Sherman

[Pfreen]

I just ordered the OA7 and OA8 needles from Joe Curto.  I’ll post the results.

[literarymadness]

For what it's worth, a lot of guys on the lotuselan.net site have dyno'ed their twin cams.  Most say on that forum that the 126 hp sprint spec cars dyno out at the rear wheels between 90-100 hp.  One guy on this forum a few years back dyno'ed his slightly built TC engine at the crank at 135 hp and 103 hp at the rear wheels. That would make "pfreen's" 115 rwhp translate to more like 145+ hp at the crank or at the very least 140+hp which quite impressive for a Stromberg head.  I've see his car in person and his TC is quite impressive.  I can't wait to get my to get my TC back next week from Twin Cam Racing in Sarasota to see how much of a difference the reground cams and B1TD needles translate on the dyno.

PS I really wish a lot more guys on this forum would dyno their Europas just to compare notes.  To me it was $50 dollars well spent to see what actual differences all those slight changes make to my Europa.

[Pfreen]

So I bought the OA7 and OA8 needles from Joe Curto.  The OA7 was way too rich.  The OA8 leaned out cruise at 50-80 mph to about 14.7:1 from 13.2-13.5 with the SM needles.  It runs great, so I am keeping the OA8 needles.  At wot, it goes rich to about 11.5 To 12:1.  That could be due to the needles or the dashpot enrichment.  I am using 3 in 1 oil (not the 20wt) in the dashpots.  It really improved response from 20 wt oil I was using before.  I also bought two colortune plugs to set/insure the carbs were set equally for a/f ratio.  I have a Unisyn so I made sure the throttles were synchronized.

The change in needles should improve my mileage and the plugs look great.  I am running Champion n7yc and am very happy with them.  I tried ngk iridium plugs but I found they fouled easily.  They may be fine now since the engine is broken in and the carbs set up.

[BDA]

It sounds like you have things worked pretty well. 

I would suggest that instead of a Unisyn, that you get a synchrometer (https://www.ebay.com/itm/VW-Porsche-Dual-Carburetor-Synchronizer-Synchrometer-Airflow-Meter-Weber/172304682623?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649). I have a Unisyn and the synchrometer was much easier to use and much more accurate.

[jbcollier]

Sounds much better.  WOT and low 12s is just fine.

I use dexron 3 automatic transmission fluid in SU and Strombergs.  It’s lighter than 20 weight and, bonus, doesn’t swell diaphragms.

[jbcollier]

I don’t recommend 3:1 oil.  It turns hygroscopic if heated.

[literarymadness]

Just dynoed the car with the reground cams.  108 rwhp and 102 torque from Stromberg head and carbs (B1DT needles) normal compression 9.5:1.  Had the rev limiter set to 6200, so it looks like it might have gotten a few more hp.

[Clifton]

Just dynoed the car with the reground cams.  108 rwhp and 102 torque from Stromberg head and carbs (B1DT needles) normal compression 9.5:1.  Had the rev limiter set to 6200, so it looks like it might have gotten a few more hp.

Compared to your last dyno, you are down quite a bit in mid range due to being so rich. You can't see the torque on the second one but hp is over 10 less. 13-13.2 is where you make peak power.

[literarymadness]

Sorry for making the dyno print so large.  You should be able to scroll over to see the torque figures.

The first dyno run: my TCS is stock Fed Stromberg Twin Cam with emissions equipment removed.  I wanted to document any horsepower change with each mod I did.

My first dyno run before any changes were made (1/18)...4th gear:  90.72 rwhp and  82.45 lbs torque
Dyno run after change to electronic ignition         (2/18)...4th gear:  96.70 rwhp and  95.14 lbs torque
Dyno run after adding headers and carb rebuild   (5/18)...4th gear:  99.01 rwhp and  91.87 lbs torque
Dyno run after cams reground from .350 to .383 (9/18)...4th gear:108.08 rwhp and 102.54 lbs torque

I thought the rev limiter was off (located inside the distributor) but instead it defaulted to 5500 rpms so I am sure if it had gone to 6500 rpms, the horsepower would be 2-4 hp higher.

[Bainford]

Those gains are significant. Over 17 HP with minor mods and tuning. The car must feel great. Any drivability issues with the re-grind?

[literarymadness]

The car is very streetable.  A lot of my driving is downtown Ft. Lauderdale and occasionally  downtown Miami. The regrind numbers help explain it better.  The duration is 268 degrees which is just under D spec Sprint cams, but the lift is .383" so I really didn't sacrifice any low end torque, but I get a huge mid-range surge of power past 2500 rpms all the way to redline.  The Fed spec Europa is .350" and the Euro Sprint cam is .360" so I was ecstatic to get .383" with nothing other than the reground cam swap out (no head work).  Twin Cam Racing who installed it evn did it without pulling the engine which really kept the cost down.  When I did the last dyno my rev limiter was set to the wrong rpm and wouldn't let me go to 6500 rpm.  I have since reset it and want to re-dyno the car to see if it will break 110 rwhp.