The Resource For All Things Datsun Roadster S211/SPL212/310/311 Datsun Sports Roadster 1959-April 1970 circa 40,000 produced https://www.311s.org/phpBB3/
Thanks Rob, shows the value of dyno tuning
Could you add if it was A or B cam
Re: Dyno sheet thread
Posted: Fri Sep 22, 2017 7:37 pm
by Gregs672000
I will look for my dyno sheet from several years ago to give more data at different RPMS. At that time, engine ran a Racer Brown cam, ported head, stock valves, stock pistons and compression ratio, header, 2" exhaust, 48mm SK racing carbs with 40mm chokes (operator noted they were not working well as the dyno plot was shakey and it went way lean at one point), EI dizzy with a Jacobs Pro-Street spark box, cold air box. It did 132rwhp, don't remember the torque.
It now has forged pistons, 11.7 to 1 compression ratio, bigger valves, crank fired ignition, aluminum flywheel, adjustable cam gear, 45mm Dellortos on 37mm chokes and still with the Racer Brown cam but I have a better Isky cam waiting in the wings and most importantly the cam is timed better! It's stronger than it was above but I don't have numbers for it. I expect to gain a lot more power with the Isky cam (it was better with it before I had to pull it due to rocker and cam wear). For what it's worth, it is a very streetable car (at least to me and what I'm used to), I am not worried about starting on a hill or having to be "super" nice to it at low rpm (somewhat, due running pump gas and having a high compression ratio; stomping on it at low RPM will result in knock)... it is definitely happier above 3500, but with the Isky cam it was more responsive at 3200 despite being a "bigger" cam. I can't over emphasize the importance of proper cam timing. After doing all the mods above, it lost 8-10hp with bad cam timing despite all the changes that should have produced more power (was a different dyno too).
Dynos vary by the way, so what is 120hp might be 130 or 110 elsewhere... I'm not sure how much they vary, but it would be important to use the same one if one is doing tuning.
Re: Dyno sheet thread
Posted: Mon Sep 25, 2017 10:55 am
by vorpal
Pjackb wrote:Thanks Rob, shows the value of dyno tuning
Could you add if it was A or B cam
I 've never changed it and I don't believe the previous owner did... so I'll go with A cam
Re: Dyno sheet thread
Posted: Mon Sep 25, 2017 1:36 pm
by sfdaugherty
Here's the dyno sheet for my previous engine, an SR20DE S14. It was burning oil badly so we only did one run. I'll post the numbers for my SR20DE Autech as soon as I can. FYI . . . This was done at about 6000 ft above sea level. Results 127 hp 123 ft lbs of torque.
Re: Dyno sheet thread
Posted: Wed Sep 27, 2017 12:24 am
by RCMike
Since Photobucket died, so did my dyno sheets..
Dyno pull when new, before we changed the computer and street tuned it.. This was 155tq and 213 HP at 9k rpm...
After we added the second barometric compensator, and street tuned the motor to allow running up at 10k feet altitude. Then we ran it on a 105* day, club day, so 3 pulls no tuning.. It needed an adjust from the street tuning..
198hp, 153 tq.. 8k rpm max power
There will be another when we retune it to run e85...
Re: Dyno sheet thread
Posted: Wed Sep 27, 2017 6:43 am
by Pjackb
Johnw wrote:I had a chance to get my car onto the dyno on Thursday and was quite pleased with the numbers. The car made what I think to be great numbers with 110hp and 110ft/torque at the rear wheels. Using SAE conversion factor of 24% drivetrain loss calculates to 145hp at the crank. I only ran the engine past 6,500 once and you can see the number don't drop off much. The problem with the engine stumbling below 2,500rpm I was able to take care of later in the day with richer needles on the HSR carburetors. I would expect the numbers to go up slightly when the engine gets fully broken in, I have 400 miles on the engine.
I was hoping that others might be willing to post there dyno sheets to compare performance and add a little fact to the seat of the pants horse power discussion
.
Re: Dyno sheet thread
Posted: Wed Sep 27, 2017 6:46 am
by Pjackb
RCMike wrote:Since Photobucket died, so did my dyno sheets..
.
you should be able to download them that’s what I did for the pictures I needed
Re: Dyno sheet thread
Posted: Wed Sep 27, 2017 7:07 am
by Pjackb
Gregs672000 wrote:
Dynos vary by the way, so what is 120hp might be 130 or 110 elsewhere... I'm not sure how much they vary, but it would be important to use the same one if one is doing tuning.
Obviously dyno will be different
The main reason for me behind this thread is to get an image of how the different engine options and combinations deliver power and especially torque (hence why I hope we will get a few strokers) and help people have an image of the engine’s characteristic if they don’t get a chance to drive one first
For example if you read the SR forums you’ll come to believe the SR20DE has no torque YET when you look at some of the sheets the numbers are not too bad but more importantly the engine delivers 85% to 100% of it’s torque between about 2200rpm and 6500rpm.
To me that mean if you’re considering that engine but have hesitation because of torque you shouldn’t
Re: Dyno sheet thread
Posted: Fri Mar 30, 2018 2:01 pm
by Pjackb
Alvin wrote: ↑Fri Mar 30, 2018 9:12 am
We had the pleasure of dyno tuning Kurt's 1967 SRL earlier this week.
The U20 with Solexes, Steve Pettersen did a nice job setting this engine up:
At Z Car Garage
Dyno video:
[youtube][/youtube]
Dyno results:
Baseline was 99hp/107tq at the wheels
After Rob's tuning it picked up ~10% more power throughout the entire rev range, making 108p/114tq at the wheels:
An interesting tidbit, Sora Blue (Calspeed's now Rob Fuller's #0248) dyno'd at 108p/115tq in 2012!
Thanks for letting us tune your SRL Kurt! Let's do a run soon
After he completed the "gentle" break-in of his Hasselgren-built U20 with a thousands-of-miles roadtrip he wanted to have it tuned. He also wanted to test different Solex filter housings.
The U20 has a C cam, .040 pistons, 44 Mikunis, a lovely JT68 exhaust system and 9:5:1 compression on 91 octane:
On the dyno:
You can hear the Solex-U20 sing in this video below. Keep watching as Brian took videos comparing the open vs late elements...it's ALOT louder with the early style:
[youtube][/youtube]
And, the magic numbers...Brian baselined at 121hp/122tq and left with 142hp/134tq to the wheels:
Very nice power delivery! And a great example of how tuning is critical
Thanks Brian, your roadster is immaculate...and fast!
Wow Brians car made some amazing power! Thanks for keeping this thread updated! It doesnt seem too wild either, something that runs 91octane and is relatively tame it should last a really long time
Re: Dyno sheet thread
Posted: Fri Sep 28, 2018 1:39 am
by 2mAn
bump...
any idea if the pics can be fixed? sucks to lose that.
does anyone run the SK48? I see Greg had them at one point, anyone else? Bolt on with the Solex manifold, right?
Re: Dyno sheet thread
Posted: Fri Sep 28, 2018 8:15 pm
by Gregs672000
Yes, they bolt on, will need to make sure the linkage works well. However, there really is no need for a carb bigger than your 44. Not that there's any real problem running the 48s, but there's no advantage that I can see. I highly doubt you will ever want to run a choke bigger than say 42mm. My engine seriously breathes, but I run 37mm chokes and it has plenty of top end power. I may give up some top or peak hp, but despite the performance enhancements done to this engine that usually make them unfun on the street, this car can tool along at low rpm or start on a hill without problems. This won't be as easy with a bigger carb/choke. It also becomes a bit more difficult to jet the carbs for lower speeds due to changes in what they call "signal" to the jets from a larger throat (has to do with velocity). This is just my opinion, but based on years of running different carbs, from 44mm Mikuni with 34 chokes, then 37s, then a set of 48mm SKs with 39s, then 45mm OERs with 37s, then finally 45mm Dellortos with 40s and now 37s. Your milage may vary!
Re: Dyno sheet thread
Posted: Wed May 01, 2019 1:38 pm
by 2mAn
What is a safe estimate of drivetrain loss from engine to wheels? 15%? 20%?
Re: Dyno sheet thread
Posted: Wed May 01, 2019 3:04 pm
by Alvin
2mAn wrote: ↑Wed May 01, 2019 1:38 pm
What is a safe estimate of drivetrain loss from engine to wheels? 15%? 20%?
