Dyno sheet thread

[Gregs672000]

Did some more street tuning today, but ultimately determined that I have an intake leak on the rear carb rubber isolator manifold gasket. Good old carb cleaner testing. I had tried to tighten them and the fronts were good, but looks like the rear need more attention. Probably why the MAP was jumpy on the tuning screen and on the vacuum gauge I hooked up a while ago. Noticed some spark shake and found the crank pick up was a little too far from the trigger wheel (1mm or less) so I fixed that and went back to the Motocraft coil pack and it appeared better on the timing light (damn POS light though... works when it wants to). So, since I'll be pulling the carbs anyway, may as well fit the 40 chokes?

[SLOroadster]

I'd say you might as well. I'm running the 40s on a stock (worn out, zero adjustment on the valves. Valve seats are concave.) head and a B cam and it doesn't suck. With more cam, a ported head (that has valve seats that are in good shape) and way more compression, I'd guess you will find some power. You have way more done to your engine than I have done to mine, so I'd have to assume you should make more power than I can.

Will

[Gregs672000]

I attended to the intake leak yesterday, removing the rubber insulators/carb mounts and sealing up the gaskets. While the carbs were off, I switched to the 40 chokes just to see how it would do. While I think the leak issue is solved, there remain other carb issues that won't allow me to run the 40s right now. I'm having problems with the accelerator pumps. I recently bought a step larger set (60s) but discovered that two of them were not made correctly (it's the jet for sure, not the system, determined through a process of elimination... they just don't squirt right and half as much), so it would immediately stumble lean at the slightest touch. The 55s were just not enough, nor do I think the 60s would have been either. And then I remembered why I had gone back to the 37 chokes from the 40s before... the Dellorto accelerator system is weak. The increased airflow from the bigger chokes just exacerbates that problem. I've noted (with the carbs off) that the pumps need more movement of the throttle before they squirt. Unfortunately no matter what adjustments I tried I couldn't get them to be more immediately responsive. Without a very fast response as I tip into the throttle, it goes lean, and it just gets worse with the more airflow. That makes it very irritating to drive. If I was heavy footed and got the pumps more involved, it was better and there was no doubt that it was clearly making more power above 4000 rpm, so I'm motivated to pursue a solution. After giving up and going back to the 37s the engine actually felt choked down... but it drove much nicer, while still having the same but much less noticeable lean pump problem.

So, before I can run the 40s I have to figure out how to get more from the pumps. A few steps bigger for sure, but I'm not convinced that will solve the problem if they don't kick in faster, and if too large may just dump a bunch of fuel for too long a time.

Man, I'd kill for a really nice, self tuning EFI system I could afford right about now!

[Pjackb]

This John Geist race engine build by David Taylor in Australia
The graph is on a very accurate engine dyno, not bad for a 50 years motor

4B03248D-4A94-40D7-9684-6328BA09CFB9.jpeg

[Gregs672000]

So I looked up how to calculate horsepower from torque, and found the following: (torque x Rpm) ÷ 5252 = hp. However, when I do this none of the hp numbers posted, including my own, match what the dyno said. Example mine at (130 torque X 4800rpm) ÷ 5252 = 118hp, not 139. Is that hp at 4800rpms? What am I missing?

[Pjackb]

So I looked up how to calculate horsepower from torque, and found the following: (torque x Rpm) ÷ 5252 = hp. However, when I do this none of the hp numbers posted, including my own, match what the dyno said. Example mine at (130 torque X 4800rpm) ÷ 5252 = 118hp, not 139. Is that hp at 4800rpms? What am I missing?

Yes HP at given RPM
If your 130lbs/ft was at 6000rpm hp would be 148

[Solex68]

So I looked up how to calculate horsepower from torque, and found the following: (torque x Rpm) ÷ 5252 = hp. However, when I do this none of the hp numbers posted, including my own, match what the dyno said. Example mine at (130 torque X 4800rpm) ÷ 5252 = 118hp, not 139. Is that hp at 4800rpms? What am I missing?

Yes HP at given RPM
If your 130lbs/ft was at 6000rpm hp would be 148

Impressive Greg.

[Pjackb]

It obviously works both ways
If you wanted to know how much torque the Geist engine had at 6K rpm
200hp x 5252 = 1 050 400
1 050 400 / 6000 rpm = 175 lb/ft or torque

Ps this why the small Honda engine even though they have little to no torque have such impressive HP number
100lbs/ft when you’re spinning at 8500rpm is 165hp

[Gregs672000]

Thank You! I've been looking over the various dyno runs posted here with U20 "solex" type carbs/ configurations, and the various SR20s (minus Mikes ridiculous version which I love) normally aspirated of course, and looking at peak torque and rpm in comparison to build or cam etc. Wondering if I can evaluate things like cam timing, carb venturi sizes, etc based on peak torque and rpm... what should this engine be doing based on how it was built (i.e it should be breathing) and what might improve or hinder that? Ya know, just thinkin...

[Gregs672000]

For example, there are a few U20 B cam solex engines posted that I think would benefit from some cam retard since the peak torque is at a low rpm... but I'm just spit ballin...
I also note that the best U20 ran a C cam which is a higher duration profile... had the best torque and hp numbers at a higher but reasonable rpm. For what ever reason that engine seems happy, and these reasons can be many (not just the cam)! I wish all the data was from the same dyno of course but that's Not possible! Hey, it's winter... can't drive it but I think about it!

[Gregs672000]

Thought I'd throw this latest pull on this thread as well as on the EFI conversion thread just to be consistent.
Unfortunately the engine was drowning with a 10 to 1 air/fuel ratio above 5000rpms, so it struggled to rev and you can see the engine waver on the graph.
I did this pull to document before and after the EFI conversion and hoped to get higher final carburetor output than the previous pull which was done on 3/4 throttle. Currently its running 45mm Dellortos with 37mm chokes. Ratio on the street was 11.7 to 1 max, but not on the dyno. Once the EFI is tuned and working well, I'll do another pull and post. After that I may play with cam timing if it's still dropping off after 6000 rpms, as I expect this cam to be good to 7000. Decent torque was available down low and peeked at 4700rpm, which makes sense with the 280 duration (same as a B cam) so I think it's more air/fuel ratio than anything.
142whp, 134lbft torque

[Pjackb]

Thought I'd throw this latest pull on this thread as well as on the EFI conversion thread just to be consistent.
Unfortunately the engine was drowning with a 10 to 1 air/fuel ratio above 5000rpms, so it struggled to rev and you can see the engine waver on the graph.
I did this pull to document before and after the EFI conversion and hoped to get higher output than the previous pull which was done on 3/4 throttle. Ratio on the street was 11.7 to 1 max, but not on the dyno. Once the EFI is tuned and working well, I'll do another pull and post. After that I may play with cam timing if it's still dropping off after 6000 rpms, as I expect this cam to be good to 7000. Decent torque was available down low and peeked at 4700rpm, which makes sense with the 280 duration (same as a B cam) so I think it's more air/fuel ratio than anything.
142whp, 134lbft torque

That’s pretty impressive power for a street U20 Greg
I know the engine has seen many changes over the years but it would be interesting to share the current basic formula
Hope you don’t mind me sharing the sheet with a few folks

[Alvin]

Thought I'd throw this latest pull on this thread as well as on the EFI conversion thread just to be consistent.
Unfortunately the engine was drowning with a 10 to 1 air/fuel ratio above 5000rpms, so it struggled to rev and you can see the engine waver on the graph.
I did this pull to document before and after the EFI conversion and hoped to get higher output than the previous pull which was done on 3/4 throttle. Ratio on the street was 11.7 to 1 max, but not on the dyno. Once the EFI is tuned and working well, I'll do another pull and post. After that I may play with cam timing if it's still dropping off after 6000 rpms, as I expect this cam to be good to 7000. Decent torque was available down low and peeked at 4700rpm, which makes sense with the 280 duration (same as a B cam) so I think it's more air/fuel ratio than anything.
142whp, 134lbft torque

Great power! Is this stock compression and 87 octane? What is total timing?

[Gregs672000]

Stock compression... Hahaha! Alvin you know Better! Too high for sure, but I have decided to work with what I've got on 92 pump with some octane boost on hot days. Once the EFI is done and tuned to the best i can get it, if the compression remains an issue the choice will eventually be 1) live with it and add whatever octane boost is necessary or 2) tear it down and machine the pistons for a lower ratio (11 or so). I'll decide then! I need to see a clean pull with a 12.5 to 1 ratio to see what the cam is really doing. That might open up some cam timing adjustments to adrress the compression too. Right now it's drowning in fuel so that's got to be fixed first. Plus, i must be getting older, but I'm finding it's not all about the most peak power it can make but what it drives like that's becoming more important to me.

Specs on this engine:
"Stage #3" head porting by Progressive Automotive, Steve Haniford. 48mm intake 38mm exhaust valves on 8mm strems, L-series retainers/lash caps.
Cam: Isky Z-197 280 duration (246 duration at 50thous), .384 lift + rocker ratio of 1.396 = .536 lift. (Note: with this cam, the intake valves hit the block even after being eyebrowed more, watch clearances). JT adjustable cam gear, currently set straight up. Head water jackets to the intake are plugged (that chamber is now used to supply a manifold pressure signal to the ignition system).
Stock block, bored 40 over, Arias forged pistons, machined to 11.7 to 1 compression, Total Seal rings.
Balanced crank/rods, aluminum flywheel, stock clutch.
Crank fired ignition by Mega jolt (distributor-less, coil pack wasted spark system based on Ford EDIS system), custom timing map (always a work in process!) Total timing 30 degrees at WOT Max safe torque. I could drop it 2 more degrees and give up 2-3 HP, and that may be a safe trade off for engine safety. So, yes, the compression ratio vs octane issue raises it's ugly head. I'm cheap and don't want to run race gas in it all the time. Live and learn!
Exhaust: Deans header (the larger one I think, but not the most current?), 2 1/4 exhaust to a Dynomax turbo muffler, then 2 1/2 to a Monza tip.
Carbs: Dellorto DHLA 45C, 37mm chokes, Mikuni velocity stacks inside Ram Aire filters. Glow Shift Wide-band O2 sensor for tuning. Electric fuel pump.

So ya, it should do better, and I expect it will, but one never knows! I truly feel the EFI will be the final piece to the puzzle outside of the compression ratio issue. But of course, I've got to get EFI to work. I'm working on the wiring now. I look forward to having a computer helping me tune it!

[Daryl Smith]

Greg,
While you may be disappointed with the peak power output (rightly so), I'd like to point out a couple of positives....

1) other than a small hiccup at around 5700 rpm, there is a very steady, smooth output from your engine, without the up and down spikes seen in many dyno charts. I do think you will see a decent power increase with the A/F ratios sorted.

2) The 1500 rpm spread between peak torque and peak horsepower, imo, shows a very tractable engine. It will only get better when sorting the A/F ratios. I have seen dyno charts that show 100 rpm between peaks, and others that show 2000+ rpm between peaks. Typically the wider spread (to a point?) between peaks will be a much easier engine to live with, and likely faster overall, even if the narrow spread engine has a higher peak output.
A really good way to compare dyno charts is to calculate the 'average' power/torque over the operating range, say between 2000 and 6500 rpm for a street engine, or similar....The engine with the higher average power/torque will be the faster one. Using 500 rpm increments from 2000 to 6500 gives you ten datapoints to average, which should be enough.