Dyno Tuning of SRL 0427

[Alvin]

With a few adjustments, it made 179hp/149tq at the wheels, on 91 octane. I thought she was quick when Diamond gave me a ride back in August, but now it must absolutely rip

Alvin:

Nice to have something to compare.

Mine only put out 160hp and 139tq (also on 91 octane). The main difference is probably that he can run that beautiful factory stainless steel header. Other differences might be the altitude (6000ft) and the dyno. I would think that dynos would compensate for altitude but I’m no expert.

Fun fact: it put out 165hp when the k&n air filter was removed. 160 hp 139 tq.jpg

Shannon

Shannon, I think the altitude is a major factor, especially on NA cars.

[Gregs672000]

Thanks for the curve post... but I must be understanding something wrong... example: 2000rpm, showing 17 degrees advance but with an additional 17 more static puts it at 34 total; 4500rpm at 28 plus the 17 for 45 degrees total (!)... I'm confused (not the first time!).
When I get some time to run the car and hook up the ol computer I will pull and post my current curve. I hear you on wanting the whole day on the dyno, especially when you're trying to get cam timing, jetting and a new ignition working right! (I tried to cram in too much). But what a difference it can make. I went BACKWARDS at one point post mods that should have gone quite the other way (and that led to checking cam timing and JTs adjustable gear...).

It is noted there are a few variables on actual horse power dyno to dyno and location to location, but regardless those are VERY impressive numbers showing a very healthy and well built engine... congrats! I would be very happy with those numbers, and my engine is not stock. Excited for you man, well done!

[theunz]

Wow 7 hp. just from the air filter is pretty impressive! Curious though, Brian's engine is not highly modified, so one would think it's air requirements would not be much greater than a stock production solex version. It's hard to imagine that Nissan's engineers would build a filter without excess capacity. So, is it JT's wide filter or the built in velocity stacks allowing the increase in power? Either way it bodes well for Jim's air filter set up! And Jim, could your wide filter element be used with the late style air cleaner?

[JT68]

The numbers make sense. A fresh Bcam solex engine with proper jetting, and optimized tuning/timing (electronic distributor, dyno time and tuning expertise) should come in at just about 150hp. (Everything has to be right)

C-cam adds 5-7 at 7k
Super free flow 2" exhaust adds 5-7.
Open AC w/ 2" element adds 5-7

So all that adds up to about 165 crank HP or so, which is pretty close to measured I believe.

One important point, the distributor doesn't ADD any HP (you can get the same result with EI, crank fire, etc.) The engine doesn't care what the spark source is, it just needs a hot spark at precisely the right time.

Whats amazing about the 123 distributor is you can optimize torque THROUGHOUT the powerband by changing the curve like a modern ECU. That's almost impossible to do with a mechanical dist. (Requires a distributor machine and spring assortment, and a dyno) You can even have different curves for cheap gas, good gas, AV gas. Being able to change the curve so easily is very slick. It probably paid for itself just in reduced dyno time since you can easily spend a whole day tinkering with distributors and everything else--$$$ on a dyno

Must be a ton of fun on the street now!

Best, jt

[AidanDawn2000]

Great to have some objective numbers in here. This car was fast before but I bet it absolutely rips now!
And the best part is that I can now shamelessly copy your curve and save on dyno money

[AidanDawn2000]

[quote="Gregs672000"]Thanks for the curve post... but I must be understanding something wrong... example: 2000rpm, showing 17 degrees advance but with an additional 17 more static puts it at 34 total; 4500rpm at 28 plus the 17 for 45 degrees total (!)... I'm confused (not the first time!)./[quote]

Brian doesn't mess around! I think part of the logic behind feeding in so much advance early is to help negate the lag you get waiting for the C cam to "spool up"

[JT68]

Lots of engines will make max power with final timing into the 40's. (depends on SO many variables) Problem is with a mechanical dist, all your timing is in by 3-4k, so if you set it for final timing that early, you'll be preigniting miserably all across the power band. Necessary compromise.
Its harder when you have a 10+:1 engine you are trying to tune on pump gas. or even worse, your compression ratio varies cylinder-cylinder etc.

"And the best part is that I can now shamelessly copy your curve and save on dyno money -- ''

I know Aidan was kidding, but the Alvin/Rob/Dynoman still gets his due.... Any difference in the engine and exhaust can easily require several degrees of timing change at any rpm, so every car/engine will be a bit different since every rebuild is different (there are no roadster "production crate engines").

Like Greg often says, its all a system and everything will either add or subtract power depending on the combinations:
Carb/jetting/temp/altitude variations +/- 0-15+hp
Cam timing variations (rem 2 cam degrees is 4 crank degrees) - affects all valve opening/closing points +/- 5-10+hp
Valve/Cam/rocker wipe, & lift differences -affects all valve opening/closing points +/- 5-10 hp
Individual cylinder CR's +/- 5-10 hp
Exhaust backpressure +/- 5-10 hp (more loss if highly restrictive)
Header design specifics +/- 5-10 hp
General health of the engine +/- 0-25+hp easy
General health/timing of the ignition system +/- 0-25+hp easy

These are just general rules of thumb, not precise. If your engine is off the mark you can see the impact. If several subtract, things get pretty sad.

Never-the-less, Aidan's right it would SAVE on dyno time. If I was doing it, It take Brian's curve, take about 5-7 degrees out at most points (17 is fine for initial) and work my way up on the dyno/street avoiding spark knock all along the way. Probably take 1/2 the dyno time if everything else is in order. Of course if you make any significant changes to the setup: Go back to start.

You guys are having too much fun out there! Excellent work.

[Gregs672000]

So that thing is really running 45 degrees total advance at 4500rpm!? My engine would blow up (11.7 to 1 compression) I think! As JT said, every engine is different. The ability to easily adjust the timing anywhere I wanted in the curve was one of the main reasons I went to megajolt (and to get rid of any timing slop from the dizzy/gears etc since it's crank fired). The 123 dizzy makes that even easier than the megajolt since you don't need a lap top (I've carried one with me on long trips just in case). Adjust it with your phone? Wow, that is really cool, and had it been available I would have strongly considered that route. The only advantage with the megajolt is the rock solid signal off the crank, no slop possible, but that may be inconsequential for most engines.

I suspect the built in velocity stacks in the original and JT versions of the air filter are the likely difference there, and another reason why I wanted velocity stacks inside my air box, which makes it a bit more difficult to design for easy installation. They do make shortie stacks which may work for those running after market KnN style individual filters (2), and they have been shown to flow as much air on top as the longer stacks (with just a tad bit less torque than the longer ones at lower rpm). Air does not like sharp edges or radical turns.

Really good info posted... I've got the tinkering bug again!

[Gregs672000]

Thought I'd revive this thread since I've been doing some tuning. I've been chasing a few issues that are not new to this engine but seemed to carry over from the previous version, and I think I've learned some stuff. Issues: Variable air/fuel ratios, mainly at idle, where I can get it set and relatively happy with a ratio in the 14s, but after driving it a bit sometimes it will read as rich as 12.0-12.4 when I stop and idle. It will eventually go back to the 14s sometimes, but not always. I installed a fuel pressure regulator (again) set at 2lbs, even though my electric pump is only 3.5lbs (I confirmed that pressure in line) and the Dellortos should be fine at 3.5lbs. Goal was to eliminate fuel level changes in the carbs as that effects the jets. Result: No change, so it's not a float issue. I had also noted that the engine became "rumbly" and uneven below 3000 rpms, like it wasn't firing all the time. I played with all kinds of jetting options, balanced the carbs really carefully (very sensitive) checking flow at various rpms but it still persisted. Got out the vacuum gauge and hooked it up to my set up (ties all 4 manifold runners into a tube that provides manifold pressure to the megajolt box)... whoa, what's happening here? Vacuum is jumping all over the place and would not settle down until the engine was reved above 3000 rpm, and then it settled where the gauge said "late ignition timing". But I was more worried about the jumping needle, that can be valve troubles. Perplexed, I set up the gauge to read each cylinder one at a time and found they all worked fine, swinging back and forth between 5 and 20+ with each rotation. I reattached the whole system, hooked up the gauge to the common port and now had a much better and more stable reading, more in 14-15 hg range which is low but likely due to the cam (yes?). Since it had improved, I realized I had probably stopped or reduced a vacuum leak. Checking around with carb cleaner as I have done countless times found some change in engine speed when I sprayed the black carb to manifold mounts, so I'm thinking now that my variations in idle richness and some of the swinging vacuum gauge readings are due to intake leak(s). Today was not the day to pull the carbs, and since it was improved a lot I decided to see about this "late ignition timing" the vacuum gauge indicated, so out came the laptop to adjust the timing. Went for a drive, would listen to the engine while trying to watch the computer screen, the A/F meter and drive at the same time... a long quiet country road is best! Advanced the timing a fair amount, ending up at a max of 42 but more often running 39-40 max based on load, wanted to be nearly all in by 4000rpms. Still need to listen some more and be careful given this engines compression, but I rarely heard ping (4th below 2500 with fairly hard accelleration so I pulled a little more out) though top end is harder to hear. The high advance at low load gets rid of the "blap blap blap" on decleration down hills etc, much nicer. Any opinions welcome! I wasn't able to get the gauge to change more than 1-2 of vacuum, but it did lead to a better timing map, which is why I decided to post here in case anyone else is considering a megajolt or is using the 123. They can really help, and one thing for sure with the MJ there's no more spark scatter!

[Solex68]

How much is a tuning session?

[2mAn]

Greg, head to Carb Connection. They should be able to get you dialed in