Dynoed my L24 at Zcon

[Tony D]

If you indeed were at 10.5:1 and uncatalyzed, there should have been a distinct black soot coming out the exhaust during that timeframe. The inside of the tailpipe would be black at that time as well. If you didn't see any black smoke then that lends credence to the error on the dynos AFR calibration. Did you see him do a free-air calibration before he started the run, or at any time during the runs to recheck the sensor? I guess it's a moot point now, but generally you hit 10.5 and you will definately see some smoke. That is the limit of most WBO2's, the dyno we were on had a Horiba which we were comparing against, and it was dead on within 0.1 on the AFRs. When we showed 10.5 flatlined, they were sometimes going to 9.3! Having that extra span helps when you are doing initial pulls and need to rough-in the curve.

 

Good Luck on the tuning. I'll stick with clickety-clickety if at all possible. I did my time sitting backwards while someone else drove WOT down back roads!

[madkaw]

Thats's interesting, because I am chatting with frank on CZCC and he was the guy before me with his triple mikuni's. He bottomed out their scale at 9.3 or something and I don't remember any plumes of smoke. he did admit that his car is running stinky rich right now. I will have to ask him if i just missed the smoke

[30 ounce]

I appreciate all the replies guys. This is my first dealings with a dyno run and deciphering a dyno graph-so all of you probably know more then me.

 

As to certain aspects of the run;the engine was running rich at the time of the run. The foward SU piston needle was set too far up into the piston creating a rich condition. Rich enough to soot the plugs-so I figure that is what you are seeing with the low AFR. Needle was reset-plugs looked perfect.

The carb floats were set to stock specs at the time of the run, but either my measurements were wrong or the stock specs didn't cut it for this engine. After returning home from ZCON, I adjusted the floats by more then a 1/8" on the tab, and the plugs still look perfect and the engine wasn't as flat on top end-noticable improvement.

As far as the flat toque curve, I'm not sure what the deal is there, but this engine runs like that curve as far as having a very solid torque band across the rpm range. I am impressed how this motor will pull from any rpm.

 

Weebeezeed, I am 15 minutes from greenwood.

 

I will not be making any drastic changes based on this dyno run, but it did pick-up my richness problem, and it did show my leaness issue at the top end, so there is something to go by. I would like to find a point with my carburation that I atleast see some richness on the plugs, that i am making significant changes. As far as the 'set-em, forget-em" theroy, how is that possible. If I just went by the plugs and MPG and wasn't worried about anything else, I would have been happy with this dyno run. Now I have made a huge float adjustment(definetly not spec) and it runs better and still isn't rich. Bruce Palmer was the one to suggest float adjustment. Maybe the it is more then that, maybe the fuel pump is not maintaining the correct setting.

 

An interesting note; the Z before me that had triples on his engine was also showing a very rich condition and making less HP then me. Could it been the suffocating heat that day-95+ degrees and humid?

 

As far as the set and forget I was talking about the float levels only. You should not be making mixture adjustments with your floats! When you remove your dashpots and look down to the jet nozzle you should be able to see fuel just below the nozzle. If you raise the fuel level too much then you will have raw fuel flowing out of the carbs and hopefully on the ground and not into a cylinder wich will hydrolically lock your motor. Be carefull!! Once you have the floats correctly set the mixture screw, needle, possibly nozzle & damper oil is all you need to adjust. At least as far as the mixture goes.

Edited August 19, 2010 by 30 ounce

[madkaw]

Well I nhave been playing with the timing and I believe i left some HP on the table at Zcon. I guess when I set my timing before I went( 10 btc static), I didn't rev the engine enough to set total timing properly. I must have also reconnected the vacuum advance ASSuming that it would cut out at the higher rpm-so I was only running about 27-30 degrees at top end.

After reading some more i took the advice and just plugged the vacuum advance and set intial to about 21 degrees and I am running a good 36+ at the top end. Good thing about this is overall hp gain and no detonation at 2500rpm(wasn't too bad). The bad is giving up some mpg and I can actually smell the difference. So it's time to develope a mechanism to limit my vacuum advance and at the same time maintain my total. Anybody have any options they have tried? I am thinking of somehow limiting the throw on the vacuum rod so I only get about half of the 17 degree advance. I guess it would also be cool to beable to keep a lower intial and full vacuum, but modify the mechanical for a higher advance. Right now I am not experiencing any detonation but not sure without some dyno that extra full advance would be doing anything. it seems the consensus here is 36 is a good number, and Braap thought 38 was optimum.

 

30 ounce, I wasn't setting mixture with the floats, just trying to keep fuel in the bowls which would effect mixture at top-end.

[Lazeum]

I haven't been playing with distributors with advance before but Vaccum advance is effective when you get some vaccum in your intake (obviously). At WOT at the dyno, there isn't any vaccum since everything is wide open between your intake and the atmosphere. It should make no or very small difference to have your vaccum port plugged or not at WOT.

Vaccum helps pulling timing when you're cruising to help MPG. That's my understanding of Vaccum advance systems, we don't use it with Triple Carbs but it could probably help smoothen up the engine at low load.

 

Afterwards, you've experienced some weird results, it might be because you've passed MBT (Minimum Best Timing), all fuel might not have time to get fully burnt resulting in rich exhaust gases. Have you got some data to confirm or discard this hypotesis? Several Torque Curve vs. Timing @WOT for instance?

Edited August 30, 2010 by Lazeum

[madkaw]

No proof on the richness, but my mpg is definetly taking a hit from losing the vacuum advance. I realize that the vacuum advance is there for other then WOT, more for cruise and high vacuum conditions. just trying to get the best of both worlds-WOT performance and fuel economy at cruise. I was thinking of cutting the vacuum advance in half to see how that effects everything, just not sure how I am going to go about that. I have Mikunis sitting on a shelf, so I'm not sure how my findings with the SU's will translate to them once they are installed. Trying to learn and improve my understanding-but I can't complain about the way this engine runs.

[Noddle]

just trying to get the best of both worlds-WOT performance and fuel economy at cruise.

 

go EFI ..

[Xnke]

Or hook the vacuum advance back up and use it. Vacuum advance is exactly that, the higher the engine vacuum, the more advance you're running. I am not exactly sure how to modify the vacuum advance; other than to add or subtract you adjust the slot length in the dizzy, but you can lengthen the slot to delay advance coming in, and then add mechanical advance, or you can shorten the slot to speed up the vacuum advance, and subtract mechanical.

 

It'll be a LONG, LONG day on the dyno with a mechanical dizzy..

[30 ounce]

Rebello recomended 34 degrees total advance for my 3.0 liter with modified SU's and no vacuum advance. I ran it that way till I put on about 1000 miles and wanted to see what the vacuum advance would do. Seems to me its a little more street friendly to drive and my mpg went from 16-23.8. I need to put this on a dyno and get the most out of it. MSD makes a programmable ignition system where you weld you mechanical advance shut and program your advance with a laptop. I almost went for that but I think I'll see what I can do with what I got first.

[Mack]

go EFI ..

 

 

+1.

 

megasquirt is your friend.

 

then you can put the timing curve and fuel curve where ever you want it, when you want it.

Edited August 31, 2010 by Mack

[madkaw]

I would like to use the mechanical advance, but this e12-80 needs to be tuned to my engine. The e12-80 pulls too much advance at the wrong time for my application and causes detonation and does not optimize power. Why run 27 degrees total when you can run 35.I did look at the idea of slotting the pull rod, but I don't think there is enough rod to do that-but I'm still working at something to that fact. As far as being a long day at the dyno-if I have my ducks in a row and have several options to try during my dyno time, I can make effecient use of my time.

 

30 ounce, I think I am experiencing what you have now. I have suffered mpg for power, but I haven't really given up any drivability. The power is good everywhere and very smooth and predictable, just needs to be more effecient. I would like to cut the vacuum advance in half and see how close I can get to 36 degrees total without detonating. If I was able to make the vacuum advance somewhat adjustable it would give me several options at the dyno in a quick period of time. I would just be curious to see the numbers comparing what I ran at zcon(10 degree intial-27 total) compared to where i am now(21 initial-36 total approx.)

 

Fuel injection is great, but for performance you need to be ready to spend$$$.

I would like to go with a edis set-up and install a megasquirt and do the timing curve right, but for now it's going to be tweeking the e12-80.

[30 ounce]

I didn't notice any power loss when I connected the vacuum advance. It's a little more responsive to throttle input. Full throttle acceleration is the same. I'm running 11.5:1 compression, 490 lift 290 duration cam and don't have any preignition problems at all on 93 octane. 91 octane gives a slight ping when cruising up a hill so I'm right there at the edge. I'm using my 260z distrubutor (it was recently rebuilt) and all the mechanical advance is in by 2200 rpm's. I think you should try that MSD unit as it will give you a better spark and adjustability. You could pull a little timing out where it's pinging now and add some on the top end. (Actually I just want someone else to try before I do!!) If you switch to Mikunis will you be able to use the vacuum advance? Seems I've read that's not an option if you use tripples.

[madkaw]

I'm suprised that you could just "plug in" your advance when running 34 total, but I have no idea how much advance your dizzy vacuum pulls. What's you intial set at then.

 

Bottom line is that if you can do that and not detonate and keep all that top advance and good mileage your doing great! I believe I have one of the early electronic dizzys, I will have to look to see how much vacuum advance it has.

 

I think you are running higher compression, but you must have some overlap with that cam. Just curious-what kind of pressure do you get doing a compression test?

 

If I didn't mention it earlier, this dizzy is all in at 2500rpm. The vacuum advance is 17 degrees. So at 2500 rpm at a cruise/slight loading(going thru the neighborhood at slow cruise thru the gears) I had 10+17+17= 44 which from what I have read is not out of the norm, but at that 2500 mark is where I would here a slight ping.

Edited August 31, 2010 by madkaw

[Tony D]

Don Potter is dead, and you ARE NOT getting my recurved E12-80!

 

I don't even want to try to explain what he did (I have a clue by what he explained to me...), but I get stock timing (10 initial) and have a 36 total at that point, WITHOUT factoring in vacuum advance. I think it adds another 7 or 8 degrees to that total under cruise conditions.

 

It's the only car I have that I can still run 87 octane in during the summer that does not ping under heavy throttle or medium throttle on a 40C+day climbing the hill on the way home.

 

The 'ramp' on the backs of the centrifugal weights has had several 'steps' cut into it, and they along iwth the mating pins that they drive have been polished like crazy for smooth action. I don't know if the weight was changed or cut down I won't take it apart to figure it out either. The vacuum slots were altered but from a casual look inside it looks stock.

 

I had that done back in the early 90's, and the cost was not as much as a Megasquirt, but was MORE than a Megasquirt KIT!

 

I would suggest you find someone with an old SUN distributor machine, make good notes on where you are pinging, and then start simulating it on the SUN. From there, you can start grinding and filing the weights to tailor the advance curve to your liking. Without a distributor machine to do this simulation, you're pretty much hamfisting it as it's internal mods to the distributor you have to do to get the 'exact' curve you want. It's somewhat time consuming, but the results are amazing in terms of what the car can ingest, what kind of performance it delivers, and fuel economy.

 

This is like carburettors. Anybody who says this is 'easy' has never done it! And it's one of those reasons I LOVED it when MS-n-S came out with the ability to drive a single coil even on an 8X8 map. The 12X12's on the MS1 are 'click click click' and you're done!

 

It's just words on a page, and I understand that for most people that's all they are...but once you've gone through the process on a SUN machine, and tailored a set of advance weights to EXACTLY what you want on the car you have, you won't appreciate what I'm saying until you get your first standalone and set up an advance curve in about 3 minutes. Most cars don't need 'steps', it's a linear equation and it is super easy to program the bins. For that stock weights work fine. But when you start dealing with fuel that's crap and have various load issues or mixture issues from fuel delivery that demand some 'kinks' in that straight line from off-idle to 3500rpms the EFI stuff is WORLDS faster.

 

Remember, just because you got an MS doesn't mean it HAS to do the fuel. Or the spark. It can do either, and act as a neat datalogging box to boot!

 

Sadly, I'm a masochist, and keep looking for an old SUN Distributor Machine. "Just because I can do it, I should have the tool that lets me show off!"

 

You won't appreciate that until you do it. Don Potter was a god when it came to recurving the Datsun Distributors, and having done it myself in the past, the results he got with mine simply made me want to kow-tow and thank hiim profusely for sharing his magic. And there's no way in hell I will ever sell that damned distributor! So DON'T ask.

 

Good Luck!

[madkaw]

If you won't sell it, can you just take it apart and make an outline of the weights on a clean sheet of paper for a templet

 

From what little I've read of dialing in the dizzy, the reshaping of the weights is much better at controlling the mechanical input then messing with springs. My car ran so great at 10 intial with full advance, now I just need to find the secret combination to get the full advance to come in at the right time. This is going to take some serious R&D and many trips to ORP raceway-darn!

 

I will probably find a nice set-up and then I will be mounting the Mikunis--- to start all over again.

[Tony D]

No, it just takes putting it in the SUN machine and spinning it up to speed after each mod..."it's easy!"

[30 ounce]

My dizzy was rebuilt 8 years ago by an old datsun mechanic-racer. I don't drive my z much so it probably has less than 5000 miles since it was rebuilt. It is the stock one that came with my 260 so assumming he didn't change the vacuum it's probably 17. He was very proud of the work he did and I could tell the car ran much better at the time. Rebello told me to run the '83 dizzy when I built my 3.0 liter but this dizzy worked a lot better so...anyway I wish I knew what he did. I'm also running MSD 6al. I think my initial timing was at 8. I'll check this weekend and get back to you.

 

I have not done a compression test. The engine has less than 2000 miles on it and I've been more concerned with getting the carbs set and chasing the valve lash. They seem to tighten up a little and I don't want burnt valves. My cam is the Isky 490 grind and it does have a lot of overlap. 11.5 is what Isky recommended for compression. Also my combustion chambers were welded & completely reshaped to add compression and give a more detonation resistant shape.

[madkaw]

I also wonder what he did with that dizzy if your running 8 initial and still getting 36 total! You might find some reshaping of the mechanical weights or springs or slots for the advance-you better hold on to that dizzy. I think I will try and find another e12-80 dizzy and experiment with it and keep my original stock.

[Tony D]

I also wonder what he did with that dizzy if your running 8 initial and still getting 36 total! You might find some reshaping of the mechanical weights or springs or slots for the advance-you better hold on to that dizzy. I think I will try and find another e12-80 dizzy and experiment with it and keep my original stock.

 

YEP!

[johnc]

Don Potter is dead, and you ARE NOT getting my recurved E12-80!

 

I don't even want to try to explain what he did (I have a clue by what he explained to me...), but I get stock timing (10 initial) and have a 36 total at that point, WITHOUT factoring in vacuum advance. I think it adds another 7 or 8 degrees to that total under cruise conditions.

 

It's the only car I have that I can still run 87 octane in during the summer that does not ping under heavy throttle or medium throttle on a 40C+day climbing the hill on the way home.

 

The 'ramp' on the backs of the centrifugal weights has had several 'steps' cut into it, and they along iwth the mating pins that they drive have been polished like crazy for smooth action. I don't know if the weight was changed or cut down I won't take it apart to figure it out either. The vacuum slots were altered but from a casual look inside it looks stock.

 

I had that done back in the early 90's, and the cost was not as much as a Megasquirt, but was MORE than a Megasquirt KIT!

 

I would suggest you find someone with an old SUN distributor machine, make good notes on where you are pinging, and then start simulating it on the SUN. From there, you can start grinding and filing the weights to tailor the advance curve to your liking. Without a distributor machine to do this simulation, you're pretty much hamfisting it as it's internal mods to the distributor you have to do to get the 'exact' curve you want. It's somewhat time consuming, but the results are amazing in terms of what the car can ingest, what kind of performance it delivers, and fuel economy.

 

This is like carburettors. Anybody who says this is 'easy' has never done it! And it's one of those reasons I LOVED it when MS-n-S came out with the ability to drive a single coil even on an 8X8 map. The 12X12's on the MS1 are 'click click click' and you're done!

 

It's just words on a page, and I understand that for most people that's all they are...but once you've gone through the process on a SUN machine, and tailored a set of advance weights to EXACTLY what you want on the car you have, you won't appreciate what I'm saying until you get your first standalone and set up an advance curve in about 3 minutes. Most cars don't need 'steps', it's a linear equation and it is super easy to program the bins. For that stock weights work fine. But when you start dealing with fuel that's crap and have various load issues or mixture issues from fuel delivery that demand some 'kinks' in that straight line from off-idle to 3500rpms the EFI stuff is WORLDS faster.

 

Remember, just because you got an MS doesn't mean it HAS to do the fuel. Or the spark. It can do either, and act as a neat datalogging box to boot!

 

Sadly, I'm a masochist, and keep looking for an old SUN Distributor Machine. "Just because I can do it, I should have the tool that lets me show off!"

 

You won't appreciate that until you do it. Don Potter was a god when it came to recurving the Datsun Distributors, and having done it myself in the past, the results he got with mine simply made me want to kow-tow and thank hiim profusely for sharing his magic. And there's no way in hell I will ever sell that damned distributor! So DON'T ask.

 

Good Luck!

 

Tony, next time you're at the shop drop off that distributor. John Benton (http://www.bentonperformance.com) across the alley has SUN distributor machine and knows how to use it. We can map the curve.