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Megasquirt Dyno results

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Old 09-22-06, 02:04 PM
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Dyno results

We'll spent a couple hours tuning on the dyno this morning and have some really smooth curves. We came to the conclusion that the turbo I'm running is too small for the rotary tho (TD07-18A) we kept seeing boost hit 7psi @5500 or so and then drop off and we had my profec spec B II boost controller set to 15 psi. So my dyno operator wasn't familar with rotaries and we just figured the turbo is too small. I managed to get 293 hp @ 5600 rpm @ 12 psi. I was disappointed initially with this number but chalk it up to nervousness and first time on a dyno I missed the warning setting on my boost controller which was set to 7 psi and basically opened up the gate 100% so I am kinda bummed that I was too out to lunch to notice this setting, needless to say there's more to be had with my setup. I was happy with how smooth I was able to get the power curve.


Last edited by West-se; 09-22-06 at 02:06 PM.
Old 09-22-06, 06:23 PM
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awesome, it's good to finally see people posting numbers with their megasquirts!
Old 09-22-06, 09:59 PM
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the td07-18a

how does that compare to the td06-20g?
Old 09-23-06, 01:08 PM
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AFAIK, the TD07 has a bigger turbine housing as the TD0X designates turbine housing size there is usually a number with the housing like H,S or SH to determine the turbine wheel size, the next number is the compressor wheel size and the letter designates the style of the wheel.

the TD06-20G has a smaller turbine housing faster spool, but larger compressor wheel.
Old 09-23-06, 03:02 PM
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dont you find it a pain to set the boost with the profec spec II. its becaUSE boost is set as a percent of wastegate capacity. i think i have the same boost controller.
Old 09-23-06, 04:19 PM
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I've got the greddy profec spec B II, and boost is set by Kpa or psi, wastegate actuation is the gain value, which eludes my simple mind.
Old 10-01-06, 01:10 PM
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wow that tubo fals on its *** fast!
Old 10-01-06, 03:57 PM
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Ya thats what happens when an efficient wastegate opens up 100% @ ~ 8psi
Old 10-01-06, 05:26 PM
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woundup7 was having the same issue with his boost controller (could only hit like 10-11PSI tops). I think he just ended up zeroing out all the special settings and what not and now it basically works like a manual boost controller. You would have to ask him personally what he did. He is on nopistons.com most frequently.
Old 10-10-06, 06:10 AM
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Originally Posted by West-se
AFAIK, the TD07 has a bigger turbine housing as the TD0X designates turbine housing size there is usually a number with the housing like H,S or SH to determine the turbine wheel size, the next number is the compressor wheel size and the letter designates the style of the wheel.

the TD06-20G has a smaller turbine housing faster spool, but larger compressor wheel.

Interesting. I have a TD06-20G Greddy kit sitting in the garage awaiting an engine rebuild. I have been reading over the various Megasquirt posts and related sites for the past several months trying to come to a decision on the EMS route.

Out of curiosity, what size injectors are you running?
Old 10-10-06, 10:20 AM
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I am running 720 primaries and 1000 secondaries, but my duty cycles are at the limit at 15 psi, I will be changing the 1000's for 1600's over the winter.
Old 10-10-06, 11:44 AM
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quick note... if you're going to go with 1000's for primaries, you're almost guarunteeing that you'll have to use the hires code to get a decent idle. By then (actually in the next couple of weeks) the ms2/extra code should have rotary trailing and staged injection support as well, so that could be another option.

Many people have reported much better tunability with the msns-extra-hires code though. You just have to be sure to run high impedance injectors, or run resistor packs with low impedance injectors, as the hires functionality disables the low-z injector pwm features.

Ken
Old 10-10-06, 11:51 AM
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Thanks Ken, at this time I have no intention of running larger than 720 primaries since they work fine with the staging code and keeps mileage respectable
Old 10-10-06, 02:23 PM
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I'd suggest everyone with hi-z injectors or resistor packs make the switch to hi-res. The increased tuning resolution is noticable at idle, even with my 550 primaries.
Old 10-10-06, 05:44 PM
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How low can you set the opening time to with the highres code?
Old 10-11-06, 11:39 AM
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Injector opening time (iot) is a constant (at a given fuel pressure and control voltage) for a given injector design. This number indicates the actual time it takes for the pintle to pull from the closed to open position. The pintle stays fully closed during most of this time, and fires open rapidly once the coil has charged adequately to overcome the fluid and spring forces holding it shut. Hi-res code has nothing to do with this aspect of the fueling calculation.

To better understand the idle issue, and how the opening time relates, MS users have defined two terms: 'commanded pulse width', and 'effective pulse width'. The commanded pw is the actual duration of the injector pulse from the MS, and is normally in 0.1ms increments for MS1. As we know there is a delay, called the injector opening time (iot), that is factored in here, the injector really only squirts fuel for a time equal to the commanded pulse width minus iot, or the 'effective' pw.

Imagine a scenario where you have a 1.0ms iot, and at idle you are seeing a commanded pw of 1.8ms. The effective pw is only 0.8ms. Now consider the 0.1ms resolution of the MS1, and the problem is apparent. Imagine you are a bit lean at idle, and bump up the VE table in the idle area to compensate. Once bumped up high enough, the commanded pw will change from 1.8ms to 1.9ms. This seems like a fairly small change, but in real terms, the effective pw increased by (0.9-0.8)/0.8 *100 = 12.5%!

The hi-res code uses the hardware timers to drive the injector outputs, giving much better injector resolution, now limited by the VE table step sizes. Reducing req_fuel and scaling up the VE table accordingly maximizes this resolution. Users have reported a resolution of about 0.02ms with hi-res code.

The hi-res code and its development is documented in this 25-page thread:
http://www.msefi.com/viewtopic.php?t=18741
Old 10-11-06, 12:29 PM
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Thanks for the detailed explanation it makes much more sense now. So when I'm at idle and my PW1 is showing 2.1 - 2.6 that is my effective pulse width ? or commanded ? I always thought that those values where unusually high.

low-z 720cc pri / 1000cc sec
Old 10-11-06, 02:39 PM
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The numbers you see in the datalog, and displayed in MegaTune are the commanded pulse width. Your 2.1 to 2.6 sounds quite high to me, particularly with 720 primaries. I run 1.9 to 2.0ms at idle with 550 primaries and stock fuel pressure on a 13b na block, idling mid 12's afr.
Old 10-11-06, 02:49 PM
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yeah, with primaries that big, I'd expect you to be idling in the 10's with those pulse-widths.
Old 10-11-06, 02:51 PM
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Originally Posted by West-se
Thanks Ken, at this time I have no intention of running larger than 720 primaries since they work fine with the staging code and keeps mileage respectable
Oh yeah, and I forgot to mention, I misread your post before and thought you said you were going to go to 1000's for primaries and 1600's for secondaries.

I was recommending against doing that.

the hires code should make low-load and idle a lot more easily tunable though; even with the 720's.
Old 10-11-06, 05:50 PM
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I just went over my last datalog and once the car is warm pw is 2.5. My idle is fairly smooth and afr is 12.5-13.0. My pw limit % is 75 and my iot is 1.0 not sure what i've got happening to cause such high cpw ?
Old 10-11-06, 09:55 PM
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pw limit % is likely what's doing it.

If you're running high-impedance injectors, or low impedance with resistors, that should be 100%.

Setting it lower is likely making the injectors either shut too soon, or stay partially open (not even sure that's possible), which would cause you to show a longer pulse width for the same AFR.

Ken
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