3.0 24V "dies" after 6000rpm

Sape
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3.0 24V "dies" after 6000rpm

Post by Sape » Fri Jul 01, 2016 10:09 am

I have 3.0 24V engine in my 75 with Megasquirt 3 and it "dies" after 6000rpm. Do you have any suggestions, what can cause this kind of problem?

Only modifications are: MS3, 45mm inlet pipes, airfilter and 2.5" exhaust (original manifolds)

Here is dyno results. 239hp@5900rpm / 290nm@4810rpm.
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Re: 3.0 24V "dies" after 6000rpm

Post by Giuliettaevo2 » Fri Jul 01, 2016 3:19 pm

Fuel pump not delivering enough?

But 239 bhp with a standard engine is not that bad.
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Re: 3.0 24V "dies" after 6000rpm

Post by Duk » Fri Jul 01, 2016 5:40 pm

Yes an air/fuel ratio plot would help.
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Re: 3.0 24V "dies" after 6000rpm

Post by Zamani » Fri Jul 01, 2016 10:09 pm

Maybe cam timing should be checked as well.

BTW do you have more info on MS3 for the 24V?
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Re: 3.0 24V "dies" after 6000rpm

Post by Sape » Sun Jul 03, 2016 5:37 am

Giuliettaevo2 wrote:Fuel pump not delivering enough?

But 239 bhp with a standard engine is not that bad.
Yes, fuel pump might cause this problem. Have to check that.
Duk wrote:Yes an air/fuel ratio plot would help.
I dont have AFR map at the moment, but i have to check that also.
Zamani wrote:Maybe cam timing should be checked as well.

BTW do you have more info on MS3 for the 24V?
Cam timing should be correct :) But have to check that also some day.

What you want to know about MS3? I use MS3X V3.57 and there is some much options, that i dont use even half of them. :)
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Re: 3.0 24V "dies" after 6000rpm

Post by gtv-racer » Mon Jul 04, 2016 11:29 am

Post a tune and a log with mega log viewer and i'll have a look.
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Re: 3.0 24V "dies" after 6000rpm

Post by Steve R » Wed Jul 06, 2016 1:49 am

as GTV-racer says, please post an MS data log. & fuel / spark tables

I run a 24v on MS1 and had some similar teething troubles when I converted over from distributor to 60-2 trigger wheel & 6 COPS. An observation whilst MS is great functionality bang for buck, it is sensitive to input conditioning.

Check the rpm input is smooth and stable. Mine initially "died" at around 5000rpm, the cause was the ECU rpm was suddenly reading about 80k rpm at that point and then the rpm limiter slams the door... it would bounce around that rpm if I tried to go through it. The solution was additional smoothing circuitry on the input from the Alfa stock 60-2 crank position sensor. This was simply a small capacitor bridged from signal input to earth (to smooth input) and a resistor in series with the input in order to reduce the signal input power. I'll see if I can find the exact values as there was some trial and error involved.

Check soft limiter isn't accidentally set at too low rpm and pulling lots of timing out. (bit obvious but worth a check)


Good power on that motor though! but as you say an unusually sudden drop off.
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Re: 3.0 24V "dies" after 6000rpm

Post by Sape » Wed Sep 07, 2016 9:45 am

Here again.
Steve R wrote:
Check soft limiter isn't accidentally set at too low rpm and pulling lots of timing out. (bit obvious but worth a check)
Yes, thats a bit obvious but that is main reason for that problem. Soft limiter has set 750rpm before hard limiter (6800rpm) and i dont know why... I set it in 100rpm before dyno, but maybe i forget to save the file or something.


Here is my fuel and spark tables, if somebody needs :)
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Re: 3.0 24V "dies" after 6000rpm

Post by Steve R » Fri Sep 09, 2016 2:43 am

Hi Sape,
Glad it was that simple ! Does it now rev out fully and with decent power to 6.8k?

I've also set rpm limits quite cautiously for the 24v, similar to yourself. Soft set at 6900 pulling 13 degrees timing out, hard at 7000. This is just to get a slightly less abrupt "stop" as the motor hits that rpm in first quicker than the tachometer needle can sweep round. For info the factory 164's have a 7200 rpm limiter, and other sources state a good condition 24v should be OK up to 7800, so we are both comparatively safe with our lower limits.

Here's my fuel and spark tables for info, ignore that the actual numbers differ as our set ups are different, but the shape and slopes ought to be similar. As an observation, I note that your spark table is flat across load, whereas you could add progressively more advance at lower map values for better drive-ability. Our numbers at 100 MAP are pretty similar though, i.e. normally aspirated wide open throttle :-)

My tables are a bit odd for two reasons, so please don't bother copying them! Partly I'm tuning around the engine being prone to stalling due to having a 7.5kg flywheel and the extra load of the supercharger with larger throttled volume too. Partly I'm running overly rich at load for added safety when going into boost, but will lean this off when on a dyno.
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Re: 3.0 24V "dies" after 6000rpm

Post by Sape » Mon Sep 12, 2016 1:17 am

Steve R wrote:
Glad it was that simple ! Does it now rev out fully and with decent power to 6.8k?
Yes now it revs pretty good to 6800rpm. Thanks to you! :)

I also have some other problem with my car. When you accelerate hard with 3. or 4. gear it starts miss firing(?) in the high revs. With 1. or 2. gear it doesn't have this problem, but it usually starts when you change 3. to 4. gear and revs is something about 4500rpm. When it do this, car wont accelerate any more and it loses all its power. I'm not sure is it miss firing or what, but it really losts all the power. Any suggestions what could cause this? I have already changed spark plugs, coils and ignition amplifier (if that is correct word in english :) ) but still doing this. Could too early timing cause this?
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Re: 3.0 24V "dies" after 6000rpm

Post by gtv-racer » Tue Sep 13, 2016 7:56 am

Sape wrote:
Steve R wrote:
Glad it was that simple ! Does it now rev out fully and with decent power to 6.8k?
Yes now it revs pretty good to 6800rpm. Thanks to you! :)

I also have some other problem with my car. When you accelerate hard with 3. or 4. gear it starts miss firing(?) in the high revs. With 1. or 2. gear it doesn't have this problem, but it usually starts when you change 3. to 4. gear and revs is something about 4500rpm. When it do this, car wont accelerate any more and it loses all its power. I'm not sure is it miss firing or what, but it really losts all the power. Any suggestions what could cause this? I have already changed spark plugs, coils and ignition amplifier (if that is correct word in english :) ) but still doing this. Could too early timing cause this?
I think your fuell table is a strange and your spark table also. It looks like the fuell table compensate's the bad spark table. They just don't make's any sence . not trying to be a bitch :oops:
they should look a more like SteveR's one.

And once again post a log and a tune and we might can help you. All we are now doing is guessing....

I think your Engine is at risk....
Last edited by gtv-racer on Wed Sep 14, 2016 6:19 am, edited 2 times in total.
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Re: 3.0 24V "dies" after 6000rpm

Post by Murray » Tue Sep 13, 2016 3:39 pm

Sape
Have you tried running the "Auto-tune" feature in Tuner Studio.I messed around doing it manually and got things pretty well sorted,but when Auto-tune became available it really took off the rough edges.Power kicked up a tad and torque is excellent.
That takes care of fueling but spark is another kettle of fish.If you follow the traditional recommendations you're missing the party !
I've spent a fair bit of time (I'm a certified auto tech.with specialty in Euro cars). Playing with this aspect of our nasty little Hemi can change it's personality.I believe you're rolling a 3.0L so what I've observed on my 2.5 may not apply precisely but I suspect the general principles apply.Hemis love advance in the right places.I've attached my spark table.I've run it maybe 4 years,car is driven enthusiasticly and has considerable amount of track time - big real tracks - Watkins Glen,Mossport, Mont Tremblant etc.My little monster uses no oil and sings a really sweet song.Play with your timing and see how it goes.Keep in mind that your playing with your engine's heart so be fine tuned to any unusual sounds particularly knocking from pre-ignition.Don't want to burn little holes in those pretty little pistons.Enjoy the voyage the end result is sweet.
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Re: 3.0 24V "dies" after 6000rpm

Post by Duk » Tue Sep 13, 2016 7:00 pm

It is going to be dependant on what fuel you're able to run in the car, but your full throttle, high RPM ignition timing does look pretty conservative compared to what you'd expect to see and compared with what others have shared.
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Re: 3.0 24V "dies" after 6000rpm

Post by Steve R » Wed Sep 14, 2016 12:38 am

Sape, that's very odd, especially as it once made good power on the dyno.

Note the use of the word "once", did the car sit with unused fuel in the tank for a for a while before the dyno? (months, years). I ask as the symptom sounds like fuel starvation at high load, being not noticeable in low gear at you aren't at those rpm's for any length of time, but the missfire becomes noticable when pulling hard in a higher gear.

Check fuel delivery volume and or pressure. Change your fuel filter, any lose bits of crud will have found their way here. If it's running lean the engine is at serious risk under load - do you have an O2 sensor to check?

Assuming your hardware changes are good it doesn't sound like a Magasquirt issue to me as 239bhp is very good. Megasquirt wise maybe check:

Ignition. This is a bit of a long shot - if you use active dwell make sure it hasn't been reduced, or try adding just a few of tenths of a milisecond to coil charging time. (gives stronger spark, more complete burn). Only add a little as the coil(s) can be overheated and fail.

Fuel. If you've subsequently changed any ignition timing for more advance then you'd probably need a little more fuel at those load points too (otherwise might be lean).

I suspect fuel delivery capacity first, but as others rightly point out we are just guessing from afar.

Hope it's resolved soon.
S
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Re: 3.0 24V "dies" after 6000rpm

Post by Steve R » Wed Nov 02, 2016 6:23 am

Hi Sape, did you get to the bottom of this?
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