Fuel/Ignition cut @ 5500 RPM only on dyno...

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Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby AvivB » Thu Mar 06, 2014 8:27 pm

Hi guys,

I have a weird issue that I cannot figure out and I need your help.

I have ST182 (FWD) with engine from ST185RC/CS.
When I swapped it, I also took the ECU, boost-pressure sensor, coil, MAF and igniting controller from the ST185 and put them in.

On the road, there is absolutely no problem and I can rev/boost all the way up to the red line at 7000 rpm.
But when I go on the dyno, it get fuel or ignition cut at 5500RPM!.

There are no CEL codes...
I tried to go back to stock boost levels (bypassing the boost controller leaving only the stock actuator connected)... no change...
I try to disconnect the ABS fuse... no change...
I try to disconnect the vacuum/boost line from the boost-pressure sensor... no change...

Any ideas?
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/Aviv

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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby underscore » Fri Mar 07, 2014 1:51 am

What kind of dyno, and how is it set up? Are you sure you're hitting fuel cut and not just hitting a limit of your fuel system? Dynoing tends to be done in 4th gear so yo may not notice it on the street because 5500 in 4th is going to be a high speed/load on the engine.
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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby AvivB » Fri Mar 07, 2014 8:00 am

Dyno type is DynoPack (the one who attached instead of the wheels).

We started on 4th and we thought we hit the speed limiter (as the ECU is the Japanese version) so we recalibrate the dyno and try again on 3rd but got the same issue.

AFR reading were super rich so I don't think it was a fuel issue.
(as I wrote, it also happen on stock boosting levels so the fuel system should hold it).
In addution, when I do it on the road with full boost, it stay super rich all the way to 7K RPM.
/Aviv

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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby klue » Sat Mar 08, 2014 12:49 am

sounds like you have the rpm limit set on the dynapack.
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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby AvivB » Sat Mar 08, 2014 8:39 am

There isn't any setup like that in the dyno... and the dyno cannot stop the engine from reving.

I've started to suspect that the ECU have some kind of "no load" rev limit and it somehow notice the almost no-load condition on the dyno.
But as far as I know, the only way the ECU can detect load is by throttle position and this was fully open.
/Aviv

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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby klue » Sat Mar 08, 2014 2:12 pm

AvivB wrote:There isn't any setup like that in the dyno... and the dyno cannot stop the engine from reving.

I've started to suspect that the ECU have some kind of "no load" rev limit and it somehow notice the almost no-load condition on the dyno.
But as far as I know, the only way the ECU can detect load is by throttle position and this was fully open.



Yes there is, its called " set speed" its on the main streen which displays your real time output. You need to have the gear ratio calculations done or it wont work properly.

The ECU does not have a no load rev limit, or else it wouldnt rev past 5500 in netural. The ECU detects load from the AFM nothing more.
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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby AvivB » Sat Mar 08, 2014 3:48 pm

We did the dyno gear ratio calibration twice, first of 4th gear and then on 3th gear when we thought we hit the speed limiter of the Japanese ECU...

I'm away from my car for the weeked but after it I'm going to try reving in natural passed 5500.
I have a vague memory that once I tried to do so I got CEL code...
/Aviv

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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby klue » Sat Mar 08, 2014 4:32 pm

AvivB wrote:We did the dyno gear ratio calibration twice, first of 4th gear and then on 3th gear when we thought we hit the speed limiter of the Japanese ECU...

I'm away from my car for the weeked but after it I'm going to try reving in natural passed 5500.
I have a vague memory that once I tried to do so I got CEL code...


speed cut is 180 on the jap ecu, 3rd gear shouldnt be doing that if my memorys serves.

if your getting a cel code and there is a rev limit, sounds like a knock code (52 again if the memory serves)
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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby brutekiller787 » Sun Mar 09, 2014 12:05 pm

Just a thought but what if the speed sensors on the back wheels are detecting a difference in speed and the rc ecu limits the revs?

Not sure if they had that back then but wouldn't that be some stuff.
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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby AvivB » Sun Mar 09, 2014 12:27 pm

brutekiller787 wrote:Just a thought but what if the speed sensors on the back wheels are detecting a difference in speed and the rc ecu limits the revs?

Not sure if they had that back then but wouldn't that be some stuff.


There is no 2nd speed sensor.
The only one exist attached to the gearbox.
/Aviv

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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby brutekiller787 » Sun Mar 09, 2014 2:27 pm

There are wheel speed sensors if the car has abs
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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby AvivB » Sun Mar 09, 2014 2:39 pm

brutekiller787 wrote:There are wheel speed sensors if the car has abs

You're referring to the ABS sensor exist on all wheels.
One of the tests we did was to disable the ABS system by pulling its fuse out... but it didn't help.
Also, as far as I know, there in no connection between the ABS control unit to the ECU so the ABS cannot cause rev limit.
/Aviv

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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby AvivB » Mon Mar 10, 2014 7:43 pm

I did a try today to rev up in natural... the rev limiter kick in only at 7K RPM... (as it should).
So I'm back to square one as I have no idea what happen on the dyno... :(
/Aviv

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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby underscore » Mon Mar 10, 2014 8:36 pm

Any chance you can try it on a different dyno?
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Re: Fuel/Ignition cut @ 5500 RPM only on dyno...

Postby brutekiller787 » Mon Mar 10, 2014 8:48 pm

Yea what underscore said might be your only option
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