Edman951

If the DME only reads up to 4.7V. I see 4.9 on my data log when running 18-19 psi.
And at that boost level i have a really hard time getting the car to run richer then 12.5.
If the DME read upto 4.7v that could explain the leaning out when I run high boost.
Because i got 72lb injectors and a GTS pump running 3bar static. so i can't be running out of fuel on that side of things.

Anybody got more info on this DME voltage thing.
How could i be maxing out the voltage if i'm not making super big HP.
Many other make more power then me and they don't seem to be maxing out the voltage. Unless i have never seen the post about the subject.

WesM951

Edman,
Maxing out the DME wouldn't make sense. Many people here have ran over 19psi on stock componets. (DME). John's ran 20psi on his stock setup (dme again).

special tool

Wes - they are talking about calibration. You can use 400 HP maf (or MAP) that gives 400 hp of air at 4.7 volts, or you can use a 650 HP maf that gives 650 HP of air at 4.7 volts.

jimbo1111

This maybe a limitation in the map piggy back you have. what fqs is the dme set at?

WesM951

d'oh.. *smacks head* guess I should of read the whole thread first lol.

GPF

My car also does the violent jerk/cutout thing at high boost. The problem is made worse because my boost fluctuates too much with the weather. If I set the boost to 18psi, on colder damper days I get this violent cutout problem all the time. If I turn it down, on warmer days the car is just too damn slow!! (everything is relative, isn't it!)

If this is true, why did Link scale the AFM Link with a 5v output?? Then again, I guess that would be the only way to retain the protection of the overboost trigger, and also explains why the original AFM also goes to 5v max.

There is, of course a cap that can be adjusted in the AFM Link which is normally set to 5.00v - but dropping that to say 4.65v would not change the actual air flowing and so could result in a dangerous lean situation? Depends on how the chips are mapped?

However, I'm pretty sure from my datalogging that I am not hitting any more than 4.6v max. (Although I'm running Danno's chips, which expect 3.0 bar, I have a 4.0 bar FPR and have scaled the AFM Link voltages down accordingly). But the violent jerk/cutout still happens. Danno did tell me that the DME relates the AFM voltage to RPM - so 4.5v might be OK at say 5,500rpm, but not at say 3,000rpm. You out there Danno? It's usually somewhere around 4,000 rpm that I have the problem.

No matter what the reason is, it's a real pita. If there is no other solution I guess I really, really need EBC!!

Has anyone else experienced this and got around it?

Conversely, does anyone have this problem but does not have the MAP conversion?

Regards

Graham

'88 Turbo S

Duke

Let's resurrecte this thread.. I myself got into these "problems" yesterday.
It seems like the Link box sends out a bit to much voltage at 20 psi and above.
Anyone managed to get around it using the AFM Link?
One solution might be to replace the 2.5 bar unit with a regular 3 bar MAP sensor within the box.

Gonna do some more testing in the next couple of days and log the voltage...

badcoupe

I can't wait to get my car back up a running and try to tune around it I think danno has some I deas as well for the problem maybe it's something that can be programmed out. Almost sounds like the map voltage needs scaled down all across the board?

jimbo1111

posted by Duke: One solution might be to replace the 2.5 bar unit with a regular 3 bar MAP sensor within the box.

Bingo! Most people that run there guru chips scaled back also limit the injectors from preforming the way they are intended. First try setting the fsq to 0. That will increase the fuel flow and scale back the voltage at higher flow. You will see less voltage with the same air flow. Much easier than changing the sensor.

Duke

I'm afraid that won't really help, since the main problem here is not fuelling but maxing out the voltage generated by air flow/mass. Now if there was an easy way just to limit the max voltage to ~4.5 volt...

GPF

Good idea to resurrect this - it REALLY PISSES ME OFF

If the problem is caused (as we all think) by the Link box giving too high a voltage to the DME which then interprets this as "must be too much boost", we need to scale down the voltage as you say.

Now, you can do this by dropping the Master AFM setting with the programmer which should get round the voltage problem - but you then have a fuelling problem across the board. This should be easier to fix though surely? eg Run higher fuel pressure to compensate, or increase the fuelling in the chips?

Either way you would need to get more fuel for a lower MAP voltage.

BTW - Even if you changed the MAP sensor as you suggest that would still be the case - and it's much easier to just decrease the Master AFM setting.


Regards

Graham

'88 Turbo S

jimbo1111

Posted by Duke: Now if there was an easy way just to limit the max voltage to ~4.5 volt...

I just explained how to do it. Don't discredit it until you try it. It does work. Remember that the dme is at a constant. The only thing you have for control is the input Maf/maf/afm and the output Injector size. If you scale the injectors to look like stock ones than your max capacity will be stock output. If you run the injectors at o scaling than the voltage will drop at the same air flow. Sometimes the answer so simple nobody believes you.

GPF

Jimbo,

Surely fqs0 gives the lowest fuelling (it does on my chips), so you would have to set the AFM Link to give a higher voltage?

Don't you really want to do the opposite? ie turn UP the fuelling on Danno's chips so you can then turn DOWN the voltage in the cells under boost??

Regards

Graham

'88 Turbo S

Duke

Too little coffee! You're right, of course it's possible to do it in that way as well...

GPF>> Some chips scale back the duty cycle in higher FQS-settings, so turning back the FQS-switch will rise the duty cycle for the injectors in the DME chip and then you can turn back the Master AFM setting.

jimbo1111

Surely fqs0 gives the lowest fuelling.

It's the other way around. 0 gives the most fueling. 1 and 2 scale back fuel.