Rev. limit WBX Digijet

[BuggyMan_Swe]

Did you guys ever find out if replacing the crystal is the solution for higher rev. limits with the Digijet?

[fastback]

I have not tested it yet....

[T4split]

A 8MHz chrystal was tested on a friends WBX today and it raised the rev limit accordingly. The stock one was in the 7.3 MHz range if I remember correctly. The Rev limit after the change was 6200 rpm and the engine ran perfect.
The engine is a 2.1 WBX, Digijet, Engle 130 cam, 1 5/8 primary tubes and a 2.5" exhaust, sligtly ported heads, 3 angle head job, and a raised fuel pressure. The engine runs VERY good and I hope I will post a video some day soon.

Next step is a new chrystal, a 9 MHz and bigger injectors.

[fastback on vacation]

Cool!
I have bought several crystals myself , but did not have enough time to test it out before i went on my holiday.
I bought 9 an 11Mhz to test with.

T4splitt: what kind of car is this engine fitted into??

[T4split]

A fastback. Sadly snow came here before we made any video session.

[mechano]

where is that cyrstal located , is there a information to read on internet about this , or can U guys describe , I am interested because I will use digijet on my 1776 typ1 engine..

[T4split]

Open up the digijet box and on the circuit board it is a Square thingy marked 7.2 or 7.25 MHz (if I remeber correct). Thats the Chrystal.

[WBX Man]

where ???

[Guest]

Ok, Jesper showed me....

[BuggyMan_Swe]

Hi again... tried replacing the crystal in a friends ECU and only got it to run smothly with an 8Mhz crystal... Even tried 11Mhz and the guy said there was no upper limit but it ran extremely bad under 4000rpm.
Its not a god solution to make the processor work faster without changing its code because you will make its internal clock run faster than it should and this I suspect shortens the injectors open time.
I might be wrong about this... and will get into the issue as soon as my own engine is finished.

[fastback]

Finally i managed to swap the crystals too im my ECU.
and can confirm my Swedish friends statement.
I used 8,3 MHz crystals and the engine seems to work just as fina as a stock....maybe my imagnination ..but it seems that the mod' suited my engine better (TCS-10 cam)

my theory is that since the stock 7,3 Mhz gives the ECU's rev limit 5500 RPM
the 8,3 gives it a revlimit ca.6250 RPM..

[Flagbuggy]

Hi Fastback

engine better (TCS-10 cam) ..[/quote]

So I take it that your motor is turbod also

[fastback]

Yes it's turboed.

[tencentlife]

I know for sure Digifant cuts off top rpm by cutting the fuel pump to half power, which it would have to do by "fluttering" the pump relay, because the only interaction the ECU has with fuel supply is to operate the pump relay. I'm all but certain Digijet does the same. Digijet doesn't operate ignition, but it does receive the rpm signal in order to know the engine rpm for its injection map.

So, maybe you could extend the top rpm simply by taking control of the relay.

Digifant operates the relay by providing the relay coil a ground path thru the ECU. The relay coil's power is provided to it when the main FI power relay closes, whenever ignition is switched on. If you just ran the relay coil's ground wire directly to ground instead of to the ECU, the pump would run continuously whenever the ignition was switched on, but the ECU wouldn't be cutting it off at 5600rpm.

[fastback]

When the RPM cut starts it is instant.
This would not happend with cutting the power to the fuel pump.
The fuel pressure would drop "slowly" compared to stopping injectors to fire.
I'd rather put my money on the control of the injectors.