I think this might be my last problem to fix for my mini-me swap.
I have a Zdyne 1 wire vtec conversion ECU
It has a cold rev limit of 6800 RPMS and a hot rev limit of 7800 rpms.
The engine will not rev past 6800 RPMS even though its fully warmed up.

Logically, I would think the problem would have something to do with the coolant temperature sensor and/or wiring. I get no ECU engine codes and everything runs normal. However, I will get a code 6 if I unplug the harness as I should.

I followed the helms manual and tested the sensor. When the engine is warmed up, I get 200 ohms at the sensor (with the harness unplugged).
With the engine turned on with the harness unplugged, I get 5 volts from the red wire to ground, and 5 volts from the red wire and the green wire in the harness.
This all indicates that I have a good sensor and wiring.

I e-mailed Zdyne and receive a reply:
I made a couple of jumper wires so I could use them to connect the harness and temperature sensor. Then I tapped into the jumper wire to take a voltage reading.
I got 0.679 volts with the engine warmed up and running. No ECU codes either.

I reconnected everything and reset the ECU. I took another test drive and it still doesn't want to rev past 6800 rpms.

Any suggestions?

 

This ECU is not user programmable. I only went for the 1 wire conversion because of budget constraints. So these were settings that were set from Zdyne.

 

The ECT sensor hardly ever throws a code, even if it is completely dead. It is a variable resistor, which usually goes and the user won't know.
Usual symptoms;
Car won't start when warm
Bad Gas mileage
I've emailed you something on ECT sensors that I think can help.



[Modified by Centripetal, 1:18 PM 7/26/2002]

 

send it back and get ur money back or a new one
after getting ur money, buy another one....
this shoudlnt be happening... if ur car and sensors are on specs... its like a faulty ecu to me....
not because they make good products and they are good ecu's doesnt mean that ALL ecu's are 100% good and that there cant be change of one of them being messed up....


[Modified by JDM EF9, 9:59 AM 7/26/2002]

 

Hey, thanks for the doc! I'll try shortig out the harness with a 330 ohm resister and then check if it'll rev past 6800. I'll also check out the thermostat like you suggested. Hopefully its a simple fix and I won't have to send back the ECU.

BTW - Do you have a whole collection of those PDF files? Could I download them from somewhere? It was VERY imformative.

 

I called Zdyne and Bill agreed that the sensor should be good and the wiring is good and it MAY be the ECU. He was thinking that both the cold and hot rev limit may have been set to 6800 rpms. He is building another one and sending it out today. I'm doing a core exchange to minimize downtime. If it isn't the ECU, then I get charged $30 for the shipping, if it is the ECU then they'll pay for it.

Also, he was saying the the VTEC activation was throttle and temperature sensitive. So if the VTEC is activating, my temperature sensor must be sending a good signal. The hot rev limit is supposed to trip at 1.2V and I was reading 0.69V. So I really hoping that the hot rev setting was just programmed wrong. It'll make things much simpler.

 

I have over 70 MB of them. However, if I give them to you, I will have to give them to everyone. I could give you my IP and you could download them but it would take some cowardnation.


[Modified by Centripetal, 1:12 AM 7/27/2002]

 

How do you like that Zdyne?? I'm looking into getting one i just haven't seen anyone that actually has one. I'm doing an A6 block and Y8 head too. Whats the stock rev limit for a Y8 anyway? How high can I go? on stock valve springs?

 

The Zdyne was a good deal.. It makes hooking up VTEC a snap..

I just got another Zdyne ecu to test. And it still won't let me rev up to 7800. So something is up with my car. I even tested the voltage right at my ECU while the car was running. 0.67 volts at the ecu and 0.67 volts at the TW sensor. Zdyne is going to send me a reprogrammed chip with 7800 rpms as the cold and the hot rev limit. Hopefully this takes care of my weird problem.

The stock rev limit for a Y8 is 7200 rpms. Someone told me that they brought their Z6 to 7600 rpms with no problem. I' running stock springs, so I won't be venturing up to 7800 unless its by accident.

 

i have the Zdyne 1 wire ECU also..

im running an a6 block with a y8 head.. it revs to 7800 and then cuts out.. so it wont over rev actually.

some people might say the ECU is expensive but i think its worth it.. no mess no hassle. no figuring out fuel/air ratios. its all plug and play. even better, you dont have to cut into your harness

 

I'm torn between doing a p28 or the zdyne. I can buy diff prom's for the P28, making it more flexible....kinda. the Zdyne is easier, but I only get it burn once. If i did valvesprings later I'd want to up the rev limit and maybe change some other stuff. I could just get another prom burn with the P28. Would I be able to run diff injectors with the zdyne? I have both a z6 and y8 heads here, the Z6 is a complete motor. I'd use the Z6 TB and intake mani on either head. So won't I need OBD1 plugs for the mani anyway? Is the Y8 head worth the $175?? I could buy it and sell the Z6 head after I use the mani and TB. So many choices!!

 

HELP!
I popped in a new chip from Zdyne that was programmed for 7800 RPMS both cold and hot rev limits. I still can't rev past 6800 RPMS!

What could it be? Lack of fuel at 6800? Timing is off? Bad sensor(s)?
It can't be the ECU. I already replaced it with another one and even replaced the chip.

Could something physically be stopping the engine?
I'm stumped, and I think so is Bill from Zdyne..

 

Have you checked to see if your tach is off? Consequently, they are inaccurate. No codes?

 

No codes are being thrown. Also, I don't have anything to test the tach, nor do I know how. Please enlighten me.

 

do you have a messed up distributor? maybe the igniter is having trouble. just a thought.

 

Hmm. The cap and rotor are new, but the ignitor is still the old unit. You think the ignitor can be fine on the lower RPMS, but then at the higher RPMS it gives out?