Speed at WOT ?

[WVZR-1]

Originally Posted by DarkAngel

Thank you everyone for all your quick answers

for tach limiter, i have a chip so i don't know if i still have the rev limit at 7100
furthermore, i don't really want to hit the rev limit :-S

A scanner if you have one from the ALDL and I'd be interested if you decided to do the C68 display for a possible validation. Do you have a FSM for the car? I could probably email you the procedure from the FSM if you don't.

In the FSM it should be found 1C1-1 through 1C1-5 for the '90 and for other years on similarly numbered pages I'd think.

[Paul Workman]

Originally Posted by XfireZ51

The ALDL datastream has a tach ceiling of 6300rpm which is the limit of the L98
datastream. Granted the rpms change rapidly at that point, but if you want to check tach error v the datastream, do it at a point below 6300rpm. There is raw data for rpms which can be output with a change in the ALDL datastream, but you will need to convert that to rpm.

No, not that complicated. The (static rpm) % error can be corrected at a reasonably lower rpm - I used 3000 - and one can get the % error down to eyeball accuracy i.e., close enough -so that it will track across the rpm range.

The bigger tach error is due to mechanical lagging as a function of rapidly increasing rpm - especially in low gear at WOT. (So, a lot could be said for the original C4 digital tach displays, far as mechanical lag (the lack thereof) goes.) So, obviously the shift light is a far more accurate (and maybe safer) way to avoid analog errors when rowing the gears.

P.

[DarkAngel]

Originally Posted by WVZR-1

A scanner if you have one from the ALDL and I'd be interested if you decided to do the C68 display for a possible validation. Do you have a FSM for the car? I could probably email you the procedure from the FSM if you don't.

In the FSM it should be found 1C1-1 through 1C1-5 for the '90 and for other years on similarly numbered pages I'd think.

i have check in the Corvette manual that i have but i didn't found the section you are refering to
if you can send it to me, it would be really nice

does 4.10 gear ration came stock out of the factory in '90 ?

[We Gone]

1990 - 1996: HVAC Diagnostic Codes

On 1990 to 1996 Corvettes equipped with RPO C68 (electronic climate control), it is possible to read the HVAC system diagnostic codes from the climate control panel on the dashboard.


1. To enter the diagnostic mode, press the fan up and down arrow buttons at the same time until -00 appears on the digital readout.

2. One you have entered the diagnostic mode, you can scroll through the various parameters by using the up and down fan buttons.

3. To view the value for a particular parameter, press the "AUTO" fan button.


Note: If you see a "-" next to a parameter value (example: "-105"), you must add "100" to that value to obtain the correct value for that parameter. Therefore, the correct reading would be 205 for this example.
Parameter Description Values
0 System Faults
(one of these will be set if your air conditioning controls have an LED flashing) 00=No Faults
01= Temp Door Motor Circuit Fault
02= Temp Door Motor Circuit Fault
03 = Ambient Sensor Open
04 = Ambient Sensor Short
05 = In-Vehicle Temp Sensor Open
06 = In-Vehicle Temp Sensor Short
07 = Solar Load Sensor Open
08 = Solar Load Sensor Short
09 = Low Freon Detected
10 = UART Failure
1 Temp Setting 60F to 90F
2 In-Car Temp Sensor 10 = HOT -130 = 230 = COLD
3 Outside Temp Sensor 10 = HOT -130 = 230 = COLD
4 Sun Load Sensor Max light Max Dark
L98 38 183
LT5 115 -110 = 210
5 Ignition System Voltage 0 = 9 Volts -155 = 255 = 16 V
6 Engine Speed (RPM divided by 25)
7 Vehicle Speed
9 A/C System Mode 00 = OFF
01 = Re-Circulation
02 = A/C
03 = Bi-Level
04 = Heater
06 = Defrost
07 = Vent
10 = Manual Re-Circulation
10 Blower PWM 0 = 0 Volts 128 = 14 Volts
11 Program Number 00 = COLD -155 = 255 = HOT
12 Mix Number -155 = 255 = COLD 00 = COLD
16 Coolant Temperature In degrees C
17 Solar Correction 114 = Max light 128 = max dark
30 Stored Full Hot Value 0 to 50
31 Temp Door Travel Range 100 to 200
34 Temp Door Position Requested 00=Full HOT -153=253=Full COLD
35 Compressor On Time 0.1 second increments
36 Number Of Times Below Critical Time
37 Software Version Number

[WVZR-1]

Originally Posted by DarkAngel

does 4.10 gear ration came stock out of the factory in '90 ?

The 4.10 ratio doesn't come from the factory for any year C4 Corvette

It looks like "We Gone" has you covered on the C68 diagnostic and information procedure. If you've other questions you can see the answers are generally just minutes away. The tach error when you confirm that is what it is won't be a difficult repair for you either. There are multiple DIY threads available for that.

[DarkAngel]

Originally Posted by WVZR-1

The 4.10 ratio doesn't come from the factory for any year C4 Corvette

It looks like "We Gone" has you covered on the C68 diagnostic and information procedure. If you've other questions you can see the answers are generally just minutes away. The tach error when you confirm that is what it is won't be a difficult repair for you either. There are multiple DIY threads available for that.

yes reponse are really quick
thanks again everyone for your reactivity

[XfireZ51]

Originally Posted by Paul Workman

No, not that complicated. The (static rpm) % error can be corrected at a reasonably lower rpm - I used 3000 - and one can get the % error down to eyeball accuracy i.e., close enough -so that it will track across the rpm range.

The bigger tach error is due to mechanical lagging as a function of rapidly increasing rpm - especially in low gear at WOT. (So, a lot could be said for the original C4 digital tach displays, far as mechanical lag (the lack thereof) goes.) So, obviously the shift light is a far more accurate (and maybe safer) way to avoid analog errors when rowing the gears.

P.

I may be guilty of providing too much information. Since a scan tool had been suggested, I simply wanted to make people aware of the fact that the ALDL data will only display RPM up to a value of 6300. So if you were trying to compare the ALDL to what you were seeing on the tach and using, say 6500rpm, it won't be shown on the scantool. I think I even said, use an RPM lower than that to come up w an error factor. I have my WB and shiftlight connected to the diagnostic plug near the firewall. That will show actual rpm when using a shift light or the WB logging software.

[DarkAngel]

ive made a quick test this we
at 2000rpm on the tach, correspond 66 on the A/C : 1650rpm
at 3000rpm, 108 : 2700 rpm
at 4000rpm, 140 : 3500 rpm

this is approx because i've made the test alone and it was hard to look at the tach, look at the A/C, maintain the rpm and look at the road

i will make other test another time and keep you informed

[WVZR-1]

I'd say you've confirmed the tachometer error and unlike a speedometer error it's not going to be at a "fixed percentage". Did you happen to make an observation "at idle"? Maybe now that an error is suspect it would be motivation to find a scanner and do it again using the ALDL as a source.

How responsive did the A/C display appear to be to your application of throttle? Considerable lag or maybe rather responsive. I've never actually used it.

[DarkAngel]

at idle it was between 28 & 32 : 700/800 rpm
the A/C display is not immediately responsive but not that much laggy also