TBI and DIS on 2.8L Questions

Printable View

02-12-2015
7Ronin

TBI and DIS on 2.8L Questions

Hello,

I have a 2.8L from an S10 backed by the stock T5 installed in a 1967 Volvo 122s. I would like to keep the stock TBI tune- I don't know about others experiences but I have found the stock 2.8L TBI to be ultra reliable so I don't want to deviate from the stock tune or add any other features EXCEPT I would like to add DIS for the clean look and some extra space a the back of the motor where the distributor is.

I'm not hung up on keeping the stock ECM (1228062 ASDU) and I know I'll need a 7X crank trigger but is there an ECM that can run the stock tune and DIS?

I greatly appreciate any help or ideas!

Thanks,

Nathan
02-12-2015
1project2many

Hi, Nathan.

If you can get the hardware set up, the solution might be as simple as changing three or four constants in the calibration. The signals from DIS and distributor ignition module are very similar. The major difference is when they are sent in relation to crank position.
02-13-2015
7Ronin

Quote:

Originally Posted by 1project2many

Hi, Nathan.

If you can get the hardware set up, the solution might be as simple as changing three or four constants in the calibration. The signals from DIS and distributor ignition module are very similar. The major difference is when they are sent in relation to crank position.

I don't think the stock ECM will work with the 7x crank sensor required for DIS. The 7X sensor has the function of letting the ECM know where the number one cylinder is- the stock ecm does not care where the number one cylinder is because the distributor handles this function.

Thanks!

Nathan
02-13-2015
Six_Shooter

Quote:

Originally Posted by 7Ronin

I don't think the stock ECM will work with the 7x crank sensor required for DIS. The 7X sensor has the function of letting the ECM know where the number one cylinder is- the stock ecm does not care where the number one cylinder is because the distributor handles this function.

Thanks!

Nathan

That's not (entirely) correct.

Take a look at the DIS system, mechanicals and electrical connections between the crank sensor and ICM, and the ICM to ECM and you will see what 1project2many is talking about.

He (1project2many) as well as I have used DIS on ECMs and codes that were never intended to have DIS associated with them.

You are correct in saying that the ECM doesn't care where #1 is, but even with ECMs that use the early DIS (non direct PCM triggered), they still don't care where #1 is.

I'll give you a nudge in the right direction... the ICM cares where #1 is.

And go... ;)
02-13-2015
7Ronin

Quote:

Originally Posted by Six_Shooter

That's not (entirely) correct.

Take a look at the DIS system, mechanicals and electrical connections between the crank sensor and ICM, and the ICM to ECM and you will see what 1project2many is talking about.

He (1project2many) as well as I have used DIS on ECMs and codes that were never intended to have DIS associated with them.

You are correct in saying that the ECM doesn't care where #1 is, but even with ECMs that use the early DIS (non direct PCM triggered), they still don't care where #1 is.

I'll give you a nudge in the right direction... the ICM cares where #1 is.

And go... ;)

Ahh, OK got it. I need to pull up a wiring diagram for a V6 car with DIS but what am inferring is that the DIS ICM uses the crankshaft trigger signal for syncing number 1 and it then needs the the ECM is advance/retard signal.

I did read that for some corvair DIS installs had to have a certain delay parameter changed due to the differences between the distributor pick-up coil and the and the 7x crank trigger.

Thanks,

Nathan
02-14-2015
1project2many

The wiring diagram will show the same circuits between the DIS module and ecm as between a distributor and ecm.
02-14-2015
billygraves

42 87 91
02-14-2015
1project2many

DIS (The 7X system) was first used on a production model with the redesigned 2.0 in the '87 J car. In the 7X system the ecm reference pulse is 60 degrees advanced of TDC.

I would not expect any need to use the pfi / MAF code. There is no functional difference in the timing control strategy. I have used turbo Sunbird code on a 93 Cavalier 2.2 with DIS and Six_Shooter has used distributor code on the sixty degree engines that evolved from the TBI 2.8.

In addition to the initial spark advance value mentioned by billygraves, the maximum and minimum advance limits will need to be adjusted to match a DIS calibration. These values are relative to the initial spark and leaving them set at distributor limits will effectively disable spark advance. It may also be helpful to change the spark latency value in code to match DIS. Additionally, we've found that some calibrations use values such as the "spark advance with power steering active" found in the turbo Sunbird code which are not subject to the min/max timing limits and need to be adjusted manually. If your vehicle uses a power steering pressure sensor connected to the ecm, spark values used when this sensor is active need to be adjusted in the ecm.

The challenge is going to be setting up the sensor and trigger wheel.
02-14-2015
1project2many

Quote:

Originally Posted by billygraves

42 87 91

Secret code?

BTW, John Spears of Speartech posted pictures of an LT1 / Northstar DIS marine engine years ago to get everyone excited. It took a few years to isolate an OEM marine application and get part numbers and pricing By that point the parts were all discontinued. But at least we now know what to put into the ecm to make the system work with a distributor based calibration.