Shop really struggling with v8 swap gauge connections

Long story but working 100 hour weeks in addition to starting my own business on the side, so time to do project on my own went to the wayside, so the v8 swap went into the shop and I told them I wasn't in much or a hurry. 1997 v90 has a 6.0 LY6, 4l60e trans installed and (mostly) running absent of some tuning issues I'm waiting until the end to work out.

Short story: Speedo has worked fine from the get-go, but shop is really on the struggle-bus getting water temp and tach gauges wired and working. They apparently have the correct sending unit to tap into the v8's head that should be able to control the water temp gauge. I have also given them a Dakota Digital converter box that I've confirmed is able to control the tach needed with the internal calibration signal the box sends. These should be straight forward to get wired up at this point right?

After weeks and weeks of no progress, I'm told today by the owner that they think the dash needs the original volvo computer to process the signals going to the dash. The original computer (ECU) was obviously removed and replaced with the GM version. They are requesting that I bring the volvo ECU back in for them to test to try and get signal to the gauges. I really don't feel this is accurate as the dash only needs some voltage to control the gauge needles and all that is needed is finding the correct resistance/voltage for all to work. Right?

Does anyone have any experience with this so I can redirect them?

The temp gauge I had an issue with my 240, so i bought a VDO sensor and a VDO water temp 52mm gauge that matched. OR you can also get a thread adapter to the volvo temp sensor to the GM threads to the head. I'm not sure how the 97 v90 engine harness if it's a single wire or not. Its very simple fix

This is how to set-up the tach signal
http://lt1swap.com/lsx_tach.htm

EDIT: make sure they set up the hp tuners to run the tach signal at 6 cylinders.

The voltage stabilizer is probably in the cluster.

Mine is a 240 application -- 6.2L running on a stock 08 Corvette ECU. For oil pressure, oil temp, water temp - I just fitted the original VDO/Volvo senders (1 in rad, 1 in oil passage in block, 1 in oil cooler fitting) and those gauges don't know/care what engine/ecu is in the car.

I set the tach wiring up as referenced above by 77Volvo - used the stock tach output from the ecu, unmodified my hptuners. My car has a V6 tach - so I accessed the actual engine rpm through the diagnostic port/phone app -- and jumpered up the tach so it would work out of the cluster. There is a little potentiometer on mine that allows for adjustment - I used that to fine tune the tach reading to what the phone was showing. Seems to be within a couple of hundred RPM across the board. No idea if that approach will work on the 97's tach.

Thanks everyone. Kinda confirms that the volvo ECU isn't necessary for this. I have the nice OBDII Ultra Scangauge that shows everything they are trying to hook up, but we all agreed that having the dash gauges work was still important in case the OBDII gauge ever is taken out. I'm mostly concerned about the tach in the gauge since it is more precise than a digital gauge with low-frequency updates. The wiring harness outputs the tach signal and I'm hard pressed to believe it's as difficult as they are making it, but they are doing this as a favor to me and it's outside their usual business model.

It's a good idea to try and get a thread adapter to retrofit the volvo sender to the gm head. I'll mention that.

If anyone else has ideas I'll keep an eye on the thread.

IIRC - the ECU outputs a 5V 4 cylinder signal for a contemporary tach application. The Volvo tach wants a 12V based signal and I think the 1000 ohm resistor makes that adjustment. As I understand it, any fine tuning can be done through HPTuners to get the tach to read fairly accurately.

What do you do 100 hours a week?

M.H. Yount said:

IIRC - the ECU outputs a 5V 4 cylinder signal for a contemporary tach application. The Volvo tach wants a 12V based signal and I think the 1000 ohm resistor makes that adjustment. As I understand it, any fine tuning can be done through HPTuners to get the tach to read fairly accurately.

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This helps, I can get a voltmeter us and see what's coming through the GM ECU wire and that should confirm if the resistor is necessary.

apachechef said:

What do you do 100 hours a week?

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I work at the state climate center and Utah State University. With turnover and budget cuts, my climate center job is doing work that used to be done by two full time employees.
My week juggles doing research aimed at peer-review journal publications, operational meteorology/climatology for Utah Public Radio and occasionally TV needs, develop and maintain automated forecast products hosted on our website, education outreach ranging from pre-school visits to retirement community presentations, extension outreach to state agencies and decision makers + any media requests for weather/climate related interviews, daily manual weather observations at a pair of weather station + data archiving, public/stakeholder data requests from our climate data portal, and my favorite...forensic/consulting meteorology for civil and criminal court cases. I'm also the state coordinator for a volunteer-based network (CoCoRaHS) of a few hundred citizen scientists measuring and reporting precipitation across the state, so doing recruiting and outreach for that. I also teach three classes at the University (two each semester)--two of which I was asked to rebuild from the ground up last year including developing the first online component for one. 160 undergrad and grad students this semester (thank god for my TA's).

On top of all that I'm ramping up my small business making craft hot sauce. Started a few years back when I could never find anything hot enough at the store and started making my own at home for personal use. Friends started buying and word of mouth spread like fire (pun intended)...kinda weird I know, but the demand is growing fast enough to warrant testing the waters to see where it goes. Plus, the flavors are way better than store-bought brands-hence the rapidly growing demand. Currently have four flavors for sale and gearing up for commercial scale come 2018. I'm looking forward to my first-born arriving in January so I can finally get some sleep.

Temp gauge in Motronic 4.4 cars is controlled by ECU. Using a -95(Motronic 1.8) or older gauge fixes this, it uses same range as any RWD with a redblock or older whiteblock.

Lankku said:

Temp gauge in Motronic 4.4 cars is controlled by ECU. Using a -95(Motronic 1.8) or older gauge fixes this, it uses same range as any RWD with a redblock or older whiteblock.

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Well that changes things. I don't think we have enough room for both ECU's in the kick panel. Might be forced to get an aftermarket gauge to supplement the OBDII scangauge if the only option to get the OEM setup to work is through the OEM ECU. Unless the temp gauge can be individually separated from the cluster and replaced with the -95 gauge, but at that point you might as well get an aftermarket to fit in that space.

Thanks for this!

DrSlow said:

This helps, I can get a voltmeter us and see what's coming through the GM ECU wire and that should confirm if the resistor is necessary.

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FWIW - I don't think the 'mystery' is what the GM ECU is outputting; I think it's 'what does the Volvo tach want in that year/model?'

DrSlow said:

Unless the temp gauge can be individually separated from the cluster and replaced with the -95 gauge, but at that point you might as well get an aftermarket to fit in that space.

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All gauges can be changed individually. I'd go for OEM-look with older gauge. Fitting some other is extra work for a clean install because of the shape and size. Or make a separate installation on top the panel behind steering wheel.

You will have to add a pin to the x1 ecu plug.
Pin 48 is the one. Then You have to add a pull up circuit to the wire that goes to the tach. The ecu needs to be set to crank in the tach type settings. On my wifes 2007 Tahoe the high and low res are both set to 2. But on my 2004 ecu they are both set to 6. You will have to play with it and see what works. Here is a link for adding the pin.

https://ls1tech.com/forums/conversions-hybrids/1312048-ly6-6-liter-tach-wiring.html

the link that 77volvo245 posted is how to do the pull up circuit.

What shop is doing this work for you?

volvo? said:

You will have to add a pin to the x1 ecu plug.
Pin 48 is the one. Then You have to add a pull up circuit to the wire that goes to the tach. The ecu needs to be set to crank in the tach type settings. On my wifes 2007 Tahoe the high and low res are both set to 2. But on my 2004 ecu they are both set to 6. You will have to play with it and see what works. Here is a link for adding the pin.

https://ls1tech.com/forums/conversions-hybrids/1312048-ly6-6-liter-tach-wiring.html

the link that 77volvo245 posted is how to do the pull up circuit.

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Good advice and help. Since I have a stand-along harness that has a wire for tach signal, I wonder if the pin has already been added? Helps to know the pin for this so we can cross reference. The harness maker's instructions say to simply wire up to the tach converter and set the parameters a certain way, which from my long-term memory is what I tried awhile back with no success, so maybe the resistor is what is needed.

t8fanning said:

What shop is doing this work for you?

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It's a local indy shop. Autobahn Performance. Owner is wonderful and has been tremendously generous on the project. Not sure he wants to do any more after this though

DrSlow said:

It's a local indy shop. Autobahn Performance. Owner is wonderful and has been tremendously generous on the project. Not sure he wants to do any more after this though

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Interesting. I haven't heard of them before. If you need any help or something with it, I'm a bit south of Salt Lake.