I'm very tempted to set up highway cruise mode on my car. The problem is I have an aftermarket speedometer and no VSS input to the ecm. I also run a TH350 so what I've been thinking of doing is setting the minimum activation RPM to 2025 (right at where I cruise 50mph) and putting in a 30 second delay before it activates. Has anyone ever tried anything like this, or am I on my own here?

 

With the number of items that depend upon the VSS, it is usually best to have it operational. As for what you are thinking to activate the lean cruise mode, it should work. Also use a MAP threshold so if you are into the throttle it won't stay or go into lean cruise mode. And a CTS threshold to be sure that the engine is up to temperature.

RBob.

 

I would run a VSS but I have a TH350 and no real way to hook a VSS up with my VDO gauges (they have a box that attaches to the Th350's output but the output signal of the box is way higher than what the ECM would expect, I believe it's even higher than the newer relucator type VSS). I've modified pretty much everything in the prom that's VSS related to 0mph, including the knock sensor, IAC, etc. etc. I've got the temp threshold for highway mode activation set to 160 degrees, and the max LV8 for highway fueling is set to 128. I think this should be about where I need to be. The reason I'm attempting this is because the car used to knock down really good mpg's before I changed the AIR divert setting in the prom, I think that was causing the car to run lean but it was also causing some crazy idle issues once up to temp. Hopefully this will help me regain some of that lost mileage.
PS. I know it's kind of crazy to talk about mileage in a stalled TH350 car but hey every bit counts

 

FWIW, the TH 350 and the T5 share the same sending unit, so you could prolly swap in a later model T5 vss if you really needed it to work

good luck with it

-jason

 

Painless also sells magnetic VSS devices that screw onto the speedo cable output that will still allow a speed cable, or by the sounds of it the VDO VSS device to then screw onto it.

 

From the VDO website:
SPEEDOMETER GAUGE QUESTIONS:
Will VDO Speedo work with my Electrical controlled Transmission?
Answer: Yes, VDO Speedo’s will work with electrical transmissions which include OE VSS (Vehicle Speed Sensors).

Which Hall Effect Speed Sender should I use?
Answer:
GM: TH350, TH400, Early 700R4 use VDO part # 340-011


Since it says early 700R4 then it sounds like a 2000 PPM setup which is what the 730 ECM uses for the optical VSS input at pin C6. Have you tried it?
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You can get good MPG with a TH350. The cam and gear choice makes the most affect. 3.08 gears work nice.

EDIT: Sure you have the right plastic gears in the TH350 for the correct PPM of the reluctor? Or do you have the wrong gears in the TH350 and programmed the speedo to work with the VSS PPM being incorrect? If so, put the right grears in it to match what the ECM wants to see.

 

This is another solution, if what junkctlr has suggested doesn't work out for you:

http://www.dakotadigital.com/index.c...rod/prd126.htm

 

There is a way to switch the 165 ecm's to read the 2000ppm signal correct? BTW I'm not running speed density, I'm using the APYP bin on the $6e program. The output on the VDO sending unit i have is a "standard closed hall effect 16 ppm signal" so I was off on the pulse number being high (it's been a few years since I put these in). I'm pretty sure I need a 4 ppm signal on the standard MAF style ecm's correct?

 

The 165 ECM expects a 2000 pulse per mile (PPM) signal open-collector type signal (like hall effect).
The sensor sounds like a 16 pulse per revolution (PPR) signal open-collector.
Your gears in the TH350 will determine the PPM of that sensor.

 

best bet is to use the 2 pulse per rev inline vss sensor from painless. should't have to touch any code to use that style vss, as it should be exactly like the optical pickup in the speedo head of a factory cable drive car.

if you had a digital speedo in the car (trans am possibly), they you'd need the 4 pulse per rev one. edit: wrong...I'm thinking '730. 165 used 2ppr.

165 should be able to use either with a bit setting. this is also i think a different pin on the ecm.....edit: wrong again...ignore the dummy behind the keyboard....

 

what about just hooking the vss up and seeing what it reads? it doesn't have to read right, as long as you get something that doesn't peg it out or say less than 10mph at 100. couldn't you just set everything to work at whatever mph it happens to show.

 

I kind of already did that by setting it all to 0 I really don't see any major use for the VSS aside from the settings that it controls, The engine doesn't calculate LV8 with it, and the DFCO stuff still works fine. I've never seen a real benefit of having the VSS but I'm not that deep into prom tuning, it's more of a weekend hobby to me. One option I had thought of was getting a TH350 tailshaft with the larger speedometer hole and running the 700r4 type speedo output to the speedometer then slaving this to the ECM but I quickly ran into issues with the buffer box etc. etc. When it was all said and done it seemed to me like the most economical thing to do was to modify the prom to not calculate the VSS in it's equations. There's also the issue with my shifter position being N when it's in 3rd gear (th350 swap with stock shifter) I could've taken that all apart and moved the wires around but instead I just changed the idle settings to not compensate for P/N over D.