Fabio421

I was looking at the SMT-6 piggyback tuning computer. Their website says that it can be used on "all" engines. Has anyone here tried using it on an L-Jet 928 (mines an 84 US) ? What were your impressions? How effective is it and how user friendly is the interface. How difficult are these to install and get tuned properly.

Thanks

Darien

Just got mine, I should get around to installing it next week. I got it to adjust my lower RPM ful pressures. Too bad the Shark Tuner isn't ready for 85-86 Sharks.

Rick Carter has had one installed for years and Louie Ott is a resident expert on the SMT-6

Abby Normal

Using one with the Turbosport set up.... Louie is the man to ask if it wil work on an 84.

Rick Carter

Louie is the expert. Darien, you'll be able to adjust timing as well.

Louie928

The SMT-6 could work on the L-jet by allowing you to change the voltage output of the air flow meter, or AFM, (trap door) to alter your mixture. However, from memory I believe the trap door is full open above about 75% power (air flow). After the trap door is full open, mixture is dependent on fuel pressure and corrected for air density by inlet air temperature. Air flow is dependent on RPM and the engine's VE. It's a fairly crude system at WOT. The SMT-6 could be used to intercept and alter the inlet air temp sensor output voltage value too.

I don't know what you want to achieve. If changing WOT mixture, then the SMT-6 won't have any effect if you try to intercept and change the AFM output. The trap door willbe full open. It should change the mixture if you intercept the temperature sensor. Sometimes those have an averaging function so immediate changes won't be seen. I don't know how the L-jet air inlet sensor works. You could use fuel pressure to get the top end (trap door full open) mixture, then using the SMT-6 to intercept the AFM signal and change that to get back to a good low end & mid range mixture would work.

The SMT-6 should be able to intercept the distributor trigger signal and change ignition timing.

I have not used a SMT-6 on an L-jet. Installation is going to involve finding switched +12v, the signal wire you want to intercept and change, and the trigger signal from the distributor. You'll need that to get RPM signal to the SMT-6 even if you don't want to change timing. The interface seems user friendly. It can be used for nearly anything involving changing a 0 to 10 volt signal, or frequency, related to a pulse rate (usually RPM) so there is a lot of configuration options. Mostly understanding the instructions and following them is the key.

The software is available for download from their web site. I've had some tell me it takes forever or longer to get registered so they can download the software. If you want to pm me, I can email you the software to check out.

Fabio421

Wow, thanks for the detailed response. I have plans for running boost (turbo) on my 84 and have always been bummed that the stock computer is unable to be tuned. When I ran across the info on the SMT-6 I thought it may be an inexpensive option. So it sounds like the key to using the SMT-6 to get proper fueling on an L-Jet with boost would be to increase the injector size to add fuel, then use the SMT-6 to take some away at lower RPM to retain driveability while not under boost. Great news. If anyone else has any details to add, please do so. This could become the "official SMT-6 thread".

John Speake

Don't go too large on injector size or else you won't be able to get a good ilde - the required injector opening time will be so close to the (erratic) injector opening time that you will have problems.

Don't go higher than 30#.

Louie928

There will be a limit to how much fuel you could pull out by altering the signal from the AFM. It's going to take some experimenting. I'd suggest doing the things normally done to manage fuel on FI engines and, like John said, don't go too big on the injectors. Use the rising rate pressure regulator, BEGI, or whatever it is for mixture under boost. Use the SMT to trim out stubborn areas which will usually be idle and part throttle. The SMT-6 can control ignition advance by using the 0-5v input from a MAP sensor so you could reduce advance with boost that way.

I don't have any SMT-6s on hand and didn't want to invest more money in buying another batch of them. John's ST works so well for the MY >87, and he'll have the '85/'86 available to take care of those too. I do know of one slightly used SMT-6 that is for sale if you want one.

Mark Stahl

I had been considering the SMT-6 but if John's ST is due for the 85-86 soon, I may very well hold off. Anyone have an idea on an ETA for the 85-86 SharkTuner? (Are we talking more like a year or more like 3 months?)

John Speake

......... more like 3 months for the LH SharkTuner 85-86.