carbs v. tbi - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
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post #1 of 4 Old 09-23-2014, 01:11 PM Thread Starter
Junior Trooper
Join Date: Sep 2014
Location: Memphis
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carbs v. tbi

After years of carb bikes I have now made the leap to TBI with the 07 Vee (and an 05 SV).

I've put the Vee back to stock mufflers and the PO said the Staintunes did not require a remap, so there's nothing to remap to go back to stock (I guess).

With carbs I'm used to re-jetting for intake and exhaust mods, but please school me on TBI. Specifically, does the ECM automatically adjust the mixture for such mods? And when does TBI require a remap (versus just doing it for better performance).

Old dog trying to learn new tricks
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post #2 of 4 Old 09-23-2014, 01:31 PM
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Well, you probably picked two of the more difficult "EFI" bikes to deal with. Like everything, time has improved fuel injection systems in bikes and the 1000 v twin Suzuki's do NOT have the latest technology.

First they tend to be tuned on the lean side in the lower rpms and part throttle settings. This is all about emmissions. Common to have some lean surging, even backfiring and hesitation especially in low speed/load riding. The higher rpms and throttle settings are actually quite rich, which is common in OEM tuning to protect the engines.

Other than some inputs from air temp sensors, manifold pressure sensors, there is not much the system does to "tune" on the fly. It does not have the ability to read air/fuel mixtures and adjust.

Many owners end up going to a tuner, Yosh box or Power Commander. While there is some improvement with these, my opinion is that they really need to be dyno tuned to the bike to work right. If you do a precision tune up to the bike, in stock configuration, they can be made to run pretty smooth and strong.

I would still rather fool with the EFI than Carbs. I am from the "good ole days" and remember all about carbs. EFI is actually much easier to diagnose and fix IMO. Don't mention the improved starting, driveability, and fuel mileage. But, like everything, some tuning can't hurt! Good luck with your new Vee!

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post #3 of 4 Old 09-23-2014, 09:30 PM
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The EFI is "open loop", that is, it has no way of sensing whether the mixture is too rich, too lean, or just right. It follows the map, based on the sensors, and that's it. The various add-on boxes allow the user to vary the map, but to do it right you'd probably want to book some dyno time to be able to set the map correctly using an external fuel-air ratio monitor. Oh, and the ECM also controls the secondary throttle plates (assuming yours are still installed) as well as timing retard based on gear selected.
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post #4 of 4 Old 09-24-2014, 12:31 AM
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Your Vee will be too lean at low throttle up to about 3500 or so RPM unless the ECU has been flashed or you use a PC. The company now makes a PCFC which is cheaper and works great on my 06 Vee. Oh, and the Vee is lean with stock pipes on the low end. Made worse by free flowing pipes. Top end is often just fine either way. You can always just get a flash from a Yosh box at your dealer or a professional tuner to solve the low end problem. The PCFC will accept up to 10 programs and you can choose which one with the turn of a dial.
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