obd1 to obd2 conversion

[robertisaar]

while thats true, it only really helps with emissions. you could dyno the same car twice, with the same tune, the only difference being running in a SFI mode, the other being MPFI, and the amount of power/torque will be exactly the same within the tolerance of how accurate the dyno is. it obviously doesn't help idle quality, i can vouch for that.

[OldSkoolGP]

while thats true, it only really helps with emissions

A more efficient burn only helps with emissions? Horsepower is a measure of an engine's efficiency. If you can get more out of an engine putting the same amount of fuel and oxygen into it, that is the definitoin of more efficient. If it is reducing emissions, it is because the combustion is more complete. How is that a bad thing?

you could dyno the same car twice, with the same tune, the only difference being running in a SFI mode, the other being MPFI, and the amount of power/torque will be exactly the same within the tolerance of how accurate the dyno is.

Uh, did that. 8 more WHP on a stock OBD-II tune and no other mods, vs. OBD-I with some tuning. You want to put that down to dyno inaccuracy? Tuned it a little more on the dyno, got another 2WHP out of it, no other changes.

it obviously doesn't help idle quality, i can vouch for that.

Try owning a DOHC and getting a smooth idle out of it. Mine idles smoother with OBD-II, and I can vouch for that.

[robertisaar]

i'm used to OHV motors... can't argue about what i don't know about...

and i really don't trust dynos down to those kind of numbers... not to mention, doesn't OBD2 SFI revert to MPFI above a certain RPM(like 3000-3500)? i know all of the obd1 and 1.5 systems do...

[IsaacHayes]

yeah I thought it reverted to MPFI above a certain RPM too. It would make sense that the valves opening so fast that the higher the RPM the less it would matter.

Someone should dyno their car then disconnect the cam sensor so it goes to batch fire mode and see what happens. Hmm I might try that on my car just for the hell of it and see if I can't get the MPFI rumble at idle they have... LOL

But for idle quality and part throttle cruising at low RPMs power I have to agree SFI will win there.

[robertisaar]

i wonder if disconnecting the cam sensor does anything other than reverting to MPFI? possibly the PCM adds more fuel, takes out timing to "compensate"?

but i have no problems with idle quality, then again, i don't have 4 valves per cylinder, so i wouldn't be penalized so much at low RPMs for airflow/turbulence

[OldSkoolGP]

AFAIK, OBD-II stays in SFI mode throughout the rev band. I can't think of any other exsplanation where with OBD-I my car had a blip of reduced power between 5-6K, and with OBD-II I now have a surge of power between 5-6K. 5-7K is now the strongest part of my rev band where before my power was almost gone over 6K.

[asylummotorsports]

All SFI systems revert to MPFI after about 2500 RPM, or so I have been lead to understand by folks alot smarter than me.

The computer simply can't keep up with individual cylinders after that, so it's really not an issue.

As far as which system is best that may be a personal preference, but OBD-1 is probably the easiest and least expensive to tune.

[robertisaar]

All SFI systems revert to MPFI after about 2500 RPM, or so I have been lead to understand by folks alot smarter than me.

The computer simply can't keep up with individual cylinders after that, so it's really not an issue.

As far as which system is best that may be a personal preference, but OBD-1 is probably the easiest and least expensive to tune.

sounds like what i've been told... i have to wonder how we could test it? and at raising speeds, the exact opening time for the injector becomes less and less important...

[IsaacHayes]

Or is it we are getting confused with the 24x crank sensor? That it's not read above 2500 RPM? Or is it both?