SD to mass air, back to SD?
 

I found a good deal on a Pro-M optimizer and the conversion wiring harness over the summer, so I converted over to Mass air and didnt FEEL any loss in hp but I know there could be a little. I wasn't having any idle problems at all before (or after), just converted to have it for the future when I have a serious cam in there.

I have the wires from the MAF spliced into the computer wiring harness, as well as 2 others that go to the VSS (it died upon stops before i did that).
Would those wires cause any problems being spliced into the harness still if I put the SD processor back in there? If so, then I'll just leave it as is because I dont wanna pull all the wires back out. I was gonna try it at the track with SD and the MASS air computer's (and intake tubing) to see if theres much of a difference to worry about.

Then again, although I've heard it works well with SD, I'll be putting in a B cam in the next few weeks and I dont want it to idle bad.

Oh well, what do you guys think I should do...?

Just leave it, its not worth the trouble for the small amount of HP
or
Switch back because speed density rules!

thanks guys

Although speed density RULES I would just leave it alone after I went through all that trouble.

When I first got my car I wanted to convert but since I joined this site.....and seen all the people running 12's with speed density I decided to keep it.

My car is in pieces right now and I cant wait to see what I will run....No tellin what I will run on slicks.

well, it would be really easy to switch back if i didnt have to take out the wires that i spliced for it (and the 2 i added). Then I'd just swap the computer and inlet tube and be done.

I'm basically asking if it will cause any problems having the extra wires hooked into the speed density computer. I wouldn't think it would, because they will be disconnected from the mass air meter.

I'm not sure about your setup but I have switched and speed density computer into a factory mass air equipped 89 Mustang and didn't have any problems, no check engine light, nothing! I don't think you will have any problems and if you do it should only be with the two wires going to your VSS, may have to disconnect them or at least put a switch or something on them so you can break the circuit. The worst you could do would be fry the speed density computer, but I doubt it would. Good luck.

If you run a B cam with Speed Density without a custom chip, your car will run like crap.

not with the right timing and fuel pressure. after all, thats what the custom chip would do.

There's plenty of people that have had success with the motorsport cam's with speed density, its all in the tune.

another reason i want to do this is just to dispell or confirm the rumors about bad idle or power loss between the 2.

I'm pretty sure I'll be able to get it to run good with the B cam, but if not, then back in goes the mass air computer

Please, a custom chip does a hell of alot more than regulate timing, and it cannot regulate fuel pressure as you stated, thats the regulators job, a camshaft replacement changes volumetric efficiency in SD to the point, it's set look-up tables cannot adjust properly like Mass Air, thats why they produced it.

YOU CANNOT RUN A B CAM ON A SPEED DENSITY STOCK MOTOR, PERIOD, IT WILL IDLE LIKE TOTALL DOG POOH!!!!!!!!!!

it has been proven time and time again that MAF is best, or a 2002 Cobra would be SD!

go to the Corral if your just gonna sit there and try to make me look dumb.

I DO know that mass air is better with cams, but I also know that speed density CAN run well with them too. It's just harder to get there.

i posted this topic to see if i'll be ok by just swapping the SD computer back in so i can see any differences. I didn't post it for people to come in and basically call me an idiot

i'll install the cam in about 2 weeks and then i'll try SD, if i can't get it to work right, then i'll put the mass air computer back in. thats all

DUDE CHILL! I am not trying to make you look bad at all, it's just that you stated that a custum chip does basically what a stock ECM does and THAT IS WRONG, maybe i was to short with you, i am sorry, but so many people state that they slap in a B cam on a stock density motor and it idles fine.............thats just not possible.........i need proof from these people other than saying it works.

Once again sorry, I guess im fed up with this myth that you can slap in a cam in a density setup and it will work fine. NOT!

it's cool man, i'm sorry for getting all jumpy too.

but i never said anything about just slapping it in there and it running fine. I know it will take some tuning, and it still may not be right. I'm gonna try it and see what happens, it may run like crap no matter what, and in that case I will put the mass air computer back in. But I'm gonna give SD a try and see what happens, I'll let you (and everyone else) know what happens.


sorry again, we all gotta be brotha's on this board:cool:

look at 88WORKCAR..he has SD,b-303,heads, intake,430's and he runs very very fast..a b-303 is more capatable with SD than the e-303 is though..i can tell you that from experiance..SD doesn not like higher lift without the more duration..the b-303 has less lift than the e-303, but has more duration

do not come on here and basically tell the kid its impossable

It's not the change in vaccum that make the speed density idle bad. It's because it can't add extra fuel. If you add 30% more air on a mass-air car, it will increase the duty cycle( pulse ) of the injectors but not speed density, it have fix tables in the computer. So if you add 30% more air on SD you will need to add 30% more fuel. How? With a fuel pressure regulator or with custom chip wich increase the duty cycle of the injectors. I do not have a cam on my car but if i lower the fuel pressure it will run like crap.

There is no way in the world you can change fuel pressure by 30% with a regulator.

Yan, i agree with 95% what you said. BUT the SD reaches its limits on the fuel table very quickly as with MAF, its limits is much higher, with this situation. yes a reegulator will help, but if you want to get the most out of your B cam with SD, use a fuel regulator, better fuel pump, and a custom chip! as for the idle, it will idle crappy, but if you go the way i said, that should take care most of the idle problems. if you still have idle problems, use the idle plate that you can get out of mags and even FORD! im not sure what is the correct term for this part, but i hope you know what i mean. keep us posted! it CAN BE DONE! good luck.

88workcar swapped to an E303 cam and did better than he did with the B303. The ONLY problems he ever spoke of the with SD computer and the B303 cam was a rich idle. Course, the B303 cam will be richer than the stocker. It took him about 5 minutes to get his E cam tuned right.

You can set fuel pressure to 60psi on most adjustable fuel pressure regulators. Stock is 39psi, that's a 54% increase of fuel pressure. That will also support nearly 350hp on the stock injectors, simulating the stock injector cycle, which is an increase of power on the stock injection cycle of nearly 50%.

The Speed Density computer is FAR FAR better at compensating with internal tables than a Mass Airflow Computer could ever hope to be. When's the last time you've seen a MAF car swap to 24lb/hr injectors and run perfect without a MAF sensor recalibration? I've seen SD handle it with not a hiccup. There's a reason for that, by the way. It's because SD cannot measure air flow. Since a MAF car can, it doesn't need such aggressive tables.

So Unit, back to the original question, do you think i should try the SD computer and see how it goes? or should I just leave the mass air processor in there and not worry about it, because I KNOW it will work fine like that?

The worst you're going to do is fry the $20 Speed Density computer. I would run it with the SD processor, see if you can tune it with fuel pressure. If you can't, you can always use the MAF processor. Just make sure the MAF sensor is NOT hooked up when you have the SD computer in there. I would hate to see something short and fry that sensor. As long as their is no ground on the extra wiring, there should be no current that flows through it.